Wavelength stabilization and locking for colorless dense wavelength division multiplexing transmitters

A method comprising:

• correlating a detected photocurrent of a backward light from a laser with a wavelength shift between a wavelength of an output light and a filter transmission peak;
• and
• thermally tuning the wavelength of the laser to substantially maximize the detected photocurrent and substantially minimize the wavelength shift,
• wherein a detected power of the light P is inversely proportional to a threshold current Ith of the laser according to P(λ)=η(Ib−Ith(λ)), where λ is the wavelength of the laser, Ib is a bias current of the laser, and λis a quantum efficiency of the laser.

A system comprising:

• a laser configured to generate a light having a wavelength and a polarization;
• an optical polarization rotator configured to rotate the polarization of the light;
• a photodetector configured to produce an electrical indication of the wavelength;
• at least one processor coupled to the photodetector and configured to:
• receive the electrical indication;
• determine a difference between the wavelength and a filter transmission peak;
• and
• adjust the laser to vary the wavelength, thereby reducing or substantially eliminating the difference and aligning the wavelength with the filter transmission peak;
• an arrayed waveguide grating (AWG) optically coupled to the optical polarization rotator such that the optical polarization rotator is positioned between the laser and the AWG;
• a reflector coupled to the AWG such that the AWG is positioned between the optical polarization rotator and the reflector;
• a second optical polarization rotator coupled to the reflector such that the second optical polarization rotator is positioned between the reflector and the AWG and there are no optical components other than an optional optical fiber between the reflector and the second optical polarization rotator;
• and
• a splitter coupled to the AWG such that the AWG is positioned between the optical polarization rotator and the splitter;
• wherein there are no optical components other than either an optional optical fiber or an optional lens between the laser and the optical polarization rotator,
• wherein the reflector is coupled to the splitter such that the splitter is positioned between the reflector and the AWG,
• wherein the splitter is configured to:
• split the light into a first part and a second part;
• forward the first part to an optical network;
• and
• forward the second part to the reflector, and
• wherein the reflector is configured to reflect substantially all of the second part back to the splitter.

A method comprising:

• generating, via a laser, a light having a polarization and a wavelength;
• rotating the polarization of the light a first time;
• detecting the wavelength of the light;
• determining a difference between the wavelength and a filter transmission peak;
• adjusting the laser to vary the wavelength, thereby reducing or substantially eliminating the difference and aligning the wavelength with the filter transmission peak;
• multiplexing the rotated light with a plurality of other lights prior to reflecting at least part of the rotated light, wherein the other lights have other wavelengths that are different from the wavelength;
• rotating the rotated light a second time prior to the reflecting;
• rotating the reflected light a third time after the reflecting;
• rotating the reflected light a fourth time prior to the reflected light returning to the laser, such that the light is rotated four times between being generated by the laser and returning to the laser;
• and
• wavelength demultiplexing the reflected light from the other lights prior to rotating the reflected light the fourth time.