Research And Simulation Of Electrical Properties In Core Area Of Lithium Niobate Modulator

Modulator with great performance is of great importance in fiber communication and optical signal processing. Electro-optic modulation is based on electro-optic effect,which means when a light is traveling through an optical waveguide,the properties of the light will change due to the electrical signal.By making full use of the linear parts of the refractive index change caused by the electric field, we can realize the linear modulation.Modulators which take lithium niobate crystal as the main material are becoming increasingly prevailing during the current years.The aim of this paper is to research the electrical property in the core parts of the modulator,including the electric filed distribution,extraction of the electric parameters and the frequency property of the network consist of the electrodes and the wavaguide.First,some physical properties of Li NO3 were introduced.The anisotropy of Li NO3 has decided the physical properties were closely connected to the direction.Among the properties,the electro-optic effect was what we concerned most,and then we analyzed the reason why lithium niobate was suitable to be the main material of the modulator.Then the structure and operational principle of Mach-Zehnder Modulator and phase modulator were briefly introduced.Afterwards,we discussed the short term drift and long term drift in the modulator.Both of them will have negative effects on regular work of the modulator,we must try to eliminate or reduce the effects.By constructing proper electric model of them,we can find the key parameters which affects the drift, and finally we can find some methods to improve the drift.The electric field between the electrodes plays an important role in the work of a modulator,so the electric field distribution is what we are interested in.Chapter 4 mainly researched the electric field distribution in the core area,based on software simulation and Point Matching Method,respectively.And a new way to estimate the parameters was proposed.People usually research the DC characteristic of a modulator,but there are few reports on the AC characteristic of it.At last we researched the AC characteristic of the modulator.The research was carried out on the MZM.By processing DC response and AC response data and making a curve fitting,we can obtain the frequency property of the modulator.From the frequency property curve,we can get some useful information of the electric model.We have researched the properties of the modulator both in time domain and frequency domain.By the work above,the ability of designing the modulator is improved,and we made a more comprehensive analysis of the modulator's performance.