An Optical Fiber Curvature Sensor Based on Two Peanut-Shape Structures Modal Interferometer

A novel curvature sensor based on optical fiber modal interferometer is demonstrated. It consists of two peanut-shape structures that are formed only by single mode fibers. The two peanut-shape structures can split and recombine the core and cladding modes, consequently, it produces modal interference. The experimental results show that the shift of the peak wavelength is almost linearly proportional to the change of curvature, and the sensitivities of the sensors with the lengths of 21, 26, and 30 mm are -18.46, -21.87, and 13.68 nm/m^-1, respectively. The proposed curvature sensor is simple, high sensitive, and inexpensive.