Generation of a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37Â dB

By inserting an asymmetric Mach-Zehnder interferometer (AMZI) into the re-circulating frequency shift loop, we experimentally obtained a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37 dB. The simulation and experimental results show that the amplified spontaneous emission (ASE) noise of the optical frequency comb can be suppressed by 3 dB after the first loop, and the tone-to-noise ratio of the 50-tone optical frequency comb is enhanced by 23.5 dB compared to that without the AMZI.