Vector bending sensor for measuring spine curvature

Abstract

A three-core photonic crystal fiber (TCPCF) vector bending sensor for measuring spine curvature is proposed. Refractive index variations of the TCPCF due to the wavelength differences in the range of 1.25 to 1.85 μm are studied. We show a linear relation between refractive index and operating wavelength. The wavelength of 1.55 μm is chosen for simulation with high energy modules to compensate for bending loss. An asymmetrical fiber is designed to sense both the direction and magnitude of the curve. The asymmetrical geometry of fiber creates an asymmetrical refractive index profile that leads to shifts in light speed in different fiber sections. This geometry asymmetry, in turn, provides the information needed to calculate both variables. Bending effects on the TCPCF has been numerically studied by the finite element method. Data analysis shows that the proposed sensor is sensitive to bending with a sensitivity of 1.2199 pm.m. It also reveals high directional sensing.