2021-02-24

Fibre cable

As I have have whinged on about for some weeks now, I have a fibre to the new house here.

What I have is an Etherway which is a glass fibre run to the exchange where it is then logically connected back to another Etherway in London in to one of our data centres where it then connects to the Internet.

I had a fibre to my old house, and in those days they ran a "fibre tube" and then "blew" fibre down it (compressed air). These days they use "fibre cable". The engineers say they prefer fibre tubes.

But what is fibre cable?

Well, it looks pretty boring, 6mm black hard cable, with a fetching yellow stripe down the side :-)

Inside it looks slightly more interesting...

As you can see, there are some steel wires for strength - allowing it to be pulled, and even strung overhead from poles. It has the red fibre stuff, which I assume is also for strength (anyone got any other suggestions), and a white tube which contains the actual glass fibres, and some gel.

This fibre cable has 4 fibres, colour coded with some coating which can be stripped off easily.

And basically, that is it - fibre optic glass (which is two layers of glass of different densities) covered in a colour coded coating, in a gel filled tube, in a strong black cable. Simples

Apparently this is not how you terminate fibre though :-)

The engineers have splicing equipment so they can splice a tail with standard plugs on to the end of the fibre, and joint it as needed underground to get to the exchange.

13 comments:

  1. The red threads are indeed kevlar type aramid for strength. The coating on the fibre itself is PVC, as it is easy to remove.
    You need some seriously special equipment to terminate single mode fibre, as you need to polish the end to micron accuracy is a special convex shape. It's much easy to make the connector in a factory and then splice the fibre.

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  2. The red fibrous elements are packing - the theory goes that with a stiffer white fibre tube and the softer fibrous elements, the white tube can shift around inside the black outer, and take the gentlest possible curve as the soft packers move out of the way.
    That's the theory, anyway. Not sure how much of a difference it actually makes :-)

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  3. With the Etherway product do you get a single optical path from your house all the way to London or is it converted back to electrical in the exchange and then multiplexed onto another fibre at different frequencies for the trip from the exchange to London?

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    1. Optical to exchange, and then over something like MPLS (Etherflow) at purchase speed to another Etherway. Can be multiple Etherflows to different Etherways in different places on different VLANs if I want.

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  4. Re the 'blown fibre tubing' Back in 2017, I think, I had a BT technician tell me that their kit connects at both ends of the installed tube and evacuates the air, creating a vacuum, of course. And then the kit at the customer premises end 'sucks' the fibre through the air-less tube. So, sucks, not blows. Innuendos not intended.

    More seriously - that's why none of our fibre joints work. We've been crimping the glass fibre strands into RJ45 plugs for 10 years. Dammit.

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    Replies
    1. I definitely saw it being blown, with compressed air. Maybe there is more than one way it is done.

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    2. I suspect you are right. And that my BT technician on that day was wrong. I doubt that many BT workers actually understand what they are doing. Perhaps 1% understand the tech they are touching. It is called "blown" fibre tubing after all. It isn't called "sucked" or "vacuumed" fibre tubing, is it?

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  5. We all need to get away from calling BT's van-driving people 'engineers'. They aren't. Engineers have degrees. Engineers design sytems and specifications and take responsibility for design details. Technicians merely follow those instructions on the ground, have no design responsibility and no liability if the system doesn't work. All BT/Openreach operatives who come to your house/office are technicians and are not engineers. Despite what BT may try to claim. A frustrated rant. Engineers and technicians are a million miles apart.

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  6. If you ever do research and write-up the various different types of fibre, their terminations, specifications and so on then it will be very interesting. Find various resources online but none of them give a full picture. It will soon be very important that domestic and commercial IT installers get familiar with fibre and copper becomes less relevant.

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    1. Definitely. You'll do a fantastic job of identifying the exact standards, products and methods and the best tools for the job.

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    2. And then they'll ignore RevK, use poor tools, and do a bad job (but they'd do that even with good tools).

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  7. Did the "engineers" say why they prefer fibre tubes? There is probably a healthy dose of preferring what they are familiar with, so I'd like to know of any genuine technical reasons.

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