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What are Fiber Optics?

Physics | 8-11 yrs | Animation, Video

You may have heard about fiber optics but the name itself does not say much about this fascinating technology. The term is used to refer to the technology where the energy of light is harnessed to transmit data, much like you would use an electric impulse in a copper wire. Since light travels at the speed of 300,000 kms per second, fiber optic technology has greatly reduced the speed at which information can be sent and received via fiber optic cables.


An optical fiber is a semi-flexible, transparent, and extremely thin strand of pure glass that has the diameter of a human hair. Thousands of these strands are arranged in bundles to make a thicker cable. Since glass is optically transparent, we are able to send information-laden rays of light over long distances.

A fiber optic cable is made up of five parts:

Strands of glass that are bundled together to make one single channel of light called the core. The diameter of the core dictates how much information can be sent and received at one time.

A protective sheath or coating around any structure or material is known as the cladding. In fiber optic cables the silica cladding increases the total internal reflection of the core. Therefore, a light pulse can pass through the entire length of the fiber, with little data loss.

A layer of plastic surrounds the core and cladding to reinforce the fiber core. The coating provides extra protection and prevents the cable from bending too much.

The strengthening fibers around the coating give added support to the coating, especially when it comes to stretching tension.

Finally, all this is covered in the cable jacket, like any other cable or wire.

The only part of a fiber optic cable that carries data is the tiny core in the center, but it has layer upon layer of protection, because glass is extremely brittle and in order for it to function at its best, there can be no breaks in the fiber at all. Add to that, the high cost of producing them and you will know why every precaution must be taken to prevent damage.

Total Internal Reflection

If you shine a torch down a long hallway, you will see that light travels in straight lines to the end of the hallway. Now if there was a bend in the hallway, you could put a mirror at the bend and light would be reflected to change direction and continue down the bend. But what if this hallway had many twists and turns and it was up to you to shine light from where you are standing to the end of the hallway? You could set up an elaborate system of mirrors so that light wiould keep reflecting until it reached the end.

A fiber optic cable is able to do this, not with the help of an elaborate set-up of mirrors, but because of the phenomenon of total internal reflection. Think of the cladding as the many mirrors along the walls of the hallway of fiber continuously reflecting light. In this way, the light is contained within the core and continues along its path inside the cable, without degrading.

How does Fiber Optics Work?

  • The first step in relaying information over a fiber optic cable is the transmitter. The transmitter is responsible for converting an electrical digital signal into a light signal. It imprints the information onto the light, as changes in intensity and pulse rate.
  • If the ray has to travel a long distance, it will have to pass through an optical regenerator. This nifty device re-boosts the strength of the ray by copying the message and sending a duplicate onward to its destination. A message may have to pass through multiple optical regenerators along its path.
  • Finally the ray of light, with the message imprinted on it, arrives at the optical receiver. Here, it is decoded back into a binary digital format.


  • The most common use of fiber optics is in the field of communication. Massive amounts of data is sent and received over networks of fiber optic cables for various industries such as cable television, phones, and the internet.
  • Since these cables are able to bend, doctors use them during surgery to shine light inside parts of the body, which are hard to reach.
  • Fiber optic scopes are also used by engineers and mechanics to throw light onto parts of machines with many twists and bends where light cannot easily travel.
  • It is also used for imaging in hard to reach areas or places with extreme conditions such as deep underground, under the sea or inside the body.

Fiber optic cables have transformed the communications industry. Before its invention, we relied on copper wires carrying electrical signals. Data would diminish while traveling over the ancestors of fiber optic cables and sometimes even get lost completely. These flexible, light-weight, non-flammable, low-power cables may be expensive but are definitely worth their weight in salt.

  • How does a binary signal differ from an analog signal?
  • Doctors use fiber optic scopes when they perform a particular type of surgery called a laproscopy. Can you find out what this technique of surgery is and how a fiber optic scope is beneficial?
  • Find out whether total internal reflection is possible with materials other than glass.

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