Fiber Bragg Grating Temperature Sensor and its Interrogation Techniques

In this comprehensive review, our focus centers novel strategies and methodologies in FBG temperature sensors and their interrogation techniques investigated for sensing in different environments. FBG temperature sensors are investigated for cryogenic, ambient, high-temperature and ultrahigh-temperature environments. Interrogation techniques encompasses optical interferometry, optical edge filtering, time division multiplexing, optical spectrum analysis (OSA) and wavelength division multiplexing (WDM), each possessing distinct characteristics and working principles. The optical interferometry technique offers exceptional sensitivity and high resolution but has a relatively lower temperature sensing range. The optical edge filtering technique provides good temperature sensitivity, enhanced resolution and nominal temperature sensing range which are mainly dependent on the span and slope of the edge of the optical filter. TDM interrogation technique has the multiplexing capability and cost-effectiveness but limitations like the requirement of partial reflective matched FBGs, spatial separ¬¬¬¬ation of the FBGs and the potential cross-talk make it less attractive for commercial applications. OSA and WDM techniques excel in multiplexing capabilities and boast the widest temperature sensing range. However, OSA is limited for research applications only. On the other hand, WDM stands out with its cost-effective per-sensor implementation and extensive usage in commercial interrogation systems. The significance of this review lies in its ability to provide researchers, engineers, and practitioners with a coherent understanding of the evolving FBG temperature sensing landscape. By consolidating and highlighting recent breakthroughs, we aim to inspire further research initiatives and foster the development of optimized FBG temperature sensing systems.