Phase-modulated fiber optic telecommunications system

An optical data transmitter comprising:

• a laser for producing light;
• a phase modulator phase modulating the light;
• and
• an electronic control circuit for receiving an electronic input data stream and controlling the phase-modulator, the electronic control circuit including an input data circuit having an electronic delay and a phase compensation circuit for altering an output of the input data circuit, the phase compensation circuit including an N-bit register for storing a desired phase compensation amount, an ALU for summing without carry the desired phase compensation amount, and a delayed feedback exclusive-or gate having a gate output and receiving the input data stream as an input, and wherein a most significant bit of an ALU output of the ALU is fed together with the gate output through another exclusive-or gate.

A fiber optic data transmission system comprising:

• a transmitter having a laser emitting a continuous wave light, the transmitter including a phase modulator phase modulating the continuous wave light and a control circuit controlling the phase modulator as a function of an electronic input data stream having a time delay, so as to create a phase-modulated optical signal;
• an optical fiber transmitting the phase-modulated optical signal;
• and a receiver, the receiver including an interferometer for receiving the phase-modulated optical signal, the interferometer having a first arm and a second arm, the second arm being longer than the first arm, the interferometer having an interferometric delay corresponding to the time delay and a phase difference imparted by the first and second arms, the control circuit imparting a phase to represent a binary zero or one as a function of the phase difference,
• the control circuit including a phase-compensation circuit for rotating a phase imparted by the phase modulator by a predetermined amount wherein the predetermined amount is a function of the phase difference imparted by the interferometer, the phase compensation circuit including an N-bit register storing the predetermined amount, an ALU for summing without carry the predetermined amount, and a delayed feedback exclusive or gate having a gate output and receiving the input data steam as an input, and a most significant bit of an ALU output of the ALU being fed together with the gate output through an other exclusive-or gate.