Active fiber comb source with single and double frequency shifters for UDWDM applications

Numerical and experimental results of a multifrequency optical source with an exceptionally stable channel separation are presented. The system consists of a single master laser and a ring containing an acousto-optic frequency shifter and an optical amplifier. The operation is based on the multiple frequency shift every round trip. We tested a single and double frequency shifter configuration. For the single stage configuration up to 84 spectral lines with stable 1.5 GHz spacing were obtained. Experimental results of the system with two cascaded shifters were demonstrated for the first time and up to 30 optical carrier frequencies with 2.5 GHz channel separation were obtained. The experimental results were in agreement with numerical simulations.