Multimode interference-based strain sensing using polarization-maintaining fiber at telecommunication wavelengths

We demonstrate strain sensing based on multimode interference using a simple single-mode fiber-polarization-maintaining fiber-single-mode fiber (SMF-PMF-SMF) structure at telecommunication wavelengths. A commercially available PMF designed for >1850 nm operation produced clear interference spectra around 1550 nm. When strain was applied to the PMF, the spectral peaks shifted linearly with a sensitivity of 0.52 pm/μϵ, while no spectral change was observed for the adjacent SMFs. These results confirm that the strain response originates exclusively from the PMF, validating its feasibility as a multimode element for strain sensing at standard telecommunication wavelengths.