Brillouin optical time-domain analysis sensor with amplification of pump pulses and tolerant to non-local effects

We demonstrate a simple technique to provide conventional Brillouin optical time-domain analysis sensor with compensation for pump pulse attenuation and tolerance to non-local effects. The technique is based on operating the sensor in loss configuration so that energy is transferred from the probe wave to the pump pulse that becomes amplified as it counter-propagates with the probe wave. Furthermore, the optical frequency of the probe wave is modulated along the fiber so that the pump pulse experiences a flat gain spectrum that equally amplifies all the spectral components of the pulse, hence, preventing distortion. The method is experimentally demonstrated in a 100-km fiber link, obtaining a measurement uncertainty of 1 MHz at the worst-contrast position.The authors wish to acknowledge the financial support from the Spanish Ministerio de Economía y Competitividad through project TEC2013-47264-C2-2-R, FEDER funds and the Universidad Pública de Navarra