Spectral-domain interferometric techniques used to measure the intermodal group dispersion in a two-mode bow–tie optical fibre

Abstract

We present two spectral-domain interferometric techniques for measuring the wavelength dependence of the group optical path difference (OPD) between the LP y 01 and LP y 11 modes of a bow–tie optical fibre. One technique utilizes a set-up comprising a white-light source, a tandem configuration of a Michelson interferometer with a two-mode optical fibre under test and a low-resolution spectrometer. In the set-up we record a series of the spectral interferograms for measuring directly the dispersion of the intermodal group OPD. The other technique utilizes a set-up comprising a superluminescent diode (SLD), a two-mode optical fibre under test and a high-resolution spectrometer. In the set-up we record a single spectral interferogram for determining the dispersion of both the overall phase with 2π ambiguity and the intermodal group OPD. The experimental results obtained by both measurement techniques are compared each other confirming good agreement.