Experimental Evaluation of an Optical Time Division Demultiplexer for Twenty-four Channels

Experimental techniques for optical demultiplexing by use of sinusoidal polarization switches were evaluated. For this purpose the terminals of a twenty-four-channel optical PCM system were simulated by two channels separated in time by1/24th the pulse period. The complete twenty-four PCM channels would have an information rate of 6.7 Gbit/sec. The measured values of cross talk in the demultiplexer were -13 dB and -9 dB for the two channels used in the simulated system. The major contributions to the cross talk were (1) intrinsic cross talk due to the use of a sine wave rather than a square wave for polarization switching (-19.6 dB and -13.1 dB); (2) light leakage in the demultiplexer crystals due to rf heating that gives rise to a nonuniform birefringence (-19 dB, both channels); and (3) misadjustment of the demultiplexer.