Investigation On Time Advancement And Pulse Distort Of Stimulated Brillouin Scattering Fast Light In Optical Fibers

With rapid development of optical communication technology,and under the historical background of further improving the ability of transformation and receiving information,the optical communication technology will be necessarily replaced by all optical network communication.All optical network communication is based on direct light-light conversion which has higher transmission efficiency and greater transmission capacity(about tens Tb per second),thus its potential applications have been implemented.The fast and slow light technology possesses the ability to control the speed of light,So it can be used to achieve synchronization or cache of the signal light.It is also being considered for optical switching and routing in all-optical network communication.The fast and slow light technology in optical fibers has been a hot research spot among different systems in recent years.The fast and slow light technology based on SBS in optical fibers has been a hot area of research because of its many advantages,such as low threshold pump power,operating at room temperature,adjusting arbitrarily working wavelength and better compatibility with optical fiber communication system,etc.In this paper,the time advancement and the pulse distortion of SBS fast light are discussed and studied,especially the SBS fast light properties of narrow band and broad band pump light in optical fibers are analyzed.The main content of the thesis is as follows.1.Firstly,different tunable technologies which can realize fast and slow light are summarized and compared.Then the research progress of SBS fast light at home and abroad in recent years is mainly discussed,including increasing the fast light advancement,decreasing the pulse distortion and using special optical fibers to increase advance efficiency based on SBS.2.The physical model and mathematical process of the Brilliouin scatting in optical fibers are presented.Considering the difference between fast light and slow light in optical fibers,the coupled amplitude equations involving acoustic and optical wave in optical fibers are improved.We started from SBS coupled wave equations based on a monochrome pump light.The small signal solutions of SBS fast light are studied,the time advancement and pulse compression factor are respectively obtained.3.Under the condition of small-signal model,the time advancement and pulse distortion of fast light based on the three coupled wave equations of SBS in high nonlinear optical fiber are investigated.The results indicated the time advancement increases linearly with the input signal power and transmission distance.Meanwhile,the degree of pulse compression becomes larger.Under the same condition,the time advancement obtained in high nonlinear optical fiber is larger than the single mode fiber,the maximum advancement can be up to 203 ns when the signal power is 50 mw and the fiber length is 50 m,the pulse distortion achieved in high nonlinear fiber is really small.The efficiency of time advancement of fast light in high nonlinear fiber is significantly improved and the pulse deformation is obviously decreased.The research results provide reference for the implementation and application of fast light.4.The method of broad band pump light including many spectral lines is suggested and discussed.The Brillouin absorption characteristics and the phase characteristics of the broad band pump light with different spectral lines are analyzed.It is concluded that a broadband absorption spectrum can be obtained by superposition of equal amplitude spectral lines.The width of the absorption spectrum increases with the number of spectral lines.And the line spacing can seriously influence the linearity of the absorption spectrum.Then broad bandwidth SBS theory is proposed,SBS fast light characters based on Gaussian broadband pump spectrum and rectangular flat pump spectrum are investigated respectively.The results admit that broad bandwidth Gaussian pulse spectrum and rectangular flat pump can reduce the pulse distortion,then can largely maintain the original pulse waveform.At the same time,the Rectangular spectrum pump fast light has smaller pulse distortion degree and own more advantages compared to the Gaussian spectrum pump.