Remote-control signal of optical loopback for supervision of long-haul fiber-optic undersea cable systems

A remote-control signal for repeater supervision to be used in a remote-controlled optical loopback method of a long-haul optical undersea cable system is proposed on out-of-service basis and the results of its transmission experiment by a field trial system are theoretically analyzed. The remote-control signal is basically composed of a pseudo-random sequence with a periodicity corresponding to a repeater selection frequency. 500 repeater selection frequencies will be available using a monolithic crystal filter (MCF) as a detection filter. By a field trial experiment, the controllability was shown to be maintained even at a bit error rate (BER) of up to 10^-1with a control signal level which, being decreased by 1.9 dB, is still more than 30 dB over a filtered noise level due to random bit errors.