Abstract: A method and system for controlling the wavelength of light emitted by a tunable laser. The system includes a wavelength tuner that provides information of a desired wavelength; a coupler for tapping a portion of the light from the tunable laser; and an apparatus for measuring the actual wavelength of the light. The apparatus takes the portion of the light as an input signal and splits the input signal into two beams that are directed through two paths of different optical lengths. Then, the two beams are interfered with each other in order to form a fringe pattern at an observation plane, where the fringe pattern is detected and analyzed to determine the wavelength of the light. A processor compares the difference between the desired and determined wavelengths, and sends a tuning signal to the tunable laser forming a feedback control of the tunable laser.

Abstract: A method and apparatus for measuring the wavelength of an input light beam whereby the input light beam is split into two light beams which are directed through two paths of different optical length. The light beams are interfered with each other in order to form a fringe pattern at an observation plane, which fringe pattern is detected and analyzed to thereby determine the wavelength of the input light beam.