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TOA STM-16 B1 Error and Frame Alignment Error Due to Wrong SFP Type

Publication Date:  2012-07-25 Views:  248 Downloads:  1

Issue Description

There are 8 x STM-16 services have been configured by trail method over one TN54TOA01 at customer lab testing platform here. 4 x STM-16 are mapped into one OTU2 (TN53ND201) facing East side FOADM (at Lambda 6) and another 4 x STM-16 are mapped into another OTU2 (TN53ND201) facing West side OTM (also at Lambda 6). Please kindly refer to attached network topology illustration page 2. When the SDH Analyzer is turn on, there are intermittent B1 errors and FAS error. At the beginning, it is doubt that this problem occur due to the IN_PWR_LOS reported by the ND2 at ROADM. However, after the IN_PWR_LOW has been resolved, the same intermittent B1 & FAS has been reported by SDH analyzer. Then, suspecting that this might be due to the capability problem of TOA, therefore, the number of the STM-16 has been deleted at both direction, making the total of the STM-16 from 8 to 6. However, this doesn't solve the problem. This prpblem remain the even the total number of the STM-16 has been reduced to one at both respective direction.

The OSN8800 (T32) plaltform is (V1R6C01SPC200) and the U2000 version is V1R5C00SPC200.

Alarm Information

Besides of the B1 and FAS error at SDH Analyzer, the alarm information retrived from U2000 are RSBBE and RSES which are reported at both ROADM and OTM side STM-16 service. Please refer to attached network topology illustration page 3.

Handling Process

After checking all of the other ND2 line and TOA port optical power normality, and also the TOA service mode, there are no problem with that. Then, the FOADM STM-16 is connected directly to SDH Analyzer, and physically loopback at ROADM side, the B1, FAS, RSBBE & RSES problem are cleared. But, when the same test is repeated at ROADM-OTM section, the B1 & FAS error occur again. Then, the problematic part is identified. The physical fiber are checked and thera are good, when the SFP at ROADM is taken out and check, apparently the SFP module used is for GE (1.25G) NOT the ANY rate SFP from 155 M to 2.75 G as used by other ports. After, the GE SFP is replaced by the ANY rate SFP, the B1, FAS , RSBBE & RSES errors are all cleared.

Root Cause

Please refer to Summary.


Usually, when there is bit errors or frame alignment reported but without any LOF alarms, we will always make the speculation that this might be line side or tributary side abnormal power or fiber high ettenuation that cause the problem. However, the incompatible of the SFP module that doesn't cause the traffic down which comes with LOF at the tributary side will lead the engineer to the wrong direction when doing troubleshooting. In addition, there is NO relevant service incompatible alarm or wrong SFP module alarm reported after the service is configured. In order to avoid similar problem happen, it is suggested that:

1. As precaution step, the U2000 shall be able to display the wrong service configuration error message during the service creation over the wrong SFP/XFP module. And this action deny the service created into SCC.

2. There should be a wrong service / module type alarm reported by the corresponding TOA port when the STM-16 traffic is configured over the wrong SFP module.