Key Technologies Research On Broadband Microwave Photonic Coherent Link With High Dynamic Range

With the continuous expansion of microwave frequency to high frequency,microwave signal processing becomes more difficult.In 1990 s,microwave photonics was proposed,which is an emerging interdisciplinary.It is a new method to realize the generation,transmission and processing of microwave signals employing the high speed and broadband characteristics of photonics technology.Microwave photonic link is one of the core content of microwave photonics,which has many advantages such as small volume,light weight,low noise,low loss,high bandwidth and immunity to electromagnetic interference.Therefore,it is widely used in the field of civil communication and national defense.It is of great significance to study the broadband and high dynamic microwave photonic link.Improvement of the link noise figure and the IMD3 suppression are mainly studied in this paper.The technical schemes to improve the noise figure and suppress the IMD3 are proposed,and the spurious free dynamic range of the link is effectively improved.The main work of this paper is as follows:1.The concepts of electro-optic conversion,photoelectric detection and the effect of fiber dispersion on the power attenuation of microwave signal are deduced.Besides,the power attenuation caused by fiber dispersion is simulated by using MATLAB.For the intensity modulation directly detection link,the RF gain,the noise figure and the spurious free dynamic range are analyzed.The MATLAB simulation analysis of the factors affecting the link performance parameters is also given.2.In the improvement of the noise figure,the balanced detection technique is introduced to reduce the relative intensity noise of the laser.The simulation link is built by OptiSystem and the results show that the signal to noise ratio of the output signal is improved by 15.0dB.The link based on the balanced detection is established,and the spurious free dynamic range of the link is 71.28dB·Hz^2/3.3.An IMD3 suppression technique based on power and bias control is proposed.The suppression of IMD3 is realized by adjusting the power distribution ratio of RF signal and the bias of the dual parallel Mach-Zehnder modulator.The theoretical derivation shows that the IMD3 of the link is completely eliminated when the linearization condition is satisfied.The linearized simulation link is built by using OptiSystem combined with balanced detection technology.The simulation results show that the link IMD3 suppression ratio is as high as 48.71 dB.The linearized micrwave photonic link is established.The experimental result shows that the dynamic range of the link can be increased by 7.37 d B.4.A linearized link based on single sideband modulation is proposed.The suppression of IMD3 is realized by controlling the power ratio and phase difference of two optical carriers.The theoretical analysis shows that the IMD3 of the link will be completely suppressed when the link satisfies the linearization condition.A linearized link based on single sideband modulation is constructed by using dual electrode Mach-Zehnder modulator and balanced bridge.The experimental result shows that the sideband suppression ratio is 9.95 dB and the spurious free dynamic range is increased to 6.43 dB by using linearized scheme.