Waveguide Coupled Novel Multicore Rectangular Polymer Optical Fiber for Curvature Sensor

This study demonstrates the use of a three-core rectangular (TCR) polymer optical fiber (POF), inscribed with FBGs, for curvature measurement. The incorporation of cyclo-olefin polymer ensures that the fiber is insensitive to humidity. Well distinguished FBGs are inscribed in all the cores using femtosecond laser-based point-by-point technique. All these cores have been coupled to the incident light source simultaneously using a few mode fiber-based waveguide coupler where two additional cores have been inscribed using femtosecond laser based multiple scanning technique. This polymer fiber system offers a broader range of curvature measurements compared to silica fibers. The response of sensor to the applied curvature was monitored along both ±X and ±Y axis. The sensor exhibits maximum curvature sensitivities of 119 pm/m^-1 and 190 pm/m^-1 along the two orthogonal axes, along with a maximum temperature sensitivity of 8 pm/°C.