Optical Fibers - Khulna University...(1) Gerd Keiser, Optical Fiber Communications, 2nd Edition...

Opto-electronic Devices and Optical

Communication

Optical Fibers:

Structures, Waveguiding, and Fabrication

Lecture 2 Presented By~

Dr. Md. Shamim Ahsan

Professor

ECE Discipline, Khulna University

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Outline

Wave Propagation Analysis

Fiber Geometry

Waveguide Equations & Boundary Conditions

Modal Equation & Modes in Step-index Fiber

V Parameter and Number of Modes

Power Flow in Step-index Fiber

Propagation Modes in Step-index and Graded-index Fibers

Optical Fiber Basics

Polarization

Nature of Light

Fiber & Cable Structure, and Fiber Fabrication

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The Nature of Light

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The Nature of Light

Figure: Representation of spherical and plane wave fronts and their associated rays.

ure

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The Nature of Light

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Optical Waveguide Concept

Figure: Physical model showing the ray

propagation and the corresponding

transverse electric (TE) field patterns of

three lower order models (m = 1, 2, 3) in

the planar dielectric guide.

(c) m = 3

(d)

E

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Skew Rays

The ray that is transmitted through the optical fiber without

passing through the fiber axis is called skew ray.

Skew rays follows the helical path through the optical fiber

as shown in the following figure.

Figure: The helical path taken by a skew ray

in an optical fiber.(a) skew ray path down the

fiber; (b) cross-sectional view of the fiber.

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Wave Propagation For Bulk Material

Similarly, by taking the curl of we obtain:

22

0 0 2r r

EH

t

Wave Propagation Equation

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For the inside region, the

solution of the guided

modes must remain finite

as r 0, whereas on the

outside the solutions must

decay to zero as r .

when, r

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Solution of Some Problems

1

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Solution of Some Problems

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Solution of Problem Regarding V Parameter and # of Modes

(2)

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Solution of Problem Regarding V Parameter and # of Modes

(3)

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Solution of Problem Regarding V Parameter and # of Modes

(4)

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Solution of Problem Regarding Cutoff Wavelength

(5)

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Power Flow in Step Index Fiber

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Solution of Problem Regarding Power Flow in Step Index Fiber

(6)

ure

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Graded Index Fibers

Figure: Possible fiber refractive index profiles for different

values of .

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Solution of Problem Regarding Graded Index Fiber

(7)

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Solution of Problem Regarding # of Modes in Graded Index Fiber

(8)

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Video: Fiber Fabrication

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Generator

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References: (1) Gerd Keiser, Optical Fiber Communications, 2nd Edition (1991), Chapter 2.

(2) Dennis Roddy and John Coolen, Electronic Communications, Fourth Edition (2000),

Chapter 20.

(3) John M. Senior, Optical Fiber Communications, 3rd Edition (2009), Chapter 2.

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