Kabushiki Kaisha Toshiba

Kokusai Denshin Denwa Co., Ltd.

Hiroyuki Ibe

Taro Shibagaki

Takeshi Ozeki

Manish Sharma

Takehiko Atsumi

Hiroshi Kobayashi

Tazuko Tomioka

Sadao Tanikoshi

Katsumi Hirai

Hideaki Yamakawa

Masahide Miyachi

Masatoshi Nakao

Shu Yamamoto

Mitsuru Sugawara

Masatoshi Suzuki

Shigeru Ohshima

Senji Shimanuki

Osamu Kinoshita

Yoshinori Yuki

Kyosuke Dobashi

Toshifumi Tamura

Yoshio Hatate

Hideki Ishibashi

Mitsuko Nakamura

Takako Mori

Hitoshi Takahira

Hiroyuki Inamura

Yoichi Hirayama

A protection path reservation method which reserves protection paths to avoid a node failure for each transmission path on a network formed of a plurality of nodes, comprising assuming the nodes as an imaginary failure node in turn in a condition in which the node failure is not present in the network, and selecting N neighbor nodes connected to the imaginary failure node through N links, wherein the imaginary failure nodes sequentially transmit protection path reservation request messages to neighbor nodes, and the nodes which have received the protection path reservation request messages sequentially, one by one, reserve N&#x2212;1 protection paths starting from the nodes.

Protection path reservation method and node unit

An optical modulator includes a phase modulator configured to drive light with an NRZI-coded drive signal for phase modulation and an intensity modulator to modulate the intensity of a phase-modulated NRZI-coded optical signal received from the phase modulator. The operating point of the intensity modulator is set such that the output of the intensity-modulated optical signal is eliminated when the NRZI-coded optical signal is not varied.

Apparatus and method for optical modulation

A point-to-multipoint communication system that is well operative for transmitting megabytes of information in the form of a signal burst. Each slave unit temporarily stores a signal and measures the amount of the signal information before transmitting the signal. A master unit requests that slave units report the measured amounts of information, and they give reports to the master unit. On the basis of the reports from the slave units, the master unit determines an allowable amount of information for each slave unit and permits the slave units to transmit the stored signals according to the request from the master unit. The interval between the reports from the slave units to the master unit can be varied.

Point-to-multipoint communication system

In a cable network system of this invention, GSUs are installed in almost all subscriber residences. A G-STB or a G-MDM is set for a subscriber who wants to receive bidirectional services. Alternatively, an NGA is attached to an existing N-STB or N-MDM. The presence of an upward transmission signal from an in-home device is monitored in the G-STB, the G-MDM, or the NGA. While the upward transmission signal is detected, a transmission indication signal is supplied to the GSU. Only while the transmission indication signal is detected, the GSU sets a gate switch in an ON state. On the other hand, while no transmission indication signal is detected, the GSU keeps the gate switch in an OFF state.

Cable network system with ingress noise suppressing function

A user apparatus periodically detects the mount state of any terminal interface card, and transmits, to a center apparatus, configuration information indicative of the configuration of the user apparatus and including the detection result, when responding to a request for delay time measurement. The center apparatus recognizes and manages the configuration of the user apparatus on the basis of the configuration information. When newly mounting or removing of a terminal interface card has been recognized, the center apparatus performs newly setting releasing of a destination identifier corresponding to the mounted or removed terminal interface card, and notifies the user apparatus of the newly set destination identifier. The user apparatus, in turn, manages identification information sent from the center apparatus, in relation to the terminal interface unit corresponding to the information. As a result, exchange, addition or cancel of communication services which the user uses can be performed easily.

Communication system, user apparatus, center apparatus, and terminal interface unit for use in communication system

Light beams emitted from an optical fiber are converted into parallel light beams by a lens, and then allowed to pass through a Faraday device, followed by being converged to an incident end of the optical fiber by a lens. The Faraday device is applied with a magnetic field in a direction of the optical axis thereof from a coil. Moreover, the Faraday device is applied with a magnetic field in a direction perpendicular to the optical axis by a pair of magnets. When an electric current flowing in a coil 74 is changed from I to -I, the direction of a synthesized magnetic field can be rotated. Therefore, by arbitrarily changing the electric current flowing in the coil, polarization of transmission light can be controlled.

Polarization control unit

Light wavelength measuring apparatus with light modulation

An optical network analyzer measures the amplitude characteristics and group delay time dispersion characteristics of an optical circuit device. In the optical network analyzer, the intensity of the light generated by a first light source is modulated by use of a modulation signal having a constant frequency and a constant amplitude. Part of the intensity-modulated light is used as a reference optical signal, and the remaining part is made to pass through the optical circuit device, thus obtaining an optical signal to be measured. The reference optical signal and the optical signal to be measured are photoelectrically converted into electric signals, and the modulated signal components of the electric signals are compared with each other, thus obtaining an amplitude ratio and a phase difference. The optical frequency of the first light source is swept in a constant cycle, and the amplitude ratio and phase difference are displayed on a display device in synchronism with the frequency sweeping. To implement an optical frequency marker, light having an arbitrarily-designated optical frequency is generated by a second light source. The light generated by the second light source is made to join part of the light generated by the first light source, so as to produce a peak at the designated optical frequency. The peak is electrically extracted and superimposed on the amplitude ratio and phase difference displayed on the display device.

Optical network analyzer for measuring the amplitude characteristics and

A digital signal exchange equipment is disclosed which is constructed of a combination of selector modules each constituted by a plurality of gate arrays as a parallel unit in a column direction. The respective gate array comprises a first gate for selecting one line from an n number of first input lines and connecting it to an output line, a second gate for selecting one line from an output line of the first gate and one second input line and connecting it to the second gate and a flip-flop for wave-shaping an output of the second gate and, at the same time, taking synchronization among the respective gate array. The selector module as set forth above is constructed of a semiconductor circuit device. When, in particular, a plurality of selector modules are combined together, they are arranged as a k-column/l-row array in which input bus lines are each connected to each common row and an n number of output lines are connected for each row to an n number of second input lines of the next-row selector module.

Digital signal exchange equipment

A wide-dynamic range light receiver according to the present invention is constructed such that a non-linear impedance element is connected in series to a light-receiving element, and a resistor and a capacitor are connected in series between a connection node of the light-receiving element and the non-linear impedance element and an input terminal of a low-noise amplifier. The impedance of the non-linear impedance element increases as the output of the light-receiving element approaches a minimum reception light level, and the non-linear impedance element is finally set in the non-conductive state. Thus, at the minimum reception light level, the output current of the light-receiving element is supplied, with little loss, to the low-noise amplifier via the pure resistor and the capacitor. In addition, the impedance of the non-linear impedance element decreases exponentially in accordance with the increase in the input of the light-receiving element. Consequently, the output current of the light-receiving element begins to flow into the non-linear impedance element from a certain point, and the current to the low-noise amplifier is limited.

Wide-dynamic range light receiver

In a frame synchronization circuit, a serial data signal, which includes a frame synchronization code constituted by an M number of bits in one frame, is converted by a serial/parallel converting circuit to a parallel data signal of a 2M-1 number of bits. An M number of pattern detectors of a first synchronization detecting circuit detect the code pattern of the first block of the frame synchronization code from the parallel data signal. A selection signal generating circuit holds outputs of the pattern detectors, and outputs them as a selection signal designating the bit position allotted to the pattern detector which detects the synchronization code pattern. An output of the serial/parallel converting circuit is delayed by a time required for the above-mentioned processing, and supplied to a selector, which selectively outputs an M-bit data signal corresponding to the bit position designated by the selection signal.

Frame synchronization circuit

A laser device according to the present invention having a semiconductor laser which has at least two longitudinal modes .lambda..sub.0 and .lambda..sub.1 both of which are able to oscillate, and oscillating at the single longitudinal mode .lambda..sub.0. The device further comprises input means which inputs a wave nearly coincident with .lambda..sub.1 to the semiconductor laser to switch the oscillating wavelength from .lambda..sub.0 to .lambda..sub.1. The semiconductor laser maintains its oscillating wavelength .lambda..sub.1 even if the intensity of said wave input from said input means reduces.

Oscillation mode switching laser devices

N framing units block N-channel input digital signals, respectively, to provide blocked signals. The framing units respond to a common block synchronization signal from a multiplexing unit to provide the blocked signals in a time relation suitable for multiplexing. The multiplexing unit multiplexes the blocked signals from the framing units to provide a multiplexed signal (higher-order group signal).

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Yokohama, Japan

Hiroyuki Ibe