On 30th June Total Telecom hosted an online panel on “Building the submarine networks of the future with SMART (Science Monitoring and Reliable Telecommunications) cables” in partnership with the Joint Task Force on SMART Cables. The session comprised of a number of short presentations from both ongoing and proposed projects as well as a lively panel discussion centring on protecting the interests of commercial cable owners, the need for collaboration between interested parties and key learnings from current projects. Click here to watch the session in full.

A large number of audience questions were received during the session – far too great a number to answer live. As such, the presenters have compiled a list of top questions from the webinar which they’ve collectively answered. You can read their responses below.  


 Have we thought about distributed acoustic sensing (DAS) as another type of sensing, or other optical sensors rather than the typical electro-mechanical pressure sensors or thermistors? I thought that there was a limitation to the robustness of currently available off-the-shelf sensors – can they actually stay down at the bottom of the ocean for 25 years without maintenance?
DAS is seen as a complementary technology.  Implementing DAS is much less intrusive and valuable seismic data can be obtained.  However, it does not provide pressure or temperature sensing, nor does it have the same sensitivity as mass accelerometers. Our expectation is for the sensors to return useful data for the first ten years of operation; the main problem being sensor calibration and drift.  The telecom system will be unaffected by some or even all of the sensors being out of service.  As a cable system ages, it still functions as a telecom system but returns less sensor data.  

This is a question for the telecom companies – Do the telecom companies have any commercial incentive to do this? Who will be funding the R&D and then subsequent scale-up of these sensor networks attached to repeaters? In one of your papers you cited that 4 W was a maximum of auxiliary power available, which would limit the power available to any connected array of sensors. Would future plans include expanding the dedicated power of repeaters to these attached sensors?
There is no direct commercial incentive to include sensors as part of a cable deployment, but the indirect costs of maintaining and repairing cables broken by external aggression is a large part of the subsequent operational budgets.  As such, it makes sense for cable operators to consider any mechanism which can potentially assist in preventing interruptions to service. The power available for a line pair amplifier is on the order of 4 Watts so our objective is to have the sensors fit within this limit.  The three target sensors draw very little power, most of the power is consumed by whatever optical modules are used to transmit the data.  At present there are no plans to expand beyond the three basic sensor types, although it is recognized as potentially desirable. 

Is electromagnetic isolation another reason to use DAS or optical sensors?
Electromagnetic isolation is certainly a benefit of those sensor types, but not necessarily the main reason to use them.  As noted, other sensors should be complementary.  Ensuring the sensors, particularly those mounted outside the repeater housing, do not cause shunt faults is a design requirement that in turn drives the need for electromagnetic isolation of the SMART sensors.  


Since SMART can only be applied to new cables, what is the perspective for the next decade in terms of km deployed and number of cables deployed?
Our expectation is that the next 5 years will be largely demonstration and confidence building, with about 30 SMART repeaters deployed over that time.  During the following 5 years, SMART deployment would ramp to 150-200 repeaters per year.  Eventually, this stabilizes with about 2,000 active SMART repeaters in service at any time. See the white paper:


A question regarding the stability of the cables due to tectonic changes and plate replacements? Are they risky for cables?
The main risk to cables from tectonic activity is from underwater landslides caused by earthquakes.  Cables are routed to avoid areas where this is known to be a problem, but it can be difficult to find an absolutely safe route. (Note that most cable faults are the result of human activities such as bottom fishing or anchoring.). 


Are the planned accelerometers three-component, and if so how will their orientation be determined?
Yes.  Gravity vector and cable heading.  Further work is planned in this area.  


Question for Philippe and EllaLink – My understanding of current DAS efforts is that the state of the art for cables only permits about 30 km for signal integrity on the backscatter method.  How long would your cable’s segments be between data interrogation points?  Is fibre technology advancing enough to allow for ‘normal’ repeater distances?
Recent improvements to DAS now provide a range of up to 125 km.  DAS interrogators are installed at the shore stations, so visibility is currently limited to the first section of cable.  DAS interrogation of longer fibre spans including repeaters has been demonstrated but not yet commercialized.  


Is still possible to insert some Smart Repeaters in any part of the EllaLink system?
It is probably too late for any already announced systems.  Although some development work is underway, more work is needed to have a practical SMART repeater ready for deployment.  


Another question to Philippe Dumont – Why use DAS only on one cable landing point?  Why not all landing points?
The dedicated fibre for DAS was a late addition to the project.  We hope that future projects can consider DAS at all landing points. 


Smart cables for tsunami and communication purposes. How to do site selection: should a tsunami cable be laid in a hazardous area and communication cable be laid in safer area?
Yes, a telecom cable should always be laid in the safest location whereas tsunami warning systems must sometimes be placed in more hazardous locations.  This does not preclude either type of cable from serving its secondary purpose: a SMART cable can provide some level of tsunami detection or a cable built mainly for tsunami warning might provide some useful telecom capacity.  


There is a clear need for a dedicated system for capacity building among states for cohesive application. Are there any initiatives in place for this?
The JTF is the main forum for such initiatives.  Some of our members are in contact with their national governments.  The JTF works alongside other industry groups such as ICPC and SubOptic.  


What would be the major difficulties for a sustained implementation of SMART Cables? How would it be possible to find a solution?
We believe SMART cables are technologically feasible.  The main limiting factor is cost.  This can be addressed by finding users willing to pay for, or at least place value on the data that can be collected.  Whether driven by science or early warning, governments are likely to be the ultimate source of funding.


What improvements were made in sensors to adhere to submarine qualifications procedures?
The sensors will not necessarily be qualified to the same level as the telecom components; achieving the same level of reliability is probably not feasible because sensors must be in contact with the external environment.  At present, our efforts are focused on ensuring the sensors have no negative impact on the performance or qualification of the telecommunications functions of a cable system.  


Would it be expected to have SMART cables as a standard type of cable offered by submarine cable suppliers?
Yes, that is our long-term vision.  


Which type of incentives could be expected for SMART cables?
Government funding is likely to be needed to support data gathering.  SMART cables can help answer critical questions regarding climate change and sea level rise.  If these issues are made a priority, SMART cables should be part of the solution.  Governments could offer tax credits, long term service commitments, or contribute to construction costs through an arrangement analogous to capacity purchase contracts. Further, governments could provide permitting and licensing benefits to proposed cable systems with smart capability.


Do you envisage any other sensors/capabilities being added to SMART cables?
Perhaps in the future, but our focus now is on the three identified sensor types.  


Given COVID 19 and the even greater need of bandwidth for communications and the launch of the UN Decade of Ocean Science for Sustainable Development in 2021 (which includes an activity for SMART for Tsunami Warning System), have new opportunities for funding been identified for advancing SMART?
We are aware of some general business incentives that might be used for SMART cables, but nothing specifically related to SMART cables.  


Are the sensors and other accessories installed in repeaters during submarine cable manufacturing or placed on the cable during installation on the marine vessels?
They must be assembled during manufacturing.  A fundamental requirement of a SMART cable is that no special procedures or alteration in the cable handling, laying, burial or other installation and maintenance activities be required.  


Are the sensors passive or active devices? Where do they get their power supply from?

The sensors can be considered active devices.  They are powered from the line feed current in the same manner as the optical line amplifiers in the repeater.  


How can DAS be implemented in thousands km long cables? DAS has an intrinsic distance limitation of a few tens of kms.
This is one reason that DAS cannot replace SMART sensors integrated into the repeaters and why SMART is still worth pursuing even with the advent of DAS.  


Seismic data cannot be observed, as far as I know, for more than about 50 km. How can it be used for tsunami warning (if not by perhaps looking at pressure variations)?
While this is true for DAS, this is not the approach taken by SMART cables.  SMART cables will have accelerometers inside each repeater, gathering seismic data at each repeater location.   


Regarding "Help to identify threats to the cable", can you quantify the benefit to the cable operator?
DAS can detect approaching vessels, trawlers, anchor dragging, and on shore construction activities in real time. 
SMART cables will provide additional data regarding the ocean environment that might be useful for planning future cables, but unless the disturbance is close to a repeater, SMART is not as useful for detecting immediate threats.  


Could you elaborate more on the question of non-traditional funding (what might that be?) and CSR expectations from the telecom companies (What will they do that they are not already doing?)
Traditional equity (owners) and debt (banks/lenders) combinations fund most submarine cables, but development organisations or other non-traditional customers could look to provide partial funding, at least sufficient to cover the cost of SMART sensors.  Development banks are already major supporters of telecommunications cables for island nations and other remote locations.  Given that these same locations are most likely to be impacted by climate change, support for SMART cables may also be considered.  


The most sensible form of “non-traditional” innovative funding will work as follows: 

1.  The telco identifies the “additional cost” resulting from smart sensors and translates this cost into a “capacity purchase contract,” i. e., the scientific user will pay the equivalent of the upfront cost in terms of purchasing capacity on the cable over the term, for example 15 years. This way the scientific user receives the data against that payment over the period and the telco is “indifferent” to the extra cost of the smart sensing. The scientific user will then turn to its funder, probably a government, to guarantee the regular payments to the telco (this is in turn attractive to the senior lenders to the telco cable as it adds high-quality credit quality).

2. In addition, there is an opportunity to add “blended finance,” that is philanthropic or foreign government development aid, to the financial package through grants etc. Multilateral Development Banks would be particularly useful to help structure such a combined finance package.


Regarding CSR, cable operators should consider that they are using the oceans and seabed at little or no cost.  Providing some public benefit (beyond the commercial benefit of carrying telecommunications traffic) could help ensure continued support for this low / no cost access.


Finally, regulators and licensors could encourage the deployment of SMART technologies by providing some streamlining of the licensing process for these cables.


What is the state of the project for the Arctic and who are the partners? 
We have followed a number of Arctic projects, but we are not aware of any that are fully funded at this time.  


At this moment there are several cables very close to end of life (EOL). Is it possible to use them in sensor technologies?
Out of service (OOS) cables have been used to create cabled observatories, for example the ALOHA Cabled Observatory  An OOS cable could be used to support a demonstration or prototype SMART cable system and we would be interested in learning more if you can refer us to the cable owners. 


DAS currently has an effective range of about 20 km, with newer systems increasing that to about 50-100 km, how do you propose increasing that range even more? Has the DAS technology been demonstrated yet through multiple repeaters?
We understand that some DAS system providers are studying methods of working through repeaters however we do not have further details.  


What is the typical life expectancy of repeaters? Is there a possibility to use SMART repeaters in future replacements / maintenance?
Repeaters typically have a design life of 25 years.  We expect the sensors to operate for at least ten years. Inserting a SMART repeater into an existing system would provide no benefit because there would be no communications path to shore. A system built for SMART repeaters would include additional fibres or some other method of retrieving data that existing systems do not have. (Note that the supervisory channel available in some systems does not provide sufficient bandwidth.). 


Is there an appetite to accommodate longer range extensions using distributed technology (DAS, DTS etc.), which can be done at incremental costs similar to SMART?
At this time, we do not believe so. SMART is the only technology that can deliver high sensitivity along an entire cable.  


What is the delta impact on power requirements for the sensors?
Our objective is for the sensors to consume no more power than one working fibre pair.  For example, if SMART were added to a 3-fibre pair regional cable system, the power consumption would increase 33% and be equivalent to that of a four-fibre pair system.  


Will the present technology be compatible after 25 years? Maybe some new technology will come.
The sensor technologies we are considering have been in use for over twenty years, so change is slow.  Unless there is some breakthrough, the same sensor technologies are likely to still be applicable.  Nevertheless, we would like to see sensor developments that would improve the long-term stability of sensors, in particular eliminating drift inherent in absolute pressure gauges (without the need for elaborate in situ calibration used in some dedicated scientific systems).  


What’s your view about the vast network of unused and decommissioned fibre-optic cables installed throughout the world? How can this infrastructure could be requalified for science?
As noted above, these cables can be repurposed to support science observatories, however in many cases the shore ends are removed leaving the rest of the cable essentially abandoned.  


Is the DAS fibre a specific type or can any fibre be used?
Any fibre type can be used.  






Thank you to our speakers for joining the session and for their contributions to this article.


Bruce Howe, Chair, SMART Cables JTF
Jose Barros, Director of External Affairs, ANACOM
Jerome Aucan, Researcher, French Institute for Research and Development
Nigel Bayliff, CEO, Aqua Comms
Steve Lentz, Director, Network System Science & Engineering, Ocean Specialists Inc.
Giorgio Mangano, Head of Ocean Bottom Systems, Güralp Systems Ltd.
Sasano Rahardjo, Research Engineer,
Agency for the Assessment and Application of Technology (BPPT)
Frederik Tilmann, Geophysicist, GFZ Research Centre for Geosciences
Philippe Dumont, CEO, EllaLink


If you have any further questions for the Joint Task Force, please submit them to or contact for general enquiries about the webinar.