National Institute of Information and Communications Technology, Incorporated

Nec Corporation

Morio Toyoshima

Mikio Fujiwara

Hiroo Kunimori

Yoshihisa Takayama

Akihisa Tomita

Ken-ichiro Yoshino

Masahide Sasaki

Yoshihiro Nambu

Dimitar Kolev

Nozomu Nishinaga

Yoshinori Arimoto

A free-space optical communication apparatus, transmitting and receiving light waves to and from an artificial satellite orbiting an earth orbit, includes a transmission light wave generating unit generating a transmission light wave to be transmitted to the artificial satellite, a telescope having an aperture for collecting a reception light wave emitted from the artificial satellite, the aperture adapted to collect a path propagation light propagating through a space including a propagation path for correcting an uplink transmission light wavefront generated by the transmission light wave generating unit to the artificial satellite, a wavefront sensor detecting wavefront distortions of the reception light wave and the uplink propagation path, a control unit generating a control signal based on the wavefront distortions, and a deformable mirror correcting the uplink propagation path based on the control signal to guide the transmission light wave to the artificial satellite through the telescope.

Free-space optical communication apparatus and method

It is an object of the present invention to provide a network system for quantum key distribution (QKD) for free space and fiber networks. The system of the present invention generates a couple of photons which have different wavelength and inputs each of the photons into the asymmetric Mach-Zehnder interferometer to obtain time-bin entangled state. It provides polarization information with one part of the photons. Then it can obtain hybrid quantum entanglement. The system of the present invention may be used hybrid quantum key distribution system applied for both free space and fibers.

Time-bin polarization format exchange technique for entangled optical source

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.

Apparatus and method for quantum cryptography communication

A switch is to be inputted a modulation signal including the synchronization signal extracted from a received communication signal as a control signal, is to be inputted a detection signal detected by a photodetector that receives a polarization modulation signal adjusted to a polarization direction of a quantum cipher signal, and selectively switches and outputs one of the detection signal and an inverted signal of the detection signal according to the control signal. A low-pass filter outputs the output signal of the switch, whereby a plus level signal is outputted when a relative angle difference &#x394;&#x3b8; between polarization axes on a transmission side and a reception side is larger than a predetermined polarization angle, a 0 level signal is outputted when &#x394;&#x3b8; is equal to the predetermined polarization angle, and a minus level signal is outputted when &#x394;&#x3b8; is in a range of the predetermined polarization angle from 0 degree.

Polarization direction synchronization detecting circuit and receiving apparatus

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.

Coherent optical receiver

In order to provide a satellite information autonomous distribution satellite capable of collecting attribute information for satellites after failure or damage occurs at or to the satellite, an information collection device is operated by a second power supply provided independently from the first power supply operating the satellite bus system, is provided separately from the satellite bus system, and collects and stores attribute information. The light receiver is provided separately from the satellite bus system and forms a prescribed control signal when light sent from the information collection station is received. The reflecting type light modulating device is operated by the second power supply, is provided separately from the satellite bus system, and transmits reflected light superimposed with a modulation signal containing attribute information in the reflected waves using this modulation signal when a modulation signal is formed based on attribute information stored in the information collection device according to the shape of the control signal.

Growing community of inventors

Tokyo, Japan

Morio Toyoshima