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Introduction to Optical Fibers.
 Used to carry signals in the form of light over distances up to 50 km.
Fibers of glass
 Usually 120 micrometers in diameter
 No repeaters needed.
 Core – thin glass center of the fiber where light travels.
 Cladding – outer optical material surrounding the core
 Buffer Coating – plastic coating that protects the fiber.
Advantages of Optical Fibre
 Thinner
 Less Expensive
 Higher Carrying Capacity
 Less Signal Degradation& Digital Signals
 Light Signals
 Non-Flammable
 Light Weight
Type of Fibers
Optical fibers come in two types:
• Single-mode fibers – used to transmit one signal per fiber (used in telephone and cable TV). They have small cores(9 microns in diameter) and transmit infra-red light from laser.
• Multi-mode fibers – used to transmit many signals per fiber (used in computer networks). They have larger cores(62.5 microns in diameter) and transmit infra-red light from LED.
How Does Optical Fibre Transmit Light??
 Total Internal Reflection.
 When light travelling in a dense medium hits a boundary at a steep angle (larger than the "critical angle" for the boundary), the light will be completely reflected.
How are Optical Fibre’s made??
 Three Steps are Involved
-Making a Preform Glass Cylinder
-Drawing the Fibre’s from the preform
-Testing the Fibre
Testing of Optical Fiber
 TENSILE STRENGTH TEST
 Abrasion Test
 CRUNCH TEST (COMPRESSION TEST)
 Impact test
 REPEATED BENDING TEST
 TORSION TEST
 WATER PENETRATION TEST
Areas of Application
 Telecommunications
 Local Area Networks
 Cable TV
 CCTV
 Optical Fiber Sensors