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dB loss in Avaya SMF Cabling


We have completed the Large MAN Cabling project at one of the oldest University in India. Following components are used:

1. Avaya SMF 9micro Cables.

2. Avaya SMF LC Connectors.

3. Avaya LC Coupler.

and other Avaya Fiber structured cabling products.

According to Avaya site we have taken following Equation for Acceptance test of this cabling.

Link Attenuation = Cable Attn + Connector Attn + Splice Attn WHERE

Cable Attn (dB) = Attn Coefficient (dB/km) * Length (Km)

Connecter Attn (dB, for LC) = (number of connector pairs * 0.14) + 0.24

Attn Coefficient (dB/km) = 0.4 at 1310 nm and 0.3 at 1550 nm

We are facing following problem:

1. Large variation in dB loss readings for different cores. (Reading varies by 1 to 1.5 dB every time u measure)

2. 40% readings are overshooting the expected reading (As per above formula)

Help Required:

1. Confirmation that weather these formulees are valid?

2. Sample Readings for SMF LC connectorization.

3. General allowed variation in the LC / SMF reading.

Help will be greatly appreciated.

regards....Prakash Somani


Re: dB loss in Avaya SMF Cabling

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If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

Community Member

Re: dB loss in Avaya SMF Cabling

Link Loss formula should be :

Cable Loss + Connecotor Loss + Splice Loss + Coupler LOss

Note 1. IF the Connecotrs were spliced on a loss of 0.30dB is typical

Note 2. Splice loss should be calculated at 0.10 dB per splice

Note 3. Coupler loss is approx 3.5 dB for a 50/50 split

Make sure the test equipment is referenced correctly and do not change the test jumpers.

The test set up should be

TX----------------cc-------------------RX c=connector

zero this out and begin testing

hope this helps

Community Member

Re: dB loss in Avaya SMF Cabling

I would only add one point.

Give the optical source time to settle down.

If the environment is optimal, it will still take two or three minutes for the source to warm up and stabilize. In a bad environment, it could take seven minutes for the source to emit a consistent signal.

Good luck!

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