随着移动通信、大数据、云服务等的快速发展和应用，无线网络的数据量和服务的多样化需求激增，未来第五代移动通信(5G)系统将为移动用户提供高达Gbps量级的传输带宽，载波频率也向着更高的微波频段发展。光载射频(RoF)以其独特的技术优势，成为解决未来5G移动通信系统中，高频载波低损耗长距离传输和低成本蜂窝密集覆盖的关键技术。由于FTTx的发展和广泛应用，将RoF技术与FTTx结合，既可大幅度提高RoF系统的性能、为移动用户提供高效覆盖，又能充分利用FTTx网络中的光纤资源、大幅度降低系统的施工和运维成本，更符合未来多样化网络的发展趋势，对未来5G系统、尤其是向更高频段通信的推进，具有重要的科学意义和实用价值。 本论文在充分调研国内外研究现状的基础上，对RoF系统的未来应用、特别是在未来5G系统应用中的若干关键科学和技术问题，进行了深入地理论、技术和实验研究，具体完成的创新性工作如下。 (1)在高频RoF系统实验中发现，受温度等周围环境因素的影响，系统接收信号的眼图存在“张开—变小—闭合—再张开”的循环现象，导致系统无法正常工作：从理论上分析了高频RF信号在光纤中传输时存在这种相位漂移特性的原因；提出了一种基于载波恢复技术克服相位漂移现象的系统实现方案，通过实验验证了系统的有效性。 (2)提出了一种CS-SCS-BS的RoF系统结构及WDM-RoF全双工通信实现技术；搭建了载波频率为10GHz的全双工RoF实验系统，验证了系统的功能。该结构与技术具有抗色散和抗相位漂移特性，提高了RoF系统的性能，解决了RoF系统与FTTx网络的兼容问题；采用中心站集中配发上行光载波的方式，基站无需本地光源，节省了基站成本、降低了实现复杂性，从而大幅度降低了未来5G网络建设的成本。 (3)提出了一种基于CS-SCS-BS的TWDM-RoF技术方案，搭建了载波频率为26-GHz的TWDM-RoF实验系统，以1.25Gbps数据速率和40㎞标准单模光纤传输系统为例，验证了技术方案的有效性。该方案可降低基站内上行光载波和下行数据的分离成本，提高单波长的频谱效率；通过次级中心站内加入光交叉单元，实现对上、下行载波资源的灵活配置，从而提高了系统效率、降低了能耗。 (4)设计研制了一种可用于5G承载网的多速率自适应光收发机和实时误码性能监测模块。光收发机自适应速率工作范围：100Mbps～10.709Gbps，体积小、成本低、功耗低；误码监测模块，可实现10Mbps～11.3Gbps之间任意速率数据的误码测试，与现有昂贵的误码仪设备(安立MP1800A)测试结果对比发现，具有较好的一致性，该模块亦可置入光网元如OLT、ONU和OADM等设备中，实现误码性能的实时在线监测，具有广阔的应用前景。 关键词：光载无线通信；相位传输特性；波分复用；时分-波分复用；自适应光收发机；误码检测仪

 With the rapid development and application of mobile communications, big data and cloud services, the demand for data and diversified services of wireless networks is increasing dramatically. The transmission bandwidth for subscribers will reach the Gbps level in the future fifth-generation (5G) mobile communications system, as well as the carrier frequency will move toward a higher microwave bands. Radio-over-fiber (RoF) technology has become a key technology to realize low loss long-distance transmission of high-frequency carriers and effective coverage of denser cellular with low costs owing to its unique advantages. In view of the rapid development and wide application of the fiber to the X (FTTx) access network, it can not only significantly improve the performance of RoF systems for an efficient coverage by combining the RoF technology with the FTTx network, but also can make full use of the existing fiber resources for a further reduction of the system construction cost, maintenance and operation cost, which is more consistent with the development trend of future diversified network and of great scientific significance and practical value for the promotion of future 5G systems, especially for the high-band communications. On the basis of the adequate investigation of the present status of the national and international research, this dissertation has carried out a detailed theoretical, technical and experimental investigation of several key scientific and technical issues for the application of RoF systems, especially in future 5G communications system. The main innovative contributions of this dissertation are listed as follows. (1)In the experiment of the high-frequency RoF system, it is found that the eye diagram of the recovered signal at the receiver terminal has a cyclic phenomenon of "opening decreasing-closing-reopening" due to influence of ambient factors such as the temperature, which causes the system unable to work properly. The reason for this phase-shift characteristics of the high-band radio frequency (RF) signal transmission through an optical fiber is theoretically analyzed. A system implementation scheme by means of the carrier recovery technique is proposed and verified experimentally to solve the phase-shift phenomenon. (2)A RoF system structure of central station (CS)-subcentral station (SCS)-base station (BS), and a full-duplex WDM-RoF communication technique are proposed. A 10-GHz full-duplex RoF experimental system is established to verify the performance of this system. The proposed technique and structure can improve the system performance against the chromatic dispersion and phase-shift characteristics, and realize an effective compatibility between the RoF system and the FTTx network. Structure of base station without local light sources is achieved by the centralized allocation of the upstream optical carriers, which leads a reduction of the cost and complexity of base stations. Thus the cost of future 5G network construction can be greatly reduced. (3)A TWDM-RoF technique on the basis of CS-SCS-BS structure is proposed. A 26-GHz TWDM-RoF experimental system with data rate at 1.25Gbps over a 40-㎞ standard single mode optical fiber, as an example, is established to verify the validity of this technical scheme. In this scheme, the separation cost of the upstream optical carrier and downstream signal at each base station can be reduced as well as a higher spectrum utilization of single wavelength. By the additional optical cross-connect unit at the SCS, flexible configuration of downstream and upstream carrier resources can be realized, which improves the system efficiency and reduces energy consumption. (4)An adaptive multi-rates optical transceiver and a real-time bit error rate tester (BERT) module for 5G bearer network are designed and developed. The adaptive optical transceiver with small size, low cost and low power consumption can operates form 100Mbps～ 10.709Gbps. The BERT module can realize the bit error test at any rate between 10Mbps and 11Gbps. Compared with the existing expensive BERT (Anritsu, MP1800A), the error detection results of this BERT module are consistent. It can also be placed into the OLT, ONU and OADM to implement a real-time monitoring of BER performance, which has a wide application prospect. Key Words: Radio-over-Fiber Communications; Phase Transmission Characteristics; WDM; TWDM; Adaptive Optical Transceiver; BERT