A novel sensing peak identification method for high accuracy refractive index (RI) sensing is proposed. The implementation takes the intensity of interference maximum as the characteristic to distinguish interference peaks, tracking the sensing peak continually during a RI changes, with high measurement accuracy and simple computation. To verify the effect of the method, the extrinsic Fabry–Perot interferometer (EFPI) sensor has been fabricated using the large lateral offset splicing technique. In the RI range from 1.346 to 1.388, the measurement range of the EFPI with the proposed method reaches at least 6 times larger than that of EFPI with the wavelength tracking method and the largest measurement error is −4.47 × 10⁻⁴. The EFPI refractive index (RI) sensor identified the sensing peak is believed to play an important role in RI, concentration and density sensing, etc., for superior performance.

A high sensitivity curvature sensor based on singlemode-tapered multimode-singlemode (STMS) fiber structure has been proposed and demonstrated theoretically and experimentally. Due to elastic-optical effect, light field distribution of the STMS structure would be asymmetric when bending is applied, resulting in a profound effect on the transmission characteristics of the STMS structure. The experimental results show a good agreement with the trend of the theoretical predictions. Adopting the intensity demodulation in experiments, an average sensitivity of -21.734 dB/m-1 over the range of 0.7064 to 1.9129 m-1 and the maximum sensitivity of -144.876 dB/m-1 at the curvature of 1.9129 m-1 have been achieved. Besides, the dependence of temperature on the transmission spectrum of this curvature sensor has been investigated, showing a low temperature cross-sensitivity. Because of these superior properties, this curvature sensor could find useful applications in architecture, mechanical engineering, and medical science.