Laying an optical cable over the air: price, methods, work plans. How to pull a fiber optic cable Installation of equipment in the entrance

They say that laying an optical cable on the ocean floor costs the Anglo-French concern Alcatel billions of dollars. One vein of glass with a thickness of 125 microns is capable of providing hundreds of terabits/sec. It is clear that there is an order of those wishing to connect the continents. It cannot be said that the connection was too reliable. In 2011, the news was reported: one grandmother left the country without the Internet. Let's get a look…

Optical cable

Information transmission via fiber optic cable

A pensioner from Georgia was looking for copper ... She came across a cable from a local telecommunications company. Most of Georgia lost the boarding school, almost completely Armenia. Modern optical fiber is capable of great feats. The first research began in the middle of the 19th century, in the following a number of inventions are presented to the public:

The fiber optic gastroscope was developed in 1956 by the University of Michigan.
Junichi Nishizawa pioneered the use of optical fiber for communication in 1963.
The first workable optical communication line was demonstrated in 1965 by Germany.
The first optical cable with acceptable attenuation was developed by STC employees Charles Kao, George Hockem. Nobel Prize awarded. Scientists raised the issue of glass purity, showed ways to improve the parameters by adjusting technological processes.

The transmission of information over cables exploits the ability of light to be re-reflected by internal walls. Most of the energy remains inside. The process of total reflection on the glass edge starts at an angle of 38 degrees. The signal fades slowly. The Alcatel concern uses repeaters to maintain the level. Each weighs half a ton. You can imagine how difficult it is to lay fiber optic cable under the ocean floor.

First, a 4,000 km section is loaded onto a ship for three weeks. The process runs at a speed of 100 meters per minute. Inside the huge compartment, workers lay the cable in rings around a vertical steel rod, in layers, like a coil. Several people are engaged, the weight of the product is relatively high. Each cable is formed by many intertwined strands of glass, the top of the bundle is covered with a steel screen, which gives the product strength.

A technological line has been developed for the production of cables. The future screen from the strip is twisted in a semicircle, an optical fiber core is laid inside. The structure is pulled through a series of steel rollers of decreasing caliber, reminiscent of the copper cable manufacturing cycle. The seam is welded, the cable is ready. It remains to cover with a waterproof shell. The cable withstands huge loads, any product undergoes a similar kind of test. In the Russian Federation, according to the standards, a glass hair can withstand a tensile strength of 7 kg.

Optical cable splicing methods

Methods for laying optical cables will tell little new things about traditional ones, the docking method is different. The main requirement here is the absence of mechanical damage. If the fiber is scratched, some of the energy will be lost. The quality of the connection is characterized by the loss in dB. A joint that has reached a figure of 0.4 dB is considered a marriage. A good welded joint will provide an indicator of 0.01 dB. To withstand stringent requirements, special equipment for the production of works is produced. Today, the following methods of connecting optical cables, mounting connectors have become widespread.

Welding

It is the easiest way, any type of optical cable is subject to. The parameters of which are stored in the software module of the device. By visiting the menu, the technician selects the desired type. The procedure is similar.

cable welding

First, let's find a sleeve (KDZS) on a fiber-optic cable of the appropriate thickness. The insulation is stripped a couple of centimeters. Kevlar braid is removable (if present). After the core is burned by a welding machine with a special grip. It is necessary to get rid of the isolation completely. The end is cut off (breaks off) with a cutter (structurally, it is part of the welding machine). Helps the cross section to become perfectly smooth. Both ends are processed alternately, on one we put a heat-shrink sleeve.

The welding process takes a matter of seconds, for quality control, the device can broadcast video (if you don’t like it, redo it). The connection loss value in dB appears on the display. Hundredths.

Mechanical connections

They have the advantage of being parsed n-th number of times. To perform the work, a special coupling is purchased, it is difficult to do without a tool: you will have to strip the insulation to a specified distance (tens of mm). After the tips are evenly cut with a device resembling a glass cutter. The ends are inserted into the sleeve, clamped. Installation is considered complete. We use one sleeve for fiber optic cores of different diameters, using special adapter inserts. The preparation process changes a little with little things.

Connectors

At the entrance of junction boxes, when connecting user equipment, connectors are more often used. Special connectors exhibit high losses, allowing switching to be changed countless times. Each company has its own technologies. Giganet has developed an instruction manual for specialized tools.

Cable stripping is an art. For the specified length, the outer insulation, braid are removed, the inner layer is cleaned (up to the core).

In the latter case, you need to act carefully, freeing the glass from excess material by centimeters. It is important not to break the vein, not to chip it off. The slightest scratch increases the loss through the walls. Fragments of glass easily pierce the skin.

The stripping is over, it's time to put on the insulators, the connector housing. The central vein is deliberately dragged through with a large margin.
We fill the connector with the compound that comes with the kit until a small droplet hatches through the central hole. It is important not to overdo it, not to combine the outer, inner circles of the coax.
The carrier fiberglass is lubricated with a hardener. Docking is done quickly so that the mixture does not have time to grab.
After a glass cutter (sold by Giganet), the core is cut, broken off with a small margin.
The process of grinding with a sandpaper of small size begins. A microscope is used for quality control. If a chip is found below the contact surface of the connector, the work remains to start over. Grinding is carried out until the surface is perfectly smooth.
Then finishing procedures follow, the product can be used.

How to lay optical cable

Inside the entrances, houses, the optical cable is laid, following the usual norms. The surface is fireproof; for installation, a packing tape is used, stuffed onto dowel-nails. In fact, the cable is equated to communication wires. Let's try to evaluate suitability!

Optical cable for laying in the ground (earth) is provided with a special marking. There is a letter Z after OK (optical cable). Some rules for laying an optical cable, the marking method are indicated by GOST R 52266.
Optical cable for indoor laying is marked with the letter C.
Optical cable for outdoor laying as such does not exist. The range includes submarine (H), air (V), field (P) cables.
Particularly flexible cords are marked with the letter W. You can bend, forgetting the restrictions.

Preparing for cable installation

Laying, installation of optical cables are carried out according to fire hazard. If the braid is made taking into account the features, the letters are added to the marking:

NG - does not propagate combustion.
LS (low smog) low emission of smoke, gas during combustion.
HF - reduced corrosivity of combustion products.
FR (fire resistance) - increased fire resistance.

It will come in handy, you will read the rules of use in the second section of the PUE 6. Now it is not in vogue, tables 2.1.2, 2.1.3 provide information that gives a live idea of how installation is customary. We are talking about an electrician, we will ask the doubters - did not you watch how the fiber-optic cables for external laying burn? At a certain power, a resonant process begins, during which the energy density is so high that the temperature reaches 10,000 degrees. Stop starting a fire.

And while a single thin strand of glass can power an area, remember that indoor fiber optic cables are poorly understood. Although the first telephone network in Moscow was launched in 1986, the last outdated one (1949) was removed in 2011. The phenomena of fire in fiber-optic cables have not even been studied yet, although providers have completely switched to technology. You will see, there is not even a single standard for gaskets. GOST refers entirely to the recommendations of narrower specifications. This is how the operating temperature, the minimum bending radius, and operating conditions are regulated. Even the tools are not listed, there are very few domestic developments, each company bends its own line.

trench laying

Separately, for installation, you should read the Guide for laying, installation and commissioning of fiber-optic communication lines. To eliminate interference, the cable is laid inside the HDPE pipe with an inner diameter of 25 mm, an outer diameter of 32 mm. It is not allowed to pull connected copper networks nearby. It is allowed to lay optical cables in cable ducts nearby (5-6 in number). If necessary, in the future, reports of copper communication wires should be used with a HDPE pipe, it is better to foresee the option in advance, do as described above. The requirement applies to sections longer than 2 km.

The standard indicates what precedes the laying of an optical communication cable:

According to the text, the HDPE pipe is supplied in coils. Using a fact, you can tell if the one on the counter is good.
If the pipe for the fiber optic cable gets stuck in the channel between the wells, you need to turn it several times.
Trimming in the trench is carried out, leaving a margin. Then, at the entrance to the channel, the pipe is pulled together with a clamp, held in place.

Other norms regarding laying in the ground of a similar kind. They look homegrown, but laying an optical cable in the sewer turns into a number of simple routine tasks. For installation, you can also look at SNiP 3.05.07. A section is given regarding the laying of a fiber-optic cable route in a building. It is indicated that the distance between fasteners does not exceed one meter, and when passing corners on each surface, the line is aimed at the wall.

Documents are old. Nowhere does it say that outdoor optical cable can travel over the air. Self-supporting varieties have been released for a long time. Some chapters on fiber optic cables are still relevant today.

vashtechnik.ru

Optical fiber is a real breakthrough in communication technology. Today, thanks to this kind of cables, high-precision and fast signal transmission over long distances is achieved without loss of quality. However, this technology has one drawback: the cable has to be “pulled”, enveloping it with a web of the city.

Laying methods
phasing

The rules for laying fiber optic cable are stipulated by many points. The first thing to decide is the type of cable. It depends on the conditions and method of laying, as well as on the object of installation. For example, aerial cabling uses aerial or self-supporting fiber optic cable. Universal, which is softer and lighter, is used indoors. A more reliable heavy cable with elements that protect against the harmful effects of the environment is laid in the cable duct. If the cable is laid in the ground, then special polymer pipes are used that protect against rodents and soil movements, they are equipped with a central power steel element. The cable itself is equipped with armor - a metal mesh. Most often, the cable is laid in a cable duct or laid in the ground. But there are other methods, more modern, among them: installation, using drilling in a horizontal direction, winding on a ground wire or laying in asphalt when a pavement is being built. In buildings, the rules for laying cables allow the use of low-current channels or voids behind a false ceiling. In addition, stacking in special trays is possible. When installing a cable in a building, you should strictly monitor the bending radii (they should not be less than the allowable for each cable individually). All cables used in buildings must be tested in accordance with fire safety conditions. When laying underground (into the ground), it is necessary to dig trenches at least 1 m deep, taking into account the length margin in those places where the cable is connected, as well as at the ends of the routes. The tightness of the cable is the main requirement when laying it through the cable well.

During air laying, all loads acting on the air-cable transition are taken into account. For example, it is necessary to take into account its sag, which varies depending on temperature fluctuations and cable tension, to calculate its length. If you know the ultimate tensile strength of the cable, you can calculate its tension, which is no more than 60% of the strength, then you can guarantee the reliability of laying along the supports.

The cable laying process consists of two stages - preparatory and main. For the preparatory stage, it is necessary to conduct an external examination and calculate the optical characteristics. During the visual inspection, the main emphasis is on checking the integrity and absence of damage, for example, in the insulation and in the cable drum. It also checks the compliance of the data indicated in the passport (attached to each coil) and indicated on the drum. First of all, when checking the optical characteristics, the specific attenuation of the fiber optic cable is determined and compared with the passport ones. At the same time, the integrity of the optical fibers is checked. After that, go to the main stage.

Sources:

Features of working with fiber

How to lay fiber optic cable

www.kakprosto.ru

2.3.2 Methods for laying optical cables when building fibers

There are several ways to lay a fiber optic cable, all of them have their own advantages and disadvantages, differ in the methods and conditions of work. For various laying methods, special types of optical cable are used. The main ways are:

cable laying in the ground (“manually” in a trench; trenchless, with the help of knife cable layers; in polyethylene pipes laid in the ground);

laying in a cable duct (in a cable duct; along protective pipes laid in a cable duct);

suspension of a cable with a power element on supports (power lines; lighting, urban transport, railway transport, etc.);

laying inside buildings and premises (internal laying);

laying through water barriers.

The construction of FOCL is considered to be a very complex production process. In particular, each laying of the main line, depending on the conditions of use (in the ground or on supports), requires the correct and high-quality selection of a certain type of cable. Of no small importance is the experience of handling optical fiber and the qualification of a specialist, without which high-quality installation and connection of the system will simply be impossible. Even laying fiber optic cable indoors will require increased attention and specific skills not used in conventional electrical wiring.

Laying fiber-optic cable in the ground. This is the most common way of laying FOCL in places where there is no cable duct. Unfortunately, this method is more expensive than overhead cable laying and takes more time. But the main advantage of such a communication line over others is its several times superiority in reliability.

The laying of fiber optic cable is carried out in soils of all categories, with the exception of soils subject to permafrost deformations.

The laying of an optical cable into the ground is carried out at an ambient temperature of at least -10 ° C. At lower temperatures (but not lower than -30 ° C), the cable must be kept for two days in a heated room and warmed up on a drum immediately before laying.

Laying FOCL in open ground involves the use of an armored cable. The thickness of the armor depends on the structure of the earth (soil) and its infestation with rodents. Cable armor must be connected in couplings and grounded to protect fiber-optic transmission systems from thunderstorms and the effects of power lines (especially in places of approach to dangerous objects). In some cases, for example, when laying an FOCL cable in close proximity to power lines (along railways), it is recommended to use an optical cable without metal elements. At the same time, in order to be able to identify and trace such lines in the future, it is necessary to use special markers at the construction stage.

There are two basic methods for laying fiber optic cable in the ground: it is either laying the cable in a trench (trench method), or the trenchless method is used using cable layers or horizontal directional drilling rigs.

The trench method of laying FOCL in the ground is most often used when installing a group of cables, while the width of the trench can be such that a vehicle (tractor) can fit directly inside the trench. Cables are laid into the ground also in ordinary trenches, about 50 cm wide, as well as in mini-trenches. The latter are about ten centimeters wide. They are used when laying FOCL in the ground on cottage plots and lawns. The depth of the cable laying in this way is not great, but the appearance of the sections does not deteriorate.

The disadvantage of this method is its complexity and low productivity. As a rule, the trench method is used when, due to terrain conditions, it is impossible to use a cable layer. The trenching is carried out by mechanisms (excavator, cutter) or manually if the cable route passes in places where it is not possible or prohibited to use heavy equipment. The cable is laid on a prepared cushion at the bottom of the trench. When various obstacles cross the route, the cable under them is laid in a pre-laid polyethylene pipe, which also helps to protect the cable in difficult sections of the route from the effects of an external aggressive environment, from mechanical damage by rodents. The backfilling of the trench is carried out with manually excavated soil or by mechanisms in layers (the thickness of each layer is 200 mm) with the laying of a signal tape in the trench.

The most common and economical way of trenchless laying of FOCL is the laying of armored cable into the ground using a knife cable layer due to the high speed of the mechanized process and a fairly high laying speed (Figure 2.3). It is applicable only on lines of relatively short length (no more than 100 km). Basically, this technology is used in the presence of a smoothly changing terrain and relatively uncomplicated soils, moreover, in those directions where a sharp increase in traffic requiring the laying of new cables is not expected in the near future.

This method ensures the optimal depth of the route (about 1.2 meters). The technology for performing work involves cutting a narrow slot in the ground with a cable layer and laying a cable on its bottom. The laying in the ground is carried out according to a specially designed scheme for fiber optic cable, when the cable drum is mounted in front of the cable-laying tractor. To reduce high mechanical loads (longitudinal tension, transverse compression, bending, vibration) on the cable that occur on the way of its movement from the drum to the exit from the cable guide cassette, a forced rotation of the drum is created and clogging of the cable-laying knife cassette is not allowed when laying the cable into the ground. The laying process is continuously monitored, which implies compliance with the following technological parameters: constant laying speed; constant inclination of the cable layer; exclusion of sharp cable bends; avoid exceeding the allowable stretch of the fiber optic cable.

Figure 2.3 - Laying an optical cable with a cable layer

In some areas, a combination of technologies is possible. Horizontal directional drilling is used at the crossing points of roads, railways, as well as rivers, ravines and swamps. In these sections, the cable is laid in laid pipes.

With any method of laying the cable directly into the ground, pits are torn off at the joints of construction lengths to accommodate optical couplings and a supply of optics. The reserve should provide the possibility of supplying the coupling to a zone convenient for organizing the workplace of installers. Optical couplings are used to connect construction lengths. To ensure the possibility of measuring the insulation resistance of the outer shells at each construction length or in sections of several construction lengths, ground wires connected to the armor are brought out of the couplings into the container of ground wires. Using jumpers, you can connect the armor of a fiber optic cable to the container, and if necessary, remove the jumpers and measure the insulation resistance.

Laying fiber-optic cable in the cable duct. The laying of optical communication cables in cable ducts is carried out both manually and mechanized using standard mechanisms and devices. At the same time, the following requirement must always be strictly observed: tensile strength, bending radius, temperature during installation and permissible compressive force must comply with the requirements of the specifications for the cable to be laid in order to avoid breakage and hidden damage to the fibers.

Cable sewerage consists of a pipeline and wells (Figure 2.4). The cable is laid in a cable conduit, and possible connections are made in cable wells or cable shafts. Manholes have manholes. All sewers are located underground, and only hatches of manholes are brought to the surface, closed with cast-iron covers, under which steel lockable covers are located.

Before laying the cable in the cable duct, a check is made for the patency of its channels and, if necessary, repair of the sewer, as well as repair and retrofitting of cable wells. For more efficient use of cable ducts and the possibility of laying optics in the same channel with copper cables, protective polyethylene pipes are laid in them.

1 - cast iron covers; 2 - pipelines; 3 - cable; 4 - viewing wells; 5 - hatches

Figure 2.4 - Cable duct

Laying in cable ducts is carried out mainly by hand tightening or with the help of winches. When laying optical fiber in protective tubes, the push method can be used.

Laying is carried out taking into account the following factors:

a turn of the route at an angle of 90° is equivalent to an increase in the length of the straight section by 200 m;

the bending radius of the OK when laying should not be less than 20 outer diameters of the OK;

it is not allowed to exceed the value of the traction force, normalized for a particular OK;

in order to avoid damage to the plastic channels of cable ducts, a synthetic traction halyard (nylon, polypropylene) is used;

do not use lubricant to reduce friction when laying the OC, since the OC shell may crack or, due to the polymerization of the lubricant, it may be difficult to remove the OC from the cable duct;

it is not allowed to push OK into the bend of the cable duct;

the drum with OK when laying should be rotated evenly by the drive or manually, but not by the thrust of the laid OK.

On difficult sections of the route and in the presence of large building lengths of the cable, it is laid in two directions from one of the transit wells (preferably a corner one), located approximately one third of the length of the route. At first, it is advisable to lay a large length of cable, then unwind the remaining cable on the drum, lay it in a “figure of eight” near the well and then lay it in the other direction.

The construction lengths of the optical cable are connected using through-through or dead-end optical couplings of various designs. The specific type of couplings is determined based on the conditions of placement in the well and is indicated in the project documentation.

In the case of tightening the optical cable using a traction or winch mechanism, a roller mechanism is used at the point where the cable enters the well to prevent damage to the cable. The cable pulling speed should not exceed 30 m/min. In walk-through wells, the cable is laid out along the walls and tied up on the console with cable ties. The place where the optical cable enters the cable well is sealed with a gland to prevent silting or flooding of channels in the spring. In the end wells, sufficient cable stock is left for the installation of optical couplings with the removal of the cable into a specialized vehicle (optical laboratory), in which optical measurement and fiber splicing are carried out.

Fiber optic cable suspension. WOK suspension options have a number of advantages compared to other construction methods: no need for land acquisition and coordination with interested organizations; reduction of construction time; reduction in the number of damages in urban areas and industrial zones; reduction of capital and operating costs in areas with heavy soils.

The suspension of fiber-optic cables is carried out on already installed supports and does not require careful preliminary preparation of the laying route, therefore it is more technologically advanced and easier than laying in the ground.

For laying FOCL by suspension to supports, the suspension of an optical fiber cable to a steel cable is often used, which is stretched between supports on consoles. It is also used to suspend the fiber optic cable with a built-in cable on specially designed consoles.

When hanging a fiber optic cable to a steel cable, each console is attached to the support using special screws. Taking into account the normal sag of the boom, the installation height of the consoles should be such that the distance from ground level to the lowest point of the cable is 4.5 m or more. The fiber optic cable is attached to the cable with hangers made of galvanized sheet steel. Such hangers must move freely along the steel cable and tightly wrap around the fiber optic cable.

In the case of suspension of a fiber optic cable in which a carrier cable is embedded, standard fittings and a support clamp are used. For tension fastening of a self-supporting fiber optic cable, spiral clamps are used (remounting of spiral tension and support clamps is prohibited).

The most important difference between laying by hanging fiber-optic cables from other methods is that the splicing points of two building lengths must be located on the support along with the technological margin of the cable, sufficient for descent from the support, as well as for restoration work in case of emergency situations on the line . Fiber optic cable length splicing is always carried out in an assembly vehicle or tent. This necessitates the reservation of greater lengths of the technological reserve than when laying in the ground. In addition, it is necessary to pay attention to the reliable fixing of the reserve, since being on a support is associated with a constant effect of wind loads.

Laying FOCL inside buildings, in comparison with other types of installation, is less expensive and does not present any particular difficulties. The design of the fiber optic cable used for these purposes is more flexible and lighter, and the length of the routes is small, which greatly simplifies installation.

Ways of laying FOCL inside the building, as a rule, depend on the purpose of the room. In industrial premises, communication centers, FOCL and other communications are laid along cable ladders, cable ladders, and guides. Sometimes cables are fixed to the ceiling with special hooks and hangers. Fiber optic lines are laid inside buildings along cable trays and guides using cable rollers, a winch, and devices for unwinding cable drums.

During construction inside the object sections of the FOCL, a cable with a fire safety certificate must be used. Such a cable can be recognized by the letter "H" in its marking. It does not burn, does not support combustion, does not emit toxic gases, but decomposes into aluminum oxide and water.

Laying FOCL through water obstacles (along the bottom) is the most costly way of laying a fiber optic cable. If we are talking about crossing a river, then if there is a bridge, the cable is laid along it, and in its absence, suspension is used using air supports or along the bottom of the reservoir. Since the environment for laying FOCL is changing (there was earth, and now water, or air), then the type of cable should also change accordingly. An optical sleeve is installed on the shore, in which an armored optical cable for laying in open ground is spliced with a self-supporting optical cable for suspension on supports above the river, or underwater, for laying fiber optic lines along the bottom of water obstacles. At the locations of the couplings, technological reserves of the cable are organized.

In railway transport, during the construction of FOCL, the most widely used methods are the suspension of a fiber-optic cable on the supports of the contact network of electrified railways and high-voltage automatic blocking lines, as well as laying in pipelines. Due to the air suspension, capital costs for construction are reduced by up to 30% compared to its underground laying. At the same time, the construction time for FOCL is significantly reduced. At the same time, favorable conditions are provided for inspecting line-cable structures when planning routine and preventive maintenance during the technical operation of transmission lines, favorable opportunities are created for the timely access of operating personnel to the place of work, including emergency recovery.

The main advantage of the air suspension of a fiber optic cable is that there is practically no preliminary preparation of the route, since it is already defined by the existing overhead line. In addition, the construction of linear devices is minimized, since they are already built, which means that the time for construction is significantly reduced.

However, cable suspension on poles has some disadvantages. So, when laying underground, a fiber-optic cable is less susceptible to negative factors that affect the stable operation of fiber-optic communication lines. Therefore, when planning and creating digital communication networks of railway transport, it is necessary to take into account the consequences of the influence of external and internal destabilizing factors, as well as to evaluate the measures taken by operational units to ensure reliable and stable operation of the communication network in real environmental conditions and the accepted system of technical operation.

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Laying fiber optic cables

Fiber optic cables have gained a lot of popularity due to their ability to interconnect infrastructure network devices. Their use allows you to transfer data over long distances at a higher throughput (data transfer rate) than using other network data transmission media.

Optical fiber is a flexible, but very thin and transparent cable made of pure glass (quartz) as thick as a human hair. In a fiber optic cable, bits are encoded as light pulses. The fiber optic cable acts like a light guide, transmitting light from both ends of the cable with minimal signal loss.

For an analogy, imagine an empty paper towel roll with a thousand-meter-long mirror surface on the inside, and a small laser pointer used to transmit Morse signals at the speed of light. Essentially, this is how fiber optic cable functions, only it has a much smaller diameter and uses sophisticated light emitting and receiving technologies.

Unlike copper wires, fiber optic cable can transmit signals with lower attenuation and is completely immune to EMI and RFI.

Currently, fiber optic cables are used in four types of production.

Corporate networks. Fiber optic cable is used for laying the backbone cable system and connecting network devices that implement the infrastructure.

Fiber-to-apartment technology and access networks. Fiber to the Home (FTTH) technology is used to provide permanent connectivity to broadband access networks for individuals and small businesses. FTTH technology supports the use of high-speed Internet access, as well as remote data transmission, telemedicine and video-on-demand.

Long distance networks. Providers use long distance terrestrial fiber optic networks to provide international and long distance connectivity. Typically, these networks operate in the range from several tens to several thousand kilometers and support speeds up to 10 Gbps.

underwater networks. Special fiber optic cables are used to provide reliable, high-speed, high-capacity links that can operate in harsh deep-sea conditions and run across the oceans.

We are focused on the use of fiber optic cable within the enterprise.

Fiber optic cable design

Although the optical fiber is very thin, it consists of two types of glass and is protected by an outer shield. In particular, fiber optic components include:

The core - consists of transparent glass and is part of the fiber through which light passes.

The cladding of an optical fiber is the glass that surrounds the core and acts as a mirror. Light pulses that pass through the core are reflected by the cladding. Due to this, they are retained in the core of the fiber, representing the phenomenon of total internal reflection.

The outer sheath is usually made of polyvinyl chloride (PVC), which protects the core and sheath of the cable. The fiber may also include reinforcing materials and a buffer (cladding) to protect the glass from scratches and moisture.

Although the core and shell are susceptible to sharp bending, they have become less susceptible to them as a result of changes in properties at the molecular level. The optical fiber has undergone rigorous production testing. It has been proven that optical fiber can withstand a minimum of 20,000 kg per square centimeter. The optical fiber is strong enough that it is not damaged during installation and use in harsh environmental conditions.

Light pulses, which represent transmitted data as bits in the medium, are generated by:

semiconductor devices called photodiodes that sense light pulses and convert them into electrical signals that can then be converted into data frames.

Note. The laser beam transmitted through the fiber optic cable can cause damage to the eyes. Therefore, precautions should be taken when working with active fiber optic cable.

Fiber optic cables can be classified into two types.

Multimode fiber optic cable (MOF): consists of a core with a larger diameter and uses LEDs to transmit light pulses. The pulse from the light emitting indicator enters the multimode fiber at different angles. The MOC is often used in local area networks because it can be operated using inexpensive LEDs. This type of cable provides a bandwidth of up to 10 Gb / s at a distance of up to 550 meters.

On fig. 1 and 2 highlight the characteristics of the IOC and OOC. One of the main differences between IOC and OOC is the value of the variance. Dispersion is the scattering of a light pulse over a certain period of time. The greater the dispersion, the greater the signal loss.

Network fiber optic connectors

An optical fiber connector is placed at the end of an optical fiber. There are various connectors for fiber optic cables. The main differences between these types of connectors are the dimensions and methods of mechanical connections. Typically, organizations favor one type of connector, depending on the equipment they use, or assign a separate connector type to each type of fiber (one for MOK cables, one for OOK cables). Currently, about 70 types of various connectors are used.

As shown in Figure 1, the three most common fiber optic connector types are as follows.

Straight Connector (ST): An obsolete connector type widely used with multimode fiber.

Subscriber connector (SC): also called square or standard. Widely used in LANs and WANs, this type of connector is equipped with a self-locking mechanism to ensure a secure installation. It is also used with multi-mode and single-mode fiber optic cable.

Luminous connector (LC): also called a small or local connector. Its popularity is growing rapidly due to its small size. It is used with single mode fiber optic cable and supports multimode cable.

Note. Other fiber cable connectors, such as the Crimp Connector (FC) or Subminiature A (SMA), are rarely used in LANs and WANs. The biconical connector and the D4 connector are obsolete connector types. These connectors are not covered in this chapter.

Since light travels in only one direction through fiber, two fiber optic cables are required for full-duplex operation. Thus, fiber patch cables can link two fiber optic cables to a pair of standard connectors. Some fiber optic connectors can be connected to both transmit and receive fiber using a single connector called a duplex connector. It is shown in fig. 1.

Fiber optic patch cables are required to connect the infrastructure devices. Some of the common connecting cables are shown in fig. 2.

SC-SC Multimode Patch Cable

LC-LC Single Mode Patch Cable

ST-LC multimode connection cable

SC-ST Single Mode Patch Cable

Unused fiber optic cables should be protected with a small plastic cover.

Also, pay attention to color coding to distinguish between singlemode and multimode patch cables. According to the TIA-598 standard, a yellow jacket is used for single-mode fiber cables, and orange (or aqua) is used for multimode cables.

Testing fiber optic cables

Termination and connection of fiber optic cables requires special training and equipment. Incorrect termination of the fiber optic cable will result in a reduced signal propagation distance or complete transmission failure.

The three most common fiber termination and splicing errors are:

Offset: Fiber optic cables are not adjacent to each other when connected.

Disconnection: Cables do not fully touch when spliced or spliced.

Polishing: the ends of the cables are not sufficiently cleaned of dirt.

A quick and easy way to test a cable is to use a bright electric torch, pointing it at one end of the fiber while watching the other end. If light is visible, then the fiber can transmit light. While this test does not measure fiber performance, it is a quick and inexpensive way to detect damaged fiber.

It is recommended to use an optical tester to test fiber optic cables, as shown in the figure. An optical time domain reflectometer (OTDR) can be used to test each segment of a fiber optic cable. This device injects a test pulse of light into the cable, measuring the backscatter and reflection of light over time. The optical reflectometer calculates the approximate distance at which problems are detected along the entire length of the cable.

Fiber optic cables and copper cables

The use of fiber optic cables offers many advantages over copper cables.

Because the fibers used in a fiber optic transmission medium are non-current conductors, the medium is not subject to electromagnetic interference and does not conduct unwanted electrical current due to grounding. Because optical fibers are thin and have relatively low signal loss, they can be used over much longer distances than copper media without the need for signal recovery. Some specifications of optical fiber at the physical layer provide data transmission over several kilometers.

When implementing fiber optic cables, the following points should be considered.

More costly when running at the same distance than copper cables (but they provide more bandwidth).

Special skills and equipment are required for terminating and splicing the cable infrastructure.

Requires more careful handling than copper cables.

Currently, in most enterprise environments, fiber optic cables are preferred for cabling and providing high-speed point-to-point connections between devices, as well as for campus communications. Since fiber optic cable does not conduct electricity and has low signal loss, it is ideal for this purpose.

This figure highlights some of the differences.

There is no one universal technology for cutting a fiber optic cable for installation. Each coupling has its own specifics, which are specified in the instructions for it. It may be necessary to completely cut off the Kevlar threads, or vice versa, leave and clamp them in the mount, cut off the strength element, or vice versa, provide for its sufficient length.

General advice - be sure to observe the prescribed length of the fibers released during cutting, do not make them too short. Otherwise, installation will be difficult.

At the same time, each stage of cable cutting has its own practical nuances - that's what we'll talk about today. And let's start with the tools that are used by professional fiber optic installers and shareholders.

Tools for cutting optical cable

The main arsenal of the assembler-solber of fiber optic networks for cable cutting:

Stripper knife;
Stripper clothespin;
D-Gel hydrophobic lubricant solvent;
Pliers;
Model knife.

As well as side cutters, ties, a vial for alcohol, screwdrivers and other tools. On sale there are special suitcase sets for working with optics, for example, NIM-25:

Cutting and installation of an optical cable into the sleeve in stages.

The first thing to do if the cable has been stored for a long time in a humid environment without end waterproofing is cut and discard approximately 1 meter of cable. Optical fiber and other structural elements lose their qualities with prolonged exposure to moisture.

This is especially true for optical cable reinforced with Kevlar threads. They perfectly absorb and "transmit" moisture for many meters. Subsequently, if such a cable is laid next to high-voltage lines, moisture in Kevlar will become a current conductor and, as a result, cause damage to the cable.

Outer sheath and cable

To cut the outer sheath, we use a stripper knife - either a standard one for fiber optics, or one that is used to cut a power cable. We set the desired thickness of the cut, fix the knife on the cable and turn it around the axis several times (5-10). It turns out a circular cut. Now we make two longitudinal ones from it in the direction of the end of the cable - and the sheath breaks into 2 halves.

Important:

The thickness of the cut must be exactly set.. If it turns out to be too deep, there is a risk of cutting the optical fibers, or dulling the knife blade on the armor. The most unpleasant thing that can happen here is that after welding and finishing the installation into the sleeve, you will find that one of the fibers jumped out of the cable, because. was damaged by cutting. If the incision is small, you will have to spend time to tear off the shell.
When working with different types of cables, always try a cut on the tip of a new cable.- to check if the cut thickness is set correctly.

The cable for suspension in cables of the "eight" type is cut with cable cutters, its sheath is separated from the main sheath of the cable with a knife.

Cutting armor, corrugated armor and Kevlar

Depending on the type of coupling, the Kevlar, corrugated or wire armor may need to be cut out incompletely, leaving some part for fastening. Also, armor and corrugated armor can be used to ground the cable - you will also need to leave a small segment.

Booking type	How to butcher
Armor with steel wires.	It is best to bite out such armor with cable cutters, 3-4 rods each. You can use side cutters, but in this case more effort and time is spent.
Armor with corrugated steel tape	Cutting requires special care, because. corrugated armor dented under the tool or its sharp edges can damage the modules, including the optical fiber. As a standard, it is cut lengthwise with a plow knife (the knife must be taken reinforced).
Kevlar armor	It is better not to cut Kevlar with ordinary cutting tools - it quickly becomes dull. Kevlar shears should have ceramic pads. Or we use wire cutters.

Inner shells and hydrophobic impregnation

To cut the inner sheath (not all cables have it), use:

Ordinary dummy knife (requires good experience and skill, because there is a high risk of damaging modules with fiber optics);
The same stripper knife as for the outer sheath, but set to a different cut thickness. We act very accurately and accurately, because fiber is getting closer;
Clothespin stripper.

It is best to keep two stripper knives on hand - one set to the outer sheath of the cable, the other for a thinner cut of the inner sheath.

Now the installer is left with modules with fiber optics, covered with a film, interlacing of threads and hydrophobe (all this together, or in different combinations). We work with gloves, because hydrophobic lubricant is a very unpleasant liquid that is difficult to wash off your hands.

A thin film, if any, is easily cut with a knife;
The threads are removed manually or with a special hook, which is on some models of stripper knives;
We take napkins, D-Gel (“orange”) liquid - it can be replaced with gasoline (if we work outdoors) and carefully clean the modules from everything;
After general cleaning, we also clean each module separately, and then wipe it with alcohol.

Some use a faster and “cleaner” method: they do not cut the cable to the modules completely, having cleaned only a small area, from half a meter. On him bite the shells of the modules and pull everything together- modules, threads, film, etc. - like a stocking. However, while saving time, this method is fraught with damage to the fibers if the applied force is too great. This is especially dangerous in winter, when the hydrophobic lubricant thickens.

Dividing the modules

If the fiber optic cable is monotube and its module is made in the form of a hard plastic tube, a circular incision is made with a small pipe cutter and, carefully so as not to damage the fibers, the module is broken.

In the case of the presence of several modules, everything is more complicated. First, while you are working with one, you need to hold on to the others that are actively crawling under your arms. Secondly, the cable itself is on weight and it is not very convenient. It is best to do this work together.

We cut empty stub modules under the root. We bite modules with fiber optics with a special module stripper. Again, it is very important to choose the correct depth of cut, so what? That's right, an optical fiber in the immediate vicinity of the instrument.

Important:

The module stripper has a special pawl that blocks the reverse. It often happens that it works just at the moment of biting the module. You cannot open the stripper back, the only way to release the latch is to bite the module again, which is fraught with damage to the fibers. Therefore, the position of the latch dog must be monitored.
You can not pull the modules from the fibers with great force, this can damage them and affect the quality of communication in the future. It is better to release slowly, in parts.

Fiber cleaning

Fibers intended for installation and welding must be perfectly whole and perfectly clean. First, we wipe them in the following sequence:

Lint-free dry wipes - 3-4 pieces - remove the hydrophobe;
Lint-free wipes moistened with alcohol (ethyl, isopropyl).

Expensive wipes in practice are often replaced with high-quality toilet paper (unflavored).

The fibers are then carefully inspected for integrity. Even if the lacquer coating is damaged quite a bit - it is better to cut the cable again. The time investment will be much lower than if you have to come back here after a while and repeat the fiber optic cable splicing process from start to finish.

Sleeve mounting

Before inserting the fiber optic cable into the sleeve on it heat shrink must be worn(with the exception of those designs where the cable is fixed in raw rubber). This is a polyethylene tube, which, under the influence of high temperature, “shrinks” and tightly wraps around the cable and the coupling pipe. This seals the cable entry. In addition, this is an additional fixation element.

Shrinkage is done after completion of work, tk. if something goes wrong during welding, there will be no need to waste time removing the frozen film.

Shrinkage can be carried out with a blowtorch, building hair dryer or gas burner. In practice, it is very convenient to use the design of a tourist gas canister and a small burner.

cable laying in the ground (“manually” in a trench; trenchless, with the help of knife cable layers; in polyethylene pipes laid in the ground);

laying in a cable duct (in a cable duct; along protective pipes laid in a cable duct);

suspension of a cable with a power element on supports (power lines; lighting, urban transport, railway transport, etc.);

laying inside buildings and premises (internal laying);

laying through water barriers.

Laying fiber-optic cable in the ground. This is the most common way of laying FOCL in places where there is no cable duct. Unfortunately, this method is more expensive than overhead cable laying and takes more time. But the main advantage of such a communication line over others is its several times superiority in reliability.

The laying of fiber optic cable is carried out in soils of all categories, with the exception of soils subject to permafrost deformations.

Figure 2.3– Laying an optical cable with a cable layer

Laying fiber optic cable in cable ducts. The laying of optical communication cables in cable ducts is carried out both manually and mechanized using standard mechanisms and devices. At the same time, the following requirement must always be strictly observed: tensile strength, bending radius, temperature during installation and permissible compressive force must comply with the requirements of the specifications for the cable to be laid in order to avoid breakage and hidden damage to the fibers.

1 - cast iron covers; 2 - pipelines; 3 - cable; 4 - viewing wells; 5 - hatches

Figure 2.4– Cable duct