Study On Key Techniques Of Intelligent EDFA

Erbium doped fiber amplifier (EDFA) is one of key components used in fiber-optic communication systems, and its performance is closely related to the communication capacity and quality of fiber-optic networks. When utilized in different of situations, EDFA can serve as the line amplifier, power amplifier and pre-amplifier, and thereby the requirements of the performance are different. Intelligent EDFA is the EDFA that can adjust its internal parameters according to external work conditions to meet different performance requirements. In this thesis, several key techniques of intelligent EDFA are investigated, and a novel intelligent EDFA structure is proposed and numerically demonstrated.In Chapter one, the background of EDFA is introduced. The characteristics of similar fiber-based amplifiers are enumerated. The development and the advantages of EDFA are summarized in detail. The current development directions are analyzed. Then the contents of this thesis are described.In Chapter two, the theory of intelligent EDFA is discussed. Different requirements on performance of EDFA are broughtened by network applications. In order to control the parameters in EDFA design, it is important to choose the theory model that fits practical application, and Gile's model is the perfect one. With this model, the performance of EDFA can be obtained for different structures with different parameters through numerical solution. The relations between structural parameters and performance states are the theoretical foundation of the novel intelligent EDFA proposed in this thesis.In Chapter three, a novel intelligent EDFA is proposed and investigated. The gain, noise figure and gain spectrum are the main parameters in optimizing in the design of intelligent EDFA. Simulation shows that, for a given input, there is an optimal length for Erbium doped fiber. Similar results are made by the simulation of the power of pump. Based on these results, we proposed a novel intelligent EDFA structure. After judging the type of input signal, the intelligent EDFA's optimal performance is achieved according to three methods, i.e. adjusting the variable optical attenuator to control input signal power, adjusting the ratio of pump power between the first and second stage, and choosing different length of second stage erbium doped fiber of EDFA. The simulation results show that the intelligent EDFA with this structure has steady and smooth output character within large input dynamic range.In Chapter four, the techniques of intelligent EDFA's circuit and software are studied. The control of hardware and software is another key technique of intelligent EDFA. It is necessary for the control software to carry out the monitoring of work status of EDFA and the adjusting of pump power, length of Erbium doped fiber, and attenuation amount. The working modes include constant current, constant power, constant gain, and constant output. The circuits for automatic control of pump temperature and power are the guarantee of steady work of intelligent EDFA.