fibre optic cable

Unanswered Question
Feb 6th, 2009

Hi all, with fibre optic cable, is it possible to have a faulty or degraded signal through it? or would it be either on or off ?

I have this problem too.
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Giuseppe Larosa Fri, 02/06/2009 - 11:33

Hello Carl,

it is possible to have a fiber link with a degraded signal.

A good link has a BER (bit error rate) of 10^(-9).

the capability to correct an isolated error used with the linecodes help to improve the performance but when errors come in bursts this is not possible anymore and error rate can be high.

Given a modulation scheme it is a question of noise margin alias Signal to Noise Ratio if BER can be acceptable or not.

A bended fiber introduces attenuation.

Other factor is modal dispersion that is the limiting factor for multi mode fibers.

Hope to help

Giuseppe

Hope to help

Giuseppe

viyuan700 Fri, 02/06/2009 - 18:02

apart from bending losses you can have dirty/faulty patchchords, the link length is greater than the allowed length. Length is limited by signal power, dispersion, at 40G Polarization Mode Dispersion.

Dispersion is there in Single Mode Fiber but it is not as much as in Multimode Fiber.

If the loss is due to crack in cable then most probably only Off.

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