| All-optical network is a research hotspot in the field of optical fiber communication,which aims to realize the transmission of information in the all-optical domain.Fiber optical modulator plays a vital role in all optical network system because of its fiber compatibility,low loss and small size.In recent years,with the development of fiber fabrication technology and post-processing technology and the emergence of new functional materials,the research of in-line optical fiber modulator based on functional materials has attracted extensive attention of researchers.As a zero-dimensional nanometer material,Pb S quantum dots have special physical properties(quantum limiting effect,size effect,etc)and good optical properties(photorefractive index,emission,absorption adjustable characteristics,etc)compared with other ordinary materials.In this thesis,Pb S quantum dots are deposited into the polishing zone of D-shape fiber by natural deposition method,using the photorefractive properties of Pb S quantum dots,the modulation characteristics of deposited Pb S quantum dots in a fiber optical modulator in the wideband and single-frequency band are studied,and on this basis,the polarization dependent modulation characteristics and time response characteristics of deposited Pb S quantum dots are also studied.The main research contents are as follows:(1)Firstly,the D-shape fiber structure is selected as the basic structure of the in-line optical fiber modulator,and the transmission performance of the D-shape fiber is simulated by Comsolmutiphsics5.5a software.On this basis,the influence of the polishing parameters on the fiber loss and polarization is studied,at the same time,combined with the tuning mechanism of Pb S quantum dots,the mode field distribution of D-shape fiber deposited Pb S quantum dots is simulated and analyzed,which provides theoretical guidance for the subsequent experiments.(2)It has been proved experimentally that in-line optical fiber modulator has good modulation characteristics for the deposited Pb S quantum dots.Under the action of internal pumping light(λ=980nm),the signal light power only changes by 0.05 d B when the pumping light power increases from 0m W to 60 m W without the deposition of Pb S quantum dots.The signal light power varies by 3.6d B and the modulation efficiency is about 0.06 d B/m W.(3)In order to study the polarization-related modulation characteristics of in-line optical fiber modulator with deposited Pb S quantum dots,by adjusting the polarization state of signal light,and making the transmission mode change.When the transmission mode of signal light in the TM mode,the signal light power changes by 2.3d B and the modulation efficiency is about 0.037 d B/m W during the process of gradually increasing from 0m W to 60 m W.When the transmission mode of signal light in the TM mode,the signal light power changes by 9d B,and the modulation efficiency is about 0.15 d B/m W.In addition,in order to further characterize the performance of the in-line optical fiber modulator,its response time is tested,it can respond to signals at frequencies up to 50 k Hz,and its response time is in the order of ms. |
