Optical fibers comprising a core region surrounding by a cladding region, and having a high stimulated backward Brillouin scattering threshold, PTH, for telecommunication transmission line application, or a low PTH for distributor sensor application are disclosed. By controlling the longitudinal and shear acoustic wave velocity profiles of an optical fiber such that VL,core 1.03 VL,cladding and VS,core 1.03 VS,cladding, where VL,core and VS,core are respectively the longitudinal and shear acoustic wave velocities of the core region, and VS,core and VS,cladding the longitudinal and shear acoustic wave velocities of the cladding region, the optical fiber will have a PTH higher than 20 milliwatts. For low PTH optical fibers, that is, with a PTH lower than 1 milliwatt, the longitudinal and shear acoustic wave velocity profiles of the fiber must be such that VL,core 0.97 VL,cladding and VS,core 0.97 VS,cladding. In both high and low PTH optical fibers, the refractive index of the core region is higher than that of the cladding region for optical wave guidance.
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