Patent ID: 8594498

Claim:
An optical signal-to-noise ratio monitor comprising: a. a demodulator comprising an input that receives an input signal comprising at least a portion of a phase modulated optical signal and a delay interferometer that splits the input signal into two signals where one signal is delayed relative to the other signal by a differential delay, the delay interferometer having a periodic phase control that sweeps the differential delay of one arm of the interferometer through a plurality of differential optical phase shifts, the demodulator converting phase modulated optical signals to intensity modulated optical signals; b. a tunable optical filter that is optically coupled to the output of the demodulator, the tunable optical filter continuously scanning 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; c. an optical detector having an input that is positioned at an output of the tunable optical filter, the optical detector detecting the filtered optical signal and generating a corresponding electrical demodulation signal at an output; and d. a processor having an input that is electrically coupled to output of the optical detector, the processor determining an optical signal-to-noise ratio for the more than one wavelength of the optical signal.