Theoretical And Experimental Investigation On Birefringence Of Photonic Crystal Fibers

Photonic Crystal Fiber(PCF) has many attractive characteristics superior to the traditional fiber and the birefringence characteristic is one of its important features. In this paper, the birefringence characteristic has been studied in theory and experment respectively. The main results are summarized as follows:Firstly, two kinds of high birefringennce of single-core PCF are put forward: the first one is squeezed lattice PCF which belongs to the global birefringence. A concept of squeezed ratio(SR) that represents the degree of squeezed lattice is proposed. Based on multi-polar method, the influence on birefringence of SR has been studied; the second one is octagonal PCF of high birefringence which belongs to non-global birefringence. The model field, dispersion, confinement loss, birefringence and beatlength of the fiber fundamental mode and the influence on birefringence of some parameters are simulated by multi-pole method. Lastly by comparing with the hexagon PCF having the same parameters, we can obtain the superiority of the octagonal PCF.Secondly, a dual-core PCF of high birefringence is proposed. The model field, dispersion, birefringence and coupling characteristic of the fiber fundamental mode and the influence on such characteristics of some structural parameters are simulated by multi-pole method. Then a polarization splitter based on three-core PCF is simulated by Improved Full-Vectorial Beam Propagation Method. It is confirmed that at a wavelength of 1 550 nm we can realize separation of the x and the y polarization through a transmission length of 1 500μm.Finally, the parameter of polarization-maintaining fiber called polarization crosstalk is experimentally measured. Two kinds of fiber samples are measured by the novel experimental system designed for measuring the polarization crosstalk. Then we analyze the sources of experimental errors and propose some corresponding solutions for the problems in the experiment.