Pump-Power-Independent Double Slope-Assisted Distributed and Fast Brillouin Fiber-Optic Sensor

A small modification of the fast and distributed slope-assisted Brillouin time domain analysis (SA-BOTDA) method allows it to easily implement pump-power independent measurements of strain and/or temperature, using the ratio between readings taken on both slopes of the Brillouin gain spectrum. Employing this new double SA-BOTDA measurement technique, fast ( ${\sim}{\rm 100}~{\rm Hz}$ at ${\sim}{\rm 1}\hbox {-}{\rm kHz}$ effective sampling rate) strain measurements are shown to be immune to pump pulse power variations as large as 6 dB. At the expense of halving the sampling rate, this technique still maintains all the benefits of its SA-BOTDA predecessor. In particular, its ability to handle (Brillouin) longitudinally inhomogeneous fibers is demonstrated.