Trends and Applications of U-Shaped Fiber Optic Sensors: A Review

Intrinsic U-shaped fiber optic sensors (FOSs) are well established in the field. With greater penetration depth and evanescent power, these sensors exhibit profound sensitivity and have supported a wide range of applications. Several sensing mechanisms have been integrated with U-shaped FOSs for physical, chemical, bio, and refractive index (RI) sensing applications. Sensor performance optimization is based on the principles of the associated sensing mechanisms. This paper is the second part of a review on U-shaped FOSs and discusses the sensing mechanisms, applications, possible improvements, and future scope of the U-shaped FOSs. Besides, this paper aims to provide researchers with a general idea of the actual implementation of U-shaped FOSs based on the theoretical model discussed in Part I of this review.