【作者】 殷杰；

【导师】 林金桐；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 急速增长的网络带宽需求和更加便利的接入条件是光载无线技术研究和应用的两个重要推动力。一方面随着越来越多无线业务的引入,尽管人们使用了更高频谱利用效率的调制格式,可用的低频段无线频率资源仍然在日渐减少,为了提供更高带宽的业务,研究人员逐渐把目光转向毫米波等更高频段应用；另一方面,随着光接入网的快速发展,光纤接入显示出可用频谱宽、单位带宽成本低、结构简单、可靠等优点。但与无线接入相比,光纤接入具有布线成本高,使用不够灵活等缺点。通过在光纤中传输射频信号,研究既能利用光纤巨大带宽,又能发挥无线通信灵活方便等优势的光载无线技术得到了世界范围内的广泛关注。本论文主要针对宽带无线接入网络和高速无线应用需求,依托国家863计划和国家自然科学基金等多个国家级项目,重点开展超宽带信号ROF系统设计与应用方面的研究。论文主要工作如下：采用双入双出新型铌酸锂调制器设计了一种能同时在光域产生monocycle和doublet型UWB(超宽带)脉冲的方法,信号带宽符合FCC(美国联邦通信委员会)标准。只需要两个不同波长的激光器和两个调制器(一个双入双出调制器和一个普通的马赫-泽德调制器)就能实现PSM(脉冲形状调制),比现有已报道的PSM实现结构大大简化。采用铌酸锂相位调制器设计了两种新型的ROF系统。第一种方案利用一个光相位调制器和一个马赫-泽德调制器设计了一种光倍频技术实现20GHz/40GHz毫米波段频率分集的微波信号产生。由于光相位调制器不需要直流偏置,不会遇到直流偏置漂移问题。在经过光相位调制器之后,输出光信号的包络保持不变,能被基站用来承载强度调制的上行信号。经过调制产生了两个频段的射频信号,具有抗频率选择性衰落的优点。第二种方案使用两个相位调制器和一个马赫-泽德调制器,设计实现了30GHz毫米波频段二相键控(BPSK)信号的产生和传输。信号两个边带分成两路分别由两个相位调制器用相反数据进行调制。两个相位调制器的驱动信号幅度可减小一半,便可获得和用一个相位调制器方案相同的调制效果。由于使用低放大倍数、低饱和功率输出的稳定驱动,从而提高了系统的可靠性。对基于外差探测的ROF系统进行了深入研究并实现了吉比特无压缩高清电视业务传输演示。理论分析并实验验证了在基站端使用大功率激光器外差DPSK格式光信号,并在终端使用移位相乘结构进行射频信号下变频和解调的实验方案,该方案具有很好的色散的容忍性和低于-30dBm的接收机灵敏度。此外还设计实现了基于2.5Gb／s光相位信号调制、外差探测和无线偏振分集发射、高灵敏度接收的光载无线系统。基于上述外差ROF系统,国内首次实现了1.3Gbit／s无压缩高清电视信号@15-32GHz大于20公里光纤传输,大于5米无线传输的业务演示,图像质量流畅,误码率达到10-9以下。论文最后提出了EPON(以太网无源光网络)与60G ROF系统融合的超宽带有线无线混合接入设计方案。该方案在同一链路中同时传输有线及无线业务,通过采用多天线技术克服了毫米波视距传输的不足。针对不同的应用环境,设计了星型和树型网络拓扑结构下的智能网关,该网关能实现下行毫米波无线信号的分发和上行数据的汇聚。更多还原

【Abstract】 The rapid increase of network bandwidth demand and more convenient access environment are two driving forces for radio over fiber research and development. On one hand, although high bandwidth efficiency modulation formats are available, with the emergence of a lot of new wireless services, the remained wireless resource becomes much scarcer. In order to supply high bit-rate services, researchers gradually turned to higher frequency such as millimeter waveband. On the other hand, with the optical access network’s high speed growth, optical access demonstrates its advantages of broad bandwidth, low devices cost, simple and reliable structure. However, compared with wireless access, the wired access network has the disadvantages of high installation cost, inflexible access to mobile users. Under this background, the research of radio over fiber which combines both advantages of wireless access and wired access is attracting attentions both from academia and industry all over the world. This issue which transmits wireless signals in the fiber, called radio-over-fiber, has a lot of key problems to be solved. In this dissertation, several design issues of ROF systems have been intensively investigated for broadband wireless access applications under the sponsorship of national 863 programs and national natural science foundation in China.The main works of this dissertation are summarized as follows:1. Firstly, a novel approach of the UWB monocycle and doublet pulses generation based on dual-in dual-out LiNbO3 modulator is proposed, whose spectrum matches the FCC standard. Employing two lasers of different wavelengths and two modulators, the pulse shape modulation can be achieved, which is simpler than the existed proposals.2. Secondly, two novel ROF system schemes based on the LiNbO3 phase modulator are accomplished. Employing one MZM(Mach-Zenhder modulator) and one PM(phase modulator), the scheme of generating frequency-diversity binary phase shift keying(BPSK) millimeter wave signals at 20GHz/40GHz with the frequency multiplication technique is completed. The optical phase modulator does not suffer from the bias drifting problem as it does not need DC bias. The envelope of output optical signal after the phase modulator keeps stable and the optical signal can be used to carry uplink data back to the base-station. The system can generate two frequencies, which will decrease frequency selective fading effect. The second scheme generates binary phase shift keying(BPSK) millimeter wave signals at 30GHz. Two sidebands are filtered into two paths and are modulated by two phase modulators with complementary data. To obtain the same effect of using one phase modulator, the amplitude of the drivers on the two phase modulators can decrease to half of that in one phase modulator scheme. Thus, more stable amplifiers of lower magnification can be used to increase the system’s reliability.3. Thirdly, the intensive research of Radio-over-Fiber system and the demonstration of HDTV service application based on heterodyne detection are completed, which includes theoretical analysis and experiments. In the experiment, the optical signal carrying DPSK information is coupled with the high power laser at the base station and the RF signal is demodulated by the delaying-multiplying structure at the terminal. The scheme has high dispersion tolerance and excellent receiver sensitivity of better than 10-30dBm. The second scheme of 2.5Gb/s optical PSK signals transmission and ASK wireless signals generation with 15GHz carrier based on heterodyne detection is demonstrated, which can realize polarization diversity and has excellent receiver sensitivity. Based on that ROF testbed, the first domestic demonstration of 1.3Gb/s uncompressed HDTV service is achieved with more than 20km wired(single mode fiber) and 5m wireless transmission. The video stream is smooth and fluent for the low bit-error-rate (<10-9).4. Finally, the scheme of the broad bandwidth wired and wireless hybrid access network with the integration of EPON and 60G ROF system is proposed. The wired and wireless signals are transmitted in one optical link. Through employment of the multi-antenna technology, the drawback of millimeter waveband signal’s straight line radiation can be overcome. For different applications environment, an intelligent gateways including star and tree topologies are designed, which can achieve the distribution of wireless down link stream and the convergence of the uplink data.更多还原