EDFA goes incommunicado after a random number of hours/days of operation
The KeopSys EDFA installed in the ISR cave dropped communication repeatedly during the long duration tests. It fell into a non-responsive state where its serial line spat the 'C' character at a constant rate. No way to recover it other than power cycling the computer.
This happened with an FTDI-based USB-to-serial interface cable, and with a MAX232-based RS232 cabling interface as well.