Research On The Brillouin Scattering Characteristics With Relation To Fiber Structures

Brillouin scattering is one of the most important nonlinear effects of the optical fiber with the interaction between photon and acoustic phonon. Such nonlinear effect has been widely used for the building structural health monitoring, submarine cable monitoring, narrow bandwidth Brillouin laser, Brillouin laser amplifier, Brillouin filter, slow light effect, and etc. The Brillouin sensor has the advantage of acquiring distributed information such as the strain and the temperature along the fiber, which is attractive due to its resistant to electromagnetic interference, small size, and etc. The different fiber structures, which may induce different acoustic or light mode states, resulting in the dissimilar Brillouin characteristics. The study of the Brillouin scattering spectrum will help us to produce different fiber structures for its potential applications as previously stated.Firstly, this paper designs an experiment that brings two beams of pulses light incident on the polarization mode fiber and then measures the Brillouin scattering spectrum, which is caused by the generated laser sideband gain, through a BOTDA system. A preliminary analysis of the reason for obtaining such scattering spectrum is studied and then compared the obtained spectrum with the one in general mono mode fibers. Also the differences between these two kinds of Brillouin scattering spectrum and the advantage of the laser Brillouin scattering spectrum sidebands are discussed.Secondly, we selecte a micro-scaled silica fiber made by fusing a biconical taper(FBT) method and then detected its Brillouin scattering spectrum and measured the temperature and strain coefficients. The appearance of multiple peaks in Brillouin scattering spectrum and the spectral changes with external stress/temperature are observed and demonstrated. In addition, we also study the Brillouin scattering effect of a micro-fiber produced by chemical etching a normal single-mode fiber and measure its temperature and strain coefficients.By comparing the Brillouin scattering spectrum which acquired by measured experiments of micro-nano fiber and the scattering spectrum of general mono modefibers, the influence of the fiber structure in the Brillouin scattering spectrum was demonstrated to some extent. At the same time, we hope these results could provide referring data for the future micro-fiber sensor production.