This research concerns the issues of monitoring in the physical channels optical access networks. This is relevant because automated diagnostic and monitoring systems in passive optical networks (PONs) are not available at the moment. The authors discuss the technique for monitoring physical channels of the tree to-pology in PONs by Brillouin optical time domain analysis (BOTDA) using end reflections. The paper analyses the main factors affecting the transmission and mechanical characteristics of the optical fiber, presents the results of the comparative analysis of optical fiber deformation measurement methods, and justifies the appli-cation of the technique based on the principles of Mandelstam-Brillouin scattering. Also, it provides the the-oretical basis and the calculated relations, which allow us to evaluate the main functional capabilities of BOTDA reflectometry. The feasibility of monitoring the physical channels of the tree topology of the optical access network by Brillouin analysis in the time domain using end reflections is evaluated.