EXFO FTB-800 Series for FTB-1 - Manual (Page 433)

Test Functions
NetBlazer 423
OH - SONET/SDH
Transport OH - Section/RS

A1 and A2: Framing. The value should be hexadecimal F6 for A1 and
28 for A2. They must appear in every STS-1/STM-1 frame of a
composite signal.
SONET: Provide frame alignment of each STS-1 frame within a
composite signal (STS-1 to STS-n).
SDH: Indicate the beginning of the STM-N frame.

J0/Z0

J0
1
: The J0 (Trace) byte is used to trace the origin of an
STS-1/STM-1 frame as it travels across the SONET/SDH network.
Available when the Trace format is set to 1 Byte (Refer to Traces
(SONET/SDH) on page 239).

Z0: Growth.
SONET: The Z0 byte was used to uniquely identify the STS in
question. This byte has to be defined in every STS-1 to STS-n frame
of a composite signal. This byte is only defined for the STS-1 #2 to
STS-1 #N of a OC-N signal.
SDH: These bytes are reserved for future international
standardization. They are located at positions S[1,6N+2] to S[1,7N]
of an STM-N signal (N > 1).

B1
1
: BIP-8 (Bit-Interleaved Parity) byte provides section error
monitoring. The byte is calculated by performing a routine even-parity
check over all bits of the previous STS-N/STM-N frame of a composite
signal.

E1
1 : Orderwire. Provides a 64 Kbit/s voice channel for communication
between two STEs (Section Terminating Equipment).
1. This byte is only defined for the first STS-1/STM-1 frame of a composite signal.