Introduction to the technique of fiber optic networks. Vols: Main characteristics and scope of application Principles of fiber optic networks

Fiber optic call lines intended for transmitting information in the optical range. According to the Soviet Information Bureau, at the end of the 80s growth rates of the use of fiber-optic lines amounted to 40%. Experts of the Union assumed a complete refusal of some countries from copper core. The congress decided on the 12th five-year period of 25% increase in lines of communication. The thirteenth, also designed to develop fiber optics, caught the collapse of the USSR, the first cellular operators appeared. By the way, the forecast of experts regarding the growth of the need for qualified personnel failed ...

Operating principle

What are the reasons for the sharp increase in the popularity of high-frequency signals? Modern textbooks mention a decrease in the need for signal regeneration, cost, increasing channel capacity. Soviet engineers were evaluated, arguing otherwise: a copper cable, armor, a screen take 50% of world copper production, 25% - lead. The very well-known fact became the main reason for leaving the sponsors of Nikola Tesla, the project of Tower Vordcliffe (the name gave the name of the Metsnate sacrifted). The famous Serbian scientist wasveling to transmit information, energy with a wireless way, scareding a lot of local hosts of the copper smelters. 80 years later, the picture has changed dramatically: people realized the need to save non-ferrous metals.

The material of manufacturing fiber serves ... Glass. Conventional silicate, designed by a fair fraction of the modifying properties of polymers. Soviet textbooks, in addition to the indicated reasons for the popularity of the new technology, are called:

1. Small attenuation of signals, which caused the reason for reducing the need for regeneration.
2. Lack of sparking, therefore, fire safety, zero explosion hazard.
3. The impossibility of short circuit, a reduced need for maintenance.
4. Insensitivity to electromagnetic interference.
5. Low weight, relatively small dimensions.

Originally fiber-optic lines were to combine large highways: between cities, suburbs, PBX. Experts of the USSR called the cable revolution of akin to the emergence of solid-state electronics. The development of technology made it possible to build networks, dedicated leakage currents, cross-mounted interference. A stretch of a hundred km long is devoid of active signal regeneration methods. The bay of a single-mode cable is usually 12 km, multimode - 4 km. The last mile is more often covered with copper. Providers accustomed to integrate terminal areas to individual users. There are no high speeds, receptions of the cheapers, the ability to simultaneously power the device, simply using linear modes.

Transmitter

The typical beam shaper is semiconductor LEDs, including solid-state lasers. The width of the signal spectrum emitted by the typical P-N-transition is 30-60 nm. The efficiency of the first solid-state devices barely reached 1%. The basis of connected LEDs is often the structure of Indium-Gallium-arsenic phosphorus. Emitting a lower frequency (1.3 μm), devices provide a significant scattering of the spectrum. The resulting dispersion strongly limits the bitrate (10-100 Mbps). Therefore, LEDs are suitable for building local network resources (a distance of 2-3 km).

Frequency division with multiplexing is carried out by multi-frequency diodes. Today, imperfect semiconductor structures are actively displaced by vertical radiating lasers, significantly improving spectral characteristics. Running speed. Price of one order. Forced radiation technology brings much higher capacities (hundreds of MW). Coherent radiation provides the efficiency of 50% of single-mode lines. The effect of chromatic dispersion is reduced, allowing you to increase the bitrate.

Small time recombination charges makes it easy to modulate the radiation of high feed current frequencies. In addition to vertical use:

1. Feedback lasers.
2. Fabry-feather resonators.

High bit races of long-range communication lines are achieved by the use of external modulators: electro-absorption, Maha - Pillars interferometers. External systems eliminate the need to use linear frequency modulation with supply voltage. Cropped spectrum of the discrete signal is transmitted further. Other methods of carrier coding techniques have been further developed:

• Quadrature phase manipulation.
• Orthogonal multiplexing with frequency separation.
• Amplitude quadrature modulation.

The procedure is carried out digital signal processors. Old techniques were compensated only by a linear component. Bereger expressed a modulator with rows of wine, the DAC and the amplifier simulated with truncated, time-dependent volterra rows. Khana proposes to use the polynomial model of the transmitter in addition. Each time the coefficients of the ranks are found using the indirect study architecture. Dutcher recorded many common options. Phase cross-correlation and quadrature fields imitate the imperfection of synchronization systems. Similarly, nonlinear effects are compensated.

Receivers

The photodetector makes the reverse transformation light - electricity. The lion's share of solid receivers uses the structure of Indium gallium-arsenic. Sometimes there are PIN-photodiodes, avalanche. The metal-semiconductor-metal structures are ideal for embedding regenerators, short-wave multiplexers. Opticoelectric converters are often complemented by transimpedanese amplifiers, limiters producing a digital signal. Then practiced the restoration of sync pulses with phase auto-lifting frequency.

Transmission of light glass: History

Phenomenon of refractive, making a possible tropospheric bond, unloved students. Complex formulas, uninteresting examples kill the love of a student to knowledge. The idea of \u200b\u200bthe light guards gave birth to the distant 1840s: Daniel Colladon, Jacques Babe (Paris) tried to embellish their own lectures with tempting, visual experiments. The teachers of medieval Europe did not earn badly, so the fairness of students who carry money looked the desired perspective. Lecturers lured the public with any ways. Some John Tyndal took advantage of the idea of \u200b\u200b12 years later, much later by releasing the book (1870), considering the laws of optics:

• The light passes the border of the air-water section, the beam refraction relative to the perpendicular is observed. If the beam touch angle to the orthogonal line exceeds 48 degrees, the photons cease to leave the liquid. Energy is completely reflected back. The limit is called the limiting angle of the medium. The aqueous is 48 degrees of 27 minutes, silicate glass - 38 degrees 41 minutes, diamond - 23 degrees 42 minutes.

The birth of the XIX century brought Lines Petersburg - Warsaw Light Telegraph with a length of 1200 km. Regeneration of the Epistle operators was carried out every 40 km. Message went a few hours, the weather was prevented, visibility. The appearance of radio interpretation of old techniques. The first optical lines are dated to the end of the XIX century. I liked the novelty ... doctors! Bent glass fiber allowed to illuminate any cavity of the human body. Historians offer the following temporary development scale:

The idea of \u200b\u200bHenry Sant-René continued settlers of the new light (1920s), conceived to improve television. Clarence Hansell, John Logs Baird became pioneers. Ten years later (1930), a medical student Heinrich Lamm proved the possibility of transmitting glass image guides. Looking knowledge has conceived to examine body insides. The image quality was chrome, an attempt to get a British patent failed.

Birth of fiber

Independently Dutch scientist Abraham Van Hill, Briton Harold Hopkins, Briter Singh Kapani invented (1954) fiber. The achievement of the first in the idea to cover the central custody of the transparent shell, which had a low refractive factor (close to air). Surface scratch protection strongly improved the quality of the transfer (the contemporaries of inventors saw the main obstacle to the use of fiber lines in large losses). The British also made a serious contribution, collecting a bunch of 10,000 pieces with a bunch of 10,000 pieces, passed an image to a distance of 75 cm. A note "Flexible fibroscope that uses static scanning" decorated Nature magazine (1954).

It is interesting! The Singh Kapani laid the term fiber optic in the magazine of American Science (1960).

1956 brought the world a new flexible gastroscope, the authors of Basil Hirschovitz, Wilbur Peters, Lawrence Curtis (University of Michigan). A feature of the novikov was a glass sheath of fibers. Elias Noncister (1961) announced the idea of \u200b\u200bcreating a single-mode fiber. It is so thin that only one speck of an interference painting was felt inside. The idea helped doctors to inspect the insides (living) person. Losses amounted to 1 dB / m. Communication needs extended much further. It was required to reach a threshold of 10-20 dB / km.

1964 are considered a turning point: a vital specification has published Dr. Kao, introducing the theoretical foundations of long-distance communications. The document actively used the above number. The scientist proved: to reduce the loss will help the glass of the highest degree of cleaning. Hermann physicist (1965) Manfred Burner (telephone telephone Reerbs, Ulm) introduced the first working telecommunications line. NASA immediately dismissed the lunar pictures using new items (the development was secret). A few years later (1970), three workers Corning GLES (see the beginning of the topic) filed a patent that realizes the technological cycle of silicon oxide smelting. For three years, the Bureau estimated the text. The new lived increased channel bandwidth of 65,000 times relative to the copper cable. Team of Dr. Kao Needli made an attempt to cover a considerable distance.

It is interesting! 45 years later (2009) Kao was awarded the Nobel Prize in Physics.

Military computers (1975) United States of the United States (NORAD, SHIEN Mountains Section) received new communications. The optical internet appeared a long time ago, before personal computers! Two years later, the test tests of a telephone line of 1.5 miles (suburb of Chicago) successfully passed 672 voice channels. Glasses worked tirelessly: the beginning of the 80s brought the appearance of fiber with attenuation of 4 dB / km. Silicon oxide was replaced by another semiconductor - Germany.

The rate of production of high-quality cable of the technological line was 2 m / s. Chemale Thomas Mensa has developed a technology that has enhancing a twenty times specified limit. The novelty finally became cheaper copper cable. Further stated above: a surge of introducing new technology was followed. The distribution step of repeaters was 70-150 km. The fiber amplifier, doped with Erbia ions, sharply reduced the cost of the construction of lines. The times of the thirteenth five-year plan brought planet 25 million kilometers of fiber optic networks.

The new impetus to the development gave the invention of photon crystals. The first commercial models brought 2000. The frequency of structures allowed significantly to increase the power, the fiber design was flexibly adjusted, following the frequency. In 2012, the telegraph and telephone company Nippon reached a speed of 1 petabit / with a range of 50 km by one-sole fiber.

Military industry

The history of the Military Industry of the United States published in Montmouth Messed is reliably known. In 1958, the Cable Manager Fort Montmouth (Signal Corps Labs Army of the United States) reported on the dangers of lightning, precipitation. The official disturbed the researcher Sam di Vita, asking to find a replacement of green copper. The answer contained a proposal to try glass, fiber, light signals. However, Uncle Sma engineers of that time were powerless to solve the problem.

The late September 1959 di Vita asked the Lieutenant of the second rank of Richard of the Riczebukener, is it known whether the formula of glass is known to transmit an optical signal. The answer contained information relating to silicon oxide - samples based on the University of Alfred. Measuring the refraction coefficient of microscope materials, Richard has acquired a headache. 60-70% Glass powder freely passed radiant light, irritating his eyes. Holding in the mind the need to obtain the purest glass, the sturgebohecher studied modern production techniques with silicon chloride IV. Di Vita found material suitable, deciding to provide the government negotiations with glass windows of Corning.

The official knew the workers perfectly, but decided to offer a matter of publicity, so that the plant received a state contract. Between 1961 and 1962, the idea of \u200b\u200busing pure silicon oxide was transferred to research laboratories. Federal allocations amounted to about 1 million dollars (interval 1963-1970). The program ended (1985) the development of a multi-billion dollar industry production of fiber optic cables, which began to rapidly replace copper. Di Vita stayed to work, consulting industry, having lived 97 years (year of death - 2010).

Cable varieties

The cable form:

1. Core.
2. Shell.
3. Protective casing.

Fiber implements a complete reflection of the signal. The material of the first two components is traditionally the glass. Sometimes find a cheap replacement - polymer. Optical cables are combined with fusion. The alignment of the nucleus will require skill. Multimode cable with a thickness of over 50 μm to solder easier. Two global varieties vary by the number of modes:

• Multimode is equipped with a thick core (over 50 microns).
• Single mode significantly thinner (less than 10 microns).

Paradox: Lower size cable provides long-distance communications. The cost of four-core transatlastic is 300 million dollars. The core is covered with a light-resistant polymer. Magazine New Scientist (2013) announced the experiences of the scientific group of the University of Southampton, covering the range of 310 meters ... A waveguide! Passive dielectric element showed a speed of 77.3 Tbit / s. The walls of the hollow tube are formed by a photonic crystal. The information flow was moving with a speed of 99.7% light.

Photon crystal fiber

A new variety of cables is formed by a set of tubes, the configuration resembles rounded beesh cells. Photon crystals resemble a natural mother-in-law, forming periodic conformations that differ in refractive factor. Some wavelengths inside such tubes fade. The cable demonstrates the bandwidth, the beam is underway to bragging refractive reflects. Due to the presence of forbidden zones, the coherent signal moves along the light guide.

Optics opens up ample opportunities where high-speed communications with high bandwidth are required. This is a good proven, understandable and convenient technology. In the audiovisual area, it opens up new perspectives and provides solutions that are inaccessible using other methods. Optics penetrated all key directions - surveillance systems, dispatching and situational centers, military and medical facilities, in zones with extreme operating conditions. Wolves provide a high degree of protection of confidential information, allow you to transmit uncompressed data like high-resolution graphics and video with an accuracy of pixel. New standards and technologies of Vols. Fiber - Future SCS (structured cable systems)? We are building a network of enterprise.

Fiber optic (it is a fiber optic) cable - This is a fundamentally different type of cable compared to the two types of electrical or copper cable considered. Information on it is not transmitted by no electrical signal, but light. The main element is transparent fiberglass, along which the light passes at huge distances (up to top of kilometers) with a minor attenuation.

The structure of the fiber optic cable is very simpleand it looks like a coaxial electrical cable structure (Fig. 1.). Only instead of the central copper wire here is used here (with a diameter of about 1 - 10 μm) fiberglass, and instead of the inner insulation, a glass or plastic sheath, which does not allow the light beyond the fiberglass. In this case, we are talking about the mode of the so-called complete inner reflection of the light from the boundary of two substances with different refractive facilities (in the glass shell, the refractive index is significantly lower than that of the central fiber). The metal braid cable is usually absent, since the shielding from external electromagnetic interference is not required here. However, sometimes it is still used for mechanical protection against the environment (such a cable is sometimes called armored vehicles, it can combine several fiber optic cables under one shell).

Fiber optic cable has exceptional characteristics. By noise immunity and secrecy of the transmitted information. No external electromagnetic interference in principle can distort the light signal, and the signal itself does not generate external electromagnetic emissions. Connect to this type of cable for unauthorized listening network is almost impossible, since the integrity of the cable is disturbed. Theoretically, the possible bandwidth of such a cable reaches 1012 Hz, that is, 1000 GHz, which is incomparably higher than that of electrical cables. The cost of the fiber optic cable is constantly reduced and is now approximately equal to the cost of a thin coaxial cable.

Typical Signal attenuation in fiber optic cables At the frequencies used in local networks, ranges from 5 to 20 dB / km, which roughly corresponds to the indicators of electrical cables at low frequencies. But in the case of a fiber optic cable with an increase in the frequency of the transmitted signal, the attenuation increases very slightly, and at large frequencies (especially over 200 MHz) its advantages over the electrical cable are indisputable, it simply does not have competitors.

Fiber optic communication lines (WOLS) allow you to transmit analog and digital signals for long distances, in some cases, tens of kilometers. They are also used on small, more "controlled" distances, for example, inside buildings. Examples of solutions for the construction of SCS (structured cable systems) to build a network of an enterprise are here: we build a network of enterprises: the scheme of building SCS - optics horizontally. Building a network of enterprises: SCS construction scheme - centralized optical cable system. Building a network of enterprises: SCS construction scheme - zone optical cable system.

Advantages of optics are well known: it is immunity to noise and interference, the small diameter of cables with a huge bandwidth, resistance to hacking and intercepting information, no need in repeaters and amplifiers, etc.
Once there were problems with the terminal seal of optical lines, but today they are mostly solved, so it has become much simpler to work with this technology. There are, however, a number of questions that should be considered solely in the context of applications. As in the case of transmission over "copper" or radio channel, the quality of the fiber-optic communication depends on how well the output signal of the transmitter and the input cascade of the receiver are consistent. Incorrect signal power specification leads to an increase in the bit error factor during transmission; The power is too big - and the receiver amplifier is "oversaturated", too small - and there is a problem with noise, as they begin to interfere with the useful signal. Here are the two most critical parameters of the VOLS: the output power of the transmitter and the loss during the transmission - attenuation in the optical cable, which connects the transmitter and receiver.

There are two different types of fiber optic cable:

* multimode or multimode cable, cheaper, but less high-quality;
* Single mode cable, more expensive, but has the best characteristics compared to the first.

The cable type will determine the number of distribution modes or "paths" by which the light passes inside the cable.

Multimode cableThe most commonly used in small industrial, household and commercial projects has the highest weakening coefficient and works only at short distances. The older cable type, 62.5 / 125 (these numbers characterize the internal / outer diameters of the fiber in the ICM), often referred to as "OM1", has limited bandwidth and is used to transmit data at a speed of up to 200 Mbps.
Recently began to use Cables 50/125 "OM2" and "OM3", offering speeds of 1Gbit / s at distances up to 500 m and 10 Gb / s to 300 m.

Single mode cable Used in high-speed compounds (above 10 Gb / s) or long distances (up to 30 km). To transmit audio and video, the most appropriate is the use of "OM2" cables.
The vice-president of the EXTRON marketing department of Marketing Rainer Shattil notes that fiber-optic lines have become more affordable, they are more often used to organize a network inside buildings - this leads to an increase in the use of AV systems based on optical technologies. Shattil says: "In terms of Integration, the Volt has already possess several key advantages.
Compared to a similar copper-cable infrastructure, optics also use analog, and digital video signals simultaneously, providing a single system solution for working with existing, as well as with promising video formats.
In addition, because Optics offers very high throughput, the same cable will work with large permissions and in the future. Wolf easily adapts to new standards and formats that appear during the development of AV-technologies. "

Another recognized expert in this area is Jim Haze, the President of the American Fiber Optic Association, established in 1995, contributing to the growth of professionalism in the field of fiber optics and, among other things, in its ranks, more than 27,000 qualified specialists in the installation and implementation of optical systems. He speaks of the growth of Volce's popularity as follows: "The benefits are in the speed of installation and low cost of components. The use of optics in the field of telecommunications is growing, especially in Fiber-to-The-Home * (FTTH) systems with wireless support, as well as In the field of security (surveillance cameras).
It seems that the FTTH segment is growing faster than other markets in all developed countries. Here, in the United States, on the optics, road traffic management networks, municipal services (administration, firefighters, police), educational institutions (schools, libraries) are built.
The number of Internet users is growing - and we are rapidly built by new data processing centers (data center), for the relationship of which fiber is used. After all, when transmitting signals with a speed of 10 Gbps, the costs are similar to the "copper" lines, but optics consumes much less energy. For many years, fiber and copper adherents "beat" with each other for priority in corporate networks. In vain spent time!
Today, the connection on WiFi has become so good that users of netbooks, laptops and iPhons have preferred mobility. And now in corporate local networks, optics are used to switch with wireless access points. "
Indeed, the applications of optics are becoming more and more, mainly due to the above advantages over copper.
Optics penetrated all key directions - surveillance systems, dispatching and situational centers, military and medical facilities, in zones with extreme operating conditions. Reducing the cost of equipment made it possible to use optical technologies in traditionally "copper" regions - in conference rooms and in stadiums, retailers and transportations.
Rainer Shtale from Extron comments: "Fiber-optic equipment is widely used in medical institutions, for example, to switch local video signals into operational. Optical signals have no relation to electricity, which is ideal in terms of safety of patients. The Volt is great for medical schools, where you need to distribute video signals from several operating in several audiences so that students can observe the progress of the "live" operation.
Fiber optical technologies prefer and military, since the transmitted data is difficult or even impossible to "count" from the outside.
Wolves provide a high degree of protection of confidential information, allow you to transmit uncompressed data like high-resolution graphics and video with an accuracy of pixel.
The possibility of transmission to long distances makes optics ideally suitable for Digital Signage systems in large shopping centers, where the length of the cable lines can reach several kilometers. If for twisted pair distance is limited to 450 meters, then for optics and 30 km not the limit. "
As for the use of fiber in the audiovisual industry, two main factors contribute to progress here. Firstly, it is the intensive development of IP-based audio and video transmission systems that are based on a high bandwidth network - the Volt is fit for them perfectly.
Secondly, the widespread requirement to transfer HD video and HR computer images are large at distances than 15 meters - and this is the limit to transfer HDMI on copper.
There are cases where the video signal is simply impossible to "distribute" through the copper cable and it is necessary to apply fiber - such situations stimulate the development of new products. Being Ho Pak, Opticis Marketing Vice President, explains: "For UXGA data strip, 60 Hz, and 24-bit colors require a total speed of 5 Gbps, or 1.65 Gbps per color channel. HDTV has slightly smaller bandwidth. Manufacturers "pushing" the market, but also the market at the same time "pushes" players to use high-quality images. There are separate applications where displays are required that can display 3-5 million pixels or a 30-36-bit color depth. In turn, this will require the transfer rate of about 10 Gb / s. "
Today, many switching equipment manufacturers offer versions of video extension cords (extenders) to work with optical lines. ATEN International, Trendnet., Rextron., GeFen.and others produce various models for a variety of video and computer formats.
In this case, the service data is HDCP ** and EDID *** - can be transmitted using an additional optical line, and in some cases, on a separate copper cable that connects the transmitter and receiver.
As a result, the HD format became the standard for the broadcast market,in other markets - installation, for example, they also began to apply protection against unauthorized copying of content in DVI and HDMI formats, "says Jim Juchtte, Senior Vice President for the Development of Multidyne. - With the help of our company, HDMI-One devices, users can send a video signal from a DVD or Blu-Ray player to a monitor or display located at a distance of up to 1000 meters. Earlier, no device operating with multimode lines has not supported the HDCP copy protection system.

Those who work with Wolse should not forget about specific installation problems - the terminal seal of cables. In this regard, many manufacturers produce both connectors and assembly sets that include a specialized tool, as well as chemicals.
Meanwhile, any element of the Volt, whether the extension, connector, or a cable dust location, should be checked for loosening the signal - this is necessary to assess the total capacity budget (Power Budget, the main calculation rate of the Volt). Naturally, it is possible to collect fiber cables connectors and manually, "on the knee", but really high quality and reliability is guaranteed only when using ready-made, produced at the factory "broken" cables subjected to thorough multi-stage testing.
Despite the huge bandwidth of the Volt, many still have the desire to "shove" in one cable more information.
Here, development goes in two directions - spectral seal (Optical WDM) when several light rays are sent to one light guide with different wavelengths, and another - serialization / deserialization of data (eng. Serdes), when the parallel code is converted to serial and back.
At the same time, the equipment for spectral seal is expensive due to the complex design and use of miniature optical components, but does not increase the transfer rate. High-speed logic devices used in SERDES equipment also increase the expenditure part of the project.
In addition, the equipment is available today, allowing multiplexing and dehemultiplexing from a total light flow control data - USB or RS232 / 485. At the same time, the light streams can be sent one cable in opposite directions, although the price of the instruments perform these "tricks" usually exceeds the cost of an additional fiber to return the data.

Optics opens up ample opportunities where high-speed communications with high bandwidth are required. This is a good proven, understandable and convenient technology. In the audiovisual area, it opens up new perspectives and provides solutions that are inaccessible using other methods. At least without significant work efforts and cash costs.

Depending on the main area of \u200b\u200bapplication, fiber-optic cables are divided into two main types:

Internal gasket cable:
When installing the Volt in closed rooms, a fiber optic cable with a dense buffer is usually used (to protect against rodents). Used to build SCS as a trunk or horizontal cable. Supports data transfer to short and average distances. Ideal for horizontal closure.

External gasket cable:
Fiber optic cable with dense buffer, armored steel ribbon, moisture resistant. It is used for external gasket when creating the subsystem of external highways and are associated with each other separate buildings. May be laid in cable channels. Suitable for direct styling in the ground.

Exterior self-supporting fiber optic cable:
Fiber optic cable self-supporting, with steel cable. It is used for external laying over long distances within telephone networks. Supports the transmission of cable television signals, as well as data transmission. Suitable for laying in cable sewage and air gasket.

The advantages of the VOLS:

• The transmission of information on the Volt has a number of advantages before the transmission over the copper cable. The rapid introduction into WOLS information networks is a consequence of the advantages arising from the characteristics of the signal propagation in the optical fiber.
• The wide bandwidth is due to the extremely high frequency of carrier 1014Hz. This gives the potential transmission the possibility of one optical fiber of the flow of information into several teracitis per second. The big bandwidth is one of the most important advantages of optical fiber above the copper or any other information transfer medium.
• Small attenuation of the light signal in the fiber. Currently produced by domestic and foreign manufacturers, industrial optical fiber has a decay of 0.2-0.3 dB at a wavelength of 1.55 μm per kilometer. Small attenuation and a small dispersion make it possible to build plots of lines without repeaters with a length of up to 100 km and more.
• Low noise levels in the fiber-optic cable allows you to increase the bandwidth, by transmitting different modulation of signals with low code and code.
• High noise immunity. Since the fiber is made of dielectric material, it is immunity to electromagnetic interference from the surrounding copper cable systems and electrical equipment that can induce electromagnetic radiation (power lines, electric devices, etc.). Multiple cables also do not arise the problems of cross-influence of electromagnetic radiation inherent in multi-particle copper cables.
• Low weight and volume. Fiber optic cables (wok) have less weight and volume compared to copper cables per and the same bandwidth. For example, a 900-pair telephone cable with a diameter of 7.5 cm, can be replaced with a single fiber with a diameter of 0.1 cm. If the fiber is "dined" into a plurality of protective shells and coat steel tape armor, the diameter of such a wok will be 1.5 cm that several times less than the telephone cable under consideration.
• High security from unauthorized access. Since the wok practically does not radiate in the radio band, the information transmitted over it is difficult to overhear, without breaking reception. Monitoring systems (continuous monitoring) of the optical communication system, using the properties of the high sensitivity of the fiber, can instantly disable the "hack" communication channel and submit an alarm. Sensory systems using interference effects of distributed light signals (both different fibers and different polarization) have a very high sensitivity to oscillations, to small pressure drops. Such systems are especially necessary when creating communication lines in government, banking and some other special services imposing increased data protection requirements.
• Electroplating network elements. This advantage of optical fiber lies in its insulating property. Fiber helps to avoid electrical "land" loops that may occur when two non-insulated computer network devices associated with copper cable have grounding at different points of the building, for example on different floors. In this case, a large potential difference may occur, which is capable of damaging network equipment. For the fiber, this problem is simply not.
• Explosion and fire safety. Due to the lack of sparking, optical fiber improves the safety of the network on chemical, refineries, when servicing technological processes of increased risk.
• Economy of Vols. The fiber is made of quartz, the basis of which is silicon dioxide, widespread, and therefore inexpensive material, unlike copper. Currently, the cost of the fiber in relation to the copper pair correlates as 2: 5. In this case, the FOB allows you to transmit signals for significantly long distances without repeaters. The number of repeaters on the extended lines is reduced when using wok. When using soliton transmission systems, a range of 4,000 km was achieved without regeneration (that is, only using optical amplifiers on intermediate nodes) at a transmission rate above 10 Gb / s.
• Long service life. Over time, fiber is degradation. This means that attenuation in the paved cable gradually increases. However, due to the perfection of modern technologies for the production of optical fibers, this process is slowed down significantly, and the WOR's service life is approximately 25 years. During this time, several generations / standards of receiving and transmitting systems may be changed.
• Remote power. In some cases, remote power supply of the information network node is required. Optical fiber is not able to perform the functions of the power cable. However, in these cases, you can use a mixed cable when, along with optical fibers, the cable is equipped with a copper conductive element. Such a cable is widely used both in Russia and abroad.

However, the fiber optic cable has some drawbacks:

• The most important of them is a high difficulty of installation (when installing the connectors, micron accuracy is necessary, at the accuracy of glass fiber and the degree of polishing highly depends on the attenuation in the connector). To install the connectors, welding or gluing with a special gel having the same refractive index of light as fiberglass. In any case, for this you need a high qualification of personnel and special tools. Therefore, most often the fiber optic cable is sold in the form of pre-sliced \u200b\u200bslices of different lengths, at both ends of which the connectors of the desired type are already installed. It should be remembered that poor-quality installation of the connector sharply reduces the permissible cable length determined by attenuation.
• It should also be remembered that the use of fiber optic cable requires special optical receivers and transmitters that convert light signals into electrical and back, which sometimes significantly increases the cost of the network as a whole.
• Fiber optic cables allow signal branching (for this, special passive splitters are made for 2-8 channels), but, as a rule, they are used to transmit data only in one direction between one transmitter and one receiver. After all, any branching inevitably loosely loosens the light signal, and if there are many branches, the light may simply do not reach the end of the network. In addition, in the splitter there are internal losses, so that the total signal power at the outlet is less input power.
• The fiber optic cable is less durable and flexible than electric. The typical value of the permissible bend radius is about 10 to 20 cm, with smaller bending radii, the central fiber can break. Poor tolerate cable and mechanical stretching, as well as crushing effects.
• The fiber optic cable is sensitive to ionizing radiation, due to which the transparency of fiberglass decreases, that is, the signal attenuation increases. Consistent temperature differences also negatively affect it, can crack fiberglass.
• Apply fiber optic cable only in networks with a star and ring topology. There are no problems of matching and grounding in this case. The cable provides the perfect electroplating network of network computers. In the future, this type of cable is likely to ous out the electrical cables or, in any case, will strongly sweat them.

Prospects for the development of VOLS:

• Due to the growing demands imposed by new network applications, the use of fiber optic technologies in structured cable systems is becoming increasingly relevant. What are the advantages and features of using optical technologies in the horizontal cable subsystem, as well as on the workplaces of users?
• After analyzing changes in network technologies over the past 5 years, it is easy to see that the copper standards of SCs lagged behind the Race of Network Armaments. Not having time to install the SCS of the Third category, enterprises had to go to the fifth, now in the sixth, and not far from the mountain use the seventh category.
• Obviously, the development of network technologies will not stop at what has been achieved: the gigabit for the workplace will soon become a de facto standard, and later de Jura, and for LAN (local computing networks) of a large or even average enterprise 10 Gbit / s Etnernet will not be rare.
• Therefore, it is very important to use such a cable system that would allow you to easily cope with increasing speeds of network applications over the course of at least 10 years - it is such a minimum service life of the SCS is determined by international standards.
• Moreover, when changing standards for the protocols, it is possible to avoid re-laying new cables, which used to be the cause of significant expenditures for the operation of the SCS and simply not allowed in the future.
• Only one transmission environment in SCS meets the requirements of the optics. Optical cables are used in telecommunication networks for more than 25 years, recently they are also widely used in cable television and LAN.
• In LAN, they are mainly used to build main cable channels between buildings and in the buildings themselves. , When this is a high data transfer rate between the segments of these networks. However, the development of modern networking technologies actualizes the use of fiber optic as the main environment for connecting directly users.

New standards and technologies VOLS:

In recent years, several technologies and products have appeared on the market, allowing to significantly alleviate and reduce the use of fiber in the horizontal cable system and connecting it to the working points of users.

Among these new solutions, first of all, you would like to highlight optical connectors with a small form factor - SFFC (Small-Form-Factor Connectors), plane laser diodes with a vertical resonator - VCSEL (VERTICAL CAVITY SURFACE-EMITTING LASERS) and optical multimode fibers of the new generation.

It should be noted that the recently approved type of multimode optical fiber Om-3 has a bandwidth of more than 2000 MHz / km at the length of the laser radiation of 850 nm. This type of fiber provides serial transmission of the 10 Gigabit Ethernet data streams for a distance of 300 m. The use of new types of multimode fiber and 850 nanometer VCSEL lasers provides the smallest value of the implementation of 10 Gigabit Ethernet solutions.

The development of new standards of fiber-optic connectors made it possible to make fiber optic systems with a serious competitor to copper solutions. Traditionally, fiber optic systems required twice the number of connectors and switching cords than copper - in telecommunication items, a much large area was required to accommodate optical equipment, both passive and active.

Optical connectors with a small form factor, represented by a recently number of manufacturers, provide twice-greater density of ports than previous solutions, since each such connector contains two optical fibers in itself, and not one, as before.

This reduces the dimensions and optical passive elements - cross-bones, etc., and active network equipment, which reduces four times the cost of installation (compared to traditional optical solutions).

It should be noted that the American EIA and TIA standardization bodies in 1998 decided not to regulate the use of a certain type of optical connectors with a small form factor, which led to the emergence of six types of competing solutions in this area at once: MT-RJ, LC, VF-45, Opti-Jack, LX.5 and SCDC. There are also new developments today.

The most popular miniature connector is a MT-RJ connector, which has one polymer tip with two optical fibers inside. Its design was designed by a consortium of companies led by Amp NetConnect on the basis of the MT multipolocal mt multiple connector developed in Japan. Amp NetConnect today presented more than 30 licenses for the production of this type of MT-RJ connector.

MT-RJ connector is largely due to an external design, which is similar to the design of the 8-pin modular copper RJ-45 connector. Recently, the MT-RJ connector characteristics have noticeably improved - AMP NetConnect offers MT-RJ connectors with keys that prevent erroneous or unauthorized connection to the cable system. In addition, a number of companies develop single-mode variants of the MT-RJ connector.

Quite high demand in the market of optical cable solutions Enjoy the LC companies LC Avaya. (http://www.avaya.com). The design of this connector is based on the use of a ceramic tip with a reduced to 1.25 mm diameter and plastic housing with an external lever-type latch for fixing in the jack of connecting socket.

The connector is available in both the simplex and duplex option. The main advantage of the LC connector is low medium losses and their standard deviation, which is only 0.1 dB. Such value ensures the stable operation of the cable system as a whole. To install the LC plug, the standard passed procedure is applied on epoxy SMO and polishing. Today, the connectors found their use from 10 Gbit / C manufacturers.

Corning Cable Systems (http://www.corning.com/cableSystems) produces both LC and MT-RJ connectors. In her opinion, the SCS industry made its choice in favor of MT-RJ and LC connectors. Recently, the company has released the first single-mode connector of the MT-RJ and Unicam version of the MT-RJ and LC connectors, the feature of which is a small installation time. At the same time, to install UNICAM connectors, there is no need to use epoxy glue and poly

Introduction

Today, communication plays an important role in our world. And if copper cables and wires and wires were used to transmit information, now the time of optical technologies and fiber optic cables have come. Now, making a call on the phone to the other end of the world (for example, from Russia to America) or uploading a favorite melody from the Internet, which lies on the site somewhere in Australia, we do not even think about how to do it. And this is due to the use of fiber optic cables. In order to connect people, make them closer to each other or to the desired source of information, you have to connect the continents. Currently, the exchange of information between continents is carried out mainly through underwater fiber optic cables. Currently, fiber optic cables are laid along the bottom of the Pacific and Atlantic Oceans and almost the entire world "Eugenous" a network of fiber communication systems (Laser Mag.-1993.-№3; Laser Focus World.-1992.-28, No. 12; Telecom . Mag.-1993.-№25; AEU: J. Asia Electron. Union.-1992.-№5). European countries through the Atlantic are connected by fiber lines of communication with America. The United States, through the Hawaiian Islands and the island of Guam - with Japan, New Zealand and Australia. The fiber optic communication line connects Japan and Korea with Far East of Russia. In the West, Russia is connected with European countries. Petersburg - Kingisepp - Denmark and St. Petersburg - Vyborg - Finland, in the south - with Asian countries Novorossiysk - Turkey. At the same time, the main driving force of the development of fiber-optic communication lines is the Internet.

Fiber optic networks are definitely one of the most promising areas in the field of communication. The capacity of optical channels to orders is higher than that of information lines based on the copper cable.

Optical fiber is considered the most advanced medium for transmitting large information flows over long distances. It is made of quartz, the basis of which is a silicon dioxide - widespread and inexpensive material, unlike copper. Optical fiber is very compact and easy, it has a diameter of only about 100 microns.

In addition, fiber is immune to electromagnetic fields, which removes some typical problems of copper communication systems. Optical networks are capable of transmitting a signal over long distances with smaller losses. Despite the fact that this technology still remains expensive prices for optical components constantly fall, while the possibilities of copper lines are approaching their limit values \u200b\u200band requires more and more costs to further develop this direction.

It seems to me that the theme of fiber-optic communication lines is currently relevant, promising and interesting for consideration. That is why I choose it for my course work and I believe, then for the future of the future.

1. History of creation

Fiber optics Although it is an universally used and popular communication tool, the technology itself is simple and has been developed for a long time. An experiment with a variable direction of the light beam by refraction was demonstrated by Daniel Colladon (Daniel Colladon) and Jacques Babinet (Jacques Babinet) in 1840. The practical application of technology was found only in the twentieth century.

In the 20s of the last century, Experimients Clarence Hasnell (Clarence Hasnell) and John Berd (John Berd) also demonstrated the possibility of transmitting an image through optical tubes.

The invention in 1970 by Corning Fiberglass specialists are considered to be a turning point in the history of the development of fiber optic technologies. The developers managed to create a conductor, which is capable of maintaining at least one percent of the optical signal power at a distance of one kilometer. According to current standards, this is a rather modest achievement, and then, without a small 40 years ago, a prerequisite for developing a new type of wired connection.

E the first large-scale experiments associated with the advent of the FDDI standard. These first generation networks work so far.

E mass use of fiber optics associated with the production of cheaper components. The growth rates of fiber-optic networks are explosive.

E growth rates of information transfer, the appearance of wave seal technologies (WDM, DWDM) / new types of fibers.

2. Fiber optic communication lines as a concept

1 optical fiber and its types

The fiber optic communication line (Vols) is a type of transmission system, in which the information is transmitted by optical dielectric waveguides, known as "Optical fiber". So what is it?

Optical fiber - an extremely thin glass cylinder called a residential (Core), covered with a layer of glass (Fig. 1), called the shell, with other than that of the vein, refractive index. The fiber is characterized by the diameters of these areas - for example, 50/125 means fiber with a core diameter of 50 μm and an external shell diameter of 125 microns.

Fig.1 Structure of optical fiber

The light applies to the core of the fiber due to successive complete internal reflections on the interface between the core and the shell; His behavior is largely similar to how if he got into the pipe, the walls of which are covered with a mirror layer. However, unlike the ordinary mirror, the reflection in which is rather ineffectively, the complete internal reflection is essentially close to the ideal - this is their indigenous difference, allowing the light to spread along the fiber over long distances with minimal losses.

The fiber made in this way ((Fig. 2) A)) is called a fiber with a stepped profile of the refractive index and multimode, since there are many possible paths, or modes to spread the beam of light.

This set of modes leads to a dispersion (broadening) of the pulse, since each fashion passes into the fibers of a different way, and therefore different modes have a different transmission delay, passing from one end of the fiber to another. The result of this phenomenon is the limitation of the maximum frequency, which can be effectively transmitted at a given fiber length - an increase in or frequency, or a fiber length over the limit values \u200b\u200bsubstantially leads to a merging of the pulses following each other, because of which it becomes impossible to distinguish them. For typical multimode fiber, this limit is approximately 15 MHz km, which means that the video signal with the strip, for example, 5 MHz can be transferred to the maximum distance of 3 km (5 MHz x 3 km \u003d 15 MHz km). An attempt to transmit a signal to a greater distance will lead to a progressive loss of high frequencies.

Fig.2 Types of optical fiber

For many applications, this figure is unacceptable, and the search for the fiber design with a wider bandwidth. One of the paths is to reduce the diameter of the fiber to very low values \u200b\u200b(8-9 microns), so that only one mode becomes possible. Single mode, as they are called, fibers ((Fig.2) b)) Even effectively reduce the dispersion, and the resulting strip - a lot of GHz km - makes them ideal for public telephone and telegraph networks (RTT) and cable networks of television. Unfortunately, the fiber is so small diameter requires the use of a powerful, precision combined, and therefore a relatively expensive emitter on a laser diode, which reduces their attractiveness for many applications associated with a small length of the design line.

Ideally, a fiber is needed with a bandwidth of the same order as the single-mode fiber, but with a diameter, as in the multimode, so that it is possible to use low-cost transmitters on LEDs. To some extent, these requirements satisfy multimode fiber with a gradient change in the refractive index ((Fig.2) C)). It resembles a multimode fiber with a stepped change in the refractive index, which was mentioned above, but the refractive index of its core is non-uniform - it smoothly varies from the maximum value in the center to smaller values \u200b\u200bon the periphery. This leads to two consequences. The first - the light applies to a slightly bending path, and the second, and more important - the differences in the delay in the distribution of different modes are minimal. This is due to the fact that high fashion included in the fiber at a bigger angle and passing a greater way, actually begin to spread with a greater speed as they are removed from the center to the zone where the refractive index decreases, and are mostly moving faster than low-order modes remaining near the axis in the fiber in the area of \u200b\u200bthe high refractive index. The increase in speed just compensates for a larger path.

Multimode fibers with a gradient refractive index are not ideal, but nevertheless they demonstrate a very good strip value. Therefore, in most small and medium-sized lines, the choice of this type of fiber is preferable. In practice, this means that the bandwidth is only occasionally turns out to be a parameter that should be taken into account.

However, it is not so for attenuation. The optical signal fades in all the fibers, at a rate depending on the wavelength by the transmitter of the light source (Fig. 3). As mentioned earlier, there are three wavelengths, on which the attenuation of the optical fiber is usually minimal, - 850, 1310 and 1550 nm. They are known as the transparency windows. For multimode systems, the window at a wavelength of 850 nm is the first and most commonly used (the smallest price). At this length of the wavelength, the gradient multimode fiber of good quality shows attenuation of about 3 dB / km, which makes it possible to implement communication in a closed TV system at distances over 3 km.

Fig.3 Dependence of attenuation from wavelength

At a wavelength of 1310 nm, the same fiber shows even less attenuation - 0.7 dB / km, allowing you to proportionally increase the range of communication to about 12 km. 1310 Nm is also the first working window for single-mode fiber optic systems, at the same time is about 0.5 dB / km, which, in combination with transmitters on laser diodes, allows you to create a link link over a length of over 50 km. The second transparency window is 1550 nm - used to create even longer communication lines (fiber attenuation less than 0.2 dB / km).

2 Classification of wok.

The fiber optic cable has been known for a long time, even the early Ethernet standards for bandwidth of 10 Mbps are supported. The first one was called Foirl (Fiber Optic Inter-Repeater Link), and the subsequent - 10basef.

Today, there are several dozen firms in the world that produce optical cables for various purposes. The most famous of them are: AT & T, General Cable Company (USA); Siecor (FRG); Bicc Cable (United Kingdom); Les Cables de Lion (France); Nokia (Finland); NTT, Sumitomo (Japan), Pirelli (Italy).

Determining parameters in the manufacture of wok are operating conditions and communication bandwidth. Under the operating conditions, cables are divided into two main groups (Fig.4)

Insecurity are designed for laying inside buildings and structures. They are compact, easy and, as a rule, have a small construction length.

The mains are designed for laying in the wells of cable communications, in the ground, on the supports along the PP, under water. These cables are protected from external influences and a construction length of more than two kilometers.

In order to provide a large bandwidth of the communication line, the woks containing a small number (up to 8) of single-mode fibers with small attenuation, and switchgear cables may contain up to 144 fibers both single-mode and multimode, depending on distances between network segments.

Fig.4 Classification of wok.

3 Benefits and Disadvantages of Fiber Optic Signal Transfer

3.1 Benefits of the Volt

For many applications, fiber optics turns out to be preferable to a variety of benefits.

Low losses during transmission. Fiber optic cables with low losses allow you to transmit image signals over long distances without using route amplifiers or repeater. This is especially convenient for transmission schemes for long distances - for example, surveillance systems for motorways or railways, where non-barrier areas are incredible 20 km.

Broadband signal transmission. The wide range of optical fiber transmission allows you to simultaneously transmit high-quality video, sound and digital data to one fiber optic cable.

Immunity to interference and tips. The complete insensitivity of the fiber optic cable to external electrical interferences and pressures ensures the stable operation of the systems, even in cases where the installers did not give sufficient attention to the location of nearby power networks, etc.

Electrical insulation. The lack of electrical conductivity for fiber optic cable means that problems associated with changes in the potential of the Earth characteristic, for example, for power plants or railways. The same their property eliminates the danger of damage to the equipment caused by currents from lightning and so on.

Light and compact cables. The extremely small sizes of optical fibers and fiber optic cables allow you to inhale the second life in the packed cable channels. For example, one coaxial cable occupies as much space as 24 optical cables, each of which is supposed to simultaneously transmit 64 video channels and 128 audio or video signals.

Remaining line. A simple replacement of the terminal equipment, and not the cable themselves, fiber optic networks can be upgraded to transfer a larger amount of information. On the other hand, a part or even the entire network can be used for a completely different task, for example, combining in one cable of a local computing network and a closed TV system.

Explosion and fire safety. Due to the lack of sparking, optical fiber improves the safety of the network on chemical, refineries, when servicing technological processes of increased risk.

Economy of Vols. The fiber is made of quartz, the basis of which is silicon dioxide, widespread, and therefore inexpensive material, unlike copper.

Long service life. Over time, fiber is degradation. This means that attenuation in the paved cable gradually increases. However, due to the perfection of modern technologies for the production of optical fibers, this process is slowed down significantly, and the WOR's service life is approximately 25 years. During this time, several generations / standards of receiving and transmitting systems may be changed.

3.2 Disadvantages of Volt

High difficulty mounting. High qualifications of personnel and special tools. Therefore, most often the fiber optic cable is sold in the form of pre-sliced \u200b\u200bslices of different lengths, at both ends of which the connectors of the desired type are already installed. Using a fiber optic cable requires special optical receivers and transmitters that convert light signals into electrical and back.

The fiber optic cable is less durable and flexible than electric. The typical value of the permissible bend radius is about 10 to 20 cm, with smaller bending radii, the central fiber can break.

The fiber optic cable is sensitive to ionizing radiation, due to which the transparency of fiberglass is reduced, that is, the attenuation of the signal increases.

3. Electronic components of the Volt. Principle of information transfer

In the most general form, the principle of transmitting information in fiber-optic communication systems can be explained by (Fig. 5).

Fig.5 Principle of information transfer in fiber-optic communication systems

1 Fiber Optics Transmitters

The most important component of the fiber-optical transmitter is the light source (usually a semiconductor laser or LED (Fig. 6)). Both serve the same goal - generating a microscopic light beam, which can be introduced into fiber and with a high frequency to modulate (change in intensity). Lasers provide greater beam intensity than LEDs, and allow a higher modulation frequency; Therefore, they are often used for broadband lines of great lengths, such as telecommunications or cable television. On the other hand, LEDs are cheaper and more resistant devices, besides quite suitable for most systems of small or medium length.

Fig.6 Ways to enter optical radiation in fiber optic

In addition to the functional purpose (i.e., which signal it should transmit), the fiber optic transmitter is characterized by two more important parameters that define its properties. One is its output power (intensity) of optical radiation. The second is the wavelength (or color) of the emitted light. It is usually 850, 1310 or 1550 nm, the values \u200b\u200bselected from the condition of the coincidence with t. N. "Transparency windows" in the transmission characteristic of the optical fiber material.

3.2 Receivers for Fiber Optics

Receivers of fiber optics solve a vital problem - detecting extremely weak optical radiation emitted from the end of the fiber, and amplify the resulting electrical signal to the required level with minimal distortion and noise. The minimum radiation level required by the receiver in order to ensure the acceptable quality of the output signal, is called sensitivity; The difference between the sensitivity of the receiver and the output power of the transmitter determines the maximum allowable losses in the system in dB. For most closed TV surveillance systems with LED transmitter typical is a figure of 10-15 dB. Ideally, the receiver should work normally when changing the input signal in wide limits, since it is usually impossible to accurately predict in advance, what will be the degree of attenuation in the communication line (i.e. the length of the line, the number of joints, etc.). In many simple constructs of the receivers to achieve the required level of the output signal, manual gain adjustment, produced when installing the system. It is undesirable because the changes in the size of the attenuation of the line caused by aging or temperature change, etc., which dictates the need to periodically adjust the amplification. In all fiber-optic receivers, an automatic gain adjustment is used, which tracks the average level of the input optical signal accordingly changes the gain of the receiver. Neither when installing, no manual adjustment is required.

optical fiber communication cable

4. Objects of the use of Volt

Fiber optic communication lines (Vols) allow you to transmit analog and digital signals for long distances. They are also used on small, more controlled distances, for example, inside buildings. The number of Internet users is growing - and we are rapidly built by new data processing centers (data center), for the relationship of which fiber is used. After all, when transmitting signals with a speed of 10 Gbps, the costs are similar to the "copper" lines, but optics consumes much less energy. For many years, fiber and copper adherents "beat" with each other for priority in corporate networks. In vain spent time!

Indeed, the applications of optics are becoming more and more, mainly due to the above advantages over copper. Fiber-optic equipment is widely used in medical institutions, for example, to switch local video signals into operational. Optical signals have no relation to electricity, which is ideal in terms of safety of patients.

Fiber optical technologies prefer the military, since the transmitted data is difficult or even impossible to count from outside. Wolves provide a high degree of protection of confidential information, allow you to transmit uncompressed data like high-resolution graphics and video with an accuracy of pixel. Optics have penetrated into all key directions - observation systems, dispatching and situational centers in zones with extreme operating conditions.

Reducing the cost of equipment made it possible to use optical technologies in traditionally copper areas - in large industrial enterprises to organize automated technological process management systems (ACS TP), in energy, in safety and video surveillance systems. The possibility of transmitting a large flow of information on long distances makes optics perfectly suitable and in demand in almost all areas of industry, where the length of the cable lines can reach several kilometers. If the distance for twisted pair is limited to 450 meters, then for optics and 30 km not the limit.

As an example of the use of Vols, I want to describe a closed video surveillance system on a typical power station. This topic has become particularly relevant and in demand, after the adoption by the Government of the Russian Federation, the ruling on counter-terrorism and a list of vital objects to be protected.

5. Fiber optic observation systems

The process of system development, as a rule, includes two components:

Selecting suitable active components of the transmitting path based on the required function (or functions), the type and quantity of the available or proposed fibers and the maximum transmission range.

The design of the passive infrastructure of the fiber optic cable, including types and specifications of the main cable, connecting boxes, cable extension panels (Fiber Patch Panels).

1 components of the video surveillance transmission path

First of all - what components are actually required to satisfy the technical characteristics of the system?

Systems with fixed cameras - such systems are extremely simple and usually consist of a miniature fiber-optical transmitter and either modular or mounted in the receiving rack. The transmitter often has dimensions sufficiently small in order to mount it directly in the chamber housing, and is supplied with a coaxial bayonet connector, an optical connector 'ST' and terminals for connecting a low-voltage power supply (usually 12 per direct or alternating current). The viewing power plant surveillance system consists of several dozens of such cameras, the signals from which are transmitted to the central control post, and in this case the receivers are mounted in a standard 19-inch 3U format card with a shared power supply.

Systems on controlled chambers with rotary devices - such systems are more complex, as an additional channel is required to transmit the camera control signals. Generally speaking, there are two types of remote control systems with such cameras - requiring unidirectional transmission of remote control signals (from the central post to cameras) and requiring bidirectional transmission. Bidirectional transmission systems are becoming increasingly popular as they allow you to receive from each camera acknowledgment of the reception of each control signal, and therefore provide greater accuracy and reliability of control. Within each of these groups, there is a wide range of interface requirements, including RS232, RS422 and RS485. Other systems do not use a digital interface, but transmit data as a sequence of sound signals over an analog channel, similar to the signals of a two-frequency tone set in telephony.

Fig.6 Transfer of remote control signals by a swivel device by one fiber

All these systems can work with fiber optic cables when using the appropriate equipment. Under normal circumstances, the simultaneous transmission of optical signals on one fiber in opposite directions is undesirable, since mutual interference occurs due to the scattered reflection in the fiber. In closed TV systems, this effect creates an interference on the image whenever the camera controls is activated.

To achieve a bidirectional transmission over one fiber that does not create mutual interference, it is necessary that the transmitters at different ends of the fibers work at different wavelengths, for example, by 850 nm and at 1,300 nm, respectively (Fig.6). Each end of the fiber is connected by a coupler on a multiplexer with a wavelength separation (WDM - Wavelength Division Multiplexer), which ensures that each receiver receives the light from the transmitter at the opposite end to the end with the desired wavelength (for example, 850 nm). Unwanted reflections from the transmitter in the Middle end are in the "incorrect" range (i.e. 1300 nm) and comply with respectively.

Additional features - Although the selection of a fixed camera or camera on a rotary device meets the requirements of most of the closed TV surveillance systems, there are a number of systems that require additional features, such as the transfer of audio information - for general alert, auxiliary messages to the consumer or intercom communication with remote post . On the other hand, part of the integrated security system can be the contacts of sensors that are triggered during fire or the appearance of foreign ones. All these signals can be transmitted on fiber - or on the same that the network is used, or otherwise.

2 Multiplexing video signals

On one single-mode fiber, it is possible to multiplexing up to 64 video and up to 128 audio signals or digital data signals, or a few smaller numbers on multimode. In this context, the multiplexing refers to the simultaneous transmission of full-screen video signals in real time, and not a small-sided or polycript display, which is more often this term refers to.

The ability to transmit many signals and additional information on several optical fibers is very valuable, especially for closed TV surveillance systems with high length, for example, for motorways or railways, where minimizing the number of fiber optic cables is often vital. For other applications, with a smaller length and highly scattered cameras, the benefits are not so obvious, and here first should consider using a separate fiber line for each video signal. The choice of one, multiplexing or not, is quite complicated, and it must be done only after consideration of all moments, including the topology of the system, total costs and, not least, resistance to network damage.

3 cable network infrastructure

After the transmission path requirements are defined, the infrastructure of the cable fiber optic network is being developed, which includes not only the cables themselves, but also all the auxiliary components are connecting boxes, panels for cable buildings, bypass cables.

The first task is to confirm the correctness of the choice of the number and type of optical fibers defined at the stage of selecting the components of the path. If the system does not differ in great length (i.e., no longer than 10 km) and does not imply multiplexed video transmission, then, most likely, the optimal choice will be a multimode fiber 50/125 μm or 62.55 μm with a gradient refractive index. Traditionally, 50/125 μm fiber is selected for closed TV systems, and 62.5 / 125 microns for local computing networks. In any case, each of them is suitable for each of these tasks, and in general, in most countries, a fiber is 62.5 / 125 microns.

The number of required fibers can be determined based on the number and relative location of the chambers and whether unidirectional or bidirectional remote control or multiplexing is used. Since pipes. Cables intended for laying in external channels usually have moisture protection or aluminum tape (dry hollow pipes), or water-repellent filler (cables with gel filler). Cable for fire safety.

Many closed TV systems of low lengths have a star configuration, where the whole cable portion is laid from each camera before the control post. For such systems, the optimal cable design will contain two fibers - respectively to the transfer of video signal and remote control. This configuration provides one hundred percent stock by cable capacity, as if necessary and video, and remote control signals can be transmitted by the same fiber. More extensive networks can win from the use of "backstanding topology" (Inverted Branch & Tree Topology) (Fig. 7). In such networks from each camera, a two-tier fiber optic cable leads to a local "concentrator", where they are connected to a single stranded cable. The hub itself is not much more complicated by the usual all-weather connecting box and often can be combined with the equipment body of one of the chambers.

The increase in value when adding fiber optic lines to an existing cable is insignificant, especially compared to the cost of related public works, it is necessary to seriously approach the possibility of installing cables with a reserve by capacity.

Fiber-optic cables of trench bulft may contain steel wire reinforcement. Ideally, all cables should be made from low smoke platy-laying materials in order to satisfy local rules intended for laying in outer cable sealing or directly in trenches, usually have a hollow tube design containing from 2 to 24 fibers in one or more

Fig.7 Tree Topology Fiber Optic Network

The control of the input fiber-optic cable usually comes to the pairing unit, mounted in the 19 "rack, and each fiber has its own individual 'ST' connector. For the final pairing with the receiver, short rigidity cables with response' ST'- Connectors at each end. To fulfill all installation work, no special art is required, in addition to a reasonable understanding of the need for careful handling of optical fiber (for example, it is impossible to flex a fiber with a radius of less than 10 fiber diameters) and the requirements of general hygiene (i.e. purity).

4
Budget optical loss

It may seem strange that the calculation of the optical loss budget occurs at the same lateral stage of the development process, but in fact any accurate calculation is possible only after the cable network infrastructure is fully defined. The purpose of the calculation is to determine the losses for the worst way to pass the signal (usually the longest) and make sure that the equipment selected for the transmission path fits into the resulting limits.

Calculation is quite simple and consists in an ordinary summation of losses in the decibels of all components of the path, including attenuation in the cable (dB / km x length in km) plus both connector and losses on the joints. The greatest difficulty - simply extract the necessary figures of the loss of the manufacturer's documentation.

Depending on the result, the result may require the revaluation of the equipment selected for the transmission path to ensure acceptable losses. For example, it may be necessary to order equipment with improved optical parameters, and if it does not exist, it should be considered about the transition to the transparency window with a greater wavelength, where less losses.

5 Testing the system and commissioning it

Most fiber-optic network installation specialists provide optical test results for fiber optic network. At a minimum, they should include the measurement results using the end-to-end transmission of optical radiation power for each fiber-optic line - this is equivalent to checking the integrity for a regular network on copper cables with multiplexers of electrical signals. These results are represented as a loss of losses in dB, and they can be directly compared with the technical data on the equipment selected for the transmission path. Usually it is considered to be normal to have a minimum margin in terms of losses (the promised equipment parameters of minus the measured value) of 3 dB on the inevitable aging processes occurring in fiber-optic lines, especially in transmitters.

Conclusion

Often, specialists have the opinion that fiber optic solutions are much more expensive than copper. In the final part of my work, I would like to summarize the previously said and try it all to find out whether it is or not, comparing the optical solutions of 3M Volution with a typical shielded system of the 6th category, which has the closest multimode optics

In the estimated calculation of the value of the standard system, the port price of the 24-port switch panel was included (based on a single subscriber), subscriber and switching cords, a subscriber module, as well as the cost of a horizontal cable for 100 meters (see Table 1).

Table 1 Calculation of the value of the subscriber port of SCS for "Copper" 6th category and optics

This simple calculation showed that the cost of fiber-optic solution is only 35% more than solutions for twisted pair of the 6th category, so that rumors about the huge high-cost optics are somewhat exaggerated. Moreover, the value of the main optical components is comparable today or even lower than for shielded systems of the 6th category, but, unfortunately, ready-made optical switching and subscriber cords are as long as several times more expensive than copper analogs. However, if for any reason, the length of subscriber channels in the horizontal subsystem exceeds 100 m, the optics simply no alternative.

At the same time, the low value of the attenuation of optical fiber and "immunity" to various electromagnetic tips makes it an ideal solution for today's and future cable systems.

Structured cable systems that are used fiberboard both for trunk and horizontal cable channels provide consumers a number of serious advantages: a more flexible structure, a smaller occupied area in the building, high safety and better handling.

The use of optical fiber at workplaces will allow in the future with minimal cost to go to new network protocols, such as Gigabit and 10 Gigabit Ethernet. This is possible due to a number of recent achievements in the field of fiber optic technologies: multimode fiber optic with improved optical characteristics and bandwidth; Optical connectors with a small form factor that require less space and fewer costs when installing; Plane laser diodes with a vertical resonator ensure the transfer of data to a large distance with low costs.

A wide range of solutions for constructing optical cable systems provides a smooth, economically acquitted transition from copper to fully optical structured cable systems.

List of used literature

1. GUK M. Hardware of local networks / m. GUK - St. Petersburg: Publishing House "Peter", 2000.-572c.

Solutions for telecommunications and telecommunications

Energy. Electrical engineering. Communication.

Optical cables

Motherland O.V. Fiber Optic Lines / O.V. Motherland - M.: Hotline, 2009.-400C.

ATTENTION: All components of the SCS and VOLS, switching and electrical devices are supplied only within the framework of network projects, we do not deal with the distribution of equipment.

• Network based on cable type "twisted pair"
• Fiber optic networks

IC Telecom-Service offers design services, installation and service support for corporate communications based on the basis of WOLS. The unique offer of the company is in an integrated approach to the creation of corporate telecommunication and information systems. In addition to laying optics, we effectively implement the creation of office PBX and call-centers (including VoIP database), as well as the creation of data processing centers and storage.

IC Telecom-Service has partnerships with leading developers of solutions to create structured cable systems. The company has a full package of valid licenses, allowing to carry out a full range of work on network integration on industrial sectors.

The company's specialists carry out a full cycle of the project to build or upgrade the network infrastructure of the Customer, the construction of the WOLS and SCS - starting from the audit before the system launch and its subsequent maintenance.

While the possibilities of copper cable lines are approaching their limit values \u200b\u200band requires increasing costs for the further development of this direction, the prospects for the use of the Volt are becoming more economical and more efficient. Today, Volce is definitely one of the most promising areas in the field of communication. The capacity of optical channels to orders is higher than that of information lines based on the copper cable. In addition, the fiber optic communication lines are immunity to electromagnetic fields, which removes some typical problems of copper communication systems.

Basic concepts and fields of using Volt

The fiber optic communication line (Vols) is a type of transmission system, in which the information is transmitted by optical dielectric waveguides, known as "Optical Fiber".

Wolf is an information network connecting elements between the nodes of which are fiber-optic communication lines. Volt Technology In addition to fiber optic issues also cover issues related to electronic transmitting equipment, its standardization, transmission protocols, network topology issues and general issues of network construction.

The Volola is mainly used in the construction of objects in which the installation of the SCS should combine a multi-storey building or a high-length building, as well as when combining geographically scattered buildings.

The block diagram of the VOLS used to create the subsystem of external highways is shown in the figure.

Application areas and classification of fiber optic cables (wok)

Fiber optic cables used in the design and installation of the SCS are designed to transmit optical signals within the buildings and between them. On their basis, all three SCS subsystems can be implemented, although in the horizontal the fiber optic subsystem is still limited to ensure the functioning of the LAN. In the domestic highway subsystem, optical cables are applied equally often with cables from twisted pairs, and in the external highway subsystem they play a dominant role.

Depending on the main field of application, fiber-optic cables are divided into three main types:

• external gasket cables (Outdoor Cables);
• internal gasket cables (Indoor Cables);
• cables for cables.

External gasket cables are used when creating a subsystem of external highways and associated separate buildings among themselves. The main area of \u200b\u200busing the internal gasket cables is the organization of the internal highway of the building, while cables for cables are intended mainly for the manufacture of connecting and switching cords, as well as to perform a horizontal layout when implementing the Fiber To The Desk class projects (fiber to work space) and "Fiber To the Room" (fiber to room). The general classification of optical SCS cables can be represented as shown in the figure.

The advantages of the Volt

The transmission of information on the Volt has a number of advantages before the transmission over the copper cable. The rapid introduction into WOLS information networks is a consequence of the advantages arising from the characteristics of the signal propagation in the optical fiber.

Wide bandwidth - due to the extremely high frequency of carrier 1014 Hz. This gives the potential transmission the possibility of one optical fiber of the flow of information into several teracitis per second. The big bandwidth is one of the most important advantages of optical fiber above the copper or any other information transfer medium.

Small attenuation of the light signal in the fiber. Currently produced by domestic and foreign manufacturers, industrial optical fiber has a decay of 0.2-0.3 dB at a wavelength of 1.55 μm per kilometer. Small attenuation and a small dispersion make it possible to build plots of lines without repeaters with a length of up to 100 km and more.

Low noise in fiber optic cable Allows you to increase the bandwidth, by transmitting different modulation of signals with low code iax.

High noise immunity. Since the fiber is made of dielectric material, it is immunity to electromagnetic interference from the surrounding copper cable systems and electrical equipment that can induce electromagnetic radiation (power lines, electric devices, etc.). Multiple cables also do not arise the problems of cross-influence of electromagnetic radiation inherent in multi-particle copper cables.

Low weight and volume. Fiber optic cables (wok) have less weight and volume compared to copper cables per and the same bandwidth. For example, a 900-pair telephone cable with a diameter of 7.5 cm, can be replaced with a single fiber with a diameter of 0.1 cm. If the fiber is "dined" into a plurality of protective shells and coat steel tape armor, the diameter of such a wok will be 1.5 cm that several times less than the telephone cable under consideration.

High security from unauthorized access. Since the wok practically does not radiate in the radio band, the information transmitted over it is difficult to overhear, without breaking reception. Monitoring systems (continuous monitoring) of the optical communication system, using the properties of the high sensitivity of the fiber, can instantly disable the "hack" communication channel and submit an alarm. Sensory systems using interference effects of distributed light signals (both different fibers and different polarization) have a very high sensitivity to oscillations, to small pressure drops. Such systems are especially necessary when creating communication lines in government, banking and some other special services imposing increased data protection requirements.

Electroplating network elements. This advantage of optical fiber lies in its insulating property. Fiber helps to avoid electrical "land" loops that may occur when two non-insulated computer network devices associated with copper cable have grounding at different points of the building, for example on different floors. In this case, a large potential difference may occur, which is capable of damaging network equipment. For the fiber, this problem is simply not.

Explosion and fire safety. Due to the lack of sparking, optical fiber improves the safety of the network on chemical, refineries, when servicing technological processes of increased risk.

Economy wok. The fiber is made of quartz, the basis of which is silicon dioxide, widespread, and therefore inexpensive material, unlike copper. Currently, the cost of the fiber in relation to the copper pair correlates as 2: 5. In this case, the FOB allows you to transmit signals for significantly long distances without repeaters. The number of repeaters on the extended lines is reduced when using wok. When using soliton transmission systems, a range of 4,000 km was achieved without regeneration (that is, only using optical amplifiers on intermediate nodes) at a transmission rate above 10 Gb / s.

Long service life. Over time, fiber is degradation. This means that attenuation in the paved cable gradually increases. However, due to the perfection of modern technologies for the production of optical fibers, this process is slowed down significantly, and the WOR's service life is approximately 25 years. During this time, several generations / standards of receiving and transmitting systems may be changed.

Remote power. In some cases, remote power supply of the information network node is required. Optical fiber is not able to perform the functions of the power cable. However, in these cases, you can use a mixed cable when, along with optical fibers, the cable is equipped with a copper conductive element. Such a cable is widely used both in Russia and abroad.

Optical fiber communication Every day is gaining rapid popularity. And, it is worth noting, not at all in vain. It is based on special fiber. This approach allows you to achieve excellent indicators to transfer information to long distances. The use of such cables is fully justified. Operation of optical fiber elements has a lot of advantages.

The main advantages of optical fiber elements include:

• durability;


• strength;


• reliability;


• resistance to mechanical and external influences;


• broadband;


• minimum price;


• low weight;


• compact dimensions;


• resistance to interference electromagnetic waves.

This list can be continued for a very long time, as the optical fiber is really the most advanced environment for information transfer.

There are two types: single mode and multimode. Both possess the most important criteria: dispersion and attenuation. In itself, fiber includes the core and shell. It is noteworthy that they differ in between the refractive index.

As for the spread of EMV in the fiber, the single-mode has a diameter of the light-water vein of about 8-10 μm. This indicator is comparable with a wavelength. The multimode diameter is 50-60 microns, which makes it possible to spread a huge amount of rays.

History and features of optical fiber communication

Optical fiber communication - A popular and demanded way to transfer information.

Despite the fact that this technology is applied in the modern market relatively recently, its principle takes its origins since 1840, when Daniel Wandowko and Jacques Babienette demonstrated their experiment. This principle was that the change in the direction of the light beam was carried out by refraction.

However, the method actively began to be used in this area in the 20th century.

This type of communication has a mass gain, namely:

• small signal attenuation;


• presence of outsiders' protection;


• performing dielectric functions;


• long service life, etc.

Due to the fact that the signal attenuation indicator is relatively small, it is possible to build a system to 100 km and more. In turn, the broadband of the fiber allows you to transmit information on such a line at a huge speed. Usually it can vary up to 1 tbit per second. Despite the fact that the cost of welding and individual elements of the system is high, the construction of this type of communication is quite justified. Its application is a guarantee of a high-quality signal without interference and distortion.

More advantages of fiber optic communication

Fiber optic communication is widely used to transfer information. Fiber optic communication has a number of unique characteristics, which cause its popularity.

This type of communication appeared in 1840 after a demonstration of an experiment with a variable of the light beam by refraction. However, this type actively began to be used only recently.

There are a huge amount. This is directly:

1. Broadband. Through the use of such fiber, you can transfer information at high speed. It varies within up to 1 Tbit over a second. This indicator is due to the extremely high carrier frequency.


2. Available cost. Such fibers have an acceptable price, which allows them to use them for many purposes.


3. Small signal attenuation. This criterion makes it possible to build a considerable length line. It can vary up to 100 km and above.


4. Long service period. This type of lines, as practice shows, can be exceled to function at least a quarter of a century.


5. Resistance to interference. This prevents a decrease in the quality of the signal and its distortion.


6. The presence of protection against unauthorized foreign access. Information that is transmitted through this type of communication is practically no possibility to intercept without destroying the main cable.


7. Safety. Optical fiber is the same dielectric. Therefore, it significantly increases the fire and explosion safety of the entire system. This is especially true in enterprises that operate in an increased risk.

These are the main advantages of such lines. Due to this, high indicators are achieved and the excellent quality of the transmitted signal.

What is included in fiber optic communication?

Fiber optic lines are a whole system in which a number of devices are included.

The main of them should include the following devices:

• receiver;


• transmitter;


• preamp;


• a microcircuit designed to synchronize and restore information;


• converter code block into parallel and converter itself;


• laser formator;


• cable.

To date, there are two types of fiber. This is single and multimode. Already from their name becomes known for the principle of operation.

If only one ray is distributed in the first, then in the second - a lot. This is due directly to the refractive index. In a single-mode fiber, it is equal to the length of the light wave, and in multimode a few more.

It is worth noting that both types are characterized by two most important indicators: dispersion and attenuation.

Maintenance of fiber optic communication lines

Fiber optic communication lines are very popular. This is due directly to their capabilities and characteristics.

Maintenance of fiber-optic communication lines must be carried out regularly to avoid different errors, distortions in the transmitted signals and breakage.

It is noteworthy that this kind of operation should be trusted only by professional masters. This guarantees a complete exception of inaccuracies. In addition, such operations allow you to significantly extend the service life of both individual elements and the entire system.

Transfer of information at all times is relevant. In order for retransmission as high quality, powerful and productive devices should be selected. Before running the hardware, it must be configured in accordance with the required parameters.

To date, such systems are relevant to the use of fiber-optic communication lines. The use of such elements has a lot of advantages.

Such a system consists of active and passive objects, as well as fiber optic cables that function, as a rule, in the infrared range. Predesome - near.

It is the optical fiber today is the most perfect medium that serves to transmit information.

Among the masses of its advantages should be allocated the most important. It:

• affordable price;
• broadband;
• compactness;
• ease;
• small signal attenuation in fibers;
• resistance to electromagnetic interference.

For information transfer systems, the last criterion is of the most important. Thus, the signal comes without distortion along the entire route of its distribution.

But such elements are not devoid of disadvantages. First of all, the need for powerful active equipment when creating the entire system.

The second drawback is that the installation of optical fiber is carried out only by applying precision equipment. Such equipment has a fairly high cost.

Another minus is the high cost of correction of the breakdown. However, compared with a huge amount of advantages and functional characteristics, these shortcomings go to the background and are completely insignificant.

It should also be noted that such a fiber can be used in two varieties: single-mode and multimode. This name is due directly to variations in the spread of radiation in it.

Companies carrying out the maintenance of fiber optic communication lines at the exhibition

The Russian complex of the international level of the Expocentre FAQ is traditionally the organizer of a huge number of sectoral and thematic events. One of them - exhibition "Communication".

For exhibitors, an excellent opportunity is provided in the framework of the project to visit the business program, gain experience, get acquainted with innovations in this area and explore the current state of the industry.

The exhibition is structured by salons, which represents considerable convenience for participants. One of the directions is the maintenance of fiber-optic communication lines. Here, representatives of this segment can explore the basic principles and methods, which makes it possible to improve the situation.

Examples of fiber-optic communication and its advantage at the exhibition

Little just to know what the advantages of fiber optic communication. It is important to be able to apply them to correctly in practice, which will ensure the highest quality of the transmitted signal. It is for this purpose that thematic and sectoral events are held.

One of them is exhibition "Communication"which traditionally collects under one roof of the international complex "Expocentre" of the leading figures and representatives of the industry.

The event within an international scale has a significant impact on the development of the industry as a whole.

International Exhibition "Communication" Already that year attracts the attention of the representatives of this industry.

The exhibition is of great importance, as it contributes:

• development of the entire industry at the international level;


• the conclusion of new products to the global market;


• introducing innovation into production;


• exchange of experience and knowledge;


• enhance competitive ability;


• study of the main directions of the market.

Every year, leading figures and representatives of the segment are collected within the walls of the Expocentre FAQ in order to demonstrate existing developments and achievements. Here you can visit various conferences and symposia, where the most important areas are discussed, in particular and optical fiber communication.

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