SUPPRESSION OF STIMULATED BRILLOUIN SCATTERING IN HIGHER-ORDER MODE OPTICAL FIBER AMPLIFIER

PROBLEM TO BE SOLVED: To provide a fiber amplifier comprising a gain module with a higher-order mode (HOM) optical fiber appropriately doped to suppress stimulated Brillouin scattering and increase optical power output of the fiber amplifier.SOLUTION: An HOM-based optical fiber amplifier is selectively doped to minimize the presence of a dopant in a portion where an unwanted lower-order mode (especially fundamental mode) of a signal is present, within a core region. When gain media are decreased (removed) from these portions of a core, the amount of amplification applied to stokes waves to be propagated backwards is minimized (probably to be canceled). The minimization of amplification reduces increase of stokes power to be generated by Brillouin gains, thereby increasing the amount of power present in desired HOM amplified optical signal output to be propagated forwards.