Thursday, April 30, 2015

Welding of optical fibers.: Cables and cutting, optical instrument, couplings, crosses, connectors and adapters

The fibers are loaded in the welding machine

Hello readers ! Everyone has heard about the optical fibers and cables. No need to tell where and for what uses optics. Many of you will encounter it at work, someone develops the transmission network, someone who works with optical multiplexers. However, I have not met the story about the optical cables, couplings, crosses, about the technology itself, and splicing cables. I - fitter of optical fibers, and in this (his first) post would like to tell and show you how it all happens, and often in his story will be distracted by other things related to this. I will rely mainly on their experience, so I fully admit that someone will say "this is not quite right," "here uncanonical."
Stuff happened a lot, so it was necessary to split the topic into parts.
In this first part you will read about the device and cutting a cable, about an optical instrument, about the preparation of fibers for welding. In other parts, if the topic would be interesting to you, I will discuss the methods and will show on video the process of splicing optical fibers themselves, about the basics and some of the nuances of measurements on optics, touch on welding machines and OTDR and other measuring instruments, show jobs fitter ( roofs, basements, attics, hatches and other field offices), tell a little about the fastener cables, wiring diagrams about, about the placement of equipment in telecommunication racks and boxes. It is certainly useful to those who are going to become fitter.




Network Technology *IT Infrastructure *

The fibers are loaded in the welding machine


Hello readers Habra! Everyone has heard about the optical fibers and cables. No need to tell where and for what uses optics. Many of you will encounter it at work, someone develops the transmission network, someone who works with optical multiplexers. However, I have not met the story about the optical cables, couplings, crosses, about the technology itself, and splicing cables. I - fitter of optical fibers, and in this (his first) post would like to tell and show you how it all happens, and often in his story will be distracted by other things related to this. I will rely mainly on their experience, so I fully admit that someone will say "this is not quite right," "here uncanonical."
Stuff happened a lot, so it was necessary to split the topic into parts.
In this first part you will read about the device and cutting a cable, about an optical instrument, about the preparation of fibers for welding. In other parts, if the topic would be interesting to you, I will discuss the methods and will show on video the process of splicing optical fibers themselves, about the basics and some of the nuances of measurements on optics, touch on welding machines and OTDR and other measuring instruments, show jobs fitter ( roofs, basements, attics, hatches and other field offices), tell a little about the fastener cables, wiring diagrams about, about the placement of equipment in telecommunication racks and boxes. It is certainly useful to those who are going to become fitter. All this I arch a lot of pictures (I apologize in advance for the paint-quality) and photos. Beware, a lot of pictures and text.



Entry

To begin with a few words about me and my work.
I work fitter optics. He started with a telephone operator and installer, and then worked in the emergency team in serving the main optics. Now I work in an organization that takes the general contractor for the construction of communication lines among different companies. A typical construction project - cable line connecting several containers of base stations GSM. Or, for example, several rings FTTB. Or something smaller - such as cabling between the two server on different floors of the building and the splicing at the ends of the cable crossover.
If the tender is won, looking for a suitable sub-contractors performing work (design and survey and construction). In some regions, it is our subsidiaries, some have their own equipment and resources, some hired an independent company. On our own shoulders rests mainly control, elimination of stocks of various subcontractors and force majeure, every agreement with landowners and administrations, sometimes drawing up the executive documentation and other constructed facilities. Often the need to work with optics: cook or digest somewhere optical coupling or cross, eliminate the effects of street racing knocked supports or fallen tree on the cable, hold the input control cable drum, to remove the trace section and so on. These are tasks I perform. Oh, and incidentally, when there is no problems in optics - other tasks from loading and installation via Express-haul to copying paper work. smile.gif



Optical cable, its types and entrails

So what is a fiber optic cable? The cables are different.






 At the point of use - for exterior and interior linings (last rare and typically in data centers high-end, where everything has to be perfectly correct and beautiful). Under the terms of the gasket - Suspension (with Kevlar or cable) to ground (armor of iron wires), for installation in cable ducts (with corrugated metal armor), underwater (complex sverhzaschischayuschaya sandwich construction), for hanging on electric poles (except for the transfer of information vyponyayut role of lightning protection cable). In my experience, the most frequent suspension cables on poles (with Kevlar) and for laying the ground (with armor). Seldom come across a rope and gofrobronёy. More common cable that is essentially a thin coaxial optical patch cord (yellow envelope in singlemode and orange - in multimode, and one bit of Kevlar fiber, the two shells are paired). Other optical cables (without protection, underwater, for installation in the premises) - exotic. Almost all of the cables, with whom I work, have a structure like the one below.


1 - central strength member (in other words - from fiberglass rod, although it may be wire in polyethylene covering). Used for centering tube modules, giving rigidity around the cable. For it is also often fixed cable coupling / cross-country, clamping screw. With strong bending of the cable has a break sneaking property, breaking and passing a part of the fiber module. More advanced cable design contain this bar, wearing a plastic shell: while it is more difficult to break and damage the cable when it is the turn will cause less. Bars and is the same as in the figure, and very thin. The tip of the bar - a great tool for fine abrasive work, for example, to clean relay contacts or a portion of the copper solder parts. If it burn for a couple of centimeters, you get a nice soft brush. smile.gif
2 - the optical fibers themselves (in the figure - in lacquer insulation). The very finest threads, fibers, for which all afoot. In this article we will speak only about the glass fibers, although somewhere in nature, there are plastic, but they are - great exotic, not cooked devices for welding optics (only mechanical connection) and are suitable only for very short distances and I personally did not face them . Optical fibers are single-mode and multimode, I have met with only single-mode, multimode since - outdated technology, it can only be used for short distances and singlemode perfectly replaced. The fiber consists of a glass "shell" made of glass with certain impurities (in chemistry and crystallography will not stop there, because they do not know the subject). Without varnish fiber has a thickness of 125 micrometers (slightly thicker hair), and in its center there is a core diameter of 10 microns high purity glass of different composition and slightly different from the cladding refractive index. It extends the core radiation (due to the effect of total reflection at the "core - shell"). Finally, on top of a 125-micrometer Cylinder "shell" covered by another shell - from a special varnish (clear or colored - for color-coded fibers), which is also a dual-layer EMNIP. It protects the fiber from moderate injuries (without varnish though fiber bends, but bad and easy to break, the fiber elementary crumble from a random position on his mobile phone; and the varnish can be safely wrapped around a pencil and pull strongly enough - it will stand). It happens that span cable slack on some fibers: broke (perezhglo, cut) all shell Kevlar burst central rod, and some 16 or 32 125 micron glass fiber can span weeks to keep the weight of the cable and wind loads! Nevertheless, even in the lacquer fibers can be easily damaged, so the fitter of the most important - the meticulousness and accuracy. One awkward movement can ruin the results of a day of work or, if not particularly lucky and there is no backup for a long time to drop the trunk link (if, digging in "combat" the main clutch, break the fiber DWDM-th under the spine at the outlet of the cable).
Fiber is a lot of varieties: ordinary (SMF or just SM), with dispersion shifted (DSF or just DS), a non-zero dispersion shifted (NZDSF, NZDS or NZ). Outwardly, they can not distinguish the difference - in the chemical / crystalline composition and, probably, in the geometry of the central core and the smoothness of the boundary between it and the shell (unfortunately, for themselves and do not clarify the matter before the end). Dispersion in optical fibers - a harsh and difficult to understand a thing, worthy of a separate article, so easy to explain - for dispersion shifted fiber can transmit a signal without distortion more than in the simple. In practice, the fitter know two types: simple and "with smeschёnkoy." The cable is often isolated the first module under the "smeschёnku" and the rest - a simple fiber. Docked "smeschёnku" and a simple fiber can be, but is not desirable, it is an interesting effect, which I will discuss in another part, about the measurement.
3 - plastic tube modules, which float in the hydrophobe fiber.
The cable to the split modules





 Optical fibers, damaged as a result of careless cutting a cable (was wrongly exposed blade length stripper to remove the inner sheath, causing erupted modules and damage of the fibers)




 In this picture - only a part of the "birth" and "species" optical sockets




 Wall cross-type 16 port FC. By the way, cooked badly: yellow shell P & G-Tail not enter the CRSS and fibers can break, and the fibers are laid in the cassette with small bending radii.



 Work on the 96 cross-type FC ports




Often option and cheaper - when thrown from the cross all that is possible, then it turns out something like this:

  Reduced: 93% of the [731 to 355] - Click to view full image
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Open cross 8-port type SC / APC, 1 unit. Worse what P & G optical-Tail are not protected and they can break those who will delve into the drawer / front, dragging, say, a new cable.



All these crosses are mounted in a rack, but there are options for wall, and other rare.











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