Nec Corporation

Sumitomo Osaka Cement Co., Ltd.

Nec C Orporation

Tadashi Koga

Yasuhiro Aoki

Morihiko Ota

Masaki Sato

Takashi Nakamura

Takaaki Ogata

Hitoshi Oguri

A communication apparatus, a communication system, a communication method, and a non-transitory computer readable medium capable of reducing differences among receiving characteristics of a plurality of quadrature amplitude-modulated signals and optimizing the capacity of transmission signals are provided. A communication apparatus () according to the present disclosure includes a transmitting unit () capable of transmitting a plurality of types of quadrature amplitude-modulated signals, and an addition unit () that adds error correction codes to the quadrature amplitude-modulated signals. Further, the communication apparatus () includes a control unit () that changes the number of bits of the error correction code according to the type of the quadrature amplitude-modulated signal.

Communication apparatus, communication system, communication method, and non-transitory computer readable medium

A local oscillation light output unit; a phase adjustment unit; a polarization control unit; a multiplexing unit; a photoelectric conversion unit; a demodulation unit; and a control unit. The phase adjustment unit adjusts the phase of local oscillation light. The polarization control unit controls polarization rotation of an optical signal. The multiplexing unit multiplexes the local oscillation light output from the phase adjustment unit with the optical signal output from the polarization control unit. The demodulation unit performs a demodulation process based on an electric signal obtained through conversion performed by the photoelectric conversion unit. The control unit, on the basis of information about the reception status of the optical signal, controls the execution of at least one of the phase adjustment of the local oscillation light in the phase adjustment unit and the polarization rotation of the optical signal in the polarization control unit.

Optical receiver and receiving method

A transmitter includes an optical modulator, a drive unit, a deviation identification signal generation unit, and a bias control unit. The deviation identification signal generation unit generates a signal value in accordance with a deviation of a bias voltage of the optical modulator by amplifying a signal value of a dither signal extracted from a modulated signal output from the optical modulator by a factor set for each of a plurality of modulation schemes so as to generate a uniform signal value. The bias control unit generates a bias value at which a center of a variation range, which is a range from a maximum value to a minimum value of the drive signal, corresponds to transmission characteristics of the optical modulator according to one predetermined adjustment method by using the signal value generated by the deviation identification signal generation unit.

Transmitter and bias adjustment method

An optical receiver is provided with: an optical reception circuit which receives wavelength multiplexed light including signal light, converts the signal light into an electrical signal by coherent detection of the signal light using local oscillation light, and outputs the power of the local oscillation light, the bit error rate of the signal light and the electrical signal; and a controller which monitors the power of the local oscillation light and the bit error rate, calculates the signal-to-noise ratio of the signal light on the basis of the power of the local oscillation light and the bit error rate, and finds the number of wavelengths of the wavelength multiplexed light and the power per wavelength of the signal light on the basis of the signal-to-noise ratio and the power of the local oscillation light.

Optical receiver and optical reception method

In order to provide an optical modulator capable of controlling a bias voltage to correspond to transmission characteristics of a modulation means even when a multi-level modulation scheme is applied, an optical modulatoris provided with: an amplitude information control meansthat generates amplitude information for controlling the amplitude of an information signal to correspond to transmission characteristics of a modulation means, adds a dither signal to the amplitude information, and outputs the amplitude information; a bias value control meansthat generates and outputs a bias value for controlling the center of the amplitude of the information signal to correspond to the transmission characteristics of the modulation meansa data output meansthat corrects the amplitude of information data on the basis of the amplitude information, and outputs the information data as the information signal; the modulation meansthat corrects the center of the amplitude of the information signal on the basis of the bias value, modulates continuous wave light by using the information signal, and outputs a modulation signal; and an adjustment meansthat extracts, from the modulation signal, the dither signal added to the amplitude information, and adjusts the amplitude information and the bias value such that the differential value of the intensity of the dither signal added to the amplitude information becomes zero.

Optical modulator, optical transmitter, and optical modulation method

A signal reception processing apparatus includes a digital signal processing unit that calculates a first Q value based on distribution of the symbols of the demodulated signal and distance between the symbols of the demodulated signal, and an error correction unit that outputs corrected signal as a demodulation electric signal, and calculates a second Q value based on an error rate at the time of the correction, and a control unit that calculates a penalty that indicates degradation quantity of signal quality caused by a nonlinear optical effect of an optical fiber based on the first Q value and the second Q value.

Signal reception processing apparatus and method for processing received signal

An exemplary aspect of the invention is an optical transmitter that emits a light signal, including: a light source; a Mach-Zehnder optical modulator; a modulator driver; a wavelength information holder; and a driving voltage controller, wherein the Mach-Zehnder optical modulator modulates the light intensity of output light from the light source by use of a modulator driving signal, the modulator driver outputs the modulator driving signal according to an input data signal, the wavelength information holder holds wavelength information on the output light of the light source, the driving voltage controller outputs, to the modulator driver, a control signal for setting the latest driving voltage, according to the wavelength information from the wavelength information holder.

Optical transmitter with driving voltage control and method

An optical receiver includes an optical amplifier configured to amplify an input optical signal and output an amplified optical signal; and a light receiving element configured to convert the amplified optical signal into an electrical signal and output the electrical signal, and the optical amplifier controls an output-level of the amplified optical signal according to a wavelength of the input optical signal.

Optical receiver, optical receiving apparatus using the optical receiver and optical receiving method thereof

When a PLL circuit is used to extract and recover clock component from an information data signal, where an optical receive signal has been converted into an electrical signal, and to monitor the frequency of a recovered clock, a low frequency section frequency detection circuit having a BPF (band-pass filter) where transmission center frequency has been shifted to higher frequency relative to center frequency of the electrical signal and a high frequency section frequency detection circuit having a BPF where the transmission center frequency has been shifted to lower frequency are provided in parallel. Utilizing a slope on one side of each transmission characteristic of the BPF makes it possible to set detection frequency freely and accurately. Therefore, a frequency detection circuit without using a special device in an optical transmitter/receiver, capable of easily detecting accurate frequency shift of f&#xb1;&#x394;f or more, and of low price and high performance, can be obtained.

Frequency detection circuit, optical receiver and optical transmission system using the same

A wavelength division multiplex transmission apparatus capable of transmitting a plurality of 1.55 micron band signal light of different wavelengths by multiplexing the wavelengths is disclosed. A plurality of dispersion compensation units are serially connected, and each executes dispersion compensation with a particular signal light and outputs a respective compensated light. Such signal light output from the dispersion compensation units are combined and then output to a transmission path. Monitor light lying in a 1.3 micron band not susceptible to the operation of an optical direct amplifier is input to the serially connected dispersion compensation units. In each dispersion compensation unit, a photo-detector detects the level of the monitor light. With this configuration, the apparatus is capable of surely detecting faults including the defective connector connection or the shutoff of an optical patch code between the dispersion compensation units.

Wavelength division multiplex optical transmission apparatus

An optical receiver board wherein, a signal light is amplified in an optical fiber amplifier. The amplified signal light is supplied to an electrically driven optical wavelength-tuning filter such as a multi-layered film interference filter, through which a signal light of a predetermined wavelength bandwidth is transmitted. The transmitted signal light is divided into first and second signal lights. The first signal light is converted to an electric signal which is amplified by an equalizing amplifier, and an amplified electric signal is supplied to a discrimination circuit, in which an information electric signal is generated by using a timing signal. The optical wavelength-tuning filter comprises a rotation actuator having a magnet-rotating portion and control coils, and an optical filter member fixed to the top of the magnet-rotating portion. In operation, the wavelength-tuning filter is swept by a sweep signal, so that an electric signal converted from a signal light transmitted through the optical wavelength-tuning filter becomes a predetermined value, and the tracking control is carried out to maximize power of the transmitted signal light. The inclination angle of the optical filter member is changed by controlling currents flowing through the control coils of the actuator, so that a transmission center wavelength of the signal light is adjusted.

Optical receiver board, optical wavelength-tuning filter module used for

A wavelength division multiplexing light transmitting system which can monitor its transmission line. In which, one light among the signal lights to be wavelength multiplexed is defined as an optical fiber transmission line monitor light. A transmitter multiplexes and transmits the monitor light with the other signal lights. These lights are attenuated and introduced to the other transmission line at return circuits 12. A receiver branches the returned lights, selects the monitor light and detects a condition of the transmission line by correlation processing. The system extremely improves a SNR and a detection time of the monitor signal.

Wavelength division multiplexing light transmitting system

It is the object of the invention to eliminate a limitation on the transmission distance of a WDM optical transmission system caused by wavelength dependencies of gains of optical amplification repeaters. The transmission characteristic of optical signal of the transmission system against the signal wavelength can be flatted by using plural kinds of the optical amplification repeaters with different gain peak wavelengths, and the longer transmission distance can be obtained.

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Tokyo, Japan

Tadashi Koga