Optical fiber has offered a new level of communication support at high speed and with an optimized technical base. But to maximize the achievement of positive factors for the application of this technology, a quality installation is required. The fact is that the fiber optic cable only resembles the usual and traditional means of signal transmission, but its structure is much more complicated and more demanding in handling.
What is optical fiber?
Optical fiber itself is a thin quartz cylinder tube of varying degrees of density. Its composition is also heterogeneous, since alloying inclusions can be added even at the production stage to increase individual parameters. The functional structure is formed by two parts - the core and the shell (does not apply to the insulation coating).
The light pulse is always within the boundaries of these two levels, but is reflected only to the core of the conductor. Actually, this principle of operation also determines the high speed of data transmission with fiber optic cable. Twisted pair, by the way, in standard formats such as CAT3 and CAT5 provides a transmission speed of 10, 100, Mbit / s, while fiber reaches 1000 Mbit / s.
Cable structure classification
A fiber optic line may contain one or more modes, which are understood as the propagation mode of a light beam. Single-mode cables transmit all beams in one direction. They travel the same path at the same speed, reaching the end point of reception at the same time, which does not distort the signal. Technologically, the operation of a single-mode fiber optic cable is supported by laser receivers that use light radiation with only one wavelength.
Multimode fibers support several trajectories of the light direction, which leads to a significant spread of rays, so the signal is distorted. Direct transmission is provided not by a laser, but by a standard LED, which reduces the cost of laying the line. The same decision affects the increase in the operational life of the cable relative to the performance of a single-mode conductor.
Cable classification by purpose
Perhaps one of the weaknesses in terms of laying fiber optic cable will be its low versatility. The sensitive structure often imposes restrictions on the use of one cable in different conditions. As a rule, this is due to the thickness and protective insulators of the wire. Therefore, at a basic level, the following types of fiber are shared:
- For external installation. Usually forms trunk networks for many kilometers. It has high requirements for external protection - mainly from mechanical damage, so armored insulation based on steel, aluminum or polycarbonate has become widespread. To add rigidity to the contour, a metal wire is also used in the wire structure.
- For internal laying. A typical representative of this group is a fiber-optic cable for the Internet, which can form a multilevel and complex structure of information transmission network to a wide array of subscribers within a small subsystem. If we are talking about internal trunk lines, then fiber can be used in combination with twisted pair.
- For cords. Optical or switching cable segments that perform not so much the functions of a signal conductor as the tasks of transitional connections at short distances.
Cable specifications
Like other types of conductors, fiber has wide ranges of various parameters. If we talk about the most common formats and the average standard, then the electrical characteristics of a fiber optic cable can be represented as follows:
- The resistance of metal insulation in contact with ground / water for 1 km is not less than 2000 megohms.
- The ability to withstand voltage in a circuit with metal insulation is up to 20 kV.
- The maximum allowable pulse current is up to 105 kA.
- Bending radius - up to 20 external cable diameters.
- The service life of optical cables is up to 25 years.
As for the dimensions of the core, for single-mode fibers, the diameter range is 8-10 microns, and for multimode cores, from 50 to 62.5 microns. In the outer sheath, the standard diameter is universal for all types of optical fiber and is 125 microns. Such cables can be used in a structured cabling system with detachable and one- piece connections. For specialized applications in special conditions, an insulating shell buffer can be used, with which the outer diameter will vary from 250 to 900 microns.
Technological stages of laying fiber
After agreeing on the necessary documents, you can begin to develop a technical solution. At the first stage, the optimal method of organizing the cable line is selected. If we are talking about the main route, then almost all laying options are allowed - underground, under water, by air or by ground. To a large extent, this will depend on the type of conductor itself. For example, a self-supporting fiber-optic cable based on high-strength aramid filaments is optimally suited for suspension on reference power lines and communications. Moreover, it is used both for the device of small contours between houses, and for kilometer routes. In any case, the selected cable is carefully monitored and only then allowed for installation.
The next step is preparing the track itself. The main tasks of the performers in this part are to ensure the most favorable conditions for laying, fixing and future operation of the cable. Supporting and supporting infrastructure must be provided, and the laying line itself is formed with the expectation of minimizing bends and rotary assemblies. Then you can proceed directly to work activities.
Underground gasket
The placement of the fiber optic line underground can be carried out by an open trench method or by means of a pipeline. Insulating pipes for cable stretching in them are usually used when laying thick tracks over many kilometers. The most reliable way is to organize a trench with a depth of 70-150 cm, and then mount the support posts or blocks. A pipe is laid on them, into which the line is pre-wound. Typically, laying fiber optic cable underground is done by segments. Protective pipes alternately form a contour and are welded in parts, and the line is drawn as the distance increases. At the final stage, the track is covered with earth.
Open cable routing underground
In this case, dispense with special pipes, but with the use of a cable layer. This is a device that allows you to place fiber in a trench with minimal bends and support for the intended fixation loop. During installation, the cable runs smoothly through the cassette knife cassette with the previously set bending range. It is important that the laying depth is at least 120 cm and that there are no frequent intersections with underground utilities on the way.
In order for the fiber-optic cable to be placed along the entire route with the same parameters of the permissible slope angle, the bending radius in the stacker must be kept the same throughout the entire distance. After the installation is completed, a signal tape is drawn above the level of the cable, and electronic marker informants are installed at the points of intersection with other communications.
Air suspension
To install the cable in this way, you can use the existing infrastructure of power lines, rail or city transport, depending on the characteristics and purpose of the route. As already noted, the simplest installation of fiber optic cable through the air is carried out using a self-supporting wire. In this case, a bundle of cables is laid in one direction. Fastening is made to a previously stretched cable. As the rigid wire is unwound, the optical fiber adheres to it and is tied with polyethylene thread. Couplers and collars can be used only as an addition to the fixing system. The small mass of the optical fiber allows you to lay its cables in a tensile manner for many kilometers.
Methods for connecting optical fibers
It is advisable to avoid frequent connection nodes, but they cannot be completely eliminated anyway. Regardless of the method of laying and purpose of the cable, you need to perform a reduction of the two circuits.
This is done in the following ways:
- Using connectors. A constructional version involving the use of mechanical devices - a kind of splitter. The method is convenient, but the quality of the connection and the reliability of such a connection leave much to be desired.
- Gluing together. A more reliable option for connecting fiber optic cable is through epoxy adhesive. It is desirable to use two-component compositions with a refractive index corresponding to a particular fiber. This method gives a good operational effect, but the installation process itself can cause a lot of trouble.
- Welding. A special soldering iron machine performs heat treatment of the ends of two lines of optical fiber, after which the compliant structure forms a monolithic joint. The seam is strengthened with heat-shrink sleeves and after a while allows you to use the cable in further installation operations.
Fiber optic cable
When the line is brought to the immediate object of operation, it remains only to complete the installation process with the help of electrical fittings. The basic element in this infrastructure will be a socket. It is located in the house or apartment at the entrance and connects the consumer equipment to the distribution panel.
To enter the cable into the outlet, it is advisable to use an optical patch cord. From this node, you can lay a fiber-optic cable for the Internet under a router, line for a phone or TV. During installation operations, crimping crimpers are used for the standard RJ11 connector, an RJ format plug, as well as cable stripping tools.
Conclusion
It is difficult to overestimate the importance of fiber for the organization of modern telecommunication lines. Practicality and versatility, coupled with high technical and operational data, have made fiber optic cable the most popular information conductor both in commercial structures and at the household level. Of course, it does not dispense with the negative factors of using this cable, which is expressed both in the high cost and in the individual nuances of installation. But practice shows that these weaknesses are more than offset by the positive effects of the application, not to mention the desire of manufacturers to optimize the technology of laying fiber-optic routes.