Patent ID: 7738793

Claim:
An optical transmitting/receiving system, the system comprising: an optical transmitter including a first phase modulator and a first light source inclusive of a laser light source and of an antisqueezer which expands a fluctuation of laser light from the laser light source in an antisqueezing direction that is orthogonal to amplitude of the light, in a phase space, and perpendicular to a superimposing direction of a signal; an optical receiver including two photodetectors, a beam splitter, a second light source phase-synchronized with a signal light from the optical transmitter, and a second phase modulator; and an optical transmission path connecting the optical transmitter and the optical receiver; wherein the system uses the light antisqueezed by the antisqueezer as a carrier; in the optical receiver, after either the signal light or a local light from the second light source is phase-modulated by the second phase modulator in terms of the characteristic phases φ of individual signals transmitted from the optical transmitter, the signal light and the local light are homodyne-detected through interfering, so as to detect the signal light projecting to a projection axis perpendicular to the antisqueezing direction of the fluctuation in the phase space.