Dependence of Brillouin Frequency Shift on Temperature and Strain in Poly(methyl methacrylate)-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, -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.