Fujitsu Corporation

Fujitsu Optical Components Limited

Tetsuji Yamabana

Satoshi Ide

Kazuyuki Mori

Yukito Tsunoda

Yuji Tochio

Kouichi Kanda

Ichiro Watanabe

Yuji Ishii

Mariko Sugawara

Tsuyoshi Morishita

In an optical transmitter having an electro-optic modulator with first child MZI and a second child MZI nested to form a parent MZI, and a processor that controls the bias voltages of electro-optic modulator. In the first section of a control loop, the processor simultaneously superimposes different dither signals onto the first bias voltage of the first child MZI and the second bias voltage of the second child MZI, and extracts the first phase error information for the first child MZI and the first-round third phase error for the parent MZI from a first monitoring result. In the second section of the control loop, the processor simultaneously superimposes different dither signals onto the first and second bias voltages, and extracts the second phase error information for the second child MZI and the second-round third phase error for the parent MZI from a second monitoring result.

Optical transmitter, optical transceiver, and method of controlling bias voltage of electro-optic modulator

Controller and control method are provided. In particular, a controller is disclosed as being configured to hold intensities of a monitor signal, which changes according to an output from a region in a device, before and after altering a state of a portion in the region and control the state of the portion based on a difference between the held intensities.

Controller and control 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

There is provided a parallel-serial converter including a selector to convert parallel data to serial data, a flip-flop to which the serial data are input so as to latch the serial data, a generator to generate replica data simulating the serial data, a detector to detect a first switching point of the replica data and a second switching point subsequent to the first switching point, and a controller to control relative timings of timing converted to the serial data in the selector and timing when the serial data is latched in the flip-flop, based on the first switching point and the second switching point.

Parallel-serial converter

In a PLL circuit, a threshold discriminator generates a control signal indicating a relative level of a control voltage. A controller outputs a controlling value based on the control signal. If the control signal indicates a high level when the controlling value specifies a control voltage-to-oscillation frequency correspondence relation whose upper and lower limits of oscillation frequency are highest, and if the control signal indicates a low level when the controlling value specifies a correspondence relation whose upper and lower limits of oscillation frequency are lowest, the controller outputs a predetermined controlling value. An oscillator has the correspondence relations set therein such that the correspondence relations have respective different upper and lower limits of oscillation frequency and are correlated with the respective controlling values. The oscillator outputs a signal with the oscillation frequency corresponding to the control voltage and associated with the correspondence relation specified by the controlling value.

PLL circuit and voltage-controlled oscillator

On an optical access network, transmission at different bit rates is realized without modifying subscriber units. A low-speed signal generating part generates a low-speed signal having a low bit rate. A high-speed signal generating part generates a high-speed signal having a high bit rate. A recovery signal generating part generates a recovery signal. A multiplex part generates and sends a multiplexed signal obtained by multiplexing the low-speed signal, the high-speed signal, and the recovery signal. A reception processing part performs processing for receiving the multiplexed signal by extracting clocks from the low-bit-rate signal. When the reception processing part enters a free running state in response to receiving the high-speed signal, the recovery signal generating part generates the recovery signal at a low bit rate in order to recover clock synchronization from the free running state.

Transmission system and transmission apparatus

A signal detecting apparatus detects a signal received based on a current received and includes a detecting unit that detects, in the current received, a peak equal to or higher than a threshold and a time counting unit that counts a given period of time from a point in time of detection of the peak by the detecting unit. The signal detecting apparatus further includes a determining unit that determines whether the detecting unit has detected the peak again within the given period of time counted by the time counting unit. An output unit of the signal detecting apparatus outputs information indicating detection of the signal received when the determining unit determines that the peak has been detected again.

Signal detecting apparatus, signal receiving apparatus, and signal detecting method

An optical receiver includes: a converting unit that converts an optical signal into an electrical signal; an amplifying unit that amplifies the electrical signal; a regenerating unit that regenerates the amplified electrical signal; a correcting unit that performs correction of an error included in the regenerated electrical signal; a monitoring unit that performs monitoring of an optical current flowing through the converting unit; and a control unit that calculates a decision threshold based on a result of the correction and a result of the monitoring.

Optical receiver for regeneration of optical signal

In an optical telecommunication system in which an intensity of an arriving optical signal is different for each packet, detected is an optical intensity for each packet with little error. For this purpose, contrived is to detect an average optical intensity across header parts for each packet by focusing on the fact that the header part comprising the preamble and delimiter of a packet is in a bit pattern which includes approximately the same numbers of '0' and '1'.

Optical power monitor for PON telecommunication

An object of the invention is to provide a control apparatus and a control method having a simple constitution, which can stably perform switching of optical path in an optical signal exchanger, while suppressing an influence on a control due to the mechanical resonance of tilt mirrors. To this end, the control apparatus of the optical signal exchanger is constituted such that in an optical signal exchanger of three-dimensional type using one set of MEMS mirror arrays, each having a plurality of tilt mirrors arranged on a plane, each tilt mirror having a reflecting surface an angle of which is controllable, when the angle of the MEMS mirror on the optical path is feedback controlled by detecting power of an optical signal output from a specific position, a resonance component removing section that removes a resonance frequency component included in a control signal is shared corresponding to a pair of driving electrodes arranged in a coaxial direction of the MEMS mirror. As a result, the influence on the feedback control by a resonance action of the MEMS mirror can be reduced, while suppressing an increase in circuit size.

Control apparatus and control method of optical signal exchanger

The apparatus controls a tilt angle of a tilt mirror in high speed with high stability, realizing non-linearity compensation. The apparatus includes: a control signal producing unit, which produces a control signal, for feed-forward controlling of the mirror into a target tilt angle, based on a parameter that determines the target tilt angle; a digital filter for removing a resonance frequency component, which is caused by an angle response of the tilt mirror, in the control signal, which is produced by the control signal producing unit; and a square root calculating unit for performing digital square-root calculation so that non-linearity of the control signal, from which the resonance frequency component has been removed, is compensated for.

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Kawasaki, Japan

Tetsuji Yamabana