Optical Fiber

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optical fibre characteristics

Transcript of Optical Fiber

Optical CommunicationVIII Sem, ECE

Submitted By:Dimple Jhanwar Lecturer(ECE Department)


INDEXS No.I. II III IV. Unit-IOPTICAL FIBERS 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 Introduction Overview of fiber communication Ray propogation Total internal Reflection Modes in Optical fiber Transmission Characteristics of Optical Fiber Cables Propagation of Light along the fiber Ray Theory Types of Optical Fibers : 1.9.1 Step index fibers : 1.9.2 Graded index fibers Attenuation in Optical Fibers 1.10..1 Linear scattering losses 1.10.2 Non linear scattering losses 1.10.3 Material Absorption losses . Bending Loss 1.11.1 Microbend losses 1.11.2 Macrobend losses

Name of ContentResume Objective Syllabus Lecture Plan

Page No.5 8 9 10



Dispersion 1.12.1 Intramodal Dispersion 1.12.2 Intermodal Dispersion UNIT-II OPTICAL FIBER SOURCES & CONNECTION 2.1 2.2 Introduction Light Emitting Diode Structure 2.2.1 2.2.2

Dome LED Planar LED Basic Layer by Layer StructureBasic Layer by Layer Structure

2.2.5 2.2.6

Homo- and Hetro-Junction Edge Emitter 2

2.2.7 2.3 2.4 2.5 2.6

Edge Emitter

Characteristics of LED Quantum efficiency Fiber Alignment Technique Fiber Optical Splicing 2.6.1 Fusion Splicing 2.6.2 Mechanical Splicing 2.7 Optical fiber connector UNIT-III OPTICAL DETECTORS 3.1 Introduction 3.2 Optical Detector Properties 3.3 Responsivity 3.4 Quantum efficiency 3.5 PIN Photo Diodes 3.5.1 Response Time 3.6 Avalanche Photo Diodes 3.7 Receiver Noise 3.7.1 Thermal Noise 3.7.2 Shot Noise 3.8 Photo Diode Materials UNIT-IV OPTICAL MEASUREMENT 4.1 4.2 4.3 4.4 4.5 Measurement of Attenuation 4.1.1 Cut back Method Measurement of Cut-off wavelength Measurement of Dispersion Measurement of Diameter Measurement of Numerical Aperture

UNIT-V LASER 5.1 5.2 Principles of Laser Rate Equations and Population Inversion 5.2.1 Two- Level system 5.2.2 Three Level System 5.2.3 Four Level System


Optical feedback Lasing threshold Q-switching: 5.2.4 Principple 5.2.5 Active Switching 5.2.6 Passive Switching 5.2.7 Applications 5.3 Mode Locking 5.3.1 Laser active Mode Locking 5.3.2 Mode Locking Theory 5.3.3 Mode Locking Methods 5.4 Applications of LASER 5.4.1 Holography 5.4.2 Distance Measurement 5.4.3 Velocity Measurement V. VI. VII. VIII X XI XIIXIV XV XVI

Assignment-I Assignment-II Assignment-III Assignment-IV Class-Test-I Class-Test-II Class-Test-III Class-Test-V Tutorial-I Tutorial-II

XVII Tutorial-III XVIII Tutorial-IV XIX Tutorial-V XX I Mid Term Paper XXI II Mid Term Paper XXII Last Year Paper XXIII Evaluation sheet





Course Objective1) This subject deals with the practical aspects of optical fiber communication by introducing optical fiber 2) This course aims to initiate an expose the newcomers to exciting area of optical communication. Technical concepts which are at the core of design, implementation and research will be discussed during this course in order that is conductive to understanding general concepts as well as latest development. 3)Basic optical networks and WDM will be studied. Students will do design calculation for a pointto-point optical fiber link and star networks. 4)To give the student understanding of working principle of optical fiber sourses(LEDs and LASERs) detectors(PIN, Avalance photodiodes) coupler,fiber connectors


SYLLABUSUNIT 1 : OPTICAL FIBERS- Introduction, Ray theory, Optical fibers: multimode, single mode, step index,graded index, plastic & glass fibers.Transmission Characteristics of Optical Fibres -Introduction, Attenuation, Material absorption loss, Fibrebend loss, Dispersion (intermodal & intramodal) UNIT 2: OPTICAL FIBER SOURCES & CONNECTION - Light Emitting Diode - Structure, Material, Characteristics, Power & Efficiency.Fiber Alignment, Fiber splices, Fiber connectors, Expanded beam connectors, UNIT 3 : OPTICAL DETECTORS - Optical detection principles, quantum efficiency, responsivity, PIN photo diode, Avalanche photo diodes, Noise in Detectors, Photo Diode Materials. UNIT 4 : OPTICAL FIBER MEASUREMENTS - Measurements of Fiber Attenuation, Dispersion, Refractive Index Profile, Cut off Wave Length, Numerical Aperture & Diometer. UNIT 5 : LASER - Emission and absorption of radiation, Einstein relation, Absorption of radiation, Population inversion, Optical feed back, Threshold condition. Population inversion and threshold working of three level & four level laser. Basic idea of solid state, semiconductors, gas & liquid laser. Basic concept of Q-switching & mode locking. Laser applications for measurement of distance, Velocity, Holography.



LECTURE PLANName of Faculty: Dimple Jhanwar Subject: Optical CommunicationS. No. Unit No. Date Name of Topic Proposed Lectures Required

Branch: ECEActual Lecture Taken Extra Activities % of Syllabus Covered By the Unit Reference Books

Sem.: VIIIRemarks


1. 2.




5. 6.

7. 8. 9.

Introduction, Ray theory Optical fibers: multimode, single mode, step index, graded index, plastic & glass fibers. Transmission Characteristics of Optical Fibres Introduction, Attenuation Material absorption loss, Fibre bend loss, Dispersion (intermodal & intramodal) Class Test-I Light Emitting Diode - Structure, Material, Characteristics, Power & Efficiency. Fiber Alignment, Fiber splices Fiber connectors, Expanded beam connectors Class Test-II

2 1 Numerical Problem 1. Jhon M Senior 2. Gred Kaser 1 Assignmet -I Easy Theoretical & Analytical



12 1. Jhon M Senior

20%2 2 Numerical Problem Assignment - II

2. Navneet Gupta

Easy Theoretical & Analytical




LECTURE PLANName of Faculty: Dimple Jhanwar Subject: Optical CommunicationIII. OPTICAL DETECTORS 10. Optical detection principles, quantum efficiency, responsivity PIN photo diode, Avalanche photo diodes Noise in Detectors, Photo Diode Materials Mid Term I Measurements of Fiber Attenuation,Dispersi on, Refractive Index Profile ,Cut off Wave Length Numerical Aperture & Diometer Class test III 1 1. Jhon M Senior 15% 2 1 AssignmentIII 2. Navneet Gupta Moderate Theoretical & Analytical

Branch: ECE

Sem.: VIII

11. 12. 13. 14.


2 15% 2 2 1 Numerical Problem AssignmentIV

1. Jhon M Senior 2. Gred Kaser

15. 16. 17.

Moderate Theoretical & Analytical


Emission and absorption of radiation, Einstein

2 1. Jhon M Hard




20. 21.


relation Population inversion, Optical feed back, Threshold condition. Threshold Working of three level & four level laser Basic idea of solid state, semiconductors, gas & liquid laser Basic concept of Qswitching & mode locking.

Senior 1 25% 2 2 2. Gred Kaser 3. Navneet Gupta

Theoretical & Analytical


LECTURE PLANName of Faculty: Dimple Jhanwar Subject: Optical Communication23. Laser applications for measurement of distance, Velocity, Holography Mid Term II Total Lecture 2

Branch: ECENumerical Problem

Sem.: VIII

24. 25.


Proposed Lecture: 36

Actual Lecture Taken:

Signature of Faculty



IntroductionAn optical fiber (or fibre) is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.Light is kept in the core of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core diameter, and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 550 metres (1,800 ft).Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced


together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

GENERAL OVERVIEW OF OPTICAL FIBER COMMUNICATION SYSTEM :Like all other communication system, the primary objective of optical fiber communication system also is to transfer the signal containing information (voice, data, video) from the source to the destination. The source provides information in the form of electrical signal to the transmitter. The electrical stage of the transmitter drives an optical source to produce modulated light wave carrier. Semiconductor LASERs or LEDs are usually used as optical source here. The information carrying light wave then pass