Research On Linearization Technology Of Microwave Photonics Links

Microwave photonics is an inter-disciplinary subject that combines optoelectronics and microwave technology.It mainly uses the photonics methods to deal with microwave signals to improve the performance of existing microwave systems.In recent years,with the rapid development of optical fiber communication and integrated optics,many countries have actively carried out research on microwave photonics.With the diversification of the demand for communication services,the bandwidth and capacity of the existing communication systems are facing great challenges.All the major operators and research institutions are actively studying the wider and more capacity of the communication system solutions.This paper mainly studies the way to improve the spurious free dynamic range of microwave photonic links,and analyzes the distortion mechanism of microwave photonic links in detail.The microwave photonic link model based on single-drive and dual-drive Mach-Zehnder modulator is simulated by using optical software optisystem,and the distortion mechanism of the two systems and the influence factors of the spurious free dynamic range are analyzed.The main contents of this paper include:(1)the current research status of microwave photonic links based on external modulation is reviewed.The core components of the microwave photonic link are investigated mainly: the research and development of laser,electro-optic modulator and photodetector,and the linearization methods of microwave photonic link based on intensity modulation and phase modulation.Then the microwave photonic link model of intensity modulation direct detection is introduced,and the factors affecting the performance of the microwave photonic link are analyzed in detail,including system gain,system noise characteristics and nonlinear distortion,in which the distortion of single tone test and dual tone test is analyzed in detail,and two kinds of test method links are given respectively.The frequency and amplitude of the harmonic components are produced.Finally,the definition of the spurious free dynamic range and its influencing factors and measurement methods are given.(2)the basic principle of the linearization of the microwave photonic link based on single-drive dual-parallel Mach-Zehnder modulator(DPMZM)is studied.Firstiy,the principle of the method is detailedly divided in theory.The link model is carried out in Optisystem software to simulate the method.The simulation results are in good agreement with the theoretical analysis.The simulation results are verified by experiments,and the spurious dynamic range of the two schemes is measured.(3)the basic principle of the linearization of the microwave photonic link based on the dual-drive dual-parallel Mach-Zehnder modulator is proposed.Firstly,the structure of the dual-drive Mach-Zehnder modulator is introduced,and the theoretical deduction is carried out.The theory proves that this method can completely eliminate the three-order inter-modulation distortion of the system and thus improve the link's spurious free dynamic range.Then the link model is carried on the Optisystem software,and the simulation results are in good agreement with the theoretical prediction,and the method is not only suitable for small signal model,but also in the large signal model.