Research On The Technology Of Optical Millimeter-wave Transmit Based On OFDM

With the rapid development of communication,the fourth generation mobile system (4G),which has the ability to provide a wide range of omnipresent real-time multimedia services with high quality and wide bandwidth,will be a milestone in the history of telecommunication industry.The Radio-Over-Fiber (ROF) system, a technology for delivering wireless signals over the optical fiber,which brings together the agility of wireless access and huge capability and low cost of fiber,has been expected to be a promising technology to apply to 4G networking. Orthogonal frequency division multiplexing (OFDM) technology,featuring robust anti-interference capability,high spectral efficiency and large transmission volume,has been publicly regarded as a kernel technology of 4G systems. Therefore,both OFDM and ROF is becoming a hot spot of the 4G's study.In the thesis,the techniques of mm-wave generation using single-sideband modulation technique in ROF system are mainly discussed. A novel scheme to generate optical millimeter-wave (mm-wave) signals by using single-sideband (SSB) modulation technique was proposed and experimentally demonstrated. Odd order sidebands were suppressed by proper adjusting the dc bias of signal-arm intensity external modulator in central office. One of the second order sideband was filtered out and SSB modulation was realized. Also the effect on downstream transmission in radio-over-fiber (ROF) system of optical carrier-to-sideband ratio (CSR) was analyzed and the performance of the ROF system can be significantly improved when CSR is 0 dB.Secondly , a novel OFDM-ROF system using single sideband modulation technology in radio-over-fiber system to generate optical millimeter-wave was proposed and experimentally demonstrated. The experiment results show that in 10GHz-ROF system,a 2 Gb/s OFDM signal transmitted over 200km SMF without wireless broadcasting only has 1dB power penalty. After being only transmitted over 8m wireless air distance it has 0.3dB power penalty. When the signal transmitted over both 200km SMF and wireless air distance of 8m,we also can obtain a clear received constellation in our experiment.