Strain and temperature dependencies of multimodal interference spectra in hetero-core-fiber structures

We investigate, for the first time, the temperature and strain dependencies of the spectral dips of the multimodal interference patterns in hetero-core-fiber structures at telecom wavelength. With increasing temperature and strain, the spectral dips shifted to shorter wavelengths with dependence coefficients of -3.5 nm C^-1 and -0.62 pm/μϵ, respectively. Their absolute values were ∼60 times larger and ∼30 times smaller than the temperature and strain sensitivities of a standard single-mode-multimode-single-mode sensor, respectively. This result implies that the hetero-core-fiber structures can be potentially used to develop highly sensitive temperature sensors with reduced strain sensitivity.