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I have a design problem. That's to design a wavelength locking loop for a DWDM optical transmitter. The DFB laser source used in the transmitter has a wavelength temperature coefficient of .106 nm / degree centigrade. The temperature of the laser chip cant be allowed to drift more than 0.1 degree centigrade.
I'm using two feedback loops for achieving wavelength control. One is a thermal feedback loop with a thermistor and thermoelectric cooler which are within the laser chip. Another is with a wavelength sensor which is afabry perot etalon based device. Which has two photo detectors one of which recieves the optical input directly and the other through an etalon. The difference in the photodetector currents gives a measure of the drift in wavelength.
I intend to use PID control for both loops(Thermal as well as wavelength).Could someone suggest some references where i could get some understanding about how to model the plants(Thermal as well as wavelegth sensor) and obtain their transfer functions so that i can tune the PID parameters.
I'm using two feedback loops for achieving wavelength control. One is a thermal feedback loop with a thermistor and thermoelectric cooler which are within the laser chip. Another is with a wavelength sensor which is afabry perot etalon based device. Which has two photo detectors one of which recieves the optical input directly and the other through an etalon. The difference in the photodetector currents gives a measure of the drift in wavelength.
I intend to use PID control for both loops(Thermal as well as wavelength).Could someone suggest some references where i could get some understanding about how to model the plants(Thermal as well as wavelegth sensor) and obtain their transfer functions so that i can tune the PID parameters.