Symptom
On a Metro WDM network, the OptiX OSN 1800 is deployed. Two stations are connected through the LDGF2 and LDGF boards, and the intermediate station is a regeneration station and uses the LWX2 board. The optical path between the LDGF board at upstream station A and the LWX2 board at regeneration station C is blocked. The other side of the LWX2 board transmits light forcibly and the LDGF2 board at downstream station B reports an OTU1_LOF alarm.
http://localhost:7890/pages/31188390/01/31188390/01/resources/help/wdm/com/mc/image/tt_wdm_mc_0188_fig01.png
Cause Analysis
The LWX2 board at regeneration station C reports an R_LOS alarm and the LDGF2 board at downstream station B reports an OTU1_LOF alarm.
- The corresponding board at upstream station A transmits colorless light.
- The input optical power of station B is not within the permitted range.
- The FEC type setting is incorrect.
- The fiber transmission line is malfunctioning.
Procedure
- Use an optical power meter to measure the output optical power from the LWX2 board to downstream station B. The optical power is within the permitted range. Therefore, cause 2 is ruled out.
- On the NMS, query FEC Type and the setting is correct.
- Check where the alarm is generated. The location information of the alarm is 1-LDGF2-201(LP1/LP1)-OUT1:1. This shows that the alarm is reported by the IN1 port on the LDGF2 board in slot 1 of station B. Therefore, the optical line between upstream station A and regeneration station C may be blocked and this causes an R_LOS alarm on the LWX2 board at station C. Because Automatic Laser Shutdown of the LWX2 board at the regeneration station is set to Disabled, and Laser Status is set to ON, the LWX2 board transmits colorless light to downstream station B. Therefore, an OTU1_LOF alarm is reported.
- Repair the optical line between upstream station A and regeneration station C. Then the alarm is cleared.
Reference Information
- When an OTU1_LOF alarm is reported on the NMS, check for the location information in the alarm to determine the port that reports the alarm. For the LDGF2 board, 201(LP1/LP1) indicates the IN1 and IN2 optical ports, and 202(LP2/LP2) indicates the IN3 and IN4 optical ports. The digit 1 at the end of the location information indicates the IN1 or IN3 optical port. The digit 2 indicates the IN2 or IN4 optical port. For example, 3-LDGF2-202(LP2/LP2)-OUT1:2 indicates the IN4 optical port on the LDGF2 board in slot 3. The location information of other boards can be deduced by analogy.
- If the receive optical power is within the permitted range, determine whether the upstream station transmits colorless light. For the boards with the FEC function enabled, check that the FEC settings are correct.
- For the OTU boards on OptiX OSN 1800, the default and recommended value of Automatic Laser Shutdown is Enabled.
