Bending characteristics of a long-period fiber grating in a hollow eccentric optical fiber

In this paper, the bending characteristics of a long-period fiber grating (LPFG) in a hollow eccentric optical fiber (HEOF) have been investigated. Two samples fabricated under different laser exposure directions have been studied experimentally. The results show that the HEOF-LPFG can distinguish specific bending directions. The resonant peak shifts linearly with increasing curvature, but its sensitivity is lower than that of the LPFGs in single-mode fibers. In addition, the exposure direction shows a great influence on the bending characteristics due to the asymmetry of the fiber core. Furthermore, the responses of the HEOF-LPFG to temperature, axial strain, and external refractive index have been measured.