Making life easier: we fork the backbone with optical crosses. High Density ODF Mounting Requirements for ODF Mounting

Sleeve for fiber optic welding: KDZS

Despite the apparent simplicity, it is quite complex and, in its own way, an irreplaceable detail. Designed to protect and seal the splice and the area of ​​the fiber cleaned from varnish. Consists of three components.

1. Metal core. Serves as a rigid frame, does not allow the sleeve to "warp" in the stove, distributing the heat evenly.
2. Hot melt adhesive. Fixes the fiber after cooling, seals the joint.
3. Heat shrinkable tube. Shrinks in the oven, forms the outer protection of the connection.

Sleeve with HERE for protection of the welding joint OV (KDZS)
Enlarge photos

In the initial state, they are a tube with a length of 3 to 6 cm. The fiber is inserted into the sleeve before welding. After welding and checking the joint with a reflectometer, the sleeve is moved to the joint and placed in the stove of the casing device.

Can be supplied complete with a coupling.

12/27/13 Information supplemented with the page Fiber optic sleeves - KDZS

OV laying in a splice plate (cassette)

Stacking optical fibers in a cassette (fiber organizer or splice plate)

The spliced ​​fiber together with the sleeve cased at the junction looks like a thin line with a sleeve weight in the middle. To neatly fix such a "web" in all optical couplings and terminal crosses, a special box is used, somewhat similar to a VCR cassette. People often call this box a cassette, but there is also official name- fiber organizer (splice plate). Cassettes (splice plates) for laying optical fibers sometimes differ slightly in design, but as a rule contain cells for fastening sleeves and some space for laying out cable fibers or optical cords. Photos of various cassettes:

Cassette (fiber organizer or splice plate)
for laying optical fiber in the box of the cross-country. Red inserts for mounting sleeves

Cassette with laid optical fiber in the optical distribution box.
The sleeves not only fit into the cells, but are also fixed with a special fastener

Fiber optic cassette for installation in a sleeve

Sequence of assembly of couplings and fiber-optic communication terminals

Mounting technology for fiber optic couplings and end devices

Couplings and fiber-optic distribution frames have different shapes and, accordingly, different assembly sequences. As a rule, suppliers or manufacturers include installation instructions for each coupling. By design, I just note that some types of couplings remain partially collapsible after final installation (clip-latch) or completely welded.

1. Start with pruning. According to the old, perhaps not written rules, 2 meters of cable is simply cut off. This is due to the fact that when tightening, the end of the cable has a maximum of shocks and bends; moreover, if the shell is broken, water could get into the module, which will subsequently cause clouding of the fiber glass.

2. On the fiber-optic splice, a reserve of cable is left, the purpose of which is the possibility of replacing or altering the splice. Its length has changed over the years (initially 15 meters, now less). On intercity lines everything is documented see protocol forms. Much of this stage can be agreed by the customer or recorded in the project. Sometimes the stock can be left and much larger due to the peculiarities of the write-off of the cable in the building communications organizations.

Fiber optic in modules
(4 pcs. in each)

3. Protective sheaths are removed from the cable to a length of about 1 meter, up to the optical modules, only a certain section of the armor is left for its fixation and electrical connection. Optical modules are wiped with nefras or alcohol from the remains of the hydrophobic filler.

4. Partially cut ends are pushed into the holes of the coupling or cross and secured. In crosses, the armor is connected to a soft wire and is output to the rack grounding terminal. Secure the cassette.

5. Next, as a rule, with a special clothespin-knife, cut the shell of the optical module so that the ends of the shell of the module are fixed in the cassette clamps. Fibers are also rubbed with nefras.

Fiber optic splice installation phase

7. A heat-shrinkable sleeve KDZS is put on one of the fibers to be welded.

8. Next comes a tool called a stripper. They remove the varnish from the ends of the fiber by about 2 - 3 cm (under the cleaver).

9. The cleaned optical fiber is wiped with alcohol or a special napkin and put into the cleaver to chip.

10. The welding process is described on the welding page. Measurement and control of the welding joint with an optical reflectometer is also carried out.

11. The fiber optic sleeve is being cased.

12. The spliced ​​fibers are placed in a cassette (fiber organizer or splice plate).

Fiber-stacked fiber cassette

13. Steps 7 through 12 are repeated for the rest of the optical fibers.

14. After casing and laying all the fibers, the OTDR control is carried out anew.

15. For the coupling, everything is sealed and placed in a pit (well). For cross-country installation and connection of connectors.

Formal order of installation of fiber optic cable disclosed on pages
12.6 Installation of optical couplings(Guidelines for the construction of linear structures of local communication networks, M., 2005)
10.3 Routing optical cables from (Manual for the operation of line-cable facilities of local communication networks)

Information on the organization of terminal devices is also available on the pages of the book "Fiber Optics. Theory and Practice" - Connection panels, connection devices and terminal compartments. Shelter connections

Mounting instructions for couplings:
Fiber optic splice shortened MOGU
Fiber-optic dead-end coupling MTOK

To enter the optical cable and connect the station equipment to the line, optical cross-sections are used. For the implementation of the FOCL construction project, it is necessary to select the brand and capacity of the optical distribution frame. For terminal points designed by fiber-optic communication lines at Zhetygen station and Korgas station, required amount sockets in the cross-section is 16. At the intermediate points, Kurozek station and Shelek station, where two cables are installed, 32 sockets are required. These requirements are met by optical distribution frames of the PR-16 type produced by OJSC "2ASistem", Tula. One cross is installed at the terminal points, two at intermediate points (sides A and B), a total of 6 optical crosses are required.

Since optical pigtails are ordered separately, we will select standard 1m pigtails. with FS-type connectors (accordingly, the optical distribution frame will also be equipped with FS-type connectors).

Optical distribution frame (Fiber Cross) Distribution panel PR 16

General information.

Optical distribution frame (Fiber Cross) distribution panel PR 16 provides:

• - Input, placement, fastening and storage of stocks of station and line cables;
• - Termination, connection, switching of line and station cables with optical fibers in a communication network common use, in technological communication networks and special-purpose communication networks;
• - Connection of control and measuring equipment;
• - Possibility of marking line and station circuits.

Optical distribution frame technical characteristics.

The maximum number of incoming line fiber optical cables- 4 things.

The maximum number of optical connecting sockets on the panel is 16 pcs.

Overall dimensions of the Fiber Cross PR 16 - 484 x 280 x 44mm

The mass of the Fiber Cross of the PR 16 distribution panel is 2.4 kg.

Optical Port Type - FC, SC, ST, FC / APC, SC / APC

Optical distribution frame delivery set.

Optical distribution frame (Fiber Cross) distribution panel PR 16 is completed according to table 3.3

Table 3.3 - Delivery set of optical distribution frame

	Name	Quantity, pcs.
	Distribution panel
	Splice plate
	Screw-washer-nut kit	1 (supplied by agreement)
	Coupler 80mm
	Screed 140mm
	Organizing platforms
		By number of ports
	Passport products

Notes.

It is allowed to replace the products included in the delivery set with similar others that do not impair the presentation, performance and meet safety requirements.

Supplied by agreement with the customer

Safety requirements for optical distribution frames.

Before starting work, carefully study this passport.

Optical distribution frame must be used in accordance with the purpose indicated in the passport.

Optical crossover device (Fiber Cross) PR 16.

Optical distribution frame is metal box, painted using powder coating technology, which provides reliable protection from external influences. A splice-cassette (splice plate) is located inside the optical distribution frame for stacking sleeves and a supply of fibers (there is a possibility of placing 24 fibers on one splice-cassette)

The optical distribution frame has four openings for the input / output of the optical cable. The holes are closed with rubber plugs to protect the inner space of the optical distribution frame from dust ingress; when installing an optical cable (OK) in PR 16, you can choose one of four holes for entering OK (or use all four if necessary).

Installation manual for optical distribution frame (Fiber Cross) PR 16

Unpacking - Be careful not to damage the ODF with the instrument. After opening the package, check the external condition of the assembly units and parts of the optical crossbar, as well as the presence of all accessories according to the packing list.

Preparing for installation

Before proceeding with the OK installation, make sure that the mounting brackets on the right and left sides of the ODF are firmly fixed;

Place the Fiber Cross PR 16 on the work table for OK editing.

Figure 3.10 - General view of the distribution panel Fiber Cross PR 16 (in the photo without the top cover with FC connectors).

Cutting and cable entry

Cut the cable according to Figure 6.14.

Insert the cable into the Fiber Cross PR 16 through the hole, notching the rubber membrane.

Secure the OK with the ties included in the kit. Secure the central strength member with the bracket and screws as shown in Figure 3.12.

Slide heat shrink sleeves over pigtails.

Figure 3.12 - Entering the optical cable

Works with optical fiber.

Stripping the fibers and welding in accordance with the recommendations for the used welding equipment;

Number the modules of the cable to be installed;

Number the pigtails and weld them with the appropriate fibers;

Bake heat shrink sleeves (heat shrink sleeves included);

Place the sleeves and stocks of fibers in the cassette, according to Figures 3.14, 3.15. (Figures for inserting cable modules and laying pigtails are spaced for ease of reading).

When laying stocks of cables, sleeves and pigtails, make sure that the bending radius of the fibers and pigtails does not exceed 30 mm.

Close the splice cassette with the transparent cover.

Connect pigtails to adapters according to their numbers.

Figure 3.13 - Input of cable modules

Figure 3.14 - Layout of pigtails

Rack mounting.

Optical distribution frame (Fiber Cross) distribution panel PR 16 is fixed in a 19 "rack with four M 6 screws (fixing screws are not included in the delivery set). Lay and fix the excess cable in a convenient place.

To assess the quality of the installation of the optical distribution frame, reflectograms of each optical fiber are taken in the regeneration section. With normal optical attenuation and no defects on the welded joints, the station equipment is connected to the line using patchcords.

Table 3.4 - Organization of jumpers on the optical distribution frame of the access node of the Kurozek station

At all points of communication on optical crossbones, 1-4 OV are switched to the equipment Huawei OptiX OSN 1500B. A linear path is organized for 1-2 OFs for the operation of a digital transmission system, 3-4 OFs are also connected to digital equipment and are used for automatic redundancy of the linear path.

A fiber-optic network for several rooms (buildings) is usually a connection of several lines into a common backbone, which is then directed to the switching node by a single multi-module cable. This branching of the highway into several lines can be carried out in a wide variety of ways, depending on the conditions and technical means, but the most simple option will use a special optical distribution frame to connect a multi-fiber cable to a single-channel optical cable.

First, it is necessary to explain what an optical distribution frame actually is. In a general sense, it is a box designed to protect an optical fiber connection, including organizational and connecting elements. However, unlike, which also serve to protect the junction, the crosses have sockets in their configuration, to which the optical fibers of the trunk cable are connected through special devices - optical pits. It is through these sockets that single-channel lines terminated with a corresponding connector on a conventional optical patch cord are connected to the backbone.

Network installation using cross-over boxes
This is the most convenient solution when you run a single backbone along a building, branching fiber modules from it as you pass the premises. The same situation usually develops if a powerful fiber-optic backbone runs along the street and produces branches to the houses. If, in the case of internal wiring of the network, you need wall-mounted crosses for rooms with sockets for a patch cord, then to connect the lines to the street backbone, you need to select a box depending on the characteristics of the cable of this line and technical conditions installation. For sequential routing of lines from a common backbone, crosses are suitable, equipped with an input and output channel for a trunk cable and sockets according to the number of lines planned for connection at a given point. Most often, one outlet is sufficient. If the separation of a single line occurs immediately from one point, then there is only one input for the trunk cable, but there can be quite a lot of sockets. Most often, this method of distributing the line is carried out in switching centers and technical rooms. For the convenience of mounting crosses in such cases, they are also made in the RAC version for placement in wiring closets. In addition, optical distribution frames can be executed with the possibility of subsequent opening without complete dismantling connections and without it. Thus, in order to select the most suitable optical distribution frame, you need to know:
.type of connection (transit branch of one, several communication lines or terminal branching);
.technological conditions (outdoor or indoor installation, wall-mounted or RAC'ovoe execution, the maximum possible dimensions and weight, the possibility of opening without dismantling);
. type of connectors plugged in (to match exactly the sockets).

It will be useful to know the type of both the trunk cable and the cable of the lines to be connected.

Installation of an optical distribution frame
Actually, the installation of the cross box itself is quite simple. The trunk cable is inserted into the hole provided for this in the box, the sheaths are removed and the cable is divided into modules. The retracted module is dissected, the fibers are stripped and prepared for connection to the pitgels. A pitgale is a connector with a small section of optical fiber that connects to the inside of the distribution frame socket. The connection to the end of the pitgale fiber is most often done by welding, but you can both glue and use splices - many optical crosses contain splice cassettes. The stock of the cable is placed inside the cross-section box without sharp bends and twists, usually there are special brackets for fixing the cable inside the case. Sleeves (or splices) of the connected fibers are placed in organizer cassettes, pit gails are connected and installation is completed, sealing the cable inlet and outlet openings and closing the cross box.

Fibers are charged into the splicer

Hello, Habr readers! Everyone has heard of optical fibers and cables. There is no need to tell you where and what the optics are used for. Many of you come across it at work, someone develops backbone networks, someone works with optical multiplexers. However, I have not come across a story about optical cables, couplings, crosses, about the technology of splicing optical fibers and cables. I am a splicer of optical fibers, and in this (my first) post I would like to tell and show you how all this happens, and also often in my story I will be distracted by other related things. I will rely mainly on my own experience, so I fully admit that someone will say “this is not entirely correct”, “it is not canonical here”.
There was a lot of material, so it became necessary to break the topic into parts.
In this first part, you will read about the device and cable cutting, about the optical instrument, about the preparation of fibers for splicing. In other parts, if the topic turns out to be of interest to you, I will tell you about the methods and show in the video the process of splicing the optical fibers themselves, about the basics and some of the nuances of measurements on optics, I will touch on the topic of welding machines and reflectometers and others measuring instruments, I will show the work places of the solder (roofs, basements, attics, hatches and other fields with offices), I will tell you a little about cable fastening, about the wiring diagrams, about the placement of equipment in telecommunication racks and boxes. This will surely come in handy for those who are going to become a splicer. I spiced it all up large quantity pictures (sorry in advance for the paint-quality) and photos.
Careful, there are a lot of pictures and text.

Introduction

First, a few words about me and my work.
I work as an optics solder. He started as a telephone operator and installer, then worked in an emergency team on the maintenance of trunk optics. Now I work in an organization that takes general contracts for the construction of facilities and communication lines from various companies. Typical construction project - cable line linking several containers of GSM base stations. Or, for example, multiple FTTB rings. Or what is smaller - for example, laying a cable between two server rooms on different floors of a building and bonding crosses at the ends of the cable.
If the tender is won, suitable subcontractors are looked for to perform the work (design and survey and construction and installation). In some regions these are our subsidiaries, in some we have our own equipment and resources, in some we employ independent companies. On our shoulders, we mainly have control, elimination of stocks of subcontractors and various force majeure, all kinds of agreements with land owners and administrations, sometimes drawing up executive documentation for the constructed object (documentation - mainly RD 45.156-2000, here is a list, plus more is added section with different licenses) and so on. Often you need to work with optics: weld or digest somewhere an optical coupling or cross, eliminate the consequences of a support knocked down by a street racer or a tree that has fallen on a cable, carry out an input control of a cable drum, take an area reflectogram, and so on. These are the tasks that I do. Well, incidentally, when there are no optics tasks - other tasks: from loading and assembly through courier delivery to copying and paper work. :)

Optical cable, its types and internals

So what is an optical cable? Cables are different.


By design - from the simplest (a shell, under it are plastic tubes-modules, they contain the fibers themselves) to super-sophisticated (many layers, two-level armor - for example, for underwater transoceanic cables).

At the place of use - for external and internal laying (the latter are rare and usually in high-end data centers, where everything should be perfectly correct and beautiful). According to the laying conditions - for suspension (with Kevlar or cable), for soil (with armor made of iron wires), for laying in cable ducts (with corrugated metal armor), underwater (complex, super-protective multilayer structure), for suspension on power transmission line supports (except for the transmission of information, they play the role of a lightning protection cable). In my practice, the most common cables are for suspension on poles (with Kevlar) and for laying in the ground (with armor). Less often come across with a cable and corrugated armor. It is also common to find a cable that is essentially a thin paired optical patch cord (yellow sheath for single mode and orange for multimode, a bit of Kevlar and one fiber; two jackets are paired). Other optical cables (without protection, underwater, for laying indoors) are exotic. Almost all the cables I work with are of the same design as the picture below.

1 - central power element(in other words, a fiberglass rod, although there may be a cable in a polyethylene sheath). Serves for centering the tubes-modules, imparting rigidity to the entire cable. It is also often used to fix the cable in the sleeve / cross-section, clamping it under the screw. With a strong bend, the cable has the mean property of breaking, breaking along the way the modules with part of the fibers. More advanced cable designs contain this rod, dressed in a polyethylene sheath: then it is more difficult to break it and it will cause less damage in the cable if it breaks. The bar can be the same as in the figure, and very thin. The tip of such a rod is an excellent abrasive tool for delicate work: for example, cleaning relay contacts or a section of a copper part for soldering. If you burn it a couple of centimeters, you get a nice soft brush. :)
2 - themselves optical fibers(in the picture - in lacquered insulation). The very thinnest fiber-optic threads for which everything is started. The article will focus only on glass fibers, although somewhere in nature there are also plastic ones, but they are very exotic, they are not cooked by devices for welding optics (only a mechanical connection) and are suitable only at very short distances and I personally have not come across them ... Optical fibers are singlemode and multimode, I have met only with singlemode, since multimode is a less common technology, can only be used over short distances and in many cases is perfectly replaced by singlemode. The fiber consists of a glass "shell" made of glass with certain impurities (I will not dwell on chemistry and crystallography, since I do not know the topic). Without varnish, the fiber has a thickness of 125 microns (slightly thicker than a hair), and in its center there is a core with a diameter of 9 microns made of ultrapure glass with a different composition and with a slightly different refractive index from the shell. It is in the core that radiation propagates (due to the effect of total reflection at the core-shell interface). Finally, the top of the 125-micrometer cylinder of the "shell" is covered with another shell - made of a special varnish (transparent or colored - for color coding fibers), which EMNIP is also two-layer. It protects the fiber from moderate damage (although without varnish, the fiber bends, but it is bad and easy to break, the fiber will elementarily crumble from a mobile phone accidentally placed on it; and in varnish it can be safely wrapped around a pencil and pulled quite hard - it will withstand). It happens that the cable span sags on some fibers: all the shells, Kevlar broke (burnt, cut), the central bar burst, and some 16 or 32 125-micrometer glass fibers can hold the weight of the cable span and wind loads for weeks! Nevertheless, even in the varnish, the fibers can be easily damaged, so the most important thing in the work of the splicer is meticulousness and accuracy. One awkward movement can ruin the results of a whole day of work or, if you are not particularly lucky and there is no redundancy, drop the trunk connection for a long time (if, while digging into the “combat” trunk coupling, you break the fiber with DWDM under the spine at the exit from the cable).
There are many types of fibers: regular (SMF or just SM), dispersion shifted (DSF or simply DS), non-zero dispersion shifted (NZDSF, NZDS or NZ). Outwardly, they cannot be distinguished, the difference is in the chemical / crystal composition and, possibly, in the geometry of the central core and in the smoothness of the boundary between it and the shell (unfortunately, I did not fully clarify this issue for myself). Dispersion in optical fibers is a harsh and difficult thing to understand, worthy of a separate article, so I’ll explain it easier - dispersion-shifted fibers can transmit a signal further without distortion than simple ones. In practice, splicers know two types: simple and "offset". In the cable, the first module is often allocated for the "offset", and the rest - for simple fibers. It is possible to dock the "offset" and a simple fiber, but it is undesirable, it causes one interesting effect, which I will talk about in another part, about measurements.
3 - plastic tubes-modules in which the fibers float in a hydrophobic.

Cable stripped to modules

They easily break (more precisely, suddenly bend) when bent like telescopic antennas in household receivers, breaking the fibers inside themselves. Sometimes there is only one module (in the form of a thick tube), and there is a bundle of fibers in it, but in this case, too much is needed different colors for marking fibers, therefore, usually several modules are made, each of which has from 4 to 12 fibers. There is no single standard for colors and the number of modules / fibers; each manufacturer does it differently, displaying everything in the cable passport. The passport is attached to the cable drum and is usually stapled to the tree directly inside the drum.

Cable passport

Typical cable passport. Sorry for the quality.

However, there is a hope that, say, the DPS cable from the Transvok and Beltelekabel manufacturers will nevertheless be the same in configuration. But you still need to look at the passport for the cable, where the detailed colors are always indicated and what type of fiber are in which modules. The minimum capacity of an "adult" cable that I have seen is 8 fibers, the maximum is 96. Usually 32, 48, 64. It happens that out of the entire cable 1 or 2 modules are occupied, then instead of other modules, black dummy plugs are inserted (so that the overall parameters cables have not changed).
4 - film braiding the modules. Plays secondary roles - damping, reducing friction inside the cable, additional protection from moisture, keeping the hydrophobe in the space between the modules and, possibly, something else. Often it is additionally tied with threads crosswise and moistened with hydrophobic gel on both sides.
5 - thin inner shell made of polyethylene. Additional protection against moisture, a protective layer between the Kevlar / armor and the modules. May be absent.
6 - kevlar threads or armor... In the figure, armor is made of rectangular bars, but much more often it is made of round wires (in imported cables, steel wires are difficult to cut even with wire ropes, in domestic cables, they are usually made of nail iron). The armor can also be in the form of fiberglass rods, the same as the central element, but in practice it has not been encountered with this. Kevlar is needed so that the cable can withstand a large breaking force and at the same time not be heavy. It is also often used instead of a cable where there should be no metal in the cable to avoid pickup (for example, if the cable hangs along railroad, where next to the contact wire with 27.5 kV). Typical values ​​of the permissible tensile force for a cable with Kevlar are 6 ... 9 kilonewtons, which allows it to withstand a large span under wind load. When cutting, Kevlar terribly blunts the cutting tool. :) Therefore, it is better to cut it either with special scissors with ceramic blades, or bite off with ropes, which I do.
As for the armor - it is designed to protect an underground cable lying directly in the ground, without protection in the form of a plastic pipe, cable duct, etc. However, armor can only protect from a shovel, the excavator still tears any cables in flight. Therefore, the underground cable is buried 1 m 20 cm in the ground, and a yellow or orange warning tape with the print “Caution! Don't dig! Below is a cable ", as well as along the route there are bollards, warning signs and notices. But they still dig and tear.
7 - external fat polyethylene sheath... Becomes the first to take on all the burdens when laying and operating the cable. The polyethylene is soft, so it can be easily cut if the cable is inaccurately tightened. It happens that when laying underground cable the contractor will tear this sheath up to the armor by several meters and will not notice, moisture gets into the cable in the soil despite the hydrophobicity, and then on delivery, when testing the outer sheath with a megohmmeter, the megohmmeter shows low resistance (high leakage current).

If the hanging cable touches a concrete post or tree, the polyethylene can also quickly rub to fibers.
There may be a plastic wrap and some hydrophobic gel between the outer shell and the armor.

In Russia, unfortunately, optical fibers are no longer produced (here, alas, a joke about polymers would be appropriate). There is a Russian laboratory making test fibers for special purposes, esvaf suggested.
They are bought from companies such as Corning, OFS, Sumitomo, Fujikura, etc. But cables are made in Russia and Belarus! Moreover, in my practice, 95% of the cables I have worked with are cables from Russia or Belarus. At the same time, imported fiber is embedded in the cable. Offhand, from my experience, I recall such cable manufacturers as Beltelekabel, MosKabel Fujikura (MKF), Eurocable, Transvok, Integra-cable, OFS Svyazstroy-1, Saransk-cable, Inkab. There are others. Of the imported cables, only Siemens remained in the memory. Subjectively, all cables are similar in design and materials and do not differ much in quality.
Here, in fact, I talked about the device of optical cables. Go ahead.

Cutting the cable: a necessary tool and technique

For cable stripping, as well as for welding, a number of specific tools are required. A typical set of an installer-solder is a suitcase with tools "NIM-25", it contains all the necessary strippers, cable tricks, screwdrivers, side cutters, pliers, a breadboard knife and other tools, as well as a pump or bottle for alcohol, a supply of hydrophobic solvent "D- Gel ”, non-woven lint-free napkins, electrical tape, self-adhesive numerals-markers for cables and modules and other consumables.


After completing consumables(ties, worm clamps, etc.) and some auxiliary tools, it is quite enough for working with optics. There are also other sets, richer and poorer in terms of configuration ("NIM-E" and "NIM-K"). The weak point of most kits is the poor quality of the "aluminum" case, which only looks nice, but in fact consists of thin fiberboard, glued with textured / corrugated foil, and aluminum thin corners with rivets. It does not last long in field and urban conditions, and it has to be repaired and strengthened. In my case, the case withstood for 3 years and, being all wounded, pulled together with corners and bolts, with a "collective farm" organizer instead of the native one, was replaced with a regular plastic box for tools. Some of the standard tools and materials may be of poor quality. I personally didn't need some of the tools. Some have already been replaced in 3 years of work. As the "branded" consumables are spent, some are replaced by "assistants" without compromising the quality of work. So, factory non-woven lint-free wipes for cleaning fibers are easily replaced. toilet paper type "pharynx plus". :) The main thing is that it is unflavored. Instead of the expensive (about 800 r / liter) D-Gel, if you work outdoors, you can use AI-92 gasoline.

When cutting cables, it is important to maintain the lengths of the cable elements in accordance with the requirements of the instructions for the coupling: for example, in one case it may be necessary to leave a long power element in order to fix it in the coupling / cross, in another case it is not required; in one case, a pigtail is braided from the Kevlar cable and clamped under the screw, in the other case the Kevlar is cut off. It all depends on the specific coupling and the specific cable.

Consider the stripping of the most typical cable:

A) Before cutting a cable that has been in dampness for a long time or without a waterproof end, you should cut off about a meter of cable with a hacksaw (if the margin allows), since prolonged exposure to moisture negatively affects the optical fiber (it may become cloudy) and other elements of the cable. Kevlar threads in a cable are an excellent capillary that can "pump" water into itself for tens of meters, which is fraught with consequences if, for example, high voltage wires run parallel to the cable: currents can begin to walk on wet Kevlar, water evaporates, crushes from the inside outer sheath, the cable is bubbling and new moisture enters through the rain bubbles.

B) If there is a separate cable for suspension in the cable structure (when the cable has the shape of the figure "8" in cross-section, where the cable is in the lower part, in the upper cable), it is bitten out with ropes and cut off with a knife. When cutting the cable, it is important not to damage the cable.

C) A suitable stripper knife is used to remove the outer sheath of the cable. NIM-25 is usually equipped with a knife "Kabifix" as in the photo below, but you can also use a stripper knife for electrical cables, which has a long handle.

Such a stripper knife has a blade that rotates in all directions, which can be adjusted in length in accordance with the thickness of the outer sheath of the cable, and a clamping element for holding on to the cable. Important: if you have to cut cables of different brands, then before cutting a new cable you need to try the knife at the tip and, if it cut too deep and damaged the modules, the blade must be twisted shorter. It couldn't be worse when the sleeve has already been welded, and suddenly, when laying the fibers, one fiber suddenly "jumps out" from the cable, because during cutting the knife hooked on the module and broke this fiber: all the work is down the drain.
With a stripper knife, to remove the outer sheath of the cable, a circular cut is made on the cable, and then two parallel cuts from it are made from opposite sides of the cable towards the end of the cable so that the outer sheath splits into two halves.

It is important to set the correct length of the stripper knife blade, since if the blade is too short, the outer shell will not easily split into two halves and it will take a long time to rip it off with pliers, and in the case of a long blade, you can damage the modules in the depth of the cable or blunt the rotating blade against the armor.

D) If the cable is self-supporting with Kevlar, then the Kevlar is cut with ropes or scissors with special ceramic blades.


Trosokus

Kevlar should not be cut with a knife or simple scissors without ceramic blades, as Kevlar quickly blunts metal cutting tools. Depending on the design of the coupling, it may be necessary to leave part of the Kevlar of a certain length for fixation, this will be described in the installation instructions for the coupling.
If the cable is intended for laying in a telephone sewer and contains only a metal corrugation from the armor (so that the rats do not gnaw it), it can be cut longitudinally with a special tool (reinforced plow knife). , to achieve an increase in metal fatigue in the place of risks and the appearance of a crack, after which you can remove part of the corrugation, bite the modules and pull off the corrugation. Such cutting should be done with special care, since it is easy to damage the modules and fibers: the corrugation is not too strong, it can shatter in the place where it is picked with tools, and when pulled from the fibers, sharp edges at the fracture site can weave the modules and damage the fibers. A cable with a corrugation is not the most convenient for cutting.
If the cable is armored with round wires, they should be bitten off with ropes in small batches, 2-4 wires each. Side cutters are longer and heavier, especially if the wire is steel. Some couplings require a certain length of armor for fixing, and armor (including corrugated ones) often needs to be grounded.

E) For the inner, thinner sheath, which is present in some cables (for example, in self-supporting with Kevlar), a separate, pre-configured stripper knife should be used (it can be the same as for removing the outer sheath of the cable) so as not to knock the knife length settings every time you cut the cable. In this case, it is especially important to correctly set the length of the blade in the stripper knife, it will be less than in the stripper for removing the outer sheath of the cable, since the inner sheath is much thinner, and immediately below it there are modules with fibers. With a certain skill, an ordinary breadboard knife can be used to remove the inner shell, making a longitudinal cut with it, but there is a significant risk of damaging the modules. You can also use a clothespin stripper to cut the coax.

E) Threads, plastic film and others are removed from the modules using napkins and D-Gel / gasoline auxiliary elements... The threads can be twisted one at a time, they can be ripped off with a special sharp "plow" hook (may be included in the design of some stripping knives to remove the sheath). To remove the hydrophobe, D-Gel solvent (colorless oily liquid, orange-smelling, toxic) or gasoline is used. However, with gasoline, be careful: office employees who have gasoline nearby will not be happy with the scent. And it is fire hazardous.
You should work with disposable gloves (surgical, plastic or construction gloves), since a hydrophobic is a very unpleasant disgusting (the most unpleasant thing in the work of a solder!), It is difficult to wash, after gasoline or a hydrophobe, the hands remain greasy for some time, and after cutting the cable, fibers are to be welded, requiring cleanliness of hands and workplace. In winter, hands stained with a hydrophobe are very cold. However, having got the hang of it, you can cut cables almost without getting your hands dirty.
After removing the threads and dividing the bundle of modules into separate modules, each module is wiped with napkins or rags with D-Gel solvent / gasoline, and then alcohol until clean. Although, in order to save time and to get less dirty, you can do the following way - initially cut the cable to the modules not to the end, but in the place where the cutting begins, by 30 centimeters, without wiping anything, bite the modules (see paragraph "e") and pull off the entire bundle of modules with winding and threads from the fibers, holding the clean end of the cable with your hand like a handle. Hands remain almost clean and time is saved. However, with this method of cutting, there is a risk of breaking part of the fibers or applying excessive tensile force to the fibers, which will negatively affect the attenuation of the fibers in the future, and also more likely to damage the modules, therefore this method is not recommended, especially in winter, when the hydrophobic filler thickens. First you need to learn how to do it right, and then try different optimizations.

g) At the required length, each module (except for dummy modules, they are bite out to the root, but first you need to make sure that they really do not have fibers) is bite off with a stripper for modules (suitable for copper coaxial), after which the module can be special efforts pull off the fibers.


Biting the modules with the stripper is a very crucial moment. It is necessary to choose a recess of the exact diameter, since if the recess is larger than necessary, the module will not bite enough to easily remove, if less, there is a risk of biting the fibers in the module. In addition, you should carefully monitor the stripper lock dog: if at the moment of biting the module it blocks the stripper's reverse stroke, fixing it in a "closed" state, then in order to separate the stripper and fold the lock, you will have to close the instrument again on the already bitten module, while there is a high probability of biting the module, which will lead to the need to rewire the cable. We remember that when biting one of the modules, other modules actively interfere with us, which must be held with the other hand, and the cable itself must also somehow be held by weight. Therefore, at first it will be very inconvenient and two people should cut the cable.
There are cable designs where the module is unique and looks like a rigid plastic tube in the center of the cable. For high-quality removal of such a module, it should be cut in a circle with a small pipe cutter (it is not included in NIM-25), and then carefully break it in place of a circular risk.
When tightening the modules, make sure that all fibers are intact and that no fiber is left sticking out of the tightened module.
If the temperature is low, the modules are thin, due to the cable design, the modules have little hydrophobicity (= grease) or the length of the removed modules is significant - the module may not be pulled off the fibers without effort. In this case, do not pull too hard, as stretching can affect the attenuation of the fibers in this place, even if the fibers do not break. You should bite and remove the module in 2-3 steps, in parts and slowly.
When cutting the cable, pay attention to the length of the fibers. It must be at least as indicated in the instructions, usually 1.5-2 meters. In principle, it can be cut into 15 cm and then even somehow welded, but then when the fibers are laid in a cassette, big problems: a large supply of fibers is needed just so that there is room for "maneuvers" when laying, so that you can "play" along the length and beautifully lay all the fibers into the cassette.

Sometimes it becomes necessary to weld into a transit cable without cutting it. In this case, it is cut to modules, just like a usual one, but the requirements for the caution of cutting are stricter: after all, a connection can already go through the cable. It is cut to the modules and the modules are carefully inserted into the “oval” input of the coupling (they will not fit into a regular round one - they will break), for this input a special set of heat shrinkage and metal clips with a hot glue block is used. This glue shrinks from high temperature melts and fills the space between the two cables, ensuring a tight seal. Further, the module into which it is necessary to weld is cut, those fibers from it that do not need to be soldered are welded back in transit, and those that we need are welded to the sealed (branching) cable. Very rarely, a situation may arise when we need to take a fiber from a module, but it is impossible to cut the module (there is an important connection through it). Then apply kit for longitudinal dividing of modules: a "chamfer" is removed from the module, the fibers are extracted from it, wiped from the hydrophobic and sorted. Those that we need are cut and welded to another cable according to the scheme, and the rest are simply placed in a cassette. In this case, if a continuous cable is started, the length of the fibers should be twice as long (2-3 m), this is understandable.

The fibers must be clean (thoroughly wiped free from hydrophobes), special care should be taken to ensure that all fibers are intact. Fibers require careful handling, because in the case when the cables are cut and wound, the welding is almost finished and some fiber breaks at the exit from the cable, you will have to re-cut the cable and welding, which will take a lot of time and is extremely undesirable and unprofitable when the connection is restored promptly on the existing highway.


Optical fibers damaged as a result of careless cutting of the cable (the length of the stripper blade was incorrectly set to remove the inner sheath of the cable, as a result of which the modules were cut through and some of the fibers were damaged)

G) The fibers should be wiped well with lint-free wipes and alcohol to completely remove the hydrophobic filler. First, the fibers are wiped with a dry cloth, then with cloths soaked in isopropyl or ethyl alcohol. This is the order because a huge drop of hydrophobic remains on the first napkin (alcohol is not needed here), but on the 4th-5th napkin, you can already call for alcohol to help it dissolve the remains of the hydrophobe. The alcohol from the fibers evaporates quickly.

Used napkins (as well as scraps of cable sheaths, chipped fibers and other debris) must be cleaned up after yourself - have mercy on nature!
The cleanliness of the fibers, especially towards the ends, is of great importance for a quality splicing. Where there is work with microns, dirt and dust are unacceptable. The fibers should be inspected for the integrity of the lacquer coating, the absence of dirt, broken parts of the fibers. If the varnish on some fiber is damaged, but not yet broken, it is better not to risk it and re-cut the cable. Spend 10-15 minutes, otherwise you risk spending the whole day.

H) On the cut cables, special adhesive heat shrinks are put on, which are often included in the coupling kit (if the coupling is with a branch pipe for cable entry). If the sleeve provides for clamping the cable in wet rubber with a sealant, then heat shrinkage is not needed. A very common and very unpleasant mistake for a beginner is to forget to wear a heat shrink! When the sleeve is welded, the heat shrink slides over the sleeve sleeve and shrinks gas burner, blowtorch or industrial hair dryer, providing a sealed cable entry into the sleeve and additional cable fixation. It is most practical to sit down with a small burner put on a can of tourist gas with a price clip: one can is enough for dozens of welded couplings, it simply ignites, unlike a blowtorch, weighs little, there is no dependence on electricity, unlike an industrial hair dryer.
Before shrinking, the coupling branch pipe and the cable itself must be sanded with coarse sandpaper for better adhesion of the glue. If you neglect this, you can get the following misunderstanding:

If you still forgot to wear the heat shrink, a heat-shrinkable cuff with a lock (known as XAGA) will help. It is impossible to collective farm sealing with duct tape!
Some heat shrinks (for example, from Raychem) are covered with dots of green paint, which turns black when heated, indicating that this place does not need to be heated anymore, but here it is necessary to warm it up again. This is done because the heat shrinkage can burst if it is overheated in some place.
It is better to sit down after the coupling is welded. If a trouble occurs during welding (for example, a fiber breaks and you have to re-cut the cable), then you don't have to pick through the frozen thick adhesive heat shrinkage with a knife, and the heat shrinkage itself will not be wasted.

I) The stripped cables are inserted into the sleeve or cross, fixed, and the sleeve or cross is fixed on the work table. When fixing the cable in the coupling or in the cross-section, you should follow the installation instructions - for different couplings everything is different there In some cases (armored cable and, for example, the MTOK A1 coupling with the appropriate input kit), the cable fixing in the coupling is separate difficult operation with trimming of armor, winding of sealant, etc.

So we brought the cut cable into the sleeve / cross, now we need to measure and strip the fibers, put on KDZS and cook according to the scheme. I will talk about this in the next part, since it turns out to be a bit too much for one article.

Optical couplings

I'll tell you a little about optical couplings and crosses. I'll start with the couplings.

An optical coupler is a plastic container into which cables are inserted and connected there. Earlier, in the late 90s - early 2000s, when all specialized materials for optics were in short supply with exorbitant prices, some nimble guys sculpted sewer fittings as couplings or plastic bottles... Sometimes it even worked for several years. :) Today it is, of course, wildness, normal couplings can be bought in any medium and large city and prices start from 1500-2000 rubles. There are many designs of couplings. The most widespread and familiar design for me personally is like a series of svyazstroydetalevsky MTOK couplings. There is a headband, from which nozzles for cable entry stick out from the outside. A metal frame is attached to the inside of the headband, to which optical cassettes are attached. A cap is put on top (which for strength can be made with stiffening ribs), sealed with an elastic band. The cap is fixed with a detachable plastic clamp: the coupling can always be opened and closed without spending a repair kit made of heat shrinks.

In general, Svyazstroydetal makes generally good couplings for different applications... From the MTOK series, I personally like the L6 clutch most of all: universal, inexpensive, easy to install.

There are other couplings in the MTOK series - small-sized, for sewerage, for entering armored cables, for burying underground. For each coupling there is an opportunity to purchase additional accessories and kits for cable entry: for example, cast iron armor protection of the underground coupling "MCHZ", an extra set of optical cassette with consumables or an additional kit for inserting one more cable.
If you need cheaper, they have a series of MOG couplings, of which the most popular is the MOG-U coupling (Optical City Coupling, Shortened): at a price of less than 2,000 rubles, we get a simple and high-quality coupling, which, however, some believe inconvenient for installation.

On a pole, such a sleeve will not look very good, and it is inconvenient to wind up a supply of cable with such a sleeve while standing on a ladder, so they are usually placed in hatches. This clutch is designed to be placed in a telephone hatch on special standard consoles. The disadvantage of the "mogushka" is that it does not have a shut-off detachable clamp and to open it you will have to cut off the heat shrinkage, and when closing it, spend a repair kit made of wide heat shrinks (if the cables are wound from one end) or a heat-shrinkable cuff (if the cables are on both sides). MTOK series A suffer from the same.In addition, if cables are inserted from both sides, it is important not to forget to put on plastic pipe on one of the "sides" of the cables, otherwise you will not be able to put it on without cutting it: beginners also suffer from this.

Also, sometimes there are couplings without branch pipes, in which the cables are sealed by clamping in raw rubber or in a sealant. For example, here is the SNR-A coupling, which my partner and I welded together as part of the construction of the FTTB ring.

This method of sealing cables requires great care, since otherwise water can get into the sleeve, which is undesirable. Firstly, the water in the sleeve over time can cause clouding of the glass fibers and deterioration of the varnish. Secondly, all metal structural elements will rust, the grounding wire, if any, will rot. Thirdly, the kevlar will pull the water over itself. And most importantly - the clutch, full of water, in cold weather it will simply crush along with the fibers.
At least two cables are usually inserted into the optical coupling. Of course, you can come up with a wild welding scheme, when one cable will be inserted and welded onto itself, but usually 2-3 cables are inserted. If 4-5 cables are introduced, and even all the cables are different with different colors and different numbers of fibers in the modules, then the coupling turns out to be difficult for installation and subsequent parsing of what is soldered where. I cooked my first such clutch with my partner for 3 days! :) So it is better to design the network so that more than 3 cables are not included in the sleeve.

Optical crosses

The optical distribution frame is designed for terminating the cable in the place where it was brought in: at the base station, in the ITC, in the data center, in the server room. A typical distribution frame is a 19 "metal box for mounting in a standard rack, a terminable cable is inserted into it from the back, and there are brackets with ports in the front.


Welded 24-port FC / APC frame, single-unit

Welded crossbar for 64 ports, LC type, 2-hunit

Working cross for 96 ports of FC type

There is also a cheaper option - when everything that is possible is thrown out of the cross, then it turns out something like this:


Open cross-section for 8 ports, SC / APC type, 1 unit. The bad news is that the optical pigtails are not protected by anything and they can be broken by those who dig in the box / rack, pulling, say, a new cable.

All of these crosses are rack-mounted, but there are wall-mounted options and others that are rare.


16-port wall distribution frame, FC type. By the way, it is badly welded: the yellow pigtail shells do not enter the CDZS and the fibers can break, and the fibers in the cassette are laid with small bending radii

The cable inserted into the crossover is welded with the so-called pigtails: in the photographs, these are thin yellow laces inside the crosses. Each fiber goes to its own pigtail. The other side of the pigtail contains an optical connector-"plug", which is inserted into the optical adapter-"socket" from the inside of the chassis. Outside the chassis, switching is performed by optical patch cords (thick yellow cords). The patch cord differs from the pigtail in a more durable connector and the presence of Kevlar inside, so that in case someone gets caught on the patch cord and tugs, it would be difficult to pull out. Well, the patch cords have connectors on both sides, while pigtails have only one. If necessary, a temporary patch cord can be welded from the two pigtails.

In principle, several cables can be brought into the cross, some of the fibers from them can be welded together, and some of them can be brought out to the ports. Then you get something that can be called "cross-coupling", while we save on materials and welding. This is sometimes done when installing FTTB, but it is undesirable to do so, since the complexity of the circuit increases.

Adapters and connectors

Optical distribution frames are characterized by the adapters used in them (more simply - optical sockets). They also exist a large number of standards and substandards.


This picture shows only a part of the "genera" and "types" of optical sockets.

The standard is a set of adapter (socket) and connector (plug). Of course, there are adapters between different standards, but these are crutches that are suitable only for measurements and which should be avoided in a constantly working communication line. The less in the line of all kinds of welded and especially mechanical joints, the better. Of course, if the distance is small, the line will work even if a couple of decibels are lost on some of the crosses. In the case of short lines, optical attenuators are sometimes specially installed. But for very long lines, where the equipment is working at its limit, adding another cross or coupling (that is, some 0.05-0.1 dB loss) can be fatal: the line will not rise.

The tip of the "fork" is, roughly speaking, a cylinder with a thin fiber through hole in the center. The end of this cylinder is not flat, but slightly convex. The tip consists of an awesomely hard and destructive scratch-resistant cermet, although metal is very rare. Rumor has it that people have broken side cutters while trying to bite through this tip. :) I myself easily scratched steel and glass with these tips. Nevertheless, they must be handled carefully, do not allow dust to enter, do not touch the end of the connectors with your finger, and if touched, wipe it with a napkin moistened with alcohol. Ideally, a special microscope (optical or with a camera) is used to monitor the condition of the patch cords. Dirty - clean, scratched, if the scratch crosses the center with glued fiber - for disposal or polishing. Dirty and scratched outlets and patch cords - common reason attenuation in the line.
The optical fiber is fixed in the tip by gluing it in with epoxy (or some other) glue and then grinding it on a special machine, although this is done only if you need to make long non-standard patch cords: it's easier and cheaper to buy ready-made ones. The price of a conventional optical patch cord 2 meters long is about 200-400 rubles.


Manufacturing of patch cords. Emilink

In practice, the most commonly used standards are FC, SC, LC. Less common are FC / APC, SC / APC, ST. LC comes in both duplex and single.

FC

Pros - excellent connection quality, therefore it is suitable for critical highways. An old proven standard. Metal (hard to break). If you move your hand on a well-screwed connector, this will not affect the connection.
Cons - to twist / twist for a long time when switching. If they are closely spaced on the cross, it can be very inconvenient to crawl in order to unscrew one of the connectors in the crowd of others.
The connector itself is fixed motionlessly thanks to the groove on it and the notch on the adapter, and only the knurled nut rotates with your fingers.

SC

Everything is the same as in FC, only the adapter and connector are square, plastic and the connector is fixed by clicking, and not screwing. Pros - cheaper FC, more convenient and faster to switch, cons - plastic is easier to break, less connection-disconnection resource. Sometimes it happens that the amount of reflection and attenuation on the connection changes noticeably after touching the connected connector, which is undesirable for critical lines. The color of the connectors is usually blue.

LC and LC Duplex

They are similar in properties to SC, but have much smaller dimensions: a two-unit distribution frame on LC accommodates as many as 64 ports, and on SC - only 32. Due to its small dimensions, they are often mounted directly on boards of optical multiplexers.

FC / APC, SC / APC, LC / APC

Same as FC, SC and LC, but with oblique (A - angle) polished tip.


Difference between normal and oblique ceramic tips. The image is a little inaccurate: in fact, in the case of both polishing, the ends are not flat, but slightly convex, respectively, when joining, only the centers of the tips will touch, where the fiber is.

Such adapters and connectors are made Green colour and when compared with conventional polishing UPC (or just PC), the difference is visible to the eye. This is to reduce back reflection at the junction of two connectors. As far as I know, this type of polishing was developed for the transmission of analog television via optics, so that ghosting does not occur on the screen, but I could be wrong.
It is possible to dock with each other "normal" and "oblique" polishing, but only if it is necessary to take an OTDR trace according to the principle "if only the length of the path is visible": a large air gap will give strong losses and strong back reflection.

For today my story is over. Ask questions, I will try to answer. If this topic turns out to be interesting to you, I will write a sequel.