A review: Salinity and temperature measurement based on optical fiber sensors

The study of optical fiber salinity and temperature sensors is essential for enhancing precise environmental monitoring and ensuring the sustainability of ecosystems. Sensor performance is closely linked to their structure, which significantly influences sensitivity and stability. Factors such as transmission mode type, sensing material selection, and structural design all affect the sensor's detection sensitivity and stability. Based on sensitivity to salinity and temperature, optical fiber sensors are classified as intrinsic and extrinsic sensors. This review provides a comprehensive analysis of the structural design, operational principles, and performance characteristics of both intrinsic and extrinsic sensors, focusing on the application and potential of various materials and structures in optical fiber sensor design. It explores how emerging materials, including polyimide and hydrogels, can enhance the sensitivity, accuracy, and stability of sensors, and examines the advantages and performance of single-mode and multimode transmission, such as photonic crystal fibers, hollow-core fibers, and microfibers, in specific applications. The review aims to inspire the use of advanced materials and innovative structures in designing new optical fiber sensors, thereby further improving their performance and application prospects.