Hollow-core photonic bandgap fibers: properties and sensing technology

In this paper, the unique properties of the hollow-core photonic bandgap fiber (HC-PBF) are reviewed, and a variety of sensing and device applications of this type of fiber in recent years are introduced. Low-loss light transmission in air core is an important characteristic of the HC-PBF, which provides light-matter interaction channel with high energy density and long interaction distance. In addition, the air-propagation of the light in fiber also reduces the impacts of fiber material properties (such as infrared absorption, thermos-optical effect) on propagating light, hence offers an efficient platform for the sensing applications such as trace gas/liquid detection, optical fiber gyro sensing. The fine micro-structure in HC-PBF exhibits novel mechanical and thermal properties, which would be beneficial to the sensing applications such as sound wave and vibration detection. The HC-PBF's porous structure can also be locally modified by using various post-processing techniques, such as local heat treatment, micromachining and selective filling, which would enable further function extension or performance enhancement. The flexibility of the fiber has been used to develop new optical fiber devices, such as grating, polarizer and polarization interferometer. At present, the development of HC-PBF sensing technology has greatly expanded the sensing ability and application range of optical fiber. It is an important direction for the development of all-optical devices and optical integration technology.