Abstract: A monitoring system which enables monitoring of a transponder accommodated in an optical path in a transmission node and a node according to their operation conditions is provided. The monitoring system comprises a monitor control management unit connected to at least one of ports of wavelength selective switches which monitors an inspection signal or an operation signal, and a control unit which controls the wavelength selective switch so as to enable monitoring by the monitor control management unit.

Abstract: In a conventional hard material insulator, reproduced sound can be tuned with use of characteristics of the material; however, various types of acoustic materials have specific high frequency characteristics, and thus their acoustic effects lack versatility, require compatible audio devices, and change with environment, musical genre, etc. To address this, a wind-bell member (resonant member) is arranged in parallel with a main propagation path of vibration transferred from an audio device to an insulator. Accordingly, a vibration system of a wind-bell having a tone determined by many factors such as a fundamental tone, harmonic tones, lingering sound, and fluctuation assists (enhances) high frequency vibration propagated from the audio device. As a result, due to the above assist action that is different in principle from a conventional type, acoustic characteristics such as a sense of localization, resolution, and a sense of transparency and scale a sound image can be dramatically improved.

Abstract: A solution is a liquid organosilicon compound represented by general formula (1) as described below: wherein, X is each independently a group represented by formula (I), formula (II) or formula (III) as described below, and when the number of the group represented by formula (I) per one molecule of the liquid organosilicon compound represented by general formula (1) is defined as a, the number of the group represented by formula (II) per one molecule thereof is defined as b, and the number of the group represented by formula (III) per one molecule thereof is defined as c, 0?a?3.5, 0?b?3.

Abstract: In order to realize a multiplexer/demultiplexer in which utilization efficiency of a frequency is high, wavelength characteristics of a transmission band is flat, the cost is low, the size is small, and a wavelength and a band are variable, the multiplexer/demultiplexer includes: first light branching means for branching inputted light into plurality of pieces of light and outputting the branched pieces of light; a plurality of light wavelength separating means for separating and outputting light outputted from the first light branching means for each of predetermined frequency bands; and an optical coupling means for making outputs having frequency bands different from each other among outputs from the light wavelength separating means gather and be outputted.

Abstract: A sender transmits to a receiver an optical signal that is phase-modulated in accordance with source data and a basis stored in a memory. The receiver phase-modulates the received optical signal in accordance with a basis, obtains detection data through interference, and stores the detection data in a memory. An inter-device address difference (GD) and an intra-device address difference (DI) are provisionally set. The detection data are checked against the source data while sequentially changing the values of GD and DI within a predetermined adjustment range. Based on the result of this checking, GD and DI are determined.

Abstract: An organosilicon compound which is obtained by subjecting a compound (A), a compound (B) and a compound (C) to hydrosilylation reaction: (A) silicone and/or silsesquioxane that has two or more Si—H groups per one molecule and has a molecular weight of 100 to 500,000; (B) silicone and/or silsesquioxane that has two or more alkenyl groups per one molecule and has a molecular weight of 100 to 500,000; and (C) a compound that has one or more epoxy or oxetanyl group and an alkenyl group having 2 to 18 carbon atoms per one molecule.

Abstract: A cryptographic key management method and device are provided by which cryptographic keys of multiple nodes can be managed easily and stably. A system includes at least one first node and a plurality of second nodes connected to the first node, and the first node individually generates and consumes a cryptographic key with each of the second nodes connected to the first node itself. A cryptographic key management device in such a system has a monitor that monitors the stored key amounts of cryptographic keys of the individual second nodes, stored at the first node, and a key management control section that performs key generation control on the first node, based on the stored key amounts.

Abstract: A liquid organosilicon compound comprising a structural unit represented by the following formula (1-a) and a structural unit represented by the following formula (1-b): In the above formula (1-a), R1 each independently is a group selected from an alkyl having 1 to 4 carbon atoms, cyclopentyl and cyclohexyl and in the above formula (1-b), R2 and R3 each independently are a group selected from an alkyl having 1 to 4 carbon atoms, cyclopentyl and cyclohexyl, and n is an integer of 2 to 50. When a mole fraction of the structural unit represented by the formula (1-a) in the liquid organosilicon compound is ? and a mole fraction of the structural unit represented by the formula (1-b) in the liquid organosilicon compound is ?, the ratio of ? and n×? (?:n×?) meets 1:3 to 1:100.

Abstract: A communication system and a timing control method are proposed that optimize timing in a sender and thereby enable information to be stably transmitted at the right timing. Under instructions from a timing controller in a receiver, the timing of driving a phase modulator in a sender is shifted by one step after another, and the then amount of clock shift and result of interference are monitored at the receiver and stored in a memory. The optimum timing is determined based on the stored data. Thus, a clock for driving the phase modulator in the sender can be set at the right timing. This is equivalent to compensating for group velocity dispersion due to wavelength dispersion that occurs when an optical signal channel and a clock signal channel are transmitted by wavelength division multiplexing transmission.

Abstract: For an error rate QBER, threshold values are preset, including a threshold value Qbit for frame synchronization processing, a threshold value Qphase for phase correction processing, and a threshold value QEve for eavesdropping detection. Upon the distribution of a quantum key from a sender to a receiver, when the measurement value of QBER is deteriorated more than Qbit, frame synchronization processing is performed. When the measurement value of QBER is deteriorated more than Qphase, phase correction processing and frame synchronization processing are performed. When QBER does not become better than QEve even after these recovery-processing steps are repeated N times, it is determined that there is a possibility of eavesdropping, and the processing is stopped.

Abstract: An optical transmitter which modulates the phases and intensities of double pulses and then transmits them, includes a branching section which branches each of the input double pulses to first and second paths, a first optical modulator placed in the first path, second and third optical modulators placed in series in the second path, and a combining section which combines the double pulses having traveled through the first path with the double pulses having traveled through the second path to output double pulses. A control section controls such that each of the first and second optical modulators performs any one of relative intensity modulation and relative phase modulation on the double pulses passing through, and the third optical modulator performs relative phase modulation on the double pulses passing through.

Abstract: A secret communications system realizes point-to-multipoint or multipoint-to-multipoint connections of both quantum channels and classical channels. Multiple remote nodes are individually connected to a center node through optical fiber, and random-number strings K1 to KN are individually generated and shared between the respective remote nodes and the center node. Encrypted communication is performed between each remote node and the center node by using the corresponding one of the shared random-number strings K1 to KN as a cryptographic key. The center node is provided with a switch section for quantum channels and a switch section for classical channels. Switching control on each of these switch sections is performed independently of the other by a controller.

Abstract: In a secret communication network including a center node and multiple remote nodes, the center node is provided with a virtual remote node which functions as a remote node similar to each of the remote nodes. Random numbers shared between the center node and each remote node are managed based on random number sequences used in cipher communication between the virtual remote node and one of the remote nodes.

Abstract: A method and apparatus for measuring the optical power of very weak light arriving at a receiver, by using a photon detector, are provided. A photon detector detects the presence or absence of the arrival of a photon in accordance with bias application timing. For a train of optical pulses coming in at an arbitrary timing in respective time slots, the bias application timing is sequentially shifted within the range of a time slot. Each time a shift is made, the number of photons detected is counted by a photon counter. Based on this number of photons, the optical power of the train of the optical pulses is measured.

Abstract: For an error rate QBER, threshold values are preset, including a threshold value Qbit for frame synchronization processing, a threshold value Qphase for phase correction processing, and a threshold value QEve for eavesdropping detection. Upon the distribution of a quantum key from a sender to a receiver, when the measurement value of QBER is deteriorated more than Qbit, frame synchronization processing is performed. When the measurement value of QBER is deteriorated more than Qphase, phase correction processing and frame synchronization processing are performed. When QBER does not become better than QEve even after these recovery-processing steps are repeated N times, it is determined that there is a possibility of eavesdropping, and the processing is stopped.

Abstract: A communication system capable of employing polarization-dependent phase modulators with a reversing configuration that preserves security against disturbance of a polarization state at a transmission path but without using Faraday mirrors and a communication method using the same are provided. A quantum cryptography system of the present invention includes a first station 1, a transmission path 2, and a second station 3. The first station 1 has means for emitting time-divided optical pulses into the transmission path 2 and measuring a phase difference between the optical pulses returning from the transmission path 2. The transmission path 2 is a medium of light.

Abstract: For an error rate QBER, threshold values are preset, including a threshold value Qbit for frame synchronization processing, a threshold value Qphase for phase correction processing, and a threshold value QEve for eavesdropping detection. Upon the distribution of a quantum key from a sender to a receiver, when the measurement value of QBER is deteriorated more than Qbit, frame synchronization processing is performed. When the measurement value of QBER is deteriorated more than Qphase, phase correction processing and frame synchronization processing are performed. When QBER does not become better than QEve even after these recovery-processing steps are repeated N times, it is determined that there is a possibility of eavesdropping, and the processing is stopped.

Abstract: An optical communication apparatus that can perform stable intensity and phase modulation on an optical pulse at high speed is provided, as well as a quantum key distribution system using the apparatus. Using multilevel signals for the electric signals (RF1, RF2) to be applied to two arms of a two-electrode Mach-Zehnder modulator, phase modulation is performed on an optical pulse in accordance with the average of the levels of the signals (RF1, RF2), and intensity modulation is performed on the optical pulse in accordance with the voltage difference between the signals (RF1, RF2), whereby stable high-speed multilevel modulation can be realized. The cryptographic key generation rate in a decoy quantum key distribution system is enhanced.

Abstract: A sender's encrypted communication apparatus and a recipient's encrypted communication apparatus autonomously generate keys for encryption with respective key generators, store the generated encryption keys in respective encryption key memories, and store part of the generated encryption keys in respective authentication memories. The keys stored in the authentication memories are used for mutual authentication when the sender's encrypted communication apparatus and a recipient's encrypted communication apparatus are connected to each other.

Abstract: A quantum cryptography key distributing system includes an optical fiber; a transmission unit and a reception unit. The transmission unit is connected with the optical fiber, generates a transmission optical pulse signal from an optical pulse signal based on a first data in synchronism with an optical clock signal and transmits the transmission optical pulse signal to the reception unit via the optical fiber. Polarization of the transmission optical pulse signal is different from that of the optical pulse signal. The reception unit is connected with the optical fiber, transmits the optical pulse signal to the transmission unit via the optical fiber, phase-modulates a part of the transmission optical pulse signal based on a second data in synchronism with the optical clock signal, and detects a reception data corresponding to the first data based on the transmission optical pulse signal in synchronism with the optical clock signal.