Longitudinal acoustic modes and Brillouin-gain spectra for GeO_2-doped-core single-mode fibers

Brillouin gain spectrum characterization in single-mode optical fibers

“…The Brillouin frequency shifts range from 11.5 GHz to 13 GHz at 1.32 m and a change of 94 MHz/wt.% is found between Brillouin shift and GeO 2 -core concentration, as shown in Fig. 7, confirming and specifying previously reported results [12], [16]. The points on the vertical axis correspond to the reported value for bulk silica and to a pure silica core fiber with an -doped cladding respectively.…”

“…Rowell et al were the first to describe guided fiber acoustic modes involved in SBS [11]. A theory for longitudinal acoustic modes in GeO 2 doped fibers was presented by Shibata et al [16]. It is the nature and concentration of doping in the fiber that determines the guiding properties of the fiber core for acoustic waves.…”

Physical Nature of “Slow Light” in Stimulated Brillouin Scattering

“…It is evident from this expression that the shorter the radiation wavelength the wider the spectrum, so for radiation in the short wavelength transmission window of silica, λ ≅ 0.2 μm, Γ B is expected to be ~2π GHz compared to ~ 20 MHz at telecom wavelengths, λ ≅ 1.3-1.6 μm. The SBS gain bandwidth in fibers may also be broadened through varying fiber design, doping concentration, strain and/or temperature (Tkach et al, 1986;Shibata et al, 1987;Azuma et al, 1988;Shibata et al, 1989;Yoshizawa et al, 1991;Tsun et al, 1992;Yoshizawa & Imai, 1993;Shiraki et al, 1995;LeFloch & Cambon, 2003). However the highest achieved line-width enhancement factor, compared to Γ B is ~5, (Yoshizawa et al, 1991).…”

Enhancement of stimulated Brillouin scattering of higher-order acoustic modes in single-mode optical fiber

“…The studies of higher-order acoustic modes and their features in the BGS are limited either to the assumptions V S1 = V S2 and 1 = 2 (indices 1 and 2 refer to core and cladding, respectively) or to specific parameter sets of particular fibers under the undepleted regime. [6][7][8] Considering the current advanced fiber fabrication technology, especially for microstructured fibers, a study of SBS of higher-order acoustic modes for a distribution of V L , V S , and involving pump depletion (e.g., pump-probe SBS amplification) and subnanosecond pulses is required.…”

“…This may explain the discrepancy between experimental and numerical values of the Brillouin frequencies. 6,3 By examining the displacement fields, we note that the acoustic wave can be well approximated as a scalar field, in terms of change in the density, by E q / 0 = ٌ · u Ϸ i␤ q u z . By the decomposition method (Ref.…”