Wavelength locker

1. A method comprising:

reading a temperature of a wavelength filter of a silicon photonics chip using a temperature sensor of the silicon photonics chip; wherein the wavelength filter is a ring-resonator add drop filter; wherein the temperature sensor and a heater are proximate to the wavelength filter on the silicon photonics chip; wherein the heater is enabled to change the temperature of the wavelength filter to change a wavelength of the wavelength filter;

measuring light dropping from the ring resonator add drop filter using a first photodetector optically coupled to the ring resonator add drop filter; wherein the first photodetector is enabled to measure light passing through the ring-resonator add-drop filter;

measuring the light dropping from the ring resonator add drop filter using a second photodetector optically coupled to the ring resonator add drop filter; and

inputting the measured light from the first photodetector into a control system;

inputting the measured light from the second photodetector into the control system; and

tuning a laser using the control system to make the output of measured light of the first photodetector and the second photodetector to be equal.

2. The method of claim 1 wherein the temperature sensor is a diode sensor.

3. The method of claim 1 wherein the temperature of the wavelength filter is used to place a slope of the wavelength filter response at a desired wavelength.

4. The method of claim 1 further comprising locking the temperature of the wavelength filter; and

locking the laser to the wavelength filter.

5. The method of claim 1 wherein tuning of the laser includes locking the laser on a slope of the wavelength filter according to a wavelength of the laser.