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

The requirements for narrow linewidth lasers and short loop propagation delay limit optical phase-lock loop realizability with semiconductor lasers is presented. Although optical injection locking can provide low-phase-error variance, its locking range is limited by stability considerations. The first experimental results for a new architecture combining both techniques, the optical injection phase-lock loop (OIPLL), are reported. Phase error variance values as low as 0.006 rad/sup 2/ (500 MHz bandwidth) and locking ranges exceeding 26 GHz are achieved using DFB lasers of summed linewidth 36 MHz with loop delay of 15 ns and injection ratio less than -30 dB.