Advances in Cryogenic Temperature Sensing Using Fiber Bragg Grating: A Review

Cryogenic temperature sensing is crucial across multiple sectors where monitoring and controlling extremely low temperatures are essential. At such low temperatures, the behavior of materials and electronic components changes significantly, making accurate temperature measurement a complex challenge. Because of its various advantages over its counterparts, fiber Bragg grating (FBG) is a potential device for cryogenic temperature monitoring. This article reviews the advances in cryogenic temperature sensing using FBG. The main limitation of bare FBG-based cryogenic temperature sensing is that the thermal expansion coefficient (TEC) of silica material on which FBGs are usually fabricated is significantly lower, especially at cryogenic temperatures. This review shows that such sensors’ packaging requirements and sensitivity enhancement can be achieved by coating FBGs with suitable materials. We have reviewed all the research papers available to date on the cryogenic sensitivity enhancement of FBG sensors by coating them with metals, polymers, or composites. A comprehensive analysis of metals coated on FBG, their sensitivity, and their deposition method is given in this article. Different composite or polymer-coated FBG sensors are compared based on their sensitivity and coating method. Coating FBGs with metals or polymers that exhibit more significant thermal expansion can improve their sensing performance. A comparison of metal- and polymer-coated FBG sensors based on sensitivity, mechanical strength, long-term stability, cost, and cryogenic performance shows that the metal-coated FBG has potential for further research. A comparison of different metal coating techniques is also discussed in this article, and it is identified that electrodeposition outperforms other techniques for coating the FBG.