The announcement of the Autonomous Systems Industry Alliance (ASIA) under the US-India COMPACT (Catalysing Opportunities for Military Partnership, Accelerated Commerce & Technology) for the 21st Century signals the development of closer Indo-US defence industrial ties especially in the maritime domain.[1] Key identified technologies include the co-development of active towed array systems, unmanned surface vehicle systems, sonobuoys, and autonomous undersea vehicles, including wave gliders.[2] All this has been interpreted as a manifestation of greater Indo-US cooperation in enhancing underwater domain awareness (UDA), given the central role these technologies play in “sense-making” — particularly within the underwater environment. This is unsurprising as UDA has garnered much attention within Indian policy and defence circles. The Indian Navy, in particular, had made UDA one its key focus areas of the Indian Navy in 2020 itself.[3] In addition to these technologies, distributed acoustic sensing (DAS) through submarine communication cables has been gaining increased traction as a measure to not only protect this infrastructure system but also to contribute to enhancing UDA efforts in both civilian and military contexts. This paper seeks to contextualise this discussion of UDA to submarine communication cables.
The paper first outlines how the concept of UDA is expanding to include protection of critical underwater infrastructure. Thereafter, it discusses the concept of distributed fibre-optic sensing, more specifically DAS and its integration into underwater sensing networks. Finally, it discusses the technical, commercial, and regulatory challenges associated with this technology.
UDA for Critical Infrastructure Protection
Underwater Domain Awareness. UDA is the subsea component of maritime situational/ domain awareness (MSA/ MDA).[4] As per the International Maritime Organisation (IMO), MDA is the “effective understanding of anything associated with the maritime domain that could impact security, safety, the economy or the marine environment”[5], which has been contextualised in a war-fighting scenario by the Indian Navy to mean “being cognisant of the position and intentions of all actors, whether own, hostile, or neutral, in all dimensions of a dynamic maritime environment, across the areas of interest.”[6] This requires the ability to i)collect, ii)fuse, iii)analyse, and iv)share data of activities (which includes the position and intention of actors) and its analysis among relevant stakeholders.[7] It must be noted that given the vast expanse and depth of the world’s oceans, attaining complete near real-time domain awareness is nearly impossible at will remain an aspirational goal. Therefore, what is sought to be achieved in more practical terms is underwater situational awareness which allows us to know and understand activities in an identified area of interest over a particular period of time. This requires sustained observation of the underwater environment, a comprehension of the situation obtaining within a given geography, and the projection of an anticipated future status.[8] The current lack of transparency of the underwater domain does not stem from a want of intent or effort but rather from the difficulties offered by the medium itself. The underwater domain is a highly hostile environment with significant challenges of high pressure, corrosion, varying temperature and salinity, lack of availability of power, and high signal-attenuation.[9] This limits the range and accuracy of data transmitted (usually via sound waves).[10] Technological advances seek to mitigate at least some of these challenges and in so doing, to improve range, data integrity, and a maximisation of the time that an asset can spend underwater, that too, at the lowest possible cost.
Application to Underwater Infrastructure. While this framework is predominantly applied to military contexts, there is wide civilian utilisation of this concept, too, especially for entities involved with the blue economy; environment protection and natural-disaster management; and research and development.[11] Even within the military context, UDA has focused primarily on submarine and anti-submarine warfare.[12] Technological development, operational plans, and policy focus, have all been geared towards detection and detection-avoidance in respect of submarines. However, the development-of and reliance-upon underwater infrastructure — such as submarine cables (for the power and communication) and energy pipelines — is rapidly growing in contemporary times, and with which grows the criticality and vulnerability of this infrastructure. There has been a considerable uptick in the disruptions of these cables — most notably in the Baltic Sea — which have had significant geopolitical ramifications.[13] Furthermore, the damage being caused by merchant vessels in circumstances evincing strong suspicions of intentional State-initiated damage, has added deliberate sabotage of cable infrastructure to the threat profile of these systems, which hitherto remained accidental in nature. In response, the North Atlantic Treaty Organisation (NATO) has launched Operation “VIGILANCE ACTIVITY BALTIC SENTRY”, the aim of which is to “improve situational awareness and deter hostile activities”.[14] This objective is sought to be achieved by deploying “additional assets at sea…and below the surface of the sea”, supported by NATO’s “Critical Undersea Infrastructure Network” and its “Maritime Centre for the Security of Critical Undersea Infrastructure”.[15] Effort is also being devoted towards “developing new technologies for surveillance and tracking of suspicious vessels and undersea monitoring”.[16] Information generated is sought to be actively exchanged, incidents tracked and assessed, and best practices shared. This points towards the integration of UDA for undersea infrastructure protection within broader MDA practices.
Current Approach. Although major Information Fusion Centres (IFC) — important players in global MDA efforts — such as IFC Singapore and India’s IFC-Indian Ocean Region (IFC-IOR) display submarine communication cables on their maps, and document cable damage incidents, this is not a focus area for these centres.[17] Moreover, current monitoring mechanisms predominantly rely on Automatic Identification System (AIS) tracking of any suspicious behaviour of surface vessels. While the dragging of anchors by surface vessels has been the preferred modus operandi or at least the predominant cause of damage in recent incidents, surface-based tracking only enables post-facto correlation of vessel location and time of disruption. Therefore, it helps in establishing an audit trail, incorporating the identification of the vessel that has caused the damage but can seldom prevent that vessel from causing any further damage. While suspicious vessel-activity such as movement patterns across cables or the sudden slowing down of vessels may well be monitored, an obvious lacuna in the adoption of this approach is the possibility of the vessel(s) switching-off their AIS transmitters/ transponders or ‘spoofing’ vessel location.[18]
Establishing and maintaining the position and movement of surface vessels by tracking their underwater signatures offers a solution that could supplement or even replace AIS-based tracking. Towards this end, platform/asset-based surveillance is a measure that is already being adopted by States to protect such infrastructure. In this regard, uncrewed underwater vessels (UUVs) are an attractive choice. In addition to NATO’s BALTIC SENTRY programme — which seeks to deploy subsea assets for monitoring and surveillance — the French Seabed Warfare Strategy, too, seeks to develop autonomous underwater vehicles (AUVs) that can dive to significant depths to monitor sensitive installations such as submarine cables.[19] The French strategy identifies technological developments such as magnetic detection (using optically-pumped magnetometers and colour centre detectors) and offer promising surveillance and tracking options.[20] In fact, cable route surveys undertaken during the project planning stage already utilise towed magnetometers to identify the existence of other cables/pipelines along the planned route.
However, a major drawback of platform-based surveillance relates to the limited area in which surveillance can be undertaken at a given time. Thus, while such endeavours may help for near-shore activity (this is, of course, significant, given that multiple cables tend to congregate at select landing points ashore), cable cuts may occur at significant distances along any stretch of the cable’s lengthy traverse. Moreover, even though such surveillance may be useful against underwater vehicles or intelligence-based surveillance by “grey” hulls or “white” ones, damage caused by merchant vessels either intentionally or accidentally, cannot be addressed by surveillance platforms. Since the ordinary length of an anchor aboard a merchant ship is 275 m to 300 m, it is unlikely that cable damage from merchant vessels is going to occur in depths in excess of 300 m, not least because it would take away the deniability feature from accusations of intentional sabotage. The presence of these platforms may act as deterrence especially if coordinated in a manner that manages to cover significant parts of the areas of interest up to a depth of 300 m. While more feasible in smaller bodies of water such as the Baltic Sea, Red Sea, or Mediterranean Sea, the applicability of such approaches in the Arabian Sea or Bay of Bengal are much more complicated, not least due to the sheer size of such seas and bays. These efforts, therefore, need to be complemented with technologies that allow for underwater sensing to enable targeted pre-emptive action for protection.
Fibre Optic Sensing. Fibre-optic sensing, i.e., the utilisation of optical fibres as a sensor to measure physical or chemical quantities is manifesting itself in an increasing variety of applications,[21] many of which allows the optical fibre itself to measure vibrations, temperature, and strain.[22] “Fibre-optic sensing” works on the principle of “Coherent Optical Time Domain Reflectometry” (COTDR) by detecting modulations in the backscatter of a light pulse travelling through the fibre.[23] Light pulses are launched into ‘dark fibres’, i.e., those that are not being utilised for communications, from an interrogator (data acquisition and measurement device)[24] located at the Cable Landing Station ashore. This light pulse is scattered back to the origin due to the heterogeneities in the fibre. The backscattered light is varied by external influences. The phase-changes in the backscattered light are collected and analysed by the interrogator to detect and measure external influences at different points along the fibre.[25] Figure 1 illustrates this mechanism.[26]
Fig 1: Fibre-Optic Sensing
Source: “Distributed Acoustic Sensing”, EarthScope
Sensors may be of two types, namely, “point sensors” or “distributed sensors”. A distributed sensor is one wherein sensing can take place along the entire fibre, as opposed to a point sensor, which can detect only at a single point.[27] Therefore, you can have a distributed temperature sensor (DTS) to detect temperature, distributed acoustic sensor (DAS) for vibrations, and a distributed strain sensor (DSS) for mechanical tension on the fibre. The current state of technology allows for a single fibre to measure for a single physical quantity at a time. Therefore, different fibres would need to be utilised for temperature, strain, and vibrations.
The utilisation of this technology for the protection of subsea communication cables is gaining traction. Cable manufacturing companies are actively promoting the utilisation of DAS technology on cables as part of an early-warning system to allow for preventive action against cable damage. Private enterprises seek to prevent damage against trawl activities, anchoring, and dredging activities.[28] As soon as a trawl or anchor begins to drag along the sea floor, acoustic waves generated from these impacts will strain the optic fibre. The interrogator will be able to localise the strain and indicate to the network operator the location of the disturbance. The network operator will then be able to correlate this information with AIS data to identify the vessel and arrive in a position where he/she can take preventive action.[29] Potential mechanisms could include sharing this information with relevant information fusion centres, port authorities, fishery organisations, and even defence forces, to intimate the vessel operator or mobilise assets in the vicinity in case of a severe threat. Importantly, the information about this threat would be received even if the vessel of concern is not transmitting on AIS.
UDA by Submarine Communication Cables
Environmental Monitoring. The applications of underwater fibre-optic sensing can extend even beyond the safety and security of the fibre-optic cable itself. Concerted efforts are being made to develop and integrate SMART cables, i.e., telecom cables installed or upgraded for “Scientific Monitoring and Reliable Telecommunications”.[30] These include hazard-monitoring sensors that can read and record data relating to pressure, temperature, seismic activity, etc. While several models of sensor-instalment are available, they are usually installed in the repeaters of the optic fibre cable.[31] Therefore, in addition to providing telecom services, these cables can read physical values underwater and transmit them back to the landing station. The primary attractiveness of installing such sensors on these systems is that much of the cable infrastructure has already been laid and the cables merely need to be upgraded for sensing. Further, the operational cost of the cable system is covered by the revenue-generating telecom business. Given the cost and time efficiencies associated with utilising cables for creating a real-time ocean observation network, the International Telecommunication Union (ITU), the UNESCO-Intergovernmental Oceanographic Commission, and the World Meteorological Organisation, have jointly established a task force to develop standards and promote the adoption of these cables.[32] As such, even dedicated sensing cables are now actively being adopted by ocean scientific research bodies and authorities across the world, replacing buoys, gliders, and autonomous vehicles, for wider basin coverage at a fraction of the cost.[33]
This project focuses on a series of point sensors along the cable rather than distributed fibre-sensing described above. This may be because installing sensors on repeaters is more cost effective than utilising a dedicated dark fibre for sensing. Additionally, crosstalk between muti-parameter sensing and telecom data precludes a single fibre being used for both activities.[34] Fibre-optic sensing for ambient underwater environment sensing has obvious applications in navigation, earthquake/tsunami early-warning, and marine biological studies.[35] Of particular interest is the application of DAS for ship detection and communication between assets at sea and facilities ashore. Given the inherently dual-use application of underwater technologies, a military utilisation of such capability is very plausible. In fact, a deep-sea observation network has already been envisaged through the integration and networking of DAS, space, and surface assets.[36]
Vessel Identification. In 2021, a study utilised a 41.5 km long cable off France to detect a tanker first 5.8 km offshore in 85 m depth, and then 20 km offshore at 2,000 m depth.[37] While the signal-to-noise ratio was better at the shallower depth, low frequency signals below 50 Hz were detected even at 2,000 m. Research has further advanced and is currently focused upon target localisation (including range and bearing) of the vessel and classification (developing a means to identify the type of the vessel).[38] Efforts have also been made to improve localisation efforts, identify vessel velocity, improve the spatial resolution of detection, and compare the impact of varying ‘field conditions’ on collected data.[39] Additionally, investment in signal-processing technology, aided by the development of artificial intelligence/machine learning (AI/ML) and its training in the analysis of specific sound signatures can assist in identifying vessels of interest, in addition to improving the signal-to-noise ratio.
Not only is fibre-optic sensing technology improving, but advancements are also being made in fibre technology itself. Most notable is the emergence of multicore fibres — a first trial in respect of which was completed by NEC (Japan) in 2021 — which not only enables multiple signals to be transmitted through different cores of the same fibre but also enables multipurpose systems to run over a single fibre. Thus, communication, acoustic sensing, temperature sensing, and power over optic fibre, may well be simultaneously realised.[40] While not within the scope of this paper, multicore fibres are likely to revolutionise deep-sea observation systems and seabed warfare capabilities. It also makes it easier to realise a “pit stop” for AUVs to charge and upload their data simultaneously.
Communications. A major challenge in achieving UDA is the attenuation of signals underwater, severely limiting the range of communications. Communication with entities located ashore involves the surfacing of the vehicles at sea in order to create a satellite link or the use of surface buoys. However, high data-collection costs and sparse distribution of such nodes have prompted research in alternative shore-to-asset communication methods. DAS technology has been promising in facilitating near real-time acoustic communication. A recent experimental study managed to transmit acoustic communication packets at a range of 200-500 metres from the source, at a frequency up to 2 kHz.[41] This study also identified that time-gating at the interrogator could allow multiple platforms to transmit simultaneously enabling the creation of a more effective underwater network — without packet collision.[42] Researchers are also testing two-way communications using DAS technology. Bidirectional communication between a shore-station and an AUV has been demonstrated, with DAS enabling uplink communication between the AUV and the shore station, and with downlink communication between the shore station and the AUV occurring using a quantum magnetometer.[43] This creates a communication loop and extends the range and flexibility of AUVs.
Therefore, not only is fibre-optic sensing technology of value to the cable itself but also has a host of applications in achieving underwater domain (spatial) awareness.
Challenges
While the application of this technology is undeniably promising, there is no gainsaying that major challenges remain.
Nascent Technology. The technology currently is at a very nascent stage. While it demonstrates a great deal of promise, currently even state-of-the-art technology only enables cable monitoring up to a maximum of 100-150 km from the interrogator.[44] This coincides with the location of the first repeater. Research is also underway to develop optical repeaters that can manage DAS signals in addition to data signals. While “OptoDAS”, which is a tool developed by “Alcatel Submarine Network”, claims to detect gear (such as a ship’s anchor) hitting the seabed from 2 km away, the location of the source would require triangulation, for which the cables in the vicinity, too, need to be DAS-enabled. The range along the cable across which the disturbance is felt is what the DAS interrogator would be able to depict. The advancements discussed above, where researchers have identified the range and bearing of the vessels, is through targeted beamforming to demonstrate this possibility.
UDA applications of DAS are at an even more nascent stage with issues of range and frequency persisting. Field trials in the open domain point to experiments done with objects in proximity to the interrogator and cable at a low frequency. Moreover, DAS is a passive sensor, which may limit its range and utilisation. In the Indian Ocean, an additional challenge is the high levels of medium- and low-frequency noise generated by merchant shipping activity.[45] Hence, there is still a long way to go for the technology to be mature enough to be adopted and deployed for UDA. However, this also presents an opportunity. There is a disconcerting lack of literature from Indian academia in this domain. A majority of the research available in the open domain is being conducted by Chinese or European universities, often involving significant grants from governments. Consequently, there needs to be investment in developing this technology further, especially given the potential and demonstrable benefits.
Privately-owned infrastructure. A major assumption while calculating the cost and time efficiencies of enabling DAS on submarine cables is the fact that the operators of these cables will permit such installation. Most global submarine communication-infrastructure is privately owned and, therefore, operator consent will be a critical aspect for the utilisation of this technology. Given the added challenges in other jurisdictions that these cable projects may face, many private operators may refuse consent. This would then require the placement of fresh cable projects for UDA purposes, which will negate the cost and efficiency that would accrue from using DAS. A State could, in theory, mandate that a fibre be given to the defence agencies, particularly the Navy, as a part of the ILD license issued to the telecom provider. Further, Section 21 of the Government of India’s “Telecommunications Act, 2023”, once notified, would give the Central government the power to notify the use of telecommunication equipment as necessary in the circumstances.[46] This, however, may prove counterproductive as it will probably hamper, if not prevent, the development of new cable projects and the establishment of data centres in India, as the two sectors are inherently linked.[47] Moreover, assuming that a private operator does consent to the installation of an interrogator, legal issues of data handling, data ownership, and data access will also arise. The ability to sell this data, manner of storage, and data sharing mechanisms between the enterprise and the State will have to identified and secured.
Militarisation of Private Infrastructure. The militarisation of private infrastructure can give rise to issues of souring business-State (B-to-G) relationships, increasing the difficulty in securing private sector collaboration — especially during conflict — and the utilisation of private infrastructure for deriving profit from conflict or to gain political favour in certain jurisdictions.[48] This is especially true for transnational infrastructure such as submarine cables.
Additionally, there is also the argument that enabling sensing on cables will make them more likely to be disrupted.[49] However, underwater infrastructure, especially submarine cables have been a target in times of conflict ever since the Spanish-American War of 1898 and leading up to the First and Second World Wars.[50] Therefore, utilising cables as sensors does not necessarily increase these chances. It is also feasible to argue that enabling DAS on cables may prevent their disruption even if intentionally targeted. This may even prevent such attacks as a proven intentional attack may exceed the threshold of conflict.
Regulatory Challenges. In addition to the rules related to data collection, processing, storage and distribution, DAS-enabled cables will require explicit coastal State approval before they can be installed. This will not only involve telecom regulatory authorities but even the defence forces of the State. Given consortium ownership structures, States may be even more apprehensive of permitting DAS enabled cables involving companies owned by potential adversary States. Further, even if one coastal State has given permission for DAS enabled cables, permits may well be required from others States through whose EEZ the cable may pass. They would be well within their right to regulate this activity as it may be classified as “marine scientific research” within the regulatory ambit United Nations Convention on the Law of the Sea 1982 (UNCLOS 1982). There are additional challenges from the perspective of the coastal State through whose EEZ such cable may pass but which may be unaware that such a cable is DAS-enabled. Each of these several facets requires a series of detailed research-studies by institutions — especially maritime-focused ones such as the NMF.
In sum, India must begin the process of creating/ developing and then adopting a regulatory framework for DAS-enabled cables, especially since the technology has become available and is actively being pursued by private entities. Even if it chooses to prohibit the connection of DAS-enabled cables to the Indian network, a formal policy needs to be enacted.
Recommendations
In essence, the application of DAS technology for the protection of submarine cables is being actively pursued by cable manufacturers and cable operators. This technology also has applications for enhancing underwater spatial awareness across civilian and military contexts. With respect to enhancing UDA for submarine cable protection, India needs to facilitate interactions between cable operators and the IFC-IOR, the Information Management and Analysis Centre (IMAC), and the Navy’s Maritime Operations Centres (MOCs) to allow the near real-time sharing of fault and AIS data. IFC-IOR should also explore possible data-sharing agreements with potential DAS enabled cables in its area of interest and prepare protocols for preventing any activity which may damage cables in its area of interest.
Indian academia and maritime-focused policy-relevant think-tanks such as the NMF certainly need to lay greater focus upon developing underwater fibre optic sensing technology, which should be aided by the Indian State. Further, regulatory bodies in India need to develop a policy and eventually a regulatory framework for DAS enabled cables. Technology is leapfrogging in this space, and it is imperative that India keeps pace.
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About the Author:
Mr Soham Agarwal, a Delhi-based lawyer, holds a Bachelor of Law (Honours) degree from the University of Nottingham, UK. He is currently an Associate Fellow with the Public International Maritime Law Cluster of the National Maritime Foundation, New Delhi. His research, which is focused upon issues relevant to the seabed, maritime infrastructure, and seabed warfare, is rapidly gaining international traction. He may be contacted at law10.nmf@gmail.com
Endnotes:
[1] Prime Minister’s Office, India – U.S. Joint Statement during the visit of Prime Minister of India to US, 14 February, 2025 https://pib.gov.in/PressReleaseIframePage.aspx?PRID=2103037
[2] Dinakar Peri, “India, U.S. identify underwater domain awareness technologies for co-production in India”, The Hindu, February 15, 2025. https://www.thehindu.com/news/national/india-us-identify-underwater-domain-awareness-technologies-for-co-production-in-india/article69223304.ece
[3] Huma Siddiqui, “Underwater domain awareness main focus of the Indian Navy: Chief”, Financial Express, December 2020 https://www.financialexpress.com/business/defence-underwater-domain-awareness-main-focus-of-the-indian-navy-chief-2142665/
[4] Dr. Prakash Panneerselvam, “India and Australia: The Need For Strategic Cooperation In Underwater Domain Awareness”, Policy Brief, Australia India Institute, November 2023 http://eprints.nias.res.in/2653/1/AII_StrategicCoop_Brief.pdf
[5] “Maritime Domain Awareness”, International Maritime Organisation https://www.imo.org/en/OurWork/Security/Pages/Maritime-Domain-Awareness.aspx#:~:text=Maritime%20Domain%20Awareness%20(MDA)%20is,economy%20or%20the%20marine%20environment.
[6] Indian Navy, Ensuring Secure Seas: Indian Maritime Security Strategy, (New Delhi: Integrated Headquarters of Ministry of Defence (Navy), 2015), 165 https://bharatshakti.in/wp-content/uploads/2016/01/Indian_Maritime_Security_Strategy_Document_25Jan16.pdf
Also See: Captain Himadri Das, “Maritime Domain Awareness in India: Shifting Paradigms”, National Maritime Foundation, 30 September 2021 https://maritimeindia.org/maritime-domain-awareness-in-india-shifting-paradigms/#_ftn2
[7] Joseph L Nimmich and Dana A Goward, “Maritime Domain Awareness: The Key to Maritime Security”, International Law Studies, Volume 83, https://digital-commons.usnwc.edu/cgi/viewcontent.cgi?article=1160&context=ils
[8] Pedro Patron and Yvan R Petillot, “The Underwater Environment: A Challenge for Planning”, Association for the Advancement of Artificial Intelligence, 2008. https://www.macs.hw.ac.uk/~ruth/plansig08/ukplansig09_submission_21.pdf
[9] Ibid
[10] Abijit Singh, “The Promise and Pitfalls of Underwater Domain Awareness”. War on the Rocks, February 10, 2023 https://warontherocks.com/2023/02/the-promise-and-pitfalls-of-underwater-domain-awareness/
[11] Cdr (Dr) Arnab Das, “Underwater Domain Awareness (UDA) Framework”, Maritime Research Centre, https://maritimeresearchcenter.com/wp-content/uploads/2024/04/Underwater-Domain-Awareness.pdf
[12] Dr. Prakash Panneerselvam, “India and Australia: The Need for Strategic Cooperation In Underwater Domain Awareness
[13] Katharina Buchholz, “Baltic Sea Cable Incidents Pile Up”, Statista, February 06, 2025 https://www.statista.com/chart/33892/damage-to-underwater-cables-and-pipelines-in-the-baltic-sea/
[14] Office of the President of the Republic of Finland, “Joint Statement of the Baltic Sea NATO Allies Summit”, January 14, 2025 https://www.presidentti.fi/joint-statement-of-the-baltic-sea-nato-allies-summit/
[15] Ibid
[16] Ibid
[17] “Visit to the Information Fusion Center Singapore”, Christian Bueger, July 28, 2024, https://bueger.info/visit-to-the-information-fusion-center-singapore/
[18] AK Chawla (Vice Admiral) and Commodore Gopal Suri, “Maritime Domain Awareness in the Indo-Pacific and the Way Ahead for Indo-Pacific Partnership for MDA”. Vivekananda International Foundation, June 27, 2023 https://www.vifindia.org/article/2023/june/27/Maritime-Domain-Awareness-in-the-Indo-Pacific-and-the-Way-Ahead
[19] Seabed Warfare Strategy, (French Ministry of Armed Forces, 2022) https://www.archives.defense.gouv.fr/content/download/636001/10511909/file/20220214_FRENCH%20SEABED%20STRATEGY.pdf p35
[20] Ibid
[21] Vit Novotny et al, “Fiber Optic Based Distributed Mechanical Vibration Sensing”, Sensors 21(14), (2021) https://www.mdpi.com/1424-8220/21/14/4779
[22] “Optical Fiber Sensing”, NEC, last accessed February 28, 2025, https://www.nec.com/en/global/solutions/ofs/index.html
[23] Vit Novotny et al, “Fiber Optic Based Distributed Mechanical Vibration Sensing
[24] “Optical Interrogators”, Hottinger Bruel & Kjaer, last accessed February 28, 2025 https://www.hbkworld.com/en/products/instruments/daq-systems/optical-interrogators
[25] Wei Huang et al, “Experimental Study on Optoelectronic Submarine Cable Used for Ship Radiation Noise Detection”, IEEE Access, 18 December 2024 https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10806696
[26] “Distributed Acoustic Sensing”, EarthScope, last accessed February 28, 2025, https://www.earthscope.org/what-is/das/
[27] Vit Novotny et al, “Fiber Optic Based Distributed Mechanical Vibration Sensing
[28] “Subsea Cable DAS Applications” ASN, last accessed February 28, 2025, https://www.asn.com/subsea-cable-das-applications/
[29] Ibid
[30] ITU News, “Submarine telecom cables enhance climate monitoring and tsunami forecasts”, International Telecommunication Union, June 08, 2022 https://www.itu.int/hub/2022/06/submarine-cables-telecom-climate-monitoring-tsunami-forecasts/
[31] International Telecommunication Union, “Scientific monitoring and reliable
telecommunications submarine cable systems”, Recommendation ITU-T G.9730.2, August 2024
[32] “SMART Cables”, Smart Cables, last accessed February 28, 2025, https://www.smartcables.org/
[33] Ibid n30
[34] Yujian Guo et al, “Submarine Optical Fiber Communication Provides an Unrealized Deep-Sea Observation Network”, Scientific Reports 13, 15412, 18 September 2023. https://www.nature.com/articles/s41598-023-42748-0
[35] M Landrø et al, “Sensing whales, storms, ships and earthquakes using an arctic fibre optic cable”, Scientific Reports 12, 19226, 10 November 2022 https://www.nature.com/articles/s41598-022-23606-x
[36] Yujian Guo et al, “Submarine Optical Fiber Communication Provides an Unrealized Deep-Sea Observation Network”
[37] Diane Rivet, “Preliminary Assessment of Ship Detection and Trajectory Evaluation Using Distributed Acoustic Sensing on an Optical Fiber Telecom Cable”, Journal of the Acoustical Society of America, 149, (2021) https://pubs.aip.org/asa/jasa/article-abstract/149/4/2615/1067853/Preliminary-assessment-of-ship-detection-and?redirectedFrom=fulltext
[38] Wei Huang et al, “Experimental Study on Optoelectronic Submarine Cable Used for Ship Radiation Noise Detection”, IEEE Access, 18 December 2024 https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10806696
[39] Bob Paap et al, “Leveraging Distributed Acoustic Sensing for Monitoring Vessels Using Submarine Fiber-Optic Cables”, Applied Ocean Research 154 16 January 2025 https://www.sciencedirect.com/science/article/pii/S0141118725000100
[40] Yujian Guo et al, “Submarine Optical Fiber Communication Provides an Unrealized Deep-Sea Observation Network
[41] John Potter, “First demonstration of underwater acoustic communication from sea to shore via an optical fibre using Distributed Acoustic Sensing, ESS Open Archive, 05 July 2024 https://essopenarchive.org/users/550690/articles/1156752-first-demonstration-of-underwater-acoustic-communication-from-sea-to-shore-via-an-optical-fibre-using-distributed-acoustic-sensing
[42] Ibid
[43] Shaojian Yang, “Integrated Acoustic-Optic-Magnetic Sensing: Enabling Telemetry via Submarine Cables”, IEEE Sensor, October 2024 https://ieeexplore.ieee.org/document/10785216
[44] Morten Eriksund, “Protecting submarine cables for enhanced connectivity”, Open Access Government, April 12, 2023 https://www.openaccessgovernment.org/article/protecting-submarine-cables-enhanced-connectivity-subsea/155612/
[45] Arnab Das, “Underwater radiated noise: A new perspective in the Indian Ocean region”, Taylor & Francis, June 25 2019 https://www.tandfonline.com/doi/abs/10.1080/09733159.2019.1625225
[46] S21 of the Telecommunication Act 2023 https://egazette.gov.in/WriteReadData/2023/250880.pdf
[47] https://www.nitiforstates.gov.in/policy-viewer?id=PNC510C000384
[48] Joscha Abels, “Private infrastructure in geopolitical conflicts: the case of Starlink and the war in Ukraine”, European Journal of International Relations, Volume 30 Issue 4, June 2024 https://journals.sagepub.com/doi/10.1177/13540661241260653
[49] Bronte Munro and Iain MacGillivray, “Reconsider Using Undersea Cables as Military Sensors”, National Defense, September 29, 2023 https://www.nationaldefensemagazine.org/articles/2023/9/29/reconsider-using-undersea-cables-as-military-sensors
[50] Jonathan Reed Winkler, “Silencing the Enemy: Cable-cutting in the Spanish American War”, War on the Rocks, November 6, 2015 https://warontherocks.com/2015/11/silencing-the-enemy-cable-cutting-in-the-spanish-american-war/
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