Experimental and Theoretical Investigations of Bending Loss and Birefringence in Embedded-Core Hollow Fiber

The bending loss and birefringence in an embedded-core hollow fiber are investigated numerically and experimentally. The bending losses of the fiber for two polarized lights are measured for different bending orientations and bending radii. Both the simulated and measured results show that the bending loss of the embedded-core hollow fiber has a strong directional dependence. The bending loss is larger and more sensitive to bending radius when the fiber is bent toward the core direction. In the opposite bending direction, the fiber has the antibending capacity. Because the core of the fiber sample is a nonstrict elliptical, a critical orientation angle exists during the bending of the optical fiber. Away from the critical angle, the bending losses are not sensitive to the bending orientation regardless of antibending direction or bending sensitive direction. The group birefringence of the optical fiber is also measured.