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.