How to lay a fiber optic cable. How to lay fiber optic cable. An example of a typical solution for laying a fiber line

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 high culture production.

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 communication network common use. Approved by order of the State Committee for Communications of Russia No. 97 dated December 17, 1997.

6. Regulations on the organization 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 due to 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 operations to splice OM, as well as increased requirements to 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, 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 is checked, the compliance of the construction length markings indicated in the passport with the 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. Its basis is 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 electric 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, directing it 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;

The 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 electrical 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 the manufacturer’s technical documentation. 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 cable is cut with cable cutters or sawed through 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 note that alcohol and solvents used when removing protective coatings, are flammable and burn with a colorless flame, can be toxic and cause an allergic reaction.

5. Welding machines are used to form an electric arc high voltage, 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 the 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 communication networks.” – 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 status 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

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. At in various ways Special types of optical cable are used for gaskets. 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 trunk 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 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; avoiding 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 suspensions must move freely along the steel cable and tightly cover 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 sections, a cable that has a certificate must be used fire safety. 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 for suspending fiber-optic cables on the supports of the contact network of electrified railways and high voltage lines automatic blocking, 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, they are provided favorable conditions to inspect 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 reduced to a minimum, since they are already built, which means that 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 consequences of the influence 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 environmental conditions and the adopted technical operation system.

They say that laying an optical cable along the ocean floor costs the Anglo-French concern Alcatel billions of dollars. One vein of glass 125 microns thick can provide speeds of hundreds of terabits/sec. It is clear that there are plenty of people who want to connect the continents. This is not to say that the connection is too reliable. In 2011, the news reported: one grandmother left the country without the Internet. Let's get a look…

Optical cable

Transmitting information 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, almost entirely Armenia, lost their boarding school. Modern fiber optics are capable of great feats. The first research began in the mid-19th century, and a number of inventions were presented to the public in the following years:

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

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

First, a 4,000 km long section takes three weeks to load onto a ship. The process takes place 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 reel. Several people work, 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 production line has been developed for the production of cables. The future screen from the strip is twisted into a half ring, and an optical fiber strand is laid inside. The structure is pulled through a series of steel rollers of decreasing gauge, reminiscent of the copper cable manufacturing cycle. Welding is carried out along the seam, the cable is ready. All that remains is to cover it with a moisture-proof shell. The cable can withstand enormous loads; any product undergoes similar tests. In the Russian Federation, according to standards, a hair of glass can withstand a tensile force of 7 kg.

Optical cable connection methods

The methods of laying optical cables offer little new information to the traditional ones; the joining 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 amount of loss in dB. A joint that reaches 0.4 dB is considered a defect. A good welded joint will provide a reading of 0.01 dB. To withstand stringent requirements, special equipment is produced for the work. Today, the following methods of connecting optical cables and installing connectors have become widespread.

Welding

Is the most in a simple way, any type of optical cable is suitable. The parameters of which are stored in the device’s software module. By visiting the menu, the technician selects the desired type. The procedure is similar.

Cable welding

First, let's find a sleeve (KDZS) for a fiber-optic cable of the appropriate thickness. The insulation is stripped down to a couple of centimeters. The Kevlar braid is removable (if equipped). Afterwards, the core is fired using a welding machine with a special grip. It is necessary to finally get rid of isolation. The end is cut off (broken off) with a cutter (structurally included in the welding machine). Helps the section become perfectly smooth. Both ends are processed alternately; we put a heat-shrink sleeve on one.

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

Mechanical connections

They have the advantage of being disassembled n number of times. To carry out the work, a special coupling is purchased; it is difficult to do without a tool: you will have to strip the insulation to the specified distance (tens of mm). Afterwards, the ends are cut evenly using a device resembling a glass cutter. The ends are inserted into the coupling and clamped. Installation is considered complete. We use one coupling for fiber-optic cores of different diameters, using special adapter inserts. The preparation process changes a little in small ways.

Connectors

At the entrance of distribution boxes, when connecting user equipment, connectors are often used. Special connectors exhibit high losses, allowing for countless re-wiring changes. Each company has its own technologies. Giganet has developed instructions that come with specialized tools.

Cable stripping is an art. The outer insulation and braiding are removed to the specified length, and the inner layer is stripped (down 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 core or break it off. The slightest scratch increases losses through the walls. Glass fragments can easily sting your skin.

The stripping is finished, it’s time to put on the insulators and connector housing. The central core is obviously pulled through with a large margin.
Fill the connector with the compound included in the kit until a small drop appears through the central hole. It is important not to overdo it, not to combine the outer and inner circles of the coax.
The supporting glass fiber is lubricated with a hardener. Docking is done quickly so that the mixture does not have time to set.
After using a glass cutter (sold by Giganet), the core is cut and broken off with a small margin.
The sanding process begins with fine sandpaper. A microscope will be 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 becomes perfectly smooth.
Then finishing procedures follow, the product can be used.

How to lay an optical cable

Inside entrances and houses, the optical cable is laid following the usual standards. The surface is fireproof; for installation, packing tape is used, which is pressed onto dowel-nails. In fact, the cable is equivalent to connected wires. Let's try to evaluate suitability!

The optical cable for laying in the ground (earth) is equipped with special markings. There is a letter Z after OK (optical cable). Some rules for laying optical cables and the marking method are specified in GOST R 52266.
The optical cable for internal installation is marked with the letter C.
There is no optical cable for external installation as such. The range includes underwater (H), aerial (V), field (F) cables.
Particularly flexible cords are marked with the letter Ш. You can bend them, forgetting the restrictions.

Preparing to lay the cable

Laying and installation of optical cables is carried out in accordance with fire hazard. If the braid is made taking into account the peculiarity, the following letters are added to the marking:

NG – flame retardant.
LS (low smog) low emission of smoke and gas during combustion.
HF – reduced corrosive activity of combustion products.
FR (fire resistance) – increased fire resistance.

It will come in handy, read the rules of use in the second section of the PUE 6. It is not in fashion now, tables 2.1.2, 2.1.3 provide information that gives a live idea of how installation is usually carried out. We are talking about electricians, let's ask those who have doubts - have you seen how fiber-optic cables for external installation 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 one thin strand of glass can power an area with internet, don't forget: indoor fiber optic cables are poorly understood. Although the first telephone network in Moscow began operating in 1986, the last outdated one (1949) was removed in 2011. The phenomenon of fire in fiber-optic cables has not even been studied yet, although providers have completely switched to the technology. You will see, there is not even a single standard for gaskets. GOST refers entirely to recommendations of narrower technical conditions. This is how the operating temperature, minimum bending radius, and operating conditions are regulated. The tools are not even listed, there are very few domestic developments, each company pursues its own line.

Trench laying

Separately on installation, you should read the Guide to Laying, Installation and Commissioning of Fiber Optic Communication Lines. To avoid interference, the cable is laid inside a HDPE pipe with an internal diameter of 25 mm and an external diameter of 32 mm. It is not allowed to pull connected copper networks nearby. It is allowed to lay optical cables in the cable duct nearby (5-6 in number). If it is necessary in the future to install copper communication wires, you should use HDPE pipe; it is better to foresee the option in advance and do it as written above. The requirement applies to sections longer than 2 km.

The standard specifies what is required before laying an optical communication cable:

According to the text, HDPE pipe is supplied in coils. Using the fact, you can tell whether the one lying on the counter is suitable.
If the pipe for the fiber optic cable gets stuck in the channel between the wells, you need to turn it several times.
Pruning in the trench is carried out, leaving a reserve. Then, at the entrance to the channel, the pipe is tightened with a clamp and held in place.

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

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

vashtehnik.ru

Fiber optics is a real breakthrough in communications technology. Today, thanks to this kind of cable, highly accurate 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 the city in a web.

Laying methods
Stagedness

The rules for laying fiber optic cables are stipulated in many ways. The first thing you need to decide is the type of cable. It depends on the conditions and installation method, as well as on the installation object. For example, aerial cable installation uses suspended 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 harmful environmental influences 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 ground movements and are equipped with a central load-bearing 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 horizontal drilling, winding on a lightning cable or laying in asphalt when being built road surface. In buildings, cable laying rules allow the use of low-current channels or voids beyond suspended ceiling. In addition, laying 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 permissible for each cable individually). All cables used in buildings must be tested in accordance with fire safety conditions. When laying underground (in the ground), it is necessary to dig trenches at least 1 m deep, taking into account the length reserve 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 along a cable well.

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

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

Sources:

Features of working with fiber optics

How to lay a fiber optic cable

www.kakprosto.ru

2.3.2 Methods for laying optical cables when building fiber optics

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.

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.

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 effects 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.

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

Laying fiber optic cable in cable ducts. 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.

1 – cast iron covers; 2 – pipelines; 3 – cable; 4 – inspection wells; 5 – hatches

Figure 2.4 – Cable duct