Temperature Insensitive Polarization Maintaining Photonic Crystal Fiber Refractive Index Sensor

A tapered polarization maintaining photonic crystal fiber based on dual-mode interference is proposed for measuring liquid refractive index. The sensing principle is based on the interference between LP01 and LP11 modes in the photonic crystal fiber. The output intensity distribution of the two modes in the fiber is investigated in detail. It is shown that when the external refractive index changes the two–lobe interference pattern of the fiber generates energy exchange. The relationship of the refractive index and the normalized value which is defined as difference to the sum of the two lobes interference intensity is studied. The analyzed results demonstrate that the sensor has refractive index sensitivity of 31.9/RIU (Normalized Value/ Refractive Index Unit) within the range of 1.36-1.4 RIU. As the two modes in the fiber have the same response to the temperature, the sensor possesses the anti-interference ability. Because of the easy fabrication, compact size and the ability of anti-interference to temperature make the sensor has extensive application prospects. Keywords-refractive index sensor; polarization maintaining fiber; two-lobe interference; photonic crystal fiber; tapered fiber