fiber optic technology
DESCRIPTION
Optical Fiber TechnologyTRANSCRIPT
Technical Seminar
Yaswanth
G12761A041
2
Fiber Optic Technology
Contents:Introduction HistoryConstruction Principle WorkingClassificationsApplicationAdvantagesDisadvantages
Introduction:
We hear about fiber-optic cables whenever people talk about the telephone system, the cable TV system or the Internet.
We are increasing ability to transmit more information, more quickly and over longer distances.
An optical fiber (or fiber) is a glass or plastic fiber that carries light along its length . Fiber Optics is overlap of applied science and engineering.
What are Fiber Optics?
Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair.
They are arranged in bundles called optical cables and used to transmit light signals over long distances.
History:1880: Alexander G. Bell
transmit sound waves over beam of light
1930: TV image through uncoated fiber cables Few years later image through a single glass fiber
1951: Flexible fiberscope: Medical applications
1956: The term “fiber optics” used for the first time
1960: Laser invented
1967: New Communications medium: cladded fiber
1970s & 1980s : High quality sources and detectors
1990: Deployment of SONET systems
Construction:
Optical Fiber consists of 3 regions
1.Core – thin glass center of the fiber where light travels.
2.Cladding – outer optical material surrounding the core
3.Buffer Coating – plastic coating that protects the fiber.
Principle:
The principle behind the transmission of the light waves in an Optical Fiber is “Total Internal Reflection”
The angle of refraction at the interface between two media is governed by Snell’s law:
2211 sinsin θnθn
Angle of incidence < critical angle
Angle of incidence = critical angle Angle of incidence > critical angle
Refraction, Critical angle , Total internal reflection
Working:When light traveling 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. This phenomenon is called total internal reflection.
Total internal reflection occurs when light enters fromhigher refractive index to lower refractive index material, i. e from glass to air total internal reflection is possible but it is not possible in air to glass.
In Figure we see that where the angle 01 is greater than the critical value the ray is refracted into the cladding and will ultimately be lost outside the fiber. This is loss.
In Figure we see that for rays where angle01 is less than a Critical value then the ray will propagate along the fiber and will be “bound” within the fiber.
n2 cladding
n2 claddingn1 core
AcceptanceCone
-If the angle too large light will be lost in cladding- If the angle is small enough the light reflects into core and propagates
qC
Acceptance Cone
n2 cladding
n2 claddingn1 core
AcceptanceCone
Acceptance angle, qc, is the maximum angle in whichexternal light rays may strike the air/Fiber interfaceand still propagate down the Fiber with <10 dB loss.Note: n1 belongs to core and n2 refers to cladding)
22
21
1sin nnC
qC
Acceptance Angle
Transmission of signal:The light in a fiber-optic
cable travels through the core by constantly bouncing from the cladding and the principle called total internal reflection.
Hence the cladding does not absorb any light from the core.
Types of Optical Fibers:
Material used
Mode of transmission
Refractive index profile
GlassFiber
PlasticFiber
Singlemode
Multimode
StepIndex
GradedIndex
Classification based on “Material Used”
Classification based on “Modes of Transmission”
Classification based on “Refractive Index profile”
Application: Fiber Optic Communication
Process of Fiber Optic Communication
Advantages:
Less signal degradationLess ExpensiveLite weightDigital SignalsNon-FlammableHigher carrying CapacityThinnerLow PowerUse Light Signals
Disadvantages
Higher initial cost in installationInterfacing costStrength
Lower tensile strengthRemote electric powerMore expensive to repair/maintain
Tools: Specialized and sophisticated