TTL Fluctuation Caused by Abnormal Optical Power in the DWDM System

The TTL fluctuates because the optical power of the DWDM system is abnormal.

Product

OptiX BWS 1600G

Fault Type

Other

Symptom

On an OptiX BWS 1600G ring network, the TTL of the Ethernet services received from an Ethernet test meter fluctuates. In normal cases, the TTL should be fixed at 5 ms. The test values are listed as follows:

TTL = 5 ms

TTL = 113 ms

TTL = 223 ms

Cause Analysis

• The signals at the remote station is excessively weak.
• The fiber is faulty.

Procedure

1. Clean all the fibers at this station, reconfigure the EPL services, and/or replace the Ethernet cable. It is found there is little effect.
2. This problem may be caused by excessively weak signals at the remote station. In this case, make a call to the NMS operation center (NOC) and ask them to check the optical power at the remote station and check whether there are bit errors at the remote station. After confirmation, it is found that the power at the remote station is excessively low and bit errors in the data exceeds the permissible range. Thus, it is determined that the attenuation on the line is caused by the fibers at the remote station.
3. Replace the fibers, the optical power at the remote station is recovered, and the ITL at the remote station becomes normal, that is, it remains at 5 ms.

Reference Information

Whenever you test a DWDM system, bring the fiber cleansing tool, fiber jumpers, and optical power meter with you.

Pay attention to the optical power, BER, system performance, and the like system indexes. Power decrease and bit errors are related to each other. For example, if the power does not meet the specified requirement, bit errors will be generated; if the fiber jumpers are of poor quality, signal degrade and a large number of bit errors will occur.

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