Demonstration of coherent detection technique for broadband optical comb light source

Abstract

We have experimentally demonstrated an observation method of broad band optical comb by retrieving from the fragments of spectra. The optical comb with 150 GHz bandwidth was divided into six fragments of spectra and they are individually detected by a coherent receiver with 18 GHz bandwidth. The fragments of spectra are unified based on the boundary condition where the highest frequency component of a fragment is equal to the lowest one in next fragment. The time domain waveform has been successfully retrieved from the fragments and agree well with that observed by 65 GHz sampling oscilloscope. To verify the validity of the method, 30 GHz optical comb was observed by both signal-shot and retrieving method. The results of amplitude and phase showed good agreement and revealed that the retrieving method is very effective to observe the complex amplitude of broadband optical comb.