The Mutual Interference of Modes of a Few-mode Fibre Waveguide Analysed in the Frequency Domain

Abstract

The interference between modes of a few-mode weakly guiding fibre waveguide is investigated in the frequency domain at the exit face of a fibre waveguide as well as at the output of a Michelson interferometer by using classical coherence formalism and the coherent-mode representation. It is revealed that a variable sinusoidal spectral modulation is present at the exit of a two-mode fibre waveguide and that the mutual interference of modes analysed at the output of a Michelson interferometer by a low-resolution spectrometer gives the interference fringes of suitable visibility. A comparison is made between the interference in the frequency domain and that in the time domain with particular emphasis on possible sensor applications.