The Generation And Optical Fiber Transmission Performance Evaluation Of Optical Mm-wave Signal

Radio-over-Fiber(RoF)technique is the integrated optical and wireless access system.Ituses fiber as RF signal transmission medium and makes full use of advantages of optical fibercommunication and radio frequency communication，such as large capacity，low loss，effectively resisting the electromagnetic interference， flexible and efficient.So RoFtechnique can effectively solve the demand of bandwidth，capacity and transmission distancefor future broadband wireless communication.The technology of optical mm-wave signalgeneration is one of the key technologies to realize ROF communication.In this paper，westudy main about the generation and transmission of optical mm-wave signal,mainlyincluding two aspects:one is the analysis summary of the existing optical mm-wave signalgeneration method, two is to put forward improved optical mm-wave signal generationmethod.The first aspect includes the following parts. First，we introduce optical mm-wave signalgeneration method such as direct modulation technology，external modulation technology，optical heterodyning modulation technology，and calculate the spectrum of optical mm-wavesignal generated by external modulation technology.Second，we illustrate that three differentspectral structures can be generated by modulator with different configurations，includingdouble side band(DSB)structure， single side band(SSB)structure and optical carriersuppress(OCS) structure. We analyze transmission performance of these three structures ofoptical mm-wave signal through simulation in Optisystem7.0.Results show that in opticalfiber transmission，DSB structure has power ups and downs decline and SSB structure andOCS structure has code element narrowing effect.The second aspect is that we propose the improved extemal modulation technology.First，lightwave，which comes from continuous laser，is modulated by local oscillator signal toobtain optical mm-wave of SSB or OCS structure.The optical mm-wave comprises twofrequeney components. Then，one frequeney component carries baseband signal while theother is blank，to overcome power ups and downs decline and time shift of the sidebandswhich always exist in conventional generation schemes. Two improved external modulationsehemes，including SSB structure optical mm-wave with signal only on optical carrier，OCSstructure optical mm-wave with signal only on one sideband are demonstrated. And the twoschemes are analyzed in theory and simulation. Results show that，compared with the formergeneration schemes，under the same conditions，the optical mm-wave signal generated byimproved extemal modulation technology can effectively restrain the influence of fiberdispersion in optical fiber transmission，has no time shift of the sideband and improves theBER performance of the system.