Ammonia detection in water with balloon-like plastic optical fiber sensor

Abstract

This work presents the demonstration of a plastic optical fiber (POF)-based ammonia sensor. The sensor head is formed by bending an unclad fiber optic sensor into a balloon-like structure. The bending radius of the balloon-like bent fiber optic sensor is varied from 1.0 to 2.5 cm. The performance of each sensor is tested using ammonia solution with concentration ranging from 0 to 15 mg l−1. Results show that the optimized performances of the proposed sensor occur when the bending radius is fixed at 1.5 cm. At this bending radius, the sensor illustrates the sensitivity of − 0.0024 (mg/l)−1 with linearity of 0.97 and resolution of − 4.17 mg l−1. For comparison, the bent sensor is compared to the straight sensor and performances of the former is found to be more superior. In addition, the balloon-like bent sensor is further tested with real water samples. The sensor sensitivity is found to be − 0.0022 (mg/l)−1 with linearity of 0.95 and resolution of − 4.54 mg l−1. The result shows that the sensor has comparable performance in the ammonia detection for both pure ammonia and real water samples. In essence, this balloon-like bent sensor functions without additional coating on the sensor head, making it favorable in terms of the simplicity of the design.