Spectral-domain measurement of strain sensitivity of a two-mode birefringent holey fiber

Abstract

In this paper, the strain sensitivity of a two-mode birefringent holey fiber is measured in the spectral domain. In a simple experimental setup comprising a broadband source, a polarizer, a two-mode birefringent holey fiber under varied elongations, an analyzer and a compact spectrometer, the spectral interferograms are resolved. These are characterized by a specific wavelength, the equalization wavelength, at which spectral interference fringes have the highest visibility (the largest period) due to the zero group optical path difference between the fundamental, the LP01 mode and the higher-order, the LP11 mode. The spectral interferograms with the equalization wavelength are processed by a new method to retrieve the phase as a function of the wavelength. From the retrieved phase functions corresponding to different elongations of a two-mode birefringent holey fiber under test, the spectral strain sensitivity is obtained. Using this approach, the intermodal spectral strain sensitivity was measured for two orthogonal (x and y) polarizations.