Birefringent Branching Filters for Wideband Optical FDM Communications

Optical branching filters consisting of birefringent filters for combining and splitting eight optical channels are studied in detail both theoretically and experimentally. Multisegment structures were used in the channel-splitting filter to suppress the crosstalk from other channels. The crosstalk of -15.5 dB was realized for a signal bandwidth B(in) equal to 67.5% of the channel separation. Discussions on the pulse response of the filter system, effects of nonzero extinction ratio, and influences of the filter frequency detuning are included.