Numerical study of refractive index sensing based on the anti-guide property of a depressed-index core photonic crystal fiber

Refractive index (RI) sensing based on the anti-guiding property of a depressed-index core photonic crystal fiber (PCF) is studied. A new type of RI sensor is formed by adding a hole to the core of a conventional index guiding PCF for the purpose of measurand filling and the depressed-index core formation. The dependencies of measurement resolution and dynamic range on the structural parameters of the RI sensor are investigated. RI sensors filled with the measurand covering a refractive index range from 1.328 to 1.445 are numerically simulated. Simulation results show that the measurement resolution from 9.32 × 10-7to 1.23 × 10-7can be achieved by means of wavelength measurement with an optical spectrum analyzer with 0.01 nm resolution. Also, problem caused by the existence of the photonic bandgap (PBG) mode which may influence the feasibility of the RI sensing mechanism is considered.