Abstract: In secret communication using a Y-00 protocol, provided is a data communication apparatus which realizes reduction in a random number generation speed by using a plurality of random number generators, and which also ensures security. The data communication apparatus includes: a plurality of random number generation sections 111a to 111f for generating random numbers, which are each a multi-level pseudo random number, by using predetermined key information; and a multi-level signal modulation section 112 for selecting a level, from among multi-levels previously prepared, the level corresponding to information data and a multi-level sequence, which is composed of a combination of values of the random numbers outputted from the plurality of random number generation sections, and for generating a multi-level modulated signal including a noise having a predetermined noise level by using the selected level.

Abstract: In an optical transmission system in which a pulse signal is converted into an optical signal before transmission, a pulse signal demodulation device capable of correctly demodulating the pulse signal is provided. An optical-to-electrical conversion section (31) converts a received optical signal into an electrical signal, and outputs the electrical signal as a received signal. A reception waveform information calculating section (33) outputs, as reception waveform information, information about a shape of a waveform of a short-pulse signal on which a distortion occurring during the time when a short-pulse signal is converted into an optical signal to when the optical signal is converted into a received signal by the optical-to-electrical conversion section (31), is reflected.

Abstract: In an optical transmission system in which a pulse signal is converted into an optical signal before transmission, a pulse signal demodulation device capable of correctly demodulating the pulse signal is provided. An optical-to-electrical conversion section (31) converts a received optical signal into an electrical signal, and outputs the electrical signal as a received signal. A reception waveform information calculating section (33) outputs, as reception waveform information, information about a shape of a waveform of a short-pulse signal on which a distortion occurring during the time when a short-pulse signal is converted into an optical signal to when the optical signal is converted into a received signal by the optical-to-electrical conversion section (31), is reflected.

Abstract: Modulators respectively modulate baseband signals into IF signals having different frequencies. A multiplexer multiplexes the IF signals. An electrical-optical converter intensity modulates the multiplexed IF signals into optical signals. A local oscillation signal source outputs a predetermined local oscillation signal. An external modulator intensity-modulates the optical signal using the local oscillation signal. An optical branching portion branches the intensity-modulated optical signal and respectively outputs branched optical signals to radio base stations. An optical-electrical converter converts the optical signal into an electric signal, to obtain an RF signal by frequency-converting the IF signal. An antenna only transmits a component having a desired radio frequency extracted in a band filter from the RF signal to a subscriber terminal.

Abstract: Provided is a data communication apparatus which is highly concealable and significantly increases time necessary for an eavesdropper to analyze cipher text. A multi-level code generation section (156a) generates, by using predetermined key information, a multi-level code sequence in which a signal level changes so as to be random numbers. The multi-level processing section (111b) combines a multi-level code sequence and information data, and generates a multi-level signal having a level corresponding to a combination of the multi-level code sequence and the information data. In the multi-level code generation section (156a), a random number sequence generation section (157) generates a binary random number sequence by using the predetermined key information. A multi-level conversion section (158) generates a multi-level code sequence from the binary random number sequence in accordance with a predetermined encoding rule.

Abstract: An angle modulator having an excellent noise characteristic and an excellent distortion characteristic independent of an unwanted wave component of an optical modulation signal is provided. The angle modulator (10) includes an optical SSB modulation section (103a), an optical SSB-SC modulation section (104a), and an optical angle modulation section (105). By performing intensity modulation on an output signal of the optical SSB modulation section (103a) at the optical SSB-SC modulation section (104a), an unwanted angle modulated signal is prevented from overlapping with an angle modulated signal outputted from an optical detection section (107). Further, by a filter (108) filtering only an angle modulated signal component which does not include the unwanted wave component among the angle modulated signal components outputted from the optical detection section (107), a distortion characteristic after angle demodulation can be prevented from deteriorating.

Abstract: An optical identification signal generation section electrical-to-optical-converts and emits identification information. A modulation section modulates information data in a predetermined modulation type determined from the identification information. An optical data signal generation section electrical-to-optical-converts and emits the modulated information data. A two-dimensional optical-to-electrical conversion section receives the optical identification signal and acquires screen information including an image of the optical identification signal. An information reading section reads predetermined pixel information from the screen information and reproduces the identification information. An optical-to-electrical conversion section optical-to-electrical-converts the optical data signal. A demodulation section demodulates the information data in the predetermined demodulation type determined from the identification information, and reproduces the information data.

Abstract: A method of manufacturing of power transmission chain 1 by interconnecting plural link plates 2 with pins 3. Individual pin pairs 3 are arranged and temporarily fixed to places. The link plates 2 are sequentially stacked in layers by press-fitting respective through-holes 4 of the link plates 2 about the respective pin pairs 3, whereby the link plates 2 are interconnected to form a circular chain (an endless loop). Subsequently, the individual pin pairs 3 are released from the temporarily fixed state. Thus, the manufacture of the power transmission chain 1 is decreased in the number of operation steps, so that the chain may be assembled easily.

Abstract: A data communication apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. In a data transmitting apparatus 101, a multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. A multi-level processing section 112 generates a multi-level signal 13 having a plurality of levels each corresponding to a combination between information data 10 and the multi-level code sequence 12. A level conversion section 113 divides the plurality of levels of the multi-level signal 13 into several groups, and allocates one level of a converted multi-level signal 21 to a plurality of levels included in each of the several groups in an overlapped manner. The level conversion section 113 then converts the multi-level signal 13 into the converted multi-level signal 21.

Abstract: An optical transmitting circuit (2) modulates multimode oscillation light using an information signal, subjects at least one oscillation-mode light beam of the multimode oscillation light to a predetermined operation, and outputting the result to an optical transmission channel. An optical receiving circuit (8) receives an optical signal transmitted through the optical transmission channel, subjects the received optical signal to an operation reverse to the predetermined operation to recover an optical signal as it was before being subjected to the predetermined operation, and converting the recovered optical signal into an electrical signal, thereby reproducing the information signal.

Abstract: An optical packet exchanger is provided which prevents a transmittable capacity of an information signal from decreasing, and which facilitates the extracting an address signal even if a modulation speed for the information signal becomes high. An optical modulation section (102) outputs an optical packet obtained by subjecting output light from a light source (101) to an intensity modulation using an information signal and a phase modulation using an address signal corresponding to a transmission destination for the information signal. An optical splitter section (301) splits the optical packet into two optical packets. An address reading section (302) reads the address signal from the phase of one of the optical packets output from the optical splitter section (301). Based on the address signal output from the address reading section (302), a path switching section (303) determines an output port for the other optical packet output from the optical splitter section (301).

Abstract: Provided are a data transmitting apparatus and a data receiving apparatus which use a Y-00 protocol and are capable of preventing an eavesdropper's decryption based on a transition pattern of a multi-level signal level. The data transmitting apparatus 101,103 of the present invention includes: a multi-level code generation section 111 for generating, by using predetermined key information 11, a multi-level code sequence 12 in which a value changes so as to be approximately random numbers; and a multi-level signal modulator section 112,125 for generating a converted multi-level signal 23 in accordance with information shared with the receiving apparatus 201,203, the multi-level code sequence 12 and information data 10, modulating the converted multi-level signal 23 in a predetermined modulation method, and outputting a resultant modulated signal 14. The converted multi-level signal 23 is a signal having a plurality of signal point allocations which are different from one another.

Abstract: Modulators respectively modulate baseband signals into IF signals having different frequencies. A multiplexer multiplexes the IF signals. An electrical-optical converter intensity modulates the multiplexed IF signals into optical signals. A local oscillation signal source outputs a predetermined local oscillation signal. An external modulator intensity-modulates the optical signal using the local oscillation signal. An optical branching portion branches the intensity-modulated optical signal and respectively outputs branched optical signals to radio base stations. An optical-electrical converter converts the optical signal into an electric signal, to obtain an RF signal by frequency-converting the IF signal. An antenna only transmits a component having a desired radio frequency extracted in a band filter from the RF signal to a subscriber terminal.

Abstract: The signal converter of the present invention receives a multichannel video signal and converts the video signal into a microwave signal, the phase of which has been modulated with the video signal. The signal converter includes: a laser light source; a modulating section for modulating the phase of output light of the laser light source with the multichannel video signal and modulating the intensity of the output light with the microwave signal; and a light receiver for receiving the output light modulated by the modulating section and for outputting the microwave signal, the phase of which has been modulated with the multichannel video signal.

Abstract: An optical modulator comprises an electrode 21 which applies to an optical waveguides 12 of a Mach-Zehnder type optical interference system a first electric signal based on an alternating current signal S1 and a direct current bias V1, an electrode 22 which applies to an optical waveguide 13 of the Mach-Zehnder type optical interference system a second electric signal based on an alternating current signal S2 and a direct current bias V2, and a bias setting section 41 which sets average direct current levels of the first and second electric signals based on signal frequency information D1 which indicates a magnitude relation between a maximum frequency of the alternating current signal S1 and a maximum frequency of the alternating current signal S2.

Abstract: A dynamic range of intensity modulation is set to range from a maximum intensity Smax to a minimum intensity Smin. A difference ?(=Smax?Smin) between the maximum intensity Smax and the minimum intensity Smin is divided by the number 2M of multilevel signals. Thus, a distance (an intensity difference) between adjacent signals is [?/2M]. The number 2M of multilevel signals is selected such that the distance [?/2M] between adjacent multilevel signals (between an intensity Si and an intensity Si+1) is sufficiently buried within a range of quantum fluctuations obtained when heterodyne measurements are made or buried within a range of quantum shot noise obtained when a direct detection is made. Bases of a basis group are each positioned for intensity signals so as to have a high intensity and a low intensity between which a distance is set to be a certain value smaller than a middle point intensity [?/2].

Abstract: Modulators respectively modulate baseband signals into IF signals having different frequencies. Multiplexers multiplex the IF signals. A local oscillation signal source outputs a predetermined local oscillation signal. An external modulator intensity-modulates an optical signal using the local oscillation signal. An optical branching portion branches the intensity-modulated optical signal. Modulators respectively modulate the multiplexed IF signals onto the branched optical signals and then output the optical signals to radio base stations. Optical-electrical converters convert the optical signals into electric signals and antennas transmit the electrical signals to subscriber terminals.

Abstract: A data communication apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. A multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which signal in which a signal level changes so as to be approximately random numbers. A multi-level processing section 112 combines information data 10 and the multi-level code sequence 12, and generates a multi-level signal 13 having a plurality of levels each corresponding to the combination of the information data 10 and the multi-level code sequence 12. A delayed wave generation section 113 generates, based on a delay profile 19, a delayed wave of the multi-level signal 13, combines the generated delayed wave and the multi-level signal 13, and outputs a multipath signal 20. A modulator section 114 modulates the multipath signal 20 in a predetermined modulation method, and outputs a modulated signal 14.

Abstract: A data transmitting apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. The multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. The multi-level processing section 112 generates a multi-level signal 13 having a level which corresponds to a combination between information data 10 and the multi-level code sequence 12. The error signal generation section 113 generates an error signal 21 which changes randomly. The accumulation section 114 accumulates the error signal 21, and outputs an accumulated error signal 22. The adding section 116 adds the accumulated error signal 22 to the multi-level signal 13, and outputs a variable multi-level signal 23. The modulator section 117 modulates the variable multi-level signal 23, and outputs a modulated signal 14.

Abstract: An optical brancher branches an input optical signal into two. An optical detector converts one optical signal branched by the optical brancher into an electrical signal. A first controller generates a control electrical signal having a waveform obtained by inverting the envelope of the electrical signal. Based on the control electrical signal, an optical signal generator produces a dummy optical signal having a waveform ?d and an amplitude ?/2. The other signal branched by the optical brancher is delayed by a delay unit for a predetermined time, and then multiplexed by an optical multiplexer with the dummy optical signal from the optical signal generator. An optical amplifier amplifies amultiplexed optical signal. An optical filter separates an optical signal of a wavelength ?1 from the amplified optical signal. Thus, optical signal amplification can be carried out without optical surges.