Patent ID: 7127179

Claim:
An optical apparatus, comprising: at least one optical component arranged along a transmission path of at least one light beam coupled as an input to the apparatus, the light beam containing a plurality of wavelengths defining channels, wherein said optical component is controllable to effect a polarization transformation, and wherein the optical component comprises at least one variable birefringent element that is controllable as to at least one of phase retardation and orientation by at least one perturbation selected from the group consisting of electrical, mechanical, thermal, magnetic, and optical perturbation; a control operatively coupled to the at least one optical component so as to vary a characteristic of said optical component such that at least one of the channels is imparted a polarization state by said at least one optical component, that is distinct from a state of at least one other of the channels, whereby said at least one of said channels can be discriminated by said distinct polarization state; wherein said apparatus is selectably controllable to effect said polarization transformations; at least one polarization control device disposed along the transmission path with the component, wherein the polarization transformation by the component sets a portion of at least one input to said distinct polarization state, and said portion is coupled to at least one output of the apparatus; and, a feedback sensor operable to determine an output level of the apparatus at least at one output defined by at least one attribute of output, and a control responsive to the sensor, the control being coupled to adjust at least one said variable birefringent element to achieve a predetermined intensity attenuation at least at one wavelength at said output.