Patent ID: 7483640

Claim:
An optical multilevel-coded signal transmission system to transmit information comprising: an optical transmitter, and an optical receiver for receiving the transmitted information through an optical transmission line using optical intensity and optical phase separately, wherein the optical transmitter comprises an inverted RZ signal light generator to generate an inverted RZ signal light intensity-modulated with a first data; and an optical phase modulator to phase-modulate the inverted RZ signal light according to a second data; and wherein the optical receiver comprises a splitter to split a light input from the optical transmission line into first and second portions; an inverter to invert the first portion from the splitter; a first detector to detect the first data in the first portion inverted by the inverter; a converter to convert a phase-modulated signal included in the second portion from the splitter into an optical intensity-modulated signal; and a second detector to detect the second data in the optical intensity-modulated signal from the converter.