Three-Axis Curvature Sensor Based on Fiber SPR

The advantage of the fiber surface plasmon resonance (SPR) curvature sensor is being insensitive to temperature and axial strain, but multidimensional curvature measurement has not yet been achieved. In this article, a three-axis curvature sensor based on fiber SPR was proposed. By CO2 laser, the plane grooves were etched on the three axial planes of the graded index multimode fiber to fabricate the SPR sensing area. Seven-core fiber was used to inject light to realize the control of SPR effect on different axial planes. By setting the refractive index environment outside the sensing area, the working wavebands of the three sensing areas are different. The bending of the sensing area causes the change of the SPR incidence angle, which corresponds to the movement of the SPR resonance valley. According to the working wavelength and wavelength shift, the axis and curvature value of the curvature can be demodulated. The experimental results indicate that the initial SPR resonance wavelengths of the three axial sensing regions are 600, 700, and 765 nm, respectively, with the highest bending sensitivity of 2.03, 2.31, and 2.89 nm/ $\text{m}^{-{1}}$ . A fresh approach to fiber SPR multidimensional curvature sensing is offered by the sensor that is being proposed in this article.