3-D Parallel Fiber Bragg Gratings Bending Sensor Based on Single-Channel Measurement

A bending sensor is proposed to demodulate the multichannel bending signals of multicore fiber (MCF) to single-channel signals by using the phase mask method combined with the thermal diffusion technique (TDT). A four-core fiber (FCF) bending sensor was fabricated. Each fiber core of the FCF had different resonant wavelengths through the method of core-by-core inscribed fiber Bragg gratings (FBGs) at the same axial position. The FCF was coupled with a single-mode fiber (SMF) by the TDT method. Finally, the single-channel measurement of the 3-D parallel FCF FBGs signals was realized. The FBGs on four cores of FCF were equivalent to the FBGs on two orthogonal cores by a different operation. The experimental results showed that the maximum bending sensitivities of the equivalent FBGs were 187.2 and -192.6 pm/m(-1), respectively. This sensor realized single-channel demodulation of MCF signals with the elimination of the crosstalk caused by temperature and strain. The proposed sensor fabrication technology with high integration, high sensitivity, and reduced crosstalk, is expected to be applied in the field of 3-D shape measurement or wearable artificial electronics.