Pseudorandom pulse code generators using electro-optical XOR gates

摘要

Pseudorandom pulse code generators utilize XOR gates constructed of a pair of back to back parallel connected laser diodes, and fiber optic delay lines connecting the XOR gates to generate PN code sequences with tens of Gbits/s data rates. The single tap generator uses a fiber optic line of a length representing a selected number of delay stages connected to the optical output of the XOR gate and with optical splitters at the end of the delay line and at a selected delay stage feeding back optical signals to the optical inputs of the XOR gate to produce the PN sequence at the end of the delay line. Multi-tap generators utilize additional electro-optical XOR gates connected in serial-parallel, or preferably in a converging cascade arrangement to feed back pulses to the delay line. A syncopated PN code generator uses the electro-optical XOR gates to multiplex codes generated by syncopated pairs of relatively slow electronic shift register code generators with the required phase shifting provided by diffeence in the lengths of the optic fibers connected successive stages of XOR gates.