Patent ID: 7840100

Claim:
A method of changing the dispersion of a light beam, the method comprising: a) providing at least a first and second dispersion compensating elements each comprising a GT etalon cavity having a highly reflective surface and a partially reflective surface separated from said highly reflective surface by a transparent material, the GT etalon cavities of said at least first and second dispersion compensating elements are characterized respectively by at least first and second group delay frequency profiles; b) causing the light beam to pass through each of said at least first and second dispersion compensating element, and to leave the respective dispersion compensating element; c) directing the light beam to interact with one or more of said at least first and second dispersion compensating elements at least one additional time thereby causing multiple interactions of the light beam with the dispersion compensating elements and increasing the effect of the dispersion compensation; wherein said at least first and second group delay profiles of said GT etalon cavities are selected such that within a central frequency of one or more frequency channels the second frequency derivatives of said at least first and second group delay profiles add substantially to zero providing for group delay ripples of the order of third frequency derivatives of said at least first and second group delay profiles.