Fujitsu Corporation

Fujitsu Semiconductor Limited

Akihiko Sugata

Tetsuya Kiyonaga

Hisaya Sakamoto

Akimitsu Miyazaki

Shinya Fujioka

Hiroshi Nishimoto

Hiroaki Tomofuji

Kohji Nozoe

Tsuzumi Ninomiya

In a semiconductor device that generates a power supply voltage from an RF carrier signal received by an antenna through the use of a rectification circuit, rectification circuits, each including a plurality of capacitors and a plurality of diodes, are connected in multistage. The rectification circuits includes limiter circuits that are turned on at a voltage larger than an on-voltage of the diodes, clamp cathodes of the diodes at a first voltage. The limiter circuits and the diodes are connected in parallel between the capacitors connected to the antenna connection terminal and a node supplied reference potential VSS of the power supply voltage.

Semiconductor device including a rectification circuit

A receiver apparatus includes a band-pass filter having a variable frequency band coupled to a node for receiving a received signal including a plurality of channels to output at an output node thereof a limited-band signal made by limiting a frequency band of the received signal to a frequency band of a desired channel, a frequency conversion unit coupled to the output node of the band-pass filter to output at an output node thereof an intermediate frequency signal made by converting frequencies of the limited-band signal, and a control unit configured to adjust an intermediate frequency of the intermediate frequency signal by controlling the frequency conversion unit in response to at least one of a signal speed and a channel frequency interval of the received signal.

Receiver apparatus and method of processing received signal which attain optimum SNR

An optical communication system transmits an optical signal from an optical sender to an optical receiver. A superimposed signal corresponding to a transmission speed of the optical signal is superimposed on the optical signal. At the optical receiver which receives the transmission light, the transmission speed is detected based on the superimposed signal included in the received light, and setting of a phase-lock loop circuit for extracting a clock signal is switched, to thereby perform a data decision processing of the received light. Thus, it becomes possible to receive and process optical signals at different transmission speeds by a single optical receiver, even when optical signals at the different transmission speeds are transmitted between the optical sender and the optical receiver.

Optical communication system, optical receiver and wavelength converter

Disclosed is a clock extraction circuit for extracting a clock signal which furnishes timing for discriminating a data signal, from the data signal. The clock extraction circuit has a timing extraction unit for extracting the clock signal from the data signal, and a filter, which is provided in front of the timing extraction unit, having an upper limited frequency sufficiently lower than the bit rate of the data. The data signal is input to the timing extraction unit via the filter.

Clock extraction circuit

A clock signal detection circuit includes a diode to which a clock signal is applied as an input. If a voltage VD IN on the anode side of the diode is greater than a voltage VD OUT on the cathode side, the clock signal is fed into a transmission line and arrives at a reflecting load upon elapse of a prescribed delay time. When the voltage VD IN on the anode side of the diode becomes smaller than the voltage VD OUT on the cathode side, the clock signal is reflected by the reflecting load and returns to the cathode of the diode through the transmission line. This introduction and reflection of the clock signal is repeated at the clock signal period so that the amplitude on the output side of the diode is enlarged, thereby making it possible to obtain, from an averaging circuit, a clock detection voltage substantially equal to the amplitude value of the clock signal.

Clock signal detection circuit

An optical amplifier is disclosed, which comprises an optical amplifying unit for amplifying an optical signal, a light output monitoring unit for monitoring the light output of the optical amplifying unit, a control unit for controlling the optical amplifying unit by comparing the light output of the optical amplifying unit monitored by the light output monitoring unit with a specified reference value so as to cause the light output of the optical amplifying unit to take a predetermined output value and an input light level detecting unit for detecting the input light level of the optical signal. The control unit controls the light output level of the optical amplifying unit by changing the reference value used for comparison according to the input light level detected by the input light level detecting unit. By employing simple means for controlling the gain of the optical amplifying unit according to the input light level of the optical signal to be inputted, proper amplification control is performed without making the optical amplifier complex even when a change occurs in the number of input wavelengths.

Optical amplifier

A drive circuit for an optical modulator having first and second electrodes for receiving a drive voltage. The optical modulator modulates carrier light from a light source according to the drive voltage to output modulated signal light. A terminating resistor for generating the drive voltage is connected between the first and second electrodes. A first end of a transmission line is connected to one of the first and second electrodes. A circuit for generating a drive signal is connected to a second end of the transmission line. A reflection rejecter (e.g., attenuator) for suppressing a reflected wave generating in the transmission line is provided on the transmission line. This drive circuit improves the waveform of the modulated signal light in case that the carrier light has large power.

Drive circuit optical modulator and optical transmitter

A supervisory and control signal transmitting system for use in an optically amplifying repeater system amplifies attenuated light and for transmitting data over a long distance between a transmitting station and a receiving station through a plurality of repeaters. The supervisory and control signal transmitting system comprises a sub signal superimposing portion for superimposing both a sub signal with a carrier frequency modulated by a supervisory and control signal and a modulation factor stabilizing signal with a different frequency thereof on an optical main signal modulated corresponding to transmission data, a transmitter sub signal superimposing portion for monitoring the output of the sub signal superimposing portion and for controlling the sub signal superimposing portion so as to stabilize the modulation factor of the sub signal to be superimposed, a modulating portion for receiving the output of the transmitter sub signal superimposing portion, and a stabilizing signal erasing portion for monitoring the output of the modulating portion, for extracting the frequency component of the modulation factor stabilizing signal, and for driving the modulating portion so as to erase the stabilizing signal from the output of the modulating portion.

Growing community of inventors

Kawasaki, Japan

Akihiko Sugata