This article shares with you an issue about CHAN_LOS alarm on the OPM8 board housed in an OptiX OSN 8800 equipment.
TN12OPM8 is the functional version of the board in this case. This version of the board provides eight ports, and each port supports optical power monitoring for up to 80 wavelengths. TN12OPM8 supports standard wavelength detection and optical power detection of each wavelength at a fixed channel spacing of C-band. Also supports APE (Automatic Power Equilibrium) function and Optical-Layer ASON.
NOTE: APE is a function to automatically equalize channel optical power at the transmitter end, ensuring a required optical power flatness and OSNR at the receiver end.
The TN12OPM8 board can interoperate with the Optical Doctor management system license. When the Optical Doctor management system license is used, the TN12OPM8 board supports OSNR detection for 10 Gbit/s, 40 Gbit/s, 100 Gbit/s, 200 Gbit/s, and 400 Gbit/s (dual-carrier) signals.
The OPM8 board consists of a 1×8 optical switch, power monitoring/spectrum analysis module, a driver and control module, control and communication module, and power supply module.
Description:
The is as follows:
and 8800_A is a FOADM node and its internal fiber is as shown below:
NOTE: The internal fiber of the SITE C and SITE B nodes is similar to the one shown above.
The customer reports the appearance of CHAN_LOS alarms on the OPM8 board in the 8800_A node on all OChs (Optical Channels) from/to adjacent sites.
Analysis:
Single-wavelength signal loss or performance (the center wavelength, power, or OSNR) degrade alarm. The CHAN_LOS alarm is generated when the 8-channel optical power monitor (OPM8) board detects that the original wavelength is lost or the optical spectrum performance degrade amount exceeds the threshold after it scans the optical spectrum.
Following the CHAN_LOS alarm handling procedure, this indicates that the impact on the system is:
- The services of the related wavelength are unavailable.
- The OPM8 cannot monitor the optical spectrum performance of the wavelength related to the alarm.
The DWDM network path (capacity for 80 wavelengths in C-band) between SITE C <-> SITE A <-> SITE B, which was new at that time, only has 4 OChs (100Gbit/s of bandwidth each) in service, allocating 3 wavelengths (78/192.2/1559.79, 76/192.3/1558.98 and 70/192.6/1556.55) for it.
The status of the OChs is checked, verifying that all are in service and no alarms.
The OChs received from SITE A are monitored at SITE C and SITE B through the OPM8 boards housed in these nodes. The Optical Power (dBm) and OSNR (dB) of all OChs are normal:
The OChs sent from SITE C and SITE B to SITE A are also monitored. The Optical Power (dBm) and OSNR (dB) of all OChs are also normal.
It is verified that the OPM8 board of SITE A detects the OChs received from SITE C and SITE B but doesn’t monitor the Optical Power (dBm) and OSNR (dB):
The OPM8 board also detects the OChs sent to SITE C and SITE B from SITE A but doesn’t monitor the Optical Power (dBm) and OSNR (dB).
The OAU106 optical amplifiers in SITE C and SITE B towards SITE A are checked, verifying that work successfully (reference values are OK).
In addition, the OAU106 optical amplifiers in SITE A that receive the signal from SITE C and SITE B are checked, verifying that work successfully (reference values are OK).
Finally, also checked the optical amplifiers of the OLA intermediate nodes, verifying that work successfully (reference values are OK).
Therefore, of the possible causes that, according to the handling procedure, can generate this CHAN_LOS alarm:
- Cause 1: The wavelength that needs to be monitored is not received or the shift of the monitored wavelength exceeds 0.15 nm.
- Cause 2: The laser on the line board at the opposite station is turned off.
- Cause 3: The optical power difference between the monitored wavelengths is excessively large.
- Cause 4: The attenuation of the multiplexer or OA board interconnected with the OPM8 is excessively high.
- Cause 5: The line board located before the OPM8 is faulty.
- Cause 6: The OPM8 that reports the alarm is faulty.
the Cause 6 is the reason for this issue.
Solution:
The OPM8 board that reports the CHAN_LOS alarm is faulty.
1. Perform a cold reset on the OPM8 board or remove and re-insert the board. Then, check whether the alarm is cleared.
2. If the alarm persists, replace the board.
Cold reset from NMS is performed on OPM8 board, but CHAN_LOS alarms persist. Therefore, the OPM8 board in the SITE A node is replaced with a new spare.
After the replacement, CHAN_LOS alarms are cleared and the new OPM8 board successfully monitors the Optical Power (dBm) and OSNR (dB) of all OChs.
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