【作者】 邢亮；

【导师】 夏宇兴； 詹黎；

【作者基本信息】 上海交通大学 ， 光学， 2008， 博士

【摘要】 光纤中控制光的传播速度甚至将光“停”下来,在全光通讯和光信息处理中具有重要意义。目前的光纤通信系统中,存在着较多的光-电、电-光转换过程,给光纤通信系统带来诸多不利因素。为了充分利用光纤通讯的带宽优势,人们一直梦想着能够实现全光通信技术。缺少实用的光路由器是全光通信发展的一个瓶颈。而其关键部件全光缓存器尚没有实用的技术途径。实现光缓存的办法之一就是——用光学的手段来控制光速。这就是研究光纤中的快慢光技术的目的——研制一种全光存储器或是高精度的光学可控延迟线,以解决全光通讯中光交换/光路由的问题。此外,快慢光现象的研究还可以应用在光信息处理和光存储等方面。本文对光纤中光速减慢技术(“慢光”技术),特别是基于受激布里渊放大的慢光技术进行了理论和实验上的研究。本文首次提出了一种可以增强布里渊慢光缓存器延迟性能的高功率布里渊放大器。泵浦和信号的功率之比如果越高会带来更高增益,而信号的延迟时间同增益成正比,所以也会带来好的延迟性能。高功率布里渊放大器利用较短的光纤长度提高了布里渊阈值,从而增加了可用的泵浦功率,所以可以提高泵浦和信号的功率比。由于增益饱和是布里渊慢光缓存器性能的主要限制之一,本文着重研究了这一特征参数。同时还测量了其延迟性能,噪声指数等特征。此外,还分析了高功率布里渊放大器的性能对其慢光缓存器应用的影响。结果表明,对输入功率-36dBm的信号,相对于低功率布里渊放大器,通过使用高功率布里渊放大器,延迟时间可以增强超过24ns。本文对布里渊慢光进行了深入的理论分析,推导了基于布里渊放大的慢光缓存器的存储能力的公式,并通过数值模拟给出了其最大能存储的比特数及获得最佳存储比特数的相应的比特率。首次从物理机理上解释了目前所有的基于SBS的慢光实验其延迟量都没有超过1个比特的原因。全光缓存器的宽带应用是发展趋势。通过调制泵浦增加泵谱光谱宽度可以实现宽带布里渊放大。我们针对宽带布里渊慢光缓存器在不同泵浦带宽(或增益带宽)的情形进行了详细的理论分析。结果表明,对RZ码,其存储能力局限在1.2比特左右。此结果是窄带情形的2倍多。本文还研究了基于光纤环形共振腔的慢光现象,详细分析了其各种特性。着重分析了其振幅损耗系数对系统延迟和色散性能的影响。结果表明,环内有增益时,且与振幅耦合比乘积为1时会出现延迟和色散突变等新现象。更多还原

【Abstract】 It is a significant technique to control the speed of light in an optical fiber for the information processing and the all optical communication systems. In the present communication systems, optic-electric convertions are needed in many places, which will bring unfavorable factors to the systems, such as increase the system complexity and reduce the signal quality. Such system is not fit for high speed application. To address the problem, men have been dreaming of the coming of all-optical communication for many years.Tunable optical buffers (TOB) are key components in future all-optical routers (AOR). The lack of feasible AOR is a well-known bottleneck of developing all-optical communication network. To realize the TOB, one needs to optically control the group velocity of light. Investigation of slow-light technique aims at realizing controllable optical delay or optical buffer with high precision. In addition, slow light technique can also be applied to information processing and optical storage.We have studied the slow-light technique, in particular the slow-light technique that based on stimulated Brillouin amplification both theoretically and experimentally.We first proposed and demonstrated a controllable optical buffer based on a high power Brillouin amplifier. An experimental investigation is performed of the characteristics, gain, gain saturation and noise figure (NF) of a high-power fiber Brillouin amplifier (FBA) for the requirement of slow-light buffer application. Among these features, gain saturation is highlighted because it is a fundamental limitation for FBA based slow-light buffer. An analysis on how the performance of the high power FBA affects FBA based buffer is presented. The results show that for a -30dBm input signal, up to around 20ns delay enhancement can be obtained by using high-power FBA.Up to now, in all experiments of SBS slow light, no public reports have evidently shown that the delay time exceeded one bit period. The physics origin of this limitation has not been clarified. We, taking into account pulse broadening, proposed a detailed analysis on the buffer ability of slow-light buffers based on the FBA. Our analysis shows that for continuous wave (CW) or quasi-CW pump the maximum storage bits is dominated by the available net gain, which is limited by both the saturation gain and pulse broadening for bit streams in optical communication systems. We show the real storage capacity of SBS based slow light buffer is around one bit (0.5 for RZ data and 1 for NRZ data) for CW or quasi-CW pump. Detailed analysis shows that for pulse sequence with given peak power, the optimum data bit rate to achieve the best storage capacity can be obtained by using our method.Broadband application of all-optical buffers is a developing trend for high speed communication requirements. The storage performance of broadband Brillouin slow-light buffer is still unknown until now. We propose a theoretical analysis of broadband tunable Brillouin slow light with variable pump bandwidth. It is shown that the storage capacity is around 1.2 bit for data of RZ code. The value is twice as we obtained in the narrow band amplification case.In addition, we studied the slow light based on resonator. We investigated several important characteristics of the resonator, in particular the delay and dispersion performance with a high amplitude loss coefficient. It is shown that delay and dispersion will mutate when the product of amplitude loss coefficient and amplitude coupled ratio is around 1.更多还原