Consider a spur Link with two stations A and B, Station A is visible on NMS and station B is logged out. with Alarm R_LOS.
1. I reached the site at Station B and observed that I am recieving Optical power from Station A. On T2000 I observed that at this Station I am having LP_RDI on the configured SDH services.
2. I went to Station A again and checked the recieve power from Station B.
It was "LOW". No power and on that Port R_LOS was coming.
Finally with the help of customer I changed the single fiber of Station B transmit, or Station A recieve.
Now I was recieving Station B transmit power.
I logged on the Station A with T2000 and checked the alarms R_LOS is gone.
At station B LP_RDI is gone as VC12 level service is configured.
R_LOS at Station A, LP_RDI at station B.
When Trouble shooting please make sure that on the NE, all the major and critical alarms are unsuppressed. which makes Trouble Shooting easy.
The cause was one fiber. Which was damaged or splice got loose and Station A was only transmitting but not recieving.
Customer should periodically check the spare fibers with OTDR for fiber lengths, and repair the faulty fiber at earliest.
Two SDH or any optical equipmnent communicate only when it's Transmit, Recieve port is connected with good fibers.
Calculate the losses, and should know which fiber is deployed in the network, for e.g G.652 is a single mode fiber which is commonly deployed, and should know that on 1310 window wat are the dispersion losses and on 1550 window what are the dispersion losses