Design And Research On Characteristics Of High Birefringence Photonic Crystal Fiber

With the high-speed development of IT (information technology) and the ever-increasing progress of science and technology, it’s inevitable for people to have a higher requirement for the optical fiber. In recent years, with the coming of photonic crystal fiber, it has, to a great extent, offset the deficiencies and defects observed in the traditional optical fiber. It is also marked by some incomparable advantages, as compared to the traditional one. The photonic crystal fiber is characterized by a lot of optical properties, one of which is the birefringence property, which will be mainly discussed in the paper. The end-face structures of the three kinds of optical fibers are designed using the finite element analysis method. We also calculate the birefringence indexes of the optical fiber using the numerical simulation software, Comsol Multiphysics3.5a, and by adjusting the structure parameters of the optical fiber, a higher birefringence in the optical fiber is obtained.The main works of this paper is as follows:(1) Designed a micro-lattice type high birefringence photonic crystal fiber, which consists of five rows of twin circular air holes in the middle core of the fiber. We found that enlarging the pore size of both big cladding air holes and micro-lattice air holes, which are designated as d2and d3, respectively, can improve the birefringence in optical fibers. At long wavelength band, by reducing the lateral spacing, b, of air holes, fibers can obtain a higher birefringence.(2) Designed an advanced high birefringence photonic crystal fiber through modifying sandwich structure. The design scheme is to remove the four circular air holes near the core of the fiber and meanwhile to introduce four oval-shaped air holes. The research suggested that increasing the ellipticity of four air holes can improve the birefringence of the fiber significantly, from the original10-3to10-2in terms of the order of magnitude.(3) Designed a structurally double-cladded high-birefringence photonic crystal fiber. The design scheme is to remove the seven air holes near the core of the fiber, and then introduces, respectively, four, six and eight orderly-aligned air holes to form three different kinds of double-cladded PCF (photonic crystal fiber) end-face structures. The research indicated that the third double-cladded PCF performed best among three of them, in terms of birefringence, and that by increasing the size of both the inside and outside of cladding air holes, as represented by d1, d2, d3,can improve the birefringence of the fiber. On the contrary, increasing the spacing, L, between the cladding air holes shows no obvious impact on the birefringence of the fiber.