Optical fiber curvature sensor based on MMF-SCF-MMF structure

•A curvature sensor based on SCF has been proposed and experimentally demonstrated.•The fabrication use a commercial fusion splicer, which is extremely easy to operate.•The structure of the sensor is simple, and the cost of the sensor is low.•The sensitivity reaches 41.46453 nm/m−1 that is higher than other curvature sensor.•The influence of MMF is analyzed in detail.