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 demodulator. Noise filtering and interference rejection properties of the discriminator are studied. It is also found that for the faithful demodulation local oscillator should he operated in the fundamental mode only. Computer simulation results and representative experiments are presented in support of the theory.