Microwave Photonic Link And Measurement Technology Based On Optical Single Sideband Modulation

In long-distance microwave photonic link,the optical single sideband modulation can avoid the fiber dispersion effects on microwave and millimeter wave signal transfer.Therefore,it is widely used in radio over fiber?ROF?link,optical controlled phased array and other systems.The link performances of four optical single sideband modulation links are studied,and the optical vector network measurement of optical devices is realized by using optical single sideband modulation.The first part establishes the theoretical model of traditional optical single sideband modulation link based on 90°RF phase shift and dual-electrode Mach-Zehnder modulator,and the theoretical performances including gain,1dB compression point and spurious-free-dynamic-range are obtained.By setting up experiments,the theoretical results are verified.However,the traditional optical single sideband modulation link has many defects.For example,the residual first-order optical sideband cannot be eliminated,and higher-order sidebands have a great impact on the link.Therefore,the optical single sideband link based on the 120°radio frequency phase shift and the dual-electrode Mach-Zehnder modulator is demonstrated,and after establishing the theoretical model,the link gain and spurious free dynamic range are analyzed and experimentally measured.The optical single sideband link based on a 120°RF phase shift and a dual-electrode Mach-Zehnder modulator not only suppresses the-1^st order optical sideband but also has a+2nd optical variation band,which reduces the error induced by the higher-order optical sidebands.And the link gain of the scheme is slightly higher than that of the traditional scheme.Then the double parallel Mach-Zehnder modulator is selected to realized optical single sideband link based on the 90°RF phase shift.The link performances are obtained by experiments,although the link gain is lower than the previous two methods,However,the power ratio of the positive and negative first-order optical sideband can be achieved 30dB in the experiment,which is much higher than the 20dB of the optical single sideband microwave photon link based on two-electrode Mach-Zehnder modulator.A optical single sideband link based on 120°RF phase shift and double parallel Mach-Zehnder modulator is also demonstrated.It is found that the link has advantage in suppressing the residual-1^st order optical sideband,and the suppressing of the+2^nd order optical sideband is almost equal to that based on the double electrode Mach-Zehnder modulator.In conclusion,the power ratio of positive and negative 1^stt order optical sideband of the optical single sideband modulation link based on dual-parallel Mach-Zehnder modulator is much higher than that based on the dual-electrode Mach-Zehnder modulator in the experiment.Then,the optical vector network measurement system based on optical single sideband modulation is used to measure the spectrum of a fiber bragging grating.Then based on optical single sideband modulation,a reconfigurable microwave photonic notch filter is constructed by using a tunable MZI coupled micro-ring resonator filter.The filter has the characteristic of adjustable center frequency.Finally,the effect of the residual sidebands on the microwave photonic filter is analyzed,the result shows when the magnitude ratio between the±1st order optical sidebands is closer to the optical extinction ratio of silicon nitride waveguide microring resonator,and the sum of phase difference between the±1st order optical sidebands and optical carrier,and the phase of silicon nitride waveguide microring is closer to odd numbers of?,the residual 1^stt order optical sideband can make the frequency rejection ratio of the microwave photonic filter larger.When there is no residual-1^stt order optical sideband,the radio frequency rejection ratio of microwave photonic filter is equal to the optical extinction ratio of the silicon nitride waveguide microring resonator.The results provide a new method to realize tunable microwave photonic filter.