How to lay fiber-optic cable between buildings. Laying the fibers in the ground (in the ground). The scope of the wols

There is no one universal technology for cutting fiber-optic cable for installation. Each coupling has its own specifics, which is stipulated in the instructions for it. It may be necessary to completely cut off the Kevlar threads or, on the contrary, leave and clamp them in the mount, cut 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, not to make them too short. Otherwise, there will be difficulties during installation.

Moreover, each stage of cable stripping 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 solders.

Fiber Optic Cutting Tools

The main arsenal of an installer-splitter of fiber-optic networks for cable cutting:

• Stripper knife;
• Clothespin stripper;
• D-Gel hydrophobic lubricant solvent;
• Pliers;
• Dummy knife.

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

Cutting and installation of 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 waterproofing the end is cut off and discard about 1 meter of cable... Fiber optic and other structural elements lose their qualities with prolonged exposure to moisture.

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

Outer sheath and rope

To cut the outer sheath, we use a stripper knife - either a standard one for optical fiber, or the one 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 towards the end of the cable - and the sheath splits into 2 halves.

Important:

• The thickness of the cut must be exactly... If it turns out to be too deep, there is a risk of cutting the optical fibers, or blunting the knife blade against the armor. The most unpleasant thing that can be here - after welding and completion of installation in the sleeve, find that one of the fibers has jumped out of the cable, because was damaged when cut. If the incision is small, you will have to spend time to peel off the shell.
• When working with different types of cables, always try the cut at the end of the new cable.- to check if the cut thickness is set correctly.

The cable for suspension in “figure-eight” cables is cut with ropes, its sheath is separated from the main sheath of the cable with a knife.

Cutting of armor, corrugated armor and kevlar

Depending on the type of Kevlar coupling, corrugated armor or wire armor may need to be cut partially, 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.

Inner shells and hydrophobic impregnation

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

• Regular breadboard knife (required good experience and skill, because there is a high risk of damage to modules with fiber optic);
• The same stripping knife as for the outer casing, but set to a different cut thickness. We act very accurately and accurately, because optical fiber is getting closer;
• Clothespin stripper.

It is best to keep two stripping knives close at hand - one with settings for 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 optic, covered on top with a film, interlacing of threads and a hydrophobe (all this together, or in different combinations). We work with gloves since hydrophobic lubricant is a very unpleasant liquid that is difficult to wash off the hands.

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

Some people use a faster and "cleaner" method: they do not cut the cable to the modules completely, clearing only a small area, about half a meter. On him bite the shells of the modules and pull everything together- modules, threads, film, etc. - like a stocking. However, for all the time savings, this method is fraught with fiber damage if the applied force is too great. This is especially dangerous in winter, when the hydrophobic grease thickens.

Splitting modules

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

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 rest, which are actively climbing under your arms. Secondly, the cable itself is hanging and it is not very convenient. It is best to do this work together.

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

Important:

• On the stripper of the modules there is a special pawl that blocks the reverse movement. It often happens that it is triggered 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 could damage the fibers. Therefore, the position of the locking pawl must be monitored.
• Do not pull the modules off the fibers with great force, this can damage them and affect the quality of communication in the future. Better to release slowly, in parts.

Fiber cleaning

Fibers intended for installation and welding should 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).

In practice, expensive napkins are often replaced with quality toilet paper (unscented).

Then the fibers are carefully examined for integrity. Even if the varnish is very slightly damaged - better to cut the cable again... The time required will be much lower than if you have to come back here after a while and repeat the process of welding the fiber optic cable from start to finish.

Coupling installation

Before inserting the fiber optic cable into the sleeve on it shrinking must be worn(except for those constructions where the cable is fixed in wet rubber). This is a polyethylene tube, which, under the influence of high temperature, "shrinks" and tightly wraps around the cable and the sleeve of the coupling. This seals the cable entry. In addition, it is an additional fixing element.

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

Shrinking can be done with a blowtorch, blow dryer or gas torch. In practice, it is very convenient to use the structure of a tourist gas canister and a small burner.

Russian communications corporations are increasingly introducing fiber-optic solutions. This applies, in particular, to the B2C segment, in which Internet access services are provided for individuals. Citizens who connect to the "fiber" get the opportunity to access the Internet at the most high speeds- tens of megabits. Previously, this speed was considered completely incredible. The introduction of fiber-optic technologies can significantly speed up business processes, and therefore become active users of the corresponding solutions commercial enterprises... What is the specificity of fiber optic cables as a communication solution? How much does it cost to build the appropriate infrastructure?

The main advantages of fiber

Optical fiber as a technology has several advantages over traditional cable types. Among those:

Immunity to interference, electromagnetic fields;

Higher throughput;

Light weight and ease of transportation;

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

No short circuits.

This type of cable is capable of transmitting a signal over very long distances. Optical fiber as a resource for organizing wired communications began 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 examine what are the main types of fiber optic solutions.

Fiber Optic Classification

Optical fiber can be used to build communication infrastructure:

Within telephone networks;

As part of intra-zone communications;

Within the backbone networks.

Recently, fiber has also been used as a tool for transmitting data at the end sections of subscriber lines. Some experts distinguish the corresponding types of cables into a separate category. Previously, in such areas, as a rule, DSL-solutions, Ethernet-cable of the "twisted pair" type were involved. For modern market Providing Internet access, it is a common practice for a subscriber to have a fiber-optic modem.

It can be noted that the communication solutions market also contains hybrid cable types that combine fiber and traditional materials.

Features of the practical implementation of fiber-optic solutions

Trunk cables are used to transfer data over long distances. Designed for the simultaneous connection of a large number of subscribers. Most often, when building such an infrastructure, single-mode optical fiber is used.

Intra-area cables are mainly used to provide multi-link communications over distances within 250 km. Most often fibers classified as gradient fibers are used in their structure.

City cables are used to provide communication between PBX and various communication centers. Designed for data transmission within 10 km and broadcasting with a large number of channels. In urban fiber-optic systems, as a rule, gradient fibers are also used.

Above, we noted that single-mode fiber is most often used in trunk cable infrastructure. What is its specificity and difference from another - 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. The lowest-order modes are characterized by high-angle directivity to the distribution surface. Those in a single quantity pass single-mode cables. In turn, multimode optical fiber has a larger fiber channel. This makes it possible to pass a large number of modes.

The advantages of singlemode cables

The main advantage of single-mode cables is that the signal level in them, as a rule, is more stable, and the data transfer rate is higher for the same amount of resource. The corresponding solutions also have disadvantages. In particular, singlemode 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 laborious installation, since the size of the light guide channel in them is larger. Regarding the emitters above, we noted that they are usually cheaper for multimode wires. At the same time, fiber-optic solutions of this type are poorly adapted for use in backbone networks due to insufficiently high bandwidth.

Cable structure

Optical communication cables are simple. The corresponding elements are based on fibers made of light-conducting quartz glass. These components are enclosed in a protective sheath. If necessary, the cable can be supplemented with other elements - in order to make the structure more robust. The optical fiber is cylindrical in shape. It is designed to transmit signals with a wavelength of 0.85-1.6 microns.

The optical fiber has a double layer construction. It contains a core, as well as a cladding, which 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 to provide optimal conditions for the reflection of the light flux. The core of the cable is most often made of quartz. In some cases, the shell can be polymeric.

How is fiber optic manufactured?

Let's consider how the industrial production of optical fiber is carried out.

The most common production method for the material involved is vapor deposition by chemical reaction. This procedure is implemented in several stages. At the first, a quartz blank is made, at the second, 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 provide high chemical purity of the material. In some cases, the manufacturer also produces gradient fibers with target characteristics refraction. They can be provided through the use of various additives - titanium, phosphorus, germanium, boron during the manufacture of optical fiber.

Cable constructions

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

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

Concentric stranding;

With a curly core;

Flat tape type.

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

Specificity of laying fiber-optic cables

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

Make sure that the radius of the cable is greater than the required minimum that is set for the bend;

The use of channels or trays with sharp edges should be avoided;

Lay cables on a flat surface;

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

Avoid twisting the wire.

The minimum bend radius is usually fixed at technical characteristics cable provided by its manufacturer. During installation, experts recommend adhering to the rule: optical fiber with a diameter of no more than 2 cm should not go beyond the minimum radius if it does not exceed 30 cm.

Tools for laying cables

Various tools are required to run the cables in question. Among them is an optical fiber cleaver. It is designed to prepare the appropriate materials for welding. Its essence is in the connection of light-conducting elements of two different wires due to high-temperature processing. Optical fiber splicing also requires the use of a special apparatus.

How much does it cost to deploy fiber?

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

But how much does it cost to implement the solutions in question? Much 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 of the costs associated with the implementation of the corresponding infrastructure. It is very important to consider it in conjunction with the labor and other resource requirements that are necessary for laying a fiber optic network. Thus, we will try to estimate how much the appropriate solutions will be implemented, 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. in question.

Above, we have 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 fiber optic will cost about 100-150 thousand rubles. As for ensuring the functioning of the city communication center, the cost of solving this problem will amount to about 100 thousand rubles. Building a distribution infrastructure based on fiber optic for a particular area will cost about 150 thousand rubles. One communication center, designed to connect subscribers, will cost about 30 thousand rubles. In turn, installation of equipment and cables for 100 subscriber lines will cost about 30 thousand rubles.

If the provider decides to provide equipment for its customers for free - 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 RF communications market on fiber imports, the corresponding prices may change in correlation with the ruble exchange rate.

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

Installation work for the laying of fiber-optic cable are carried out on the basis of project documentation and in compliance with regulatory requirements. The choice of the laying method is reflected and justified in the project. It must correspond to the type of cable, and the selected cable must correspond to the method and conditions of its installation.

There are four most common options:

1. Laying the cable into the ground.
2. Laying in cable ducts.
3. By air (cable suspension on poles, supports and building facades).
4. Internal laying (inside buildings).

Laying in the ground

Laying fiber optics in the ground is an affordable and reliable way of installing fiber-optic communication lines. This method is used everywhere, with the exception of soils prone to permafrost deformations.

The main options are:

• trenching method, in which the cable is laid directly in the ground (trench) and which is usually used when laying cables with a tape covering or protective armor;
• trenchless method using a cable layer.

It is permissible to use other methods of mechanized fiber-optic laying, but due to their high cost, they have not become widespread and are used when there are no less costly alternatives. Manual cable laying is used infrequently - in cases where there is no possibility of access for equipment and space to perform such work.

When constructing long-distance FOCLs (main FOCLs), the optimal solution is to lay a fiber-optic cable in protective polyethylene pipes (PPT). Due to the special technology of cable injection into the DCB and the presence of an inner layer of lubricant in the pipes, with this method of installation work, it is more convenient, easier and faster to lay long cables.

Installation in cable ducts

In cities and settlements installation of fiber optic cable underground is often carried out in cable ducts. For this purpose, both existing channels, for example, telephone channels, and new ones, specially laid pipes, are used. Which solution will be the best is determined based on the actual conditions and plans for the efficient operation of the sewer system.

Concrete, asbestos-cement or plastic pipes are used as cable ducts for the cable. The laying is carried out by the pulling method. The necessary operations to connect cable sections are performed in cable shafts or wells. The absence of earthworks with this method of fiber-optic communication installation reduces the cost of work.

Installation of fiber optic cable over the air

Laying FOCL through the air is usually advisable only if it is impossible to lay the cable in the ground or in a sewer. From the point of view of reliability, this method is inferior to the last two, but it reduces the labor intensity of the work and reduces costs.

For the installation of overhead lines used:

• cable laying along the supports (poles) of the existing power transmission line or communication line;
• optical cable in a lightning protection cable (installation or replacement of a cable);
• suspension of a self-supporting fiber-optic cable;
• winding a thin fiber on the phase (neutral) wire of the power transmission line.

Internal gasket

Laying of fiber-optic cable inside the building is used for the installation of intra-house, office and industrial fiber-optic communication lines. In these cases, the use of cables of light and flexible design is acceptable, but this factor will require reducing the angles of the line rotation and careful monitoring of compliance with the bending parameter. Installation work is simplified due to the possibility of using existing channels. Laying is carried out in the open (in basements, attics, technical rooms) and in a hidden way - behind false panels, ceilings or floors.

This is the most common way of laying fiber-optic communication lines in places where there is no cable duct. Unfortunately, this method is more expensive and time consuming than overhead cable laying. But such a communication line is several times superior to the latter in terms of reliability. There are two basic methods for laying fiber optic cable into the ground: either laying the cable in a trench (trench method), or using a trenchless method using cable layers or horizontal directional drilling rigs.

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 by rodents. The cable armor must be connected in couplings and grounded to protect the fiber-optic transmission systems from thunderstorms and the impact of power lines (especially in places of convergence with hazardous objects). In some cases, for example, in the case of laying a fiber-optic cable in the immediate vicinity of power lines (along railways), it is recommended to use a metal-free optical cable. 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 (see additional markers and marker finders).

The trench method of laying fiber-optic communication lines in the ground is most often used when installing a group of cables, while the width of the trench can be such that vehicle(tractor) can fit directly inside the trench. Cables are also laid in the ground 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 fiber-optic communication lines in the ground on cottage plots and lawns. The depth of cable laying in this way is not great, but at the same time it does not deteriorate appearance plots. The technology of cable installation in asphalt pavement is popular in Europe. The asphalt is cut with a special knife, similar to the one we use for road repairs. Further, a cable is laid in the resulting trench with a width of 19 to 32 mm and a depth of up to 305 mm. The cable can be protected either by a special box or by several layers of protective materials that are laid over it. A narrow and shallow trench allows fiber to pass through the ground over existing utilities, causing minimal damage to road infrastructure. After laying the cable, such trenches are filled with bitumen. This method is most widely used in Scandinavia. In our country, however, it has not found wide application, mainly due to the poor quality of the road surface.

It is possible to use the trench method of laying fiber-optic communication lines into the ground in the presence of many obstacles (nearby communications, drainage systems), but in this case, the "problem area" has, as a rule, to be passed manually.

The most common way of trenchless laying of fiber-optic communication lines is laying an armored cable into the ground using a knife cable layer. 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 in the near future a sharp increase in traffic requiring the laying of new cables is not expected. The route for laying armored cables into the ground is selected, as a rule, along roads of various purposes and categories, outside the right-of-way.

As for the laying of fiber-optic communication lines in the ground in ZPT (protective plastic pipes), this is the main method of laying cables in Europe. Today it is widely used in Russia as well. ZPT, made of high-strength polyethylene, are produced in lengths from 600 to 4000 meters and are supplied on special coils or drums. Their service life in the ground reaches 50 years, they reliably protect the fiber-optic cable from mechanical damage (in particular, from rodents), allowing the use of inexpensive fiber-optic cables without armor in FOCL. In addition, damage to the fiber optic cable during earthworks is excluded (it is placed in the PTA after the completion of the pipe laying).

RRP are usually laid in the ground in open trenches or by a trenchless method at temperatures from -10 ° C to + 50 ° C (RRP operation is allowed at temperatures from -50 ° C to 65 ° C). When laying in the ground, sharp bends of the PTA are unacceptable: the minimum radius should be 1.5 m or more.

In turn, laying FOCLs into the ground in protective pipes is usually carried out using manual tightening methods using Ultrasonic inspection; mechanized tightening using cable winches; pneumatic piston / pistonless method.

In general, laying FOCLs into the ground using special cable layers is the fastest way to lay FOCLs. It provides a significant degree of mechanization of the process along with an optimal track depth (approximately 1.2 m). Before laying, the ground is cut through with a cable knife, and the cable is laid in the resulting slot. Some cable managers allow you to lay multiple cables at different depths at the same time. Above the cables, laying of a signal tape or the installation of special information posts is required. Practitioners recommend using a signal tape, since the posts in our country sometimes serve a disservice, attracting the attention of metal seekers. The signal tape is made of a non-decaying material, most often yellow. The technology of laying fiber-optic communication lines requires ensuring a constant speed, as well as avoiding sharp bends and exceeding the permissible cable stretch (even the slope of the cable-layer must be constant).

Laying FOCL in the ground (in the ground) can also be carried out by the method of horizontal directional drilling (HDD) during the construction of FOCL. This method, also called directional drilling, is one of the most common methods for laying steel cable sheaths. Moreover, the puncture length can exceed 1000 m without reaching the surface. This technology It is used to cross obstacles such as agricultural land, railways and highways, tramways, water obstacles, at airports, under runways, as well as in nature reserves.