Nec Corporation

Nec C Orporation

Tetsuyuki Suzaki

Hajime Ishikawa

Naoya Henmi

Hiroshi Nishimoto

Takashi Kuriyama

Yoshihiro Matsumoto

Hiroshi Tezuka

Tomoki Saito

An optical fiber changes a polarization state of a propagating light when at least one of a vibration and a displacement occurs. An optical transmitter inputs a first wavelength light to the optical fiber via a separator, and an optical transmitter inputs a second wavelength light to the optical fiber via a separator. The first and second wavelength lights propagated through the optical fiber in mutually opposite directions are respectively received by optical receivers (and) via the separators (and), and a fluctuation of a polarization is detected in polarization fluctuation detectors (and). A data processing device collects data indicating the fluctuation of the polarization detected by the polarization fluctuation detector and data indicating the fluctuation of the polarization detected by the polarization fluctuation detector.

Optical fiber sensor and optical fiber sensor system

In a receiver operable in response to a data signal, an eye aperture size is detected along a time axis by an eye aperture detection circuit and is controlled by a control circuit so that it becomes a maximum. The eye aperture detection circuit determines different decision time points of the same level arranged along a time axis and judges whether or not an error is caused to occur at each of the decision time points, so as to detect the eye aperture size and to produce detection results. The control circuit processes the detection results in accordance with a predetermined algorithm to successively vary the eye aperture size and to keep the data signal at an optimum amplitude.

Receiver and receiving method capable of detecting an eye aperture size formed by reception data signals

In a matrix switch method, pieces of timing information synchronous with the signal speeds of input data parallelly input to N (N is a positive integer) input terminals are extracted. The respective input data are switched/output to N output terminals through a switch. Output signals from the output terminals of the switch are regenerated by using the pieces of timing information extracted from the corresponding input data. A matrix switch device is also disclosed.

Matrix switch method and device

The present invention generates a reference signal including identification information based on a first coding method and generates data signals by a second coding method different from the first coding method. Next, it time division multiplexes signals by allocating the reference signal to a reference time slot and allocating data signals to time slots of which phase difference between the reference time slot is predetermined, and sends a multiplexed signal. In a receiver side, the reference time slot is detected based on identification information in a transmitted signal.

Time division multiplexing transmitter and decoding circuit used for

This invention relates to methods and apparatus for extracting data of a channel from and for inserting low speed input data into a channel of time division bit multiplex. An optical data transmission system is used for distribution of video signals or information services. A variable frequency divider generates a timing signal by frequency dividing a clock signal by N. The resulting timing signal is phase shifted by M clock periods by inserting one cycle of 1/(N+M) frequency dividing in accordance with a synchronous command signal. With the timing signal, data of a channel is extracted from the time division multiplexed data of N channels by an extracting circuit, such as a D-type flip-flop. With a synchronous signal generated from the timing signal having the same pulse width of the multiplexed data, a low speed input data is inserted into a channel of the multiplexed data of N channels by a selector.

Method of and apparatus for extracting or inserting a signal in a time

A waveguide-type optical device includes a substrate with an electro-optical effect, two adjacent optical waveguides, a signal electrode covering either of the optical waveguides and an earth electrode covering the other optical waveguide and having a segment of the same form as the signal electrode which lies close to the other optical waveguide.

Waveguide-type optical device

The present invention provides a method and device for channel selection for setting at least one channel among N channels as a reference channel, detecting temporal location of the reference channel in a reception side, selecting an arbitrary channel using a relative time difference between the detected temporal location of the reference channel and that of the channel to be selected.

Method and device for channel selection

A method of optical transmission comprises steps of generating a light signal, controlling a wavelength of the light signal in accordance with a correcting signal, and modulating an intensity of the light signal supplied from the light source to generate an output light signal in accordance with a modulating signal. The wavelength change of the light signal generated by the light source coincides with the wavelength change which occurs during the modulating step, so that the wavelength change is cancelled in the output light signal. An optical transmitter used in the method comprises a light source which generates a light signal, a correcting signal generating circuit which supplies the light source with a correcting signal for changing the wavelength of the light signal generated by the light source, and an optical modulator which modulates an intensity of the light signal supplied from the light source to generate an output light signal in accordance with a modulating signal.

Method of optical transmission and optical transmitter used in the same

A plurality of transmitting signal lights are supplied from a semiconductor laser light source which is modulated by a current having adjusted amplitude and phase injected thereinto in an optical transmitting apparatus. The signal lights are modulated in intensity by a plurality of external modulators, and a time-difference is applied among the signal lights. Thus, the signal lights are combined to provide a transmitting signal light which is propagated through a transmission line. At this time, a frequency component having a low transmission speed is supplied to the transmission line earlier than a frequency component having a fast transmission speed in compliance with a wavelength dispersion property of the transmission line.

Growing community of inventors

Tokyo, Japan

Tetsuyuki Suzaki