Design of doped double-core photonic crystal fiber sound pressure sensor with high sensitivity

In order to break the limitation of high Young's modulus of quartz material on the sensitivity improvement of fiber optic sensor in uniform radial direction, a doped double-core photonic crystal fiber sensing structure was proposed. The circular air holes were arranged on the fiber cladding to form hexagonal lattice. Polymethyl methacrylate was doped into the base-material area surrounded by the air holes on one side of the double-core photonic crystal fiber. The influence of cross-section parameters on sound pressure sensitivity under uniform stress was analyzed by COMSOL and the optimal structure was obtained. At the kPa level, the free spectral width is about 13nm. At the MPa level, the free spectral width is about 2.5465nm. The results show that the sensitivity of x polarized sound pressure is 0.15942nm/kPa at 1550μm. Compared with the Sagnac PCF pressure sensor, the size of this sensor is smaller, and the sensitivity at uniform radial direction is increased about 46.6 times. This work contributes to the design of the next generation underwater sound pressure sensor.