Refractive Index Sensors Based on a Chirped Core Long-Period Fiber Grating

A compact RI sensor with a high sensitivity based on LPFG is designed and experimentally confirmed. The proposed sensor is realized by splicing different fibers, which gives it stable mechanical performance. The simulation results indicate that, at short lengths, a high sensitivity is achieved by optimizing the strength of the evanescent field. Consistent with the simulation results, the sensor demonstrated a high RI sensitivity (>600 nm/RIU in 1.42) and a compact size (about 2.7 mm) in the experiment. The temperature response of the sensor is 19 pm/°C at the range of 26–90 °C. The compact size and high RI sensitivity give this LPFG a competitive advantage in various refractive index measurement engineering applications.