Fujitsu Corporation

Fujitsu Optical Components Limited

Satoshi Ide

Kazuyuki Mori

Yukito Tsunoda

Tetsuji Yamabana

Toru Matsuyama

Hidehiko Nakata

Tsuyoshi Yamamoto

Tadashi Ikeuchi

Kohei Shibata

Koji Terada

Shinichi Sakuramoto

Mariko Sugawara

Takaya Chiba

Ken-ichi Nakamoto

Takatoshi Yagisawa

Tadao Inoue

Hiroyuki Nobuhara

Jun Matsui

Norio Ueno

Yoshio Sakai

Hideki Oku

Mariko Kase

Toshiyuki Takauji

Hiromasa Tanaka

Kensuke Takahashi

A VCO generates a clock signal. A phase and frequency detector compares phases and frequencies of the clock signal generated by the VCO and an input signal. A charge pump adjusts a control voltage of the VCO based on an output of the phase and frequency detector. An identical digit detector generates a first signal by delaying a rising timing of the input signal by a first time, generates a second signal by delaying a falling timing of the input signal by a second time, detects succession of identical digits in the input signal based on the first signal and the second signal, and stops adjustment of the control voltage by the charge pump when the identical digits succeed by a predetermined number of identical digits or more.

Clock recovery circuit, optical module, and clock recovery method

A signal decision circuit includes: a first decision circuit configured to identify a voltage level of an input signal using an average level of an amplitude of the input signal as a first threshold level; a detection circuit configured to detect an average of an amplitude absolute level based on the average level of the amplitude; a second decision circuit configured to identify a voltage level of the input signal using a second threshold level obtained by adding the average of the amplitude absolute level to the average level of the amplitude; and a third decision circuit configured to identify a voltage level of the input signal using a third threshold level obtained by subtracting the average of the amplitude absolute level from the average level of the amplitude.

Signal decision circuit, optical receiver, and signal decision method

A drive circuit that drives a light emitting element coupled to a first output terminal of a differential circuit, the drive circuit includes: a dummy load provided at a second output terminal of the differential circuit, a resistor coupled between the first output terminal and the second output terminal, two transistors coupled to a voltage source and applying a current to the light emitting element and the dummy load, and a comparative amplifying circuit having a non-inverting input terminal coupled to a reference voltage, an inverting input terminal coupled to at least the first output terminal of the differential circuit via a resistor, and an output terminal coupled to gates of the two transistors.

Light emitting element drive circuit

A receiver circuit includes a first amplifier circuit to differentially amplify differential input signals by a linear operation, a second amplifier circuit configured to differentially amplify output differential signals of the first amplifier circuit by a limiting operation, a feedback circuit, first and second resistors coupled between the feedback circuit and outputs of the first amplifier circuit, and third and fourth resistors coupled between the feedback circuit and outputs of the second amplifier circuit. The feedback circuit amplifies a positive-phase signal that is output from a positive-phase output node thereof coupled to the first and third resistors, and a negative-phase signal that is output from a negative-phase output node thereof coupled to the second and fourth resistors, and feeds back a feedback signal after amplification to the first amplifier circuit.

Receiver circuit

A driving circuit for driving a diode includes at least one differential pair including a first output node and a second output node and configured to switch an output current, a current source configured to adjust the output current, a dummy load coupled to the second output node, a first termination resistor coupled between the first output node and a termination ground, and a second termination resistor coupled between the second output node and the termination ground. The output current is supplied to the diode through the first output node by at least one differential pair.

Driving circuit having a dummy load connected to one output node of a differential pair

An optical transmission system including a transmitting unit to transmit an optical main signal, a receiving unit to receive the optical main signal, and a transmission line through which the optical main signal is transmitted, the optical transmission system includes: an optical transmitter unit configured to be activated or inactivated based on a control signal so as to transmit the control signal, the optical transmitter being included in the transmitting; and an optical receiver configured to receive light with the activate state or the inactivate state of the optical transmitter the optical receiver being included in the receiving unit, wherein the receiving unit regenerates the control signal, based on a power of the received light.

Optical transmission system, control signal transmission method, and optical module

An optical transmission apparatus includes an optical transmitter that includes a light emitting element and a driver circuit for the light emitting element, a temperature sensor that detects a temperature of the optical transmitter, and a controller that switches an operation mode of the optical transmitter from a normal mode to a low-power mode so as to reduce a heating effect to the light emitting element and allow an operation of the light emitting element to continue when the temperature detected by the temperature sensor is equal to or higher than a given temperature.

Optical transmission apparatus and optical transmission method

An optical receiving circuit includes: a first non-feedback amplifier configured to convert a current signal, obtained from a light receiving element in response to an optical signal, into a first voltage signal; a second amplifier configured to convert an input current signal into a second voltage signal, the output signal not being directly fed back to an input side; a differential amplifier configured to perform differential amplification on the first voltage signal and the second voltage signal and to output an in positive signal and a negative signal obtained through the differential amplification; and an offset compensation circuit configured to input, on the basis of the in positive signal and the negative signal output from the differential amplifier, an offset current signal in accordance with an offset of a level of the in positive signal from a level of the negative signal to the second amplifier.

Optical receiving circuit

There is provided an optical receiving device for deriving a signal using for data identification. The optical receiving device includes a demodulator for demodulating a modulated optical signal to an demodulated optical signal, a convertor for converting the demodulated optical signal to a first and a second electric signals, a generator for generating a complement signal by summing the first electric signal of a normal in phase component and the second electric signal of a reverse in phase component, and a suppressor for suppressing, by the use of the complement signal, a variation of potential which appears in a data signal at a time of phase changing of the modulated optical signal, the data signal being a difference of the normal in phase component and the reverse in phase component.

Optical receiving device, optical receiving circuit, and method for receiving optical signals

A communication terminal apparatus receives a management signal at a bit rate A and a data signal at a bit rate B (B=A&#xd7;M) through the same line. The communication terminal apparatus includes a signal regenerating unit, a management signal converting unit, a timing control unit, and a data signal obtaining unit. The signal regenerating unit regenerates a signal transmitted through the line as a signal of a bit rate C (C=A&#xd7;N). The management signal converting unit converts N bits of the regenerated signal into the management signal of one bit. The timing control unit controls timing for obtaining a data signal based on the management signal. The data signal obtaining unit obtains the data signal according to timing control of the timing control unit.

Communication terminal apparatus, communication apparatus, and signal receiving method

A data receiver circuit includes: a clock/data recovery circuit to recover a clock and data from a received signal; a fixed pattern generation circuit to generate fixed pattern data; a first selection circuit to select and output one of the fixed pattern data generated by the fixed pattern generation circuit and recovered data recovered by the clock/data recovery circuit; a second selection circuit to select and output one of a reference clock and recovered clock recovered by the clock/data recovery circuit; and a switching circuit to make the first selection circuit output the fixed pattern data and to make the second selection circuit output the reference clock, when an input signal is lost or the clock/data recovery circuit is in a loss-of-lock state.

Data receiver circuit

An optical communication apparatus includes a receiver configured to receive an optical signal transmitted from an optical transmitting apparatus; a detector configured to detect a predetermined pattern signal included in the optical signal; a calculator configured to calculate, based on a waveform of the predetermined pattern signal, an amount of dispersion of the predetermined pattern signal; and a compensator configured to compensate for dispersion according to the amount of dispersion.

Optical communication apparatus and optical communication method

In an optical receiver, a light receiving element receives the optical packet signals and converts the optical packet signals to electrical signals. A bias voltage supply section supplies bias voltage to the light receiving element. A monitoring section monitors an input level of each optical packet signal or each electrical signal and transmits a monitored value to the bias voltage supply section. In addition, the bias voltage supply section temporarily increases the bias voltage according to magnitude of the monitored value after an end of receiving of each optical packet signal.

Optical receiver

A light modulation device capable of stabilizing a phase set in phase modulation processing and improving optical communication quality. A phase modulator is provided for each of plural branched input lights and performs phase modulation of the input light. A phase shifter is provided at the upstream or downstream of the phase modulator and shifts a phase of the input light or of the phase-modulated light. A light interference section causes the output lights from the light modulator to interfere with each other to generate a multilevel phase modulated signal and interference light having a phase state different from that of the modulated signal. A monitor receives the interference light and outputs an electric signal according to the intensity. A phase shift controller generates a phase control signal based on the electric signal and applies the signal to the shifter to control the phase shift amount to be set by the shifter.

Light modulation device

In an optical switch controller, in order that residual vibration at movement control of a movable body such as a tilt mirror can be reduced and controlled with high accuracy, a processing unit outputs a driving signal for controlling the angle of the tilt mirror, the driving signal is D/A converted by a D/A converter and then is changed to a high-voltage signal by a high-voltage amplifier to be supplied to the tilt mirror, the electrostatic capacity of the tilt mirror changes corresponding to angle change of the tilt mirror, a mirror-angle detecting unit detects the electrostatic capacity and feeds back it as a correction value to a processing unit, and the processing unit corrects the driving signal using a correction value obtained when the angle of the tilt mirror is actually changed.

Growing community of inventors

Kawasaki, Japan

Satoshi Ide