Patent ID: 6842283
Filing Date: 2005-01-11
Classification: G02B,G02F,H04B

Abstract:
1. A device for applying a variable differential group delay to a signal at an input of the device, and for providing the modified signal it an output of the device, the device comprising: first, second and third birefringent elements arranged in order between the input and output of the device and having first, second and third differential group delays (DGDs) in the ratio 1:2:1, and having principal axes, the first second and third differential group delays being significantly larger than the optical period of the signal at the input of the device; means for controlling, in each birefringent element, the orientation of the PSPs of the signal in the element relatively to the principal axes of the element, the control being such that a change in orientation between the first and second elements is equal and opposite to a change in orientation between the second and third elements.