Thanks HN folks for all the comments. To clarify a bit, the cables are pulled through PVC conduits under the flooring before being buried in cement. Currently the hypotheses for why the cable disintegrated so quickly is hydrolysis and paint solvents. Singapore is extremely humid but this doesn't explain why the exposed cabling on the other end is still healthy and not crumbly.
The second possibility is that I keep the leftover wall paints (Nippon Paint Vinilex 5000) in the same room and have noticed that much of the solvents have evaporated. It is possible that the solvents in the air might have caused the cable to fail in 3 years. It would explain why the other ends that aren't exposed to the air inside the bomb shelter aren't falling apart.
Some other learnings from this. Buried cabling should always be permanently fixed and attached to a patch panel instead of dangling in the open. That was the original plan but I figured it wouldn’t be an issue. I was wrong. Always measure exact length of buried fibre cabling as they aren’t meant to be stored in loops.
You say that the connection would be permanently severed, but if the fibre is run through PVC can’t you pull a new run? Easiest way is to use the existing fibre to pull the new cables through.
Yeah, leaving hanging loops with a gentle bend radius is very common as long as the loop is secured, and does not cause problems. Maybe something pulled on it though?
next i'd take a look at the network equipment's transceiver signal strengths. ideally over time to see if this has degraded. additionally, take a look at ethernet errors, retransmits, etc.
if you're using 25gbps/sfp28 transceivers, you probably have FEC. if so, you probably have both correctable and uncorrectable error counters to look at.
Thanks, I really appreciate the SMEs commenting here. I'm learning a lot.
Definitely learnt it the hard way this time. You're right that buried cables should be exact in length and fastened to a patch panel. I'll probably look into better conduit design as well for the next time (in 15 years?). Having shared conduits means I would risk damaging other cables if I tried to pull a new cable through.
Good conduit and patch panel design is definitely key for a happy life. Leaving some extra space/capacity initially is also a good idea, especially since (unless you're covering truly great distances) there's not exactly a lot of innovation in the single mode fibre space: strands you put in today (even if it's 'the cheapest stuff your vendor sells most of', which is generally my philosophy for selecting cables) will still be viable a few years down the road.
Sharing/in-place-repurposing conduit is not something I'd recommend, but if you must, leave a few dummy cables (a.k.a. 'pieces of string') on the initial install...
Hey actually I didn't know! It's my very first time dealing with fibre networking so I just maxed out the supposed durability specs. I figured I'd rather go overkill than regret not having done so. Ironic I know.
Unfortunately I can't easily dig the cable out and bury it again in this case. I'll have to figure out how to pull a new cable using the existing cable through the PVC conduits as the cable shares a larger conduit with multiple other fibre and Ethernet cables. The whole project was orchestrated remotely in a different timezone with me giving the electricians instructions over WhatsApp photos and audio recordings, so that limited what I could realistically control onsite back then. Often the contractors would proceed with a do first ask questions later approach while I was still asleep. The networking project was holding up the entire home renovation so everything was learnt and planned in a short amount of time.
AFAIK fibre splicing and terminating tools are very expensive. Do point me in the right direction for the $50 tools and I could go get some and DIY.
> AFAIK fibre splicing and terminating tools are very expensive.
They're more like $600 expensive than $6000 expensive these days. For very low budget, you could go with a mechanical (aerobic) splice; it's more loss, less robust and takes up more space, but doesn't require a fusion splicer.
Back in my day the local telephone company used waxed lacing cable for that sort of thing[1]. These days it seems that polypropylene string is popular (search on "conduit pull string").
You basically want something that is slippery and will tend to not get stuck. I have used Dacron fishing line, but that is mostly because I had a bunch of it laying around.
I wanted to reach you regarding your comment here: https://news.ycombinator.com/item?id=44547866 Would you be willing to maybe elaborate on the problems caused - I've planned to adopt Miro Sameks for an application?
DM me via my about me, if interested. Would be very thankful.
In theory I can pull a new cable through. But practically it might be tough due to the number of bends (shelter -> wall -> vent -> ceiling -> wall -> floor -> room). In the worst case scenario I can give it a try, but it's probably going to destroy the new fibre cable when I pull it through. For now the connection still works, so I am hoping it doesn't get to the point where I have to give that a try.
you can always try the plastic bag + vacuum cleaner trick - take a thin flexible rope, tie it to a small plastic bag, stuff the small plastic bag into the conduit, use a vacuum cleaner at the other end to suck the plastic bag & rope through. You can then use the rope to pull through new cable. If you make the rope twice the length of the conduit, you can keep it in there indefinitely to pull through new cable whenever you want.
I've seen dummy wires being put in when the conduit goes in.
Say initially you need 2 wires from A to B. That probably means there's plenty of room left. So you just put 4 more other wires in there. When the time comes you need to pull a new one, you pull in the new by pulling out the old
To anyone reading this and assuming it applies equally to electrical conduit, it does not, which is why the NEC specs a maximum of four 90 degree bends between pull points. You could probably manage five, as was described, but it is technically disallowed (again, for electrical wiring - the NEC doesn’t care about networking).
Bends ideally need pull boxes, but given the lack of pull boxes, you might be able to use fish tape where where fish rods / glow rods don't work, if you cannot get a pullstring / pull cable going.
It's one of those "just because" moments. The idea was to future proof my home infra for a 25G NAS connection. Most ethernet connections tap out at 10G. While theoretically speaking Cat 8 cables can do 40G, hardware support for full 40G Cat 8 NICs is rare. Fibre is very very flexible with its potential bandwidth and SFP28 transceivers are relatively affordable (if you don't do what I did by using SMF. Home networks should only use MMF if the property isn't a mansion.)
I still prefer SMF over MMF. It also allows me to "move" where the city fiber comes in and patch it to another location without any active hardware. So I can for example move my router into another room.
I'd say the opposite - any fibre in a wall should probably be single-mode fibre (SMF), simply for future proofing. Single mode optics aren't much more expensive and single mode fibre hasn't changed nearly as many times as multi-mode. You can run 25G over the same SMF that once ran 1G - not so with MMF.
The electricians mentioned that in order to curve the cables along underneath the floor tiling they couldn't use metal trunking which would cause sharp angles, so they used PVC pipes to do curvy trunking for the fibre cables. I could theoretically pull a new cable through by ripping out the wall outlet if this cable actually fails. You can see it in my earlier homelab post. But due to the length of the trunking and the number of bends, I'm not too sure if I can safely drag a new fibre cable through.
But yeah, maybe it's not that bad after all. I hope it won't get to that point.
One of my love / hates is Australian parrots and cockatoos - fantastic birds, noisy as hell - and they can rip out and shred unprotected wiring from rural camera and sensor systems like winged can openers.
> due to the length of the trunking and the number of bends, I'm not too sure if I can safely drag a new fibre cable through.
I saw someone commented elsewhere about a plastic bag and a vacuum. Another option to keep in mind is a lubricant intended specifically for the task of pulling cable through a conduit.
I'm not sure either. It's not an air tight bomb shelter and it's used like an average storeroom, storing stuff like winter jackets, suitcases and paint. I do use small amounts of Calcium Chloride based dessicants to keep the room dry.
Radon is a noble gas and chemically inert. It's radioactive, which is why it's a toxicity worry. But there was enough radiation in that basement to mechanically damage plastic in three years, OP would be long since dead.
Radon is a noble gas. It's not going to affect fiber or wiring... but yes, if you're going to spend much time down there, definitely a good idea to check for it.
Interseting - I have high radon (mitigeted in the house via a fan), if I burry fibre what will I need to do to get something that will work? I have an outbuilding that I want to give internet.
As someone who had to learn German, I actually really appreciated the language being formatted quite like closure functions."I have 'noun' upon which 'verb'" with the pronoun and verb being the parentheses where you can then do stuff like f().g().h() where you chain the returned context: "Ich habe etwas getan, was mir schon immer Spaß gemacht hat und mir jedes Mal Freude bereitet, wenn ich daran denke."
Yes I do have a peeve about the numbering system that screws you over at the end, "Ten thousand, three hundred, four and twenty." Yes I know the French numbering is even worse.
German just makes sense to me programmatically. Unfortunately I no longer have much of any opportunity to practise nowadays outside of online language classes.
The second possibility is that I keep the leftover wall paints (Nippon Paint Vinilex 5000) in the same room and have noticed that much of the solvents have evaporated. It is possible that the solvents in the air might have caused the cable to fail in 3 years. It would explain why the other ends that aren't exposed to the air inside the bomb shelter aren't falling apart.
Some other learnings from this. Buried cabling should always be permanently fixed and attached to a patch panel instead of dangling in the open. That was the original plan but I figured it wouldn’t be an issue. I was wrong. Always measure exact length of buried fibre cabling as they aren’t meant to be stored in loops.
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