The Research And Development Of The Control System On Optical Fiber Output Stable Laser Light

Optical communication is a way which is based on the light wave.With the rapiddevelopment of optical fiber communication technology，fiber optic test equipment is alsosimultaneously in progress. In the technology of the fiber communication technology, themeasurement of the optical fiber attenuation, the connector loss and the sensitivitymeasurement of a light closing end machine, the light source is indispensable. Stable lightsource in the fiber measurement is like an oscillator in the electronic circuit, the optical signalmust be a high accuracy one and the optical power must be stable. Therefore, the study of thestable light source control system is necessary. We adopt semiconductor laser as the lightsource. It is a very sensitive device, current and temperature fluctuations can also causechanges of the optical power, affecting the accuracy and stability of the output. It is necessaryto design a control system to monitor the light emitting condition of the semiconductor laserto maintain the semiconductor stability of the laser power output.In the research process of the stable light source system, detailed described powercontrol and temperature control circuit including driving constant current source circuit、protection circuit、current and voltage control circuit、optical power acquisition circuit andtemperature acquisition circuit. Through monitoring the optical intensity of the semiconductorlaser, converting the optical signal into electrical signal and sending it into the microcomputer,then feedback to the controlled constant current source, and by changing the current toachieve the stability of the optical power. The automatic temperature control circuit uses athermistor to acquire the temperature of the semiconductor laser and is converted into anelectrical signal and then come into the microcontroller. PWM is adopted to drive thethermoelectric cooler to regulate the temperature of a semiconductor laser.On the software design, mainly includes the initialization procedures, current and voltagemonitoring program, PID algorithm program, optical power sampling and temperatureacquisition program etc, and the arithmetic average filtering method is adopted to process thedata. In the control process of the semiconductor, the current change quickly and isproportional to the power at the same temperature, so the optical power feedback control isrealized by using the linear compensation method. But temperature changes slowly and there is a lag, so PID control algorithm is adopted and we use C language algorithms to program.In this paper, the stability experiment is done to test the stability of the light source, theexperimental result shows that the stability of the designed light source can meet therequirement of metrological verification and achieved the desired effect.