Abstract: A tunable laser includes an optical cavity comprising a first and second mirror. A gain medium is positioned in the optical cavity that generates stimulated emission in the optical cavity when biased. A thermally tunable optical filter is positioned in the optical cavity that is heated to a temperature that selects a desired optical mode of the optical cavity. A thermally tunable optical phase retarder is positioned in the optical cavity that is heated to a temperature which changes an optical path length in the optical cavity by an amount corresponding to a resonant frequency of the tunable optical filter so that a phase-matching condition of the optical cavity is shifted to the desired optical mode of the optical cavity selected by the thermally tunable optical filter.

Abstract: An optical signal-to-noise ratio monitor includes a demodulator comprising an input that receives at least a portion of a phase modulated optical signal. The monitor also includes a delay interferometer with a periodic phase control that sweeps a differential delay of one arm of the interferometer through a plurality of differential optical phase shifts. The demodulator converts phase modulated optical signals to intensity modulated optical signals. A tunable optical filter continuously scans a transmission wavelength over a desired wavelength range in a time that allows more than one wavelength to be transmitted through an output of the tunable filter for each of the plurality of differential optical phase shifts. An optical detector detects the filtered optical signal and generates a corresponding electrical demodulation signal at an output. A processor determines an optical signal-to-noise ratio for the more than one wavelength of the optical signal.