Surface Brillouin Scattering in Disordered Optical Fibers With Transverse Anderson Localization Guiding Mechanism for Evaluation of Longitudinal Structural Fluctuations

We numerically investigate the surface Brillouin scattering (surface-BS) in a transverse Anderson localization (TAL) guiding silica glass-air disordered optical fiber (DOF) with random air-holes. The normalized light intensity profiles of light beams propagating along DOF at different launch positions are obtained, which confirms the TAL mechanism. Then, the surface-BS in DOF is numerically investigated by the equation of elastodynamics with the electrostriction. It is found that there are two main peaks in the surface-BS spectrum and the Brillouin frequency shift (BFS) is sensitive to the air-fill fraction of DOF. Furthermore, the feasibility of longitudinal structural fluctuations evaluating of DOF by the Brillouin optical time-domain analysis technique is analyzed and discussed. The average sensitivity of BFS to the air-fill fraction is simulated to obtain an optimal performance in practical application. This paper is an interesting theoretical enlightenment for combining the novel concepts of surface-BS and DOF, also a useful exploration of longitudinal structural evaluating method for special optical fibers with microstructures.