Hollow-core photonic bandgap fiber, birefringence, bending

Calculate the modes of the fiber before and after bending using wave optics in COMSOL software, and convert the fiber bending using conformal formula. Extract two polarization fundamental modes from the fiber mode, with the difference being the fiber birefringence. The difference in birefringence under different bending states of optical fibers is called the birefringence change. The birefringence of Panda fiber is measured using white light interferometry, and the distance between the two interference peaks at 1550nm is calculated. Then, the birefringence of the fiber is calculated using the birefringence calculation formula. In the document, 7cell and 19cell represent birefringence under different optical fibers, and the secondary folder represents birefringence under different wall thicknesses, including birefringence under different bending directions and bending radii. In each document, lam refers to the working wavelength, RE (neff) refers to the real part of the effective mode refractive index, Cl refers to the fiber confinement loss, and B/BIr refers to the fiber birefringence. RR refers to the bending radius