EXFO FTB/IQS-88000 Series Power Blazer for FTB-2/2Pro/500/IQS-600 - Manual (Page 463)

Test Functions
Power Blazer 451
OH - GFP-F/GFP-T

Extension Header: CID, Spare, and eHEC are only available when EXI
is set to Linear (refer to EXI on page 138).

CID (Channel IDentifier) indicates the communication channel
used by the signal. Possible values are 00000000 through 11111111
(0 to 255).

Spare indicates the extension header Spare field. Possible values
are 00000000 through 11111111 (0 to 255).

eHEC (Type Header Error Control) indicates the CRC-16 error
control code that protects the integrity of the contents of the
extension header by enabling both single-bit error correction
(optional) and multi-bit error detection.
OH Details
Displays the details of the selected OH byte. The first column indicates the
selected OH byte. The second column indicates respectively from top to
bottom the bit numbers used, the byte value in binary, and the
interpretation of the byte when applicable.