Mach–Zehnder carbon monoxide gas sensor based on tin dioxide coated endlessly single-mode photonic crystal fiber

Abstract A Mach–Zehnder interference (MZI) carbon monoxide gas sensor based on tin dioxide-coated single-mode photonic crystal fiber (ESPCF) was constructed. Using the collapse fusion method, a piece of tin dioxide-coated ESPCF is embedded between the two ends of the seven-core fiber (SCF) to form an SCF-ESPCF-SCF optic-fiber sensor with an MZI sensing structure. To examine the properties of the sensing layer, including its crystalline structure, elemental makeup, and surface appearance, we utilized XRD for diffraction studies, XPS for compositional analysis, and SEM for morphology imaging. The outcomes confirm the successful synthesis of the tin dioxide sensing material, with the formation of a uniform morphology, coating approximately 1.5 μm in thickness on the fiber’s surface. Notably, the sensor exhibits a sensitivity to carbon monoxide of 0.01696 dB/ppm, with activation and reset durations being 60 s and 72 s, correspondingly. The sensor demonstrates high sensitivity, strong selectivity, a favorable linear response, and stability, rendering it highly efficacious for the environmental monitoring of toxic carbon monoxide gas.