Bending Loss Analysis Of Eccentric Core Optical Fibers

As as one of the basic components of various optical devices, fiber has been widely used in the technology of sensor, laser and high-speed optical communication systems. At the same time, advances of new technologies has greatly promoted the development of optical fiber area which leads to the emergence of a variety of special optical fibers, including the Eccentric-Core Fiber. the fiber core has a deviation from the center, forming an asymmetric structure, also the fiber core is more close to the cladding boundary than traditional ones, so its optical transmission characteristics is extremely different. Currently, this kind of fiber has been applied in many fields such as fiber optic attenuator, interference refractive index sensors and lasers.The main research of this thesis is as follows:First, we analyze the background and significance of the subject, and study the development of fiber optic sensor and bending loss in china and abroad. Then predict the advantages of Eccentric-Core Fiber in all-optical integrated devices and optical fiber sensing area in the future. at last we chose this subject.Second, basis theory of fiber optical transmission is elaborated, including the ray optics and wave optics theory. the equivalent refractive index method to bending fibers is described; also introduce several numerical simulation methods to the characteristics of fiber optic transmission, compare them and choose BPM methods at last.Thirdly, we establish a theoretical model to calculate Eccentric-Core Fiber according to the traditional theory of fiber optic transmission theory. by solving the characteristic equation of the general three-fiber waveguide and using of the conformal transformations in electromagnetic field,we get the propagation constants. Then we apply the traditional bending loss theory to Eccentric-Core Fiber.finally, we get the value of bending loss in the fiber.Finally, use Beam PROP in Rsoft to construct a system of Eccentric-Core Fiber, including the structure, the light source, optical monitors and other parameters. observed the attenuation at different bend radius. And by changing the eccentric distance,the strength of bending loss can be predicted. By comparing to the former analysis, we get the conclusion finally.