Abstract: A kind of hollow-core negative curvature fiber (HC-NCF) with polarization filtering and polarization maintaining characteristics is designed, and its characteristics are analyzed. By introducing an inner cladding ring to break the symmetry of the conventional negative curvature fiber, the fundamental mode and the inner cladding glass mode in two orthogonal directions are coupled, which increases the birefringence and loss ratio in the two polarization directions. Then the influence factors of fiber birefringence characteristics and loss are analyzed, including the wall thickness, the inner diameter of the inner cladding tube, and the core diameter. The results show that when the fiber core diameter and the inner diameter of the outer cladding tube ring are 30 m, the wall thickness of the outer cladding and inner cladding tube ring are 1.116 m and 1.56 m, respectively, and the inner diameter of the inner cladding tube ring is 9 m, the birefringence at 1.55 m reaches 1:33 × 10−4, the polarization extinction ratio in the x polarization and y polarization directions of the fundamental mode reaches 4723 (36.7 dB), and the bandwidth with polarization extinction ratio greater than 100 is 7 nm. In addition, the minimum loss at 1.55 m is as low as 0.03 dB/m. It is shown that this kind of polarization maintaining negative curvature fiber can be used in fiber devices that are sensitive to polarization.

Key words: physical optics, negative curvature fibers, birefringence, confinement loss, polarization filter