A type of centered porous-defected polarization maintaining photonic crystal fiber

In standard fiber transmission systems,imperfections in the core-cladding interface introduce random birefringence that leads to light being randomly polarized.These problems with random birefringence in polarization maintaining(PM)fibers are overcome by deliberately introducing a larger uniform birefringence throughout the fiber.Current PM fibers realized by standard fiber technology include PNDA or bow-tie fibers,which achieve this goal by applying stress on the core region of a standard fiber.A modal birefringence up to 5×10-4 may be readily obtained.However,this kind of fibers is so sensitive to the change of environment that the stability of systems can be seriously affected.In the other hand,PM photonic crystal fibers(PCFs)with asymmetric core designs,which offer resistance to the change of environment,may be used to introduce modal birefringence at least one order of magnitude larger than that for conventional PM fibers.This paper studies the relationship between the arranging shape and size parameters of air holes in total internal reflection(TIR)PCF and the birefringence.A kind of single-mode two-hole center-defected PCF with a birefringence of 3.4×10-3 is designed through structure optimization.Meanwhile,numerical empirical equation for this kind of PCF is achieved by the method of multi-variant nonlinear regress fitting,which may offer theoretical reference for the manufacture of PM-PCF in future.