Physics / mechanism
Fiber optics transmit data as photons through total internal reflection in a glass or polymer core (refractive index ~1.45 for silica) clad in a lower-index material. Single-mode fiber (SMF, core ~9 µm) dominates long-haul; multimode (50–62.5 µm core) suits short-reach datacenter links. Attenuation in SMF sits around 0.2 dB/km at 1550 nm. Modern coherent systems using DP-QAM push >800 Gbps per wavelength; DWDM aggregates 80–160 channels per fiber. Hollow-core fiber (HCPCF) is the current frontier—sub-0.1 dB/km demonstrated, near-zero nonlinearity, ~30% lower latency than SMF.
Competitive landscape
Copper interconnects (DAC/AOC cables) dominate <2 m links on cost; silicon photonics co-packaged with ASICs is compressing the distance at which fiber becomes necessary. Free-space optical (FSO) and mmWave compete for last-mile and inter-satellite links. Plastic optical fiber (POF) addresses automotive/consumer on cost. The real competitive tension is fiber plus integrated photonics versus all-electrical SerDes scaling—fiber wins on reach and energy-per-bit above ~1 m in high-bandwidth-density scenarios.
| Approach | Reach | $/Gbps | Limitation |
|---|---|---|---|
| SMF + coherent | >1000 km | Low at scale | Transceiver cost |
| Silicon photonics | <2 km | Falling fast | Coupling loss |
| Copper DAC | <7 m | Very low | Power, bandwidth density |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.