Two-dimensional microbend sensor based on long-period fiber gratings in an isosceles triangle arrangement three-core fiber.

To realize the 2D microbend sensor, we design and fabricate two non-orthogonal long-period fiber gratings (LPFGs) in an isosceles triangle arrangement three-core optical fiber which is made in our lab, making an isosceles triangle arrangement three-core optical fiber. To mark two directions without crosstalk, we write two different periods of LPFG in each of the two external cores and the central core, which induces a strong asymmetric refractive index arrangement in the fiber cross section. Theoretical analysis and experimental results verify that the resonant wavelength originates from the tunneling between the LP01 core mode in the center core and the external core. In the confirmation experiments, the proposed sensor can distinguish multiple bending directions and experiences a maximum sensitivity of 3.234  nm/m-1 with a bending range of 0-0.588  m-1.