Detailed investigation of spectral properties of SMS fiber segment and its sensing performance under varying multimode fiber lengths

Here, a comprehensive analysis of the impact of the multimode fiber (MMF) lengths on different sensitivities of single mode-multi mode-single mode (SMS) fiber segment sensor probe under different external perturbations such as temperature, strain and refractive index has been propounded and studied thoroughly. In addition, different phenomenal characteristics of the SMS segment namely fast Fourier transform, fringe visibility, the free spectral range of the observed transmission spectrum and most importantly the self-imaging phenomena have been investigated meticulously. These aforementioned characteristics are also verified theoretically. The experimental results show that the sensitivities increase with an increase of the MMF length and are restricted to 12 cm length due to the superimposing and less resolution of the probing dips beyond this. Experimental results illustrate that our proposed sensing probe is capable to achieve superior sensitivities better than 93 pm/degrees C,-2.56 pm/ mu epsilon and-38.55 nm/RIU for temperature, strain and refractive index, respectively for the 12 cm length of the MMF. The higher sensitivities and resolutions assure potential employment and promising solution of the proposed sensor in various sensing applications.