Fujitsu Corporation

Takeshi Ihara

Hiroshi Hamano

Takuji Yamamoto

Izumi Amemiya

Yasunari Arai

Yoichi Oikawa

Yoshinori Nishizawa

Hiroki Ooi

George Ishikawa

Hiroo Kitasagami

Katsuya Yamashita

It is aimed at providing an optical receiving apparatus and an optical receiving method, which can assuredly receive and process signal lights having different transmission rates, by a simple and single device. To this end, the signal light received by the present optical receiving apparatus is converted into an electric signal by a light receiving element and thereafter sent to an equalizing amplifier whereby the signal is amplified. The transmission rate of this received signal is detected by a transmission rate detecting part, and a band of the equalizing amplifier is optimally controlled by an equalizing band controlling part, corresponding to the detected transmission rate. In case of adopting a PLL (phase-locked loop) circuit as a clock generating circuit, there is also controlled a band of a loop filter corresponding to the transmission rate detected by the transmission rate detecting part. Thus, there can be obtained an excellent reception characteristics, even when receiving signal lights having different transmission rates.

Optical receiving apparatus and method

A method for extracting a timing signal produces a data signal from a first portion of an optical signal, extracts a timing signal from a second portion of the optical signal and adds dispersion compensation to at least one of the first and second portions of the optical signal to thereby control the amount of total dispersion in the second portion of the optical signal to be substantially different from the amount of total dispersion in the first portion of the optical signal. The timing signal extracting device uses a signal reproduction circuit to produce the data signal, a signal extraction circuit to extract the timing signal and a chromatic dispersion control apparatus to add dispersion compensation. The optical signal may be modulated by a data signal having a bit rate of X bits/second and the extracted timing signal may have a frequency of X hertz. The signal extraction circuit may be used with a phase locked loop. Here, a voltage-controlled oscillator generates a clock signal, a phase comparison circuit compares the phase of the clock signal with the phase of the extracted timing signal and a control circuit controls the phase comparison circuit, to generate a control voltage for the voltage-controlled oscillator on the basis of the comparison. The chromatic dispersion control apparatus may use a variable dispersion compensator together with an optical detector which detects the intensity of a specific frequency component of the optical signal to minimize the intensity of the specific frequency component.

Method and device for extracting a timing signal

Waveform degradation due to chromatic dispersion of an optical fiber is detected and compensated for. A waveform detector detects a change in waveform, based on the ratio between the powers of a plurality of frequency components or on peak or duty detection, and the frequency bandwidth of an equalizing amplifier or the chromatic dispersion of an optical fiber is controlled based on the result of the detection.

Detection of, and compensation for, waveform change due to chromatic

An equalizing filter with an optimized frequency response and improved reliability and quality, for equalizing a reception signal so as to regain its original waveform. The equalizing filter comprises a low-pass filter and a high-frequency booster circuit. With its limited passband, the low-pass filter rejects the noise components contained in the signal being processed. The high-frequency booster circuit has such a frequency response that exhibits a stepwise gain increase at high frequencies. Those two elements, composed of reliable passive components, are coupled in series to provide a combined frequency response that is optimized for the design of highly sensitive optical receivers. As integral part of the high-frequency booster circuit, the equalizing filter employs an inductor made of a bonding wire. To obtain a predetermined inductance with high accuracy, the bonding wire is divided into a plurality of sections, which are used to make a daisy chain connection that bridges between a plurality of lands disposed on the substrate.

Equalizing filter and control method for signal equalization

A high speed electronic circuit has a cascode circuit configuration and is provided with a bias current source (CS.sub.0) between an emitter and a base of a load transistor (Q) in the cascode circuit configuration for compensating a base-emitter voltage (V.sub.BE) of the transistor to eliminate an adverse effect of charging and discharging at a stray capacitor (C) which can be connected between the base and the emitter of the transistor. The high speed electronic circuit can be applied to an; circuit, a level shift circuit, a level shift discrimination circuit, a signal distribution circuit, a signal synthesization circuit and a frequency band control circuit.

High-speed electronic circuit having a cascode configuration

A filter circuit and a filter integrated circuit capable of being used in a high frequency band includes a first resistor R.sub.1 connected between an input signal source and an emitter of a common-base transistor TR.sub.1, a first capacitor C.sub.1 connected between said input signal source and a reference voltage point, a second capacitor C.sub.2 connected between said input signal source and a collector of the common-base transistor TR.sub.1, and a second resistor R.sub.2 connected between the collector of the common-base transistor and the reference voltage point. Thus, a low-pass filter which operates in a high frequency band and suppresses the influence of characteristic parameters over the filter characteristic can be constructed.

Filter circuit and filter integrated circuit

A filter circuit and a filter integrated circuit capable of being used in a high frequency band comprises a first resistor R.sub.1 connected between an input signal source and an emitter of a common-base transistor TR.sub.1, a first capacitor C.sub.1 connected between said input signal source and a reference voltage point, a second capacitor C.sub.2 connected between said input signal source and a collector of the common-base transistor TR.sub.1, and a second resistor R.sub.2 connected between the collector of the common-base transistor and the reference voltage point. Thus, a low-pass filter which operates in a high frequency band and suppresses the influence of characteristic parameters over the filter characteristic can be constructed.

An electronic circuit package which includes first and second conductive metal members and a circuit board held between the first and second metal members and having a cutout in which an electronic circuit part is accommodated and a process of producing such electronic circuit package are disclosed. With the electronic circuit package, deterioration of a high speed characteristic of an electronic circuit part accommodated in the package is minimized, and accordingly, when the electronic circuit package is applied to an IC for very high speed optical communications for use with an optical repeater or the like, a very high speed system can be realized. By assembling the components in accordance with a predetermined order, facility in process of production and improvement in reliability of products are attained.

Method of producing an electronic circuit package

Electronic circuit package

Disclosed is an equalizing and amplifying circuit in an optical signal receiving apparatus comprising a preamplifier circuit having an input terminal connected to the output of a light receiving element. The preamplifier circuit amplifies the electrical signal from the light receiving element and outputs an amplified signal. An automatic gain control circuit is connected to the output of the preamplifier circuit. The preamplifier circuit comprises a transistor having a common-base, a current source connected to the emitter of the transistor for supplying a bias current to the transistor, and a load resistor connected to the collector of the transistor. The emitter of the transistor is connected to the input terminal, and the collector of the transistor is connected to the output terminal. A negative influence caused by mounting the circuit on a package is avoided and the circuit operates stably in a high frequency range.

Equalizing and amplifying circuit in an optical signal receiving

A data delay circuit includes a first transistor, and a second transistor having a base, an emitter and a collector. Input data is applied to the bases of the first and second transistors. A constant-current source is coupled between the emitters of the first and second transistors and a negative power source. A capacitor is connected between the collector of the first transistor and the collector of the second transistor. The data delay circuit further includes a third transistor and a fourth transistor. The emitters of the third and fourth transistors are connected to the collectors of the first and second transistors, respectively. The bases of the third and fourth transistors are provided with control data having a polarity opposite to that of the input data and having an adjusted amplitude level corresponding to a desired delay time to be given the input data. First and second load resistors are respectively coupled to the collectors of the third and fourth transistors through a positive power source. Delayed input data is drawn from the collectors of the third and fourth transistors.

Growing community of inventors

Kawasaki, Japan

Takeshi Ihara