<title>Time-domain and spectral-domain low-coherence interferometry used for dispersion characterization of optical fibers</title>

Abstract

In this paper, time-domain analysis of a tandem configuration of a nondispersive Michelson interferometer and a two-mode optical fiber, and spectral-domain analysis of intermodal interference at the output of the optical fiber alone are presented when a low-coherence exciting source is used and effects of first-order and second-order intermodal dispersion are included. Time-domain analysis shows that the visibility dependence of the output interferogram consists of two side peaks corresponding to positive and negative imbalance of the interferometer that compensate for the group optical path difference (OPD) of two modes in the optical fiber. It is shown that the effect of second-order dispersion gives rise to a flattening and a symmetrical broadening of these two side peaks. Spectral-domain analysis shows that the wavelength- dependent modulation of the source spectrum is obtained at the output of the two-mode optical fiber alone. By processing the spectral modulation, the intermodal dispersion parameters can be obtained. Theoretical results are verified experimentally: the visibility dependences measured in the setup comprising a bulk-optic Michelson interferometer and a two-mode optical fiber give the intermodal group OPDs, and the wavelength- dependent modulations of the source spectrum measured at the outputs of the two-mode optical fibers alone give the wavelength dependences of the group OPDs between two modes of the optical fibers. Moreover, good agreements between the experimental results of both measuring techniques are confirmed.