The advent of optical fiber communications brought a revolution for the entire field of communication. With it’s own characteristics so that high-speed, large-capacity communication is possible. Currently, it has become an irreplaceable and the most important technology for information transmission. In this context, research and analysis of the structure and optical fiber transmission characteristics has an important significance on further development and application of the optical fiber. This paper firstly summarizes the development and future development trends of the technology of optical fiber and its characteristics, advantages. Followed by the key theory of the diploma project ——fluctuations in optical theory, and the simulation software –MATLAB. Then expounded the structure and transmission principle of the fiber material, and focus on the analysis and description of the characteristics of the transmission of step-fiber .Using the wave optical theory, derives the characteristic equation of the optical transmission in theory. Solving its scalar solution, and expatiates the definition and classification of those modes. Finally use MATLAB to map the diagram of the electric field’s strength in several modes of Step-scalar mode fiber.
