End-End Fiber Testing

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Sep 30th, 2009
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I have a single mode fiber between two sites less than a mile apart.




I need to test for power loss and check health of the fiber end-end. Is there anything specifc i will need to check for? The fiber was installed about 10 years ago and just need to work out how reliable the fiber is?


normally on single fiber what should i expect to see for db level?

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viyuan700 Wed, 09/30/2009 - 05:50
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If the distance is just a mile away should not be any problem unless their is any imperfection in the fiber.


Fiber loss at 1330nm is 0.3-0.4dB/Km and at 1550nm 0.2 to 0.25dB/Km. Add 2-3 dB splice & connector loss. If your loss us more than 3-4dB on this link then you can see with an OTDR if their is any break.


But OTDR is a costly instrument so first you can check just with a power meter if that gives you a high loss than you can think of other measurement.





francisco_1 Wed, 09/30/2009 - 06:13
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Vishwamurti,


so i should expect to see normally for 1310nm 0.3-0.4dB depending on the distance and 1550nm 0.2 to 0.25dB also depending on the distance? if i get a higher db level say 3-4dB, is that acceptable?

is my understanding correct?


viyuan700 Wed, 09/30/2009 - 06:30
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or 1310nm 0.3-0.4dB depending on the distance and 1550nm 0.2 to 0.25dB also depending on the distance


Yes this is the fiber loss you just multiply by distance.


Apart from it you have splice loss which occurs when you join two pieces of fiber length IT depends on how good the splicing was done.


When you will connect a connector to a power meter that will also have some loss.


I was considering all those losses in that 3-4dB. So if you get that kind of loss i think should be fine.


Your distance is so small for a single mode fiber even though it is 10 year old .Even if you want to go for 10G on this fiber i think you will not have any problem unless their is cut or something.


Do you have idea what speed are you considering on this link? Have you decided on what card you want to use.

francisco_1 Wed, 09/30/2009 - 06:44
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switches have 10/100 interface so no more than 100mb.


Lastly as an example to clarify by understanding, so to work out the loss say the distance is 1 mile = 1.6km and the loss is 0.3 (taken in to consideration the connector and splice db losses as well!). do i multiply 0.3db by 1.6km = 0.48?

viyuan700 Wed, 09/30/2009 - 06:54
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do i multiply 0.3db by 1.6km = 0.48


Yes you have to multiply. Actually these are the general loss figure for single mode fiber. If you need specific for your cable then see if you have any manual of your cable.


100Mb optical port (SFP) for single mode fiber can go 10Km. So i think should go 1.6Km without any problem.

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