Study On Design Structure And Characteristics Of Photonic Quasi-Crystal Fiber

With the development of mobile networks,the application of optical fibers has also increased.The development of modern optical fiber technology has brought tremendous progress to optical communications.Photonic quasi-crystal fiber?PQF?,as a new type of microstructured fiber,has attracted extensive attention due to its excellent characteristics.Such as high birefringence,controllable dispersion and so on.It also has important applications in many optical fields.Experiments have shown that changing the structure of photonic quasi-crystal fibers can cause the optical characteristics of the fiber to change.By adjusting the changes of these parameters,the required optical characteristics can be achieved.In this paper,we briefly analyze the influence of different structures on optical properties.Three new types of PQF structures are proposed.We analyze the effect of each parameter on the optical characteristics by using the finite element method combined with perfectly matched layer boundary conditions.Starting with four types of PQF structures,they are six-fold,eight-fold,ten-fold,and twelve-fold PQF structures.The nonlinear characteristics and birefringence characteristics of the four structures are mainly analyzed.The simulation results shown that the nonlinear coefficients of these structures are almost the same.Therefore,we further analyze the nonlinear coefficients of the ten-fold PQF structure.Change the size of the air holes with different turns of the ten-fold PQF,and analyze the influence of each circle of air holes on the nonlinear coefficient.It is shown that changes in the air holes at the core will have a significant effect on nonlinear coefficients.The radius of the air hole closest to the core changes by 0.1?m,and the effect on the nonlinearity exceeds 100W^-1km^-1.At the same time,the distance between the air holes will also cause the change of the nonlinear coefficient.The birefringence characteristics of these four structures have obvious differences,which are different from the nonlinear characteristics.When the axis of abscissa and ordinate is used as the line of symmetry,the six-fold and eight-fold structures are obviously asymmetric.This is also the main reason why the birefringence of these two structures is higher than that of the other two structures.This proves that it is possible to improve the birefringence of the structure by destroying the symmetry of the structure.According to the above rules,three new PQF structures were designed.The single-ellipse structure fiber is a new type of fiber that combines high birefringence and high nonlinear coefficient.Based on the eight-fold PQF structure,a single ellipse structure is added at the core.The single ellipse of the core not only effectively destroys the symmetry of the original structure and improves the birefringence,but also makes the hole spacing of the fiber core dense,enhancing the nonlinear coefficient.The optimized parameter structure finally obtained has high birefringence high nonlinear.The new high-birefringence PQF is an optical fiber structure with two elliptical air holes at the core.The two elliptical air holes at the core effectively break the symmetry of the structure.The effective refractive index difference between the two fundamental modes of x,y is increased,and the birefringence value is increased.The optimized structure can obtain higher birefringence than other structural fibers,and the loss does not exceed 10^-2d B/m.This novel structure has great potential in high-performance optical devices.The new PQF is a bow-tie structure with high nonlinear PQF with near zero dispersion.Reduce the air holes on both sides on the basis of the six-fold PQF structure.Adopt two sizes of air holes to form a bow tie,and add two circular air holes at the core.It is shown that the two air holes in the fiber core not only improve the birefringence,but also increase the nonlinear coefficient.The highly nonlinear PQF with near zero dispersion isobtained with low confinement loss.This kind of optical fiber can have practical application value in the generation of supercontinuum.And on this basis,the structure also obtains high birefringence and low loss.