Ultra-sensitive glucose optical fiber sensor based on an open cavity structure with the vernier effect

In this paper, an ultra-sensitive glucose optical fiber sensor based on an open cavity structure with the vernier effect is proposed. By cascade and bias fusion of multiple types of optical fibers, a high sensitivity sensor unit based on Mach–Zehnder interferometer is obtained. By cascading it with a Sagnac interferometer as a reference unit, the vernier effect can be formed to further enhance the sensitivity. The simulation and experimental results have confirmed that the proposed optical fiber sensor has extremely high sensitivity. In the experiment, the refractive index sensitivity of the sensor can reach 81461.7 nm/RIU. Moreover, it is employed for the direct measurement of clinically relevant glucose solution. Within the linear glucose concentration range of 0-30 mM, the sensitivity is up to -2.032 nm/mM. This proposed sensing configuration offers the advantages of simple preparation, high sensitivity, and good stability, making it highly promising for applications in the chemical and biochemical detections and dynamic process monitoring.