Fibre Optics: The Backbone of Modern Telecommunications

Answering the question: why fibre is today’s telecom backbone?

Since the early 2000s, global telecommunications networks have steadily replaced traditional copper cables with fibre optic infrastructure to handle the explosive growth in internet, mobile, and cloud computing traffic. What was once a technology reserved for long-haul trunk routes has now become essential at every layer of modern telecommunications, from intercontinental links to the cables running into homes and businesses.

More than 99% of intercontinental data now travels through submarine fibre optic cables, a network that has grown from the first transatlantic TAT-8 cable in 1988 to over 1.4 million kilometres of undersea routes today. Major upgrades throughout the 2010s and 2020s have pushed aggregate capacities into the hundreds of terabits per second, with systems like Microsoft and Facebook’s MAREA cable delivering 200 Tbps across the Atlantic.

National backbones, 4G and 5G mobile networks, and most data centre interconnects now rely on optical fibers for the capacity, speed, and reliability that copper simply cannot match. Consider what happens when you stream a film, join a video conferencing call, or access cloud computing services: the data travels predominantly through fibre networks, even if the last few metres to your device are wireless.

The shift became especially visible after 2020, when remote work and video streaming demands surged by more than 40% almost overnight. Fibre networks absorbed this traffic spike without widespread failures, unlike congested copper-based systems in many areas.

This article will explain what fibre optics are, how they work, and why they have become essential to modern telecommunications infrastructure. Whether you’re evaluating network functionality for your organisation or simply curious about the technology enabling your high speed internet connections, understanding fibre is now fundamental.

What is fibre optics in telecommunications?

Fibre optics refers to the use of ultra-thin strands of glass or plastic to transmit data as pulses of light rather than electrical signals. This technology has revolutionised how we carry signals across everything from intercontinental backbones to local access networks.

A single optical fiber is remarkably small. The core—the light-carrying centre—is typically about 8-10 micrometres in diameter for single mode fiber (roughly the width of a human hair), or 50-62.5 micrometres for multimode variants. This core is surrounded by a 125-micrometre cladding layer that reflects light back into the core, keeping it confined as it travels.

Key structural components of fibre optic cables:

• Core: The central glass or plastic strand where light signals travel, made of highly transparent silica

• Cladding: A layer of glass with a slightly lower refractive index that ensures total internal reflection

• Coating/Buffer: Protective layers shielding against moisture, abrasion, and environmental factors

• Strength members: Aramid yarns or steel providing tensile support during installation

• Outer jacket: The final protective layer, designed for specific deployment environments

Fibre optic cables bundle many individual fibres together—often dozens or hundreds—protected by these strength members and outer jackets for deployment across long distances.

Primary telecom applications:

• Backbone internet links connecting cities, countries, and continents

• Metro rings distributing traffic within metropolitan areas

• Access networks bringing connectivity to neighbourhoods

• Fibre-to-the-home (FTTH) deployments delivering gigabit services directly to residences

• Data centres interconnects enabling cloud computing and content delivery

The resulting infrastructure supports the fast and reliable transmission of more data than any previous technology, with minimal signal loss over distances that would render copper cables unusable.

How fibre optics work: from light pulses to global connectivity

Understanding how fiber optic cables work reveals why they’ve become indispensable for modern telecommunications. The process transforms digital information into light, sends it across vast distances, and converts it back for use at the destination.

The transmission process:

• Signal conversion: At the transmitter, lasers or LEDs convert electrical signals into light signals at specific telecom wavelengths (typically 1310 nm, 1550 nm, or within the C-band and L-band ranges)

• Light propagation: Light pulses enter the fibre core and travel via total internal reflection—the cladding’s lower refractive index causes light to bounce off the core-cladding boundary rather than escape

• Minimal attenuation: Modern single-mode fibres achieve loss rates of approximately 0.2 dB/km at 1550 nm wavelength, far superior to copper’s exponential signal degradation over distance

• Amplification: Erbium-doped fibre amplifiers (EDFAs) boost optical signals directly without converting to electrical form, enabling spans of 50-100 km between amplification points

• Reception: At the destination, photodetectors convert light pulses back into electrical signals for processing

Unlike copper cables, fibre can carry data tens or hundreds of kilometres with remarkably low attenuation. This makes it possible to span continents with relatively few repeater stations.

Wavelength-division multiplexing (WDM):

The real power of fibre comes from multiplexing—sending multiple data streams simultaneously over the same physical strand. Dense WDM systems transmit 40-80 different wavelengths through a single fibre pair, with each wavelength carrying its own data channel.

This technique has enabled record-breaking capacities. Bell Labs demonstrated transmission exceeding 100 petabit × km/s, while commercial systems routinely achieve multi-terabit aggregate throughput on single fibre pairs. The result is ultra fast speeds that scale as demand grows, simply by adding more wavelengths.

Why fibre optics have become the telecom backbone

Fibre has displaced copper in backbone and high-capacity networks because of a combination of advantages that no alternative technology can match. For internet service providers, enterprises, and government agencies alike, these benefits make fibre the preferred choice for critical role infrastructure.

Speed and capacity:

• Commercial systems now support 100 Gbit/s, 400 Gbit/s, and beyond per wavelength

• Aggregate capacities reach multi-Tbit/s per fibre pair using WDM technology

• A single fibre pair can equal thousands of copper pairs in transmission capacity

• Demonstrated systems have achieved 25.6 Tbps, with laboratory records far higher

Bandwidth scalability:

• Traffic growth driven by video streaming, cloud computing, and mobile data demands continues accelerating

• Global data is projected to reach 175 zettabytes annually by 2025

• Fibre networks scale by adding wavelengths, not by laying new cables

• Future proof technology that can accommodate increasing data demands for decades

Long-distance performance:

• Single-mode fibre enables unrepeated spans exceeding 100 km routinely, with some systems reaching 10,000 km

• Fewer amplifiers and regenerators reduce operational costs and potential failure points

• Ideal for national backbones, intercity links, and undersea cables spanning oceans

• Copper requires regeneration every few kilometres at high data rates

Reliability advantages:

• Complete immunity to electromagnetic interference and electrical interference

• No crosstalk between adjacent fibres in dense cable bundles

• Unaffected by lightning, power surges, or proximity to high-voltage equipment

• Performs consistently in environments that would degrade copper—near power lines, industrial equipment, or in urban density

Security benefits:

• Tapping a fibre without detection is significantly harder than with copper

• No electromagnetic emissions to intercept remotely

• Essential for financial networks, government communications, and critical infrastructure

• Supports encryption overlays and emerging quantum key distribution

Cost-effectiveness over time:

• Higher initial installation cost offset by dramatically lower maintenance requirements

• Lower energy consumption in transmission equipment (approximately 1 pJ/bit versus copper’s 100 pJ/bit)

• Longer usable lifespan than copper infrastructure

• Capacity upgrades often require only equipment changes, not new cabling

Key applications of fibre optics in modern telecommunications

Fibre now underpins everything from international connectivity to last-mile broadband. The applications span virtually every aspect of how we communicate, work, and access information in the digital age.

Submarine cables:

• Continental backbones linked by undersea fibre systems deployed since the late 1980s

• Modern systems like MAREA (Microsoft/Facebook, 2018) carry 200 Tbps over 6,600 km

• Google’s Dunant cable (2021) uses space-division multiplexing for 250 Tbps capacity

• SEA-ME-WE and other systems connect Europe, Asia, Africa, and the Americas

• Handle 99% of international data traffic, enabling global connectivity

National and regional backbones:

• Fibres connecting major cities, internet exchange points, and large scale networks

• Typically deployed along railways, motorways, and utility routes

• Enable reliable internet connections between population centres

• Support wholesale capacity for internet service providers and enterprises

Metro and access networks:

• Fibre rings inside metropolitan areas connecting mobile base stations and exchanges

• Enterprise building connections for high speed data transmission

• Local exchange links aggregating residential and business traffic

• Foundation for reliable transmission across urban environments

Fibre-to-the-home (FTTH) and fibre-to-the-premises:

• Passive optical networks (PON) delivering gigabit services to residences

• Global FTTH connections projected to exceed 1 billion by 2025

• Average FTTH speeds reached 1.5 Gbps in 2024

• Enables 4K/8K video streaming, online gaming, and virtual reality applications

• Supports multiple simultaneous users and smart home devices

Mobile backhaul and fronthaul:

• Fibres linking 4G LTE and 5G base stations to core networks

• Essential for achieving low latency (sub-microsecond requirements for 5G)

• 5G fronthaul demands 10 Gbps+ with <1 µs latency

• Enables mobile networks to deliver high speed internet to smartphones

Data centre interconnects (DCI):

• Short-haul links between data centres within metro areas

• Long-haul connections between regional data centres for cloud services

• Critical for content delivery networks serving video streaming platforms

• Supports synchronous replication and disaster recovery for enterprises

• Enables the distributed architecture of modern cloud computing

These applications collectively enable the services people rely on daily: video conferencing for remote work, cloud-based business applications, streaming entertainment, and the responsive mobile networks that keep people connected.

Types of fibre optic cables and where they’re used

Telecoms deploy different fibre types and cable constructions depending on distance, capacity requirements, and installation environment. Understanding these variations helps explain why network infrastructure choices matter.

Single-mode fibre (SMF):

• Core diameter of approximately 9 µm allows only one light path

• Optimised for long distances—backbone routes, submarine cables, and metro networks

• ITU-T standards like G.652 (standard SMF) and G.655 (non-zero dispersion-shifted) define specifications

• Used in FTTH deployments where future capacity growth is anticipated

• Minimal modal dispersion enables higher bit rates over longer spans

Multimode fibre (MMF):

• Core diameters of 50 µm or 62.5 µm permit multiple light paths

• Suited for shorter runs inside buildings, campuses, and data centres

• OM3, OM4, and OM5 categories define performance grades for different distances and speeds

• Less expensive transceivers offset by distance limitations (typically under 2 km)

• Common in data centre patch cords and enterprise LAN connections

Outdoor versus indoor cables:

• Outdoor cables feature armouring, water blocking, and UV-resistant jackets

• Indoor cables use fire-rated jackets (plenum or riser rated) for building codes

• Indoor designs often have tighter bend radius capabilities for routing through conduits

• Hybrid cables exist for transitions between outdoor and indoor environments

Deployment-specific designs:

• Aerial cables: Designed for pole-mounted installation with self-supporting or lashed configurations

• Duct cables: Optimised for pulling through underground conduits, often with low-friction jackets

• Direct-buried cables: Armoured designs for installation without protective conduits

• Submarine cables: Heavily armoured with multiple protection layers for ocean floor deployment

Bend-insensitive fibres:

• Modern designs tolerate tighter routing without significant signal loss

• Essential for congested ducts, cabinets, and indoor installations

• Allow fibre deployment in spaces previously unsuitable for optical cables

• Reduce macrobend losses that traditionally plagued tight-radius installations

The choice between these options affects both performance and total deployment cost. Long-haul trunk cables between cities use very different constructions than the patch cables connecting servers in a data centre rack.

Fibre optics and the evolution of telecom networks (4G, 5G, and beyond)

The rise of smartphones, cloud services, and streaming—particularly after 2010—has driven exponential growth in backhaul traffic carried over fibre network infrastructure. Every generation of mobile technology has increased fibre dependence rather than reducing it.

4G LTE era (2010s):

• Rollouts dramatically increased demand for fibre-based mobile backhaul

• Cell sites required far more capacity than 3G predecessors

• Operators began replacing microwave backhaul with fibre where economically viable

• Laid groundwork for the fibre infrastructure that 5G would later require

5G network requirements:

• Dense small-cell architectures require fibre to far more locations than macro-only networks

• Fronthaul connections to remote radio units demand both high capacity and ultra-low latency

• 5G NR specifications require sub-millisecond transport latency for many use cases

• Centralised and virtualised RAN architectures depend on robust fibre connectivity

• Each small cell may require 10 Gbps+ fronthaul capacity

Fixed-mobile convergence:

• Operators increasingly share core fibre infrastructure across mobile, broadband, and enterprise services

• Common transport networks reduce duplication and operational costs

• Enables unified service delivery regardless of access technology

• Fibre backbone serves as the single high-capacity foundation

Emerging telecom use cases:

• Edge computing nodes: Distributed processing requires fibre links to numerous edge locations

• Ultra-reliable low latency communication (URLLC): Industrial automation, remote surgery, and autonomous vehicles need guaranteed low-latency fibre paths

• Massive IoT deployments: Aggregating sensor data from smart cities and environmental monitoring applications

• Private 5G networks: Enterprise deployments requiring dedicated fibre backhaul

Telefónica and other major operators highlight that fibre’s stability is essential for AI-driven data centres, which are projected to consume 8% of global power by 2030.

The pattern is clear: each wireless generation requires more fibre, not less. The “wireless” networks that consumers experience depend entirely on wired fibre infrastructure behind the scenes.

Challenges in deploying and operating fibre telecom networks

While fibre offers tremendous advantages, operators face practical challenges when rolling it out at scale. These obstacles explain why fibre buildout takes time and significant investment, especially in difficult areas.

Civil works and rights-of-way:

• Trenching, duct installation, and street works represent the majority of deployment costs

• Permitting processes in cities can take months or years

• Coordination with utilities, transport authorities, and local governments adds complexity

• Cross-border routes require negotiating multiple regulatory frameworks

• Estimated fibre costs run 3-5x higher than copper per kilometre installed

Rural and remote extension:

• Low population density makes per-premises costs prohibitive for commercial returns

• Difficult geography—mountains, water crossings, remote islands—multiplies expense

• Often requires public-private partnerships or government subsidies to proceed

• Sparse coverage still leaves gaps in broadband networks globally

Technical management:

• Signal attenuation accumulates over long distances, requiring amplification planning

• Chromatic and polarisation-mode dispersion limit bit rates above 100 Gbps on older fibres

• Nonlinear effects like four-wave mixing cap ultra-high capacities at extreme distances

• Fibre ageing and environmental factors require regular testing and maintenance

• Fusion splicing demands precision equipment and trained technicians

Workforce and skills:

• Shortage of trained fibre splicers and installers in many regions

• Installation quality directly impacts long-term network performance

• Safety standards for handling and installation must be strictly followed

• Network engineers need expertise in optical transmission systems and monitoring

Physical vulnerability:

• Construction work and dig-ins cause 10-20% of network outages annually

• Natural disasters—earthquakes, hurricanes, flooding—can sever routes

• Submarine cables face risks from anchors, fishing activity, and geological events

• Operators deploy route diversity and protection switching to mitigate single points of failure

• Bending losses in tight radii remain a concern in congested installation environments

Despite these challenges, the benefits of fibre have consistently outweighed the obstacles. Investment continues to grow as operators recognise that no alternative technology can meet future data demands.

Future directions: how fibre will shape tomorrow’s telecommunications

Fibre capacity is still far from exhausted, and ongoing research ensures it will continue to underpin telecom innovation through the 2030s and beyond. The technology is evolving on multiple fronts simultaneously.

Higher-capacity transmission:

• Coherent optics and advanced modulation formats enabling 800 Gbit/s and 1.6 Tbit/s per wavelength

• Industry projecting 400G+ coherent optics as standard by 2026

• Aggregate capacities approaching exabits on single fibres in laboratory demonstrations

• Photonic integration delivering pluggable 1.6 Tbps transceivers

Next-generation fibre designs:

• Hollow-core fibres guiding light through air rather than glass, reducing latency by approximately 30%

• Multi-core fibres with multiple light-carrying paths in a single strand

• Demonstrations of 10,000 km hollow-core transmission achieved in 2024

• Potential to overcome current capacity limits approaching Shannon limits

5.5G and 6G networks:

• Even denser cell deployments requiring more fibre termination points

• More stringent latency and reliability requirements for advanced applications

• Terahertz frequency bands demanding extremely low-latency backhaul

• Integrated sensing and communication applications dependent on fibre backbone

Quantum communication integration:

• Specialised fibres carrying quantum keys alongside conventional traffic

• Quantum key distribution enabling theoretically unhackable encryption

• Critical for financial services, government agencies, and defence applications

• Hybrid networks blending quantum security with classical high-capacity transport

Software-defined and open optical networking:

• Disaggregated architectures reducing vendor lock-in

• Programmable networks adapting capacity dynamically to traffic patterns

• Open interfaces enabling multi-vendor interoperability

• More flexible management of large scale networks

Investment trajectory:

• Industry forecasts fibre investment surging to $200 billion annually by 2030

• Space-air-ground integrated networks blending satellite with terrestrial fibre

• Coherent PON targeting 50 Gbps symmetric FTTH by 2028

• Continued expansion of broadband networks to underserved areas globally

The enduring foundation:

• Regardless of how wireless standards evolve, fibre optics will remain the physical backbone of global telecommunications networks

• Every 5G, 6G, and beyond wireless innovation requires more fibre, not less

• The fundamental physics—light signals through thin strands of glass—offers capabilities no alternative can match

• Global communication networks will depend on fibre infrastructure for decades to come

Key takeaways

Aspect	Summary
What fibre is	Ultra-thin strands of glass or plastic carrying light pulses to transmit data
Core advantage	99% of intercontinental data travels via fibre with minimal signal loss
Speed capability	100 Gbps to 400 Gbps+ per wavelength, scaling via WDM to multi-Tbps
Distance performance	0.2 dB/km loss enables spans of 100+ km without regeneration
Key applications	Submarine cables, national backbones, mobile backhaul, FTTH, data centres
5G dependency	Dense small cells and fronthaul require extensive fibre deployment
Future direction	Hollow-core fibres, 1.6 Tbps transceivers, quantum integration

Fibre optic technology has transformed from a specialised long-haul solution into the essential foundation of global telecommunications. Whether you’re streaming content, joining a video call, or accessing cloud services, the data travels predominantly through fibre—often across multiple continents—before reaching you.

Understanding this infrastructure matters for anyone making technology decisions, planning network upgrades, or simply wanting to grasp how the digital age actually works. The thin strands of glass that carry our communications represent one of humanity’s most remarkable engineering achievements, enabling fast data transmission at scales that would have seemed impossible just decades ago.

As data demands continue growing and new applications emerge—from virtual reality to quantum computing to smart cities—fibre optics will remain central to delivering the capacity, speed, and reliability that global connectivity requires.