The term fibre optics is comprised of two terms. Fibre and optics. Fibre means a “thread-like structure,” and optics means “light.” It means a thread-like structure through which light will pass. Fibre optics are based on the principle of total internal reflection (in this phenomenon, the light should pass from a denser to a rarer medium, and the angle of incidence should be more than the critical angle).
The main parts of optical fibre are listed hereunder:
- Core
- Cladding
- Jacket
The core is the innermost part of the fiber. It is basically the dense medium through which light will travel. The core is surrounded by an outer layer called the cladding. Similarly, the cladding is covered with a jacket. The jacket, aka cover of the fibre optic cable, is used to protect the optic fibre.
The core of the optical fibre consists of cylindrical glass with a high refractive index. If the laser strikes the interface at an angle greater than the critical angle, the total internal reflection will occur, and the light will reach the other end. This means that light can be confined in the optical fibre over a long distance. No matter what complex shape the fibre forms.
Note: total internal reflection happens between the high refractive index glass and the low refractive index air.
However, optical fibre needs a protective coating. A protective coating is not possible with this configuration. The introduction of protective material will replace the position of the air and cease the total internal reflection phenomenon. An easy way to overcome this issue is to introduce a low refractive index glass above the core glass, known as cladding. This way, the total internal reflection will happen, and you’ll be able to use a protective layer.
Both the core and cladding use silica as their base material. The difference in the refractive index can be achieved by adding different types of dopants. During the transmission of the signal, various losses happen, which result in the failure of transmission of the signal. The signal can’t travel for more than 100 kilometers.
This loss of signal strength is generally called attenuation. Absorption and scattering are the main reasons for signal attenuation. This is why amplifiers and cables after a certain distance are used. They boost the signal strength and allow signals to be transmitted over a long distance.
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