Design And Characteristic Analysis Of Compressed High Birefringent Photonic Crystal Fiber

Photonic crystal fiber has a wide range of applications in the fields of communication and sensing because of its characteristics of non cut-off single mode,flexible controllable dispersion,high birefringence and high non linearity.The design of photonic crystal fiber is no longer limited to the strict periodic structure.Researchers try new structures and introduce doping materials to obtain better characteristics and higher application value.The design and analysis of compressed birefringent photonic crystal fiber are studied in this paper.Firstly,the theoretical basis of the finite element method and how to simulate the mode field distribution,birefringence,dispersion,limited loss,effective mode field area and nonlinear coefficient are simulated by using the full vector finite element method in the design of photonic crystal fiber.Then a compressed circular air hole photonic crystal fiber is proposed.By introducing two small circular air holes in its core area to obtain birefringence,the high birefringence single mode transmission of the photonic crystal fiber is realized with the aid of asymmetric structure.The full vector finite element method combined with perfectly matched layer absorbing boundary condition is used to numerically analyze the transmission characteristics of the photonic crystal fiber.The results show that the mode birefringence generated by the photonic crystal fiber in the 1400-1700nm wavelength range is up to 10^-22 orders of magnitude,which is about two orders of magnitude higher than that of the conventional polarization maintaining fiber.At the same time,the peak of birefringence can be adjusted to the required wavelength by adjusting the size of the aperture flexibly.The numerical analysis of the loss characteristics of the basic mode of the photonic crystal fiber is influenced by its structural parameters.It is obtained that the photonic crystal fiber can produce a limited loss of less than 0.01dB/km in the range of 1400-1700nm wavelength.Finally,the compressed circular air hole photonic crystal fiber model is further optimized,and the two small circular holes of the core are changed to ellipse.By adjusting the structural parameters of the optical fiber,the birefringence and other transmission characteristics are studied,so that the transmission characteristics of the fiber change in a large wavelength range.Under certain structural parameters,high birefringence,low loss,high nonlinearity and zero dispersion can be obtained.A series of models with different structural parameters are established for analysis and comparison,and some appropriate design parameters are given.The results show that the birefringence of photonic crystal fiber can reach 2.02*10^-2.