An optical fibre cable consists of several key components:

• Core: The core is the central part of the fibre, made of glass or plastic, through which the light signal travels. It has a higher refractive index than the cladding.
• Cladding: The cladding is a layer of glass or plastic surrounding the core. It has a lower refractive index than the core. The cladding ensures that light is confined to the core through TIR.
• Buffer Coating: A plastic coating that protects the core and cladding from damage.
• Strength Members: These provide mechanical strength to the cable, protecting the fibre from stress and strain.
• Outer Jacket: The outermost layer, providing further protection against environmental factors like moisture and abrasion.

Types of Optical Fibre:

• Single-mode fibre: Has a small core diameter (around 8-10 micrometers). It allows only one mode of light to travel through it. This results in less modal dispersion (spreading of the light pulse) and allows for longer distances and higher bandwidth. Typically used for long-distance telecommunications.
• Multi-mode fibre: Has a larger core diameter (typically 50 or 62.5 micrometers). It allows multiple modes of light to travel through it. This results in more modal dispersion, limiting the distance and bandwidth compared to single-mode fibre. Typically used for shorter distances, such as within a building or campus network.

Table summarizing the differences:

The critical angle is the angle of incidence at which light travelling from a denser medium to a rarer medium is completely reflected. This angle is specific to a particular pair of media.

When light strikes a surface at or above the critical angle, it undergoes total internal reflection. This means that all of the light is reflected back into the denser medium, rather than being refracted into the rarer medium.

• The critical angle is always greater than 0 degrees.
• It depends on the refractive indices of the two media involved.

Total internal reflection occurs at the critical angle because the angle of incidence at which the refracted ray becomes parallel to the normal is the critical angle. When the angle of incidence is greater than the critical angle, the refracted ray no longer exists. Instead, all the light is reflected back into the denser medium.

This phenomenon is directly related to the refractive indices of the two media. Total internal reflection can only occur when light travels from a denser medium to a rarer medium. The refractive index of a medium is a measure of how much the speed of light is reduced in that medium. The greater the difference in refractive index between the two media, the more pronounced the total internal reflection will be.

Diagram:

The diagram should show a ray of light travelling from a denser medium (e.g., water) to a rarer medium (e.g., air). The ray should approach the interface at an angle greater than the critical angle. The diagram should clearly indicate the normal to the interface and the reflected ray should be shown inside the denser medium.