Abstract: A coherent optical receiver includes a 90-degree optical hybrid circuit to which a received signal light is input, I-channel and Q-channel photo detectors to which the outputs of the hybrid circuit are input, a clock extraction circuit which reproduces a clock whose speed is the same as a demodulated signal obtained by demodulating the received signal light and which is synchronized therewith, I-channel and Q-channel sampling circuits which sample the signal outputs from the I-channel and Q-channel photo detectors by use of the clock, and a digital signal processing section which digitally processes the sampled signals, converts them to a digital signal, and outputs the digital signal. The digital signal processing section feeds a phase offset signal detected there back to the clock extraction circuit to thereby control the phase of the clock, and compensates dispersion of light within a fiber and phase fluctuation during free-space propagation.

Abstract: A coherent optical receiver includes a 90-degree optical hybrid circuit to which a received signal light is input, I-channel and Q-channel photo detectors to which the outputs of the hybrid circuit are input, a clock extraction circuit which reproduces a clock whose speed is the same as a demodulated signal obtained by demodulating the received signal light and which is synchronized therewith, I-channel and Q-channel sampling circuits which sample the signal outputs from the I-channel and Q-channel photo detectors by use of the clock, and a digital signal processing section which digitally processes the sampled signals, converts them to a digital signal, and outputs the digital signal. The digital signal processing section feeds a phase offset signal detected there back to the clock extraction circuit to thereby control the phase of the clock, and compensates dispersion of light within a fiber and phase fluctuation during free-space propagation.

Abstract: A communication satellite facility and a satellite communication system adapted to respond flexibly to development and change of communication technologies occurring on the ground even after satellites have been launched. The system includes a first satellite having an antenna function, a second satellite having a modem function and a third satellite having a server function all of which are launched into one and same slot of geosynchronous orbit and connected one to another by wideband intersatellite communication. A ground station connected to a ground network communicates with the first satellite.

Abstract: The present invention aims to provide a communication satellite facility and a satellite communication system adapted to respond flexibly to development and change of communication technologies occurring on the ground even after satellites have been launched. This object is achieved, according to the invention, by a system comprising a first satellite having antenna function, a second satellite having modem function and a third satellite having server function all of which are launched into one and same slot of geosynchronous orbit and connected one to another by wideband intersatellite communication. A ground station connected to a ground network communicates with the first satellite.