VIAVI Brillouin OTDR: Telecom Optical Networks Use Cases

Abstract:
Brillouin Optical Time Domain Reflectometers (BOTDR) uniquely allow to analyze how strain or temperature distribute along and affect an optical fiber over tens of kilometers. This type of measurement is nowadays employed for factory testing during development or qualification of optical cables, before and after installation, for troubleshooting of a failing installed cable, and for field temperature or strain long-term monitoring. VIAVI designed an innovative BOTDR that can uniquely measure both strain and temperature simultaneously, by acquiring both the Rayleigh and Brillouin back-scattering on the same fiber. The combination of Brillouin shift and Landau-Placzek ratio readings allows to separate the temperature and strain effects. When an optical telecom cable is deployed, all the steps involved must warrant that the strain along the cable never exceeds its Maximal Allowable Tension (MAT) in order to avoid the cable getting damaged and ending up with a higher probability to fail. Traditional Rayleigh OTDR measurements are not able to provide useful information about the fibers tensile mechanical loads. Strain measurements using a Brillouin OTDR can instead map the structural health of the fibers in a cable. This work describes the VIAVI instrument features, and the data acquired by telecom operators around the world for underground, aerial and submarine field networks.