Low crosstalk dual parameter fiber optic sensor for simultaneous temperature and pH detection based on femtosecond laser processing

This study presents a groundbreaking dual-channel sensing technology embedded within a meticulously fabricated microcavity optical fiber structure using femtosecond laser technology. This microcavity design enables the generation of both surface plasmon resonance (SPR) and Mach-Zehnder interferometer (MZI) signals, eliminating crosstalk—a critical challenge in traditional multi-parameter sensing. This achievement ensures a precise one-to-one correspondence between output signals and the measured variables. Using layer-by-layer self-assembly, the SPR sensing region was selectively modified with a pH-sensitive material. In parallel, the temperature-sensitive material was integrated into the microcavity via microfluidic filling. This dual approach facilitates the simultaneous detection of temperature and pH levels. Experimental results validate the technology's exceptional capabilities: the SPR channel exhibits a remarkable sensitivity of −16.5 nm/pH for pH monitoring, while the MZI channel demonstrates a sensitivity of 1.15 nm/ °C for temperature detection. These values represent significant advancements over previous studies. The sensor developed in this research offers several key advantages: simultaneous temperature and pH measurement, minimized crosstalk, and outstanding sensitivity. This technology holds tremendous promise for enhancing water quality monitoring, safeguarding aquatic environments, and controlling water pollution, marking a significant step forward in environmental protection technologies.