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How Does a Fiber Optic Cable Work?

We Have an Easy Explanation on How a Fiber Optic Cable Works

Whether it is Internet broadband connections, telephone systems, or medical imaging, fiber optics technology has found its importance in each and every field.
Shah Newaz Alam
Last Updated: Jan 11, 2019
The technology of fiber optics has eased up communication with several of its advantages. Optical fibers allow long distance communication at higher bandwidths, in comparison to other forms of communication.
What is a Fiber Optic Cable Made of?
Any technology that is used for communication uses the principle of energy conservation. In fiber optics, data is transferred when it is transformed in the form of light pulses. A fiber optic cable is made up of hundreds of pure thin strands of glass. These strands of glass have a width of one tenth of the size of a human hair.
For understanding the principle used, we will consider a single-mode optical fiber. This is a type of cable that is used in Internet, TV, and telephone connections. It can be divided into three parts: core, cladding, and buffer.
The center most part is called the core, which is made up of pure glass and carries the information. The plastic covering above it, which causes the reflection of light signals is called cladding, and the sheathing that protects it is called buffer coating. In some cases, a tough buffer layer may be surrounded by a jacket layer to add to its strength.
In a single-mode fiber, the core is about 8 - 10 microns in diameter, which is equivalent to the millionth of a meter; that small is its size. With this, the information can be carried over 100 km.
Working of the Cable Explained
The principle that is used for transmission of light pulses or photons through an optical fiber is that of 'Total Internal Reflection'. When light travels from a medium of lower refractive index to that of a higher refractive index, it bends towards the normal. The normal is a line that is perpendicular to the interface of two mediums.
However, when light travels from a medium of higher refractive index to that of a lower one, it bends away from the normal. The angle made by the incident ray to the normal is called the angle of incidence, and the angle made by the refracted ray with the normal at the point of incidence in the other medium is called the angle of refraction.
Now, consider that the light is traveling from a medium with higher refractive index to that of a lower refractive index. As the angle of incidence increases, the angle of refraction also increases.
Now, if the angle of incidence is increased to a point that the angle of refraction becomes perpendicular to the original angle of refraction, i.e. almost parallel to the interface of the two media, then this particular angle of incidence is called the critical angle.
If this angle is further increased beyond this particular point, then the refracted light will be returned to the same medium, i.e. reflected. This is the process of total internal refraction.
What happens in fiber optics is that the light is sent at such an angle, almost parallel to the optical fiber, that it goes through the process of total internal reflection and travels through hundreds of kilometers.
Besides, as we all know that the highest speed of any form of energy is that of light. So, it has to be the fastest way of communication. Light gets reflected at the walls of the pure glass, and hence travels through hundreds of kilometers.
  • With dimensions of one tenth of a human hair, these cables are much thinner than their copper counterparts.
  • Since information is carried in the form of light signals, there are no chances of mixing of information in two fibers of the same cable.
  • Low power transmitters can be used for the transmission of signals, since the losses are minimal.
  • Implementation and usage costs are much less, in comparison to their copper counterparts.
Billions of bits of information can be transferred per second using this technology.