{'fraction_non_alphanumeric': 0.018629407850964737, 'fraction_numerical': 0.001996007984031936, 'mean_word_length': 5.064516129032258, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Stimulated Brillouin scattering modeled through a finite difference time domain approach

Stimulated Brillouin scattering (SBS), in an optical fiber, is a three-wave interaction (3WI) resulting from a coupling between light and acoustic waves. In a fiber optic sensing context, SBS results from the interaction between counterpropagating pulsed and continuous fields. We formulate a solution to the time dependant, one dimensional 3WI model in a SBS based fiber optic sensor. It is shown that a low complexity, first order finite difference time domain (FDTD) solution is capable of accurately modelling the dynamics of SBS with little computational effort. A modification to the first order scheme is proposed to combat numerical damping and dispersion, brought on by the low order of the solution. Examples are presented, validating the performance of our modelling technique. The effect of pulse power and risetime on the resulting scattering is examined, along with the effects of γa, an intrinsic fibre parameter related to the linewidth of the Brillouin spectrum. The spatial and temporal evolution of the acoustic field is illustrated; the effect of the steady state value of this field on the 3WI is investigated. The steady state acoustic field strength is related to the extinction ratio of the pulsed source, and it is found that this parameter has a significant influence on the scattering. This type of modelling provides a rapid means of investigating SBS as a tool in fiber optic sensing.