Combined Method for SBS Suppression in High Numerical Aperture Single-Mode Optical Fibers

We propose and test a combined method of suppression of stimulated Brillouin scattering (SBS) in high numerical aperture (NA) optical fibers that makes it possible to use both the application of tensile-compressive stresses and the control of the transverse acoustic refractive index profile. In the experiment on the acoustically tailored Al
₂
O
₃
-GeO
₂
-doped fiber (optically step-index, NA
$\sim ~0.2$
) with a quasi-four-peak SBS gain spectrum
$\sim 0.8$
GHz wide, we used the offset-core technique to create a tensile-compression stress over the whole fiber length, controlled by small-diameter coiling. The stress causes each of the spectral peaks to broaden without overlap. Thus, at the optimal coiling diameter, an 11.3dB net SBS gain suppression has been obtained, where
$\sim 5$
dB is due to the tension. Ways to enhance SBS suppression in such fibers up to 18dB and more using the proposed technique are also discussed.