摘要
随着各种数据业务对传输带宽需求的不断增长,如何利用现有的光纤传输系统,进一步提高通信容量,满足日益膨胀的需求,已成为光通信领域研究的热点。当前光传送网中波分复用( WDM)技术主要在光纤的C-波段(1530～1565 nm)使用。随着L-波段掺铒光纤放大器( EDFA) 的日趋成熟,将WDM 系统由传统的C-波段延伸到L-波段(1570～1610nm) 已经是大势所趋。与此同时,可用作L-波段通信用光源的光纤激光器也逐渐成为研究热点。
本文提出了一种波长调谐范围达41nm(1569 nm 到1610nm)的L-波段可调谐环形腔掺铒光纤激光器设计方案。波长选择部分由偏振控制器和偏极器构成,其理论依据是光的偏振特性以及单模光纤中的双折射效应。通过调整环形腔内偏振控制器, 改变腔内不同波长的偏振态以获得可变波长输出。通过选择高浓度的掺铒光纤,使用环形光学谐振腔结构并采用二次泵浦技术大大缩小了结构尺寸,提高了光源的稳定性和输出特性。高双折射光纤的引入,能够极大的压缩线宽,3dB 线宽≤0.12nm,在1590nm 的斜率效率为0.246, 波长稳定性优于0.02nm,边模抑制比≥45dB,最大输出光功率为17mW。以上指标均优于迄今国内有文献报到的同类结果。
It has been over two decades since the first experiment of fibercommunication was operated in 1978. Fiber-optic communicationtechnologies have been put into commerce step by step. The speed offiber-optic communication has been growing from 45Mbits/s to 40Gbit/s.How to use the exiting communication system to widen the communicationcapability to meet increasingly demands has have become the hotspot ofthe optical communication realm research, when all kinds of data servicesrequire more and more transmission bandwidth. The current WavelengthDivision Multiplexing(WDM) applications and systems mainly useconventional wavelength band(1530-1565nm). As the erbium-doped fiberamplifier(EDFA) is gradually mature,WDM system from C-band toL-band(1570-1610nm) is necessary trend. Meanwhile, L-bandcommunication transmitter has also become research hotspot.
Under this background , the author develops a tunable L-bandErbium-doped fiber ring laser instructed by Processor Guo Yubin duringthe postgraduate study. The tunable bandwidth of the fiber laser is from1569nm to 1610nm, covered the whole L-band. Using high density EDFAcan shorten the fiber availably, contracted the structure size consumedly,raise the stability and output characteristic of the light source. Highperformance erbium-doped fiber laser which has bright applied foregroundare acquired by the way of choosing reasonable parameters, such ascoupling ratio of output coupler and optimizing the structure of theresonance cavity. Literature search shows that there are not achievementsand research in this area is in vogue. Consequently, this thesis will unfoldthe study focus on this point, in the expectation of offering the theory andexperiment reference for the methods of L-band fiber laser.
Firstly, the thesis introduced the creation principle of the laser and the
basic structure and the work principle of the fiber-optic laser machines.Pump laser, gain medium and optical resonance cavity as three componentsof fiber lasers are analyzed theoretically in details, especially inerbium-doped fiber laser.
Secondly, the thesis detailedly introduced the develop process oftunable L-band Erbium-doped fiber ring laser. Pump source chooses980nm semiconductor laser. In order that amplified spontaneous emission(ASE) move to L-band, we adopt high density erbium-doped fiber(11m+1.8m), ring cavity structure and second pump technology. Mostpopular schemes of tunable filter are summarized and compared, such asFabry-Perot interferometer filter, thin file interferometer filter, tunablefiber grating and so on. A feasible wavelength selection mechanism isformed by the combination of a polarization controller and a polarizer isdemonstrated. The theoretical basis is polirization characteristic of the lightand birefraction in single mode fiber. When line polirization lights frompolarimeter transmit in cavity, their polirizaton state will be change.Polirization direction of some line polarization light is not consistent withthe polirization direction of line polorization by adjusting polirizationcontroller. Its loss is least and it is easiest to form laser. By this way,wavelength is tunable. By importing an high birefraction polirization fibercan improve birefraction effort. After transporting one loop, it can makethe polirization direction of different light different greater and loss is most.Therefore, it can reduse the mode compete and compress lineband oflaser .This equipment has four strongpoint, simple structure, low insertionloss , wide tunable range and low cost .
Finally, on the basis of theoretical design, the apparatus andcomponents for the experiment were actively prepared and set up.Debugged the experiment and measured the main technological indexes.The main technological indexes of the scheme test and verification
引文
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