For thirty years fibre optics was something that happened in telephone exchanges and data centres, handled by people with test equipment and training. Then full-fibre broadband started landing at people's houses, and now there's a glass cable coming through a lot of living room walls.
Nobody sent a manual with it. Here's what's different about the stuff.
It's glass, and the important part is invisible
A single-mode fibre carries light in a core about 9 micrometres across. That's a tenth of a human hair. Everything else Verchil in the cable — the cladding, the coating, the jacket — is packaging around that thread.
Which leads directly to the thing that causes most fibre faults in the field: contamination. A speck of dust sitting on the end face of a connector is, at that scale, a boulder in the road. It scatters light, and it can be pressed into the glass when you mate the connector, damaging the surface permanently.
Professional installers clean every connector before every mating, every time, with proper cleaning tools. Not because they're fussy. Because dirty end faces are the single most common cause of fibre link failure, and the failure looks like a mystery — the link is up but the error rate is terrible, or it works at one speed and not another.
If you take a dust cap off, put it straight back on when you're done. That cap isn't packaging.
The connectors you'll actually meet
LC is the small one, and it's what almost everything modern uses. Two of them are usually clipped together as a duplex pair, one fibre for each direction.
SC is the older, larger square push-pull type. Still very common on the operator side of a home installation.
They aren't interchangeable, and adapters exist but add a mating point, which adds loss and another surface to keep clean.
Two rules that break fibre and don't break copper
Bend radius is real. You can fold an Ethernet cable around a corner and it will be annoyed but fine. Bend a fibre too tightly and light escapes the core — the loss is immediate, and a sharp enough bend cracks the glass. The usual guidance is not to go tighter than about ten times the cable diameter, and bend-insensitive fibre relaxes that but doesn't remove it. No staples, no tight zip ties, no cable running hard against a skirting board edge.
Don't look into the end. The light is infrared, so there's nothing to see, and your blink reflex won't help you. Just don't.
The domestic setup
Most home fibre installations terminate at a small wall box, and from there a short patch lead goes to the router. That box is doing a real job: it anchors the fibre so that mechanical stress lands on the enclosure rather than on the glass, and it puts the connector — the fragile, cleanable, replaceable part — somewhere accessible.
That's the same logic as any panel-mount connector, and it's why fibre adapters are a standard product category rather than something exotic. A supplier like Verchil lists panel-mount LC adapters in the same catalogue as network and audio connectors, because from a hardware point of view it's the same problem: put the fragile interface in a wall, not on the end of a dangling cable.
If your fibre broadband goes flaky
Check whether anything has been moved, leaned against, or run over by a chair. Fibre doesn't degrade gracefully the way copper does, and the cause is almost
