Impact of pump depletion on the determination of the Brillouin gain frequency in distributed fiber sensors

The energy transfer between the two interacting optical waves in a distributed sensor based on stimulated Brillouin scattering can lead to a non-uniform spectral distribution of the pumping power after a long propagation. This results in a spectrally distorted gain that biases the determination of the maximum gain frequency. A quantitative analytical model gives an expression for the tolerable pump power change keeping the maximum bias within a given accuracy.