{'fraction_non_alphanumeric': 0.029141104294478526, 'fraction_numerical': 0.018404907975460124, 'mean_word_length': 5.219047619047619, '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}}
Brillouin frequency shift dependences on temperature and strain in PMMA-based polymer optical fibers estimated by acoustic velocity measurement

We estimated the dependences of Brillouin frequency shift (BFS) on temperature and strain in poly(methyl methacrylate)-based polymer optical fibers using ultrasonic pulse-echo technique at ~10 MHz. The estimated BFS dependence on temperature was linear with a coefficient of approximately -17 MHz/K at 650 nm pump, which was -34 times larger than that of silica fibers at 650 nm pump. In contrast, its strain dependence was found to be nonlinear, probably originating from the elastic-to-plastic transition.