Generation And Optimization Of Chaotic Brillouin Dynamic Grating

Compared with the conventional fiber Bragg grating,the Brillouin dynamic grating based on stimulated Brillouin scattering has the advantages of all-optical generation,reading and writing separation,adjustable position,tunable spectrum,rapid reconstruction,flexible and controllable parameters.In recent years,it has received sustained attention and in-depth research internationally,and has been widely used in distributed optical fiber sensing,variable optical delay line,fiber characterization,all-optical signal processing,high-precision spectral analysis and other fields.However,the Brillouin dynamic gratings induced by existing methods have the defects that the grating length is limited by the lifetime of the phonons,the intensity is unstable,and multiple gratings are easily generated.The thumbtack correlation of the chaotic laser signals make it possible to generate only one permanent dynamic Brillouin grating in a polarization maintaining fiber.Firstly,the chaotic Brillouin dynamic grating is generated in polarization-maintaining fiber by numerical simulation,and the characterization of chaotic Brillouin dynamic grating is studied in detail in this paper.Then the reflection characterization of chaotic Brillouin dynamic grating is improved by filtered optical feedback.The main work and progress are as follows:1)The theoretical model of the chaotic Brillouin dynamic grating is established.The chaotic Brillouin dynamic grating is generated in polarization maintaining fiber by numerical simulation,and the characterization of the reflection spectrum and gain spectrum of the chaotic Brillouin dynamic grating are studied in detail.We find that the width of the reflection spectrum of the chaotic Brillouin dynamic grating is inversely proportional to the effective length of the grating,and the effective length of the grating also has an influence on the width of the gain spectrum.Both the spectral widths of the reflection spectrum and the gain spectrum are not affected by the power of the chaotic pump light.In addition,we also studied the influence of the spurious gratings on the reflection characterization of the chaotic Brillouin dynamic grating due to the implicit external cavity feedback delay characteristic of the chaotic laser signal generated by an external cavity feedback semiconductor laser.2)The generation of spurious Brillouin dynamic gratings adversely affects the reflection characterization of the chaotic Brillouin dynamic grating.Based on the advantage of the filtered optical feedback technology in suppressing the external cavity feedback delay signature of chaotic laser,the suppression of the spurious gratings with filtered optical feedback semiconductor laser is studied in detail by numerical simulation in this paper.The results show that by adjusting the filter's bandwidth and its detuning from the laser frequency can effectively suppress the spurious gratings and significantly improve the reflection characterization of the chaotic Brillouin dynamic grating.