Fujitsu Corporation

Kakuji Inoue

Kazuyuki Mori

Hiroyuki Nobuhara

Setsuo Misaizu

Yoshihiro Saito

Norio Nagase

Yo Akimoto

Kenichi Kobayashi

Makoto Miyoshi

Yasunori Nagakubo

Hiroo Kitasagami

Yasuhiro Tanaka

Masahiko Yamashita

Toru Yamazaki

Hirokazu Osada

Tatsuya Nishimura

Kazuhisa Kogure

Shinichiro Sano

Takayoshi Ikegami

Shihori Imai, Legal Representative

An optical transmitter comprises an amplitude modulation unit performing amplitude modulation of only a one-side amplitude of a main signal with a low-frequency signal having a predetermined frequency. An optical modulator receives an input signal generated after the one-side amplitude modulation, and modulates an incoming light in response to the received signal in accordance with a predetermined modulation-characteristic curve to output an optical output signal. An operating point control unit applies a predetermined bias voltage to the optical modulator to control a level of the input signal substantially applied to the modulation-characteristic curve so that the one-side amplitude of the main signal is applied to a minimum portion of the modulation-characteristic curve of the optical modulator.

Optical transmitter and its control method

A transisterized circuit may be driven with a low voltage without saturation of a direct current operating voltage point. The transisterized circuit includes a first transisterized circuit formed by a cascade connection of a first differential transisterized circuit and a first emitter follower circuit, a second transisterized circuit formed by a cascade connection of a second emitter follower circuit and a second differential transistor circuit, and an inversion circuit connected between said first transisterized circuit and said second transistor circuit.

Operating voltage point compensation circuit for a transistorized circuit

A burst optical signal receiver receives optical signals produced in a burst form from a predetermined subscribers. This burst optical signal receiver comprises an identifying circuit for comparing the input level of an input optical signal with a predetermined threshold value to identify the input level; a peak detector for detecting and holding the peak value of the input optical signal; a DC feedback circuit for acquiring the DC level of an output of the identifying circuit; and a circuit for producing the predetermined threshold value from the DC level from the DC feedback circuit and the peak value held in the peak detector and supplying the predetermined threshold value to the identifying circuit. The peak detector has a plurality of peak detection sections having different gains and operational dynamic ranges and causes those peak detection sections to operate in accordance with the input level of the input optical signal.

Burst optical signal receiver

In an equalizing amplifier that equalizes an electric signal obtained from a light signal received via an optical transmission path, an AGC circuit generates first and second signals from the electric signal by referring to a threshold voltage. The first and second signals are complementary signals. An offset compensation circuit generates a first difference signal based on a difference between the first and second signals, compares the first difference signal with a first reference signal, and outputs, as the threshold voltage, a resultant error signal to the AGC circuit. The threshold voltage is varied so that it is located in the center of an amplitude of the electric signal whereby an offset of the AGC circuit can be compensated for.

Equalizing amplifier, receiver using the same and preamplifier

Growing community of inventors

Sapporo, Japan

Kakuji Inoue