Abstract: A quantum cryptography communication apparatus performs quantum cryptography communication between a transmitter and a receiver. The quantum cryptography communication apparatus includes first communicating unit transmitting and receiving a communication signal including relatively strong pulse light between the transmitter and the receiver, and second communicating unit transmitting and receiving a relatively weak quantum cryptography signal between the transmitter and the receiver in a period in which the communication signal is off and the attitude axis for the receiver can be adjusted to that for the transmitter by the second communicating unit.

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 quantum cryptography communication apparatus performs quantum cryptography communication between a transmitter and a receiver. The quantum cryptography communication apparatus includes first communicating unit transmitting and receiving a communication signal including relatively strong pulse light between the transmitter and the receiver, and second communicating unit transmitting and receiving a relatively weak quantum cryptography signal between the transmitter and the receiver in a period in which the communication signal is off and the attitude axis for the receiver can be adjusted to that for the transmitter by the second communicating unit.

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 method of obtaining a set of measurements for making a position determination. Laser ranging measurements are made from at least two spaced apart stations with respect to a common distant moving object. The ranging measurements utilise respective signals transmitted from the stations so as to impact the moving object at substantially the same time. By making ranging measurements for a plurality of positions of the moving object the position determination can be made by triangulation techniques.

Abstract: A method of obtaining a set of measurements for making a position determination. Laser ranging measurements are made from at least two spaced apart stations with respect to a common distant moving object. The ranging measurements utilise respective signals transmitted from the stations so as to impact the moving object at substantially the same time. By making ranging measurements for a plurality of positions of the moving object the position determination can be made by triangulation techniques.

Abstract: A method of obtaining a set of measurements for making a position determination. Laser ranging measurements are made from at least two spaced apart stations with respect to a common distant moving object. The ranging measurements utilise respective signals transmitted from the stations so as to impact the moving object at substantially the same time. By making ranging measurements for a plurality of positions of the moving object the position determination can be made by triangulation techniques.