Fiber Optics and Types

Fiber Optics or Optical Fiber is a modern technology that transmits information/data as a light pulse along glass or plastic fiber. An Optical Fiber is a cylindrical fiber of glass that is hair-thin in size or any transparent dielectric medium. The fiber which is used for optical communication is waveguides made of transparent dielectrics.

In this article, we will discuss Optical Fiber/Fiber Optics in detail. We will also discuss Types of Fiber Optics based on different categories, advantages, and disadvantages of Fiber Optics as well.

Fiber optics refers to the technology and method of transmitting information as light pulses along a glass or plastic strand or fiber. Fiber optic cables are used for long-distance and high-performance data networking. They are capable of transmitting data over longer distances and at higher bandwidths (data rates) than electrical cables, making them a critical component in modern telecommunications, internet, and computer networking.

• Core: It is the central tube of very thin size made of optically transparent dielectric medium and carries the light transmitter to receiver and the core diameter may vary from about 5um to 100 um.
• Cladding: It is an outer optical material surrounding the core having a reflecting index lower than the core and cladding helps to keep the light within the core throughout the phenomena of total internal reflection.
• Buffer Coating: It is a plastic coating that protects the fiber made of silicon rubber. The typical diameter of the fiber after the coating is 250-300 um.

There are different types of fiber optics based on several categories as mentioned below:

Based on the Number of Modes

• Single-mode fiber: In single-mode fiber, only one type of ray of light can propagate through the fiber. This type of fiber has a small core diameter (5um) and high cladding diameter (70um) and the difference between the refractive index of core and cladding is very small. There is no dispersion i.e. no degradation of the signal during traveling through the fiber. The light is passed through it through a laser diode.
  
• Multi-mode fiber: Multimode fiber allows many modes for the light rays traveling through it. The core diameter is generally (40um) and that of cladding is (70um). The relative refractive index difference is also greater than single-mode fiber. There is signal degradation due to multimode dispersion. It is not suitable for long-distance communication due to the large dispersion and attenuation of the signal. There are two categories based on Multi-mode fiber i.e. Step Index Fiber and Graded Index Fiber. These are categories under the types of optical fiber based on the Refractive Index

Based on Refractive Index

• Step-index optical fiber: The refractive index of the core is constant. The refractive index of the cladding is also continuous. The rays of light propagate through it in the form of meridional rays which cross the fiber axis during every reflection at the core-cladding boundary.
  
• Graded index optical fiber: In this type of fiber, the core has a non-uniform refractive index that gradually decreases from the center towards the core-cladding interface. The cladding has a uniform refractive index. The light rays propagate through it in the form of skew rays or helical rays. it does not cross the fiber axis at any time.

Based on the Material Used

• Plastic Optical Fibres: For transmission of light, polymethylmethacrylate is used as core material
• Glass Fibres: These are extremely fine glass fibers, the core and cladding of the optical fiber is made of plastic.

Fiber Optics has the work of transmission of light particles, or photons. Fiber optics transmit data as light through thin sheets of glass or plastic. Each fiber consists of a core, where the light travels through it, and a surrounding cladding that reflects the light back into the core part. Data is converted into light using a laser or LED, and these light pulses travel through the core, bouncing off the cladding to stay contained in it.

At the receiving end, a photodetector converts the light back into the electrical signals. This technology allows for fast, high-capacity data transmission with minimal signal loss, immunity to electromagnetic interference, and therefore the security is enhanced. Fiber optics are generally used for high-speed internet, telecommunications, medical devices, and many more industrial applications.

• Fiber Optics can be used in Computer Broadcasting and Networking
• Fiber Optics are used on the Internet. They are also used in Television Cable.
• Fiber Optics are widely used in Military Activities. They are also used in Medical Purposes like for precise illumination.
• They can also be used in Underwater environments as they don’t require to be replaced frequently.

• Fiber Optics supports bandwidth with higher capacities.
• Electromagnetic Interference is very little with Fiber Optics.
• Fiber Optics are stronger and lighter than copper cables.
• Very little Maintenance is required in Optical Fiber.

• Fiber Optics is more costly than Copper Wire.
• Huge manual work is required to install new cables.
• Some optical fibers like glass fiber require more protection.
• Fiber Optics are more fragile i.e., can be easily broken, or signals can be lost easily.

Q1: Consider the following statements: [UGC NET Paper 2 CS 2019]

(a) Fiber optic cable is much lighter than copper cable
(b) Fiber optic cable is not affected by power surges or electromagnetic interference
(c) Optical transmission is inherently bidirectional.

Which of the statements is (are) correct?

1) Only a and b
2) Only a and c
3) Only b and c
4) a, b and c

Ans: Option1 (Only a and b)

Q2: The critical angle θc in an optical fiber is given by ________ Where n₁ is the refractive index of medium 1 and n₂ is the refractive index of medium 2. [ISRO Scientist EC 2011 Paper]
a) sin^-1 (n₂/n₁)
b) sin^-1 (n₁/n₂)
c) sin^-1 (n₁*n₂)
d) sin^-1 n₂

Ans: Option1 (sin^-1 (n₂/n₁))

What are the 4 common fiber optic connectors?

ST, SC, FC, MT-RJ, & LC connectors are 4 common fiber optic connectors

What signal is used by fiber optics?

Signals are encoded as pulses of light or laser 

What are the threats to fiber optics?

Tapping, bending and splicing attacks are threats to fiber optics