Sensing performance of U-shaped fiber in chaotic correlation fiber loop ring down system

We experimentally demonstrated a high sensitivity chaotic correlation fiber loop ring down sensing based on U-shaped fiber optical sensor. The U-shaped fiber optical sensors with different bending diameters were spliced into fiber loops with different cavity lengths to study the influence of cavity length and bending diameter on detection sensitivity. The relationship between cavity length and sensitivity was investigated theoretically and experimentally. The limit of sensitivity was analyzed theoretically and the highest sensitivity of 2253.390 μs−1RIU−1 in the refractive index range of 1.3347–1.3721 was realized experimentally. A handheld probe measuring device was obtained by combining short cavity fiber loop ring down and U-shaped fiber optical sensor, and the probe device can achieve the detection of hemoglobin level with the high sensitivity.