Real-Time, Year-Round, Cross-Arctic Observations Integrating Three Complementary Technologies into Submarine Telecommunication Cables

On-going geopolitical concerns in Eastern and Northern Europe are raising the awareness of the risks to key infrastructure including intercontinental Internet access. To address such concerns mitigation measures considered include adding redundant access paths to eastern Asia, in addition to those in place today. An approach being considered are Arctic ocean-crossing submarine telecommunication cables. This route shortens the distance (i. e., time) between Europe and Asia and because of the dearth of cables in the Arctic, additional applications such as monitoring the environment along the path are under consideration. This contribution highlights three different environmental sensing technologies that can be associated with a submarine telecommunication cable, and particularly with one crossing the entire Arctic Ocean. The first method consists of sensors in repeaters that are components of the submarine telecommunication cable and placed every 100 km or so. The possible sensors must have long design lives, to provide reliable temperature, pressure and accelerometer data in real time. This is the concept of SMART cables, a concept promoted for over a decade by the ocean research community and now enjoying its first initial implementations with two systems to be deployed in 2026 in the Pacific and Atlantic respectively, following an on-going test in the Mediterranean. SMART cables are now recognized as an emerging network of GOOS, the Global Ocean Observing System. The second method uses recent developments in distributed acoustic sensing (DAS), a method that can precisely pinpoint changes in the strain of an optical fibre by illuminating it with short laser pulses and “interrogating” the reflected signal to measure changes over time and quantify vibrations. This method has been demonstrated to work well over fibre lengths spanning over 100 km. On-going developments by Alcatel Submarine Networks will allow the concept to be generalized on longer cables by providing DAS over many 150 km cable segments, thereby allowing acoustic/seismic sensing in real-time along thousands of kilometres of cable. The third method adds branching units and spur cables along the main route of the telecom cable that feed power and communication capabilities to instrument platforms. This method has been demonstrated for almost 20 years with the Ocean Networks Canada's VENUS and NEPTUNE observatories, and with the US Ocean Observatory Initiative's Regional Cabled Array in the Pacific Ocean. In the case of an Arctic crossing cable, given the need to re-power it mid-way to enable its repeaters over such a large distance, a branch of F the main cable needs to land in a northern community where a shore station provides additional power. This shore station also provides a point of presence for adding network routes to North America. Each branching unit and spur would host nodes with a complex array of instruments and sensors, similar to the NEPTUNE observatory that supports research in many ocean disciplines. The three approaches are complementary: the SMART cable provides accurate data at specific points along the cable. The DAS-enabled cable provides sensing of strain at some level of sensitivity but at a high spatial resolution along the cable. The branching unit-and-spur approach allows for the support of the broadest range of Arctic science disciplines as the nodes can support any and all types of underwater fixed and mobile platforms with sensors for marine biology, ocean chemistry, physical oceanography, geophysics and sensors for hazard alerting (tsunami and earthquakes). The common benefit of all of these approaches are their real-time capabilities.