Simple coherent detector for a coherent FM-SCM system

A coherent sub carrier multiplexing (SCM) lightwave detection scheme using a lock-in microwave has been proposed. The discriminator does not have any false locking problem which is common in a heterodyne phase locked demodula tor. Noise filtering and interference rejection properties of the discrimin ator are studied. It is also found that for the faithful demodulation local oscillator should he operated in the fundamental mode only. Computer simul ation results and representative experiments are presented in support of th e theory.