Simple all-fiber optical-microwave phase detector for subfemtosecond synchronization

Abstract

We demonstrate a passively phase-biased simple all-fiber optical-microwave phase detector based on intrinsic phase shift of multiport fiber coupler. It is composed of fiber coupler, phase modulator and balanced photodetector, hence free of additional phase bias and magneto-optic components. As a result of optical-microwave synchronization between mode-locked laser and voltage controlled microwave oscillator, 875-as integrated jitter [1 Hz-1 MHz] and 860-as rms timing drift over 1 hour is achieved.