Study On Automatic Gain Control Of Erbium-Doped Fiber Amplifiers

The invention of Erbium-Doped Fiber Amplifier (EDFA) brought an evolution in optical communication.With the advantages of high gain and output power,low noise, wide bandwidth as well as no relation with polarization,EDFA changes the traditional optical-electrical-optical relay mode step by step in many fields,and becomes an indispensable device in modern optical communication systems.It saves the expensive cost in optical-electrical transition,makes equipment easy to operate and maintain. With the updating of WDM system and development of optical transition network,Gain-Clamped Erbium-Doped Fiber Amplifier fixes the problem of gain fluctuation and vibrating when input power and upload channel numbers are changing.The thesis studies and designs the automatic gain control of Erbium-doped Fiber Amplifier. Researched on the several methods of automatic gain control of Erbium-doped Fiber Amplifier, the thesis designs a new method of automatic gain control circuit based on the erbium-doped fiber amplifier design, the design programmes mainly based on linear Tabular and Lookup Table Calculating control mechanisms with a combination to achieve the automatic gain control of erbium-doped fiber amplifier.Firstly, the history and actuality of the EDFA and its prospect in practical applications is introduced.Then the thesis designs a new method of automatic gain control circuit based on the erbium-doped fiber amplifier. Secondly, the reasons that why to choose the hardware of MCU, pump lasers, optical attenuator, temperature sensors and A/D, D/A are descripted. Pump laser driver circuit, the light detection circuit, Optical attenuator of the drive circuit, temperature sensors and A/D, D/A of the interface circuit carried out a detailed analysis and design, and point out that the related problems should be pay attention while designning. Then, The concept of linear interpolation algorithm was introduced, and linear interpolation algorithm is applied to the pump Laser and optical attenuator control of the pump laser and optical attenuator control mechanism using look-up table, and reject a relatively long time compared consumption of computing mechanisms, so as to achieve the erbium-doped fiber amplifier operating speed advantages. Erbium-doped fiber amplifier based on the automatic gain contro includes pump laser control module, photoelectric detector modules, optical attenuator modules, input or output optical power control module, module temperature detection and eye-module.Then, the cycle of the system and the system flow chart are given. As when the temperature changes, optical attenuator will take place in control of drift, the paper also designed a light attenuation accuracy of the attenuator control procedures, described in detail the procedures to achieve its way. Finally in the laboratory to test the system, the test results were analyzed and compared.Linear interpolation and the look-up table control mechanism are introduced to the AGC-Erbium-doped fiber amplifier design which is a feature of this paper. Linear interpolation and look-up table control mechanism can significantly improve the pace of work of EDFA, it will certainly be widely used.Laboratory test results show that the design of the erbium-doped fiber amplifier can be accurate and reliable optical signal to achieve the automatic gain control, the established objectives and requirements are realized.