what is problems when you get high bit error in line card ?

Multiple factors can cause high bit rate errors on line card - Bad RX levels; bad RX card; bad attenuator in between; dirty fiber and bad TX card

It depends on the location of receiving these errors whether it is on RS or MS or path (B1,B2,B3).

if it is on MS or RS so you can follow the below steps:

1- Check the Rx power on the NMS,if it is OK go to step2.

2-Put hardware loop with attenuater on the line card SFP if all errors cleared so card and the sfp are ok and the errors coming from the other end.

3- put tester on the fibers and start loop testing to determine the source of errors.

Dear Mohammed,  RX optical fiber power will be in thershold level, due to that will get affect high bit errors in line card.