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Improper threshold of IPA lead to service interruption

Publication Date:  2012-07-25 Views:  35 Downloads:  3
Issue Description

Topology like this :

A-B-C

Normally, when link between A and B has broken, the service between B and C should be normal . But this time, all of the services down , so now the problem is why service between B and C interrupt .

Detail information about this network please see the attachment .

Alarm Information

OTS-LOS-P in FIU

MUT-LOS in OAU

Handling Process
  1. Check the link ,we find the first alarm on this link is C 1-FIU have a OTS_LOS_P alarm.
  2. Check C 11-OAU board, it have LOS alarm
  3. Check C 1-FIU input power, before link down is -3dBm, after link down is -10.2dBm
  4. Check B 206-OAU output power, before link down is 19.7dBm, after link down is -11.9dBm
  5. Check the cable loss, the cable between B and C totally loss 37.3 dBm
  6. Increase the Gain in B 206-OAU, change the value from 23dBm to 25dBm then service recover

Before fiber cut--After fiber cut--After increase the gain of B site

B OAUIN:-3.3-------------11.4-----------11.4

OUT: 19.7----- -------- 11.9----------- 13.7

C 1-FIUIN:-3---------------10.2-----------8.6

C 31-CRPCIN-15.8-------------17.7---------15.9

                C  11-OAU      IN:    -7.6--------------   -60----------   -13.3

Root Cause

Improper configuration of IPA threshold lead to the service down

#0xc0008:ipa-get-rxlosth:1
                                    IPA RXLOSTH                                  
                                   IDX   RXLOSTH                                 
                                   1     -150                                    
  Total records :1                                                               

If input optical power of OAU is below -15 , laser will be shut down but IPA will not take effect because input power of SC2 which is assist board for IPA is normal .

Suggestions

Chang the threshold of OAU

END