Research on Radio-on-Fiber Access Systems Eliminating Electric Power Supply at Base Station

本研究的目的是为了实现高效、高性能的光纤无线接入系统，消除天线基站的电源，并对其实用化进行研究。首先，我们尝试提高光调制器和光电二极管的转换效率。在本工作中，应用三短节阻抗匹配，光调制器和光电二极管的转换效率分别提高到2.5d B和4.0d B。另一方面，为了提高光电转换的效率，从理论上阐明了利用稀土金属制成的荧光材料的波长转换技术可以将最大转换效率提高50%左右。其次，为了提高光调制器的转换效率，提出了一种基于ROF接入系统的外差技术消除天线基站供电的新方案。在下行传输的情况下，在中心站使用双级联光调制器，将2.45 GHz的电信号下变频到0.45 GHz，基站侧的传输性能比传统方案提高了7.5dB。在上行传输的情况下，为了实现ROF系统不需要基站供电，我们提出了上行传输方案，该方案将接收到的2.45 GHz射频信号与中心站发送的光信号产生的本地信号混合，向下转换为0.45 GHz。与传统方案相比，该方案的传输性能提高了约8.0d B。

The purpose of this research is to realize high effectiveness and performance Radio-on-Fiber (ROF) access system eliminating electric power supply at antenna base station and to study for practical use of it.At first, we tried to improve the conversion efficiencies of optical modulator and photo-diode, which are indispensable elements to ROF system. In this work, applying to three-stub impedance matching, the conversion efficiencies of optical modulator and photo-diode were improved to 2.5 dB and 4.0 dB, respectively. On the other hand, to improve the efficiency of optical-to-electrical conversion, it was theoretically clarified that the maximum efficiency of about 50 % was improved by using the wavelength conversion technique of the fluorescent material, which was made from rare-earth metal.Next, in order to improve the conversion efficiency of optical modulator, we proposed a novel scheme using heterodyne technique based on ROF access system eliminating electric power supply at antenna base station. In the case of down-link transmission, using dual cascaded optical modulator at center station, the electrical signal at 2.45 GHz is down-converted into 0.45 GHz, and then, the transmission performance of 7.5 dB was improved at base station side, compared to conventional scheme. In the case of up-link transmission, to realize ROF system eliminating electric power supply at base station, we proposed up-link transmission scheme, which down-converts into 0.45 GHz by mixing 2.45 GHz received RF signal and local signal, which is generated by the optical signal delivered from the central station. In this scheme, the transmission performance of about 8.0 dB was improved in comparison with conventional scheme.