Photonic crystal fiber pressure sensing based on birefringence effect

In order to achieve high sensitivity of pressure magnitude and direction measurement, the elasto-optical effect of photonic crystal fiber is studied by the full vector finite element method. First of all, the birefringence characteristics of the fundamental mode of the edge-pass high birefringence photonic crystal fiber under lateral pressure and static liquid pressure are studied. The results show that the effective refractive index of the two polarization fundamental modes changes obviously under the static liquid pressure, the phase mode birefringence changes linearly with the pressure. The second, the influence of fiber structure on birefringence is discussed, the results show that the size of birefringence can be influenced by changing the shape, position and size of the air holes in the fiber. The structure of photonic crystal fiber with high birefringence is obtained by optimizing the structure. The result show that, when free space wavelength is 1.55μm and pressure is 120MPa, the sensitivity of its phase modal birefringence up to 1.498×10^-5 MPa_-1 and the maximum measurable hydrostatic pressure value is 353MPa. The research is meaningful to realize the pressure sensor with multi-angle and high sensitivity.