Research On The Methods Of Several Optical Millimeter-wave Generation

The radio-over-fiber (ROF) system, which has many outstanding capabilities,such as low penalty, broad-band, high-capacities and seamless transmission and so on,will be a perfect technology in the future broadband wireless access services, and ithas been a research hot spot in optical fiber communication.At home and abroad, ROFcommunication technology has attracted wide attention and made some effort.Opticalmm-wave generation is one of the key technology in ROF system. In thisthesis,several schemes of mm-wave generation and transmission are proposed and Theresults obtained are as follows:(1) In order to increase the transmission distance for optical millimeter waveover optical fiber, a novel scheme for optical millimeter (mm)-wave generation withoptical carrier suppression(OCS) modulation by external modulator in aradio-over-fiber (ROF) system was proposed. At the central station, a CW lightwavewas intensity modulated by the RF signal to generate OCS signal. After the pureoptical carrier was filtered, an optical interleaver was employed to separate thespectrum of the upper sideband and the lower sideband of the generated OCS signal.After the lower sideband signal was modulated with a baseband data at2.5Gbit/s, itwas recombined with the unmodulated signal to generate optical mm-wave, and thentransmitted to the base station over single mode fiber(SMF). In the base station, theelectrical mm-wave signal was generated by optical electrical(O/E) conversion. Thedispersion performance of the generated mm-wave is theoretically analysed。Theoptical millimeter wave can be transmitted40km over single mode fiber byexperiment. The simulation and experiment results ahow that it can immune thefading effect and increase the transmission distance for optical millimeter wave overfiber by this method.(2) We have numerically and experimentally investigated a radio over fibersystem to generate optical millimeter wave with four time frequency of the localoscillator frequency using two-cascaded intensity modulators based on optical carriersuppression scheme. In the central office,the upstream data is mixed with the RFclock to generate a electrical signal, and then a external modulator is used to generatea optical millimeter with double freqnency of RF clock, after the second externalmodulator, the optical millimeter wave was generated with frequency Quadruple.By this scheme, a40GHz millimeter wave was generated with2.5Gbit/s signal with only10GHz clock source. After transmission over SMF20km, the power penality is lessthan2dB.