Effects of Material Deformation on U-shaped Optical Fiber Sensor

This work presents an evanescent wave-based U-shaped plastic optical fiber sensor. The effect of bend-induced material deformation on numerical aperture (N.A) and V-number has been thoroughly investigated. With sufficiently smaller bend radius, the numerical aperture of a U-bent fiber decreases toward zero near the inner curvature of the bending. The present scenario causes entire optical power loss at interface between core-clad (sample region) interfaces, resulting in no detectable power. It has been observed that as the bending radius increases, the local N.A value decreases while the refractive index of the surrounding region remains fixed. As a result, the fractional power in the surrounding region rises, resulting in increased absorbance and sensitivity of the EW absorption-based optical fiber sensor.