What is Fibre Optic Cable?
Fibre optic cables are mainly used to transmit information over long distances with minimum loss. The information through optical fibres is transmitted in the form of light pulses. The core of the optical fibres is made of glass or plastic. The fibre optic networks mainly work on the principle of total internal reflection. Here, the incident angle should be more than the critical angle. The diameter of the optical fibre is equal to the human hair. The fibre optic cables can transmit information faster than traditional electric cables. This article describes the meaning and definition of fibre optics, parts of optical fibre, types, classification and applications of fibre-optic internet, phone and TV services in detail.
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Parts of Fibre Optic Cables
The fibre optic cables are mainly made of four parts, they are listed below.
Core
Cladding
Buffer
Jacket
Core: The core is the inner part of the optical fibre. It is the medium, which allows the light to pass through it. The core region has the highest refractive index in the optical fibre. The core is made up of Glass or Plastic.
Cladding: Cladding is the substance that is covered over the core of the optical fibre. It has a lower refractive index while compared to the core of the fibre. The cladding of the Optical fibre is made up of Glass / Plastic.
Buffer: The Buffer is the moisture substance that is coated over the surface of the cladding. They are mainly used to provide flexibility to the optical fibre’s core and cladding.
Jacket: The jacket is the outer surface of the optical fibre. They act as a shield for protecting the inner part of the fibre.
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Types of Fibre Optic
The optical fibre cables are classified based on various factors like the refractive index, materials used, and mode of propagation of light.
Types of Optic Fibre Based on Refractive Index
Step Index Fiber: The index of refraction will sharply decrease from the core to cladding.
Graded Index Fiber: The Index of refraction will be maximum at the centre of the core and radically decreases from core to cladding.
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Types of Optic Fibre Based Based on Core Material
Glass Fiber: The core and cladding of the optical fibre are made of glasses.
Plastic Fiber: The Core and cladding of the optical fibre is made of plastic.
Classification Based on Mode of Propagation
Single Mode Fiber: The core diameter of the single-mode fibre is small. The light wave can travel a longer distance with smaller refraction.
Multimode Fiber: The core diameter for multimode fibre is large. The loss during the light travel through its core is high. Also, It is preferable to transfer for a short distance.
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Based on Mode of Propagation and Refractive Index
The optical fibres are classified into four types based on their mode of propagation and refractive index. They are listed below.
Step index-single mode fibres
Graded index-Single mode fibres
Step index-Multimode fibres
Graded index-Multimode fibres
Fibre Optic Cable Short Note
Various types of fibre optic cables are mainly utilized to provide internet connectivity to the home or offices. Here, the optic cable running from the network hub reaches near the home or straight to home for internet connectivity. In the optical fibre network, Fiber to the Home (FTTH) or Fiber to the Premises (FTTP) is the fastest type of network. It can provide a direct connection to houses, apartments, and businesses.
Fibre to the Curb (FTTC) is another type of fibre optic network, which provide a partial connection. Here, the optical cables reach the crub near the home or businesses place and the copper cables will carry the signals from the crub to the rest of the way.
Fibre to the Building (FTTB) is also a type of fibre optic network, which distributes the signal for the offices and homes located in a particular location.
Facts and Advantage Of Fibre Optic Cable
The optical fibre will allow larger bandwidth. While the copper wire does not allow such a great bandwidth,
The data can be transmitted through a long distance with the help of Optical fibre. This can be used for undersea transmission.
The Optical fibre can transfer data at high speed while compared to copper cable. The optical fibre will transfer data just 31% less than the speed of light.
Usually, optical fibres are immune to external weather, temperature..etc Unlike copper wire, optical fibre will not be affected by electromagnetic induction.
Since the optical fibre is flexible, the maintenance charge is less while compared to copper wires. Also, Optical fibre is less prone to damage and breakage.
The maintenance cost for the optical fibre is less while compared to the copper wire, even the initial installation cost for optical fibre is high.
The optical fibres are thin and non-flammable. So, it is not sensitive to the external surface.
The power required to transfer information through the optical fibre is less, while compared to other traditional methods.
The data from optical fibre are secure, and it cannot be decoded for hacking.
It is possible to avoid losses like heat loss, eddy current loss...etc while using optical fibre for transmission.
This article described the meaning and definition of fibre optics with the types of fibre optics, parts of optical fibre and their advantages in detail.
FAQs on Fibre Optics
1. What is a fibre optic cable and what are its main components?
A fibre optic cable is a network cable used for high-speed data transmission over long distances. It contains strands of glass or plastic fibres inside an insulated casing. The primary components are:
- Core: The innermost part made of glass or plastic through which light pulses travel. It has the highest refractive index.
- Cladding: A layer of material surrounding the core with a lower refractive index, which is essential for total internal reflection.
- Buffer: A protective coating over the cladding that shields it from moisture and physical damage.
- Jacket: The outermost layer of the cable that protects it from external environmental factors.
2. How does an optical fibre transmit information using light?
An optical fibre transmits information in the form of light pulses based on the principle of total internal reflection (TIR). Light from a source enters the core, which has a higher refractive index than the surrounding cladding. As the light travels, it strikes the boundary between the core and cladding at an angle greater than the critical angle, causing it to reflect back into the core instead of escaping. This process of continuous reflection allows the light signal to propagate along the entire length of the fibre, even around bends, with minimal loss.
3. What are the main types of optical fibres based on their structure and mode of propagation?
Optical fibres are primarily classified based on their refractive index profile and the number of modes they can propagate:
- Based on Refractive Index: Step-Index Fibre (sharp change in refractive index between core and cladding) and Graded-Index Fibre (gradual decrease in refractive index from the core's centre to the edge).
- Based on Mode of Propagation: Single-Mode Fibre (a very thin core that allows only one light path, used for long distances) and Multi-Mode Fibre (a larger core that allows multiple light paths, used for shorter distances).
4. What are the key applications of fibre optic technology?
Fibre optics are essential in modern technology for various applications, including:
- Telecommunications: Providing high-speed internet connections (e.g., FTTH - Fibre to the Home), telephone services, and television broadcasting.
- Data Networking: Used in local area networks (LANs) and data centres for high-bandwidth data transfer.
- Medical Field: Used in endoscopes and lasers for non-invasive surgeries and diagnostics.
- Military and Aerospace: For secure and reliable communication in aircraft, ships, and other sensitive environments due to its immunity to interference.
5. Why is the cladding in an optical fibre necessary, and why must its refractive index be lower than the core's?
The cladding is crucial because it creates the necessary conditions for total internal reflection (TIR) to occur. For TIR to happen, a light ray must travel from a denser optical medium to a rarer one. By having a lower refractive index than the core, the cladding acts as the rarer medium. This ensures that when light travelling through the denser core strikes the core-cladding boundary at a sufficient angle, it is completely reflected back into the core, allowing the signal to be guided along the fibre with minimal loss.
6. What are the main advantages of fibre optic cables over traditional copper wires?
Fibre optic cables offer several significant advantages over copper wires:
- Higher Bandwidth: They can carry significantly more information than copper cables of the same diameter.
- Faster Speed: Data travels as light pulses, which is much faster than the electrical signals in copper wires.
- Less Signal Degradation: Signals can travel much longer distances without needing to be boosted.
- Immunity to Interference: They are immune to electromagnetic interference, ensuring a cleaner and more reliable signal.
- Enhanced Security: It is extremely difficult to tap into a fibre optic cable without being detected, making data transmission more secure.
7. How does the 'mode of propagation' differentiate single-mode and multi-mode fibres?
The 'mode of propagation' refers to the different paths that light rays can take as they travel down the fibre. Single-mode fibres have a very narrow core (typically 8-10 micrometres) that forces light to travel in a single path or 'mode'. This minimises signal distortion and allows for high-speed, long-distance transmission (e.g., across oceans). In contrast, multi-mode fibres have a larger core (50 micrometres or more) that allows light to travel along multiple paths simultaneously. This can cause the signal to spread out (dispersion), making it more suitable for shorter distances, such as within a building or campus.
8. If light travels in a straight line, how can an optical fibre guide it around a bend?
While it's true that light propagates in a straight line, an optical fibre guides it along a curved path using total internal reflection (TIR). Inside the fibre, the light signal doesn't bend; instead, it travels in a series of straight lines, reflecting off the inner wall of the core. Each time a light ray hits the core-cladding boundary, it bounces off at an angle and continues in a new straight path until it hits the boundary again. This zigzag path effectively contains the light within the core and steers it along the physical route of the cable, even around corners.
