US Patent 7893395 Optical delay lines

This invention relates to optical delay lines, particularly to modifying an optical signal passing through an optical delay line. A method of applying a Doppler shift to an optical signal as it passes through an optical delay line is provided, the method comprising the step of progressively altering a property of the optical delay line during passage of the optical signal therethrough such that the time taken for the optical signal to pass therethrough is progressively lengthened or progressively shortened for successive portions of the optical signal. In addition, an optical delay line is provided that may be used in accordance with the above method.