Other

Hitachi, Ltd.

Opnext Japan, Inc.

Akihiro Hayami

Yasuhiro Yamada

Tadashi Hatano

Tomonao Kikuchi

Naohiko Baba

Takayuki Nakao

Toshiaki Murai

Tomoaki Shimotsu

Hidehiro Ikeuchi

Tohru Oyama

Tadaaki Fujii

Masayuki Miyoshi

Norio Chujo

Mitsuo Akashi

Hideyuki Serizawa

Hiroki Irie

A temperature compensating circuit includes a first circuit network between an inverting input terminal of an operational amplifier and an output terminal of the operational amplifier , and a second circuit network between the inverting input terminal of the operational amplifier and a reference potential. At least one of the first circuit network and the second circuit network is made of an arrangement containing a plurality of series-connected thermistor/resistor pairs in which the thermistors are connected parallel to the resistors, and the temperature compensating circuit compensates a temperature-dependent signal which is inputted into a positive phase input terminal of the operational amplifier , and outputs the temperature-compensated signal.

Temperature compensating circuit, temperature compensating logarithm conversion circuit and light receiver

Two sets of a high speed differential amplifier and a low speed differential amplifier are prepared, and frequency response speeds of these high speed/low speed differential amplifiers are different from each other. Both an oscillating frequency and a frequency modulation sensitivity of a ring oscillator type voltage-controlled oscillator circuit can be separately set by adding two outputs of these differential amplifiers to each other and by varying the selection ratio of these high speed/low speed differential amplifiers in a linear manner. Thus, the setting ranges for the oscillating frequency and the frequency modulation sensitivity are enlarged. At this time, since a summation of currents flowing through the high speed/low speed differential amplifiers is continuously made constant, the oscillating frequency depending characteristic of the output amplitude of the VCO circuit can be canceled. Furthermore, since control signals are supplied in a differential structure, increasing of jitter components caused by the common mode noise can be suppressed.

Optical receiver module optical transmitter module phase-locked loop circuit voltage-controlled oscillator and frequency response controllable amplifier

An optical transmitter includes a plurality of optical wavelength stability control apparatuses, each of which is capable of compensating for a wavelength drift by varying a laser diode drive current. Each of the optical wavelength stability control apparatuses detects a laser diode drive current, which is controlled by an auto power control circuit, by using a laser diode drive current detector. The laser diode drive current is normalized by a laser diode drive current increase/decrease normalization unit. A laser diode temperature control target value is generated at a compensated reference voltage generator, in response to the normalized laser diode drive current, to control a current value applied to a thermoelectric cooler so that an output value of a temperature monitor circuit approaches a predetermined laser diode temperature control target value.

Optical wavelength stability control apparatus, optical transmitter and multiple wavelength transmitter

Growing community of inventors

Yokohama, Japan

Akihiro Hayami