Highly sensitive polymer optical fiber sensors based on periodic semi-ring-V-shaped microgroove structures for trace liquid leakage detection

In this paper, a polymer optical fiber (POF) sensor based on a periodic semi-ring-V microgroove structure (PSVMS) is proposed for trace leakage detection, in which a microstructured POF is integrated with a flexible light-emitting diode (LED) strip to achieve leakage sensing via the side-coupling mechanism and intensity-modulation principle. To determine the parameters of PSVMS, a complete theoretical model of the side-coupling mechanism is developed for the first time. Simulations indicate that a groove depth of 300 µm, a groove width of 200 µm, and five grooves per unit exhibit optimal performance in leakage detection sensitivity. A PSVMS pattern is fabricated on a 2 mm POF sidewall using a CO₂ laser. Experimental results demonstrate that the sensor achieves a minimum detectable leakage volume of 500 nL, which is nearly three orders of magnitude lower than that of conventional sensors, with an approximate 10% power change. At a leakage volume of 1 mL, the power change increases to 75%, and repeatability tests yield a coefficient of variation below 5%, confirming high reproducibility and consistency. The low-cost sensor offers a promising approach for trace liquid leakage detection.