Practical limitations of the slope assisted BOTDA method in dynamic strain sensing

By analyzing the operation of the slope assisted Brillouin Optical Time-Domain Analysis (BOTDA) method, it comes out that the acquisition rate is practically limited by two fundamental factors: the polarization scrambling frequency and the phase noise from the laser. As regards polarization scrambling, we show experimentally that the scrambling frequency poses a limit on the maximum acquisition rate for a given averaging factor. As regards phase noise, we show numerically and experimentally that the slope assisted method is particularly sensitive to the laser phase noise, due to the specific positioning of the pump-probe frequency shift on the Brillouin Gain Spectrum (BGS).