Most of the time when we talk about engineering on the podcast, we talk about the kind of engineering that maybe involves writing a unit tests, perhaps an end-to-end test, and if you're feeling extra special that day, a property test before shipping it into production. In case something breaks, there's usually a gradual roll out you can stop or a feature switch you can close to give yourself some time to work on a fix.

This is not the kind of engineering we're talking about today. This episode's guests, Andy and Pascal – and I haven't reached the point of self-delusion where I start to talk about myself in the third person. That's a different Pascal who's very much not me. Anyway, Andy and Pascal work on our subsea cable infrastructure that carefully places high-tech fiber cables along the bottom of the ocean to allow us all to communicate quickly in high fidelity and with redundancies in case something goes wrong.

And I'm sure after you have listened to the conversation, you will like me have gained a new appreciation for the various ways in which submarine cables are subject to disruptions that are outside of the control of the engineers working on them. Andy and Pascal recently started working on Project Waterworth, which once completed will reach five major continents and span over 50,000 km, making it the world's largest subsea cable project. This is the kind of project where long deprecated approaches like move fast and break things won't cut it.

Completely unrelated to crosscontinental communication links. We've had a few hiccups during the recording. I've done my very best to clean up the audio and shorten the awkward gaps where I had to reconnect. If anything sounds a little corrupt. Please blame this one on me and not the other Pascal or Andy. And now without further ado, here are Andy and Pascal to talk about the challenges and opportunities of working on the world's largest subsea cable project.

Pascal H. (Host): 95% of all internet traffic goes through them. And this particular conversation, given that it crosses the Atlantic, has a nearly a 100% chance of flowing through one of them, and yet most of us rarely consider their existence. Subsea cables. This is, however, certainly not the case of my two guests whose whole job is to think about them.

Andy and Pascal, welcome to the Meta Tech podcast. I'm honestly thrilled to have you on because I may have a bit of a strange tick where I do spend quite a bit of time thinking about the mostly invisible infrastructure that powers our digital lives, whether it's the electrical grid or intercontinental fiber lines.

But before we dive in. Sorry this probably won't be the last accidental pun here. Let's quickly talk a bit about you both. Andy, can we start with you? So how long have you been at Meta and have you always worked on subsea cables infrastructure?

Andy: I've been at Meta now for just over 8 years. And you're right, I've always worked on submarine cables. My first job in the industry was back in August, 2000. So coming up on 25 years of designing, planning and engineering these subsea telecommunication systems.

Pascal H. (Host): I also feel like this is probably not quite as flexible a space where you can just jump between, like we often do as engineers. Like, oh, I'm gonna work on an Android app now, even though I'm an iOS engineer or something. So I'm, I'm glad you are bringing long expertise with you. So how about you Pascal?

How long have you been at Meta and did you do something else before you worked on submarine cables?

Pascal P.: Ah, yes. I joined Meta to a little bit more than two years ago. So in January, 2023. And before I worked for a wet supplier that we are using right now for our cable for 10 years in, in subsea. And before subsea, I started with terrestrial. So always optical transmission, but first in terrestrial during 15 years, 10 years of subsea and now two years within Meta.

And happy to, to keep on working on subsea.

Pascal H. (Host): Fantastic. Okay. Let's address the elephant in the room. Most people when they think of Meta, don't necessarily think of fiber lines thrown on the bottom of the ocean. So tell us a bit about this entire engineering team that is dedicated to building subsea cables.

Pascal P.: Yes, we, we have a great team with within Meta and, Meta develops infrastructure all across the globe to transport information and content for billion of people using Meta services, all around the world. At the core of this infrastructure, aggregation point, and the digital cable that connect them, Meta uses aggregation point, like data center, for example, to us, the technology that supports our apps and services.

And to connect the aggregation point, Meta invests in digital cables over land, but also sea, so subsea cable are critical for Meta to serve people wherever they are in the world from our data center. And 95%, as you underline, at the beginning Pascal, 95% of the traffic is going through this subsea cable.

Without this robust connection and a strong edge ecosystem anchoring this network, people would receive subpar performance when accessing content. So we are involved in every step of this project. Understanding how much capacity is needed, how to resource it, where the cables touch land, where on the ocean floor we put them, how much protection the cable needs, what kind of ships are used to lay. We’re overseeing the manufacturing and more. So our engineering team, so Andy, myself and other people, prioritize both innovation and quality. These cables are the unseen digital highway of the internet, which is why we are one of the biggest invest, investor in subsea cable.

Pascal H. (Host): There are so many areas and then so many challenges. I want to address as many of them as possible, but maybe we could first talk a bit about the scale. So people actually understand our contribution to this worldwide ecosystem.

So how many subsea cable projects has Meta done, and what role do our engines actually play in them?

Andy: So we've been investing in directly owned submarine cables since about 2016. When we started building the Marea cable that goes between Spain and the U.S. Since then, we've invested in nearly 30 submarine cables around the world. So they are in a Pacific, Indian Ocean, and we've even built a cable that goes all the way around Africa.

The project's a huge undertakings that typically take three to five years to complete and are designed to operate for 25 years. As Pascal mentioned, we're involved in every step of the way.

The submarine cable engineering team specializes in optical physics, manufacturing, and quality control, ocean floor geology, specialized vessels and more.

And we don't do this alone. We, we're partnered with our strategy, legal policy, environmental teams to support various aspects of these projects. We also collaborate with telecoms operators, and governments to help us build at the scale.

Pascal H. (Host): So recently Meta announced Project Waterworth. This is how I found out about the scale of our Subsea cable infrastructure and frankly, I think a lot of other Metamates based on the comments that we saw internally. So what I read is that this is the longest subsea cable project ever longer than the earth’s circumference.

So can you tell me a bit about, more about the project? Where is it going and why are we building it?

Andy: Yeah, certainly. So Project Waterworth, as you say, is a huge undertaking. It goes between five continents. It connects to US India, Brazil, and South Africa. And it's unique because it goes from the US East coast to the US West coast, the long way round. So it's the first cable ever to go all the way around the world.

Um, it's three new ocean corridors being opened up. So one in the Atlantic from the US down to South Africa, then from South Africa up to India, and then we connect from India via the Indian Ocean and the Pacific back to California. So it provides a huge amount of diversity from other existing routes, and should also provide a lot more resilience to the global backbone.

Pascal H. (Host): What's the primary reason for investing in additional infrastructure? Is it the resilience that you just mentioned, or are we also stretching the capacity of existing cables?

Andy: A bit of both, but I think that the resilience aspect is huge with, with Project Waterworth. So if you look at existing cables that go between the US East Coast, Europe, and. India, they all pass through the Mediterranean, then they cross Egypt terrestrially, and then they go down the Red Sea and out through the Gulf of Aiden into the Indian Ocean.

That area's become problematic due to both the Middle East tensions and the situation with the Houthis. We saw only a year or so ago that a ship in the Red Sea damaged multiple cables and caused a significant outage. So we, we try and look for resilience, and when you've got very narrow seaways, such as the Red Sea with a lot of cable forced into very close separation that that represents, um, a single point of failure for us. So one way to mitigate that is to explore new routes that may be longer, but they'll be far more reliable. So that's why we're going the long way around Africa to get to India. And similarly in the Asia Pacific region, there are also other tensions and other geographies where it's getting more difficult to obtain permits and more time consuming to obtain the permissions needed to lay the cable.

So by routing the cable in deeper ocean, further away from problematic jurisdictions, we, we can move faster and deliver with greater predictability and resilience.

Pascal H. (Host): That is absolutely fascinating. I think most of us will be fair to say, don't really need to consider the geopolitical risks as part of their engineering day-to-day job. But what you, you are doing is clearly motivated by very current events and still needs to happen on these really long time scales because as you have described, you don't just go into a hardware store buy a 10,000 kilometer cable and throw it off the back of a ship at your rent where there are long timescales involved. But maybe we focus on one of these pieces first. So Pascal, maybe I can ask you about this.

So what does a cable actually look like? So what, what do I need to picture when I think about a submarine cable?

Pascal P.: Ah, excellent question. Usually people think of, of subsea cable that will be big like a power cable that will add the size of a, of a leg. But in fact, I have one here.

Pascal H. (Host): And I should just mention, I'll put this into the cover photo for the podcast, so people who might want to pause for a second or grab the phone, they can check it out. Now, it is really small. It looks probably about the same, at least on the inside. Then your average Cat6 cable that people might be familiar with, and then having some sort of outer layer.

So what are these outer layers around the actual fiber line there?

Pascal P.: Yeah, so we start with the first part, which is here. The first part is optical fiber. So the optical fiber are really small. There are 250 micron for the outer diameter, so equivalent to, to your hair. Then to protect this fiber, we have a tube. The tube is two three millimeters of outer diameter. And to really protect this tube from the water pressure, we added wires, stainless wire that will create a vault around the tube and that will allow to protect it from the water pressure. And then we have copper. You can see the copper because in fact, an optical cable, subsea cable is also a high voltage line where we'll have current on it.

So the copper will have two functions. The first one will be to protect mechanically, the vault to be sure that the wire will not explode. And the second function will be to carry the current.

And finally, we have what we can see in white here, the insulation layer, which is a polyethylene layer. And the subsea cable is usually composed of this type of cable. But in some regions, some areas, we can have another one, a bigger one. So this one was 17 millimeter, and this one would be a little bit bigger, but you can see the first, the basis, which is here, the lightweight cable on top of which we have added one, two, so two additional layers that will allow to protect the, the cable, and this is what we call the armoring, the armor of the lightweight cable. And when we add the, the armoring, we will switch from roughly half kilogram per meter to four kilogram per meter. So we'll multiply by eight the weight of the cable,

Pascal H. (Host): So the optical layer is obviously for transmitting the data that we have, so why do we need the high voltage line in there as well?

Pascal P.: The line voltage line is key because the line voltage will allow to power what we call the repeater. Indeed, every 80 kilometers, 70 - 80 kilometers, we will need amplifier inside the repeater, and this amplifier will allow to amplify the light, the optical parts of the cable. This optical amplifier has been invented in, in the eighties. We will have more explanation, later, and thanks to this regular amplification, we will be able to transmit the signal above 10,000 kilometers. For Waterworth, for example, project we can go up to 14,000 kilometers. Which is incredible. And the weight, if we compare with respect to the weight of the cable, half a kilo per meter, the weight of a repeater will be around half a ton. So 500 kilogram, 1000 pounds.

So in addition to the repeater on the cable that we just explained, we have also on the path of the cable branching unit. And this branching unit will allow us to drop some fiber pairs in a country or in a island to add and drop cri uh, traffic regularly because subsea cable is not only end-to-end, but it can go to intermediate landing. And the weight of this branching unit is really high. It's equivalent to a medium sized car, so 1.5 tons, 3000 pounds.

And what is also important for all this element, the cable, the repeater and the branching unit, we need to underline that they will be under the water for 25 years.

Pascal H. (Host): What?

Pascal P.: It's really crazy. We can't imagine having something at home with electronic inside because in the repeater we have component, electronic component. And we can't imagine at home to have something that would be guaranteed for 25 years with a high pressure. Because when we speak of the pressure at 8,000 meter, it's equivalent to have one car on your tummy. The pressure is as high as this.

Pascal H. (Host): That definitely requires some real engineering, not just what we call engineering and software, but I, I'm glad I don't have to create software or anything that needs to withstand these scenarios over the course of a quarter of a century.

So can we talk a bit more about the actual process behind it? Because as I've mentioned before, this is not the kind of thing where you just go out one day and you decide, Hey, I want to throw a bit of subsea cable into the ocean.

So how do you actually start when you want to plop down tens of thousands of kilometers of subsea cable?

Andy: So the first thing we have to do is a, what's known as a desktop study where we'll look at the available information about the ocean to plot out what looks like a good route. So we'll take into account other cable routes, areas that we know, know to be shallow or deep, any areas that are protected or off limits for other reasons.

And then we have to go out and do a survey because the maps that we have at present of the ocean floor, they're, they're really not very good. We know far more about the surface of Mars and the moon than we do about the deep ocean.

Pascal H. (Host): That is kind of sad actually.

Andy: Just a bit. Because of that, we've gotta go out and do our own mapping exercise.

And the only way we can see underwater is we've using sonar. So sonar is the transmission of sound waves. Um, those sound waves will bounce off the ocean bed and we measured the time that they arrived back at the ship, to create a 3D digital map of the ocean floor.

And what that allows us to do is see any features of interest such as submerged volcanoes, canyons, drowned valleys, all sorts of interesting things on the ocean bottom, where it probably would not be a good place to put a cable. We're looking for the most flat, boring place on the floor where we can safely lay the cable and where it's going to not experience any difficult conditions, any abrasion, any strong current. So we're mapping all these things out, and then the next step is to get on and, and lay the cable. And that's done from a cable ship. Everything's done from the surface.

People often ask me, what's it like to go down to the bottom of the sea? And I've never done that. No intention of ever doing that. Um, it is something we can do from the surface by carefully laying the ship with the correct tension and the correct layback from the back of a ship. In deep ocean, we lay the cable very carefully on the planned route, and it just sits on the, on the bottom.

In shallower water, it may need some more protection. So in addition to the armoring that Pascal mentioned, we also want to trench the cable into the sea floor sediments, and that's done using a plow or remotely operated vehicle, and it can keep the cable safe from ship's, anchors, fishing gear, or other hazards.

Pascal H. (Host): That is definitely a lot to consider. When you map out the ocean floor, I guess a lot of this has to do with ensuring that you're not disturbing any protected ecosystems or other things. What, what are some examples of things that you found without knowing about them before and you decided, okay, we definitely need to route around them and not right through.

Andy: All sorts of interesting things. So we, we come across shipwrecks, on occasion, that have never been chartered. We come across submerged valleys in the deep ocean floor, which have been eroded, you know, either many thousands of years ago, or some of them are still being eroded by processes today that happen on the continental shelf and send sediment down into the deep sea.

In fact, it was only with the laying of submarine cables, telegraph cables in the early 1900s, that some of these deep ocean oceanographic processes were actually discovered because they were causing cables to break. So, there's all sorts of interesting things down there that we are looking at and, we've got lots of experience in the industry that tells us what is a suitable environment in which to lay the cable.

When it comes to the marine floor and fauna, we’re looking generally at those places that are far less interesting in terms of habitats. You know, we're trying to avoid anywhere which is gonna be environmentally sensitive. And, you know, we work closely with regulators and the environmental agencies within government who often, you know, declare certain areas as off limits for submarine cables.

But generally speaking, the cable itself is very benign. It doesn't leak any chemicals. It doesn't create any electromagnetic field. So once the cable's down there, it's, we describe it as being sort of having a benign to neutral impact on the marine environment once it's laid.

Pascal H. (Host): Yeah, we've seen it or have had it described to us. For those who don't want to look at the cover. Definitely doesn't seem like a huge disruptor, but it is, it definitely makes sense to at least look at what you are potentially disturbing there.

And I would like to focus a bit more on the differences between the deep ocean and the more shallow sections that were just described. So how, how did the two differ? We've heard already that in the shallow areas you might need to add some additional protection.

Andy: Yeah, so the shallow areas are really the, generally speaking, the problem areas. Far more faults on submarine cables occur close to land. Once you get out beyond 200 miles from shore before, you know, you only see three or 4% of all faults happen out in the, what's known as the high seas and the deep ocean.

So it's, um, it's very important to try and get the cable out into the deep water as soon as possible. We're always looking to minimize the distance on the continental shelf because that's where the dredging, the fishing, the anchoring is all happening, which can be extremely harmful to the cables.

It's also far more expensive. So what, once you're in a deep ocean, it's very quick to run the survey. It's very quick to install a surface laid cable. In the shallow water, everything takes far more time, costs more money, and it's generally far more complex all around. So being in the deep ocean, over a thousand meters water depth is advantageous.

Most deep ocean seabeds are somewhere in the range of 3 to 5,000 meters water depth. There are occasions where it gets deeper, so there's some trenches. There's a famous, um, Mariana's Trench. There's also a trench that the waterworth cable crosses called South Solomon Trench, which goes down to 7,000 meters.

And in those environments, we just have to lay the cable quite slowly and carefully to account for the gradients. We actually use the lightweight cable down there because it has the highest strength to weight ratio. If we were using an armored cable, it would be so heavy that if we ever needed to recover it to repair it, it would, break under its own weight and water. And lastly, you know, with the amplifiers, the repeaters that Pascal mentioned, we try and plan so they, they're not located in the very deepest parts because they all add weight which makes it complicated to recover the system for repairs.

Pascal H. (Host): There are so many considerations there. How does it actually work when you have like two completely separately or differently armored cables? Do you need to have a splitter in between them or do you just, I don't even know the words for it. Transform them from one cable into the other in some continuous flow.

Andy: Yeah, there, there's transition. So the transition between one cable type and another is basically just, you know, the armor stops and then the core of the cable continues, which is the lightweight Pascal mentioned. The tricky bit to manage there is the torque because, all cable likes to twist, you know, it's got a memory, it wants to twist. And the cable with the armor wires on wants to twist more than the other cable. So, you generally have to sort of manage these transitions. So you go from a heavy armor to a medium armor and then to the core cable in sequence. And that is a way of avoiding this twist effect propagating down the cable as it's being installed.

Pascal H. (Host): So we talk now about the difficulties of keeping the cables alive, so to say, especially in these shallow regions where a lot of traffic can happen. But things will inevitably go wrong if you have fisher boats and other entities floating around there.

So what happens if something breaks? Who's on call for this?

Andy: So when a cable breaks, um, the industry is set up with a standby fleet of repair vessels, all around the world that is sort of jointly funded by, by every system.

Every system enters into an agreement, which is designed to sort of jointly fund a cable ship or several cable ships in a given region. So they're on standby, ready to go out, a bit like fire trucks. They're all, they're manned, ready to go. So when there's a fault, the cable ship will load the spare cable. It will plan the repairs. Sometimes we'll have to get some permits, if it's within an area of jurisdiction, and then the vessel will head out.

The fault location will normally be identified from the cable station. They'll be able to use methods such as optical time domain, reflectometry to locate that cable fault location. So they know, they know where they're going. And when they get to site, the first thing they will do, typically, is to cut the cable deliberately. So they will use a hook with a blade in the hook and hooks on a line, and they'll drag it across the cable line to create a cut. And, then they've got two separate ends and they can then use hooks that don't have blades on to hook those two respective ends and bring them up to the surface. Once the two ends are on the surface, it's possible to then splice in an extra section of cable, we call spare cable, to join, the thing back up again.

And because you're bringing everything up to the surface, that's why you need the extra distance to be inserted to connect the two pieces. It's jointed and it's tested. They make sure everything's working from the cable stations at each end, and then the careful the cable is carefully lowered back down to the seabed to create a sort of, what we call a bite, which is a loop of cable, which will be offset to one side or other of the original route. And, and then, you know, it can be put back into service.

Pascal H. (Host): I am very glad there are international collaborations going on for this, and not one of you gets a call in the middle of the night. It's like, okay, I'm going to Vietnam to fix a cable or wherever that fault may occur.

Andy: Well, we often have to coordinate and we have to liaise and, arrange for the ship to be called out. But no, we don't actually have to get on a plane and on a boat and go and do it.

Pascal H. (Host): That definitely feels like enough work already. Yeah. So we've talked about plenty of challenges here. It feels like pretty much all of it is just so much more complex than anybody would think who's not emerged in this space like you clearly are.

But if you could pick just one engineering challenge or maybe two that you found particularly revealing about the complexity of this entire space, what would you go with?

Pascal P.: The, the first challenge, I can see is space. Space because when you look at the cable, at this cable, you start with that 2 millimeters for the optical fiber, and you end up with 40 millimeters. You multiply by 200 the size of the outer diameter. It's crazy just to protect this small fiber from fishing activity as explained by Andy.

So space also for lightweight, even if this is a smaller one, we have to carry, the ship will have to carry and to lay 10,000 of kilometers. And there is also the fact that the ship have only so much space for longer and longer cables. So, I remind that Waterworth is 50,000 kilometers of cable.

So space is key, but also when we increase the volume to be produced, we need to focus also on quantity and quality. And when we consider the length of cable to be produced, we need to be sure that the wet supplier will be able to manufacture it with very high quality. Because usually when you increase the volume to be produced, the quality can go down and this is absolutely not possible when you guarantee the cable for 25 years.

So I will compare subsea cable with haute couture and at the same time high technology. Haute couture because we can really customize everything but we need to have mass production. Also when we speak of 50,000 kilometers, that should last for 25 years.

So this is, this is really incredible.

Pascal H. (Host): It really is, and I think now we need to just kind of speed run through some of the questions that we have left, but one we definitely need to address is how much capacity does one of those cables actually have?

I guess like everybody looks at it, it's so small, it can't be. That much, but we know it's actually light that is going through it, but how, how much does it have and how does it work?

Pascal P.: So how does it work? Optical light that will go through optical fiber. Now, with respect to the quantity and capacity that we can reach roughly, it's half petabit for 7,000 kilometers.

And for Waterworth, when we will double the distance, 14,500 kilometers. Thanks to midpoint, we will do a stop in Hawaii or in Brazil in Fortaleza. We will, it'll allow us to power the cable and to stay with a reasonable capacity that will be 0.4 petabit.

And capacity is automatically linked to the number of fiber pairs that we'll be able to put in the cable. And currently what we are using is maximum 24 fiber pairs. The more fiber pairs we have, the more capacity we have. And it'll be linked also to the number of repeater we talk about that we can put on the cable. The more we add also, the more capacity we can, we can reach.

Pascal H. (Host): Can you give us a brief idea of how much 0.5 petabits is in something that people can have, have an easier kind of grasp on?

Pascal P.: 0.5 petabits. So if you need to remind only one figure. So three years of 4K video. Three years, you imagine in just, one second. So we have transmitted three years of 4K video between these two words. It's really amazing. And, we currently have very few cable in the world that are able to transmit 0.5 petabits. Meta will have one that will be completed soon, in the coming months, between U.S. and Spain. So I would say less than 5 alpha bit cable.

Pascal H. (Host): So it definitely gives us a lot of room for growth if we want to all move up to 8K, for instance.

So how many fiber pairs do you, most of the cables currently have? If you say this is not really all that common.

Pascal P.: In average, I think that right now the average value is 16 fiber pairs for, for the number of fiber pairs. But with Meta we are pushing always the cable to the limit. So we are mainly using now only 24 fiber pairs.

It can be a low value if we compare with terrestrial, because with terrestrial we are at 1000, 2000, 5,000, fibers in the cable, but the constraints are not the same. Because, as I explained, a subsea cable is not only an optical fiber, an optical cable. This is also an electrical high voltage line because we need to carry the electricity, the power that will power the repeater. While on terrestrial, we have huts space regularly that will bring the power to the optical amplifier.

Pascal H. (Host): Yeah.

Pascal P.: This is, this is a big difference.

Pascal H. (Host): So obviously the number of fiber pairs has dramatically changed over the years, so what else has actually changed in the kind of long history of these cables?

Andy: Well, in many ways, not very much. The first cable that was laid across the English channel only lasted a day before it was hit by a fishing boat and damaged. And yeah, these are the same similar threats that we, we're facing today when it comes to cable protection. But, yeah, other things have developed, you know, we've got far, far more sophisticated ways now of laying the cable compared back in the Victorian days.

But one, one fun fact is that, back then global time zones only became necessary when submarine cables became installed. It was the advent of the telegraph cables. And that conversation between Queen Victoria and President James Buchanan that made people realize that he didn't actually know what time it was.

They knew what time it was, but they didn't know what the respective time difference was between the two countries. So they had to then develop the global time zone system when telegraph cables arrived. Um, you know, prior to that, when it took several weeks to be able to send a letter by a ship, it didn't really make much difference.

Pascal H. (Host): That is fascinating. And now at least we have an overlap to the software engineering world that suffers greatly due to the introduction of time zones, which is one of the hardest things to wrap your head around. Pas, Pascal, do you have a different perspective on things that have changed over the years?

Pascal P.: I, um, yes. Since, since the eighties, things has, have changed a lot because we were in the past with electrical amplification. And in the eighties, we have the introduction of optical amplification and, the first subsea cable using optical amplification were at the end of the eighties, beginning of the nineties. So it was not, if we compare with the 25 years this cable, the guarantee, ended in 2015. Finally, so only 10 years ago.

Then in the early 2000s, we had an increase of the number of fiber pairs. So, but a small increase to 4-6 fiber pairs only in the cable with only 10 gigabit per fiber pairs. So each second, only one hour instead of three years. Only one hour of 4K video.

And then in the, in the, we add also what we call the coherent era. So you have an internet box at home, here at the end of the subsea cable, we have what we call transponder. And with the coherent era and the revolution on this transponder, we can multiply by 10, the capacity. Which is, which is really crazy.

We can't add this anymore right now. So we need to use another technique, which is to increase the number of fiber pairs 8, 12 to and now 24. This is a maximum that we can reach. And for this, we use what we call SDM technology. So SDM technology is based on parallelism.

We are using multiple fiber pairs to transmit the capacity that we want to, to reach in the subsea cable. So it was the main key changes during the last year, since the late eighties.

Pascal H. (Host): Amazing stuff.

So unfortunately we're running out of time, but I definitely don't wanna let you go before you can tell me a bit about your upcoming plans.

What is next for you? And. for your team.

Pascal P.: Next subsea cable. So let's speak about it. The next subsea cable, we, we target to double the capacity. We spoke about half petabit for the transatlantic, so the idea will be to go to 1 petabit. And Meta is really a leader in the industry for the 1 petabit cable because the Metaverse, Llama 4, with multimodal AI innovation announced recently. They are pushing for more capacity. So, 1 petabit is the right number for the coming years. It's equivalent to 48 fiber pairs. So we will use the same technology. We will double, we'll ask the wet supplier to double the number of fiber pairs, or we have another technique if we want to change a bit.

In the rainbow we have multiple colors. Currently we are using only half of the color of the rainbow, so the idea is to double the bandwidth. So to use all the color of the rainbow and to use what we call C+L bandwidth.

And finally, another solution. When we look, when we come back to this fiber, the idea is to use two fibers and to concentrate these two fiber into one single fiber. And this is what we call, two core fiber. And one single fiber will be equivalent to two current fiber. Each time, will it be the color, the number of color or bandwidth that we'll use? The number of fiber pairs or the type of fiber that we will change each time, we will multiply by two, the capacity, and we will go to, 1 petabit.

Pascal H. (Host): That is really incredible. As Andy just said, this is effectively still in it at its core, the same technology that was used in the 1850s, and still there's so much more you can do in terms of little optimizations that in the end, double the capacity that you have. That is still no mean feat.

But okay, unfortunately we're running out of time, although I'm sure I could spend another hour talking with you. So Andy and Pascal, thank you so much for ensuring that we can have these discussions across the ocean and share so much information and build community with people. Definitely in a much more reliable fashion than many of the other technological pieces that contributed to this discussion.

But thank you so much for building all of this and joining me here on the Meta Tech Podcast.

Andy: Thanks for having us.

Pascal P.: Thank you very much, Pascal. Bye-bye. Bye everybody.

Pascal H. (Host): And that was my interview with Andy and Pascal. Did the rigor that goes into planning for a project that needs to work and continue to work for decades in one of the most inhospitable places on Earth also break your brain a little? Let us know on Threads and on Instagram where we are at @MetaTechPod and I'm @passy_.

If you want to show us in other ways that you've enjoyed the episode, then why not leave us a five petabit rating in your podcast player of choice. But that's it for another episode of the Metate Tech Podcast. Until next time, toodle-loo.