Development of novel handheld optical fiber dissolved oxygen sensor and its applications

A simple and robust integrated handheld optical fiber dissolved oxygen (DO) sensor was developed based on a compact optical structure and phase shift measurement principle. In this device, a 1 × 4 multi-mode optical fiber bundle structure was used for the transmission of excitation light and the collection and transmission of fluorescence. The fiber optode was fabricated by coating an O₂ sensing foil on the end of the optical fiber bundle. This elegant optical design significantly improved the optical transmission efficiency, miniaturization, portability, and stability of the entire sensor system. A low-cost photodetector (PD) was applied for simultaneous detection of the fluorescence signal and reference light signal based on the time-resolved effect. Rapid and accurate measurement of the phase shift between the fluorescence and reference light signals was achieved using phase measurement electronics and signal processing system. Based on a proposed theoretical model with temperature compensation calibration, this DO sensor was used for rapid, accurate, and reproducible detection of DO concentrations with long-term stability and low drift. The results of in-situ/on-line detection for various water samples were highly consistent with those of commercial optical oxygen sensors. The proposed DO sensor has the potential to be a powerful alternative to traditional oxygen sensors in laboratory or in field.