Difference Between Optical Fibre and Coaxial Cable

The computers and other electronic devices transmit the data from one to another device in the form of signals and using a transmission media. The transmission media can be fundamentally categorized into two types guided and unguided.

Unguided media is a wireless communication which carries electromagnetic waves by making use of air as a medium and also in the vacuum, it can transmit data and without requiring a physical conductor. Guided media need a physical medium to transmit signals such as wires. Guided media is classified in three ways twisted pair cable, coaxial cable and fibre-optic cable. The crucial difference between optical fiber and coaxial cable is that an optical fiber is used for the transmission of the optical signal and a coaxial cable is used for the transmission of an electrical signal. This article explains you the major difference between optical fibre and coaxial cable.

Definition of Optical Fibre

Optical fibre is a type of guided media. It is made up of glass, silica and plastic, where the signals are transmitted in the form of light. Optical fibre uses the principle of total internal reflection to guide light through the channel. The structural composition of an optical fibre includes a glass or ultrapure fused silica surrounded by a cladding of less dense glass or plastic. The cladding is covered with a buffer either loose or tight, to protect it from moisture. Finally, the whole cable is then encased by an outer covering made by a material such as teflon, plastic or fibrous plastic etc. Fibre optics cable is made up of glass and is delicate which makes it difficult to install. The repeater is placed at 2 km to 20 km depending on the type of the fibre. There is two types of optical fibre, multimode and single mode. Multimode fibre has two variations, step index and graded index fibre. LED and lasers can be used as the light source of the optical cable.

anatomy of undersea fiber optic cable materials and construction

Definition of Coaxial Cable

Coaxial cables are also known as coax and are guided media that are used for transmission of electrical signals to some distances. Coaxial cables are basically conductors that allow electrons to flow through it. It is made up of a conductor (usually copper) placed at the centre or core which is surrounded by an insulating sheath. The sheath is also encased in an outer conductor of a metal braid, foil or a combination of the two. The external metallic wrapping acts as a shield against the noise and completes the circuit as the second conductor. The outer metallic conductor is also enclosed in a plastic covering to protects the whole cable. Coaxial cable is a good alternative to an ethernet cable. The coax cables are most popularly used in the cable TV to distribute the TV signals.

coax cable components minearc 1024x543 1

Comparison Chart

Basis for comparisonOptical FibreCoaxial Cable
BasicTransmission of the signal is in optical form (light form).Transmission of the signal is in electrical form.
Composition of the cableGlass and plasticsPlastic, metal foil and metal wire (usually copper).
Losses in cableDispersion, bending, absorption and attenuation.Resistive, radiated and dielectric loss.
EfficiencyHighLow
Cost
Highly expensive
Less expensive
Bending effectCan affect the signal transmission.Bending of wire does not affect the signal transmission.
Data transmission rate2 Gbps44.736 Mbps
Installation of the cableDifficultEasy
Bandwidth provided
Very high
Moderately high
External magnetic fieldDoesn’t affect the cableAffects the cable
Noise immunityHighIntermediate
Diameter of the cableSmallerLarger
Weight of the cableLighterHeavier comparatively

Key Differences Between Optical Fiber and Coaxial cable

  • An optically transmitted signal undergoes less attenuation as compared to an electrical signal transmitted through a coaxial cable.
  • The coaxial cables are low-cost cables whereas, fiber cables are expensive.
  • Optical fibers are more efficient as they allow long distance as well as fast signal transmission. While coaxial cables are less efficient.
  • Optical cables are lightweight cables whereas coaxial cables are somewhat heavy in weight and are comparatively thicker than optical fiber cable.
  • The bandwidth utilization factor for signal transmission is very much higher in case of optical fiber than a coaxial cable.
  • Installing an optical fiber is a difficult task in comparison to the installation of any coaxial cable.
  • In an optical fiber, the transmitted signal is not affected by the external magnetic field. While in the case of coaxial cable, the transmitted signal gets somewhat affected by the external magnetic field.

Advantages and Disadvantages Optical Fibre

Advantages 

  • Noise resistance – As fibre optic cable uses light rather than electricity, noise is not an issue. External light probably could create some interference, but that is already blocked from the channel by the outer jacket.
  • Less attenuation – The transmission distance is remarkably greater than that of any other guided media. In optical fibre cable, a signal can run for miles without needing regeneration.
  • Higher bandwidth – Fibre-optic cable can carry higher bandwidth.
  • Speed – It provides higher transmission rates.

Disadvantages 

  • Cost – Optical fibre is expensive because it needs to be manufactured precisely and a laser light source costs a lot.
  • Installation and maintenance – A rough or cracked core of the optical fibre can diffuse the light and cease the signal. All the joints must be perfectly polished, aligned and sealed light-tight. It makes use of unsophisticated tools for cutting and crimping, which makes it more difficult to install and maintain.
  • Fragility – Glass fibre is more delicate and easily broken than a wire.

Advantages and Disadvantages of Coaxial Cable

Advantages

  • Frequency characteristics – Coaxial cable has a better frequency characteristic as compared to twisted pair cable.
  • Susceptibility towards interference and crosstalk – It is less susceptible to interference and crosstalk because of concentric construction of the cable.
  • Signaling – Coax cable supports both analog and digital signalling.
  • Cost – It is cheaper than optical fibre.

Disadvantages

  • Distance traveled by the signal – A repeater is required for every kilometer when the communicating devices are placed at a longer distance.

Applications

Optical fiber

It is used to transmit signals of optical frequency, thus finds applications in HDTVs, aircraft and in the medical field for the surgical purpose.

Coaxial Cable

It is used to transmit radio frequency signals, hence finds applications in cable TV signal transmission as well as in internet and telephone connections.

Conclusion

Both optical fiber and coaxial cable are used for signal transmission. Optical fibre is more efficient than coaxial cable in terms of data transmission speed, noise and interference resistance, dimensions, bandwidth, losses etc. But, coaxial cable is cheaper, easily available and installed, and bending of the cable does not affect the signalling in the cable.

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