Multi-channel curvature sensor based on fiber bending loss wavelength and SPR

Fiber Bragg gratings and interferometric curvature sensors are easily disturbed by axial strain and temperature, and cascaded multi-channel curvature sensing is difficult. In this letter, a curvature sensor based on fiber bending loss wavelength and the surface plasmon resonance (SPR) mechanism is proposed, which is insensitive to axial strain and temperature. In addition, fiber bending loss valley wavelength demodulation curvature improves the accuracy of bending loss intensity sensing. Experiments show that the bending loss valley of single-mode fiber with different cut-off wavelengths has different working bands which is combined with a plastic-clad multi-mode fiber SPR curvature sensor to realize a wavelength division multiplexing multi-channel curvature sensor. The bending loss valley wavelength sensitivity of single-mode fiber is 0.8474 nm/m^-1, and the intensity sensitivity is 0.0036 a.u./m^-1. The resonance valley wavelength sensitivity of the multi-mode fiber SPR curvature sensor is 0.3348 nm/m^-1, and the intensity sensitivity is 0.0026 a.u./m^-1. The proposed sensor is insensitive to temperature and strain, and the working band is controllable, which provides a new, to the best of our knowledge, solution for wavelength division multiplexing multi-channel fiber curvature sensing.