摘要:
An optical transmitter including a light source for outputting a carrier light, an electro-absorption optical modulator for absorbing the carrier light according to an applied voltage to thereby output an intensity-modulated signal light, a device for applying an offset voltage to the optical modulator so that the applied voltage enters a region where the generation of the carrier light in the light source is stable, and a device for receiving an input signal to superimpose a modulation signal corresponding to the input signal on the offset voltage. This optical transmitter prevents wavelength chirping of the light source due to residual reflection in the optical modulator to thereby allow improvement in waveform.
摘要:
An optical transmitter comprises a first unit for generating an optical signal having a bandwidth given by a main signal, a second unit modulating the optical signal according to a control signal to extend the bandwidth of the optical signal, a third unit extracting backward light including SBS(stimulated Brillouin scattering) light generated in an optical fiber transmission line, and a fourth unit performing feedback control so that the power of the SBS light becomes substantially constant. Through the structure of the optical transmitter good transmission characteristics of a main signal are obtained and the suppression of the SBS is allowed.
摘要:
Disclosed is a laser diode protecting circuit adapted to prevent a laser diode from producing an excessive emission when the laser diode is driven at low temperature, thereby assuring that the laser diode will not be damaged or degraded in terms of its characteristic. When the laser diode is started at low temperature, a laser diode protecting circuit has a power monitor circuit for monitoring backward power of the laser diode and a laser diode current limiting circuit for limiting the laser diode current when the backward power becomes equal to the set power. When the laser diode temperature subsequently rises and the backward power falls below the set power, an automatic current control circuit performs automatic current control in such a manner that the laser diode current attains a set current value. Alternatively, a temperature monitor circuit monitors the temperature of the laser diode and the laser diode current limiting circuit limits the laser diode current when the monitored temperature of the laser diode is less than the set temperature. When the laser diode temperature exceeds the set temperature, the automatic current control circuit performs automatic current control in such a manner that the laser diode attains the set current value.
摘要:
Disclosed is a laser diode protecting circuit adapted to prevent a laser diode from producing an excessive emission when the laser diode is driven at low temperature, thereby assuring that the laser diode will not be damaged or degraded in terms of its characteristic. When the laser diode is started at low temperature, a laser diode protecting circuit has a power monitor circuit for monitoring backward power of the laser diode and a laser diode current limiting circuit for limiting the laser diode current when the backward power becomes equal to the set power. When the laser diode temperature subsequently rises and the backward power falls below the set power, an automatic current control circuit performs automatic current control in such a manner that the laser diode current attains a set current value. Alternatively, a temperature monitor circuit monitors the temperature of the laser diode and the laser diode current limiting circuit limits the laser diode current when the monitored temperature of the laser diode is less than the set temperature. When the laser diode temperature exceeds the set temperature, the automatic current control circuit performs automatic current control in such a manner that the laser diode attains the set current value.
摘要:
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.
摘要:
An optical transmitter includes a laser diode module including a laser diode which outputs a light signal to a transmission line, a driving unit which drives the laser diode in accordance with an input signal indicative of data to be transmitted, and a coupling unit for connecting an output of the driving unit to an input of the laser diode module. The coupling unit allows an alternating current to flow through the laser diode and inhibits the output of the driving unit from being subjected to a direct current from the laser diode module.
摘要:
The optical transmission apparatus for multiple wavelengths according to the present invention comprises; a light source, a temperature control section for controlling the temperature of the light source, a temperature control (ATC) loop for controlling the operation of the temperature control section, and a wavelength control (AFC) loop. The ATC loop detects the temperature of the light source and feedback controls the operation of the temperature control section, so that the optical output wavelengths of the light source fall within a wavelength capture range corresponding to a target wavelength of the AFC loop. The AFC loop has a wavelength detection filter having a periodic transmission wavelength characteristic. After the operation of the ATC loop has stabilized, a wavelength capture operation is commenced, and the operation of the temperature control section is controlled so that the optical output wavelength of the light source is captured at a stable point corresponding to a target wavelength, among a plurality of stable points.
摘要:
An identification level control method and an optical receiver are disclosed to determine an optimal identification level in a simple structure without clock extraction. In the identification level control method, an identification level supplied to a limiter amplifier is changed from a lower bound to an upper bound thereof and is stored together with an output average of the limiter amplifier. Then, a first average and a second average are set based on the output average. A first identification level corresponding to the first average and a second identification level corresponding to the second average are obtained, and an optimal identification level is computed based on the first identification level and the second identification level, and is supplied to the limiter amplifier.
摘要:
There is provided a PLO device which performs high-accuracy, high-quality clock recovery. A shifted data generation part generates shifted data, and a first phase comparison part outputs first difference data. A first filter removes an alternating-current component from the first difference data and outputs a first detection voltage. A delay part delays input data for a time corresponding to half of one time slot with the use of an analog delay element and outputs delayed data. A second phase comparison part compares the phases of the input data and delayed data with each other and outputs second difference data. A second filter removes an alternating-current component from the second difference data and outputs a second detection voltage. An arithmetic section divides the first detection voltage by the second detection voltage to obtain a control voltage. A clock oscillation section outputs recovered clock based on the control voltage.
摘要:
An automatic temperature control circuit of a laser diode solves a problem that a temperature control becomes unstable when switching to heat or cool the laser diode. In the circuit, a peltier element changes the temperature of the laser diode by heating or cooling, a temperature detecting section detects the temperature of the laser diode and outputs the corresponding detected voltage, an error amplifying section outputs an error voltage by comparing the detected outputted voltage with a fixed value, a peltier current control section controls the direction of a driving current flowing to the peltier element in correspondence with an error voltage outputted from the error amplifying section. In addition, there is provided a circuit which feed-backs a voltage corresponding to the driving current flowing to the peltier element to an input side of the error amplifying section and adds it to the detected voltage outputted from the temperature detecting section.