【作者】 郭昌建；

【导师】 何赛灵；

【作者基本信息】 浙江大学 ， 光通信技术， 2011， 博士

【摘要】 随着信息技术的发展以及各种新型业务的出现,用户对接入带宽以及数据安全性的要求越来越高。光码分多址(OCDMA)技术因其具有的接入协议简单、高安全性、软容量等优点,近年来得到了广泛的研究,在军用、电子商务以及民用接入网等场合均有广阔的应用前景。本论文在基于FBG的全光OCDMA技术以及电域处理OCDMA技术两个方向上,通过理论分析、系统仿真和系统实验等方法,对这两种OCDMA技术的系统和子系统的设计和实现进行了研究。本文在基于FBG的全光OCDMA技术上做了如下研究和创新工作：首先,我们利用非线性偏振旋转效应,提出了一种新型的光阈值器,以消除多用户全光OCDMA系统引起的多用户干扰。我们提出的新型光阈值器具有在整个C波段对波长透明以及不需要定制的带通滤波器等优点。我们应用这种新型的光阈值器,实现了4用户、单用户2.5 Gb/s、传输距离为20 km的相干一维TPC-OCDMA系统。其次,我们提出并实验实现了应用在OCDMA-PON中的一维/二维混合编解码方案。其中二维WHTS-OCDMA链路采用ASE作为光源,采用级联FBG作为编解码器；一维相干TPC-OCDMA链路则采用锁模光纤激光器产生的超短脉冲作为光源,采用码长为127的相移SSFBG作为编解码器。最后,我们通过仿真和实验研究了以系统速率为2.5 Gb/s下设计的相移SSFBG作为编解码器实现的高速(10 Gb/s),长距离(180 km)传输的相干一维TPC-OCDMA系统。仿真和实验的结果均表明,随着速率的升高,系统的接收灵敏度持续下降。在采用工作在2.5 Gb/s的长度为38.1mm,码长为127的相移SSFBG,在速率为10 Gb/s单用户传输180 km时,相对于速率为2.5 Gb/s时,接收灵敏度将下降约6 dB。全光OCDMA系统面临着很严重的拍频噪声和多用户干扰的影响。即使采用光阈值器和光门限等技术,系统能达到的用户数仍然非常受限。因此我们提出并研究了一种基于空间编码和副载波复用的电域处理OCDMA系统,从而消除拍频噪声对系统的影响,并且在理想状态下可以消除多用户干扰。我们首先通过仿真和实验实现了15用户、单用户1 Gb/s、传输20 km的CDM/SCM-PON系统。实验结果表明,在15用户同时存在的情况下,各通道的误码性能均在普通前向纠错编码能够纠错的误码率范围内。接着,我们研究了新型CDM/SCM-PON系统在DSB和SSB调制下色散对信号的影响,并针对上述两种调制下色散的影响,提出了色散补偿的方案,并通过仿真验证了我们提出的两种色散补偿方案的可行性。最后,我们通过仿真研究CDM/SCM-PON系统接收端的关键器件,模拟/数字转换器(ADC)的各项指标,包括带宽、分辨率以及前端裁剪滤波器的裁剪率对系统性能的影响。仿真结果表明,ADC在分辨率为5位以上时,带宽在约0.8倍于信号带宽,裁剪滤波器的裁剪率为3-5时,系统的性能可以达到最优。更多还原

【Abstract】 Due to advances in information technologies and the emerging of various bandwidth consuming services, we are seeing an ever increasing demand for faster and more secure internet connections. Optical code division multiple access (OCDMA) is considered as one of the attractive access technologies in both military and civil applications due to its advantages such as high capacity, simple networking protocol, and the potential of security enhancement for the physical layer. The main topic of this thesis is all optical OCDMA based on FBG en/decoders and electrical processed OCDMA systems and subsystems. Theoretical analysis as well as system simulations and experimentations are carried out.A large part of this work on all optical OCDMA systems and sub-systems based on FBG en/decoders is devoted to experimental demonstration and analysis. First, a novel optical thresholder based on nonlinear polarization rotation is proposed. Our proposed optical thresholder has the advantage of colorless operation over C-band without the utilization of custom-designed band-pass filters, which is crucial in the design of large-scale and cost-effective OCDMA-PON systems. A 4x2.5 Gb/s TPC-OCDMA system based on our proposed optical thresholder is experimentally demonstrated. Then, a hybrid 1D/2D en/decoding architecture is proposed and experimentally demonstrated for the first time. An ASE source is used for 2D WHTS-OCDMA link using cascaded FBG en/decoders, while ultra-short pulses from an mode-locked fiber laser is used as the source for the 1D TPC-OCDMA link with 127-code SSFBG en/decoders. After that, we analyze the performance of 10 Gb/s TPC-OCDMA systems using SSFBGs designed for 2.5 Gb/s applications, as the fabrication process poses a limitation on high-speed (short grating length),long-code SSFBGs. We show through simulation and experimentation that a～6-dB power penalty is expected when using 2.5 Gb/s (38.1 mm) SSFBGs in single user 10 Gb/s, and 180 km TPC-OCDMA systems.All optical OCDMA systems suffer from severe beat noise and multiple access interference (MAI). Additionally, practical deployment of all-optical OCDMA systems typically faces the challenges of high system costs due to the adoption of expensive optical units. To address these problems, we propose a novel CDM/SCM-PON based on spatial coding and subcarrier multiplexing, with code division multiplexing in electrical domain. We first demonstrate a 15×1 Gb/s CDM/SCM-PON with 20 km of standard single mode fiber transmission, through both simulation and experimentation. We show that error free operation assuming forward error correction (FEC) can be achieved when 15 simultaneous users are present. We then address the chromatic dispersion induced signal distortion for both DSB and SSB modulated CDM/SCM-PON systems, using electrical post chromatic dispersion compensation for SSB modulated systems, and electrical chromatic dispersion pre-compensation for DSB modulated systems. Both proposed schemes have been verified using VP1 and matlab co-simulation. In our last work, we analyzed the ADC impact on CDM/SCM-PON systems. Through system simulation we find that the system performance can be optimized using an ADC with at least 5-bits resolution, with a bandwidth of around 0.8 times signal bandwidth, and with a clipping ratio of around 3-5.更多还原