Demonstration of a low bandwidth 1.06 mu m optical phase-locked loop for coherent homodyne communication

A type-II, 1.06- mu m, optical phase-locked-loop (OPLL) for use in a coherent homodyne receiver is discussed. Diode-laser-pumped solid-state lasers are used for both the local oscillator and transmitter, because their phase noise is significantly lower than that of diode lasers. Closed-loop RMS phase noise of less than 12 mrad (0.69 degrees ) is achieved, and modulation-demodulation in bulk modulators at rates from 20 kHz to 20 MHz with less than 19 degrees of modulation depth is demonstrated.>