EXFO FTB-800 Series for FTB-1 - Manual (Page 384)

Test Results
374 FTB-700G/800 Series
Traces - OTN

SAPI OTU/ODU-TIM check boxes, when selected (cleared by default),
allows editing the expected Source Access Point Identifier (SAPI) and
also enables OTU/ODU-TIM alarm monitoring.

DAPI OTU/ODU-TIM check box, when selected (cleared by default),
allows editing the expected Destination Access Point Identifier (SAPI)
and also enables the OTU/ODU/TCM-TIM alarm monitoring.

Copy RX uses the received SAPI/DAPI message as the expected
SAPI/DAPI message.