EXFO FTB-8510B Guia Del Usuario página 883

For OC-768: The REI-L error is declared when the combination of the
M0 and M1 bytes indicates that one or more BIP violations have been
detected.
Alarm Analysis
AIS-L (Alarm Indication Signal - Line): The AIS-L alarm is declared
when bits 6, 7 and 8 of the K2 byte contain the "111" pattern in five
consecutive frames.
RDI-L (Remote Defect Indication - Line): The RDI-L alarm is declared
when bits 6, 7, and 8 of the K2 byte contain the "110" pattern in five
consecutive frames.
SONET/SDH Application
M0
Located in STS-1 #4
0000 0000
0000 0000
0000 0000
:
0001 1000
0001 1000
:
1111 1111
M1
Located in STS-1 #7
0000 0000
0000 0001
0000 0010
:
0000 0000
0000 0001
1111 1111
SONET Tabs
Line RX (SONET)
Indicates
0 BIP violation
1 BIP violation
2 BIP violations
6144 BIP violations
0 BIP violation
:
0 BIP violation
233