All fiber curvature sensor based on modal interferometer with waist enlarge splicing

• A novel curvature sensor based on polarization-maintaining fiber interferometer with waist enlarge splicing is proposed.
• The sensitivity of −10.634 nm/m−1 and 10.152 nm/m−1 were acquired by concave and convex bending with the range of 0–2.054 m−1
• The PMF-based sensor has a higher sensitivity than the SMF-based one.
• The length of PMF is shorter, the sensitivity of the sensor is higher.
• The waist-enlarge splicing can make sensor stable.

A novel fiber curvature sensor based on modal interferometer with waist-enlarge splicing is proposed. A section of 30 mm polarization maintaining fiber (PMF) is spliced with waist enlarge between two conventional single mode fibers (SMFs) to construct an all fiber curvature sensor. The results show that the transmission spectrum has a blue and red shift, corresponding to the opposite curvature directions. The sensitivity coefficient of −10.634 nm/m−1 and 10.152 nm/m−1 were acquired by concave and convex bending with the range from 0 m−1 to 2.054 m−1, and the corresponding resolution were 9.4 × 10−4 m−1 and 9.85 × 10−4 m−1, respectively. And the influence of different lengths of PMF on the sensitivity was also discussed.