| Research Abstract |
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.
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