Abstract: An optical transmitter comprises a modulator for generating a modulated current in accordance with a modulation control signal, a light emitting element driven by the modulated current from the modulator to emit light in accordance with the modulated current, a first current source for supplying the modulator with a driving current, a first temperature detector for detecting an operating temperature of the modulator to output a signal indicative of a detected operating temperature of the modulator, and an amplifier for receiving a data signal to supply the modulator with the modulation control signal based on the data signal. The amplifier has a first modulation control signal controller for controlling a changing amount per unit time of the modulation control signal at rising and falling times in accordance with an output signal of the temperature detector.

Abstract: An optical transmitter receiver module and an apparatus incorporating the same module are provided, which realizes the reduction of power consumption and the enlargement of the operating temperature range.

Abstract: In the initial state, any wavelength variation of the output signal light with a change of the current injected into the laser is monitored with a wavelength meter, the quantity of wavelength variation is fed back to the wavelength compensation circuit, a compensation voltage for maintaining the wavelength in the initial stage is figured out, and that voltage is recorded into a memory element or the like. A configuration to add this compensation voltage to a comparator makes it possible to compensate for fluctuations of the characteristics of the optical splitter, wavelength filter and light receiving elements and thereby to obtain a stable optical wavelength. By constantly monitoring the injected current applied to the laser when the optical transmitter is in operation and giving a compensation voltage matching the current variation to the comparator, stabilization of the optical wavelength can be realized.

Abstract: An optical transmitter comprises a modulator for generating a modulated current in accordance with a modulation control signal, a light emitting element driven by the modulated current from the modulator to emit light in accordance with the modulated current, a first current source for supplying the modulator with a driving current, a first temperature detector for detecting an operating temperature of the modulator to output a signal indicative of a detected operating temperature of the modulator, and an amplifier for receiving a data signal to supply the modulator with the modulation control signal based on the data signal. The amplifier has a first modulation control signal controller for controlling a changing amount per unit time of the modulation control signal at rising and falling times in accordance with an output signal of the temperature detector.

Abstract: An optical transmitter for use in an optical transmitting system based on PDS (Passive Double Star) technology, does not erroneously output an optical signal when the optical transmitter is powered on/off. The optical transmitter has a current source 1 for outputting a drive current having a magnitude corresponding to an input control signal, a Laser diode (LD) for generating an optical output signal based on the received drive current, a modulator 9 for controlling the supply and cutoff of the drive current to the Laser diode (LD), a source voltage detector 3 for monitoring a source voltage to detect whether the source voltage is lower than a predetermined voltage, and a switch circuit 4 for outputting a control signal to the current source 1 to stop the supply of the drive current when the source voltage is determined to be lower than the predetermined voltage.

Abstract: An optical transmitter for use in an optical transmitting system based on PDS (Passive Double Star) technology, does not erroneously output an optical signal when the optical transmitter is powered on/off. The optical transmitter has a current source 1 for outputting a drive current having a magnitude corresponding to an input control signal, a Laser diode (LD) for generating an optical output signal based on the received drive current, a modulator 9 for controlling the supply and cutoff of the drive current to the Laser diode (LD), a source voltage detector 3 for monitoring a source voltage to detect whether the source voltage is lower than a predetermined voltage, and a switch circuit 4 for outputting a control signal to the current source 1 to stop the supply of the drive current when the source voltage is determined to be lower than the predetermined voltage.

Abstract: An optical transmitter for use in an optical transmitting system based on PDS (Passive Double Star) technology, does not erroneously output an optical signal when the optical transmitter is powered on/off. The optical transmitter has a current source 1 for outputting a drive current having a magnitude corresponding to an input control signal, a Laser diode (LD) for generating an optical output signal based on the received drive current, a modulator 9 for controlling the supply and cutoff of the drive current to the Laser diode (LD), a source voltage detector 3 for monitoring a source voltage to detect whether the source voltage is lower than a predetermined voltage, and a switch circuit 4 for outputting a control signal to the current source 1 to stop the supply of the drive current when the source voltage is determined to be lower than the predetermined voltage.

Abstract: An optical transmission system includes a current source for outputting a drive current, a semiconductor laser for converting the drive current into a stimulated emission light and producing the same, a drive circuit for converting a transmission data signal into a modulation control signal and outputting the same, an optical modulator for receiving the stimulated emission light and a shading control signal for interrupting light emission and producing and outputting transmission signal light by changing an amount of transmission of the stimulated emission light according to the shading control signal, and a shading element for receiving the transmission signal light and a shading control signal for interrupting light emission and interrupting the transmission of the transmission signal light according to the shading control signal whereby an optical signal having wrong optical wavelength is rapidly prevented.

Abstract: An optical transmitter comprises a modulator for generating a modulated current in accordance with a modulation control signal, a light emitting element driven by the modulated current from the modulator to emit light in accordance with the modulated current, a first current source for supplying the modulator with a driving current, a first temperature detector for detecting an operating temperature of the modulator to output a signal indicative of a detected operating temperature of the modulator, and an amplifier for receiving a data signal to supply the modulator with the modulation control signal based on the data signal. The amplifier has a first modulation control signal controller for controlling a changing amount per unit time of the modulation control signal at rising and falling times in accordance with an output signal of the temperature detector.

Abstract: A safety device for an engine cooling system having a heater core circuit for circulating the engine cooling water through the heater core of an automotive air conditioning system, and a radiator circuit for circulating the engine cooling water through a radiator. The safety device comprises a safety valve provided in the heater core circuit and capable of discharging the engine cooling water outside the vehicle when the temperature of the engine cooling water exceeds a predetermined temperature and/or when the pressure of the engine cooling water exceeds a predetermined pressure.