Comment by alienchow | Hacker News Reader

Comment by alienchow | Hacker News Reader

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.

I see telecoms make loops all the time both indoors and outside. The loops should be strapped together and strapped down though.

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?

>Always measure exact length of buried fibre cabling as they aren’t meant to be stored in loops.

This is awful advice I would discard immediately. It's poor practice and against code.

When pulling cable, especially fiber, the ends of the cable should be able to reach the fathest corner of the room. Excess cable should be in a service loop, properly secured to a wall, and terminated on a patch panel. Both ends of he cable should follow this rule. That means you're typically pulling cable that's 15m longer or more, depending on the room and configuration.

NEVER buy and pull cable that is the exact size. The cable literally comes from the factory looped up, it's designed to be looped (watch bend radius).

Oh, sry! Your comment came after I posted mine. I had similar experience with a bottle of organic thinner for paints.

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.

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