Research On Linearization Of High Danamic Range Microwave Photonics Link

Microwave photonics is a new discipline studying the law and application of the interaction between microwave and lightwave. It is generally regarded as an effective way to meet the major challenges in microwave systems. Microwave photonics link is an important branch in microwave photonics. Frontier research in microwave photonics link is how to improve the bandwidth and dynamic range of the microwave system. To realize high dynamic range link, the key technology is linearization technique.Microwave photonics link is generally divided into two categories, intensity modulation link and phase modulation link. With development of integrated dual-parallel modulator, linearization based on dual-parallel modulator is a hot topic in intensity modulation link in recent years. The main stream of linearization techniques currently is using small signal approximation method, and therefore it is not able to achieve suppression of third-order inter-modulation distortion under large signal. That is to say, in current researches of high linearity intensity links, we have not been able to completely suppress third-order inter-modulation distortion. Focusing on nonlinear distortion in intensity modulation link limiting transmission performance, this thesis proposed a highly linear approach for microwave photonics link based on dual-drive dual-parallel Mach-Zehnder modulator. Based on driving conditions and parameters optimization settings of dual-drive dual-parallel Mach-Zehnder modulator, this thesis explored a linearization scheme to completely suppress the third-order inter-modulation distortion. The thesis presented theoretical analysis under both small signal and large signal model, detailed simulation and prototype experiments verifying complete suppression of third-order inter-modulation distortion. The thesis also analyzed parameters’impacts on experimental performance in detail. The simulation results are in good agreement of the theoretical analysis. Experimental results also provide strong support for the proposed linearization technique.In phase modulation link, according to the correspondence between signal amplitude and modulated optical phase, phase modulation microwave photonics link can be considered having a linear modulation, the key problem of the link is how to achieve broadband and flexible phase modulation to intensity modulation conversion and linear demodulation. To improve the performance of phase modulation microwave photonics link, currently a lot of researches are focused on realizing coherent detection linearization, including phase-locked feedback loop and IQ demodulation techniques. But on whole, coherent detection linearization has narrow bandwidth and structure of high complexity. This thesis, focusing on direct detection of simple structure, proposed linearization of a broadband phase modulation microwave photonic link. At the output of the phase modulator, we use spectral processor to perform optical spectrum phase-control in order to achieve phase modulation to intensity modulation conversion and third-order inter-modulation distortion suppression. We used this method to adjust phase shifts of corresponding optical spectrums, and derived the optimal phase shift to maximize the suppression of third-order inter-modulation distortion. Detailed simulation and prototype experimental verification are presented in this thesis. The simulation and experimental results verify well the linearization performance as in theoretical analysis.