Research On Optical Millimeter-wave Vector Signal Transmission In Radio Over Fiber System

Electric field process microwave signal more and more difficult with the increase of the communication capacity and improve the communication frequency from microwave to millimeter wave. In addition, the electromagnetic radiation has a big influence on human security. So the traditional electric field process microwave signal has been difficult to meet the development requirements of the new technology. Radio-Over-Fiber (ROF) is a technique to modulate wireless signals on optical wave to transmit wireless signals. It is the physical implementation technology which combines the advantages of wide bandwidth, low loss and immune to EMI of the fiber optical communications and the advantages of access flexibility and mobility of the wireless communications, and has become an ideal solution to solve large capacity, high bandwidth and mobility. Optical millimeter-wave generation is one of the most key techniques of the ROF system. This paper focus on discussing the way to generate the optical millimeter-wave signal, mainly includes two aspects:the first is the analysis of several traditional modulation methods DSB (double-sideband modulation), SSB (signal-sideband modulation) and DSB+CS (carrier suppression DSB) based on LN-MZ modulator, theoretical analysis and computer simulations these modulation schemes. The second is the analysis of the traditional modulation systems transmite vector signal which applys to wireless communication existing phase distortion, and proposes two solutions to solve millimeter-wave vector signal phase distortion. One is with the method of separation subcarrier to modulate data on one sideband and the other sideband with no data, theoretical analysis and computer simulation show that the millimeter-wave vector signal generated by photodiode detection can avoid phase distortion. The other is with filters filter out some sidebands only leaving one sideband with data and one sideband without data to avoid phase distortion. The theory analysis and system simulation prove these two methods have good transmission performance. Simulation results show that these two novel modulation scheme can not only generate optical millimeter-wave signal with frequency quadrupling and frequency quintupling but also modulate vector signals on one sideband with no phase distortion or constellation overlapping on the millimeter-wave signal at the receiver. These two modulation schemes have shown a great potential in the ROF link.