As shown in the figure: A-B-C-D 4-site linearmultiplexingchain network, when doing linearmultiplexingsegment inversion testin each segment area, it is found that after disconnecting the primary fiber between BC, there is no alarm for the service of A-D, and for the2Mservicebetween A-C, TU_AIS is reported in site C and LP_RDI is reported in site A. After disconnecting the primary fiber between BC, there is no alarm for the service of A-D, and for the 2M service between C and D, TU_AIS is reported in site C and LP_RDI in site D. After disconnecting the primary fiber between CD, there is no alarm for the service of A-D, and for the2Mservicebetween C and D , TU_AIS is reported in site C and LP_RDI in site D. After disconnecting the main fiber between CD, there is no alarm for the service between A-D, and for the2Mservicebetween C-D, site C reports TU_AIS, site D reports LP_RDI, and the alarm disappears for the fiber restoration between CD.

Host version: V100R010C03SPH211(5.21.20.55)

Possible causes:
1, Linearmultiplexingsegment reversal failure;
2, Linearmultiplexingsegment protection group configuration parameter error;
3, Linearmultiplexingsegment protection channel abnormality;
4, Linearmultiplexingsegment protection channel line single board failure, cross single board failure;
5, Physical fiber connection, logical fiber connection error.

Processing:
1,after thelinearmultiplexingsegment inversion, the inversion site has amultiplexingsegment inverted alarm, only the inversion point of the existence of TU_AIS alarms, other services without alarms, indicating that after the fiber cut linearmultiplexingsegment inversion is normal; excludethe possibility of failure of thelinearmultiplexingsegment inversion;
2, check theparameters of the protection group linearmultiplexingsegment protection unit is very protection veneer logical mapping is correct;
3, respectively, to check the linearmultiplexingsegment of the BC network elementsInversion status, the protection channel is normal;
4, site C generated TU_AIS alarm where theVC4time slot channel there are other services, can notdo loopback operation on theVC4; between BC to find a freeVC4, configure the BC between the2Mlanding service to test, after the BC main fiber disconnect, site C2Mservice reported TU_AIS, site B2Mservice reported LP_RDI faults, the BC site2Mservice reported LP_RDI faults, the BC site2Mservice reportedTU_AIS, the BC site2Mservice to test theBCsite2Mservice to test theBCsite2Mservice toreport TU_AIS, site B2Mservice to report the BCsite2Mservice to report theTU_AIS.RDI fault remains, in the B site 11 slot 1, the thirdVC4playing the inner ring, B site alarm disappears, playing the outer ring C site alarm does not go away; in the C site 11 slot 2, the thirdVC4playing the inner ring, C site alarm disappears, playing the outer ring B site alarm does not go away; rule out the BC site of the crossover and the line veneer failure problems;
5, suspected that the BC standby channel optical misconnections between the BC site main fiber restoration, close the Site C 11-slot 2-port laser, site B 11-slot 1-port optical report R_LOS normal, turn off site B 11-slot 1-port laser, site C 11-slot 1-port optical report R_LOS abnormal, turn off site C 11-slot 1-port laser, site D 11-slot 2-port optical report R_LOS normal, turn off site D 11-slot 2-port laser, site C 11-slot 1-port optical report R_LOS abnormal; turn off site D 11-slot 1-port optical report R_LOS abnormal; turn off site D 11-slot 2-port laser; turn off site D 11-slot 1-port optical report R_LOS abnormal; turn off site D 11-slot 1-port optical report R_LOS abnormal; turn off site D 11-slot 1-port optical report R_LOS abnormal. R_LOS abnormal; through the shutdown of the laser found that the C site 11 slot 2 port RX fiber and 11 slot 1 port RX fiber mandarin ducks, resulting in linearmultiplexingsection of the business can not be (check whether the fiber connection is correct, you can also set the J0/J1 overhead byte by the local end, the opposite end to see whether it is possible to normally receive the setting of the J0/J1 byte to determine the normal fiber optic connection);
6, will be the 11 slot 2 port RX fiber and 11 slot 1 port RX fiber at the site of C site. C site 11-slot 2-port RX fiber and 11-slot 1-port RX fiber exchange, again BC, CD main fiber break test, business is normal.

Linearmultiplexingsection after the reversal of the business part of the failure, focus on checking the spare channel line and cross-single board failure, logical fiber and physical fiber is the same, whether the protection group parameters are correct; positioning can be selected without the use ofVC4channel configuration2Mservice test, convenient business loopback positioning.