Investigation of Brillouin scattering in high Ge-doped few-mode fiber for bend-resistant sensing

The stimulated Brillouin scattering (SBS) of heavy germania-doped few-mode fiber (HG-FMF) up to 98 mol% and its dependence on temperature, strain, and bending are studied in this paper, respectively. Two widely located individual Brillouin gain spectra (BGS), whose central peaks are 8.151 GHz and 8.862 GHz, are found in HG-FMF, respectively. These two BGS are generated by the interaction between the fundamental and higher-order acoustic wave modes, which match well with the numerical simulation. The heavy germania-doping induced a large refractive index difference between the core and cladding that strongly confined the optical field in the fiber core and modified its Brillouin parameter. This fact also leads to the bending resistance of HG-FMF, in the bending radii from 0.3 cm to 2 cm, in contrast to traditional FMFs, and suppressed the temperature and strain sensitivity of the two BGS to 213 kHz/°C, 342 kHz/°C and 20.5 kHz/με, 21.4 kHz/με, respectively. These advances of HG-FMF could be potentially used for bending-resistant distributed multi-parameter sensing.