Quick Answer / Summary: Choose pre-terminated single-mode fiber with a 2.0 mm or 3.0 mm indoor drop jacket for the ONT to router path. Single-mode reaches kilometers, so 30 m inside a house is trivial and the optics cost no more than multimode. Keep the installed bend radius at 30 mm or more for a 3.0 mm cable and 20 mm for a 2.0 mm cord. Terminate at a small wall box so the connector stays reachable and the run can be re-made.
The optical network terminal is where the carrier’s responsibility ends, and everything after it is a short, bendy, often hidden run through a house. That makes the job a drop-cable decision rather than a data-center one: jacket type, bend radius and connector access matter more than modal bandwidth. This article covers the ONT to router path, indoor against indoor/outdoor jacket, 2.0 mm and 3.0 mm bend limits, why single-mode wins at 30 m, and the outlet choices that keep the run serviceable.
The Run You Are Actually Building
The terminal is usually mounted where the drop enters, in a garage, a utility cupboard or an outside wall, while the router sits in a living space 10 to 30 m away. That path crosses finished walls and corners, so the cable must survive installation, not a data hall.
Three wavelengths leave the terminal on a typical GPON link: 1490 nm downstream, 1310 nm upstream, and 1550 nm where RF video shares the fiber. All three are single-mode, which settles the glass choice first.
The handoff points that matter
The carrier side is normally an SC/APC connector in a green housing, because angled polish keeps reflections out of the upstream receiver. The router side is an LC/UPC port on an SFP. Most homeowner installs go wrong between those two types.
Why fiber suits this path
Cat6 carries 10GBASE-T to 100 m, so distance is not the argument. Fiber has no ground reference, no lightning path into the router and no susceptibility to dimmer or inverter noise. Power still needs a local outlet at each end.
Jacket, Diameter and Bend Radius
Jacket and diameter set the radius you can bend and the load you can crush.
Where the 7.5 mm figure comes from
Bend-insensitive single-mode glass, G.657.A2, keeps loss negligible at a 7.5 mm radius at 1550 nm. That is an optical limit for the glass, not the cable: a 3.0 mm jacket kinks long before the fiber notices, so work to ten times the outer diameter.
Clips, staples and corners
A staple gun is the fastest way to destroy a drop. Use clips that hold the jacket without crushing it, keep conduit bends above 30 mm, and leave 300 mm of slack at each end so a re-termination needs no new run.
| Cable | Outer diameter | Installed bend radius | Crush resistance | Where it fits |
|---|
| Indoor cord, 2.0 mm | 2.0 mm | 20 mm | Light | ONT to router, visible |
| Indoor drop, 3.0 mm | 3.0 mm | 30 mm | Moderate | Skirting and conduit |
| Indoor/outdoor drop | 5.0 mm | 50 mm | Heavy | Through a wall to a garage |
| Tight-buffered distribution | 2.9 mm | 30 mm | Moderate | Patch panels and trays |
| Armored indoor | 3.0 mm plus armor | 40 mm | Very high | Surface runs in workshops |
Single-Mode or Multimode at House Distances
At house distances both types work, and one is simpler to keep in stock.
Loss budget over 30 m
Single-mode at 0.35 dB/km loses 0.01 dB over 30 m; multimode at 3 dB/km loses 0.09 dB. Two mated pairs at 0.3 dB each dominate the budget either way, so distance decides nothing and connector count decides everything.
Matching the terminal and the router
Order the patch as SC/APC to LC/UPC, or splice an SC/APC pigtail into an LC panel. Never mate APC to UPC: the 8 degree face meets a flat one and leaves an air gap that costs loss and can chip both ferrules.
Keeping the Run Serviceable
A fiber run is only as good as the point where somebody can reach it.
Wall box and service loop
Terminate in a two-port fiber outlet rather than leaving a bare pigtail behind drywall. A 300 mm coil behind the box gives room to re-terminate, and a labeled port tells the next person which fiber feeds the router.
Cleaning before every mate
An LC ferrule measures 1.25 mm across, so dust that would miss an SC core lands directly on it. Inspect and clean both end faces before mating; a contaminated pair adds loss and can damage the end face permanently under spring pressure.
Real Installations
Two houses where the path, not the glass, set the design.
Terminal in the garage, router in the study
A 1980s house had the terminal on the garage wall and the router 24 m away in a study. The installer ran a 3.0 mm indoor drop through 20 mm conduit, ended at a two-port outlet, and used SC/APC to LC/UPC patches. The link held at 2.5 Gbps.
Flat with no cavity to fish
A rental flat had solid masonry walls and no cavity. The run went in 10 mm trunking along the skirting using a 2.0 mm cord with 20 mm radius at each bend. Nothing was buried, so both connectors stayed accessible.
Frequently Asked Questions
Can I run the in-house fiber myself?
The indoor run after the terminal is low risk if it is pre-terminated and clipped with no sharp bends. Do not touch the carrier drop or its splice closure.
Single-mode or multimode for a house?
Single-mode. It matches the terminal output, costs about the same at 30 m and leaves room for long reach optics. Multimode only suits equipment that already uses it.
What bend radius should I keep?
At least 30 mm installed for a 3.0 mm cable and 20 mm for a 2.0 mm cord. The 7.5 mm figure applies to the glass, not the jacket, which kinks first.
Can two fiber patches be joined with a coupler?
Yes, with a mating sleeve, but each joint adds about 0.3 dB and a reflection. One joint in a 30 m run is acceptable; at three, pull a single length.
Does fiber need grounding or surge protection?
It has no ground reference and no surge path, which is one reason it suits a utility cupboard. The equipment at each end still needs a grounded outlet.
Related resources: fiber network cabling; fiber optic network cable forms; fiber versus copper
