Brillouin distributed sensor over a 200km fiber-loop using a dual-pump configuration and colour coding

In this paper, we propose a new Brillouin Optical Time Domain Analysis (BOTDA) set-up that combines simultaneous Brillouin gain/loss measurements with colour coding. This technique gives the advantage that the pump power can greatly be increased, compared to other coding schemes, thus increasing the sensing range. A measurement over a 200 km fiber-loop is performed, with a 3 meter spatial resolution and an accuracy of ± 3 MHz (2σ) at the end of the sensing fiber. To the best of our knowledge, this is the best result obtained with a Brillouin sensor without Raman amplification.