Question

The purpose of cladding is to:
A. Avoid the cross talk during transmission
B. Increase information transmission rate
C. Reduce transmission error
D. Reduce computation error

Answer 1

Recall that cladding is a layer that surrounds the core of an optical fibre, and has a lesser refractive index than the core to facilitate core-confined transmission of the signal via total internal reflection and to prevent straying of signals. Think in terms of how stray signals could “interfere” with the transmission of their neighbouring signals if left unchecked.

Complete step by step answer:
Let us begin by understanding what cladding means.
In a literal sense, cladding is a covering or a coating on a structure or a material. However, the cladding that we are about to discuss is in the context of optical fibres.
Now, an optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. An optical fibre does the same.
Optical fibres usually include a core that is surrounded by a transparent material called cladding. Light is kept in the core by total internal reflection and enables the optical fibre to act as a waveguide to transmit light between the two ends of the fibre.
Now, cladding may be one or more layers of glass or plastic surrounding the core of the optical fibre. Cladding materials are chosen by virtue of their lower refractive index in comparison to the core, which has a higher refractive index. This helps to confine the light to the core of the fibre by total internal reflection which occurs at the boundary between the core and the cladding. This prevents any refraction from occurring at their interface and all the light is internally reflected in the core instead.
Thus, the core always has a greater refractive index than the cladding. The difference between their refractive indices is what causes the mirror-like interface which guides the light back to the core.
Now, crosstalk is an unwanted electronic signal interference that occurs when there is an unnecessary coupling of adjacent signals. This can happen due to improper coupling of transmission media or by signal crossovers.
Cladding ensures that a signal passing through the core of an optical fibre is always confined to the core of this fibre by the mechanism of total internal reflection and prevents the signal from straying into adjacent fibres. Thus, the signal is transmitted down the fibre and does not escape through the sides of the fibre.

So, the correct answer is “Option A”.

Note: Note that fibre optic cables can work without cladding but this offers a lesser guarantee in crosstalk prevention. In some cases, air is used as a natural cladding, since the refractive index of air is much less than the fibre crore and allows total internal reflection to occur. Thus, even if cladding does not exist, the surrounding air can still provide such an effect.