FEATURE
SUBOPTIC 2023 BEST POSTER AWARD
COMPARING SENSITIVITY OF STATE OF POLARIZATION MONITORING AND DISTRIBUTED ACOUSTIC SENSING IN THE SVALBARD ARCTIC SUBMARINE COMMUNICATION CABLE By Kristina Shizuka Yamase Skarvang (NTNU), Steinar Bjørnstad (Tampnet), Robin André Rørstadbotnen (NTNU), Kurosh Bozorgebrahimi (SIKT), Jan Kristoffer Brenne (ASN), Dag Roar Hjelme (NTNU)
ABSTRACT
The existing optical fiber telecommunication infrastructure is an attractive alternative for creating a global geophysical activity sensing network. This paper compares State of Polarization (SOP) sensing and Distributed Acoustic Sensing (DAS) in a field measurement on a telecommunication cable in Svalbard, Norway. SOP sensing is used on an alien wavelength in a live single-span passive submarine cable communication system. Unlike DAS, direct physical fiber perturbation is measurable without saturating, while distributed signals from earthquakes are still measurable. The combined environmental and background noise limits the minimum detectable SOP variations to corresponding to signals from ML 2-3 earthquakes in our infrastructure.
1. INTRODUCTION
Sub-sea fibre telecommunication infrastructures are spanning the world. Additional utilization of this telecommunication network for monitoring environmental and geophysical parameters is attractive as it enables high granularity worldwide monitoring. Using Distributed Acoustic Sensing (DAS), detecting phase changes in a back-reflected signal is a well-established technique. Various studies have
demonstrated submarine sensing of both earthquakes, ship passing, and whale soundings [1]. However, DAS systems currently have a range constraint of approximately 150 km [2]. The SOP of an optical signal in a fiber cable is susceptible to mechanical disturbance brought on by geophysical vibrations. In [3], where a long active subsea cable of 10,000 km was used, SOP-based sensing was used to detect earthquakes as well as ocean swells. The work demonstrated that
Figure 1: Schematic setup of the field setup and the map of Svalbard where the cable is placed.
68 SUBMARINE TELECOMS MAGAZINE