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IN CAMPUS COMMUNICATION SYSTEM USING OPTICAL PRINCIPLES AND

TECHNIQUES (RECEIVER)

AZIDZIN BIN MOHD.RIDZAUDZIN

This report is submitted in partial fulfillment of the requirements for the award of

Bachelor of Electronic Engineering (Telecommunication Electronics) With Honours

Faculty of Electronic and Computer Engineering

Universiti Teknikal Malaysia Melaka

April 2009

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UNIVERSTI TEKNIKAL MALAYSIA MELAKA

FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER

BORANG PENGESAHAN STATUS LAPORAN

PROJEK SARJANA MUDA II

Tajuk Projek : In campus communication system using optical principles and

techniques (receiver)

Sesi Pengajian : 2008/2009

Saya AZIDZIN BIN MOHD.RIDZAUDZIN (HURUF BESAR) mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syarat-

syarat kegunaan seperti berikut:

1. Laporan adalah hakmilik Universiti Teknikal Malaysia Melaka.

2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.

3. Perpustakaan dibenarkan membuat salinan laporan ini sebagai bahan pertukaran antara institusi

pengajian tinggi.

4. Sila tandakan ( √ ) :

SULIT*

(Mengandungi maklumat yang berdarjah keselamatan atau

kepentingan Malaysia seperti yang termaktub di dalam AKTA

RAHSIA RASMI 1972)

TERHAD*

(Mengandungi maklumat terhad yang telah ditentukan oleh

organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHAD

Disahkan oleh:

__________________________ ___________________________________

(TANDATANGAN PENULIS) (COP DAN TANDATANGAN PENYELIA)

Alamat Tetap: G7-01-06 Kuarters IPD Gombak,

Bukit Idaman Selayang

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“I hereby declare that this report is the result of my own work except for quotes as cited

in the references.”

Signature :

Author : AZIDZIN BIN MOHD.RIDZAUDZIN

Date :

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“I hereby declare that I have read this report and in my opinion this report is sufficient in

terms of the scope and quality for the award of Bachelor of Electronic Engineering

(Telecommunication Electronics) With Honours.”

Signature :

Supervisor’s Name : MR.TAN KIM SEE

Date :

v

DEDICATION

This thesis is dedicated to my family and friends who have shared countless hours

helping me in the process completing this report.

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ACKNOWLEDGEMENT

It is difficult to write a technical report without the contributions from others. I

have received an abundance of such assistance, for which I am deeply grateful. I want to

thank Mr. Tan Kim See, my project supervisor who was always there for me when I

needed his advice. Without his guidance, it would have been very much harder for me to

complete my final year project. I also want to acknowledge all the other people who had

played a part in helping me to finish this project as fulfillment for my bachelor degree. I

am particularly indebted to my friends and colleagues who have put up with me for my

incessant argumentative discussions many a time I called upon them. The findings

expressed in this report were retrieved from the various inputs and combined efforts of

many kind people whom are impossible for me to list them down one by one.

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ABSTRACT

Free space optics (FSO) is an emerging technology that has found application in

several areas of the short-and long-haul communications space. From inter-satellite links

to inter-building links, it has been tried and tested. As with any technology, FSO has

worked much better in some applications than in others. Free space optical systems do

face a lot of problems especially from atmospheric disturbances as the signal travels in

free space. Rain and snow attenuate the signal and hence decrease the range of reliable

communication. Fog being composed of water droplets, can completely hinder the

passage of light through a combination of absorption, scattering and reflection. Physical

obstructions such as flying birds cause temporary interruption in the received signal.

Nonetheless, free space optical communication systems is a viable alternative, given its

optical base, bandwidth scalability, speed of deployment, re-deployment and portability,

and cost-effectiveness.

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ABSTRAK

Optik ruang bebas (FSO) adalah satu teknologi mula membangun yang telah

diaplikasikan di beberapa kawasan untuk ruang komunikasi jauh dan singkat. Daripada

sebagai penghubung antara satelit kepada penghubung antara bangunan, ia telah

diaplikasi dan diuji. Dibandingkan dengan teknologi sedia ada, FSO terbukti lebih baik

dalam beberapa faktor. Sistem optikal ruang bebas ini bagaimanapun tetap mempunyai

kekurangan kerana isyarat dipancarkan ke ruang bebas banyak menghadapi gangguan

terutmanya dari atmosfera itu sendiri. Hujan dan salji menggangu isyarat dan oleh itu

mengurangkan julat komunikasi untuk bekerja. Kabus yang terhasil juga boleh

menghalang isyarat yang dipancar dari diterima. Halangan objek fizikal seperti burung

juga mendatangkan masalah kerana boleh menghalang isyarat untuk satu jangkamasa

yang singkat. Namun banyak kelebihan sistem ini seperti menjimatkan kos, mengambil

masa yang singkat untuk dipasang, penghantaran yang laju menjadikan ia satu pilihan.

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LIST OF CONTENT

CHAPTER TITLE PAGE

PROJECT TITLE i

DECLARATION iii

PENGAKUAN iv

DEDICATION v

ACKNOWLEDGEMENT vi

ABSTRACT vii

ABSTRAK viii

LIST OF CONTENT ix

LIST OF TABLE xiv

LIST OF FIGURE xv

LIST OF ABBREVIATION xvii

1 INTRODUCTION

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1.1 Project Introduction 1

1.2 Project Objective 2

1.3 Scope 3

1.4 Problem Statement 4

2 BACKGROUND STUDY 6

2.1 Introduction 6

2.1.1 History of Free Space Optic (FSO) 7

2.1.2 How Free Space Optics (FSO) Works 8

2.1.3 FSO specifications 8

2.2 FSO, Fiber Optic and RF Wireless A Comparison 10

2.3 FSO Network Architectures and Commercial

Implementations 12

2.4 Applications 13

2.5 Free Space optics (FSO) technology 14

2.5.1 How a Laser Works 14

2.6 FSO characteristics 17

2.6.1 FSO Transmission Formula 20

2.7 Free Space Optics (FSO) Advantages 21

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2.7.1 Free Space Optics (FSO) Security 22

2.8 Challenges and Reliability Issues in FSO Systems 23

2.8.1 Laser Safety 28

2.8.1.1 Laser Classification Overview 28

2.8.1.2 Potential Transmission Hazards 29

2.9 Causes of Transmission Impairments 31

2.9.1 Overview 31

2.9.2 Path Geometry 32

2.9.3 Scintillation 33

2.9.4 Rain Attenuation 33

3 METHODOLOGY 34

3.1 Introduction 34

3.2 Project Planning 37

3.3 Literature Review 38

4 RESULT AND DISCUSSIONS 39

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4.1 Transmitter 35

4.1.1 Laser 39

4.1.2 Laser Source 40

4.1.2.1 Diode Lasers 41

4.1.3 Diode Laser Modules and Laser Pointers 45

4.1.3.1 Difference Between Diode Laser Modules

And Laser Pointers 46

4.1.3.2 Inside a Laser Pointer 47

4.2 Receiver 49

4.3 Circuit 50

4.3.1 RS-232 Standards 51

4.4 Construction 52

4.5 Testing 54

4.6 Serial Communication-Data Transfer Concept 57

4.7 Flow Control 59

4.7.1 Serial Port Pinouts and Pin Functions (D25 and

D9 Connectors) 60

4.7.2 The Null Modem Configuration 61

4.7.3 COM Port Addresses and IRQ’s 62

4.7.4 UART Registers and Programming 64

4.8 Line Control Register (LCR) 66

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5 CONCLUSION AND RECOMMENDATIONS 77

5.1 Recommendations 77

5.2 Conclusion 78

REFERENCESS 80

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LIST OF TABLE

NO TITLE PAGE

2.1 FSO Comparison 10

2.2 IEC 60825-1 Laser Classification System 29

3.1 Gantt Chart PSM 1 37

3.2 Gantt Chart PSM 2 38

4.1 Electrical Characteristics of BPW-34 49

4.2 D Type 9 Pin and D Type 25 Pin Connectors 60

4.3 Standard Port Addresses 62

4.4 COM Port Addresses In the BIOS Data Area 63

4.5 Table of Registers 64

4.6 Bit #0 and Bit #1 of IER 66

4.7 Line Control Register 68

4.8 Line Status Register 69

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LIST OF FIGURE

NO TITLE PAGE

2.1 Typical Network of Laser Transceivers 10

2.2 Laser Concept 15

2.3 Block diagram FSO communication system 18

2.4 Block Diagram of Fiber Optic Transmitter and Receiver Assemblies 19

2.5 Single-beam FSO Transceiver 19

2.6 Transmission Spectra for Light Traveling through clear air 26

2.7 Transmission Spectra for Light Traveling through moderate fog 26

2.8 Penetration of Light Into Eyeball 31

2.9 Calculation of Beam-width 32

3.1 Project Flowchart 36

4.1 A Diode Laser Module 45

4.2 The Schematic of The Transceiver 50

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4.3 DB-9 (Female) Wiring 53

4.4 PCB Patterns For The Transceiver 54

4.5 The Assembled Transceiver 54

4.6 Null Modem Wiring Diagram 61

xvii

LIST OF ABBREVIATION

FSO - Free Space Optic

WDM - Wavelength Division Multiplexing

RF - Radio Frequency

LD - Laser Diode

LED - Light Emitting Diode

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CHAPTER 1

INTRODUCTION

1.1 Project introduction

The increasing demand for higher bandwidth in communication networks has led

to the rise in the use of optical communication systems for transmitting voice, video and

data. Optical communication can be either guided as in fiber optic wave guides or

unguided as in free space optical systems. Fiber optic systems are the most reliable

means of providing optical communications. But the digging, delays and associated

costs to lay fiber often make it economically prohibitive. Moreover, once fiber is

deployed, it becomes a "sunk" cost and cannot be re-deployed if a customer relocates or

switches to a competing service provider, making it extremely difficult to recover the

investment in a reasonable timeframe. Free space optical communication system on the

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other hand, is a line of sight technology that uses air/free space as the medium of

transmission and is relatively simple. Unlike radio frequencies, the technology requires

no spectrum licensing. It is easily upgradeable, and its open interfaces support

equipment from a variety of vendors. Further, it enables optical transmission at speeds

up to 2.5 Gbps and in the future up to 10 Gbps using WDM. This is not possible using

any fixed wireless/RF technology existing today.

1.2 Project objectives

To design a communication system that sent data in light beam through

atmosphere.

To offer system that overcome the problems or disadvantage in recent wireless

communication such as microwave.

Provides system with no federal communication commission or frequency

allocation requirement.

Provides system that useful where the physical connection of the transmission

and receiver location is difficult.

Provides system that portable and quickly deployable (ideal for temporary

installation).

Provides an economic system because no cabling cost, low power consumption

and save space.

Provides system that is secured because of laser’s narrow beam detection and

interception are difficult.

Design a moderate speed FSO data link with transfer rates up to 100Kbps.

Operating distances 100 to 300 meter

Much Cheaper as compared to the commercially available equipment.

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Design using readily available, cheap and indigenous components instead of

expensive, specialized components.

Excellent up-time and good reliability.

Very less setup times.

1.3 Scope

Due to financial constraints we have implemented this technology at an

elementary level. Availability of more funds will help us implement the circuit

for higher speeds of the order Mbps to Gbps and also widen its communication

range from meters to kilometers.

The system implemented is basically a one to one bi-directional communication

system. It can be modified into one to many multichannel systems.

One of the limitations of the above system is its inability to operate with

efficiency in presence of fog, heavy rain or snow.

As the range of communication of the system increases certain de-coherence

limiting measures are needed also, the swaying of buildings certain adjustments

need to be done.

When line of sight communication is not possible then the system can be

implemented by the use of reflection and deviation mirrors.

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1.4 Problem statement

Fiber optics provides an excellent solution for high bandwidth, low error

requirements and can serve as the backbone for the internet infrastructure. Most of the

recent trenching to lay fiber has been to improve the metro core (backbone). Carriers

have spent billions of dollars to increase network capacity in the core, of their networks,

but have provided less lavishly at the network edges. This imbalance has resulted in the

"last mile bottleneck." Service providers are faced with the need to turn up services

quickly and cost-effectively at a time when capital expenditures are constrained.

From a technology standpoint, there are several options to address this "last mile

connectivity bottleneck" but most don't make economic sense.

Fiber Optic Cable: Without a doubt, fiber is the most reliable means of providing

optical communications. But the digging, delays and associated costs to lay fiber

often make it economically prohibitive. Moreover, once fiber is deployed, it

becomes a "sunk" cost and cannot be re-deployed if a customer relocates or

switches to a competing service provider, making it extremely difficult to

recover the investment in a reasonable timeframe.

Radio frequency (RF) Wireless: RF is a mature technology that offers longer

ranges distances than FSO, but RF-based networks require immense capital

investments to acquire spectrum license. Yet, RF technologies cannot scale to

optical capacities of several gigabits. The current RF bandwidth ceiling is 622

megabits. When compared to FSO, RF does not make economic sense for service

providers looking to extend optical networks.

Wire and Copper-based technologies: Although copper infrastructure is available

almost everywhere and the percentage of buildings connected to copper is much

higher than fiber, it is still not a viable alternative for solving the connectivity

bottleneck. The biggest hurdle is bandwidth scalability. Copper technologies may

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ease some short-term pain, but the bandwidth limitations of 2 megabits to 3

megabits make them a marginal solution.

Providing last mile connectivity is extremely difficult and expensive. In metropolitan

areas, an estimated 95 percent of buildings are within 1.5 km of fiber-optic

infrastructure. But at present, they are unable to access it. Connecting them with fiber

require high cost, with 85 percent of the total figure tied to trenching and installation.

Street trenching and digging are not only expensive, they cause traffic jams (which

increase air pollution), displace trees, and sometimes destroy historical areas.

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CHAPTER 2

BACKGROUND STUDY

2.1 Introduction

Free Space Optics, the industry term for “Cable-free Optical Communication

Systems”, also called Free Space Photonics (FSP) or Optical Wireless refers to the

transmission of modulated visible or infrared (IR) beams through the atmosphere to

obtain optical communications. In other word, it is a line of sight optical technology in

which video and data are sent through the air (free space) on low-power light beams at

speeds of megabytes or even gigabytes per second. A free-space optical link consists of

2 optical transceivers accurately aligned to each other with a clear line-of-sight.

Typically, the optical transceivers are mounted on building rooftops or behind windows.

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These transceivers consist of a laser transmitter and a detector to provide full duplex

capability. It works over distances of several hundred meters to a few kilometers.

Like fiber, Free Space Optics (FSO) uses lasers to transmit data, but instead of

enclosing the data stream in a glass fiber, it is transmitted through the air. Free Space

Optics (FSO) works on the same basic principle as Infrared television remote controls,

wireless keyboards or wireless Palm devices.

2.1.1 History of Free Space Optics (FSO)

The engineering maturity of Free Space Optics (FSO) is often underestimated,

due to a misunderstanding of how long Free Space Optics (FSO) systems have been

under development. Historically, Free Space Optics (FSO) or optical wireless

communications was first demonstrated by Alexander Graham Bell in the late nineteenth

century (prior to his demonstration of the telephone!). Bell’s Free Space Optics (FSO)

experiment converted voice sounds into telephone signals and transmitted them between

receivers through free air space along a beam of light for a distance of some 600 feet.

Calling his experimental device the “photophone,” Bell considered this optical

technology and not the telephone, his preeminent invention because it did not require

wires for transmission.

Although Bell’s photophone never became a commercial reality, it demonstrated

the basic principle of optical communications. Essentially all of the engineering of

today’s Free Space Optics (FSO) or free space optical communications systems was

done over the past 40 years or so, mostly for defense applications. By addressing the

principal engineering challenges of Free Space Optics (FSO), this aerospace/defense

activity established a strong foundation upon which today’s commercial laser-based Free

Space Optics (FSO) systems are based.