Abstract: A method and apparatus are provided for detecting a frequency of an optical signal within a communications channel having a plurality of optical carriers separated by a predetermined frequency spacing. The method includes the steps of locking an optical carrier frequency to an axial mode of an optical resonator of known free spectral range; providing an additional optical resonator as a reference having a known free spectral range that differs from that of the first optical resonator; locking an optical reference signal to a closest axial mode of a reference optical resonator producing an optical reference signal that is spectrally offset from said optical carrier frequency by a spectral quantity less than the known free spectral range; mixing the optical carrier frequency with the reference optical signal frequency thus generating a difference signal as a beat frequency; and measuring a frequency of a difference signal.

Abstract: A method and apparatus are provided for detecting a frequency of an optical signal within a communications channel having a plurality of optical carriers separated by a predetermined frequency spacing. The method includes the steps of locking an optical carrier frequency to an axial mode of an optical resonator of known free spectral range; providing an additional optical resonator as a reference having a known free spectral range that differs from that of the first optical resonator; locking an optical reference signal to a closest axial mode of a reference optical resonator producing an optical reference signal that is spectrally offset from said optical carrier frequency by a spectral quantity less than the known free spectral range; mixing the optical carrier frequency with the reference optical signal frequency thus generating a difference signal as a beat frequency; and measuring a frequency of a difference signal.

Abstract: A method of frequency stabilizing a semiconductor laser. The method includes the steps of detecting a heterodyne beat note by optically mixing a leakage field of an optical resonator and a frequency modulated output of the semiconductor laser and detecting a phase of the heterodyne beat note by mixing the heterodyne beat note in quadrature with a radio frequency reference signal. The method further includes the steps of filtering the detected phase of the heterodyne beat note, scaling the filtered detected phase of the heterodyne beat note, and modulating the semiconductor laser with the scaled detected phase of the heterodyne beat note and the radio frequency modulation reference signal.