title: Detailed theoretical investigation of bending properties in solid-core photonic bandgap fibers.
abstract: In this paper, detailed properties of bent solid-core photonic bandgap fibers (SC-PBGFs) are investigated. We propose an approximate equivalent straight waveguide (ESW) formulation for photonic bandgap (PBG) edges, which is convenient to see qualitatively which radiation (centripetal or centrifugal radiation) mainly occurs and the impact of bend losses for an operating wavelength. In particular, we show that cladding modes induced by bending cause several complete or incomplete leaky mode couplings with the core mode and the resultant loss peaks. Moreover, we show that the field distributions of the cladding modes are characterized by three distinct types for blue-edge, mid-gap, and red-edge wavelengths in the PBG, which is explained by considering the cladding Bloch states or resonant conditions without bending. Next, we investigate the structural dependence of the bend losses. In particular, we demonstrate the bend-loss dependence on the number of the cladding rings. Finally, by investigating the impacts of the order of PBG and the core structure on the bend losses, we discuss a tight-bending structure.
authors.affiliation: Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan. murao@icp.ist.hokudai.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Murao
authors.forename: Kunimasa
authors.initials: K
authors.lastname: Saitoh
authors.forename: Masanori
authors.initials: M
authors.lastname: Koshiba
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical