Coax vs Fiber: What Is Actually in Your Wall and Why It Matters
GSC data shows "coax vs fiber" is searched 2,900 times per month and most sites answer it poorly. Here is the hardware reality.
Updated April 2026
The Physical Reality
The plain-language analogy
Coax is like shouting through a metal pipe. The signal travels as radio waves that can be distorted by external noise and attenuate over distance. Fiber is like shining a flashlight down a perfect mirror-lined hallway. The light bounces along the glass strand with almost no loss and zero susceptibility to electromagnetic noise outside the cable.
How Data Actually Travels
Cable (DOCSIS over coax)
Cable internet uses the DOCSIS protocol, which modulates data onto radio-frequency channels across the coax spectrum. Under DOCSIS 3.1, the downstream uses OFDM channels in the 108-1218 MHz range. The upstream (your data going out) uses a much narrower slice: roughly 5-85 MHz under DOCSIS 3.1.
Critically, this spectrum is shared among all subscribers connected to the same neighbourhood node, which typically serves 500-2,000 homes. During peak hours (7-10pm), that shared capacity creates the congestion that causes cable speeds to drop. Each household is competing for the same frequency slice.
Fiber (PON over glass)
Fiber uses Passive Optical Network technology. A single fiber strand from the provider splits passively into multiple strands serving individual homes. Under GPON (most current deployments), wavelengths are: 1490 nm for downstream, 1310 nm for upstream. XGS-PON (newer, 10 Gbps) uses 1577 nm downstream, 1270 nm upstream.
The splitting ratio is typically 1:32 or 1:64, meaning your strand serves far fewer homes than a cable node. And unlike coax RF spectrum, light wavelengths do not degrade meaningfully over typical last-mile distances (under 20 km), so the speed you get in a rural area is the same as in a dense urban block.
Direct Answer: Does Fiber Internet Use Coax?
No. Fiber internet does not use coaxial cable. The fiber optic strand runs from the provider's central office or distribution point to an ONT (Optical Network Terminal) box at your home. The ONT converts the light signal into ethernet, which your router uses.
Your coax wall outlets are not involved in fiber internet delivery. They may remain in use for cable TV, or they can be repurposed for MoCA distribution if you want to extend wired ethernet through existing coax inside your home.
What You Actually Plug In
Cable setup
Fiber setup
Technical Comparison: Key Numbers
| Spec | Coax (DOCSIS 3.1) | Fiber (XGS-PON) |
|---|---|---|
| Signal medium | RF electrical waves | Light pulses (infrared) |
| Frequency / wavelength | 5-1218 MHz spectrum | 1270-1577 nm |
| Max downstream (spec) | 10 Gbps (theoretical) | 10 Gbps |
| Max upstream (spec) | 1-2 Gbps (DOCSIS 3.1) | 10 Gbps |
| Attenuation per 100m | 5-10 dB at 500 MHz | 0.02 dB at 1550 nm |
| Max run without amplifier | 100-200m (node to home) | 20+ km |
| EMI susceptibility | Yes - copper carries EM noise | None - light is unaffected |
| Shared with neighbours | Yes (node, 500-2000 homes) | PON split 1:32 or 1:64 |