The paper presents an entirely fiber optic Mach-Zehnder interferometer formed in a polarization maintaining photonic
crystal fiber (PM PCF). It uses the interference between the polarization modes and the cladding modes. The method of
collapsing the air holes in a single segment of the PM PCF was applied to excite the cladding mode from the polarization
modes of the PM PCF and create the coupling region of these modes. Measurements of the wavelength spectra of the
produced interferometers were performed. The influence of the interferometer length on the period of the wavelength
spectrum was investigated experimentally. On the basis of these measurements the difference of the group refractive
indices of the polarization modes and the cladding mode was determined. The dependence of the strain sensitivity
coefficient of the produced interferometers on the wavelength was determined experimentally. The possibilities of
application of the constructed interferometer for sensors are presented.
Presented is a compact, all-PCF modal interferometer made by fusion splicing. The splices were performed in such a way as to cause the holes of the PCF to collapse over the length of the splice. The modal interferometer is created by the segment of a birefringent PCF, including the micro-collapses at the ends, and SMF-28 pigtails spliced to it. Obtained spectra of the interferometer and an estimation of its parameters are presented. The effect of tensile strain on the spectrum is illustrated. The application possibilities of the constructed interferometer for sensors are given.