Experimental demonstration of the spectral interference between two linearly polarized modes at the output of a fibre waveguide excited by a low-coherence source

The mutual interference of two linearly polarized (LP) modes in the frequency domain has been demonstrated experimentally at the output of a fibre waveguide excited by a low-coherence source when the optical path difference between both LP modes exceeds the coherence length of the source. The spectral interference between two LP modes, which shows up a periodic modulation of the source spectrum, serves as an illustration of the experimental verification of conclusions we have made in previous theoretical works. Consequently, the feasibility of a novel experimental method utilizing a high-resolution spectrometer in the evaluation of the group-delay time difference between both LP modes has been confirmed.