Experimental Generation And Characteristic Analysis Of Chaotic Brillouin Dynamic Grating

The Brillouin dynamic grating(BDG)is based on the stimulated Brillouin scattering effect in the optical fiber,and has the advantages of all-light generation,separation of reading and writing,fast reconstruction,and multi-parameter adjustable.At present,it has been applied in the fields of non-cross-sensitive measurement of temperature and strain,high spatial resolution sensing,surrounding medium concentration sensing,optical delay line,optical signal storage,and all-optical flip-flop.However,the traditional BDG has problems such as difficult to maintain stably and prone to multiple gratings.In order to solve the above problems,this thesis uses the thumbtack-shaped autocorrelation characteristics of chaotic lasers to experimentally produce chaotic BDG in a polarization-maintaining fiber for the first time,and further studies the reflection characteristics of chaotic BDG.The main work progress is as follows:(1)The overall experiment plan of chaotic BDG was designed,and the key experiment instruments were selected and their parameter settings were carried out.On this basis,an experimental system for generating chaotic BDG was built.A chaotic laser with a spectral bandwidth of 1.86 GHz and a frequency difference of the Brillouin frequency shift in the slow axis of the polarization-maintaining fiber is used as two pump lights,which are injected from the slow axis at both ends of the 100 m long polarization-maintaining fiber.A chaotic BDG with a length of 3.4 cm is generated where the two pump waves meet.Then the continuous wave output by the tunable laser is injected from the fast axis of the polarization-maintaining fiber to detect the chaotic BDG,thus confirming the generation of the chaotic BDG.(2)The gain spectrum and reflection spectrum characteristics of the chaotic BDG are analyzed through experiments.The research shows that when the power of the two chaotic pump waves are 300 m W and 20 m W,the maximum reflectivity of the chaotic BDG is0.116%.When the bandwidth of the chaotic pump wave is at 3.98 GHz,the gain spectrum width of the chaotic BDG is 40.3 MHz,and the reflection spectrum width can reach 3.06 GHz.When the spectrum bandwidth of the chaotic laser gradually increases,the Brillouin gain spectrum width increases at a speed of 0.668 MHz/GHz,while the reflection spectrum width of chaotic BDG increases at a rate of 0.44 GHz/GHz.