Research On High Birefringence Of Photonic Crystal Fiber And Multi-core Coupling Characteristics Of Photonic Quasi-crystal Fiber

The successful development and application of Pohotonic Crystal Fiber?PCF?has caused a great sensation in the field of optical communication.A variety of structures and properties of photonic crystal fiber have emerged and are widely used in making excellent optical de-vices.Optimizing and designing photonic crystal fibers with higher performance has become the focus of attention in the field of optical communication.Compared with traditional opti-cal fiber,photonic crystal fiber has excellent characteristics,such as endlessly single-mode,extremely low loss,high nonlinear coefficient,flexible dispersion.Moreover,due to the flexibility of structural design,photonic crystal fibers have become the focus of fiber re-search.In this paper,a photonic crystal fiber and a quasi-photonic crystal fiber with high birefringence based on finite element theory and a seven-core quasi-photonic crystal fiber based on coupled mode theory are proposed.This thesis mainly includes three aspects of works:First,a photonic crystal fiber based on micro-hole core structure was studied.It intro-duced 7 sets of nano-scale micro-hole structures in the core of the fiber.When the diameter D of the micro-hole and the hole spacing H between the holes are increased,the birefrin-gence of the fiber is increased.However,increasing or decreasing the spacing between the microhole groups and the group has little effect on the birefringence of the photonic crystal fiber.Secondly,by arranging the positions of the air holes around the core,a dodecagonal high birefringence quasi-photonic crystal fiber is designed.The core is surrounded by the air holes of the inner layer to form an elliptical shape in the y-axis direction.It is found that its birefringence coefficient can reach 10^-2in the communication window 1.31 and 1.55?m.Compared with the photonic crystal fiber of elliptical air hole of the same magnitude,the structure is simple and easy to be made in the laboratory.Finally,a six-fold symmetric multi-core quasi-photonic crystal fiber is designed.Its core is a seven-core core consisting of six non-adjacent air holes that remove the middlemost and third layers of the cladding.Through simulation studies,it is found that the structure has a short coupling length,and the coupling length is shortened by reducing the hole pitch,duty ratio,core refractive index,and core diameter.