1. OPTICAL FIBER AND ITS APPLICATIONS
Presented by
Dr.M.LAWRENCE
ASSISTANT PROFESSOR
DEPARTMENT OF PHYSICS
ST.JOSEPH’S COLLEGE(AUTONOMOUS)
TIRUCHIRAPPALLI-2

2. Optical Fiber and its Applications
CONTENTS
Optical fiber
Guiding mechanism
Total internal reflection
Numerical aperture
Types of optical fibers
Refractive index mode
Applications

3. Optical fiber
An optical fiber is a flexible, transparent fiber made by drawing glass(silica) or plastic to a diameter slightly thicker that of a human hair.

4. The information carried by the light wave should need a guiding medium through which it can be transmitted safely. The guiding medium is called as optical fiber.

5. Optical fiber cable
A bundle of optical fibers consists of thousands of individual fiber wires as thin as human hair, measuring 0.004mm in diameter is known as optical fiber cable.

6. Guiding mechanism in optical fiber
The light which enters from one end of the fiber strikes on the interface of core and cladding at greater angle of incidence.
The light beam under goes total internal reflection and it passes along the length of the fiber.

7. Total internal reflection in optical fiber
The optical fiber obeys the laws of reflection and refraction of light waves.

8. A light ay travelling in a medium of refractive index n1 incident on another medium of lower refractive index n2 at the boundary.
This light ray is reflected back in to first medium or refracted through second medium.
The reflection or refraction of the light at the interface depends on the difference in the speed of light in two materials having different refractive indices and angle of incidence.

9. Numerical aperture(NA)
Used to describe the light gathering or light collecting ability of an optical fiber
The numerical aperture(NA) of an optical system is a dimensionless number that characterizes the range over which the system can accept or emit

11. Types of optical fibers
Depending on the number of modes of propagation the optical fiber are classified in to two types
(i) single mode fiber
(ii) multimode fiber
Single mode fiber
If only one mode is transmitted through an optical fiber, then the optical fiber is known as single mode fiber.
its core diameter is small in the order of a few times the wavelength of light

12. It is designed to have small refractive index difference between the and cladding.
The single mode fiber must be used along with laser diodes
It can support only one mode of propagation

13. Multimode fiber
If more than one mode is transmitted through an optical fiber, then the optical fiber is known as multimode fiber.

14. The large core radii of multimode fiber makes it easier to launch light in to the fiber.
It can support a number of modes.

15. Refractive index profile
The refractive index of the core and cladding, the optical fibers are classified in to two types.
1.Step-index fiber
2.Graded-index fiber
Step-index fiber
In step index fiber, the variation is refractive indices of air, cladding and core vary step by step. Hence, this type of fiber is known as step index fiber.

16. Step index fiber is classified in to two types. They are
Step index -single mode fiber
step index-multi mode fiber
Step- index single mode fiber

17. Multimode multi mode fiber
A step index single mode fiber has a core diameter of 5 to 10mm and an external diameter of cladding of 50 to 125 mm.
Multimode multi mode fiber

18. Graded index multimode fiber
A step-index multimode has a core diameter of 50 to 200 mm and an external diameter of cladding 125 to 300 mm
It has a core material with uniform refractive index and cladding material of lesser refractive than that of the core
Graded index multimode fiber

19. A graded index multimode fiber has a core diameter of 50 to 200mm and an external diameter of cladding 100 to 250mm.
The refractive index of the core is maximum at the axis of the fiber and it gradually decreases towards the cladding.

20. Difference between single mode fiber and multi mode fiber
In single mode fiber, only one mode can propagate through the fiber.
It has smaller core dia and the difference between the refractive index of core and cladding is very small.
Fabrication is difficult and costly.
Multi mode fiber allows a large number of paths or modes for the light rays travelling through it.
It has larger core dia and refractive index difference is larger than the single mode fiber.
Fabrication is less difficult and not costly.

21. Applications Filters can be used under sea communication
Fibers are used in military applications such as aircrafts,ships,tanks etc
Fibers are used in public utility organization like railways, TV transmission etc
Fibers are used in LAN systems of offices, industrial, plants and colleges etc
Fibers are used in telecommunication such as voice telephones, video phones telegraph services, message services and data network.

22. Thank you