10.8.10 Why Has Optical Fiber Replaced Copper for Long-Distance Communications?
- Why Was Copper Used for So Many Years?
- What Limits the Performance of Copper Cables?
- Why Does Optical Fiber Have Much Lower Attenuation?
- Why Can Optical Fiber Carry So Much More Information?
- Why Doesn't Electromagnetic Interference Affect Optical Fiber?
- Why Is Optical Fiber More Secure?
- What Role Do Optical Amplifiers Play?
- Where Is Optical Fiber Used Today?
- Does Copper Still Have a Future?
- Will Optical Fiber Continue to Evolve?
- Why Has Optical Fiber Transformed Global Communications?
- What Should You Remember?
Short Answer
Optical fibre has replaced copper for most long-distance communication systems because it provides enormously greater bandwidth, much lower attenuation, complete immunity to electromagnetic interference, improved security, and lower lifetime operating costs. Modern optical fibres can carry terabits of data per second over hundreds or even thousands of kilometres using optical amplifiers, making them ideally suited to the Internet, submarine communication cables, and global telecommunications networks. Although copper remains important for many short-distance applications, optical fibre has become the foundation of the world's high-capacity communication infrastructure.
Why Was Copper Used for So Many Years?
For more than a century, copper was the dominant transmission medium for telecommunications.
Early telegraph systems, telephone networks, radio interconnections, and computer networks all relied upon copper conductors because they were inexpensive, mechanically robust, and relatively easy to manufacture. Engineers continually improved copper-based technologies through better insulation, coaxial cable, balanced transmission lines, digital modulation, and sophisticated signal processing.
By the late twentieth century, however, communication demand had grown so rapidly that the physical limitations of copper were becoming increasingly difficult to overcome.
What Limits the Performance of Copper Cables?
Although copper is an excellent electrical conductor, it is not a perfect one.
Electrical signals travelling along copper transmission lines experience several important limitations. These include:
- conductor losses caused by electrical resistance;
- increasing attenuation at higher frequencies because of the skin effect;
- dielectric losses within the insulating material;
- electromagnetic interference from nearby electrical equipment;
- crosstalk between neighbouring cables; and
- limited usable bandwidth.
As communication systems demanded ever higher data rates, these limitations became increasingly significant.
Why Does Optical Fiber Have Much Lower Attenuation?
Instead of carrying electrical currents, optical fibre guides pulses of light.
Modern silica fibres are manufactured from exceptionally pure glass containing extremely few impurities. As a result, light experiences remarkably little absorption or scattering. At the commonly used wavelength of 1550 nm, a modern single-mode fibre typically exhibits an attenuation of only about 0.2 dB/km. By comparison, an electrical transmission line carrying equivalent information rates would experience dramatically greater losses.
Lower attenuation means that repeaters or amplifiers can be spaced much further apart, reducing both construction and operating costs.
Why Can Optical Fiber Carry So Much More Information?
One of the greatest advantages of optical fibre is its enormous bandwidth.
Visible and infrared light occupy frequencies hundreds of thousands of times higher than those used by conventional radio systems. Although communication systems never utilise this entire spectrum, the available bandwidth is still vastly greater than that of copper transmission media.
Furthermore, optical fibres can simultaneously carry many independent wavelengths of light using Wavelength Division Multiplexing (WDM). Each wavelength behaves like a separate communication channel, allowing dozens or even hundreds of high-capacity data streams to share a single fibre.
Modern Dense Wavelength Division Multiplexing (DWDM) systems routinely transport many terabits of information every second over one optical fibre.
Why Doesn't Electromagnetic Interference Affect Optical Fiber?
Copper cables transport electrical signals and therefore interact with external electric and magnetic fields.
Nearby power cables, radio transmitters, lightning strikes, and industrial equipment may all introduce unwanted interference. Optical fibres carry light rather than electrical current. Because glass is an electrical insulator, optical fibres are essentially immune to electromagnetic interference. This immunity makes optical fibre particularly attractive for:
- industrial plants;
- electrical substations;
- hospitals;
- railway signalling systems;
- aircraft;
- military communication systems; and
- environments containing powerful radio transmitters.
Why Is Optical Fiber More Secure?
Optical fibre also provides important security advantages.
Electrical cables naturally radiate small electromagnetic fields that may sometimes be intercepted. Optical fibres radiate virtually no detectable energy during normal operation. Intercepting information generally requires physically accessing the fibre itself, an action that usually introduces measurable losses detectable by network monitoring equipment.
Although no communication medium is completely secure, optical fibre offers a significantly higher degree of protection against unauthorised interception than conventional copper transmission lines.
What Role Do Optical Amplifiers Play?
Early optical communication systems required electronic repeaters to regenerate signals periodically.
Each repeater converted the optical signal into electrical form, amplified it, reconstructed the digital data, and converted it back into light. Modern systems instead employ Erbium-Doped Fibre Amplifiers (EDFAs). These devices amplify the optical signal directly without converting it into electrical form.
Optical amplification dramatically simplifies long-distance communication systems while supporting enormous transmission capacities across many optical wavelengths simultaneously.
Where Is Optical Fiber Used Today?
Optical fibre now forms the backbone of almost every major communication network.
Typical applications include:
- international Internet backbone networks;
- submarine communication cables;
- metropolitan fibre rings;
- fibre-to-the-home (FTTH);
- cable television distribution;
- mobile phone backhaul;
- cloud computing data centres;
- scientific research networks; and
- defence communication systems.
Virtually every international telephone call, video stream, cloud service, or Internet transaction depends at some stage upon optical fibre.
Does Copper Still Have a Future?
Despite the extraordinary success of optical fibre, copper has by no means disappeared.
Copper remains well suited to many applications where communication distances are relatively short. Examples include:
- Ethernet local-area networks;
- Power over Ethernet (PoE);
- building wiring;
- USB and HDMI connections;
- printed circuit boards;
- radio-frequency interconnections;
- industrial control systems; and
- many automotive communication networks.
Copper also has one important advantage that optical fibre cannot provide—it can deliver electrical power as well as data. This capability makes copper indispensable for many end-user connections.
Rather than competing directly, copper and optical fibre increasingly complement one another.
Will Optical Fiber Continue to Evolve?
Optical communication technology continues to advance rapidly.
Current research focuses on:
- higher-order modulation techniques;
- coherent optical communication;
- space-division multiplexing;
- multicore fibres;
- hollow-core fibres;
- improved optical amplifiers; and
- photonic integrated circuits.
These developments are expected to increase transmission capacity still further while reducing both equipment cost and power consumption.
Although the underlying principle of guiding light by total internal reflection remains unchanged, the performance of optical communication systems continues to improve year after year.
Why Has Optical Fiber Transformed Global Communications?
Optical fibre has fundamentally changed the way the world communicates.
Its combination of enormous bandwidth, exceptionally low attenuation, immunity to electromagnetic interference, excellent security, and outstanding reliability has enabled the explosive growth of the Internet, cloud computing, mobile communications, online entertainment, and global digital commerce.
Without optical fibre, today's interconnected digital society simply could not exist.
What Should You Remember?
- Optical fibre has replaced copper for most long-distance communication because it offers much greater bandwidth and much lower attenuation.
- Light experiences far less loss in high-purity silica fibre than electrical signals experience in copper conductors.
- WDM and DWDM allow many independent communication channels to share a single optical fibre.
- Optical fibre is immune to electromagnetic interference and provides improved communication security.
- EDFAs allow optical signals to be amplified directly without electronic regeneration.
- Copper remains important for short-distance communication and applications requiring electrical power delivery.
- Modern global communication networks rely upon optical fibre as their primary transmission medium, while copper continues to serve many local access and equipment interconnection roles.