Patent ID: 7154668

Claim:
An apparatus for providing a profile of attenuation as a function of wavelength, in an optical system for carrying a plurality of wavelengths in a wavelength range of interest, the apparatus comprising: at least one light transmission path for the plurality of wavelengths, wherein the wavelength range of interest is presented as a polarization-referenced input signal with predetermined polarization states; a differential phase retardation section coupled to the polarization-referenced input signal, the differential phase retardation section including at least two birefringent elements, so as to produce a change in polarization state as a function of wavelength, in an output from the differential phase retardation section; and, further comprising at least one polarization-referenced output element operable to discriminate components of the output of the differential phase retardation section as a function of polarization state; and, a control circuit operable to generate a set of control signals that are applied to the birefringent elements to obtain a desired contoured profile of attenuation as a function of wavelength.