Amplification of optical delay by use of matched linearly chirped fiber Bragg gratings

We describe the use of a matched linearly chirped fiber Bragg grating (FBG) pair as a key element in an adjustable optical delay line. This delay line has the unique property that the achievable optical group delay is orders of magnitude greater (factor of 10^2 in our experiment) than the actual physical displacement. We demonstrate operation of such an optical delay line over a delay range of 3.5 mm using a pair of matched 1300-nm chirped FBGs with a bandwidth of 20 nm each.