How do I validate my fiber network?

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Oct 24th, 2008
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How do I validate my fiber port cabling when using the following Cisco transceivers?




I want to develop a test to prove the “Lines” are good, poor or ugly, poor meaning the cabling has problems, too much attenuation because of bad splices, etc.

I've found one document “OL-5067-05” that deals with Transmit Power, Receive Power and Power Budgeting for these GBIC and SFP modules. But how can I apply these values to my faculties, which is maintained by someone else? My faculties

are world wide and I'm wondering about "Marginal" installations that might happen.

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michandrz Fri, 10/24/2008 - 20:18
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you could test all your lines with an OTDR (fancy term for fiber meeter) there a bit costly but a handy tool to have. I recommend the fluke DSP series but they have been retired and have a replacement out, sorry i cant recall the replacement model

scottmac Sat, 10/25/2008 - 05:51
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An OTDR (Optical Time Domain Reflectometer) Will tell you how long the fiber is, within a certain resolution (frequently to the closest meter, some will do half meter) ... and is useful for finding the approximate location of a break, or the length of the run.

For quality measurements, you'd use either a calibrated source and power meter and/or a Optical Spectrum Analyzer.

When the fiber is/was installed (if it was installed by a professional), they do a power measurement for the span and record & report it to the consumer.

With your own source & meter, you can compare the original reading to "what you got now" and determine if there is a significant degradation (dirt, crud, break, tight bend, etc).

With a spectrum analyzer, you can see how much spectral dispersion your span is producing and the basic quality of your pulse train / signal.

Sometimes several functions are integrated into a single device (JDSU does this, Fluke probably does too)

Another useful tools is a Visual Fault Locator, which puts a very bright red light down the fiber. When the light hits a break, it scatters the light and you see a red blip from the fiber's sheath.

Good Luck


fjcardenas-1 Tue, 10/28/2008 - 09:03
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Review the optical power characteristics of the optical transmitter and receiver in the Manual of the interfaces or equipment. Usually there is a RX power range (Minimum - Maximum). Connect a Power Meeter to the other end of the fiber and verify if the receiving power is within the range. If it is you are fine. I would recommend to use an attenuator to set the RX power to the middle of the range. Do the same thing for the other end.


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