Fiber Optic Microbend Sensor.

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UNIVERSTI TEKNIKAL MALAYSIA MELAKA

FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER BORANG PENGESAHAN STATUS LAPORAN

PROJEK SARJANA MUDA II

Tajuk Projek : FIBER OPTIC MICROBEND SENSOR

Sesi

Pengajian : 2008/2009

Saya NIK NOZITA BINTI MOHD SAAD

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: RKT BATU MENGKEBANG 18000 KUALA KRAI KELANTAN

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FIBER OPTIC MICROBEND SENSOR

NIK NOZITA MOHD SAAD

This report was submitted in partial Fulfilment of requirement for the Bachelor Degree of Electronic Engineering (Telecommunication Electronics)

Faculty of electronic and Computer Engineering Universiti Teknikal Malaysia Melaka

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iii

DECLARATION

“I hereby declare that this report is result of my own effort except for works that have been cited clearly in the references.”

Signature : ……….

Name : NIK NOZITA MOHD SAAD Date : 30 APRIL 2009

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“I hereby declare that I have read this report and in my opinion this report is sufficient in terms of scope and quality for the award of Bachelor of Electronic and

Computer Engineering (Electronic Telecommunication) with Honours”

Signature : ……….

Supervisor’s Name : EN CHAIRULSYAH B. ABDUL WASLI

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ACKNOWLEDGEMENT

I would like to take this opportunity to express my deepest gratitude to my project supervisor; Mr. Chairulsyah b. Abdul Wasli, who has persistently and determinedly assisted me during the whole course of this project. It would have been very difficult to complete this project without the enthusiastic support, insight and advice given by him.

To all my peers, especially the occupants of faculty of electronic and computer engineering, thank you for providing the motivation necessary for me to do my best. I would like to express my gratitude to my friends for sharing our sentiments and their ideas. Not forgetting my parents, for without their love and support, I would not even be here, thank you for everything. Finally, I would like to thank for all the people around me who had involved directly or indirectly for throughout their advices, supports and guidance for my completion of this research project.

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ABSTRAK

Tujuan utama projek ini adalah untuk mencipta dan menghasilkan optic fiber

microbend sensor, untuk mengukur kuasa yang keluar, kehilangan kuasa dan analisis keputusan. Tajuk sebenar projek ini adalah fiber optic microbend sensor. Projek ini menghasilkan system pengesan yang mana termasuk punca cahaya, elemen pengesan dan pengesan cahaya. Dalam keadaan yang normal, sesetengah aras boleh dikira dan sekiranya pengesan mengesan kehadiran tekanan, paras arus akan berubah dan menunjukkan tekanan. Dalam system fiber, gelombang optic ditukarkan kepada arus elektrik dengan menggunakan pengesan cahaya. Jumlah kuasa yang dikesan oleh penerima bergantung kepada jumlah kuasa yang keluar daripada pengeluar dan dikeluarkan oleh fiber optik. Bila wayar dalam keadaan normal iaitu lurus, kuasa yang hilang sedikit berbanding dalam keaadan bengkok yang mengeluarkan banyak kuasa kerana ada cahaya yang terpantul menyebabkan kuasa pada penerima

berkurang. Perbezaan kuasa menunjukkan wayar fiber optik boleh diguna sebagai microbend sensor. Projek ini termasuk juga dengan pengiraan, simulasi, mereka dan menganalisa data.

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ABSTRACT

The main purpose of this project is to design and to build fiber optic microbend sensor, measure the output power, power loss and analyze the results. The title of this project is fiber optic microbend sensor. This project consists the transmitter and the receiver between the fiber optic. This project will develop a sensor system that used fiber optic cable, which is consisting of light source, sensor element and the light detector. In normal condition the certain level will measure and if the sensor senses some pressure it will change the level and indicate the level of pressure. In fiber system, the optic wave is converted into an electric current by a photodetector. The power detect at the receiver is depend on the power feed at the transmitter and the attenuation of the fiber optic. When the cable in a straight line condition, the attenuation will be minimum but if there is bend or indentation on the cable, there will be additional attenuation on the cable because some of ray light will be reflected so the power at receiver will be drop. This power differences will show that the fiber optic cable can be use as microbend sensor. This project contains calculation,

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TABLE OF CONTENT

CHAPTER TITLE PAGE

DECLARATION i

DEDICATION ii

ACKNOWLEDGEMENTS iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES vii

LIST OF FIGURES viii

LIST OF APPENDICES ix

LIST OF SYMBOLS x

I INTRODUCTION 1

1.1 OBJECTIVE 2

1.2 SCOPE OF WORKS 3

1.3 PROBLEMS STATEMENT 4

1.4 METHODOLOGY 4 1.5 THESIS OUTLINE 5

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II LITERATURE REVIEW 6

2.1 INTRODUCTION TO FIBER OPTIC 6

2.2 SYSTEM DESIGN CONSIDERATION 7

2.2.1 System power budget 8

2.2.2 Power at the source 8 2.2.3 Power in fiber 15 2.2.4 Power at the detector 15

2.3 CABLE CONSTRUCTION 16

2.3.1 Military standards 23

2.3.1.1 Design parameter 24

2.3.2 Fiber optic terminology 25

2.3.3 Fiber optic cost and benefits 25 2.4 CONCEPT OF GUIDED LIGHT 26

2.4.1 Core 26

2.4.2 Cladding 26

2.4.3 Step index fiber 27

2.4.4 Core modes 28

2.4.6 Light Propagation on Fiber Optic 28

2.5 SINGLE MODE FIBER OPTIC 29

2.5.2 Graded index fiber 30

2.5.2 Losses in fiber 31

2.5.2.1 Absorption 31 2.5.2.2 Scattering 32

2.5.3 Bending loss 32

2.6 FIBER OFTIC MICROBEND AND

MACROBEND SENSOR 34

2.7 FIBER OPTIC MICROBEND LOSS

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III RESEARCH METHODOLOGY 38

3.1 THEORY 38

3.2 FLOW CHART 41

3.3 TRANSMITTER CIRCUIT OPERATION 42

3.4 RECEIVER CIRCUIT OPERATION 43

IV RESULTS AND ANALYSIS 44

4.1 RESULTS 44

4.2 CALCULATION BENDING LOSS 45

4.3 MULTISIM TESTING 48

4.4 BREADBOARD TESTING 54

4.5 PROTEUS DESIGN 55

4.6 COMPARISON EACH MEASUREMENT 57

4.7 ANALYSIS THE RESULT 58

V DISCUSSION AND CONCLUSION 60

5.1 DISCUSSION 60

5.2 CONCLUSION 61

5.3 SUGGESTION 62

REFERENCES 63

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LIST OF FIGURE

FIGURE TITLE PAGE

2.1 Electromagnetic Spectrum 6

2.2 Basic fiber optic links 7

2.3 Power Supply 9

2.4 Voltage control oscillator (VCO) 10 2.5 Connection diagram 11

2.6 Transistor symbol and Schematics 11

2.7 Resistor symbols and picture 12

2.8 Potentiometer 13

2.9 Diagram voltage regulator 14 2.10 Symbol Voltage regulator 14 2.11 Fiber optic cable cross section 16 2.12 Cross section of single mode with large core diameter 17 2.13 Light propagation in single mode fiber 17 2.14 Cross section of multimode with large core diameter 18 2.15 Light propagation in step index multimode fiber 18

2.16 Light propagation in step index multimode fiber 18

2.17 Loose tube cable 19

2.18 Tight buffer cable 20

2.19 Cable construction of a plastic optic cable 21

2.20 Termini retraction and its effect on microbending 23 2.21 Basic fiber structure 27

2.22 Step index fiber 28 2.23 Numerical Aperture and Acceptance Angle 29

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2.25 Profile of index refraction for graded index fiber 30

2.26 Bending loss 33

2.27 Typical optical fiber 35

2.28 Microbends and macrobends 36

2.29 Fiber optic microbends 36

3.1 Project flow chart 41

3.2 Transmitter Circuit Operation 42

3.3 Receiver Circuit Operation 43

4.1 Condition of fiber optic 45

4.2 Bending radius against bending losses 46

4.3 Bending Loss 47

4.4 Block diagram for part of simulation 48

4.5 Connection for transmitter circuit simulation 49 4.6 Simulation result for transmitter circuit 50

4.7 DC analysis for transmitter circuit 50

4.8 AC analysis for transmitter circuit 51

4.9 Connection of receiver circuit simulation 52 4.10 Simulation result for receiver circuit 52

4.11 DC analysis receiver circuit 53

4.12 AC analysis receiver circuit 53

4.13 Transmitter circuit 54

4.14 Receiver Circuit 55

4.15 Waveform receiver 55

4.16 Transmitter circuit by Proteus 56

4.17 Transmitter layout 56

4.18 Receiver circuit by Proteus 57

4.19 Receiver layout 57

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LIST OF TABLES

TABLE TITLE PAGE

2.1 Comparison of Optical Fiber 20

4.1 Data for each part of transmitter circuit 51 4.2 Data for each part for receiver circuit 54 4.3 Comparison output transmitter and receiver

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xiv

LIST OF SYMBOL

Pi Input power

Po Output power

R Radius ℓ Length αB Bending loss

Ω _Ohms

V Voltage

α

_{Attenuation coefficient}

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CHAPTER I

INTRODUCTION

This project provides the reader with the detailed and comprehensive study of theory, design, calculation, result and problem encountered in the designing fiber optic microbend sensor. The approaches used to achieve this project are through literature review, dimensional calculation, and computer simulation. It also approaches used to analyses the characteristic and required specification before designing fiber optic microbend sensor.

Computer simulation is best technique to get the solution because it is fast and economical. The Multisim software was used to get the solution to determine its suitable parameters.

This project is divided into three stages which includes literature review and calculation followed by software simulation and the lastly design the hardware, testing, analyze the results. The fiber optic microbend sensor is designed focus to find the power

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loss in two conditions where in normal condition and the bend condition. The suitable formula to calculate the power loss to achieved the theory.

1.1 OBJECTIVE

Most of the mechanism sensors are made of switch, which can detect huge physical touch. It is very difficult to use this sensor to detect tiny touch. The fiber optic system will act as a sensitive sensor because of its power differences when there is

bending at the fiber optic cable. The technology the fiber is widely is use and become one of the important technologies in new era. Fiber optic is one of ways to upgrade the

communication system.

The objectives of this project are;

1. To design and build fiber optic microbend sensor that able to measure the differences power loss.

2. To compare the power loss between normal and bend condition of the fiber optic.

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1.2 SCOPE OF WORK

This project mainly focuses on the power loss from fiber optic where the system will act as a sensitive sensor because of its power differences when there is bending at the fiber optic cable. The first part of this project is to study literature. Then designing the system simulation and collecting the formula related to power loss to build the fiber optic microbend system.

From the theory, the formula power loss was found and from that, the calculation of power loss are determine where it is achieved the theory. The circuit transmitter and the receiver are designed and testing in Multisim software to determined the suitable parameters. From that, the simulations are making from the designed system. The hardware is designed and the system tested. The result were compared and analyzed.

There are six parts scope of works;

1. Study about fiber optic, power loss and transmitter and receiver circuit design. In this part, it need to find the formula to calculate the power loss, parameter of circuit and design the circuit with computer software to make sure the fiber optic microbend sensor design is perfect and success.

2. Develop the equations that related with the project to calculate the power loss in fiber optic in two conditions where normal and bend condition.

3. By using the multisim software the expected result for the power loss can be earned. Simulation process is one of the engineering methods to get the expected result without using any material that costly.

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4. When obtain an applicable circuit from this simulation, the hardware can be started.

5. Test the hardware after the whole process is done.

6. Compare result with the expected result in simulation.

1.3 PROBLEM STATEMENT

These projects try to make the fiber optic act as a sensor and compare power loss between normal and bend condition. Fiber optic have many advantage compare where the physically small, high capacity, huge bandwidth where fiber can transmit a mind-

boggling quantity of data with extremely good transmission quantity. So that we choose the fiber optic as a sensor and it is very sensitive where can detect the small power loss in normal or bend condition.

1.4 METHODOLOGY

At the first, start planning the project with the literature review for the related journal, books and all information from internet, magazine and each other. With the all information, develop an equation to get the expected result by simulation. Try to run the simulation to look their expected result before design the hardware. If not, back to simulation once again.

If the expected result shows the accurate value that we want, design the hardware and test it. Then measure and calculate the result to compare with the simulation result. If the hardware result shows the perfect result it seem the project is successfully done. If not, back to hardware and test it again until we get the accurate result. Lastly, at the end of the research the whole process of the project will be written into thesis.

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1.5 THESIS OUTLINE

There are several outline contain in this thesis where the first one is objective of this project. To finish this project, the methodology was followed. After that, the

simulation and measurement of the result were compared and analysed. The thesis outline is shown as below:

1. Objective 2. Scope of works 3. Problem Statement 4. Methodology 5. Literature review 6. Research methodology 7. Results and analysis 8. Discussion and conclusion

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CHAPTER II

LITERATURE REVIEW

This chapter will explain the basic concept and theories needed for development and implementation of the project. Besides, this chapter will provide information about fiber optic bending loss.

2.1 INTRODUCTION TO FIBER OPTIC

Fiber optic data transmission systems send information over fiber by turning electronic signals into light. The electromagnetic spectrum is composed of visible and near-infrared light like that transmitted by fiber and all other wavelengths used to transmit signals such as AM and FM radio and television. The figure 2.1 shown the electromagnetic spectrum where there is contain the frequency and the wavelength used to transmit signal [1].

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The term wavelength refers to the wave like property of light, a characteristic shared by all forms of electromagnetic radiation. Wavelength is the measurement of the distance a single cycle of an electromagnetic wave covers as it travels through a complete cycle. Wavelengths for fiber optics are measured in nanometers [1].

Figure 2.2 Basic fiber optic links

The figure 2.2 shown the basic fiber optic link is a fiber optic system where it is similar to the copper wire systems they are rapidly replacing. The principle of this system is use light pulses (photons) to transmit data down fiber lines, instead of electronic pulses to transmit data down copper lines. Transmitter is contains with driven, source, and source to fiber connection. It essentially converts coded electrical signals into equivalently coded light pulses. At the opposite end of the fiber optic, known as the optical receiver or detector. The purpose of an optical receiver is to detect the received light incident on it and to convert it to an electrical signal containing the information overcome on the light at the transmitting end [2].

2.2 SYSTEM DESIGN CONSIDERATIONS

The purpose of the fiber optic system is involves many interrelated functions and devices but all system is begin with the set of basic design specifications. The application requirements considered the types of signals, distances to be covered and number of connections to be made along with applicable performance standards and resources restrains [2].

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2.2.1 System power budget

A point that have consistently presented in a variety of ways throughout is the important of optical power throughput in fiber optic communications systems. The most important parameter in fiber optic communication system is the optical power transfer function. Most importantly is the output power must be greater the input sensitivity of the receiver. The system power budget is then a calculation of the power loss in each

component of the system to ensure that enough power reaches the receiver to accurately reproduce the original input information [2].

The loss in this system must be balanced with gains in order to produce a signal that is large enough in amplitude to be accurately interpreted by the receiver but not large enough cause saturation of system component. All power budgets must be major part of the system design and availability of options and the components that best satisfy both of these conditions must be considered [1].

2.2.2 Power at the source

Where the signal first enters the system, the transmitter selected must be

appropriate for the application. The type and the number of the signals are in a particular source. The LED has less power and wider line widths than laser diodes, limiting their use to shorter distances and lower data rates. These are more stable and cheaper than laser diodes [3].

A 9V battery is used as a main voltage supply to this circuits as shown in figure 2.3. However, the circuits require both a 9-volt and a 5-volt power supplies. Therefore, a voltage regulator LM7805 has been used in order to provide both the 9V and 5V DC supply. The capacitor Cl and C2 is used to maintain the stability of the voltage supply.

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Figure 2.3 Supply by using the Voltage Regulator

The LM358 series consists of two which is independent and high gains. It is internally frequency compensated operational amplifiers which were designed purposely to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage [3].

Application areas include transducer amplifiers, dc gain blocks and all the conventional op- amp circuits which now can be more easily implemented in single power supply systems. For example, the LM358 series can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional ±15V power supplies [6].

The Characteristic of Operational Amplifier is;

• In the linear mode the input common-mode voltage range includes ground and the

output voltage can also swing to ground, even though operated from only a single power supply voltage.

• The unity gain cross frequency is temperature compensated.

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The Advantages of the operational amplifier are;

• _{Two internally compensated op amps} • _{Eliminates need for dual supplies}

• _{Allows direct sensing near GND and V}_OUT_{also goes to GND} • _{Compatible with all forms of logic}

• _{Power drain suitable for battery operation}

Figure 2.4 Voltage Controlled Oscillator (VCO)

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1.5 THESIS OUTLINE

There are several outline contain in this thesis where the first one is objective of this project. To finish this project, the methodology was followed. After that, the

simulation and measurement of the result were compared and analysed. The thesis outline is shown as below:

1. Objective 2. Scope of works 3. Problem Statement 4. Methodology 5. Literature review 6. Research methodology 7. Results and analysis 8. Discussion and conclusion

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CHAPTER II

LITERATURE REVIEW

This chapter will explain the basic concept and theories needed for development and implementation of the project. Besides, this chapter will provide information about fiber optic bending loss.

2.1 INTRODUCTION TO FIBER OPTIC

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Figure 2.2 Basic fiber optic links

2.2 SYSTEM DESIGN CONSIDERATIONS

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2.2.1 System power budget

component of the system to ensure that enough power reaches the receiver to accurately reproduce the original input information [2].

2.2.2 Power at the source

Where the signal first enters the system, the transmitter selected must be

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Figure 2.3 Supply by using the Voltage Regulator

The Characteristic of Operational Amplifier is;

• In the linear mode the input common-mode voltage range includes ground and the output voltage can also swing to ground, even though operated from only a single power supply voltage.

• The unity gain cross frequency is temperature compensated. • The input bias current is also temperature compensated.

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The Advantages of the operational amplifier are; • _{Two internally compensated op amps} • _{Eliminates need for dual supplies}

• _{Allows direct sensing near GND and V}_OUT_{also goes to GND} • _{Compatible with all forms of logic}

• _{Power drain suitable for battery operation}

Figure 2.4 Voltage Controlled Oscillator (VCO)

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