Phase-shift based BOTDA measurements tolerant to non-local effects

We demonstrate a BOTDA sensor based on the use of the Brillouin phase shift that performs measurements tolerant to non local effects. This technique raises opportunities to increase the distance covered by these sensors and the maximum optical power of the probe wave injected to the fiber. As a result, the system has the potential to increase the SNR achieved at the last meters of the fiber. Proof-of-concept experiments demonstrate unaltered measurements of the phase shift spectrum in a 20Km long fiber for large frequency-dependent distortions of the pump pulse.The authors wish to acknowledge financial support from the Spanish Ministerio de Educación y Ciencia through the project TEC2010-20224-C02-01 and from the Universidad Pública de Navarra