BT and leased lines.

Discussion in 'Broadband' started by Martin Lukasik, Apr 21, 2006.

  1. Hi guys.

    Do you know if BT's using singlemode fibers or multimode?
    I thought they are using singlemode, but I saw a MM fiber connected to my
    Then in goes via cupler to some white fiber, but it doesn't say whether or
    not it's singlemode...

    Just wondering.
    Anyone knows?

    Martin Lukasik, Apr 21, 2006
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  2. Martin Lukasik

    jimmy Guest

    What's "fiber" and "cupler" ?
    jimmy, Apr 21, 2006
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  3. Martin Lukasik

    cw Guest

    Easily overlooked typos except to grammar and spelling nazis...
    cw, Apr 21, 2006

  4. A firm of solicitors ;o)
    Keith Willcocks, Apr 21, 2006
  5. Martin Lukasik

    ato_zee Guest

    Generally BT uses monomode to deliver corporate services
    (5/125 is common, nowdays it may be blown fibre)
    and they charge an arm and a leg for
    their NTU with battery backup - UNLESS - they are quoting
    against C&W or Telewest. With blown they can add extra fibres
    and services and repairs are easier that trying to splice
    in a manhole with water lapping over your wellies.
    Their presentation to the user may be multimode or monomode,
    depending on what the customer requests and can accomodate.
    BT's customers premises NTU usually provides BT with
    monitoring capability so that if you report a fault their
    network control center can check the circuit out from
    their end, and create a loopback for end to end testing
    if necessary.
    It is not unusual for the customers fibre transceiver to
    go marginal, the source diodes are run fairly hard.
    There is generally some terminating equipment, like
    a rack card, or box, between BT's fibre and the users
    ato_zee, Apr 21, 2006
  6. What's "fiber" and "cupler" ?

    Sorry master. Coupler and "fibre". It's not my fault I'm not British and not
    my fault that english we learnt at school was something between British and

    Martin Lukasik, Apr 24, 2006
  7. [..]
    I was wondering, because somebody cut our fibre outside, and as I've noticed
    it was a singlemode fibre (or monomode -- however you call it). But in the
    building we've got multimode fibre.
    I've spoken to BT guy and he told me they're using singlemode and he said it
    only goes to the patch panel at exchange and it doesn't go to any equipment.
    It's just a purely dedicated line.
    So what if I connect my 1000Base-ZX GBIC module, which can do 100kms? Would
    it work?
    I haven't tried in the UK yet, but I tried in few other countries and it did

    Martin Lukasik, Apr 24, 2006
  8. Don't worry, only Jimmy doesn't understand you.
    Colin Forrester, Apr 24, 2006
  9. Martin Lukasik

    ato_zee Guest

    Without knowing what's BT's presentation at your end it's hard to be
    specific. It would be unusual for BT to splice monomode onto multimode.
    It might work ok from them to you (with losses going from monomode to
    single mode) but you would need to launch sufficient optical power to
    overcome the losses going from multimode to monomode, which is
    why it might just work, but is not a preferred solution. A lot depends
    on range. At the exchange the monomode terminates on a patch panel,
    what he didn't say was what the other side of the panel feeds, most
    likely a card, speculatively it could be one of a set of cards that link
    to a multiplexed higher rate circuit.
    BT can bring in monomode and offer you a dedicated circuit to anywhere
    in the world, like your back office in Hong Kong, at a price.
    Or you can split a circuit between voice and data, n by 64k channels
    for the PABX and the rest of the bandwidth for Ethernet.
    There has to be a from/to, how far and does the from/to cross one
    or more exchange boundries? They could just give you dark fibre,
    like the old wires only circuits that you could lease from BT, but
    it would be unusual.
    ato_zee, Apr 24, 2006
  10. but you would need to launch sufficient optical power to
    He came with a funny laser pointer (1mW) and the guy on the other end could
    see the light. Distance in straight line is about 8 miles.
    But I'm not quite sure whether or not they tried to see the light on the
    exchange or the other end.
    Anyway, I've got 1000Base-ZX converters, which can do 100km on a singlemode

    It's about 8 miles in straight line; at least two exchanges, but as I'm
    calculating it will be about 5.
    Can I ask you a stupid question? What is a "dark fibre"?

    Martin Lukasik, Apr 25, 2006
  11. Martin Lukasik

    ato_zee Guest

    Dark fibre is the term for unused fibre, just the fibre, with
    or without any connectors. Like if you put in an 8 or 12
    core fibre, but currently need only a pair, the remaining fibres
    are called dark fibre. Some international routes have
    dark fibre to allow for future expansion of capacity.
    An ordinary torch works quite well if the far end can be
    shielded from direct light. I use it to identify which of a
    pair is which, assuming spliced on tails with ST
    connectors, and you can't determine it from the cable
    itself, often the case with blown fibre. You end
    up with 8 or 16 connectors and have to determine
    which goes to which on a panel, so you get your
    mate on his mobile, and he has a torch.

    Multi-pair fibre circuits are quite common, a pair each
    for Personnel, Sales, Shop Floor or whatever, and you
    need to isolate them from each other with a router, like
    you don't want Sales to be able to access the Payroll
    and see who is being paid what. So that's 3 pairs,
    and a dark pair, if it's an 8 fibre cable. Hospitals are
    the same they have dozens of independent
    ato_zee, Apr 25, 2006
  12. Dark fibre is the term for unused fibre, just the fibre, with
    Thanks for the answer. I will give it a try probably next month when I go to
    data centre.
    Think is worth a try. We've got few leased lines on two fibres, so I can
    connect GBIC modules (RX and TX). New lines work on 1 fibre :-(

    Martin Lukasik, Apr 25, 2006
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