A communications network that transmits data as pulses of light through strands of ultra-pure glass or plastic fibre, achieving terabit-class bandwidth, low attenuation over tens of kilometres, and immunity to electromagnetic interference. Fibre optic networks form the backbone of global telecommunications — submarine cables, metro rings, data-centre interconnects, and fibre-to-the-premises access — and set the bandwidth and latency envelope within which cloud, streaming, and real-time immersive applications operate.
Semantic Classification
Content
Definition
A fibre optic network carries information as modulated light guided by total internal reflection along hair-thin strands of glass. Because optical carriers oscillate at hundreds of terahertz, a single fibre pair can carry tens of terabits per second when dense wavelength-division multiplexing (DWDM) stacks scores of independent wavelengths onto it; because silica attenuates light by only ~0.2 dB/km at 1550 nm, spans of 80-100 km need no amplification, and erbium-doped fibre amplifiers (EDFAs) extend reach across oceans. These physics give fibre its decisive advantages over copper and radio: vastly higher Bandwidth, lower loss, and complete immunity to electromagnetic interference.
Structurally, fibre networks form the layered core of Telecommunications Infrastructure. Roughly 500 submarine cable systems carry the overwhelming majority of intercontinental traffic; terrestrial long-haul and metro rings connect cities; dedicated dark-fibre routes interconnect Data Centre campuses, where hyperscalers run their own optical backbones; and access networks bring fibre to the premises (FTTP) through passive optical network (PON) architectures that split one feeder fibre among dozens of homes. Inside facilities, the same technology scales down to metre-length transceiver links at 400 and 800 Gb/s between switches and GPU clusters.
The contrast with Satellite Communication is complementary rather than adversarial: fibre wins overwhelmingly on capacity, cost per bit, and Latency where it can be laid (light in fibre travels at about two-thirds of c, giving London-New York round trips near 60 ms), while satellites cover the maritime, rural, and disaster-recovery cases where trenching is impossible or uneconomic. For the real-time immersive workloads in this graph — cloud rendering, volumetric video, telepresence — fibre’s combination of throughput and stable low latency is what makes the application classes feasible at all.
Technical Details
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Fibre types: single-mode (ITU-T G.652/G.654, 9 µm core) for long haul and access; multimode (OM3-OM5, 50 µm core) for short intra-facility links.
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Multiplexing: DWDM with up to ~96 channels at 50 GHz spacing in the C-band; coherent transceivers (QPSK to 64-QAM with DSP) deliver 400 Gb/s-1.2 Tb/s per wavelength.
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Amplification and reach: EDFA and Raman amplification; submarine repeaters every ~60-80 km; record hollow-core fibres cut both loss and propagation delay.
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Access architectures: GPON (2.5G/1.25G), XGS-PON (10G symmetric), and emerging 25G/50G-PON; point-to-point Ethernet for business services.
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UK context: Openreach’s FTTP build passed 20 million premises in September 2025 and roughly 22 million by early 2026, alongside extensive altnet deployments; Project Gigabit subsidises rural coverage towards national gigabit-capable targets.
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Resilience: route diversity, ring protection, and rapid optical restoration matter because a single cable cut — anchor drag on a submarine span, a dug-up duct — can sever regional connectivity.
Current Landscape
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UK full-fibre coverage reached 85% of premises by mid-2026 (ISPreview H1 2026 audit, up from 81.9% at end-2025), with gigabit-capable coverage at 91%; Point Topic recorded overall FTTP at 82.9% at the end of Q1 2026.
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Openreach’s FTTP footprint stood at 22.1 million premises at Q1 2026 (about 65% of UK premises), building at roughly 1 million premises per quarter towards its 25-million target for December 2026, with a stated ambition of up to 30 million by 2030; take-up on the built footprint averages ~38%.
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Altnets collectively passed ~46% of UK premises with FTTP by mid-2026, and Project Gigabit contracts (c. 838,000 subsidised rural premises) were about one-third built by July 2026.
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Speed tiers are stepping up: Openreach’s GPON-based network tops out at 1.8 Gb/s, with XGS-PON trials of up to 8.5 Gb/s launched around Guildford in early 2026; Ofcom forecasts gigabit coverage of up to 95% by January 2029, and government targets c. 99% by 2032.
Sources:
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https://www.point-topic.com/post/uk-fttp-premises-in-q1-2026
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https://www.broadbandanalyst.co.uk/articles/openreach-full-fibre-broadband-reaches-20m-premises/