Discriminator-Aided Optical Phase-Lock Loop Incorporating a Frequency Down-Conversion Module

A new discriminator-aided optical phase-lock loop (OPLL) incorporating a frequency down-conversion module to generate a low phase noise, highly frequency-stable, and frequency-tunable microwave signal is proposed and demonstrated. The inclusion of the frequency down-conversion module allows the use of lower frequency components in the control circuits with a reduced cost. In addition, the new design allows continuous frequency tuning of the generated microwave signal. The down-conversion concept is presented, along with a phase noise analysis detailing the contributions to the phase noise from the reference sources. An OPLL based on the proposed configuration is implemented. The phase noise performance, as well as the frequency stability is experimentally studied