摘要
本论文主要研究了以掺铒光纤为增益介质的光纤超荧光光源及其光谱的增益平坦技术。设计研制的高平坦度C+L波段掺铒光纤超荧光光源适用于分布式光纤光栅传感系统、长距离光纤通信系统以及光纤陀螺和光纤无源器件测试等领域。本文的分析研究对高平坦度的ASE光源的设计和制作具有一定的指导意义。
首先对研制掺铒光源所用的掺铒光纤、泵浦激光二极管以及主要光电器件的工作原理和特性作了详细的介绍。对掺铒光纤超荧光光源的特性、基本原理、结构和数学模型作了系统地描述。在介绍C波段和L波段ASE光源的基础上,对C+L波段ASE光源进行了深入的研究。通过对单级单程、单级双程和双级双程结构的C+L波段ASE光源的实验研究和分析,设计了三级双泵浦结构的C+L波段ASE光源。此光源与前面几种结构的C+L波段ASE光源相比,具有更优的性能指标,尤其是输出光谱的平坦度,在不加任何滤波器的情况下,60nm(1543~1603nm)波段范围内光谱的不平坦度<±1.3dB,由于1532nm波长附近的波峰存在,在80nm(1523~1603nm)波段范围内光谱的不平坦度>±3dB。
然后,针对ASE光源输出光谱的不平坦性,介绍了几种典型的光谱平坦技术方法,其中重点介绍了外部均衡法,即使用增益均衡滤波器实现光谱的高平坦度。研究的滤波器包括:马赫-曾德尔干涉仪型滤波器、长周期光栅(LPFG)以及基于光纤环形镜结构的增益平坦滤波器。对各个滤波器进行了详尽的理论与实验研究,然后总结各自的优缺点。其中,根据设计的光源输出光谱的特点,通过理论计算,利用特制的长周期光栅实现了在80nm(1525~1605nm)波段范围内,输出的C+L波段光谱平坦度<±0.66dB,输出功率较加入LPG之前减小了1.05dB,是较为理想的一种平坦方法。
结合实验室承担的科研项目,分析了分布式光纤光栅传感检测系统对掺铒光纤超荧光光源性能的要求。将优化设计的光源应用于分布式光纤光栅传感系统中,通过实验证明:使用高平坦度的ASE光源不但可以增加分布式光纤光栅传感系统中的传感器数量,而且有利于FBG传感信号的远距离传输和解调。
最后,结合论文中的研究情况指出了论文的不足之处,并根据现在国内外的研究现状对掺杂光纤光源相关领域的未来研究方向进行了展望。
The super-fluorescent fiber source (SFS) and the gain flattening technique are studied in this paper. The high flattening fiber soure produced can be applied in the distributed FBG sensing system, the long optical fiber communication systems, fiber optic gyroscope, and so on. The studies of the paper are useful for the design of the high flattening erbium-doped super-fluorescent fiber source.
First, the article gives a detailed introduction about the erbium-doped fiber, the pumping source as well as the main optoelectronic devices, which compose the SFS. Then, systematically describes parameters、fundamental structures and mathematical model about erbium-doped fiber super-fluorescent source. Based on the studies of the C band and L band ASE, the C+L band ASE is lucubrated. By studying the C+L band ASE of single-stage single-pass, single-stage double-pass and dual-stage double-pass structure, a high flatness C+L band ASE is presented using the three-stage erbium fiber and two pump LDs of 980 nm structure. The flatness of the spectra from 1543nm to 1603nm is less than±1.3dB without using any external spectral filters. But the the flatness of the spectra from 1523nm to 1603nm is more than±3dB, because there is a peak near by 1532nm.
The typical spectra of erbium-doped fiber source is not a flat spectra containing a high-intensity region and a flat part spectra. In order to make the spectra flat, some gain flatten techniques are introduced. Thereinto, research focus is the gain flatten filter. The filter studies include cascaded Mach-Zehnder Interferometer (MZI) based gain flattening filter, long period fiber gratings (LPFG) and fiber loop mirror. Analyse their working principles theoretically, test their effects by the experiments, and contrast their characteristics. Based on the spectra of designed fiber source, the transmission spectrua of the LPFG can be computed. By utilizing the LPFG built according to the computing result, the flatness of the spectra from 1525nm to 1605nm is less than±0.66dB, the output power is 1.05 dB samller than before. So it is better than others.
According to the project of our laboratory, the performance of fiber source used in distributed FBG sensing system is analysed. The optimized C+L band ASE is applied in the distributed FBG sensing system, experiment results indicate that the high flatness ASE not only extends the bandwidth for large number of sensor, but also is beneficial to accurate demodulation.
Finally, the shortages of the study are listed, which definitize the targets and the problems to be solved in the future study.
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