Nec Corporation

Nippon Electric Co., Ltd.

Isamu Takano

Kazuhisa Kaede

Norihisa Ohta

In order to provide an optical transmitter applicable for a transmission speed range higher than 1 Gb/s without transmission quality degradation, the embodiment of the invention comprises a flipflop having a set terminal supplied with a transmission signal and a variable delay circuit for delaying an inverse output of the flipflop to be supplied to a reset terminal of the flipflop, for equalizing pulse width of the laser light with that of the transmission signal.

Optical transmitter

The invention provides a very high speed optical transmission apparatus which is tough against a variation in mark rate using an equalizing amplification circuit of a narrow-band frequency characteristic. The optical transmission apparatus includes an equalizing amplification circuit including a photoelectric conversion circuit for receiving a non-return-to-zero code as a reception signal, a peak value detection circuit, a dc amplifier, a timing extraction circuit, a dc regeneration circuit and an identification circuit. The equalizing amplification circuit includes a differentiating circuit for producing a differentiation equalization waveform of a reception signal of a non-return-to-zero code. The dc regeneration circuit includes a logic circuit for outputting logically positive and negative signals of an output signal of the equalizing amplification circuit, and a set-reset flip-flop circuit for receiving the logically positive signal of the output of the logic circuit as a set signal and receiving the logically negative signal of the output of the logic circuit as a reset signal. A full-wave rectification circuit is provided at an input terminal of the timing extraction circuit.

Optical transmission method and optical transmission apparatus

In a prescaler IC test method for carrying out a characterization test to decide whether or not a prescaler IC is normal by the use of an IC tester for carrying out a predetermined decision operation and a probe card for mounting the prescaler IC kept on a wafer, the prescaler IC carries out a frequency dividing operation on reception of a frequency signal to produce a frequency divided signal. The characterization test comprises the steps of generating the frequency signal to supply the frequency signal to the prescaler IC on reception of a direct current control signal, converting the frequency divided signal into a converted signal having a predetermined signal width and a signal level, detecting a first mean value of the signal level, and supplying the first mean value to the IC tester in the form of a direct current signal. The IC tester is supplied with the first mean value and carries out the predetermined decision operation by the use of the first mean value.

Prescaler IC test method capable of executing alternate current test by

A probe card includes an oscillator generating an AC signal, an averaged value detecting circuit receiving a signal outputted from a prescaler IC, for generating an averaged DC signal, and a plurality of switches for changing a flow of a signal among the IC tester, the prescaler IC, the oscillator and the averaged value detecting circuit. The switches is so controlled that the AC signal is supplied to the prescaler IC, and the signal outputted from the prescaler IC is supplied to the averaged value detecting circuit and converted to the averaged DC signal, whereby a non-defective/defective of the AC function of the prescaler IC is discriminated on the basis of the obtained averaged DC signal. The switches are also so controlled that a DC test signal is supplied from the IC tester to the prescaler IC and a DC output signal outputted from the prescaler IC is supplied to the IC tester. Thus, both an AC function test and a DC function test can be carried out on the prescaler IC in the form of a wafer by transferring only DC signals between the IC tester and the probe card.

Prescaler IC testing method and test probe card

An optical transmission system that can perform not only amplification of optical signal level but also dispersion pre-equalization, as the signals are optical. In this invention, optical power level of an optical signal propagating through the dispersion medium is amplified in the optical amplifier. The signal becomes the optical signal a. A phase modulator driving circuit outputs a signal corresponding to the envelope signal of the optical signal a. An optical phase modulator phase-modulates the input optical signal a, outputs an optical signal d for which signal optimum dispersion pre-equalization is performed.

Optical trunk transmission system and an optical repeater circuit

A high frequency amplifier has a distributed amplifier having a sufficiently wide band and formed on a microwave integrated circuit, and at least one bandpass filter directly connected to the distributed amplifier and formed of a microstrip line having a desired frequency band having a desired center frequency.

High frequency amplifier

The object of this invention is to offer an optical transmission system that can perform not only amplification of optical signal level but also dispersion pre-equalization, as the signals are optical. In this invention, optical power level of an optical signal propagating through the dispersion medium 101a is amplified in the optical amplifier 102, the signal becomes the optical signal a. The phase modulator driving circuit 104 outputs a signal corresponding to the envelope signal of the optical signal a. The optical phase modulator 103 charged the signal phase-modulates the input optical signal a, outputs the optical signal d which is performed dispersion pre-equalization to dispersion medium 101b.

An optical regenerative-repeater system according to the present invention includes an optical branch device for branching an input optical signal, a photodiode for converting an optical signal to an electric signal, a timing circuit for generating timing signal, and an optical latch circuit for latching an optical signal. A branched optical signal supplied from the optical branch device is converted to an electric signal by the photodiode. The timing circuit supplies a timing signal to the optical latch circuit in accordance with the electric signal supplied from the photodiode.

Optical regenerative-repeater system

A method and circuit for extracting a timing clock in a Pulse Code Modulation (PCM) system capable of transmitting data at a rate which is on the order of a gigabit per second. A first clock signal is produced by extracting a fundamental frequency component from the received signal. A frequency-divided clock signal is produced by dividing the first clock signal by a predetermined division ratio. A second clock signal is produced by extracting a frequency component of the frequency-divided clock signal. The extracted clock signal is generated by multiplying the second clock signal by a ratio which corresponds to the division ratio.

Timing extracting method suitable for a high bit-rate transmission

A negative feedback amplifier has an amplifying section including a first GaAs FET with its source, gate and drain electrodes. A second GaAs FET has its drain electrode connected to the source electrode of the first GaAs FET. An input terminal is connected to the gate electrode of either the first or the second GaAs FET. A feedback circuit feeds back a part of the output given from the drain electrode of the other GaAs FET's to the gate electrode of the same GaAs FET.

Growing community of inventors

Tokyo, Japan

Isamu Takano