The core-mode conversion between LP01 and LP11 modes is obtained in the FMF by cascading long period fiber gratings (LPFG) working at the same wavelength region.  Different transversal modes of stimulated Brillouin scattering (SBS) can be implemented based on broadband long period fiber gratings (LPFG) and acoustically induced fiber gratings (AIFG).  The RFL base on two broadband LPFGs can obtain high purity LP11 mode operating in the range of 1543 nm to 1565 nm. 
LPFG
Different transversal modes of stimulated Brillouin scattering (SBS) can be implemented based on broadband long period fiber gratings (LPFG) and acoustically induced fiber gratings (AIFG).  Moreover, the output mode can be dynamically switched between LP01 mode, LP11a mode and LP11b mode by modulating frequency shift keying (FSK) signal of the AIFG. 
AIFG
The core-mode conversion between LP01 and LP11 modes is obtained in the FMF by cascading long period fiber gratings (LPFG) working at the same wavelength region.  Different transversal modes of stimulated Brillouin scattering (SBS) can be implemented based on broadband long period fiber gratings (LPFG) and acoustically induced fiber gratings (AIFG).  The RFL base on two broadband LPFGs can obtain high purity LP11 mode operating in the range of 1543 nm to 1565 nm. 
LPFG
The core-mode conversion between LP01 and LP11 modes is obtained in the FMF by cascading long period fiber gratings (LPFG) working at the same wavelength region.  Different transversal modes of stimulated Brillouin scattering (SBS) can be implemented based on broadband long period fiber gratings (LPFG) and acoustically induced fiber gratings (AIFG).  The RFL base on two broadband LPFGs can obtain high purity LP11 mode operating in the range of 1543 nm to 1565 nm. 
LPFG