High-performance heterodyne optical injection phase-lock loop using wide linewidth semiconductor lasers

The requirements for narrow linewidth lasers or short-loop propagation delay limit optical phase-lock loop realizability with semiconductor lasers. Although optical injection locking can provide low-phase-error variance, its locking range is limited by stability considerations. The first experimental results for an heterodyne optical injection phase-lock loop are reported. Phase-error variance as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, single-sideband (SSB) noise density of -94 dBc/Hz at 10-kHz offset and mean time to cycle slip of 3/spl times/10/sup 10/ s have been achieved using DFB lasers of 36-MHz summed linewidth, a loop propagation delay of 20 ns and an injection ratio of -30 dB.