Investigation Of Forward And Backward Brillouin Scattering In Fibers

In this paper, the effects of the forward Brillouin scattering on stokes wave in single fibers and the effects of fiber structure on the backward Brillouin frequency shift and backward Brillouin gain peak in photonic crystal fiber are investigated by the all-vector finite element method.The main contents and achievements are as follows.1. The effects of R0,m and TR2,m acoustic modes of forward Brillouin scattering on gain, phase modulation and additional birefringence in single mode fiber are investigated. The results show that the gain of forward Brillouin scattering reaches maximum at their frequencies matching those of R0, 8 and TR2, 10 modes in R0, m and TR2,m(0o/90o) modes, and the gain increases with the increasing of pump power. The Stokes wave phases is modulated obviously by R0,1, TR2,5, TR2,7 and TR2,10 mode, where TR2, m modes play a vital role in the phase modulation which linearly increases with the increasing of pump power. TR2,1, TR2,5, TR2,7, TR2,10 modes obviously induce additional birefringence which linearly increase with pump power increasing.2. The effects of fiber structure on the backward Brillouin scattering frequency shift and backward Brillouin sctttering gain peak in photonic crystal fiber are investigated. The results indicate that the Brillouin frequency shift decreases and the Brillouin gain peak increases as the hole diameter increases when air hole pitch and air hole layer number are constant. At given air diameter and air hole layer number, the Brillouin frequency shift increases and the Brillouin scattering gain peak decreases with the air hole pitch increasing. At the given air diameter and air hole pitch, the Brillouin frequency shift almost has no change and the Brillouin gain peak decreases with the air hole layer number increasing.