Patent ID: 8121489

Claim:
An optical transmitting and receiving system comprising: an optical transmitter; an optical receiver; and an optical transmission channel that connects the optical transmitter to the optical receiver, wherein the optical transmitter includes an optical pulse source, a first asymmetric interferometer that converts a train of output pulses from the optical pulse source into a train of dual pulses, the delay time of which is longer than half the period of the output pulses, a phase modulator that modulates two optical pulses as a unit, one of the two optical pulses having passed through one arm of the first asymmetric interferometer, the other optical pulse having passed through another arm of the first asymmetric interferometer, the original pulse giving the other optical pulse being different from the original pulse giving the one optical pulse, where an original pulse means a pulse in the train just outputted from the optical pulse source, the receiver includes a second asymmetric interferometer that provides the same optical path length difference as that provided in the first asymmetric interferometer, and a balanced detector, and signal light outputted from the optical transmitter and propagating through the optical transmission channel passes through the second asymmetric interferometer in the optical receiver and is received by the balanced detector.