A Scalable Data Collection System for Continuous State of Polarisation Monitoring.

Our dependency on the telecommunication infrastructure is continuously increasing, as different infrastructures – such as energy and telecommunication – now have mutual dependencies. This calls for increased monitoring of the fibre network, which is a highly critical part of the infrastructure. State of Polarisation (SoP) of light propagating through fibre transmission systems is impacted by any vibrations and mechanical impacts on the fibre. By continuously monitoring the SoP, any unexpected movements of a fibre along a fibre-path may be traced. Movements may be caused by e.g. work in node-rooms impacting patch-cords, trawlers or other types of sub-sea equipment touching or hooking into sub-sea fibre cables, digging close to a fibre-cable, or geophysical phenomena like earthquakes. In this paper, we describe a low-cost, scalable system for SoP monitoring and give examples of patterns monitored in different types of fibre infrastructures. The monitoring system consists of single-unit rack-mount instruments connected to taps from live optical transmission signals. Each instrument has local storage for 1-2 years of data, and is periodically automatically uploading data to a server for backup and data-access purposes. Examples of observed patterns are impact from a thunderstorm on a Fibre-To-The-Home (FTTH) cable, 50 Hz on a fibre-cable spun around a high-voltage power air-cable, as well as animal impact on a patch-cord.