Patent ID: 6870967
Filing Date: 2005-03-22
Classification: G02B

Abstract:
1. A Method of inducing a phase change in a finite response filter, which comprises a concatenation of tunable couplers, and at least one tunable delay line, both comprising planar SiON-based waveguide arms, said tunable couplers and said at least one tunable delay line forming a plurality of interferometers, at least one of which carries a heater on at least one of its wave guide arms, characterized in that at least one of said arms of the interferometers is exposed to an irradiation at UV or a smaller wavelength, thereby inducing a change in refractive index which induces said phase difference change, wherein the characterized step comprises the additional steps of: a) determining an initial phase difference for an optical signal transmittable in the waveguide arms of at least one of said interferometers; b) determining a desired phase difference for a target frequency response; and c) comparing the phase differences of steps a) and b) and calculating therefrom a phase difference change to be induced, before exposing said at least one of said arms of the interferometers to said irradiation.