Retrotechtacular: Submarine Cable Splicing Is Serious Business

Really. As this wonderfully narrated talkie picture from 1939 will attest, keeping even one drop of water from penetrating undersea cables is of the utmost importance.

How do they do it? Many, many layers of protection, including several of jute wrapping. The video centers on splicing a new cable to an existing one in the San Francisco Bay to bring the wonder of telephony to a man-made island created for the Golden Gate International Expo.

The narrator makes these men out to be heroes, and when you see how much lead they came into contact with, you’ll understand what he means. Each of the 1,056 individually insulated wires must be spliced by hand. After that comes a boiling out process in which petrolatum is poured over the splice to remove all moisture. Then, a lead sleeve is pulled over the connections. Molten lead is poured over the sleeve and smoothed out by hand.

At this point, the splice is tested. The sleeve is punctured and nitrogen gas is pumped in at 20psi.  Then comes the most important step: the entire sleeve is painted with soap suds.  Any gas that escapes will make telltale bubbles.

Once they are satisfied with the integrity of the sheath, they wrap the whole thing in what appears to be lead cables and pound them into submission. Surely that would be enough, don’t you think?  Nope.  They weld the cables all around and then apply two coats of tar-treated jute wrapping, which retards saltwater corrosion considerably.

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

48 thoughts on “Retrotechtacular: Submarine Cable Splicing Is Serious Business

    1. Why bother to splice the cable and have to deal with getting the data
      off the seabed when you could do in a nice and cozy Room 641A?

      If I were a TLA with huge budget, I would operate/control internet backbone and
      peering companies and collect as much data as I want.

      1. Yep – just intercept at an end node under full color of government permission.

        That being said – watching the evolution of cables is interesting. That stuff on the poles is designed for a 30+ year life span. Which of course is why companies like Verizon are trying to ditch the cabling because it’s coming up on replacement time.

        1. Around here the phone cabling on the poles has passed the half century mark, and Verizon mandated pole workers can only replace them if a tree takes them out, and only that section. Yet they continue to sell us DSL, despite our distance from the DSLAM growing every time a lightning strike takes out a strand, requiring the pole worker to reroute us down another road.

          1. Never thought I’d say this, but you’re luck to still have Verizon. They ditched my state entirely and now we’re stuck with Fairpoint – half the service for twice the price. I’ve since ditched Fairpoint entirely, and my life is better for doing so.

          2. Back in the day I had to get DSL. I contact Verizon and they say I’m too far from the CO. Now granted I live in the city, and the CO is less than a mile from my place.

            So what I had to do was call repair, have them do an MLT and made sure they recorded the distance into my customer record. Then call and order DSL and lo and behold, it worked.

  1. I used to do this in the Air Force back in ’00 to ’06. I worked at a base built in the 1930’s and have ran across quite a few of these lead splices cases. They last quite a while, and are definitely waterproof. The only reason we’ve had to remove them is because of new installations. We still have to hand-splice each individual wire, and wrap them up in different types of rubber tape and seal them up in pre-made stainless steel cases. They can be made totally sealed and waterproof by filling them up with a liquid goo that turns into a solid mass inside the case, or pressurized and tested using the same soapy water method.

    And yes, lead poisoning on the old cases was an issue, we were made to treat them as haz-mat and disposed them the same way after we cut them out of service.

  2. It’s paranoid the amount of wrapping they use, but when the tiniest leak has salty water, at whatever pressure, squirting in, it doesn’t take long for some of the thousand wires there to corrode, and probably the rest soon after. It’s so expensive to lay them in the first place, in such a hostile environment. Paranoia pays!

    Some present-day undersea cables are permanently pressurised with gas, to help keep water out of smaller leaks.

    I wonder how competitive the cost is with satellite? I know the latency is longer, too much for some things. I wonder if it would be competitive to have a series of hydrogen-filled balloons in the sky? Somebody was going to do that in the 90s, for Internet access, using radio links between zeppelins, which would shine radio down over cities and towns. Point-to-point radio bandwidth can be pretty good. And less latency than electricity through copper.

    Another option, maybe, free-space lasers with computerised aiming, perhaps enough that the receiver could be a curved mirror a metre across? It’d be a matter of how stable the combination of a gigantic virtual “sail” with very little mass is. You’d need a layer of still air.

    I was thinking maybe aerial cables, between the zeppelins I mention. A long as you had enough zeppelins that cable lengths would be too short to ever reach the ground. Or you could use a string of smaller balloons, or a combination of both. Perhaps the cables could at least have enough flotation along them that they’d only fall slowly, and so not be so dangerous.

    Or perhaps I’m massively overestimating what you can do with zeppelins. Still, the radio-link idea seemed good to me. A lot cheaper to launch, maintain, and replace than satellites. And even a few networked up would be useful. Wonder what happened to the guy? I think he was a mate of Richard Branson’s, maybe it was Per Lindstrand.

      1. Wrong!

        While it’s fiber optic, there’s also a run of high-voltage cabling to power the erbium-doped fiber amplifiers needed every 100km or so that are on ‘lumps’ in the cable. Fiber optics are also typically slower than copper in terms of latency due to the way the light refracts and centers itself down the fiber, but it also depends on the style of fiber (it is similar to the ‘velocity factor’ of coax).

        1. Aren’t there some laser power amplifiers that are themselves powered with lasers? Not sure exactly how they do it, maybe the “power” wave is a shorter wavelength? They look a lot like a loop of fibre with some doping, as you mentioned. They use those now as line amps.

          For the latency, I was simply thinking the speed of electricity in copper is about a third of light in vacuum, which is about the same as light in anything. Anything normal at least. Never thought about all the bouncing, tho single-mode fibre helps with that.

    1. You should check out Google’s Project Loon. They are using high-altitude balloons to bring internet to remote areas.

      As per the satellite communications, there is a common misconception that people use them for internet. They aren’t used for internet. Nor are they used for international phone calls. Everything is done over fiber optic cables under the seas. The only times you’d use a satellite is if you were in a super remote area.

      1. What are all those communication satellites for then? Seriously, I’m asking!

        I’ve just looked at Project Loon, I’m interested to see how well it does. Maybe the guy who tried it last time (still can’t remember his name!) suffered the problem of being a bit too early, before the technology, and Internet usage, had come far enough. Obviously geographical customer density has grown hugely since the 1990s. I know Loon are investigating Third World places in the middle of nowhere, but maybe it’ll be economical in cities too.

        And that brings to mind two things, firstly that being too early has killed a LOT of modern tech. It’s funny how much of it comes along 5 years later and does so well.

        The other thing is, even though they’re getting Evil in their old age, I’m glad Google are so keen on blue-sky research. Reminds me of General Electric, Bell, and IBM, in the good old, old old, Big Iron days. They all had huge departments of scientists and researchers, inventing the future. Nothing expected of them except “Do some science!”

        The 1980s seemed to kill that off, and ever since, the witless generation who run business these days can only think of short-term profits. Doing proper research pays off later on, but much more, it’s the kind of stuff that changes societies and people’s way of life.

        So, nice to see Google with their 20% time, supporting massive amounts of the stuff that produces heaps of worthless dirt and the occasional gigantic diamond.

        1. In actuality, IBM R&D is still busy working on things that may become products soon. I believe they even have a website up, running on something that IBM builds….. As for GE Research, trust me, they are at work. Google’s problem is being taken seriously.

        2. @Greenaum: “What are all those communication satellites for then? Seriously, I’m asking! ”

          The costs are orders of magnitude above intercontinental fibre bundles, but sometimes $$ are the least of your concerns. There aren’t *that* many (civvie) communications satellites up there, compared to other space users: science, military, spytech are going to be far and away the largest operators up there.

  3. BTW, sorry to go on, but I LOVE these retrotech features, one of the best bits of the site! I think Mike mentioned they’re hard to find stories for, but keep it up! They don’t all have to be Youtube, in fact I’d prefer if they mostly weren’t, I absorb info better through reading and pictures. If not as quickly.

  4. The jute-and-tar wrapping is used on galvanized steel cables for the standing rigging of old sailing ships. Apparently you can get decades of service out of them if it’s maintained properly.

  5. Metallic lead is not the evil substance many people thing it is. It is compounds of lead like in lead paint that are highly bioavailable that are the real issue, just like with mercury.

    1. Yep. I don’t get the lead phobia. It pops into every soldering topic. How much lead do they think the average fisherman is exposed to? Or tire shop mechanic? If it isn’t soluble in water or fats I don’t worry much. My mouth is loaded with mercury/silver amalgum for the last 45 years. Hmmm. That might explain a few things. I’ll get back if I can member where my. What was I looking for?

      1. Mostly it was those millions of tonnes of tetraethyl lead. Or whatever it ended up as when it came out the car exhaust. All sorts of deaths and brain damage has been prevented, and IQs gone up, since they banned it.

        I recall in primary school being forced, along with my whole class, to have my finger pricked and a drop of blood taken by some studenty types who were investigating something to do with lead in petrol. Back when there still was some. I don’t recall my mum being asked for permission, and even if she gave it I bloody didn’t! WTF happened to informed consent!?

        To put it another way, they should at least have tried bribing us with sweets. Wonder what a 30-year-old assault to the finger with a pointy needle will get me in compensation? What’s 30 years interest on a miniature Mars bar?

        1. We used to avoid picking berries along major highways, but that was about all I ever heard about the fuel lead. Plenty of performance enthusiasts still use it as an additive in the US – tetraethyl, people used to say ‘fill er up with ethyl’ when I was a kid. It is an amazingly good additive. Too bad we can’t get a catalytic converter that also removes the lead (instead of ruining the converter), because fuel economy and compression could go up and engine cost go down, not to mention the big improvement in long term fuel storage. You can still get leaded gas for aviation. Nobody wants ruined exhaust valves in traditional engines. Newer engines like Rotax and similar high RPM engines will take 20 or 30 years more to displace Lycoming style. Maybe we will have electric planes by then.

          The mystery that always intrigued me was, where is all the rubber and brake pad material that has worn off the cars? Shouldn’t it be like snow along the roadside?

          1. On busy underpasses, etc. you can see it as a black soot that coats everything, particularly traffic signals. It gets washed away by rain (or blown by wind) often enough to not accumulate.

          2. Worn off tire is consumed by bacteria and fungi and decomposed by oxygen and sunlight. Chrysotile asbestos from older brake pads remains as a carcinogenic pollutant, hence the move towards more biologically inert material such as synthetic aramid.

      2. The main sources of widespread lead poisoning was via paints, and tetraethyl lead in fuel. For someone working directly with lead, one added consumption via erosion onto the hands and clothes, and the inhalation of fumes. We had our Cub and Boy Scouts wash their hands after handling air rifle pellets at the shooting range.

  6. I love to watch the random video links that show up at the end of these things – one just gave a good website for more AT&T videos at ” ” – there are some good hard tech videos there for Retrotechtacular.

  7. BT used to do subsea cables at martlesham labs in the UK, there they had a dedicated building containing a huge hydraulic test tank with a moveable block of concrete as the lid, where massive hyraulics would move the block down to simulate sea bed pressure while testing new cable sections for leakage.
    At the new management direction that came in the 80’s saw most of their engineering expertise depleted and replaced by non technical managers, they sold all the equipment when they became a “service” company, and now have to buy back the subsea cables they require at vastly increased prices from the company they sold them to, one cable & wireless, now one of their biggest compettitors.
    I have seen the subsea cable laying ships in the port at felixstowe docs, great big massive cable reel with a laying derrick hanging off the side. Impressive feat of engineering.

  8. I’m sure there’s a good reason why they didn’t just lay the cable along the bridge. If that were my hand underneath the molten lead, I might have voted for it.

    That was neat to learn about Treasure Island.

  9. The only danger I see is posed by the lead is is green horn being burned in learning the skill or an old hand being burn while having a brain fart doing the job getting burned. I can’t know the makeup of the wire that was used to cover the splice and hammered in place, but it wouldn’t make sense to armor Lead with more Lead. I’d guess is was Monel, hammered to make sure it was tightly seated in place creating as small of lump as possible. In the past I helped spool electrical cable that was used to power large submersible pumps in oil wells. When pulling equipment from the well the manufacturer service man would have us hammer each wrap against the wrap before in, so each layer of wrap would lay smoothly. I thought it odd he did spend more time soapy the ends of the applied hand molded lead after it cooled. In my mind those are those points I would expect leaks. Then they crammed quite a bit of information into >5 minutes, editing had to be tight I guess.

    1. A good many current informational videos could use that sort of tight editing. While the move to digital has removed the physical limitations, I don’t think it’s removed our impatience to get to the point when viewing introductory material.

  10. Oh that takes me back. British telecom were still training engineers in lead jointing in a similar way to this in 1980 when I was an apprentice. It was still used in the major cables running between towns and cities. They were often pressurised too to keep their continuity.

    People forget that cables were finite lengths and joints introduced loss and a point of failure you could do without on the vital comms link between cities. This is before decent radion and GSM gave us other options.

  11. A while back, an American submarine tapped into a Russian cable. We got data from that cable for years, decades I think it was. They didn’t know it for a long time. Then, when they thought we had tapped it, they started feeding us false data.
    But the story of how they found it, is interesting. One of the people involved in the project, noticed in his home area (i forget where it was), he noticed a sign in his harbor that said something like “Caution: Buried Cable”. He figured there is probably the same thing in Russia. And sure enough, after looking, they found a harbor, with a sign that said in Russian “Caution: Buried Telephone Cable”
    So they started snooping around, and that’s how they found the cable. Since it was a land line, that transverse a harbor, they assumed the cable was safe, and couldn’t be tapped. So they never bothered encrypting what was sent over that cable. That’s why it was so valuable to us, it wasn’t even encrypted and because it was trusted, they said and relayed, EVERYthing over it.
    Every couple of years, the navy would send out a submarine and replace the tapping equipment (I don’t know what that part of it was, I think a physical tap, or just electromagnetic radiation monitors).

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