EXFO FTB-8510B Guia Del Usuario página 881

For OC-12: The REI-L error is declared when the M1 byte located in the
STS-1 #7 indicates that one or more BIP violations have been detected.
For OC-48: The REI-L error is declared when the M1 byte located in the
STS-1 #7 indicates that one or more BIP violations have been detected.
SONET/SDH Application
M1, bits
234 5678
000 0000
000 0001
000 0010
:
110 0000
110 0001
:
111 1111
M1
0000 0000
0000 0001
0000 0010
:
1111 1111
SONET Tabs
Line RX (SONET)
Indicates
0 BIP violation
1 BIP violation
2 BIP violations
:
96 BIP violations
0 BIP violation
:
0 BIP violation
Indicates
0 BIP violation
1 BIP violation
2 BIP violations
:
255 BIP violations
231