SUZAIRI BIN DAUD

UNIVERSITI TEKNOLOGI MALAYSIA

SUZAIRI BIN DAUD

A thesis submitted in fulfillment of the

requirements for the award of the degree of

Master of Science (Physics)

Faculty of Science

Universiti Teknologi Malaysia

DECEMBER 2010

To my beloved family...

ACKNOW LEDGEM ENT

Praised be to Allah s .w .t . Peace and Blessing be to Prophet Muhammad s.a.w...

In the preparation of this thesis, I was in contact with numerous researchers

and academicians. They have contributed towards my understanding and thoughts of

the Physics of sensors. In particular, I wish to express my sincere appreciation and

gratitude to my main supervisor, Prof. Dr. Jalil Ali, for his encouragement, guidance,

and friendship. I am also very thankful to my co-supervisor, Dr. Saktioto for his

guidance and motivations. Without their continued support and interest, the

completion of thesis would definitely be impossible.

I wish to express my sincere thanks to the staff of Photonics Research

Laboratory, Fibre Optics Laboratory, Optoelectronics Laboratory, librians of PSZ,

and all staffs from Institute of Advanced Photonics Science and Faculty of Science,

UTM, especially Mr. Ab. Rasid Isnin and Mr. Nasir Abu Bakar, for their help and

cooperation. My sincere appreciation also extends to all my friends who have

provided assistance and various occasions. Their views and suggestions have been

useful indeed.

Last but not least, I am very grateful to all my family members, especially my

sister, Mrs. Faridah Daud for her motivation, financial support, and patience. Also

thanks to the Ministry of Science, Technology and Innovation for supporting this

research via FRGS vote no. 78452.

ABSTRACT

A prototype outdoor fibre Bragg grating (FBG) temperature sensing system

based on a commercial FBG has been designed, constructed, developed, and its

performance evaluated. The commercial FBG sensor head has a center wavelength of

1553.865 nm, 0.24 nm bandwidth, >97 % reflectivity, and a length of (3.0+0.1) cm.

In order to reduce the optical losses of the FBG system, the shortest optical fibre path

used was (55.0+0.1) m. The temperature sensitivity of the system was evaluated for

different placement heights from the rooftop floor with and without the presence of

focusing elements. The TLS was used to provide the broadband light source via a

fibre optic cable of wavelength 1550 nm. The OSA was used to display the

transmission and reflection spectrum from which the Bragg wavelength, XB,

bandwidth, and power dip are obtained. The transmission spectrum was obtained

through direct connection to the FBG and the reflection spectrum using a (2x2) 3dB

coupler. The Bragg wavelength change with temperature changes was used to

determine the FBG system’s performance. Results obtained shows that AXB is

directly proportional to temperature changes for both transmission and reflection

spectrum with and without focusing elements at different placement heights. The

gradient of AXB versus temperature provides the sensitivity of the FBG system. The

average sensitivity of the FBG sensor system measured was 10.0 pm/°C without any

focusing element. It has an average of 12.5 pm/°C when the FBG sensor head was

focused with a convex lens and 13.9 pm/°C when focused with a hand lens. The FBG

sensor system sensitivity was increased when a hand lens was used. The sensitivity is

constant irrespective of the FBG sensor head position from the floor. Thus, a

prototype FBG sensing system has been developed for outdoor temperature

measurements.

ABSTRAK

Satu prototaip gentian parutan Bragg (FBG) bagi sistem penderia suhu di

kawasan terbuka menggunakan FBG komersil telah direkabentuk, dibangunkan,

dimajukan, dan prestasinya dinilai. Panjang deria FBG komersil tersebut mempunyai

panjang gelombang Bragg 1553.865 nm, jalur lebar 0.24 nm, pantulan >97%, dan

(3.0±0.1) sm panjang. Bagi mengurangkan jumlah kehilangan pada sistem ini,

gentian optik sepanjang (55.0±0.1) m telah digunakan. Kepekaan suhu sistem ini

dinilai pada ketinggian yang berbeza dari lantai bumbung dengan menggunakan

kanta penumpu dan tanpa meggunakan sebarang elemen penumpu. TLS

memancarkan sumber cahaya pada nilai tertentu menerusi kabel gentian optik

dengan panjang gelombang 1550 nm. OSA pula memaparkan spektrum pancaran dan

pantulan yang mana panjang gelombang Bragg, AXB, jalur lebar, dan kuasa junam

dapat diukur. Spektrum pemancar diperoleh melalui penyambungan terus dengan

FBG dan spektrum pantulan pula diperoleh dengan menggunakan gandingan (2x2)

3dB gentian optik. Perubahan panjang gelombang Bragg terhadap perubahan suhu

persekitaran digunakan untuk menilai kepekaannya. Keputusan yang diperoleh

menunjukkan perubahan panjang gelombang Bragg adalah berkadar langsung

dengan perubahan suhu bagi kedua-dua spektrum pancaran dan pantulan, dengan

atau tanpa elemen pemfokus, pada ketinggian berbeza. Kecerunan graf AXB lawan

suhu memberi nilai kepekaan sistem tersebut. Purata kepekaan sistem penderia FBG

tersebut adalah 10.0 pm/°C bagi sistem tanpa elemen pemfokus. Purata kepekaannya

bernilai 12.5 pm/°C apabila penderia tersebut ditumpukan dengan kanta cembung

dan 13.9 pm/°C bagi sistem yang ditumpukan dengan kanta tangan. Kepekaan sistem

penderia FBG tersebut meningkat apabila kanta tengan digunakan. Kepekaannya

adalah malar dengan tidak dipengaruhi oleh kedudukan FBG tersebut. Maka, satu

prototaip sistem penderia FBG bagi pengukuran suhu luar telah berjaya dibangunkan.

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOW LEDGEM ENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF APPENDICES xvi

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Background of Study 2

1.3 Problem Statements 4

1.4 Objective 4

1.5 Scope of Study 4

1.6 Significance of Study 5

1.7 Organization of Study 5

LITERATURE REVIEW

2.1 Introduction

2.2 Historical Perspective of Fibre Bragg Grating

7

7

2.3 Fibre Bragg Grating 8

2.4 Fibre Bragg Grating as a Sensor 10

2.5 Overview of Fibre Bragg Grating for Temperature Sensing 11

2.6 Advantages of Fibre Bragg Grating Sensor 13

2.7 Sun Radiation and Spectral Wavelength 15

2.7.1 Composition of Solar Radiation 16

3 THEORY 17

3.1 Introduction 17

3.2 Coupled-Mode Theory 17

3.2.1 Coupled-Mode Equations 19

3.2.2 Coupling Coefficient 20

3.3 Principle of Fibre Bragg Grating 22

3.4 Properties of Fibre Bragg Grating 22

3.4.1 Bragg Wavelength 23

3.4.2 Bragg Grating Bandwidth 24

3.4.3 Bragg Grating Reflectivity 26

3.5 Optical Response of Fibre Bragg Grating 28

3.5.1 Optical Response to Wavelength 29

3.5.2 Optical Response to Strain 29

3.5.3 Optical Response to Temperature 31

3.6 Characteristics of Fibre Bragg Grating 32

3.6.1 Bragg Condition 33

3.6.2 Transmission and Reflection in Fibre Bragg Grating 34

3.6.3 Effective Refractive Index 35

3.6.4 Grating Period 36

4 EXPERIM ENTAL SET-UP 37

4.1 Introduction 37

4.2 Measurement of Fibre Loss 37

4.3 Design of Fibre Bragg Grating Temperature Sensing 39

4.3.1 Tunable Laser Source 40

4.3.2 Optical Spectrum Analyzer 41

4.3.3 Fibre Optic Coupler 42

4.4 Measurement of Fibre Bragg Grating for Temperature

Sensing 43

4.4.1 Measurement of Transmission Spectrum 43

4.4.2 Measurement of Reflection Spectrum 44

5 RESULT AND DISCUSSION 47

5.1 Introduction 47

5.2 Fibre Loss Measurement 47

5.2.1 Fibre Loss Measurement by Experiment 48

5.2.2 Fibre Loss Measurement by Calculation 48

5.3 FBG Reflection and Transmission Spectra at Room

Temperature 50

5.4 Result of Fibre Bragg Grating for Temperature Sensing 52

5.4.1 Effect of Different Placement Height on FBG

Sensitivity 56

5.4.2 Effect of Focusing Element on FBG Sensitivity 58

5.4.2.1 Effect of Convex Lens Focusing on FBG

Sensitivity 59

5.4.2.2 Effect of Hand Lens Focusing on FBG

Sensitivity 60

5.4.2.3 Comparison of Different Focusing Elements 62

5.4.3 Bandwidth of Fibre Bragg Grating 65

5.4.6 Reflectivity of Fibre Bragg Grating 66

5.5 Interpretation and Discussion 67

6 CONCLUSION 70

6.1 Conclusion 70

6.2 Recommendation for Future Work 71

REFERENCES

Appendices A-I

72

77-91

LIST OF TABLES

TABLE NO. TITLE PAGE

Table 4.1 Details of focusing elements 39

Table 5.1 Power meter reading of fibre loss 48

Table 5.2 Sensitivity of the FBG at different height 58

Table 5.3 Effect of focusing convex lens on the sensitivity of FBG at

different placement height from the rooftop floor 60

Table 5.4 Effect of focusing convex lens on the sensitivity of FBG at

different positions from the rooftop floor 62

Table 5.5 Sensitivities of FBG for different focusing elements based on

transmission spectrum 65

Table 5.6 Sensitivities of FBG for different focusing elements based on

reflection spectrum 65

FIGURE NO. TITLE PAGE

Figure 2.1 Reflected and transmitted light in the FBG 9

Figure 2.2 The FBG system 10

Figure 3.1 Illustration of contradirectional coupling 18

Figure 3.2 Schematic of enlarge FBG 23

Figure 3.3 Calculation of FWHM using reflection spectrum 24

Figure 3.4 The FBG system 32

Figure 3.5 Transmission and reflection in FBG 35

Figure 4.1 Experimental set-up for fibre loss measurement 38

Figure 4.2 Schematic of the basic experimental set-up 39

Figure 4.3 Tunable Laser Source model MG9638A 40

Figure 4.4 Optical Spectrum Analyzer model MS9710B 41

Figure 4.5 3-dB fibre optic coupler 42

Figure 4.6 Schematic of experimental set-up to measure transmission spectrum44

Figure 4.7 Schematic of experimental set-up to measure reflection spectrum 45

Figure 4.8 Close-up of the experimental set-up 46

Figure 4.9 Experimental set-up for FBG temperature sensing 46

Figure 5.1 Reflection spectrum provided by the manufacturer, QPS

Photonics Inc, Canada 50

Figure 5.2 Reflection spectrum at 23 °C 51

Figure 5.3 Transmission spectrum at 23 °C 51

Figure 5.4 Examples of transmission and reflection spectrum 54

Figure 5.5 Examples of calculation of Bragg wavelength shift 55

Figure 5.6 Shift of Bragg wavelength in different temperature for transmission

spectrum 57

Figure 5.7 Shift of Bragg wavelength in different temperature for reflection

spectrum

Figure 5.8 Effect of a focusing convex lens on the Bragg wavelength for

different temperature from the transmission spectrum 59

Figure 5.9 Effect of focusing convex lens on the Bragg wavelength shift from

the reflection spectrum 59

Figure 5.10 Effect of hand lens focusing on the Bragg wavelength shift at

different temperature obtained from the transmission spectrum 61

Figure 5.11 Effect of hand lens focusing on the Bragg wavelength shift at

different temperature obtained from the reflection spectrum 61

Figure 5.12 Comparison of Bragg wavelength shift at 2.0 cm height 62

Figure 5.13 Comparison of Bragg wavelength shift at 30.0 cm height 63

Figure 5.14 Mean sensitivity of FBG for unfocused system 64

Figure 5.15 Mean sensitivity of FBG that focused with convex lens 64

Figure 5.16 Mean sensitivity of FBG that focused with hand lens 64

Figure 5.17 Bandwidth versus temperature for different FBG placement height 66

Figure 5.18 Reflectivity of FBG at different temperature 67

a - Core radius

b - Wavelength position at 0 °C

CMT - Coupled-mode theory

d - Power dip

dB - Decibel

DNA - Acid deoksibonukleid

E - Electric field

EMI - Electromagnetic interference

FBG - Fibre Bragg grating

FBGs - Fibre Bragg gratings

FOS - Fibre optic sensor

FWHM - Full width at half maximum

H - Magnetic field

HiBi - High birefringent

K - Grating momentum vector

k - Propagating constant vector

k - Propagating constant

k ! - Modal wavevector of the forward-propagating wave

k 2 - Modal wavevector of the backward-propagating wave

L - Grating length

MHz - Mega Hertz

Mp - Fraction of fibre mode power

N - Number of grating plane

NA - Numerical aperture

nm - nanometer

ncl - Cladding refractive index

nco - Core average index

neff - Effective refractive index

no - Average refractive index

ni - Refractive index of fibre core

n2 - Refractive index of fibre cladding

OSA - Optical Spectrum Analyzer

pm/°C - pikometer per degree Celsius

R - Reflectivity

R(L,X) - Reflectivity in the function of length and wavelength

s - Fringe visibility of the index change

T - Temperature

TLS - Tunable Laser Source

UV - Ultraviolet

UVA - Ultraviolet A

UVB - Ultraviolet B

UVC - Ultraviolet C

z - Distance along the fibre longitudinal axis

e - Permittivity

U - Permeability

ez - Strain

a - Thermo-expansion coefficient

£ - Thermo-optic coefficient

Q - Coupling coefficient

A - Grating period

Ag - Grating spacing

Apm - Phase mask period

X - Wavelength

XB - Bragg wavelength

Xin - Incident light

XB,0 - Nominal Bragg wavelength

Xo - Initial wavelength

SL - Change of length

dneff - Change of refractive index

Ak - Detuning wavevector

An - Dept of index modulation

A T - Temperature change

AXb - Bragg wavelength shift

°C - Degree Celsius

°F - Degree Farenheigh

% - Percentage

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Standard sheet of MG9638A wavelength variable laser source 77

B Wavelength standard of MS9710B Optical Spectrum Analyzer 78

C Details of fibre optic coupler 79

D Data of transmission spectrum without focusing element 80

E Data of reflection spectrum without focusing element 82

F Data of transmission spectrum with convex lens focusing element 84

G Data of reflection spectrum with convex lens focusing element 86

H Data of transmission spectrum with hand lens focusing element 88

I Data of reflection spectrum with hand lens focusing element 90

INTRODUCTION

1.1 Introduction

Over the last five decades, fibre optic sensors (FOS) have emerged as modern

device in sensing and telecommunication technologies. FOS can be classified as

fluorescent/spectrally-based, intensity-based, or interferometric. Fluorescent-decay

temperature sensor, blackbody radiation temperature sensor, Fabry-Perot temperature

sensor, interferometric temperature sensor, polarimetric temperature sensor, and dual

mode temperature sensor are examples of sensors used in fibre optic temperature

sensing. Fibre Bragg grating (FBG) has the unique advantage as an fibre optic

temperature sensor as compared with all other temperature sensors (Neil, 1990).

FBG is used in measuring the temperature accurately in a variety of

environment (Yonghang, 2004) which includes in harsh environment, underground,

and also disaster places. Fibre Bragg grating is a type of distributed Bragg reflector

constructed in a short segment of optical fibre that reflects a particular wavelength of

light and transmits all the other wavelengths. This is achieved by appending a

periodic variation to the refractive index of the fibre core, which generates a

wavelength of specific dielectric mirror. Thus, an FBG can be use as an inline optical

filter to block certain wavelength or as a wavelength-specific reflector.

The most important innovation of the 1990’s in FOS is the development of

FBG sensors. Fibre Bragg grating can used as a sensor because of its excellent

unique properties. FBG emerges as an important technology in fibre optic sensing

due to its smart structure, excellent linear characteristics, immune to electromagnetic

interference (EMI), low fibre loss, and other outstanding advantages (Lai et al.,

2002). Nowadays, decent and sophisticated techniques in temperature measurement

become very important and necessary for safety precautions in industrial

requirements (Bowei, 2004).

The FBG sensitivity measurements will be assessed for different FBG’s

position from the rooftop floor using different focusing elements at periods of the

day. The research will examine the effect of different focusing elements, FBG

positions, and temperature variations on the sensor head of the FBG. Measurements

made will be based on the transmission and reflection spectrum of the FBG.

1.2 Background of Study

A sensor is a device that measures a physical quantity and converts it into a

signal which can be read by an instrument. For example, mercury in glass

thermometer converts the measured temperature into expansion and contraction of

the liquid which can be read on a calibrated glass tube. A thermocouple converts the

temperature measurement to an output voltage which can be read by a voltmeter. For

accuracy purposes, most sensors are calibrated against known standards.

Temperature is an important and most commonly measured parameter in

everyday applications. Traditionally, the semiconductor sensor, platinum resistance

sensor, thermistor, and thermocouple are most commonly utilized for temperature

measurements. For most applications, these conventional temperature sensors can be

adequate for its purpose. However, these temperature sensors are not reliable due to

the lack of intrinsic safety, their characteristics of electrically active, and poor

lifetime at excessive temperatures (Yonghang, 2004). Furthermore, these

conventional temperature sensors are all point sensors. In other words, they are

localized sensors, which can only provide temperature reading over a small area

rather than providing an overall temperature profile (Udd, 1995). These sensors are

also suitable for the passive multiplexing, but difficult in practice, due to size

limitations (Xiaopei et al., 2004).

Optical fibre offers a number of distinguishing and excellent advantages over

conventional sensors. Fibre Bragg grating (FBG) sensor is one of the most important

and useful optical fibre sensors. The concept of FBG was discovered three decades

ago by Hill and his co-workers (Hill, 1978). However, most of the recognized

pioneering work about FBG and its applications were only published a decade later

after it’s discovery by a group of researchers at United Technology Research Centre

(Meltz et al., 1989).

FBG sensors are dielectric and virtually immune to electromagnetic

interference (EMI). It can withstand against hostile environment, including in high

and excessive temperature. It can be used to measure high temperature, until 1000 °C

(Hirayama et al., 2000). It is also utilized as a distributed sensor. In principle,

distributed sensors are different from point sensors. Here the parameter of interest is

measured with certain spatial resolution at any points along a single optical fibre.

They would permit the use of power sensors and represents more effective use of

optical fibre that are used for both measurements and data transmission, which

allows them to become more attractive.

FBG sensors can be incorporated into optical fibre cables. These sensors can

be embedded into new structure or surface bonded onto an existing structure. This

allows real time monitoring of structures (Tahir et al., 2005), ultimately leading to

truly ‘smart’, and provide fatigue data for subsequent analysis (Everal, 2000). FBGs

are able to play a crucial role in sensing technology, due to their unique smart

structure (Lai, 2002).

1.3 Problem Statem ent

The main motivation of this research is to design, construct, and develop

temperature sensor using a commercial fibre Bragg grating (FBG) sensor under

outdoor condition. To this end, a commercial germanium-doped silica fibre Bragg

grating is used. This research will examine the effect of temperature variations on the

characteristics of an outdoor FBG temperature sensor. How does the characteristics

of FBG sensor respond to changes under different environment conditions and

placement heights of FBG? How does the focusing elements such as convex lens and

hand lens affect the sensitivity of FBG? These investigations can be used to

determine the performance of FBG sensor for outdoor temperature measurement. Its

performance will be evaluated based on the transmission and reflection spectrum.

1.4 Objective

The objective of this research is to design, construct, and develop an outdoor

FBG temperature sensor system for different FBG placement heights from the

rooftop floor. The effect of FBG at different heights from the rooftop floor will be

evaluated. The research will also analyze the effect of focusing elements on the FBG

sensor head based on the transmission and reflection spectrum.

1.5 Scope of Study

This research starts with a literature review on FBG. The literature review

will focused on temperature sensing of FBG and its sensitivity. The theory involved

in temperature sensing will be discussed. The principle of FBG is based on coupled­

mode theory (CMT). The FBG spectrum at room temperature were taken for both

transmission and reflection spectrum as the reference for Bragg wavelength shift.

The measurement of FBG temperature sensing was made at the different placement

heights of FBG with different focusing elements used at the sensor head. The convex

lens and hand lens were used as the focusing elements in this research. The

performance or sensitivity of the FBG will be analyzed in terms of the Bragg

wavelength shift.

1.6 Significance of Study

This research enables us to understand FBG temperature sensing performance

by examining the characteristics and properties of the FBG. Initially studies shows

that there are rapid fluctuations in outdoor temperature. The sudden change in

outdoor conditions such as temperature variation, rain, and effect of wind blowing

may affect the stability of the reading.

With the increasing needs for health monitoring in structures such as bridges,

tunnels, highways, dams, aircraft wings, and spacecraft fuel tanks, it is imperative to

design and develop an effective sensor system which can detect any sudden changes

in strain, pressure, and temperature. The practical challenges here may include

decoupling at different sensing parameters for long term thermal stability of the FBG

under outdoor environment. This enables us to apply the FBG temperature sensor in

a variety of fields, such as medical, construction, manufacturing, industry, and many

more.

1.7 Organization of Study

This thesis consists of six chapters and begins with a brief introduction of the

research background and work undertaken as described in Chapter 1. It includes the

background study, problem statement, objective, scope, and significance of the study.

The literature review on FBG fundamental, an overview of FBG for temperature

sensing, the properties of sun radiation and spectral wavelength are described in

Chapter 2. In Chapter 3, the theory of FBG will be discussed in detail. This includes

the coupled-mode theory, the properties, optical response, and characteristics of

FBG. Chapter 4 describes the FBG experimental set-up and the research

methodology used in this research. Chapter 5 gives the results, analysis, and

discusses the performance testing evaluation of FBG for outdoor temperature

sensing. The Bragg wavelength response with respect to the temperature variation is

analyzed. Parameters such as sensitivity, bandwidth, and reflectivity are analyzed for

different FBG’s height placement from the rooftop floor and for different focusing

elements placed on the FBG sensor head. Finally, Chapter 6 provides the conclusion

of this study and suggestion for further work.

Archer, Cristina; Jacobson, Mark. "Evaluation of Global Wind Power". Stanford.

http://www.stanford.edu/group/efmh/winds/global_winds.html. Retrieved

2008-06-03.

Bowei, Z. (2004). “High Temperature Sensors based on Hydrogen Loaded Fiber

Bragg Gratings ". M. Sc. Thesis. Concordia University, Canada.

Bowei, Z. and Mojtaba, K. (2005). “Characteristics o f Fiber Bragg

Grating Temperature Sensor at Elevated Temperatures".

Proceedings of the 2005 International Conference on MEMS,

NANO and Smart Systems (ICMENS’05).

Edmon, C., Chen-Chun Y., Stephen, E S., Stephen, J., and Ralph, P T. (2004).

“Characterization o f the response o ffibre Bragg gratings fabricated in

stress and geometrically induced high birefringence fibres to

temperature and transverse load". UK: Institute of physics publishing.

13, 888, 894, 895.

Georges T., Delevaque E., Monerie M., Lamouler P., and Bayon J. F ,” Pair

induced quenching in erbium doped silicate f ib e r s ’, IEEE Optical

Amplifiers and Their Applications, Technical Digest, 17, 71 (1992).

Grattan, K. T. V., and Meggit, B. T. (2000). “Optical Fiber Sensor: Advanced

Applications- Bragg Gratings and Distributed Sensors ". Boston. Kluwer

Academic Publishers.

Hill, K. O., Fujii, Y., Johnson, D.C., and Kawasaki, B. S. (1978). “Photosensitivity in

Optical Fiber Waveguides; Application to Reflection Filter Fabrication ”.

Applied Physics Letter. 32 (10), 647-649.

Hill, K.O. (2002). “Fiber Optics Handbooks-Fiber, Deviced, and Systems fo r optical

Communication”. America. McGraw-Hill.

Hilaire, St., Pierre; G. J. A. (2005). “ United States Patent 6904201 ”. Retrieved on

July 6, 2005, from http://www.freepatentsonline.com/6904201.html.

Ho, S. P., Ali, J., Rahman, R. A., Saktioto (2008). “Growth Dynamics and

Characteristics o f Fabricated Fiber Bragg Grating using Phase Mask

M ethod”. Workshop on Recent Advances of Low Dimensional Structures

(WRA-LDSD). 7-9 April 2008. The University of Nottingham, UK.

Ho, S. P., “Properties o f Fabricated Fiber Bragg Grating fo r Temperature Sensing

Using Phase Mask Technique” . Master Thesis, UTM, (2008).

Jeff, H. (2002). “Understanding Fiber Optics (Fourth Edition)”. London: Prentice

Hall, 153-157.

Juergens, J. (2005). “Thermal Evaluation o f Fiber Bragg Gratings at Extreme

Temperatures”. Canada Technology and Communication Research Center.

Jung, J. et al., 1999. “Fiber Bragg Grating Temperature Sensor with Controllable

Sensitivity”, Appl. Opt, 38(13), Pg. 2752-2754.

Kashyap, R. (1999). “Fiber Bragg Gratings”. London: Academic Press Inc. 185

189.

Kawasaki, B. S., Hill, K. O., Johnson, D. C., and Fuji, Y. (1978). “Narrow-Band

Bragg Reflectors in Optical F ibers”. Optics Letter. 3:66-68

Lai, Y. C., Qiu, G. F., Zhang, W., Zhang, L., Bennion, I., Granttan, K.T.V. (2002).

“Amplified Spontaneous Emission-based Technique fo r Simultaneous.

Measurement o f Temperature and Strain by Combining Active Fiber with

Fiber Gratings ". Review of Instrument, American Institute of Physics (AIP).

73 (9).

Lam, D.K.W. and Garside, B.K. (1981). “Characterization o f Single-mode Optical

Fiber Filters ". Applied Optics. 20, 440 - 445.

Malo, B., et al., “Apodised in fiber Bragg grating reflectors photoimprinted using a

phase m ask”, Electronic Letters, Vol. 31, 1995 pp. 223-225.

Meltz, G., Morey, W.W. and, Glen W.H. (1989). “Formation o f Bragg Gratings in

Optical Fibre by Transverse Holographic M ethod". Optics Letters. 14 (15),

823-825.

Morey, W. M., Ball, G. A. and Meltz, G. (Feb. 1994). “Photoinduced Bragg

Gratings in Optical Fibers ". Optics and Photocs News: 8-14.

Muhs, Jeff (2007). “Design and Analysis o f Hybrid Solar Lighting and Full

Spectrum Solar Energy System” Oak Ridge National Laboratory.

N. Hirayama, Y. Sano, ISA Transaction 39 (2000) 169-173. “Fiber Bragg Grating

Temperature sensor fo r Practical Use".

Neil, J. Guillermo (1999). “Development o f Temperature Compensated Fiber Optic

Strain Sensors based on Fiber Bragg Gratings ". University of Toronto.

Institute for Aerospace Studies.

Noyes, WM (1860-03-31). "The Law of Light" (PDF). The New York Times.

http://query.nytimes.com/mem/archivefree/pdf?_r=1&res=9503E1D81E30EE

34BC4950DFB566838B679FDE&oref=slogin. Retrieved 2008-05-18.

Othonos, A. “Fiber Bragg gratings”, Review of Scientific Instruments, Vol. 68,

1997, pp.4309-4341.

Othonos, A. and Kalli, K. (1999). “Fiber Bragg Gratings: Fundamentals and

Applications in Telecommunication and Sensing”. Boston (USA): Artech

House Inc.

Rahman, R. A., Ikhsan, S., Supian, H. M. (2000). “Fibre Optic Bragg Grating

Sensors:A New Technology fo r Smart Structure Monitoring in Malaysia ”.

IEEE 0-7803-6355-8.

Ramesh, S. K.; Kuo, C. W, Righini, G. C., Najafi, S. I. (1999). “Design

and fabrication o f a Fiber Bragg Grating temperature sensor”.

International Society for Optical Engineering proceedings series.

Ronald, S., 2003: “Seeing The Light" Feb 2003; Trade & Industry.

Shilton AN, Powell N, Mara DD, Craggs R (2008). ""Solar-powered aeration and

disinfection, anaerobic co-digestion, biological CO(2) scrubbing and biofuel

production: the energy and carbon management opportunities o f waste

stabilisation pon ds”. Water Sci. Technol. 58 (1): 253-258.

Simpson, A. G. (2005). “Optical Fibre Sensor and their Application” . Ph.D. Thesis,

Aston University.

Strasser, T. A., J. R. Pedrazzai, and M. J. Andrejio, “Reflective mode conversion

withUV-induced phase grating in two-mode fiber’", Conference on Optical

Fiber Communication OFC 1997, Dallas, TX, FRS 16-21, 1997, paper FB3.

Snyder, A. W., and Love, J. D. (1983). “Optical Waveguide Theory”. Chapman &

Hall,London.

Tahir, B. A., Ali, J. and Rahman, R. A. (2005). “Strain Measurements Using Fibre

Bragg Grating Sensor”. American Journal of Applied Science (Special

Issue).40-48.

Tanaka, T. et al, “100 Ghz-spacing 8-channel Light Source Integrated with Gratings

and LDs on PLC Platform”. The Institude of Electronics, Information and

Communication Engineers, Technical Report of IEICE, (2002).

Udd, E., Nelson, D., and Lawrence, C. (1997). “Multiple axis strain sensing using

fib re gratings written onto birefrigent single mode optical fib re”.

Williamsburg: Proc. 12th Int. Conf. Optical Fibre Sensors. 354-357.

Xiaopei, C., Yan, Z., Gang, P., Jiju, A. (2004). “Experimental design in Fiber Optic

D evelopm ent”. International Journal of productivity and Performance, 53, 8.

Yonghang, S., Jinglei, H., Weizhong, Z., Tong, S., Kenneth, T. V. G., William,

D.N.P.(2004). “Fiber-optic Sensor System fo r Heat-flux M easurement”.

Review o f Scientific Instruments.