Simple method for the elimination of polarization noise in BOTDA using balanced detection of orthogonally polarized Stokes and anti-Stokes probe sidebands

Abstract

Given the strong polarization sensitivity of Stimulated Brillouin Scattering (SBS), in Brillouin Optical Time Domain Analysis (BOTDA) it turns out to be indispensable to perform some kind of polarization scrambling, either in the pump pulse, or the probe signal (or both). This is usually accomplished using polarization scrambling/switching systems, which, being mechanical, tend to be not as robust as it would be desirable. In this paper we propose a completely passive system, with no moving parts, to perform the polarization scrambling in a BOTDA. It is based on the use of balanced detection among the orthogonally polarized Stokes and anti-Stokes bands of the probe signal. The setup requires no alignment and provides a performance similar to a conventional BOTDA sensor