High Sensitivity Optical Fiber Curvature Sensor Based on Cascaded Fiber Interferometer

A highly sensitive optical fiber curvature sensor based on cascaded fiber interferometers (CFIs) is demonstrated theoretically and experimentally. Theoretical results show that the scheme of cascaded fiber interferometers can be regarded as an equivalent fiber interferometer with longer interference length and narrower FSR. It serves as a curvature sensor with sensitivity up to 4.362 nm/m^-1 within the measurement range of 0-1.134 m^-1. Compared to the single fiber modal interferometer, the curvature sensitivity of the CFI is almost doubled. In addition, simultaneous curvature and temperature measurement is achieved using the coefficient matrix method, eliminating the issue of temperature cross sensitivity.