Modeling And Simulation Of Mode-Division Multiplexed Optical Transmission System

With the rapid development of Internet technology, distance education, telemedicine, cloud computing and large data, the transmission rate of system and the capacity of network will show multiple levels growth in the foreseeable future, however the optical transmission system will not satisfy these demands, which just using the conventional dimensions of time, frequency, polarization and multilevel code. So studying and searching for the new dimension has getting more and more attentions. Spatial dimension is considered to be the only one dimension which has not be effectively utilized in the cable transmission. Previous studies show that using the spatial modes can increase the transmission rate, and it also can improve the performance of the network.The ultra high-speed optical fiber communication system will use3M modulation technique in the future, namely multi-level, multi-core and multi-mode modulation. This paper just studied several key points about mode-division multiplexing, including design of few-mode fiber, research of nonlinear coefficients and mode coupling theory. The specific content is about:(1) Designing the weakly coupled few-mode fiber for uncoupled mode-Division multiplexing transmissions. As the important transmission channel for the mode-division multiplexing system, few-mode fiber has all of characteristics of long-distance transmission of single mode fiber and multi-mode of multimode fiber. We designed a weakly coupled four linear polarization modes fiber, which could use the low-complexity MIMO digital processing technology. By comparison, the fiber has these characteristics of high DGDs, low mode coupling, low nonlinearity and low bend loss. (2) Studying the optimization of Kerr nonlinearity coefficients and the control method of mode power. Nonlinear effect has the important implications for optical signal transmission. It is related the structures of few-mode fiber and the incident mode power. So we studied the relationships between Kerr nonlinearity coefficients and the structures of the fiber, and several important methods are obtained for optimizing the Kerr nonlinearity coefficients. And then through considering the impact of incident mode power, we proposed a control method and its related apparatus, which can effectively compensate the mode dependent loss and nonlinear effect.(3) Studying the mode-coupling theory and simulate the three modes multiplexing system. Due to the undesirable characteristics of fiber under practical condition, mode-coupling caused the crosstalk between each mode. We simulated a three modes mode-division multiplexing system, which includes weakly mode-coupling between two non-degenerate modes and strong mode-coupling between two degenerate modes. The system has the right transmission characteristics through analyzing the system performances, and different transmission properties for different modes by analyzing the system performance curves.