Enhanced Surface Plasmon Resonance (SPR) Fiber Optic Sensor for Environmental Monitoring: A Coreless Fiber–Based Design

The present work represents the fabrication of a CF-MZI fiber sensor to develop an optical sensor leveraging surface plasmon resonance (SPR), in order to measure the component concentrations in the surrounding environment. In this sensor structure, a coreless optical fiber (NCF) covered with a layer of gold nanoparticles was used, which significantly improved the sensing performance. The interferometer structure can be formed by joining two segments of the standard multi-mode optical fiber (MMF) to the two ends of 2-cm coreless fiber via fusion splicing. The obtained results showed high sensitivity in the experimental tests. The sensitivity to the concentration changes was measured at − 68 nm/C% for single-layer sensing and 55.35 nm/C% for dual-layer sensing. The customized design enables real-time monitoring and improves the detection of environmental variables, and it is characterized by its simplicity and compact structure. The proposed sensor is versatile and suitable for various sensing applications beyond environmental analysis.