Abstract: In a quantum cryptography communication apparatus, a light pulse is generated by a light source and split into a signal light pulse and a reference light pulse on a receiving side. The signal light pulse and the reference light pulse are transmitted to a sending side via a communication channel. On the sending side, the received reference light is passed through a first optical path and phase-modulated by a randomly selected amount. Communication information is acquired on the basis of the reference light passed through the first optical path and the signal light passed via a second optical path. Frequencies of the signal light pulse and the reference light pulse are shifted. The intensity of the signal light pulses is attenuated and phase-modulated by an amount corresponding to the communication information. The resultant signal light pulse and the reference light pulse are returned back to the receiving side.

Abstract: In a quantum cryptography communication apparatus, a light pulse is generated by a light source and split into a signal light pulse and a reference light pulse on a receiving side. The signal light pulse and the reference light pulse are transmitted to a sending side via a communication channel. On the sending side, the received reference light is passed through a first optical path and phase-modulated by a randomly selected amount. Communication information is acquired on the basis of the reference light passed through the first optical path and the signal light passed via a second optical path. Frequencies of the signal light pulse and the reference light pulse are shifted. The intensity of the signal light pulses is attenuated and phase-modulated by an amount corresponding to the communication information. The resultant signal light pulse and the reference light pulse are returned back to the receiving side.

Abstract: A quantum cipher communication system performs communication processing based on quantum cipher. It may have a first communication terminal, a second communication terminal, and a communication path that connects them. The first communication terminal may contain an optical source, a first light-separating device, optical paths, a light-synthesizing device, a second light-separating device, a first phase-modulator, and a homodyne detector that performs homodyne detection based on the reference light separated in the second light-separating device and passed through the first optical path and the signal light separated in the second light-separating device and passed through the second optical path. The second communication terminal may contain a light-sending device, an optical attenuator, a second phase-modulator, and a photon-number-setting device that sets to a predetermined value an average photon number of the signal light sent to the communication path from the light-sending device.

Abstract: An optical communication apparatus in which bidirectional communication may be made over a sole optical fiber. A light emitting device (132) radiates light through an optical system (133) to an optical fiber (76). The light transmitted from the optical fiber (76) is received over optical system (133) by a light receiving device (136). In the optical system (133), such a relationship S?2QN?M>S/2Q?N is set, where M is the light volume of the stray light emitted, Q is the value of a Q-value representing the communication quality as required, S is the light volume of a received signal from a communication partner and N is the sum total of the Gaussian noise.

Abstract: An optical communication system suitable for full duplex optical communication between a first and a second optical transceiver units. connected with each other by a single-core optical fiber. The first and second transceiver units may have different types of light emitting elements emitting light having different loss rates in the single-core optical fiber. The system enables stable full duplex communication without setting up large scale or costly transmission units by relatively reducing the optical crosstalk involved. The first optical transceiver unit provides transmission light to be coupled with the single-core optical fiber with the intensity in the range of TAmin–TAmax. The amount of light emitted from the light emitting element of the optical transceiver unit to be coupled with the single-core optical fiber is in the range TBmin–TBmax, which amount may be adjusted by a light emission adjusting unit provided in the optical transceiver unit.

Abstract: The invention provides an optical communication system, an optical transmitting apparatus, an optical receiving apparatus, an optical communication method, and a storage medium, in which a large-capacity transmission can be performed at high speed and multiplexing efficiency can be improved. The optical communication system includes an optical transmitting apparatus and an optical receiving apparatus connected via a transmitting medium having anomalous dispersion characteristics. In this system, the optical transmitting apparatus converts a plurality of information signals output from a plurality of signal sources into light signals having amplitudes different according to the respective information signals to output the light signals LP, by providing an individual specified optical intensity capable of performing an optical soliton transmission.

Abstract: In a network system having a simple construction, addressing method, communication control device and method thereof, the increase or decrease in the number of nodes does not affect the nodes of a network. Each node is provided with a first storage means for storing first information indicating all node identifiers used in a network and second information indicating the node identifiers of all nodes directly or indirectly connected to each port, and when new nodes are connected to the network, a predetermined first node gives each of the new nodes a node identifier and notifies the other nodes of this information, and when nodes are disconnected from the network, a prescribed second node remaining in the network notifies the other nodes of this information.

Abstract: An optical communication system suitable for full duplex optical communication between a first and a second optical transceiver units. connected with each other by a single-core optical fiber. The first and second transceiver units may have different types of light emitting elements emitting light having different loss rates in the single-core optical fiber. The system enables stable full duplex communication without setting up large scale or costly transmission units by relatively reducing the optical crosstalk involved. The first optical transceiver unit provides transmission light to be coupled with the single-core optical fiber with the intensity in the range of TAmin-TAmax. The amount of light emitted from the light emitting element of the optical transceiver unit to be coupled with the single-core optical fiber is in the range TBmin-TBmax, which amount may be adjusted by a light emission adjusting unit provided in the optical transceiver unit.

Abstract: A first surface of an optical component has a lens function of converging the transmission light from a light source. A second surface reflects the transmission light, converged by the lens function of the first surface, towards an end face of an optical transmission medium as the destination of transmission. The light reflected by the second surface is radaited from a coupling surface. Since the light beam from the light source is directed towards the optical transmission medium by exploiting the total reflection of light, a high-reflection multi-layer film or a polarization beam splitter film, required in a conventional apparatus employing a polarization beam splitter, is unneeded, with the result that the film forming cost or the cost in bonding two prisms used for fabricating the polarization beam splitter may be dispensed with. In this manner, the production cost or size of the apparatus can be reduced without lowering the transmission/reception performance.

Abstract: An optical communication apparatus in which bidirectional communication may be made over a sole optical fiber. A light emitting device (132) radiates light through an optical system (133) to an optical fiber (76). The light transmitted from the optical fiber (76) is received over optical system (133) by a light receiving device (136). In the optical system (133), such a relationship S−2QN≧M>S/2Q−N is set, where M is the light volume of the stray light emitted, Q is the value of a Q-value representing the communication quality as required, S is the light volume of a received signal from a communication partner and N is the sum total of the Gaussian noise.

Abstract: The invention provides an optical communication apparatus to communicate a data signal. The optical communication apparatus is capable of firmly carrying out optical communication using an optical transmission media. The optical transmission media may be connected between a first optical communication apparatus and a second optical communication apparatus. Upon a detector detecting an incoincidence between an electric signal outputted from a light receiving element and a test signal, a controller may control a parameter of a light emitting power control signal to increase an intensity of an optical signal outputted from a light emitting element. Upon the detector detecting a coincidence therebetween, the controller may set a current value of a parameter of the light emitting power control signal as a parameter upon a selector selecting the data signal.

Abstract: A first surface of an optical component has a lens function of converging the transmission light from a light source. A second surface reflects the transmission light, converged by the lens function of the first surface, towards an end face of an optical transmission medium as the destination of transmission. The light reflected by the second surface is radaited from a coupling surface. Since the light beam from the light source is directed towards the optical transmission medium by exploiting the total reflection of light, a high-reflection multi-layer film or a polarization beam splitter film, required in a conventional apparatus employing a polarization beam splitter, is unneeded, with the result that the film forming cost or the cost in bonding two prisms used for fabricating the polarization beam splitter may be dispensed with. In this manner, the production cost or size of the apparatus can be reduced without lowering the transmission/reception performance.

Abstract: An optical fiber connecting method and apparatus in which optical communication is performed in a uni-core bidirectional system as optical crosstalk is prevented from occurring. To this end, an optical fiber connector 1 includes a refractive index matching member 2 and an optical fiber connecting unit 5. The refractive index matching member 2 has a refractive index substantially equivalent to that of the cores of optical fibers 101, 102. The optical fiber connecting unit 5 interconnects the optical fibers 101, 102 in a state in which end faces 101a, 102a of the optical fibers 101, 102 are contacted with a refractive index matching member 2 interposed between the end faces 101a, 102a of the optical fibers 101, 102.

Abstract: A first surface of an optical component has a lens function of converging the transmission light from a light source. A second surface reflects the transmission light, converged by the lens: function of the first surface, towards an end face of an optical transmission medium as the destination of transmission. The light reflected by the second surface is radaited from a coupling surface. Since the light beam from the light source is directed towards the optical transmission medium by exploiting the total reflection of light, a high-reflection multi-layer film or a polarization beam splitter film, required in a conventional apparatus employing a polarization beam splitter, is unneeded, with the result that the film forming cost or the cost in bonding two prisms used for fabricating the polarization beam splitter may be dispensed with. In this manner, the production cost or size of the apparatus can be reduced withut lowering the transmission/reception performance.

Abstract: An optical transmitter-receiver according to the present invention is an optical transmitter-receiver connected to an optical fiber used for a single-core two-way optical communication channel for making a first optical signal S1 to be sent incident upon the end of the optical fiber and receiving a second optical signal S2 sent via the optical fiber. The above optical transmitter-receiver is provided with emission means for emitting a first optical signal S1, an optical system for making a first optical signal S1 from the emission means incident upon the incident end of the optical fiber in a direction R1 different from a direction in which a second optical signal S2 is outgoing from the end of the optical fiber and light receiving means for receiving a second optical signal S2 outgoing from the end of the optical fiber.

Abstract: Disclosed is an optical disc apparatus compatible with both ROM type and RAM type optical discs having high density and large capacity. An optical disc apparatus includes: a disc control device including an optical disc (a magneto-optical disc), a spindle motor for rotating the optical disc, an objective lens for forming a light spot on the optical disc, and a control drive device which controls and drives the objective lens in the tracking direction of the optical disc, a semiconductor laser serving as a light source, a signal light transfer having a polarization-preserving optical fiber for guiding output light from the semiconductor laser to the objective lens, ¼ wave plates provided in optical paths on both sides of the polarization-preserving optical fiber, and signal detecting devices (polarization beam splitter and photo detectors) for detecting a servo signal, etc. from the reflected light from the optical disc.

Abstract: A recording and/or reproducing method for using an optical disc in the recording or reproduction data on or from the optical disc in predetermined data-length units. In a recording operation, the recording and/or reproducing method includes the step of dividing data read from the optical disc in the predetermined sector length, rewriting inputted data into the desired sector which is divided from the predetermined data-length inputs and recording the data including the rewritten sector on the optical disc in the predetermined data-length units. In a reproducing operation, the recording and/or reproducing method includes the step of reading the data having from the optical disc in the predetermined data-length units, dividing the data read from the optical disc in the predetermined data-length units into the predetermined sector length and transferring data of the reproduced desired sector as output data.

Abstract: An optical card recording apparatus comprises a card holding member (17) on which an optical card is loaded at a predetermined position, a driving device (12,14,15,16, 17G,22,24,25) for moving the card holding member (17) in relation to a fixed member, and a movement control device (45, 51) operative to control the driving device (12,14,15,16, 17G,22,24,25) so as to place the card holding member (17) at a reference position in relation to the fixed member and then to move the card holding member (17) from the reference position or a position at which the card holding member (17) reaches after moving from the reference position by a selected distance in a predetermined manner, so that record tracks are formed on the optical card in a predetermined arrangement by a light beam caused to be incident upon the optical card loaded on the card holding member (17).

Abstract: Apparatus for controlling a tone arm is provided with a horizontal drive motor for moving the tone arm in the horizontal direction, a horizontal velocity detector connected to the same rotating shaft as the tone arm so as to move concurrently with both the tone arm and the horizontal drive motor, a control circuit having a motional feedback loop to energize the horizontal drive motor in accordance with a desired pre-set velocity signal and a fedback detected velocity signal.

Abstract: A tone arm assembly provided with a motor for moving a tone arm in a horizontal direction with respect to a record disc, a servo circuit for keeping the moving velocity of the tone arm constant, and a positioning servo circuit to operate when the tone arm reaches a reproducing position, in which the positioning servo circuit and the velocity controlling servo circuit are combined together thereby to stop the tone arm quickly at a predetermined position.