Optical fibers with preset stimulated backward Brillouin scattering thresholds

摘要

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