Nec Corporation

Yasushi Hara

Hiroaki Tanaka

Kenichi Nomura

Takanori Fujisawa

Norio Yanagi

Junichi Hayasaka

In order to stabilize the characteristics of reception of an optical signal received via a transfer path, this optical receiver is provided with: a local beam output means; a light receiving means; a photoelectric conversion means; a measuring means; a control means; and a comparing means, the comparing means, when the control meanssweeping the wavelength of the local beam in a predetermined wavelength range with respect to the central wavelength of the optical signal, generating difference data between a spectrum based on a result of the measuring, by the measuring means, of the electric signal in accordance with a change in the wavelength of the local beam and a preset reference spectrum.

Optical transfer system, optical transmitter, and optical communication method

A test controller of a transmitting-side optical wavelength multiplexing transmission apparatus of the present invention includes a wavelength tunable filter controller configured to control a center wavelength and a wavelength band of an optical signal that a wavelength tunable filter transmits; and a test transponder controller configured to control a wavelength band of a test optical signal generated by a test transponder and a wavelength interval between the test optical signal and the optical signal that the wavelength tunable filter transmits. A test controller of a receiving-side optical wavelength multiplexing transmission apparatus of the present invention includes a wavelength tunable filter controller configured to control a center wavelength and a wavelength band of an optical signal that a wavelength tunable filter transmits; and a test transponder controller configured to control a center wavelength and a wavelength band of a test optical signal received by a test transponder.

Test controller, optical wavelength multiplexing transmission apparatus, test control circuit and method, and program recording medium

In order to identify occupied bands in an optical transmitter with high accuracy, a band identifying circuit includes an optical intensity controller configured to change, by a prescribed level, an optical intensity of an optical signal outputted from a target-of-identification optical transmitter among a plurality of optical signals respectively outputted from a plurality of optical transmitters, constituting a wavelength-multiplexed optical signal, and having mutually different wavelengths, a spectrum acquisition circuit configured to measure an optical intensity of each wavelength of the wavelength-multiplexed optical signal and output a result of the measurement as a spectrum, and a band identifier configured to identify a band occupied by the target-of-identification optical transmitter, based on a change amount of the outputted spectrum.

Band identifying circuit, wavelength-multiplexed optical signal transmission device, wavelength-multiplexed optical signal transmission system, and band identifying method

Present invention provides an optical communication system that controls reception sensitivity of an optical receiver. The communication system () according to the present invention comprising: an optical transmitter () to which an transmission signal is input, and which modulates the transmission signal to an optical signal and transmits the optical signal; and an optical receiver () that receives the optical signal and demodulates the optical signal to an transmission signal. And the optical receiver () includes a photoelectric conversion means () for converting the optical signal into an analog electric signal, a conversion and demodulation means () for converting the analog electric signal into a digital signal and demodulating the signal to the transmission signal, and an amplitude control means () for controlling amplitude of the analog electric signal, and the amplitude control means () controls the amplitude of the analog electric signal in accordance with wavelength dispersion of the optical signal.

Optical communication system, optical receiver, optical receiver control method, and non-transitory computer readable medium

Provided are a multiplexing circuit for multiplexing a memory output signal output by a memory for temporarily accumulating a low-order group signal with an overhead bit necessary for optical digital transmission and a pattern generation circuit for generating an unfixed pattern having no fixed value. An unfixed pattern is applied to the multiplexing circuit while the memory outputs a fixed pattern. A selection circuit provided between the multiplexing circuit and the memory selects an unfixed pattern between a fixed pattern output by the memory and an unfixed pattern output by the pattern generation circuit.

Circuit for preventing transmission of a fixed pattern of optical digital transmission equipment

A bit rate converter capable of avoiding slip of data in a memory for use in bit rate adjustment is disclosed. A phase comparator compares a write address and a read address of the memory to produce a phase difference. The write address is ahead of the read address in the memory. A stuffing rate controller selects one of a plurality of preset fixed stuffing rates depending on the phase difference. A stuff pulse inserter inserts a stuff pulse into readout data from the memory at the selected stuffing rate. When normally operating, a normal fixed stuffing rate is selected. When the phase difference is small than a lowest threshold value, a higher fixed stuffing rate is selected. When the phase difference is greater than a highest threshold value, a lower fixed stuffing rate is selected.

Bit rate converter with controlled stuffing rate

A dummy bit elimination device in a coding apparatus for use in a submarine cable system. The dummy bit elimination device has a converter for eliminating only dummy bits from FEC (Forward Error Correction) code. The coding apparatus has an optical-to-electrical signal transducer, a demultiplexer, a coder for generating an FEC code, a multiplexer for multiplexing inputs, and an electrical-to-optical signal transducer. The dummy bit elimination device is inserted between the coder and the multiplexer so that the outputs of the coder are fed to the converter and an outputs of the converter are fed to the multiplexer.

Dummy bit elimination device and coding apparatus for FEC code word

An optical communication network system that communicates by wavelength division multiplexing. The optical network system includes a plurality of communication devices for communicating with one another. At least one of the communication devices is connected as a connection communication device to each of plural multi/demultiplexing devices. A plurality of optical signals are assigned to as assigned optical signals to the communication devices, respectively. The optical signals have wavelengths different from one another, respectively. Each of the optical multi/demultiplexing devices includes a supplying section for supplying the connection communication device with a specific one of the assigned optical signals that is assigned to the communication device. The supplying section may be a bandpass filter for allowing the specific optical signal to pass therethrough and supplies the specific optical signal to the connection communication device.

Optical communication network system with wavelength-based signal

An optical branching apparatus for branching optical transmission lines as reverse and forward links through a plurality of ports includes a plurality of demultiplexing units, a plurality of multiplexing units, and a plurality of optical transmission media. Each of the plurality of demultiplexing unit is arranged in each of the ports to demultiplex a light beam input from the optical transmission line in accordance with one of a wavelength and a wavelength band. Each of the plurality of multiplexing units is arranged in the each port to multiplex light beams having different wavelengths or wavelength bands demultiplexed by the demultiplexing units of remaining ports and outputs a multiplexed light beam to the optical transmission line. One of the wavelength and the wavelength band is determined in accordance with a combination of an optical transmission source and an optical transmission destination. Each of the plurality of optical transmission media connects the each demultiplexing unit to at least one of the multiplexing units of the remaining ports to perform optical transmission.

Growing community of inventors

Tokyo, Japan

Yasushi Hara