Optimal Intelligent Design And Implement Of Erbium-doped Fiber Amplifier

The research and application of erbium-doped fiber amplifier improved the development of Optical communication. EDFA is extensively used in DWDM optical communication system and Community Antenna Television (CATV) system. EDFA amplifies the optical signals directly, without the optical-electric-optical switch and has the advantages such as high output power, high amplification gain, broad-band spectrum and low noise figure. EDFA's amplification performance has no relation to system's bit-rate and data format and has been one of important components in modern optical communication system.Nowadays, there are many types of EDFA in application. They mainly are classified as two types by their functionality, traditional EDFA and intelligent EDFA. In traditional research of EDFA, the AGC technology which changes the pump parameters by the output optical signal's power to adapt the amplifier's gain has been researched mostly and well-developed. However, AGC can't select the optimized parameters according to input optical signal and could not satisfy the requirement of different applications. EDFA's auto-adaptive technology means the EDFA has certain intellectual ability and could change its working parameters according to the outside environment (input and output optical signals'power) to optimize its performance in different applications. The adaptive technology which has been researched includes adapting the erbium-doped fiber's length and applying double-stage pump amplification technology. In the former technology, the erbium-doped fiber's length changes according to different input optical signal and the erbium-doped fiber has not been reused. So it needs many erbium-doped fibers, has complex structure and is very expensive. The latter technology uses double-stage pump and is difficult to be auto-adaptive to different applications.Based on the research of erbium-doped fiber, this thesis improves the traditional EDFA's disadvantages and introduces an optimized intellectual scheme of erbium-doped fiber. The critical technology of this EDFA connects certain erbium-doped fiber with same length or different length by certain 1×2 switches. Combined with the adjust of the pump power, the EDFA can controls the 1×2 switches according to different input optical signal to get the optimum erbium-doped fiber's length. So it can get the desired gain and output optical signal's power. In the experiments, we optimize the erbium-doped fiber's length and pump power according to the input optical signal'power and design the optimum parameters of the EDFA. The experiments demonstrate that the EDFA proposed in this thesis have good performance and can auto-adapt to the pre-amplifier, line amplifier and power amplifier. Further more, it brings the advantages of simple structure and performance-price ratio. This kind of EDFA can not only be used in optical CATV system, but also be used in DWDM optical communication system.The first chapter introduces different amplifiers in the optical communication field thoroughly. For emphasis, the development history of EDFA and the research results of EDFA in recent years have been introduced. Besides, the chapter describes the background of optical amplifier and the application advantages of erbium-doped fiber in optical communication system.The second chapter illustrates the theory fundamental of EDFA. The theory model and parameters related to performance of EDFA are analyzed in details. The optical amplification principles of EDFA and performance figures are described and different theory model of EDFA in existence are listed. The Saleh model and Giles model are especially researched because of their extensive application. These theories are the basic fundamental of the EDFA research field.The third chapter introduces the new EDFA's design scheme and proposes the specific implementation scheme. The critical technology of this EDFA connects certain erbium-doped fiber with same length or different length by certain 1×2 switches. Combined with the adjust of the bump power, the EDFA can controls the 1×2 switches according to different input optical signal to get the optimum erbium-doped fiber's length. So it can get the desired gain and output optical signal's power. In the optimization of intellectual EDFA, the EDFA's gain, noise figure and gain spectrum are the optimizing parameters.The forth chapter introduces the design of EDFA's driver, including software and hardware design. Software and hardware design are critical technologies of EDFA. The design gives circuit and software implementation ways of temperature auto-control and power auto-control. The design's main goal is to monitor the EDFA's working status and adjust the bump power, erbium-doped fiber's length and input attenuation according to different input optical power. In the experiment, the EDFA is implemented in gain-stable and power-stable control models. The auto-control circuits of Pump temperature and power guarantee the stability of EDFA is the basis of EDFA's intellectuality and makes the EDFA accommodate to different applications.The fifth chapter gives a review about the whole thesis.