The Research Of Several Key Technology In Fiber And Wireless Combination

Due to the wide bandwidth of fiber communication and the flexibility of mobile access, seamless integration of wired and wireless technology has attracted extensive national and international attention and research interests. Making full use of fiber communication and high frequency radio transmission, RoFtechnology, transmitting the radio-frequency(RF) signals via the fiber, has the capability to realize RF-signal wired transmission and ultra-widebandwidth access with advantages of small signal interference, high-capacity and low overall cost.In this thesis, based on traditional RoF systems, in-depth study was conducted for multi-frequency millimeter waves(MF-MMWs) enabled RoF schemes. Compared with traditional RoF systems, MF-MMWs RoF schemes are not only capable of providing different MMWs at different frequencies for various base stations, but also offering different MMWs for different users or services in the same base station, thus MF-MMWs RoF systems are capable of supporting more users and services and have the capability to satisfy users’ particular needs. The generation of MF-MMWs,the construction design of RoF systems,the approaches of employing RoF technologies in access network are key issues to realize FM-MMWs RoF systems. In this thesis, in-depth studies are carried out to settle the aforementioned three issues, and three FM-MMWs generation schemes and the corresponding adaptive RoF systems have been proposed: a bidirectional RoF-PON system with MZM and SOA enabled scalable generation of MF-MMWs, a RoF-PON with scalable generation of MF-MMWs enabled by polarization multiplexed FWM in SOA, a RoF-PON system with tunable optical frequency comb(TOFC) enabled scalable MF-MMWs generation. In addition to aforementioned work, the application of RoF technologies to cloud radio access network(C-RAN) has also been investigated, and a wired/wireless-integrated C-RAN system was then proposed, which is capable of providing wired/wireless-aggregated multi-services. The originality and innovative work are summarized as follows:1. Based on MZM-SOA enabled MF-MMWs signal generation technology, a bidirectional passive Ro F system has been proposed. The SOA enabled four-wave mixing effect(FWM) and MZM enabled multiple frequency components signal generation have been theoretically analyzed and discussed. Via FWM, MZM-generated multiple frequency components signal and pump signal are used to obtain the multiple optical carriers, and through beating the two optical carriers, the millimeter waves with their frequencies around 60 GHz can be generated. A complete full-duplex RoF system is experimentally constructed, in which the downstream pump light is reused for upstream communication, and millimeter wave generated via beating process is employed as the radio frequency source at base station. Aforementioned design simplifies the base station construction and then reduces cost. The results of downstream and upstream communication experiments verify the feasibility of the proposed RoF system with MZM and SOA enabled MMWs generation. Experiments have also been undertaken to investigate the SOA gain saturation properties and the effect of optical components power difference of the SOA input signal on FWM.2. A novel wired/wireless-integrated RoF-PON system has been proposed based on the polarization multiplexed FWM effect in a SOA, which is used to generate multiple optical frequency components for wired/wireless data modulation. Using the beating process, MF-MMWs can be obtained with their frequencies located at 60 GHz region. One or more MMWs generated by the beating process can be allocated for the userson-demand. In this scheme, the wired access can also be provided to satisfy the users’ wired communication requirements. To significantly improve system performance, the effect of different parameters on polarization multiplexed FWM effect has been investigated, and the results indicate that system optimal performance can be obtained in the case of SOA input electric current falling into 300~400 m A and optical power difference between the optical signal and pump light within 12~14 dB. Through extensive simulations, the results successfully verified the feasibility of our proposed scheme.3. TOFC enabled MF-MMWs scalable generation has been proposed, anda novel wired/wireless access integrated RoF-PON system has been then designed. The TOFC is constructed by cascading a phase modulator(PM) and two intensity modulators(IMs). With proper selection of the peak-to-peak voltage of PM, a flat and effective optical comb with 39 frequency lines and each adjacent two lines at 2GHz frequency gap can be obtained. The MF-MMWs can be generated by beating the optical comb line pairs with frequency interval at about 60 GHz. Compared with other MF-MMWs generation schemes, the TOFC based scheme have advantages of system performance stability and high level of controllability for frequency gap size between every adjacent lines. Thus it enables the base station and network to improve flexibility and scalability. The feasibility of the proposed wired/wireless access integrated RoF-PON scheme is confirmed by extensive simulations.4. The influences of two different data modulation methods have been theoretically analyzed and demonstrated in a RoF-PON system. The first modulation method is the case that all optical lines of the generated optical comb signal are employed to carry the wireless data, while in the second method, only half of the optical comb frequency lines are modulated. Through the simulations, the results indicates that the second modulation method can improve the system performance, regardless of the increased overall cost.5. A RoF technology-based access network system with multi-service wired/wireless integration is proposed. In the system center station, several optical frequency lines are generated and modulated by wired, RF, WiFi, and WiMAX signals, respectively. After arriving at base station, the RF signal-modulated optical frequency lines are beating with each other while the optical frequency lines, modulated by wired, WiFi, and WiMAX signals, are demodulated directly. Thus, the multi-service integration can be achieved in a base station.