Enhanced Spectrum Resolution of Optical fiber Refractive Index Sensors Based on Single-arm Fiber-optic Tapered Probe

In light of the low resolution of the interference spectrum and the low demodulation accuracy of the existing interference-type refractive index sensors, a reflective mode interferometric sensor based on a Single-arm fiber-optic tapered probe (SAFTP) is proposed. This structure consists of a section of single-mode and no cladding fiber that is fused without eccentricity. By defining the depth-to-width ratio and preparing probes with different taper angles, the interference peaks are tuned to meet the high sampling resolution requirements of spectral measurement instruments. Within a limited bandwidth range, the greater the depth-to-width ratio, the wider the range of the measured physical quantity. From the perspective of spectral measurement instruments spectral acquisition, under the same bandwidth and number of acquisition points, the smaller depth-to-width ratio results in a higher spectral interference sampling resolution. Finally, the refractive index sensitivity of the SAFTP was calibrated under the optimal taper angle, allowing for the successful detection of the refractive index of silicone oil. Given the significant role of methyl silicone oil in aviation and precision instruments, it is crucial to utilize tunable SAFTP to measure the refractive index of silicone oil under various operating conditions. This will enable oil detection and assessment of silicone oil.