Optical fiber sensor based on helical Fibers: A review

In recent years, optical fiber sensors based on helical fibers have attracted more and more interest and have developed into various sensors used in many practical applications. This review focuses on introducing the sensing principles, measurement methods, and sensing characteristics of different kinds of helical optical fiber sensors. These Sensors can be classified into three categories from the perspective of their sensing principles, namely, helical fiber sensors based on mode coupling, interference, and circular birefringence. Finally, we compared the research results with outstanding sensing characteristics in recent years and we pointed out the future development direction of helical structure optical fiber sensors. This work shows that the helical structure has a wide range of applications in fiber gratings, all-fiber interference devices, and all-fiber polarization control devices, and it will contribute great value to scientific research and industrial applications.