Broad-band Erbium-doped Fiber Amplifier

It has been over two decades since the first experiment of fibercommunication was operated in 1978. Fiber-optic communication technologieshave been put into commerce step by step. The speed of fiber-optic communicationhas been growing from 45Mbits/s to 40Gbit/s. How to use the exitingcommunication system to widen the communication capability to meet increasinglydemands has have become the hotspot of the optical communication realm research,when all kinds of data services require more and more transmission bandwidth. Thecurrent Wavelength Division Multiplexing (WDM) applications and systemsmainly use conventional wavelength band (C-band, 1530-1565nm). As the L-bandErbium-doped fiber amplifier (EDFA) is gradually mature, WDM system fromC-band to L-band (1570-1610nm) is necessary trend. So Broad-bandEDFA(C+L-band) has also become research hotspot.Under this background, the author develops a Broad-band EDFA instructed byProcessor Guo Yubin during the postgraduate study. The gain flatness bandwidth ofthe EDFA can reach 60nm. The C-band and L-band signals are amplified separatelyas using paralleled structure;it can obtain the optimum amplified performance byadjusting respective structure, finally uses WDM to gather the two parts to get anideal broadband output. This paper studied and had carried on the experiment in theexpectation of offering the theory and experiment reference for the methods ofBroad-band EDFA.First, the thesis introduced the basic optical fiber amplifier structures, andcarried out the theoretically analysis on the gain medium——erbium-doped fibercharacteristics, especially on the EDFA's principle of work,amplified performanceand so on.Next, the characteristic of amplified spontaneous emission (ASE) had beenconducted to the research of EDFA and laid a strong emphasis on the ASE curvecharacteristic which pumped under different pump power. We expected atheoretically instruction to the Broad-band EDFA system in using ASE.Finally, we do research on the C-band and L-band in experiment. We used themethod of gain flatness filter in C-band to get flatness output. The max outputpower can reach to 23dBm, gain flatness bandwidth get to 32nm, gain flatness isless than 1dB, noise figure is less than 5.0dB, this kind of structure of C-bandEDFA had already used in production. High efficiency L-band EDFA that based onFiber Bragg Grating (FBG) had been conducted to the experimental study. Byutilizing the FBG with the center wavelength of 1550nm before the input side ofEDF to inject a portion of C-band ASE back into the system, the populationinversion of this EDFA is intensified, which gives rise to gain improvementcompared with the conventional one, the conclusion is peak output power 15dBm,simulation bandwidth 35nm, gain flatness less than 1.5dB;this structure can alsoachieve the automatic gain control (AGC) function and the amplifier gain isclamped at 25dBm with a variation of less than 0.5dB for an input power as high as-15dBm.We also discussed the method and its performance through simulationwhich carried out C-band and L-band function of AGC.In sum, this thesis analyzes the principle, design process, debugging process,output characteristic mensuration of Erbium-doped Fiber Amplifier. I hope thatthese researches could provide worthy theories and the technique support forfurther research and development.