Russian communications corporations are increasingly introducing fiber optic solutions. This applies, in particular, to the B2C segment, in which Internet access services are provided to individuals. Citizens connected to fiber optics have the opportunity to access the Internet at the highest speeds—tens of megabits. Previously, such a speed was considered absolutely incredible. The introduction of fiber optic technologies can also significantly speed up business processes, and therefore active users of the corresponding solutions are becoming commercial enterprises. What are the specifics of fiber optic cables as a communication solution? How much does it cost to build the appropriate infrastructure?

Key benefits of fiber optics

Optical fiber as a technology has a number of advantages over traditional types of cables. Among them:

Resistance to interference, electromagnetic fields;

Higher throughput;

Light weight and easy to transport;

There is no need to ground the Sinhala transmitter and receiver;

No short circuits.

This type of cable is capable of transmitting signals over very long distances. Optical fiber as a resource for organizing wired communications has begun to be actively implemented in developed countries in the 70s. Now the level of penetration of relevant technologies in Russia is one of the most dynamic in Europe.

Let us now study the main types of fiber optic solutions.

Classification of fiber optic cables

Optical fiber can be used to build communication infrastructure:

Within telephone networks;

As part of intrazonal communications;

Within the backbone networks.

IN Lately Optical fiber is also used as a data transmission tool at the end sections of subscriber lines. Some experts classify the corresponding types of cables into a separate category. Previously, in such areas, as a rule, DSL solutions and twisted pair Ethernet cables were used. For the modern Internet access market, it is common practice for the subscriber to have a fiber-optic modem.

It can be noted that the market for communication solutions also includes hybrid types of cables that combine optical fiber and traditional materials.

Features of the practical implementation of fiber optic solutions

Trunk cables are used to transmit data over long distances. Designed for simultaneous connection large quantity subscriber Most often, when building such an infrastructure, single-mode optical fiber is used.

Intrazone cables are used primarily to provide multi-channel communications over distances within 250 km. Their structure most often involves fibers classified as gradient.

City cables are used to provide communication between telephone exchanges and various communication centers. Designed for data transmission within 10 km and broadcasting with a large number of channels. Urban fiber optic systems also typically use gradient fibers.

We noted above that single-mode fiber is most often used in backbone cable infrastructure. What is its specificity and difference from the other - multimode?

Singlemode and multimode cables

The term “fashion” in this case is technical. It denotes a set of light rays that form one or another interference structure. Modes of the lowest order are characterized by being directed toward the distribution surface at a large angle. Single-mode cables carry these in single quantities. In turn, multimode optical fiber is characterized by a larger optical fiber channel. This makes it possible to pass a large number of modes.

Advantages of single-mode cables

The main advantage of single-mode cables is that the signal level in them is usually more stable, and the data transfer speed for the same amount of resource is higher. The corresponding solutions also have disadvantages. In particular, single-mode cables require significantly more powerful, and therefore expensive, radiation sources than those used with multimode fibers.

Benefits of Multimode Fiber

In turn, cables of the second type, which are designed to transmit a large number of modes, are characterized primarily by less labor-intensive installation, since the size of the light-conducting channel in them is larger. Regarding the emitters above, we noted that for multimode wires they are usually cheaper. At the same time, fiber optic solutions of this type are poorly suited for use in backbone networks due to insufficiently high throughput.

Cable structure

Optical communication cables are designed simply. The basis of the corresponding elements is fibers made of light-conducting quartz glass. These components are enclosed in a protective shell. If necessary, the cable can be supplemented with other elements in order to give the structure greater strength. The optical fiber has a cylindrical shape. It is designed to transmit signals with a wavelength of 0.85-1.6 microns.

The optical fiber has a two-layer design. It contains a core and a cladding that have different refractive characteristics. The first component is used to transmit electromagnetic signals. The shell is designed to protect the channel from external interference, as well as provide optimal conditions for reflecting the light flux. The cable core is most often made of quartz. The shell in some cases can be polymer.

How is optical fiber made?

Let's look at how industrial fiber production is carried out.

Among the most common methods for producing the corresponding material is vapor deposition through a chemical reaction. This procedure is implemented in several stages. At the first stage, a quartz blank is made, at the second stage, a fiber is formed from it. This process involves the use of the following substances: chlorinated quartz, oxygen, pure quartz. The considered method of producing optical fiber is characterized, first of all, by the ability to ensure high chemical purity of the material. In some cases, gradient fibers with target characteristics refraction. They can be achieved through the use of various additives during the manufacture of optical fiber - titanium, phosphorus, germanium, boron.

Cable designs

So, we have studied the main characteristics of optical fibers and the features of their manufacture. Let us now consider options for the structural implementation of the corresponding cables.

The parameters that define the features of the respective configurations depend on the specific application of the fiber. With all the variety of design approaches, there are 3 main categories of cables:

Concentric twist;

With a shaped core;

Flat tape type.

Fiber optic cables of the first type have a structure generally similar to that typical for electrical cables. The number of fibers in such solutions is most often 7, 12 or 19. Cables of the second type therefore have a core - usually plastic, in which light-conducting channels are located. This type of optical cable contains 8 fibers, in some cases - 4, 6 or 10. Ribbon cables have in their structure, respectively, tapes that contain a certain amount of light-conducting channels. As a rule - 12, in some cases - 6 or 8. It can be noted that in some cases the indicator in question, which characterizes an optical cable, is 16 fibers. This characteristic may be determined by the standards adopted in the country in which the optical fiber is produced.

Specifics of laying fiber optic cables

Let us now study the main features that characterize the laying of optical fiber. Experts recommend adhering to the following basic rules when solving the corresponding problem:

It is necessary to ensure that the cable radius is greater than the minimum required for bending;

Avoid using channels or trays with sharp edges;

Cables should be laid on a flat surface;

If possible, avoid connecting cables at a 90-degree angle;

Avoid twisting the wire.

The minimum bending radius is usually specified in the cable specifications provided by the cable manufacturer. During installation, experts recommend adhering to the rule: optical fiber with a diameter of no more than 2 cm should not extend beyond the minimum radius, unless it exceeds 30 cm.

Cable management tools

To install the cables in question, you will need various instruments. Among these is an optical fiber cleaver. It is designed to prepare appropriate materials for welding. Its essence is in connecting the light-conducting elements of two different wires due to high-temperature treatment. Splicing optical fiber also requires the use of a special apparatus.

How much does it cost to implement fiber optics?

Previously, there was a popular point of view that the installation of fiber optic cables is not very profitable due to the high cost of the light-conducting media themselves, as well as the work on their installation. Such a thesis was probably relevant at that period of market development, when there was not expected to be a sufficiently high demand for appropriate communications. Now, as we noted above, optical fiber is no longer uncommon for ordinary subscribers of city networks.

But how much does it cost to implement the solutions in question? A lot depends on the specific types of wires. Moreover, the price set by the manufacturer for a particular fiber (optical cable) is a very superficial criterion for the costs associated with the implementation of the corresponding infrastructure. It is very important to consider this in combination with the labor costs and other resource requirements that are needed to lay a fiber optic network. Thus, we will try to estimate how much it will cost to implement the appropriate solutions, taking into account the total costs - not only for optical fiber, the price of which, as we noted above, can vary significantly, but also for attracting specialists to install cables and purchase other necessary infrastructure components , which is in question.

Above, we classified fiber optic solutions based on such a criterion as the scale of the networks. So, if we talk about trunk lines, then laying 1 km of optical fiber will cost approximately 100-150 thousand rubles. As for ensuring the functioning of the city communication center, the cost of solving this problem will be about 100 thousand rubles. Building a fiber-based distribution infrastructure for a single area will cost approximately 150 thousand rubles. One communication center designed to connect subscribers will cost approximately 30 thousand rubles. In turn, installation of equipment and cables for 100 subscriber lines will cost approximately 30 thousand rubles.

If the provider decides to provide equipment for free to its customers - in particular, fiber optic modems, then each of the corresponding devices will cost about 1000 rubles. Note that, due to the continued dependence of the Russian communications market on the import of optical fiber, the corresponding prices may change in correlation with the ruble exchange rate.

Thus, optical fiber in some cases may indeed require significant investment. However, as the number of subscribers increases, the corresponding investments will pay off. Many modern Russian providers are counting on this by upgrading traditional communication lines and introducing high-tech fiber optic solutions.

Basic advantages of aerial cable laying between buildings:

1. Ease and speed of installation (in contrast to underground cable laying, this type installation does not entail digging trenches, removing debris, etc.).
2. Availability (when laid underground, the length of the cable connecting buildings is longer than in the case of an air connection).
3. Speed ​​and minimization of repair costs in unforeseen situations.
4. Construction of an overhead line is a fairly budget option. This is because it requires almost no use complex technology, cranes, etc.

Disadvantages of air gasket:

1. Susceptibility to external disturbances (thunderstorm, rain, frost).
2. Possibility of damage from physical impact of other objects (friction).
3. The formation of cracks due to high humidity, which threatens to replace the line.
4. Short service life.

Overhead communication lines

Fig.1. Two buildings are connected by an overhead communication line (airline)

In the image:

1 – connection objects (usually residential buildings, offices, apartments),
2 – steel rope (wire, rod, support cable),
3 – telephone cable.

This is the most simple circuit what you need to get upon completion of installation work.

The use of twisted pair without a fixing metal rope is fraught with spoilage products. This is due to the fact that the telephone cable is not designed to withstand aggressive environmental influences (sharp gusts of wind, melted snow, icing). Ideally, the cable should be insulated. In normal cases (with a cable length of up to 80 m), the insulation diameter is 1 - 1.5 mm 2. The cable covering serves anti-corrosion protection. Otherwise, due to its small cross-section, the product will fail very soon (in a year).

The cable is installed by fixing it to solid protruding objects (reinforcement, masts). Here it is important to limit the contact of the cable with the fastening on each building. Differences in potential can lead to the fact that during the flow of current through a metal structure, when inducing a twisted pair cable, a short circuit may occur. Grounding the load protection cable is mandatory. In rare cases, grounding occurs unilaterally. Since the two-way method is more effective. In this case, it is necessary either to ground one side through a container, or to divide the steel rod into equal parts by inserting a fiberglass plate.

Overhead line via twisted pair

Network cable ( twisted pair), exposed to the realities of a harsh climate, is subject to very heavy stress. The twisted pair cable connecting houses suffers even more from the tasks assigned to it. The best choice for laying cables through the air would be to use a material designed for external tensioning. It is distinguished by appropriate technical characteristics. In the best case, the communication line is treated with a thermoactive polymer resin (compound) or coated with a special water-repellent paint (hydrophobic). The shielded cable is completely excluded from possible options. If there is a risk of a short circuit, such a shielded cable will not help solve the problem, and it is more expensive.

To ensure the protection of installations connected to the overhead line from all kinds of voltage surges, the ideal solution would be lightning protection. This is a special diode bridge that reacts to the potential difference between the protective cables and short-circuits them. It is also possible to drain excess static current into grounding.

At cable laying by air The communication line is attached to the protective conductor. It can be fixed with any dielectric that does not come into contact with the environment. It is believed that the optimal solution would be nylon ties. Using ties, the twisted pair is connected to the supporting cable at the connection points, at an interval of 50-70 cm. The cable should not be stretched in order to avoid a situation where the entire load is placed on it, and the cable does not perform its main function - the supporting one. The sagging of the twisted pair should be within reason (for clarity, Fig. 1 shows an incorrect installation option). The ties are pulled as tightly as possible to avoid any friction between the products. In case of excessive constriction, damage to the cable structure may occur (the fastening system must have a flat surface and its width is at least 5-7 mm).

Cable laying over the air

Necessary materials:

• optical fiber
• support wire
• clamps (ties).

The cable must correspond to size b+l, where l is the additional length designed for loosening and fastening (Fig. 2).

Fig.2. Schematic plan of the air

1. Unwinding the cable on the roof of the first building.
2. Measure the required distance over which the air will be laid from point A to the equipment installation site (under normal conditions, you can make a calculation with a margin). You need to mark point A on the unwound cable. Find the corresponding mark on the wire (having previously measured the distance from the fastening to point A, and marking it on the cable). The cable is laid parallel to the cable (point A of the cable to point A of the wire).
3. Measure the length (a+d) from point A of building 1 on a metal wire (d are measurement errors that are caused by sagging and distance from the edge of points A - objects 1 and 2).
4. Over a given length, it is necessary to distribute the screeds evenly. Person 1 and person 3 fix the position of the cable (Fig. 3), person 2 secures it. The cable should not hang much lower than the cable.

Fig.3. Cable to cable fastening technology

We can assume that the preparation of the air system for installation has come to an end. Part of the unused cable, which is intended for 2 objects, is carefully rolled into a coil and fixed with tape to the wire (so it will not cause discomfort during installation work).

The last iteration of stretching is performed using the following methods:

• The cable can be pulled below and stretched from 1 object.
• Make a shot between the roofs of two buildings by throwing a dart with a fishing line (you can use a crossbow or a gas gun), where the end of the air gun is fixed on one roof. Next, you should pull the product from roof 2 using the attached fishing line.

Method No. 1: cable stretching method

Having 2 “buffer” cables (a thin rope, a dense thread that will support the weight of the structure), the first end of the wire is attached to 1 roof, and the second to a nylon thread or rope 1, after which it is lowered down along the building (Fig. 4 ). Then you need to move the end of the rope to object 2 (taking into account obstacles in the form of vegetation or other high ledges).

The end of the rope 2 is lowered from the roof 2. The ends of the products are tied together and lifted to the 2nd object. In general, now the main task is to control the quality of the process of tightening the end of the rope with the coiled cable to the 2nd object. Now the wire is stretched, of course, with an acceptable sag. The wire is firmly fixed to the 2nd object, then the cable is laid and the wire is grounded.

Rice. 4 First method

Method No. 2: stretch method

From roof 2 in the direction of roof 1, the layer launches a dart with a fishing line attached using a weapon. It is taken by the installer, who is located on 1 roof. Layer 1 fixes the line to a specially prepared cable, and the installer on roof 2, following an approving signal from installer on roof 1, pulls the cable towards himself (Fig. 5).

Fig.5. The second method of tensioning an optical cable when laying it through the air

To implement the latter method, an ultrasonic design model is often used, called the Laserline air gun.

Key features of the Laserline cable management gun:

• The weapon is equipped with a laser, which simplifies the aiming process.
• The size of the fishing line wound on the reel is 465 m, which means you can make shots over long distances.
• The maximum line reach is 40m.
• The gun comes complete with gas cylinders refilled with CO2 (Fig. 6)
• For convenience, you can stock up on a set of darts for it.

Attention! Before use, you must read the instructions.

The Tekhkabelsystems LLC company supplies optical fiber, optical couplings, fittings and tools for laying optical cables over the air (between supports, buildings). The price of products is indicated in the product cards or available upon request. From this article you will learn how to stretch and lay a cable over the air: installation methods, fastening conditions, cost of work and rules for handling products.

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Before you begin laying a cable in the ground, it is necessary to conduct a series of surveys along the route, which will help you choose the optimal design of the optical cable and technology for installation: in a trench, with a cable laying machine, using blasting or inclined drilling. When choosing, they take into account whether there are underground structures along the route: communication cables, pipelines, etc. They also check whether there are ground obstacles: railways and highways, forests, rivers, ravines, swamps, power lines, etc. In addition, during surveys determine where regeneration points, access points to OK, and optical couplings will be located.

The most economical method of laying cables in the ground is considered to be laying with a cable laying machine - it provides high speed gaskets and degree of mechanization. If the route intersects with a railway or highway, ravines, swamps, rocky areas and rivers, other laying methods can be used. If, when choosing a fiber optic cable, you choose a cable with armored metal covers, then you must comply with safety requirements to protect it from lightning, from the influence of power lines and electrified railways. On sections of the route that are the most dangerous in terms of emerging electromagnetic phenomena, the use of all-dielectric fiber optic cable should be considered.

Laying the cable directly into the ground using a cable laying machine must ensure smooth passage of the optical cable through the cable cutter cassette while observing the permitted cable bending radius and maintaining the laying depth (1.2 m). Cable layers are used on long and straight sections of the route, if there are no frequent intersections with any underground utilities.

Before starting laying, the soil must be cut (cut) in advance with a cable cutter, without inserting the cable. You can also do this procedure using a soil ripper. Many cable laying machines are equipped with soil breakers (loosening agents), including vibrators, which allows the required traction force to be reduced by half. If the soil on the route is rocky and heavy, then the digging is carried out in several passes until the full depth of the route is reached.

The laying is carried out evenly - without reducing or increasing the speed; the bottom of the slot should be smoothed evenly with a cable knife, to avoid possible mechanical damage to the optical fiber by stones or other protruding objects. You should also avoid sharp bends in the optical cable. The angle of the cable laying knife should not change. Constant monitoring of the depth of the fiber optic cable is required. When laying, it is unacceptable to exceed the permissible tensile force of the optical cable.

The permitted bending radius of the fiber optic cable must be constant; if the turn of the route is steeper than the cable layer can handle, then a trench should be dug to perform the maneuver. The deepening and deepening of the cable laying knife must be done exclusively in a pre-opened pit, and the size of the pit must exceed the maximum width of the knife. It is recommended that, simultaneously with laying the optical cable, 100 - 150 mm above its laying level, lay a warning tape, as well as install electronic markers at the intersections of the route with underground structures and at its turns.

When laying optical cables at intersections with cables, pipelines, etc., measures should be taken to prevent damage to existing structures.

In places where construction lengths will be joined, it is necessary to provide a technological margin in length, which will allow installation of the optical cable in a specialized installation vehicle (the margin must be at least 10 m). After the cable is installed, the length reserve (rolled up without violating the permitted bending radius) and the assembled cable is laid to the depth of installation in the ground, protected from mechanical influences. To ensure protection, the cable and coupling are covered with durable materials before being covered with soil (it is possible to place the coupling and a supply of optical cable in a small-sized access point).

An optical cable is laid in a trench if the route has multiple intersections with various obstacles or underground utilities or if there is a danger of damaging drainage devices with a cable-laying knife. Trenches can be developed with single-bucket and chain excavators, trenchers, and, in cramped conditions, with entrenching tools (manually). When developing a trench, it should be taken into account that the resulting depth will decrease by 50 - 100 mm due to the addition of loose soil or sand, which ensures leveling of the bottom and allows organizing smooth transition through inclusions that cannot be removed. After laying the optical cable in the trench, it is covered with a layer (100 - 150 mm) of sand or loose soil, on top of which a signal tape is laid. After this, the trench is filled with the excavated soil and compacted.

If the route crosses a railway or highway, the optical cable is laid using controlled drilling or horizontal puncture, using protective pipes.

If the optical cable route passes through a water barrier, then it is necessary to provide for the construction of two sections (transition sections), which are spaced 300 meters from each other. If there is a bridge at the location of the planned river crossing, then the lower section of the fiber optic cable is laid along the bridge. The river crossing section will be connected by coupling connections to a cable laid in the ground on the coastal sections. In order to ensure the most convenient access to couplings, it is recommended to place the OK technological stock and the couplings themselves at an access point (type POD).

If the water barrier is a navigable river, or the route passes through a significant number of underground communications, or through a large ravine, then horizontal inclined drilling techniques will be used. This method allows you to make hidden passages at a distance of up to one kilometer and a depth of up to 30 m, while ensuring high accuracy. Accuracy is achieved by preliminary drilling (pilot well) of small diameters with an exact exit on the opposite side of the obstacle, after which the well is expanded in several stages to the required diameter. Using drilling fluid, which forms a channel and acts as a lubricant, single pipes or bundles of them are pulled through the well, organizing cable ducting in the transition area.

Fiber optic cable routes are marked with picket posts, warning signs, and cable routes are linked on the working documentation to local facilities located permanently, using electronic markers and geostationary positioning systems.

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

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

laying in a cable duct (in a cable duct; through 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.);

installation inside buildings and premises (in-site installation);

laying through water barriers.

The construction of fiber-optic lines is considered a very complex production process. In particular, each installation of a main line, depending on the conditions of use (in the ground or on supports), requires correct and quality choice a certain type of cable. Of no small importance is the experience of handling optical fiber and the qualifications of a specialist, without which high-quality installation and connection of the system will simply be impossible. Even installing 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 method of laying fiber-optic lines 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.

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

Laying an optical cable in the ground should be carried out at an ambient temperature not lower than -10° C. At lower temperatures (but not lower than -30° C), the cable must be kept for two days in a heated room and it must be heated on a drum immediately before installation.

Laying fiber optic lines in open ground involves the use of 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 areas close to hazardous objects). In some cases, for example, when laying a fiber optic cable in close proximity to power lines (along railways), it is recommended to use an optical cable without metal elements. At the same time, 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 ways to lay fiber optic cable in the ground: either laying the cable in a trench (trench method), or using a trenchless method using cable laying machines or horizontal directional drilling units.

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

The disadvantage of this method is its labor intensity and low productivity. As a rule, the trench method is used when the terrain conditions make it impossible to use a cable laying machine. The trench is constructed using machinery (excavator, milling cutter) or manually if the cable route runs in places where it is not possible or prohibited to use heavy equipment. The cable is laid on a prepared pad at the bottom of the trench. When the route crosses various obstacles, the cable under them is laid in a pre-laid polyethylene pipe, which also helps protect the cable in difficult sections of the route from the influence of an external aggressive environment and from mechanical damage by rodents. Backfilling of the trench is carried out with excavated soil manually or using mechanisms in layers (the thickness of each layer is 200 mm) with warning tape placed in the trench.

The most common and economical method of trenchless installation of fiber optic lines is laying an armored cable into the ground using a knife cable layer due to the high speed of the mechanized process and a fairly high installation speed (Figure 2.3). It is applicable only on lines of relatively short length (no more than 100 km). This technology is mainly used in the presence of smoothly changing terrain and relatively simple 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 the work involves cutting a narrow slot in the ground with a cable layer and laying the cable at the bottom. Laying in the ground is carried out according to a specially developed scheme for fiber optic cables, 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 occurs along the path of its movement from the drum to the exit from the cable guide cassette, forced rotation of the drum is created and the cassette of the cable-laying knife is not allowed to become clogged when laying the cable in the ground. The laying process is continuously monitored, implying compliance with the following technological parameters: constant laying speed; constant tilt of the cable laying machine; elimination of sharp cable bends; preventing the permissible stretch of the fiber optic cable from being exceeded.

Figure 2.3– Laying the optical cable using a cable laying machine

In some areas it is possible to combine technologies. At crossings of roads, railways, as well as rivers, ravines and swamps, horizontal directional drilling is used. In these areas, the cable is laid in laid pipes.

With any method of laying a cable directly into the ground, pits are torn off at the junction of construction lengths to accommodate optical couplings and a supply of optics. The reserve should ensure the possibility of supplying the coupling to an area convenient for organizing the installers’ workplace. 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, grounding wires connected to the armor are brought out from the couplings into the container of grounding wires. Using jumpers, you can connect the armor of a fiber optic cable into the container, and if necessary, remove the jumpers and measure the insulation resistance.

Laying fiber optic cable in cable duct. Laying of optical communication cables in cable ducts is carried out both manually and mechanized using standard mechanisms and devices. In this case, it is always necessary to strictly observe the following requirement: the tensile strength, bending radius, temperature during installation and permissible compressive force must comply with the requirements of the technical specifications for the cable being laid in order to avoid rupture and hidden damage to the fibers.

Cable sewerage consists of a pipeline and wells (Figure 2.4). The cable is laid in the cable duct, and possible connections are made in cable wells or cable shafts. Inspection wells have hatches. The entire sewer system is located underground, and only inspection well hatches are brought to the surface, closed with cast-iron covers, under which there are steel locking covers.

Before laying a cable in a cable duct, a check is made for the permeability 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 – inspection wells; 5 – hatches

Figure 2.4– Cable duct

Installation in cable ducts is carried out mainly by manual tightening or using winches. When laying optical fiber in protective pipes, it is possible to use the push method.

Laying is carried out taking into account the following factors:

turning the route by an angle of 90° is equivalent to increasing 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 amount of traction force normalized for a specific OK;

to avoid damage to plastic cable ducts, a synthetic traction halyard (nylon, polypropylene) is used;

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

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

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

In difficult sections of the route and in the presence of large construction lengths of the cable, it is laid in two directions from one of the transit wells (preferably corner), located approximately a third of the length of the route. 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.

Construction lengths of optical cable are connected using feed-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 design documentation.

When tightening an 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 to the console with cable ties. The place where the optical cable enters the cable well is sealed with a passage gland to prevent silting or flooding of the channels in the spring. In the end wells, sufficient cable reserve is left for the installation of optical couplings with the removal of the cable to a specialized vehicle (optical laboratory), in which optical measurement and fiber welding are carried out.

Fiber optic cable suspension. FOC suspension options have a number of advantages compared to other construction methods: no need for land acquisition and approvals from interested organizations; reduction of construction time; reducing the amount of damage 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 simpler than laying in the ground.

To lay fiber-optic lines using the method of suspension to supports, they often use the suspension of a fiber-optic cable to a steel cable, which is stretched between supports on consoles. Fiber optic cable suspension with a built-in cable on specially designed consoles is also used.

When the fiber optic cable is suspended from a steel cable, each console is attached to a support using special screws. Taking into account the normal sag, 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 using hangers made of galvanized sheet steel. Such hangers must move freely along the steel cable and tightly enclose the fiber optic cable.

In the case of hanging a fiber optic cable that has a built-in support cable, standard fittings and a support clamp are used. Spiral clamps are used for tension fastening of a self-supporting fiber optic cable (reinstallation of spiral tension and support clamps is prohibited).

The most important difference between laying by hanging fiber-optic cables and other methods is that the splice points of two construction lengths must be located on a support along with a technological cable reserve sufficient for descent from the support, as well as for restoration work in case of emergency situations on the line . Splicing of building lengths of fiber optic cable is always done in an installation vehicle or tent. This necessitates the need to reserve larger lengths of technological reserve than when laying in the ground. In addition, it is necessary to pay attention to the reliable securing of the reserve, since being on a support is associated with constant exposure to wind loads

Laying fiber optic lines inside buildings, compared to other types of installation, the matter 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 lightweight, and the length of the routes is short, which greatly simplifies installation.

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

When constructing fiber-optic communication lines inside facility areas, a cable that has a fire safety certificate must be used. This 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 fiber optic lines through water obstacles(along the bottom) is the most expensive method 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 medium for laying the fiber-optic line changes (it was earth, but now it is water or air), the type of cable must also change accordingly. An optical coupling 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 hanging on supports above the river, or underwater, for laying fiber optic lines along the bottom of water obstacles. Technological cable reserves are organized at the locations of the couplings.

In railway transport, during the construction of fiber-optic lines, the most widely used methods are the suspension of fiber-optic cables on the supports of the electrified contact network. railways and high-voltage auto-blocking lines, as well as installation in pipelines. Due to the air suspension, capital costs for construction are reduced to 30% relative to its underground installation. At the same time, the construction time for fiber-optic lines is significantly reduced. At the same time, favorable conditions are provided for the inspection of 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 repairs.

The main advantage of aerial suspension of a fiber-optic cable is that virtually no preliminary preparation of the route is required, 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 construction time is significantly reduced.

However, hanging the cable on supports has some disadvantages. Thus, when laid 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 for railway transport, it is necessary to take into account the effects of external and internal destabilizing factors, as well as evaluate the measures taken by operational units to ensure reliable and stable operation of the communication network in real conditions environment and the adopted technical operation system.

Koloskov A. A., “The Cable Guy”, No. 1/2 (16)

Introduction

Fiber-optic communication lines (FOCL), due to a number of advantages and disadvantages (low attenuation, ultra-wideband, electromagnetic noise immunity, etc.) over traditional lines based on electrical cables, can provide a significant effect in the construction of new and modernization of existing cable communication systems. But no winnings or advantages are given for nothing. Fiber optic technology requires a more delicate attitude, greater knowledge and a high production culture.

The fiber-optic fragment in the structure of cable information transmission systems, among others, is designed to solve the problem of long distances, which is very important for vast Russia. With the steady decline in prices for fiber-optic equipment, including cable products, the laying and installation of optical cables is currently becoming widespread.

This article, which discusses simple but necessary things, is the result of summarizing the experience of the installation department of the Design and Installation Company Network LLC. The article is addressed not to “seasoned” specialists, but to young installation departments that have recently joined the large and motley family of “cable workers”.

Normative base

The construction and operation of fiber-optic lines is carried out in accordance with the requirements stipulated in the following regulatory documents:

1. Guidelines for the construction of linear structures of trunk and intrazonal cable communication lines. – Moscow, 1986

2. Guidelines for the construction of linear structures of local communication networks. M., JSC "SSKTB - TOMASS", 1995. Approved by the Ministry of Communications of Russia on December 21, 1995.

3. Guidelines for laying, installing and commissioning optical communication lines of the GTS. – Moscow, 1997

4. Manual for the operation of line-cable structures of local communication networks. M., UES of the State Committee for Communications of Russia, 1998. Approved by the State Committee for Communications of Russia on June 05, 1998.

5. Standards for acceptance and acceptance measurements of elementary cable sections of trunk and intrazonal underground fiber-optic transmission lines of a public communications network. Approved by order of the State Committee for Communications of Russia No. 97 dated December 17, 1997.

6. Regulations on the organization of electrical measurements during installation and commissioning of fiber-optic lines at the Moscow GTS. Approved by the management of JSC MGTS and JSC Mostelefonstroy in October 1995.

7. Installation and measurements of fiber-optic communication lines. A manual for fiber optic line meters and installers. OJSC "Mostelefonstroy" 1999

8. GOST 25462-82. Fiber optics. Terms and Definitions.

9. GOST 26599-85. VOSP components. Terms and Definitions.

It will be very useful to familiarize yourself with the modern Technical Specifications (TS) for fiber-optic cables from leading manufacturers.

Features of the construction of fiber-optic communication lines

The main stages of construction of communication lines on electrical and optical cables are the same. This makes it possible to widely use well-known techniques and mechanisms in the process of building fiber-optic lines.

Differences in construction technology, installation work and operation of fiber-optic lines are determined by the following design features of the optical cable (OC):

Relatively low resistance to tensile and compressive forces;

Small transverse dimensions and weight in combination with large construction lengths;

Relatively large attenuation values ​​of optical fiber (OF) splices;

Difficulties in organizing official communications;

The need to spend large amounts of time on fusion operations, as well as increased requirements for personnel qualifications.

The fundamental point is to ensure the least stressful conditions possible when laying the casing. The physical limitations recommended by the manufacturer must be strictly followed.

IN general view The process of laying OK consists of two stages: preparatory and main (the laying itself).

The preparatory stage includes incoming inspection of construction lengths. Incoming inspection of construction lengths consists of external inspection of the cable and measurement of its optical characteristics. Drums with OK are subjected to external inspection for the absence of mechanical damage. After opening the drum casing, the presence of factory passports and compliance with the markings are checked construction length specified in the passport, markings indicated on the drum, as well as the external condition of the cable for the absence of dents, cuts, pinches, twists, etc.

When measuring optical characteristics, first of all, the kilometer attenuation of the optical device is determined, i.e., its OF, and the results are compared with the passport data. In case of unsatisfactory results of the incoming inspection, a report is drawn up against which a complaint is made.

Pulling cables in the sewer

Fiber optic cable outside buildings within populated areas is laid in most cases in telephone sewers. It is based on round pipes with an internal diameter of 100 mm made of asbestos cement, concrete or plastic. Telephone sewerage is laid at a depth of 0.4 to 1.5 m from separate blocks hermetically joined together. After 40-100 m, inspection wells are placed on the route, on the walls of which consoles for cable laying are mounted. The difference between the technology for laying electrical and optical cables in telephone ducts is that the pulling force of the latter should not exceed the permissible value, and cable torsion is not allowed.

Cable laying in a telephone sewer is usually carried out in a free channel, where during construction a wire is left for pulling. In its absence, the passage of channels is carried out using a channel preparation device, which is an elastic fiberglass rod with a diameter of 10 mm and a length of up to 150 m, wound on a drum with a diameter of about 1 m. The rod is pushed into the channel to the adjacent well. Next, attach the end of the cable to the tip of the rod and pull it back. For fastening, you need to use a special tip, which is fixed on the cable by its strength element and armor covers and must be equipped with a torsion compensator. Pulling should be done smoothly and without jerking.

If there are sharp turns on the route, a rotary roller is installed in the well. In its absence, the cable is pulled out of this well in a loop, and further installation is carried out as from the starting point of the route. Often, to save construction time, the cable is sorted by hand directly in the well, directed into the sewer pipe.

Cable laying in buildings

Laying OK is usually not very difficult, both because of the short length of the route and because of the lighter and more flexible design of the intra-facility cable used for this. In the case of installation in pipe distribution, under a false floor and behind a false ceiling, the cable is first unrolled from the transport drum and laid out in a loop or figure eight at the starting point of the route, and then smoothly pulled into the cable channel. To facilitate the work, steel broaching wire 5-10 m long can be used.

When laying cables on open cable racks or in gutters in long corridors, it is more convenient to lay the cable on the floor along the route, and then lift it onto the gutter and fix it with plastic clamps every 2-3 m.

In non-residential attics and technical floors of buildings (if they are through), it is very convenient to hang the cable using standard metal hangers on a pre-tensioned support cable. In this case, complex strength calculations taking into account wind and ice loads are usually not required. The same method can be recommended when laying cables through basements and technical undergrounds of buildings in the absence of existing cable channels.

Air cable suspension

OK suspension options have a number of advantages compared to other construction methods:

No need for land allocation and approvals from interested organizations;

Reducing construction time;

Reducing the amount of possible damage in urban areas and industrial zones;

Reduced capital and operating costs;

Independence from types of soils and soils.

However, there are also disadvantages of air laying:

Shorter service life due to environmental influences;

Susceptibility to increased mechanical stress in adverse weather conditions;

Unaesthetic;

Complexity of calculations when exposed to loads under all operating conditions.

For the construction of fiber-optic lines using the suspension method in populated areas, the OK suspension to a steel cable stretched between supports on consoles, as well as the OK suspension with a built-in cable on specially designed consoles, are widely used. When hanging the OK from a steel cable, each console is attached to the support with special screws. The installation height of the consoles (taking into account the normal sag) must be such that the clearance from the ground to the lowest point of the cable is at least 4.5 m. The OK is attached to the cable using hangers made of galvanized sheet steel. The hangers must tightly encircle the cable and move freely along the steel cable.

When suspending OK with a built-in support cable, standard power supply fittings of the KGP type and a supporting clamp PSO-14-03 are used. For tension fastening of a self-supporting OK, a spiral clamp of the NSO-14P-02 brand is used. The fastening of this clamp to the support is carried out through the thimble supplied with the clamp and the linear coupling fittings. Re-installation of the spiral support and tension clamps is prohibited.

The figures below show the fittings for tension and support fastenings OK on supports of a circular cross-section.

Schemes for fastening non-self-supporting dielectric OC on round supports

Rice. 1 Tension fastening diagrams OK

Rice. 2 Schemes of supporting fastening OK

Schemes for fastening a self-supporting dielectric OC on round supports

Rice. 3 Scheme of tension fastening of a self-supporting OK

Rice. 4 Scheme of supporting fastening of a self-supporting OK

As mentioned above, the disadvantages of the OK air suspension include the difficulty of calculating all the loads acting on the air-cable transition (ACT). The calculation of the supporting cable includes the calculation of the actual tension force under operating conditions, which should not exceed the ultimate tensile strength of the cable, and the calculation of the required length of the cable. The ultimate tensile strength of the cable and its specific gravity can be found in technical documentation manufacturer. When calculating the cable tension, it is necessary to take into account all components of the load that can affect its stretching in real conditions, i.e., calculate its total weight load. In the worst case, the cable stretches under the influence of its own weight, the weight of the cable and fastening structure, and the weight of freezing ice (the vertical component of the load). In addition, the load on the cable increases under the influence of wind force (horizontal component of the load). The required length of the cable must be calculated taking into account the sag, which changes depending on temperature fluctuations and tension force.

As practice shows, the reliability of cable laying on a suspension can be guaranteed when using a cable whose tension does not exceed 60% of its ultimate tensile strength (in all operating conditions). The issues and methodology for fully calculating aerial-cable transitions are quite complex and are not presented in this article. Some formulas and considerations are presented in an accessible and understandable form in.

Optical cable cutting

Cutting an optical cable includes the steps of removing the outer covers and cutting the core.

In the process of cutting an optical cable, armor coverings, protective shells are removed and light guides are prepared for installation of connectors or splicing by welding. During cutting, the cable must be firmly fixed on the mounting table with a clamp, clock vice or plastic tie.

The purpose of cutting is to prepare the light guides for welding or installation of connectors. The cutting length is usually about 1 m when using welded technology.

Removal of the outer protective hose begins by making a circular cut on its shell. The distance from the edge of the cable to the cut point should be equal to the cutting length. The protective hose is then cut longitudinally using a breaking thread or a knife. If there is no breaking thread in the cable design, the use of a special cable knife with a self-orienting or rotary cutter gives a good effect.

The internal protective hose is removed from the cable core in the same way as the external one using a breaking thread, a regular or cable knife. The core elements are unraveled, the end of the cable is firmly fixed on the mounting table with a clock vice, cable ties or a clamp. The threads of the reinforcing Kevlar winding are cut off with scissors, the reinforcing elements are removed with side cutters, the central power steel rope cut with wire cutters or sawed with a hacksaw.

To remove module tubes, a stripper or a special ring knife is used. A circular cut is made on the sheath with a tool, then the tube is removed from the fiber using a smooth, constant pulling force. To reduce the forces acting on the fibers, the module tubes are removed in several stages.

After removing the module's protective tube, the fibers are cleaned of the hydrophobic gel with a rag or napkin soaked in a special cleaning liquid or alcohol. The processed fiber is set aside. Then they begin cutting the next module.

The completely cut cable is inserted into the switching and cutting device, and after being fixed in it, it is ready for further work.

Basic safety rules when working with fiber optic devices

When working with optical cable and other fiber-optic equipment, you must:

1. Under no circumstances should you look into the end of the optical fiber or optical transmitter connector. The radiation transmitted through the light guide is outside the visible wavelength range, but can lead to irreversible damage to the retina.

2. Avoid getting optical fiber scraps generated during connector installation and fiber splicing on clothing or skin. These trimmings should be collected in tightly sealed containers or with sticky tape. When working with fiber, it is necessary to wear safety glasses.

3. While working with optical fiber, eating is strictly prohibited, and after work you must wash your hands with soap.

4. Please be aware that alcohol and solvents used to remove protective coatings are flammable and burn with a colorless flame and may be toxic and cause an allergic reaction.

5. Welding machines use high voltage to form an electric arc, which is dangerous to life, and the arc discharge between the electrodes can lead to the ignition of flammable gases and vapors of flammable liquids.

6. Smoking while working with fiber optics can lead to a sharp decrease in the quality of the weld or the manufactured connector.

Useful tips (extract from Technical specifications for optical communication cables, section: Installation and operation instructions):

The cables are intended for laying (installation) at a temperature not lower than minus 10° C;

The bending radius of the cable during installation (installation) must be at least 20 nominal outer diameters of the cable;

When installing the cable, the permissible tensile and crushing loads, as well as other mechanical characteristics, the values ​​of which are specified in the Technical Specifications, must not be exceeded;

The permissible static bending radius of optical modules is at least 40 mm;

The permissible bending radius of the optical fiber during installation is at least 3 mm (within 10 minutes);

Organizations carrying out cable laying and installation must have a valid certificate authorizing them to carry out the relevant construction and installation work.

When laying (installing) and operating cables intended for suspension on overhead communication lines, the following special requirements must be observed:

When unwinding the cable during installation, the cable must not touch any objects, with the exception of rotating rollers;

The radius of the mounting rollers installed on the first support must be at least 20 nominal outer diameters of the cable;

During the process of laying the boom, the sag should be greater than the design values. Installation of the design sag booms should be carried out at the final tension of the cable;

The technical characteristics of the suspension fittings must be agreed with the cable manufacturer;

During operation, the cables must be protected by vibration absorbers from vibration that occurs under wind load.

BIBLIOGRAPHY:

1. A. B. Semenov, “Fiber optics in local and corporate networks connections." – Computer press, Moscow, 1998

2. R. Freeman, “Fiber Optic Communication Systems.” – Moscow: Tekhnosphere, 2003. – 440 p.

3. “Fiber-optic communication systems on GTS.” – Directory. Ed. A. S. Briskera, A. N. Golubeva. – M.: “Radio and Communications”, 1994.

4. "Fiber optic technology: Current state and prospects." – 2nd ed., revised. and additional / Sat. articles edited by Dmitrieva S. A. and Slepova N. N. - M.: Fiber Optical Equipment LLC, 2005 - 576 p.

5. Z. A. Zima, I. A. Kolpakov, A. A. Romanov, M. F. Tyukhin, “Cable television systems.” – Publishing house of MSTU im. N. E. Bauman, Moscow, 2004

6. S.V. Volkov, “Cable TV networks.” – M.: Hotline-Telecom, 2004 – 616 p.

7. “TFC cables. Methodology for calculating cable tension during aerial laying.” – J-l TELE-Sputnik, February 2000