Patent ID: 7692793

Claim:
Method comprising: a) introducing a first analyzing optical wavelength λ 1 into a tunable optical filter using a nominally fixed wavelength laser operating at a first temperature T 1 , the tunable optical filter being tunable by changing an operating parameter (parameter), and having a first calibration between optical wavelength and the operating parameter, b) varying the parameter of the tunable optical filter, c) measuring the optical power output from the tunable optical filter to produce a first optical power vs. parameter relationship, d) changing the temperature of the nominally fixed wavelength laser to temperature T 2 to produce a second analyzing optical wavelength λ 2 , e) introducing the second analyzing optical wavelength into the tunable optical filter, f) varying the parameter of the tunable optical filter, g) measuring the optical power output from the tunable optical filter to produce a second optical power vs. parameter relationship, h) comparing the first and second optical power vs. parameter relationships, i) based on said comparison changing the calibration of the tunable optical filter.