| With the rapid growth of bandwidth requirements in fixed networks and wireless access networks,radio-over-fiber?RoF?technology has attracted more and more attention because of its advantages in system capacity,bandwidth and mobility.Photonic millimeter-wave generation technology is one of the key technologies in the RoF system.In this thesis,we mainly studied the photonic millimeter-wave frequency-multiplying generation technology and its transmission performance.Firstly,the basic principle and key technologies of the photonic millimeter-wave generation technology are introduced.Secondly,three kinds of photonic millimeter-wave frequency-multiplying schemes based on external modulators are proposed.Thirdly,the full-duplex RoF transmission system based on photonic millimeter-wave frequency multiplying is studied.The research work is structured as follows:1.Three kinds of photonic millimeter-wave generation schemes based on frequency multiplying are proposed.In scheme 1,a frequency octupling scheme based on an integrated polarization division multiplexing dual-parallel Mach-Zehnder modulator?PDM-DPMZM?by properly setting the RF driving signals,the angle of the polarization controller and the working points of the modulator is proposed.The proposed scheme does not require any optical or electrical filters,and the scheme is not sensitive to modulation index.The simulation results show that when the modulation index is set in a reasonable range?4.294.6?,an 80-GHz millimeter wave is generated using a 10-GHz radio frequency signal.The power spectrum is very pure,and the signal-to-noise ratio?SNR?can reach51.3 dB.In scheme 2,a frequency 12-Tupling scheme based on two parallel dual-parallel polarization modulator?PolM?is proposed.In this scheme,the PolM has the high extinction ratio and does not need the direct current bias,so there is no direct current bias drift problem,which ensures the good stability of the system.In scheme 3,a frequency24-Tupling scheme based on two cascaded dual polarization Mach-Zehnder modulator modulator?DPol-MZM?without using any optical and electrical filters is proposed.By properly setting the RF driving signals,the angle of the polarization controller and the working points of the dual polarization modulator,an optical signal with only±12th order sidebands is generated.A 120-GHz millimeter wave is generated using a 5-GHz radio frequency wave in the simulation.2.A microwave photonic phase shifter based on an integrated dual polarization modulator?DPol-MZM?is proposed.The simulation results show that the phase of the optical millimeter signal output from the polarizer can be tuned from 0 to 360°by simply adjusting the polarization direction of the lights whereas the amplitude keeps constant.3.The full-duplex ROF system is introduced,and a full-duplex RoF transmission system based on a frequency 12-Tupling millimeter-wave generation scheme is presented.The eye diagram and the curve of bit error rate and receiving optical power of the link are verified by simulation.The simulation results show that the uplink and downlink in the case of BTB and after transmission 10 km,30 km,50 km through the optical fiber.After data demodulation,the amplitude and width of the eye diagram does not change,which shows that both the downlink and uplink are insensitive to the periodic fading and the symbol narrowing caused by fiber dispersion.For the downlink,when the received optical power is above-17.5 dBm,the bit error rate is below 10-10.For the uplink,when the received optical power is above-23.3 dBm,the bit error rate is below 10-10.4.The terahertz technology is introduced briefly,and the scheme of THz wave generation based on microwave photonics is analyzed.The simulation results show that a 0.3-THz terahertz wave is generated from a 25-GHz local oscillator signal,and the power of THz wave is 90?W. |
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