Abstract: A system is provided for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light; a laser cavity includes an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium; a position sensor that senses position of the element; position signal circuitry that produces a position signal indicative of position of the element sensed by the position sensor; a storage medium storing at least one position signal corresponding to a respective predetermined position of the element; comparison circuitry for comparing the produced position signal with the at least one stored position signal and for producing a comparison result indicative of whether the element has reached to the predetermined position; marker signal circuitry providing an external wavelength marker signal when the comparison result indicates that the element