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Optical Modules on the TOM Board Fail to Work Normally

Publication Date:  2012-07-25 Views:  83 Downloads:  0
Issue Description

At a certain office, all the optical modules on the live network pass the sensitivity test during NE-level hardware acceptance. During the system acceptance, however, it is found that a great number of optical modules on the TOM board work abnormally. The fault symptoms are as follows: 

1.  GE module: When a self loopback is configured, the system reports R_LOS and the received power is displayed as �60 dBm.

2. 2.5G module: The sensitivity decreases. After a self loopback is configured, if relatively high attenuation is added, the system reports LOS when the optical power deceases below -6 dBm.

3. 2.5G module: The transmitted optical power is normal, but the received optical power is displayed as “/”. No value of the optical power is found through performance query.
Alarm Information
Handling Process
Add services to the NE or connect the NE to a test instrument that can provide service light.
Root Cause

There are two criteria for inspecting an optical module: loss of signal (LOS) and loss of power (LOP). LOS is used to check whether optical power is present. If certain optical power is present, LOS is not reported. LOP is used to check whether signals exist. No LOS is reported when a service is configured. There is no unified regulation for these two criteria in the industry. Optical module suppliers have not unified the methods of inspecting optical modules.

During NE hardware acceptance, a service is added to the NE in the sensitivity test by using a test instrument. Therefore, the problem is not found in the test. However, when a self loopback is configured on the NE, there is only white light but not service light on the optical port. Thus, even if the system detects optical power, it reports LOS.