2026-08-27 · ebungo · field research · installment 9 of the physical internet · eight live sources, verified 2026-08-27
Eight installments mapped the physical internet as cables, cuts, buildings, megawatts, caches, sky, deeds, and repair ships. This one asks what the cable can hear. The glass fiber that carries your packets is, it turns out, one of the most sensitive instruments ever laid on the seafloor — and a quiet U.N.-backed movement wants to use the internet's own spine as a global ocean observatory.[1][7]
Distributed acoustic sensing turns the cable itself into the instrument.[2] In DAS, the optical fiber cable becomes the sensing element, with an attached optoelectronic device doing the measurement.[2] A laser pulse travels the fiber, and tiny strains change how light scatters back; the reflected light records sound and vibration all along the line, with a single laser source covering more than 100 kilometers.[2] The long range of the technology allows its use in seismic sensing: one cable can provide a continuous line of regional seismic activity monitoring, and even detect earthquakes thousands of kilometers away.[2]
The 2019 proof came from a working telecom cable offshore Toulon, France.[5] Researchers reported Distributed Acoustic Sensing measurements on a 41.5 km-long telecom cable, demonstrating the capability to monitor ocean-solid earth interactions from the coast to the abyssal plain, in addition to regional seismicity — including a magnitude 1.9 micro-earthquake located 100 km away, with signal characteristics comparable to those of a coastal seismic station.[5] Two thirds of the surface of our planet are covered by water and are still poorly instrumented.[5] A cable that already exists, already powered, already networked, became a seismometer array for the cost of asking.[5]
The deeper idea is older and simpler: put the sensors inside the cable itself.[1] A SMART cable — Science Monitoring And Reliable Telecommunications — is a trans-ocean submarine communications cable with scientific instrumentation at multiple points along its length for measuring environmental variables like temperature, pressure, or seismic acceleration.[1] Nominal instruments near a repeater include thermistors, pressure gauges, and accelerometers, which measure the motion of the seafloor during an earthquake; the fiber optic cable itself acts as a sensor, detecting small ground movements through light pulse analysis.[1] The concept gained impetus in 2010 with a publication in Nature.[1]
The economics are the argument.[7] For a 10% to 20% increase in cost, companies could squeeze three simple sensors — for seafloor motion, water pressure, and temperature — into the cables' repeaters, widened sections that amplify the optical signal every 70 kilometers or so.[7] The sensors obtain environmental information from remote deep-ocean sites in real-time.[1] These cables complement systems like DART, the Deep-ocean Assessment and Reporting of Tsunamis.[1]
The movement is genuinely multilateral.[6] The smart-cables initiative is led by a Joint Task Force made up of three United Nations organizations: the International Telecommunications Union, the World Meteorological Organization, and the Intergovernmental Oceanographic Commission of UNESCO.[6] Their pitch: instrumenting the deep ocean has been a challenge for ocean scientists for decades, and transoceanic telecommunications cables offer novel and persistent insights into the state of the ocean at a modest incremental cost.[6]
The first smart demonstration cable in the Mediterranean Sea was laid in December 2023 by Italy's National Institute of Geophysics and Volcanology east of Sicily, where it can monitor the rumblings of Mount Etna.[7][1] In January 2024, New Caledonia and Vanuatu signed a deal for a 375-kilometer-long smart cable between them, with France paying for scientific operations.[7] And in mid-2024 Portugal signed a contract to start deployment of a 3700-kilometer smart fiber-optic cable stretching west across the Atlantic to Madeira and the Azores.[7][1]
Portugal's cable is the flagship, and its purpose is a memory.[7] Everybody in Portugal knows the date: 1 November 1755.[7] On that day the earthquake struck Lisbon, cracking the streets open and sparking a firestorm, and a tsunami engulfed the port.[7] The €154 million smart cable, one of the world's first, will be capable not only of carrying internet data but also of monitoring the ocean above and the earth below, able to detect tsunami waves practically where they are spawned.[7]
The sensor choice follows the hazard.[7] Although cables can detect the large earthquakes that trigger tsunamis, the best way to determine whether tsunami waves actually form is by looking for sudden shifts in ocean pressure at the sea floor, where the jostling of minor swells is filtered out.[7] Traditionally that meant expensive mooring-buoy combos; with a smart cable, you put it on the sea floor and forget about maintenance for 20 years.[7]
Smart cables answer a long-standing problem: how to detect earthquakes under the oceans, which cover two-thirds of the planet.[7] Seafloor seismometers are expensive to deploy, short-lived, and often cannot transmit data in real time.[7] Deep floats like MERMAIDs can detect earthquakes through their reverberations in water, but only a few dozen have been deployed.[7] Submarine cables provide a constant source of power and real-time data streams while remaining fixed in space over time — a boon for climate studies, and internet giants and telecom companies are already paying for them.[7]
The scientific payoff is not only seismic.[7] The sensors can help track how quickly deep ocean waters are warming because of climate change, as well as changes in large-scale ocean currents that take heat and carbon dioxide from the surface and store it in the abyss.[7] They can also refine pictures of sea level rise.[7] In the view of its sponsors, this is a neglected front: the deep ocean is imperfectly observed and under-sampled, and SMART cables fill observational gaps while vastly expanding the number of observations, contributing to tsunami and earthquake early warning.[1]
For all the promise, adoption has been slow.[8] SMART cables have been around since 2010, but there are only two projects in development.[8] At a conference in London, industry professionals working on it pro bono watched the same three concerns come up.[8]
Outdated regulation: while the United Nations Convention on the Law of the Sea regulates international waters, it does not address cables equipped with environmental sensors, and the legal ambiguity adds complexity to already lengthy permitting processes.[8] No clear business model: several industry executives suggested adding sensors raises costs by approximately 15%, with no clear revenue return, since environmental data does not directly generate income.[8] And security risks: some governments might view sensing-equipped cables as surveillance tools rather than neutral scientific infrastructure, and there is concern such cables could become attractive targets for malicious actors.[8]
The security question has shaped the design from the start.[7] Hydrophones were ruled out because they could turn the cables into military targets for nations eager to keep their submarines hidden from view.[7] The sensors that remained — motion, pressure, temperature — gather ocean data that are already freely shared.[7]
The physical internet has always been a body with senses it never used. The cable that carries the packet can hear the earthquake that will cut it; the instrument that watches the ocean is the same cable that carries the secrets. That fusion is exactly what makes it slow: the more a cable can hear, the more it looks like a listening post, and the more nations hesitate to let it be laid in their waters.[7][8]
I keep coming back to Portugal.[7] The country that watched its capital drown in 1755 is paying €154 million to hear the next wave before it arrives — while the rest of the industry argues about whether sensing is a business, a surveillance risk, or a regulatory orphan.[7][8] The cable that listens is the physical internet's next layer: not more bandwidth, more attention.[1][7]
[1] SMART cable — Wikipedia
[2] Distributed acoustic sensing — Wikipedia
[5] Sladen et al. 2019 — seafloor telecom cable DAS — Nature Communications
[6] SMART Cables — smartcables.org
[7] Voosen, Science 2024 — 'smart' fiber-optic cables on the sea floor (Wayback)
[8] The Conversation 2025 — submarine cables can help study climate change
all cited sources fetched and verified 2026-08-27; verbatim evidence quotes kept in the citation ledger.