Multichannel Directional Recognition SPR Curvature Sensor Based on D-Type Double-Clad Multimode Fiber

A fiber surface plasmon resonance (SPR) curvature sensor has the advantage of being insensitive to axial strain and temperature, but there are still difficulties in multichannel cascade and curvature direction identification. In this article, a multichannel directional recognition SPR curvature sensor based on D-type double-clad multimode fiber was proposed. The asymmetric structure of D-type multimode fiber can well realize directional curvature sensing. When the light in the multimode core leaks to the silica clad, due to the existence of plastic clad, it can still continue to transmit. When the refractive index of UV curable adhesive coated in different sensing areas is different, wavelength-division multiplexing multichannel sensing can be realized. When the sensing probe is bent to be convex, the maximum intensity sensitivity is 0.0057 a.u./m−1, the resonance wavelength is redshift, and the wavelength sensitivity is 0.6114 nm/m−1. When the sensor probe is bent to be concave, the maximum intensity sensitivity is 0.0043 a.u./m−1, the wavelength is blueshift, and its highest sensitivity is 0.5831 nm/m−1. In addition, this article also realizes a three-channel directional recognition SPR curvature sensor based on a D-type double-clad multimode fiber, which provides a new scheme for multichannel directional curvature measurement.