High-sensitivity all single-mode fiber curvature sensor based on bulge-taper structures modal interferometer

An optical fiber curvature sensor based on bulge-taper splicing structures modal interferometer is proposed and experimentally demonstrated. The sensor is fabricated by a length of 10 mm single mode fiber (SMF) which is spliced between two SMFs with bulge-taper splicing. The results show that the sensor is sensitive to curvature with a sensitivity coefficient of −31.821 nm/m−1 in the range of 4.29-4.98 m−1 and −17.051 nm/m−1 in the range of 4.98-5.59 m−1. The proposed sensor also shows the temperature sensitivity of 72 pm/°C, and the curvature error caused by temperature is only 0.0023 m−1/°C in the range of 4.29-4.98 m−1 and 0.0042 m−1/°C in the range of 4.98-5.59 m−1. This sensor exhibits the advantages of compactness, robustness, low cost, all-SMF structure, easy and repeated fabrication, and high sensitivity.