Simultaneous directional curvature and temperature sensor based on a tilted few-mode fiber Bragg grating.

We demonstrate a directional curvature sensor based on tilted few-mode fiber Bragg gratings (FM-FBGs) inscribed by a UV laser. The eigenmodes of LP01 and LP11 mode groups are simulated along with the fiber bending. The directional curvature sensor is based on the LP11 mode resonance in the tilted FM-FBG. For curvature from 4.883 to 7.625  m-1, the curvature sensitivities at direction of 0° and 90° are measured to be -2.67 and 0.128  dB/m-1, respectively. The temperature variation barely affects the resonance depth of LP11 mode. The proposed curvature sensor clearly demonstrates the potential to simultaneous directional curvature and temperature measurement with the resolutions of 9.15×10-4  m-1 and 0.952°C, respectively.