The effect of the gain dependency of the linewidth of Brillouin amplification on double slope-assisted dynamic sensing techniques

The effect of the gain dependency of the Brillouin linewidth on double-slope-assisted Brillouin optical domain, dynamic sensing techniques is studied. These double-slope methods are immune to pump-power related peak Brillouin gain variations, however, they are not immune to gain-dependent variations of the shape of the Brillouin gain spectrum. For a 15ns pump pulse, this gain-dependent shape of the normalized Brillouin gain is shown to lead to a 5.5 [%/dB] strain error when the double-slope sum-difference approach is used, compared with a 7 [%/dB] error when the double-slope ratio approach is used. Ways to compensate for these issues are discussed.