<title>Multistage fiber optic delay line for astronomical interferometry</title>

Abstract

In fiber optic Fourier transform spectrometry (FTS), fiber optic double Fourier interferometry (DFI) and, probably, in single-mode fiber-linked telescope array, fiber delay lines are needed to make the system all-fiber optic, which will results in many advantages. Fiber-stretching operation has been demonstrated to be one method in which a piece of fiber is stretched mechanically to generate optical path difference (OPD). Nevertheless, this fiber-stretching operation has two drawbacks. First, it introduces additional polarization and dispersion effects, both of which are stretching state and wavelength dependent. Second, in practive, its maximum delay is limited. In this paper, we describe a new type of fiber delay line in which the fiber-stretching device (we call it OPD generator) is used to generate continuous OPD, and, OPD stores made of optical switch and two segments fibers having different lengths are employed to save and release the OPD that the OPD generator produces. The main advantages of this kind of fiber delay line are: 1) dispersion in the OPD stores may be minimized because the fiber in an OPD store is free of external strain, and polarization effect can be eliminated; 2) fiber-stretching operation will introduce less dispersion and polarization effects; hence 3) large optical delay may be obtained with shorter fiber. At the same time, performance of this kind of delay line is analyzed and the characteristics are discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.