العربيةEvery RF and satellite engineer hits this fork eventually: you’re designing a cable run and someone asks, “should we go fiber?” The right answer depends almost entirely on what the cable is carrying. If it’s connecting a modem to a BUC or LNB, the answer is always coaxial — no exceptions. If it’s a data backbone between buildings, fiber is almost certainly the better call.
This guide breaks down the key differences between fiber optic and coaxial cable and gives you a clear framework for choosing the right one every time.
What Is Coaxial Cable?
Coaxial cable carries RF signals as electrical waves along a center copper conductor, insulated from a surrounding braid or foil shield by a dielectric foam core. The shield keeps the signal contained and blocks external interference from entering. An outer PE or PVC jacket provides mechanical and weather protection.
In VSAT and satellite applications the most common types are LMR-400 (standard Ku-band IFL, runs to ~30m), LMR-600 (medium runs to ~60m), LMR-900 (long runs to 80m+), and legacy RG214. For broadcast and CATV distribution, 75Ω RG6 is common.
The capability that makes coaxial indispensable for satellite work: it carries DC power alongside the RF signal. The same cable that carries your IF signal from modem to LNB also delivers the 13V or 18V DC that powers the LNB — plus the 22 kHz polarisation tone — and the 24–48V DC that drives the BUC. No other single cable can do this.
What Is Fiber Optic Cable?
Fiber optic cable carries signals as pulses of light through a glass core, surrounded by cladding (a lower-refractive-index glass layer that traps light inside by total internal reflection), a protective buffer coating, and an outer jacket. There are no copper conductors — signals travel at the speed of light with virtually no attenuation over distance.
Two main types exist: single-mode fiber (SMF, OS1/OS2) for long-distance runs up to 40+ km, and multi-mode fiber (MMF, OM3/OM4) for shorter data links up to ~300m. For telecom and data center backbone, SMF OS2 is the current standard.
The defining advantages: attenuation of just 0.2 dB/km at 1550 nm (vs approximately 30 dB/100m for LMR-400 at Ku-band), complete immunity to electromagnetic interference, and effectively unlimited bandwidth. The defining limitation: fiber cannot carry DC power. Any powered equipment at the far end requires a separate power cable.
Fiber Optic vs Coaxial Cable: Full Comparison
| Feature | Coaxial Cable (LMR-400) | Fiber Optic (SMF OS2) |
|---|---|---|
| Signal medium | Electrical (RF waves) | Light (photons) |
| Attenuation @ 1 GHz | 6.8 dB / 100m | 0.035 dB / 100m |
| Attenuation @ Ku-band (12 GHz) | ~30 dB / 100m | N/A — light, not RF |
| Max practical IFL run (Ku-band) | 30m (LMR-400) · 60m (LMR-600) · 80m (LMR-900) | Not suitable for IFL |
| Max data run | ~50m (10GBaseT, Cat6A) | 40+ km (SMF) |
| EMI immunity | Partial (braid reduces, does not eliminate) | Complete — immune to all EMI |
| DC power over cable | ✓ Yes — LNB 13/18V, BUC 24–48V | ✗ No — separate power cable required |
| RF signal (native) | ✓ Yes | ✗ No — requires RF-to-optical conversion |
| Bandwidth | DC to 40 GHz (LMR-600) | Practically unlimited (>100 THz) |
| Field termination | Easy — crimp tool, N-type / SMA / BNC | Requires fusion splicer + cleaver |
| Cable cost | Lower | Higher |
| Weight | Heavier | Very light |
| Minimum bend radius | 25mm (LMR-400) | 30mm (standard OS2) |
| Security | Can be passively tapped | Tap causes detectable signal loss |
| Ground loop / surge risk | Yes — copper conductor | None — glass is non-conductive |
When to Use Coaxial Cable
✓ Coaxial is the right choice for:
1. VSAT and satellite IFL runs — Mandatory. Your satellite modem must deliver DC power to the LNB (13V/18V + 22 kHz polarisation tone) and BUC (24–48V) through the same cable that carries the IF signal. Use LMR-400 up to 30m, LMR-600 to 60m, LMR-900 to 80m+ at Ku-band.
2. Two-way radio and base station antenna feedlines — VHF/UHF antenna connections are always coaxial. LMR-400 is the standard for fixed base station installations.
3. RF signal distribution — Splitters, combiners, amplifiers, RF patch panels: anywhere you’re routing or processing a live RF signal, coaxial connections are required throughout the chain.
4. Short runs under 40–50 meters — For L-band and below, coax is simpler, cheaper, and easier to terminate. The attenuation penalty is manageable for short runs.
5. Remote RF power delivery — Any equipment at the far end that needs power over the cable (BUC on a tower, LNB on a dish) requires coaxial IFL — there is no alternative.
6. Field installations — Coax connectors (N-type, SMA, TNC, BNC) are field-terminable with a hex crimp tool. Fusion splicing fiber requires capital equipment and a clean environment.
When to Use Fiber Optic Cable
✓ Fiber optic is the right choice for:
1. Long data backbone runs (>100m) — Any Ethernet or network backbone link over 100m should be fiber. SMF supports 10G Ethernet over 10+ km without amplifiers. Coaxial cable would require impractically thick gauge (LMR-900+) and still fall short.
2. EMI-heavy environments — Generator rooms, industrial motor drives, high-voltage transformer enclosures: fiber is completely immune. Coax braid reduces EMI pickup but does not eliminate it — you’ll see interference on the signal.
3. Building-to-building links — Outdoor aerial or buried runs between buildings: fiber provides natural ground-loop isolation and is immune to lightning surges between structures. Copper cable between buildings can conduct a surge that damages equipment at both ends.
4. High-bandwidth data (40G / 100G / 400G) — These speeds are not achievable over coaxial cable at practical distances. Fiber is the only option.
5. Security-critical installations — Fiber signals cannot be intercepted passively. Any physical tap causes a measurable signal loss that optical monitoring equipment can detect and alert on.
6. Harsh or marine environments — Fiber is immune to moisture ingress effects on signal quality, salt air corrosion of conductors, and temperature-driven changes in impedance.
Why VSAT Always Uses Coaxial — Without Exception
In any VSAT installation — from a single maritime terminal to a large teleport earth station — the IFL between the satellite modem and the outdoor unit (BUC and LNB) must be coaxial cable. The reason is simple: the satellite modem or ODU controller delivers DC power to the LNB and BUC through the same coaxial IFL that carries the IF signal. Fiber optic cable cannot carry DC power.
Fiber-based IF extension systems do exist. They use optical modulators and demodulators with separate power injectors to extend IFL runs beyond 100 meters in large earth station facilities. But these are expensive, complex installations reserved for sites where very long cable runs make standard coax impractical. For any typical VSAT site — from a rooftop dish to a teleport hub — coaxial cable (LMR-400 through LMR-900 depending on run length) is the only practical and cost-effective IFL solution.
Frequently Asked Questions
Need coaxial cable for your VSAT or satellite installation?
BravoSatcom stocks LMR-400, LMR-600, RG214 — weatherproof N-type connectors included.
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