Symptom
On a point-to-point network built with the OptiX OSN 6800, wavelengths are added at station A, pass through station B, and then are dropped at station C. In system commissioning, the optical power at the IN port on the FIU board at station C is -12 dBm but the optical power at the TC port on the FIU board at station C is -38 dBm. This means that insertion loss reaches 26 dB.
Cause analysis
The FIU board is a multiplexer/demultiplexer board. It receives signals from the opposite end through the IN port. Then, it outputs main optical path signals through the TC port and outputs the supervisory channel signals through the TM port.
Procedure
- Field engineers measure the optical power at the TM port on the FIU board at station C and the value is -12 dBm. This means that the FIU board at station C may receive only the supervisory channel signals from the SC1 board at station A through the IN port but no main optical path signals is received. Field engineers check fiber connections and find that the fiber from the M40 board at station A to the FIU board at station C is not properly installed. Then, field engineers re-install the fiber and the optical power of the TC port at station C becomes normal.
