Patent ID: 6993257

Claim:
An optical channel monitor, comprising: an optical input port; a photodetector disposed in an optical path communicating at least intermittently with said optical input port; an optical filter disposed in said optical path between said optical input port and said photodetector; an optical band splitter disposed in said optical path between said optical filter and said photodetector; an optical reference system in optical communication with the optical band splitter between said photodetector and said optical filter and configured to generate a reference signal; and a comparison device configured to compare a measurement signal with said reference signal by generating a first wavelength-to-voltage function for the reference signal and generating a second wavelength-to-voltage function for the measurement signal, wherein said second wavelength-to-voltage function is generated using a wavelength transform function consisting of relating the wavelengths in the reference optical signal with the wavelengths in the measurement signal with the following equation: λ m−1 =(m/m−1) λ m where m and m−1 represent the order of the wavelength passband, m being an integer number greater than 1, λ m and λ−1 m are wavelengths transmitted at the m th and m−1 th order respectively.