EXFO FTB-8500 Series for FTB-500 - Manual (Page 209)

Traffic Analyzer Tabs
Ethernet and Fibre Channel Application 195
FC Latency
FC Latency
Note: Available with FC Framed Layer 1 and FC Framed Layer 2 only.
Press TEST, Traffic Analyzer, and Latency.
Latency is only available when the two following conditions are met:

Framed Layer 1 or Framed Layer 2 has been selected from the BERT
Configuration panel on both TX and RX Configuration.

The test pattern should be different than CRPAT, CSPAT, and CJTPAT.
Configuration
Latency Tag: Allows Latency and Buffer-to-Buffer Credit
measurements when the Latency Tag check box is selected. The
Latency Tag check box is cleared by default.