Abstract: A four fiber ring network optical switching circuit capable of realizing the bridge function at times of the span switching and the ring switching economically by a very compact structure is disclosed. A four fiber ring network optical switching circuit is formed by a 10×8 optical matrix switch having ten input ports and eight output ports, and two branching elements adapted to branch each one of two optical signals among eight optical signals that are inputs of the four fiber ring network optical switching circuit, into two identical optical signals, and to enter the two identical optical signals into two input ports of the 10×8 optical matrix switch such that the eight optical signals are entered into the ten input ports of the 10×8 optical matrix switch as ten optical signals.

Abstract: A phase modulation method and apparatus use a plurality of phase modulators disposed in series to phase-modulate light from a source laser. Modulation by the phase modulators is used to produce phase shifts in the optical signal, with modulation by the first phase modulator producing phase shifts of 0 degrees or 2&phgr; degrees, and modulation by the n-th phase modulator producing phase shifts of 0 degrees or 2n×&phgr; degrees. Here, &phgr; degrees is a predetermined phase level and n is an integer than two and not more than the number of phase modulators. The method is also used to detect and control transmission errors.

Abstract: Signal light (at a wavelength &lgr;s), entered an input terminal from an optical transmission line, inputs a combiner through an optical amplifier. The combiner combines the output light of the optical amplifier and the probe light (at a wavelength &lgr;p) from a probe light source and applies them to an EA modulator. The EA modulator superimposes a waveform of the signal light on the probe light. An optical BPF transmits only the component of the probe wavelength &lgr;p in the output light of the EA modulator. A photodetector converts the output light of the optical BPF into an electric signal, and an amplifier electrically amplifies the output of the photodetector. A BPF extracts the clock component of the input signal light from the output of the amplifier and applies it to a driver. The driver pulsatively drives the probe light source at the same frequency with that of the clock signal from the BPF and adjusts its pulse phase so as to synchronize with the current pulse from the EA modulator.

Abstract: It is an object of the present invention to perform optical pulse separation that employs a clock recovery method that does not necessitate a complex constitution and by means of which operation is stable even during high-speed operation in excess of 160 Gbit/s. Hence, the clock signal required in the optical pulse separation is extracted by means of a clock recovery stage. The clock recovery stage is constituted by an O/E converter that has a reception bandwidth enabling a clock frequency signal to be received, a phase-locked loop for obtaining a recovered clock signal in which the jitter of the time division multiplexed optical signal is faithfully reproduced, an electrical phase delay circuit, and a high Q value bandpass filter, and the like. The time division multiplexed optical signal is received by the O/E converter and O/E converted thereby. The O/E converted electrical signal is supplied to the phase-locked loop.

Abstract: In a signal demultiplexing device formed by a probe light source, a wavelength converter, and a wavelength demultiplexer, the probe light source is formed by a plurality of sub-probe light sources configured to respectively generate the sub-probe lights with the prescribed different wavelengths for respective time-slots, a multiplexer configured to multiplex the sub-probe lights generated by the plurality of sub-probe light sources, and a phase different giving unit configured to give phase differences corresponding to time-slot positions to the sub-probe lights multiplexed by the multiplexer, and to sequentially output the sub-probe lights with the phase differences in correspondence to respective time-slots.

Abstract: A key input device embodying the present invention comprises a seesaw switch unit (4) installed on a sheet (41), and a key rubber (8) installed on the sheet (41) covering the seesaw switch unit (4). A seesaw key (10) is arranged on the surface of the key rubber (8) for depressing the seesaw switch unit (4). The seesaw switch unit (4) comprises a base plate, a dome sheet provided on a base plate having a plurality of dome portions, and a pivotally movable member 6 provided over the dome sheet to depress selectively each dome portion. The depression of the pivotally movable member 6 causes a dome portion to be elastically restorably invertable, to have a contact terminal formed on an inner surface of the dome portion into contact with a contact electrode formed on a surface of the base plate, closing contacts. With the key input device, the device can be made thinner, and the complete waterproof can be achieved with reduced number of components.

Abstract: An optical transmission system comprises a light source to output an optical carrier having a predetermined wavelength, a photoelectric converter, an optical transmission line, an optical circulator to apply an output light from the light source to one end of the optical transmission line and to apply a light through the same end of the optical transmission line to the photoelectric converter, and an optical modulator disposed on the other end of the optical transmission line to return a portion of the light from the optical transmission line as a reference light to the optical transmission line without modulation and to modulate another portion of the light from the optical transmission line with a transmission signal to return it to the optical transmission line as a modulated light.

Abstract: An optical digital regenerator for digitally regenerating an input signal in an intact optical state. A first operating unit has a first probe light generator for generating a first probe light and a first optical operator for converting a waveform of the first probe light output from a first probe light generator according to an optical intensity waveform of the input signal light. A clock extractor extracts a clock component of the input signal light from a photocurrent generated by the first optical operator. A second optical operating unit has a second probe light generator for generating a second probe light pulsed in accordance with the clock output from the clock extractor and a second optical operator for sampling the second probe pulse light output from the second probe light generator.

Abstract: An optical switching system is implemented by providing a transmitting section with a preparatory transmitted optical signal selector and a working transmitted optical signal splitter, which are each implemented by a 1×2 optical space switch, and by providing a receiving section with a receiving optical switch which is implemented by a 2×2 optical space switch, and with a preparatory receiving optical gate which is implemented by a 1×2 optical space switch. This makes it possible to switch between the working system and preparatory system without employing any 4×4 optical space switch, thereby implementing a practical optical switching system without causing such problems as communication interruption during maintenance or impairment of transmission path working efficiency.

Abstract: A braking pressure control apparatus for a hydraulically operated brake, including a first hydraulic system having a first hydraulic pressure source power-operated to pressurize a working fluid and capable of controlling the fluid pressure, for operating the brake, a second hydraulic system having a second hydraulic pressure source operable by an operating force acting on a manually operable brake operating member, to pressurize the working fluid to a pressure higher than a level corresponding to the operating force, for operating the brake, a switching device operable to selectively establish a first state in which the brake is operated with the pressurized fluid delivered from the first hydraulic pressure source, and a second state in which the brake is operated with the pressurized fluid delivered from the second hydraulic pressure source, and a diagnosing device operable to diagnose the second hydraulic system on the basis of the fluid pressure in the second hydraulic system.

Abstract: A four fiber ring network optical switching circuit capable of realizing the bridge function at times of the span switching and the ring switching economically by a very compact structure is disclosed. A four fiber ring network optical switching circuit is formed by a 10×8 optical matrix switch having ten input ports and eight output ports, and two branching elements adapted to branch each one of two optical signals among eight optical signals that are inputs of the four fiber ring network optical switching circuit, into two identical optical signals, and to enter the two identical optical signals into two input ports of the 10×8 optical matrix switch such that the eight optical signals are entered into the ten input ports of the 10×8 optical matrix switch as ten optical signals.

Abstract: A braking system including a brake cylinder, a first hydraulic pressure source having a first pump device for pressurizing a working fluid, a second hydraulic pressure source operable in response to an operation of a brake operating member, to pressurize the fluid to a pressure higher than a value corresponding to an operating force of the brake operating member, and a brake-cylinder-pressure control device operable when the brake cylinder is disconnected from the second hydraulic pressure source, to control the pressure of the fluid pressurized by the first hydraulic pressure source, such that the fluid pressure in the brake cylinder is controlled to a value determined on the basis of the operating force, and wherein an emergency communication device is operated when at least one of the brake-cylinder-pressure control device and the first pump device fails to normally function, to hold the brake cylinder in communication with the second hydraulic pressure source.

Abstract: In a light source for generating light containing multiple wavelengths substantially uniform in intensity, a wavelength demultiplexing element 10 (for example, waveguide-type wavelength selecting filter) demultiplexes input light into a plurality of wavelengths &lgr;1 through &lgr;32. Optical amplifiers 14-1 through 14-32 amplify outputs of the element 10 and applies them to input ports of a wavelength multiplexing element 12. The wavelength multiplexing element 12 wavelength-multiplexes their input. Output of the wavelength multiplexing element 12 is applied to a fiber coupler 16 which, in turn, applies one of its outputs to the wavelength demultiplexing element 10. The optical amplifiers 14 have a gain larger by approximately 10 dB than the loss in the optical loop made of the element 10, optical amplifier 14, element 12 and fiber coupler 16. The other output of the fiber coupler 16 is wavelength-multiplex light containing wavelengths &lgr;1 through &lgr;32.

Abstract: An optical wavelength routing device comprises an arrayed waveguide comprising a plurality of channel waveguides formed on a substrate, a plurality of input waveguides having 12 input ports located on an input side of the arrayed waveguide, a plurality of output waveguides having 16 input ports located on an output side of the arrayed waveguide, an input slab waveguide for coupling the plurality of input waveguides to the arrayed waveguide to provide a first coupling portion on the side of the input waveguide, and an output slab waveguide for coupling the arrayed waveguide to the plurality of output waveguides to provide a second coupling portion on the side of the output waveguide, in which central wavelengths of lights input to the input ports and output from the output ports are controlled such that a difference between a predetermined wavelength and a central wavelength is suppressed within the range of +&dgr;&lgr;/4.

Abstract: In an optical amplifier apparatus for amplifying an incident signal light having wavelengths of 1.06 &mgr;m band, a first optical isolator makes an incident signal light pass therethrough in one direction from an input end to an output end. An optical fiber includes a core mainly composed of silica glass and doped with a predetermined rare-earth element and the other elements, and a cladding of silica glass, and transfers in a single mode the signal light output from the first optical isolator. An optical multiplexer multiplexes an excitation light having an excitation wavelength of 0.8 &mgr;m band with the signal light transferred by the optical fiber, by outputting the excitation light to the optical fiber, and further transfers and outputs the signal light having wavelengths of 1.06 &mgr;m band amplified by induced emission in the optical fiber due to the rare-earth element excited by the excitation light.

Abstract: A key input device embodying the present invention comprises a seesaw switch unit (4) installed on a sheet (41), and a key rubber (8) installed on the sheet (41) covering the seesaw switch unit (4). A seesaw key (10) is arranged on the surface of the key rubber (8) for depressing the seesaw switch unit (4). The seesaw switch unit (4) comprises a base plate, a dome sheet provided on a base plate having a plurality of dome portions, and a pivotally movable member 6 provided over the dome sheet to depress selectively each dome portion. The depression of the pivotally movable member 6 causes a dome portion to be elastically restorably invertable, to have a contact terminal formed on an inner surface of the dome portion into contact with a contact electrode formed on a surface of the base plate, closing contacts. With the key input device, the device can be made thinner, and the complete waterproof can be achieved with reduced number of components.

Abstract: In a signal demultiplexing device formed by a probe light source, a wavelength converter, and a wavelength demultiplexer, the probe light source is formed by a plurality of sub-probe light sources configured to respectively generate the sub-probe lights with the prescribed different wavelengths for respective time-slots, a multiplexer configured to multiplex the sub-probe lights generated by the plurality of sub-probe light sources, and a phase different giving unit configured to give phase differences corresponding to time-slot positions to the sub-probe lights multiplexed by the multiplexer, and to sequentially output the sub-probe lights with the phase differences in correspondence to respective time-slots.

Abstract: In a light source for generating light containing multiple wavelengths substantially uniform in intensity, a wavelength demultiplexing element 10 (for example, waveguide-type wavelength selecting filter) demultiplexes input light into a plurality of wavelengths &lgr;1 through &lgr;32. Optical amplifiers 14-1 through 14-32 amplify outputs of the element 10 and applies them to input ports of a wavelength multiplexing element 12. The wavelength multiplexing element 12 wavelength-multiplexes their input. Output of the wavelength multiplexing element 12 is applied to a fiber coupler 16 which, in turn, applies one of its outputs to the wavelength demultiplexing element 10. The optical amplifiers 14 have a gain larger by approximately 10 dB than the loss in the optical loop made of the element 10, optical amplifier 14, element 12 and fiber coupler 16. The other output of the fiber coupler 16 is wavelength-multiplex light containing wavelengths &lgr;1 through &lgr;32.

Abstract: In a light source for generating light containing multiple wavelengths substantially uniform in intensity, a wavelength demultiplexing element 10 (for example, waveguide-type wavelength selecting filter) demultiplexes input light into a plurality of wavelengths &lgr;1 through &lgr;32. Optical amplifiers 14-1 through 14-32 amplify outputs of the element 10 and applies them to input ports of a wavelength multiplexing element 12. The wavelength multiplexing element 12 wavelength-multiplexes their input. Output of the wavelength multiplexing element 12 is applied to a fiber coupler 16 which, in turn, applies one of its outputs to the wavelength demultiplexing element 10. The optical amplifiers 14 have a gain larger by approximately 10 dB than the loss in the optical loop made of the element 10, optical amplifier 14, element 12 and fiber coupler 16. The other output of the fiber coupler 16 is wavelength-multiplex light containing wavelengths &lgr;1 through &lgr;32.

Abstract: A braking pressure control apparatus for a hydraulically operated brake, including a first hydraulic system having a first hydraulic pressure source power-operated to pressurize a working fluid and capable of controlling the fluid pressure, for operating the brake, a second hydraulic system having a second hydraulic pressure source operable by an operating force acting on a manually operable brake operating member, to pressurize the working fluid to a pressure higher than a level corresponding to the operating force, for operating the brake, a switching device operable to selectively establish a first state in which the brake is operated with the pressurized fluid delivered from the first hydraulic pressure source, and a second state in which the brake is operated with the pressurized fluid delivered from the second hydraulic pressure source, and a diagnosing device operable to diagnose the second hydraulic system on the basis of the fluid pressure in the second hydraulic system.