Nec Corporation

Satomi Shioiri

Kiyoshi Fukuchi

Hitoshi Takeshita

Toshiharu Ito

Emmanuel Le Taillandier De Gabory

Kazuo Takagi

Makoto Shibutani

Masaki Umayabashi

Masaaki Soda

Hiroyoshi Tanabe

Takenori Morikawa

Toshiharu Itou

A method is provided for setting a timing of phase modulation by a target phase modulator within an optical transmitter which performs 2order phase shift keying, n being a natural number equal to or more than two. The method is provided with: feeding a specific pattern to the optical transmitter to allow the xPSK transmitter to emit an optical carrier in accordance with the specific pattern; receiving the optical carrier by a delay interferometer; converting a pair of light signals emitted from constructive and destructive outputs of the delay interferometer into an electrical signal; detecting a peak to peak value of the electrical signal; and setting the timing of the phase modulation by the target phase modulator so as to minimize the peak to peak value of the electrical signal.

Method and system for setting timing of phase modulation of xPSK transmitter

In the optical communication device and the optical communication system using DPSK modulation whose cost is low, whose size is small and whose power consumption is low, the N:1 multiplexergenerates a serial signal by multiplexing a parallel signal coded by the DPSK modulation coding unitsbit by bit on a time division basis. The electric-phase modulation optical converterconverts a serial signal into a phase modulation light. The N-bit delay interferometerexecutes DPSK decoding with respect to a phase modulation light by comparison with an N-bit preceding optical signal. The optical-electric signal converterconverts a decoded intensity modulation light into an electric signal. The N:1 demultiplexerdivides an electric signal converted by the optical-electric signal converterinto a number N of signals bit by bit on a time division basis.

DPSK modulation-demodulation method, and optical communication device and optical communication system using the same

Transmission-side communication apparatususing a DQPSK (differential quadrature phase-shift keying) scheme is provided with: optical carrier generation sectionwhich generates an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period; and modulation sectionwith which DQPSK-modulates the optical carrier generated by the optical carrier generation means in accordance with a modulation signal at an interval of the symbol period. There are provided: single delay interference sectionwhich receives an optical signal obtained by DQPSK-modulating an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period and outputs an output light obtained by causing the optical signaland a delay optical signal thereof to interfere with each other; and photoelectric conversion sectionwhich converts the output light outputted by the delay interference means to an electric signal.

Optical communication system, optical communication method and optical communication apparatus

The present invention converts each of the optical differential signals from DPSK demodulator from an optical signal into an electrical signal by using optical-electrical signal converters. Thereafter, each electrical signal is subjected to amplification adjustment at an appropriate amplification factor by variable amplifier, and an appropriate delay amount is added to each electrical signal by variable delay line, and thereafter data discrimination is performed by discriminator. Since two differential signals after DPSK demodulation are subjected to amplitude and delay adjustments, the need for optical parts is obviated enabling the use of electric circuits which can be integrated. Thus, the cost of the optical reception device will be reduced. Moreover, the since electric signals whose phases and amplitudes are equalized are inputted to discriminator, erroneous determination of data at discriminator will be reduced.

Optical reception device and optical reception method

The present invention provides a light receiving apparatus using the DQPSK demodulation method. The light receiving apparatus comprises: one Mach-Zehnder interferometer for branching a received light signal into light signals at two arms to allow the branched two light signals to interfere with each other; one balanced photoelectric converter for converting the two interfered light signals, by using the Mach-Zehnder interferometer, into an electric signal corresponding to a difference between light intensities of the two light signals; and a phase adjuster for dynamically shifting the phase of a light signal passed through one of the two arms at the Mach-Zehnder interferometer.

Light receiving apparatus using DQPSK demodulation method, and DQPSK demodulation method

In a communication system in which a plurality of communication terminals sequentially transfer data to a server during the respective transmission permissible periods assigned to the respective communication terminals, the communication terminal transfers a preamble for synchronization to the server at a time of starting the transmission permissible period, converts a data frame for every 8 bits into every 10 bit-code, and transmits to the server, the signal string with a code indicating the head added there, during the transmission permissible period, and turns a communication to the server into a zero signal state, during a period other than the transmission permissible period, while the server establishes a synchronization by reading the preamble for synchronization inserted into the signal string received from each of the communication terminals, converts a portion of the zero signal state of the signal string into a predetermined special code string, and inversely transforms the received signal string into the data frame before the coding.

Communication system including several communication terminals and server, its communication terminal, its server and data transfer control program

Transmission delay time measurement is performed on a signal propagation path between respective points of two printed circuit boards connected by a coaxial cable. Measurement is made of a frequency-domain response of the cable and a first time-domain response of the propagation path at its sending point and a second time-domain response of the propagation path at its receiving point. From the first time-domain response and the frequency-domain response, estimation is made of a third time-domain response of the propagation path that would be observed at the receiving point if there is no waveform distortion on the surface of the printed circuit boards. Time-domain correlation is calculated between the second and third time-domain responses. A first delay time is determined from the estimated time-domain response and a second delay time is determined from the correlation. The first and second delay times are summed to yield the transmission delay time of the propagation path.

Apparatus and method for measuring transmission delay time of a signal propagation path between printed circuit boards

A clock identification and reproduction circuit which synchronizes a clock signal with an input signal includes a voltage controlled generator for generating a clock signal, a phase comparator for detecting a phase difference between an input signal and a clock signal to generate a phase difference signal according to the phase difference, and a filter for synchronizing a clock signal of the voltage controlled generator in response to a phase difference signal, in which the phase comparator generates a phase difference signal when a specific pulse waveform of a pulse of an input signal changes.

Clock identification and reproduction circuit

In order to produce a photo-mask for a modified illumination, corrective patterns are added to and/or deleted from each target area of a design pattern so as to minimize a deformation of an optical image on a photo-resist layer, and the corective patterns are calcualted by using algebraic equations without a trial-and-error.

Growing community of inventors

Tokyo, Japan

Satomi Shioiri