Distributed Sensing Based on Interferometry and Polarization Methods for Use in Fibre Infrastructure Protection

Abstract

Fibre optic infrastructures are very important, and therefore, it is necessary to protect them from fibre cuts. Most fibre cuts are caused by digging activity, and many network operators seek appropriate solutions enabling detection of possible unexpected events (predict these cuts) and subsequent network outages. In most cases, there is no need to locate events, and only information regarding the occurrence of the event is sufficient. Direct detection-based distributed fibre optic sensing systems appear to be an appropriate solution, allowing digging to be detected before the fibre breaks. The average power of such signals is relatively small, and there is no interference with other signals in the fibre. We performed laboratory measurements to compare the sensitivity and accuracy of interferometric and polarization systems for acoustic vibrations. In the case of interferometric systems, the reference and sensing arms were in the same cable, and both were subjected to acoustic vibrations.

Classification of Events Violating the Safety of Physical Layers in Fiber-Optic Network Infrastructures

“…An example of the enhanced sensitivity of interferometers is provided in [ 18 ] by comparison to the sensitivity of polarization detection, which constitutes another large group of sensing techniques based on the detection of polarization changes in a fiber. For example, polarization analysis can be performed using polarization-sensitive optical time domain reflectometry (POTDR) based on Rayleigh light scattering [ 19 ].…”