UNIVERSITI PUTRA MALAYSIA

NOR AZURA MALINI BT AHMAD HAMBALI

FK 2010 38

SINGLE-WAVELENGTH RING-CAVITY FIBER LASER WITH IMPROVED TUNABILITY BASED ON NONLINEAR STIMULATED

BRILLOUIN SCATTERING

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SINGLE-WAVELENGTH RING-CAVITY FIBER LASER WITH

IMPROVED TUNABILITY BASED ON NONLINEAR STIMULATED

BRILLOUIN SCATTERING

By

NOR AZURA MALINI BT AHMAD HAMBALI

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirements for the Degree of Doctor of Philosophy

November 2010

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Dedicated to;

Abah,

Mak,

Abang,

Yang,

Adik Hafizul

My sweet Azri

Lecturers,

Friends.

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment

of the requirement for the degree of Doctor of Philosophy

SINGLE-WAVELENGTH RING-CAVITY FIBER LASER WITH

IMPROVED TUNABILITY BASED ON NONLINEAR STIMULATED

BRILLOUIN SCATTERING

By

NOR AZURA MALINI BT AHMAD HAMBALI

November 2010

Chairman: Professor Mohd. Adzir Mahdi, Phd

Faculty: Engineering

Stimulated Brillouin scattering (SBS) is a nonlinear phenomenon that occurs in an

optical fiber as a result of interaction between an injected coherent pump signal and

an acoustic wave, resulting in backward propagating signal named Stokes wave.

Practically for single-mode silica fiber (SMF), the Stokes wave was found to be

downshifted by 0.08 nm (10 GHz) from the injected signal wavelength, through the

Doppler effect. SBS generation has been considered generated a lot of interest for its

deployment in a number of applications, such as microwave generation, frequency

shifting, narrow-bandwidth amplification and fiber laser.

This thesis focuses on the utilization of the nonlinear effects in dispersion

compensating fiber (DCF), particularly the SBS to generate a single-wavelength laser

in ring-cavity configurations. In this thesis, three types of fiber laser in ring-cavity

configurations were investigated namely; Brillouin fiber laser (BFL), Brillouin

Erbium fiber laser (BEFL), and Brillouin Raman fiber laser (BRFL). All the results

presented in this thesis have been published.

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For ring cavity BFL, the lowest Brillouin threshold power of 0.9 mW, Brillouin

signal (BS) peak power of 7.28 mW and the flatness of the BS power were obtained.

The lasing wavelength of BFL structure can be tuned freely in the cavity because the

laser structure does not produce any self-lasing cavity modes. The lasing wavelength

is strictly dependent on the BP wavelength and subject to the availability of

amplification bandwidth.

The impact of Erbium-doped fiber amplifier (EDFA) location in the BEFL structure

was investigated. A single-wavelength BEFL-1 structure in which the Brillouin

pump (BP) is pre-amplified before entering the DCF produced 25.1 mW of BS signal

power and tuning range of 50 nm. In contrast the BS signal power of 15.5 mW and

1.4 mW was obtained from BEFL-2 and BEFL-3, which can only be tuned over 28

nm and 3 nm respectively. In conclusion, the BEFL-1 generated higher gain

efficiency to suppress the self-lasing-cavity modes in the cavity and provided higher

BS signal power. Next, the characteristics of this BEFL structure in which the BP is

pre-amplified before entering the DCF was demonstrated with variation of output

coupling ratios from 10% to 99%. The highest BS signal power of 28.7 mW and

wider tuning range over 60 nm without any self-lasing cavity modes were obtained.

For the final experiment, the BRFL characteristics in terms of BS signal power,

threshold power and tuning range were reported. The BS signal power of 2.71 mW,

threshold power of 27 mW and BS signal power flatness of 26 nm were obtained. It

is evidently shown that the BRFL can be operated freely without any appearance of

the self-lasing cavity modes for all cases of the injected RPU power.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia

sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

ISYARAT PANJANG GELOMBANG TUNGGAL RONGGA CINCIN

GENTIAN LASER DENGAN PENAMBAHBAIKAN JULAT PENALAAN

BERASASKAN PADA PENYERAKAN BRILLOUIN TERANGSANG

Oleh

NOR AZURA MALINI BT AHMAD HAMBALI

November 2010

Pengerusi: Profesor Mohd. Adzir Mahdi, Phd

Fakulti: Kejuruteraan

Penyerakan Brillouin terangsang (SBS) merupakan fenomena tidak linar yang terjadi

disebabkan oleh interaksi antara penyuntikkan isyarat pam optik koheren dan

gelombang akustik di dalam gentian optik, ini menyebabkan penghasilan isyarat

yang merambat ke belakang yang dinamakan sebagai gelombang Stokes. Untuk mod

gentian mod tunggal (SMF), gelombang Stokes telah dipisahkan pada jarak 0.08 nm

(10 Ghz) daripada penyuntikkan isyarat pam, ini kenali sebagai kesan Doppler.

Generasi SBS telah dipertimbangkan oleh pelbagai lapisan penyelidik sejak

bertahun-tahun lagi dan ini menghasilkan minat yang mendalam untuk

membangunkan pelbagai aplikasi seperti generasi gelombang mikro, penganjakkan

frekuensi, penguatan lebar jalur sempit, dan laser gentian.

Tesis ini menumpukan kepada penggunaan kesan-kesan tidak linar di dalam

penyerakan menggantikan gentian (DCF), dimana pada dasarnya SBS digunakan

untuk menjana isyarat panjang gelombang tunggal di dalam struktur rongga cincin.

Dalam tesis ini, tiga jenis struktur rongga cincin telah dikaji, dinamakan sebagai laser

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gentian Brillouin (BFL), laser gentian Brillouin Erbium (BEFL) dan laser gentian

Brillouin Raman (BRFL). Semua keputusan yang dihasilkan di dalam tesis ini telah

diterbitkan.

Bagi BFL, takat permulaan Brillouin yang terendah telah diperolehi sebanyak 0.9

mW, puncak kuasa BS sebanyak 7.28 mW dan kerataan bagi kekuatan isyarat BS

telah diperolehi. Panjang gelombang bagi struktur BFL boleh menalakan secara

bebas dalam rongga, kerana mod berbolak-balik tidak dihasilkan. Ditegaskan,

panjang gelombang bergantung kepada panjang gelombang BP dan juga tertakluk

kepada ketersediaan penguatan lebar jalur.

Kesan lokasi bagi penguat gentian terdop Erbium (EDFA) di dalam struktur BEFL

telah diselidik. Untuk jarak gelombang tunggal bagi struktur BEFL-1 di mana pam

Brillouin (BP) adalah pra-diperkuatkan sebelum memasuki DCF telah menghasilkan

kekuatan isyarat BS sebanyak 25.1 mW dan juga julat penalaan pada jarak 50 nm.

Sebaliknya, kekuatan isyarat BS sebanyak 15.5 mW dan 1.4 mW telah diperolehi

daripada BEFL-2 dan BEFL-3, yang juga menghasilkan julat penalaan pada jarak 28

nm dan 3 nm. Kesimpulannya, BEFL-1 telah menghasilkan kecekapan yang tinggi

untuk menekan mod berbolak-balik dan ia juga dapat menghasilkan kekuatan isyarat

BS yang lebih tinggi. Seterusnya, ciri-ciri struktur BEFL di mana pam Brillouin (BP)

yang pra-diperkuatan sebelum memasuki DCF telah ditunjukkan dengan

menggunakan pelbagai nilai nisbah gandingan keluaran dari 10% hingga 99%.

Kekuatan isyarat BS yang tinggi pada 28.7 mW, dan julat penalaan yang lebih luas

pada jarak 60 nm tanpa kemunculan mod berbolak-balik telah dihasilkan.

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Untuk kajian yang terakhir, ciri-ciri BRFL dalam perkara yang berkenaan dengan

kuasa BS, kuasa takat permulaan dan julat penalaan telah disiasat. Kekuatan isyarat

BS sebanyak 2.71 mW, kuasa takat permulaan sekitar 27 mW dan. kerataan bagi

kekuatan isyarat BS pada jarak 26 nm telah diperolehi. Dengan ini, terbukti bahawa

BRFL boleh dikendalikan secara bebas tanpa sebarang kemunculan mod berbolak-

balik pada semua kes penyuntikan kuasa RPU.

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ACKNOWLEDGEMENTS

All praise is to ‘ALLAH THE ALMIGHTY’ for giving me the opportunity, patience

and guidance in completing this project successfully.

I am indebted to many for their support during the research and writing of this thesis.

First and foremost, I would like to thank my advisor, Professor Mohd. Adzir Mahdi

for sharing his unique views of science, constant interests, advices, suggestions and

constructive criticism. He has taught me many optical concepts which serve to add

depth and perspective to my knowledge of physics and engineering. I am indebted to

Assoc. Prof. Dr. M. H. Al-Mansoori, for the insights into the design and

experimental problems. I would also wish to express my gratitude to my supervisory

committee members, Dr. Ahmad Fauzi Abas and Dr. M. Iqbal Saripan.

I could not complete these thesis successfully without the love and support of my

family especially Abah, Mak, Abang, Yang, Adik Hafizul , my little cute Azri and all

of above.

Finally, many thanks are extent to all my course mates and also my understanding

best friends Padil, Maslinda, Eija, Fidah, Za, and Fini. I am also hugely indebted to

my lab-mates especially, Muhammad Ajiya, Yeo Kwok Shien, Shee Yu Gang and

Muhammad Hafiz, Hafizah Zubaidah, Nelidya for their supporting attitude, advise

critics, understanding and attention towards the completion of my thesis. They are

eager to give their time to help me when I was stuck. Thank you very much.

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Approval Sheet 1

I certify that an Examination Committee met on date 9 November 2010 to conduct

the final examination of Nor Azura Malini Bt Ahmad Hambali on her Doctor of

Philosophy thesis entitled “Single-wavelength Ring Cavity Fiber Laser based with

Improved Tunability on Nonlinear Stimulated Brillouin Scattering” in

accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and

Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee

recommends that the candidate be awarded the Doctor of Philosophy. Members of

the Examination Committee are as follows:

Mohd. Fadlee bin A. Rasid

PhD

Faculty of Engineering,

University Putra Malaysia

(Chairman)

Alyani binti Ismail

PhD

Faculty of Engineering

Universiti Putra Malaysia

(Member)

Salasiah binti Hitam

PhD Faculty of Engineering

Universiti Putra Malaysia

(Member)

PhD

Internal examiner

_______________________________

BUJANG KIM HUAT, PhD

Professor/Deputy Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfilment of the requirement for the degree of Doctor of Philosophy.

The members of the Supervisory Committee were as follows:

Mohd. Adzir Mahdi, PhD

Professor

Faculty of Engineering

University Putra Malaysia

(Chairman)

Ahmad Fauzi bin Abas @ Ismail, PhD

Lecturer

Faculty of Engineering

University Putra Malaysia

(Member)

M. Iqbal bin Saripan, PhD

Lecturer

Faculty of Engineering

University Putra Malaysia

(Member)

Mohammed Hayder Al-Mansoori, PhD

Associate Professor

Faculty of Engineering

University Tenaga Nasional

(Member)

_________________________________

HASSANAH MOHD GHAZALI, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

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DECLARATION

I declare that the thesis is my original work except for quotations and citations which

have been duly acknowledged. I also declare that it has not been previously, and is

not concurrently submitted for any other degree at Universiti Putra Malaysia or other

institutions.

_________________________________________

NOR AZURA MALINI BT AHMAD HAMBALI

Date: - 9 November 2010

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TABLE OF CONTENT

Page

DEDICATION ii

ABSTRACT iii

ABSTRAK v

ACKNOWLEDGEMENT viii

APPROVAL ix

DECLARATION xi

LIST OF TABLES xv

LIST OF FIGURES xvi

LIST OF ABBREVIATIONS / SYMBOL xix

CHAPTER

1 INTRODUCTION

1.1 Overview 1

1.2 Problem Statement 3

1.2.1 Lower threshold power 4

1.2.2 High power efficiency 4

1.2.3 Tuning range 4

1.3 Motivation 5

1.3 Objectives 5

1.4 Scopes of work 6

1.5 Thesis Organization 7

2 LITERATURE REVIEW

2.1 Fiber laser 10

2.2 Nonlinear effect 11

2.3 Stimulated Brillouin Scattering (SBS) 12

2.4 Single-wavelength laser 13

2.5 Brillouin threshold 15

2.6 Theoretical of Brillouin gain 17

2.7 Erbium Doped Fiber Amplifier (EDFA) 21

2.7.1 Theoretical of Erbium gain 23

2.8 Raman amplification 27

2.8.1 Raman Scattering 27

2.8.2 Theory of Raman gain 29

2.9 Brillouin Fiber Laser (BFL) 30

2.10 Brillouin/Erbium fiber laser (BEFL) 33

2.11 Brillouin-Raman Fiber Laser (BRFL) 36

3 METHODOLOGY

3.1 General research development 42

3.2 Equipments and components 43

3.3 The general methodology flow chart

3.3 Investigation on the effect of EDFA location in ring

cavity Brillouin-Erbium fiber laser 45

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3.4 Optimization of output coupling ratio on the performance

of a ring-cavity BEFL 49

3.5 Effect of output coupling ratio on the performance

of ring-cavity BFL 52

3.6 Single-wavelength ring-cavity BRFL 54

4 PUBLISHED PAPER 1: INVESTIGATION ON THE EFFECT

OF EDFA LOCATION IN RING CAVITY BRILLOUIN-ERBIUM

FIBER LASER 62

Abstract 62

References and links 63

1 Introduction 65

2 Brillouin-Erbium fiber laser structures 67

3 Brillouin Stokes laser power 69

4 Self-lasing cavity modes 70

5 Tuning Range 74

6 Conclusion 77

Copyright permission 79

5 PUBLISHED PAPER 2: OPTIMIZATION OF OUTPUT

COUPLING RATIO ON THE PERFORMANCE OF RING

CAVITY BRILLOUIN-ERBIUM FIBER LASER 80

Abstract 80

1 Introduction 81

2 Experimental Setup 83

3 Results and Discussion 84

4 Conclusion 92

References 93

Copyright permission 95

6 PUBLISHED PAPER 3: EFFECT OF COUPLING RATIO

ON THE PERFORMANCE OF RING-CAVITY BRILLOUIN

FIBER LASER 97

Abstract 97

1 Introduction 98

2 Experimental Setup 99

3 Results and Discussion 100

4 Conclusion 107

References 108

Copyright permission 111

7 PUBLISHED PAPER 4: SINGLE-WAVELENGTH

RING-CAVITY BRILLOUIN-RAMAN FIBER LASER 112

Abstract 112 1 Introduction 112

2 Experimental Setup 113

3 Results and Discussion 116

4 Conclusion 118

References 121

Copyright permission 124

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8 CONCLUSION 125

8.1 Performance Comparison 125

8.2 Conclusion 127

8.3 Thesis Contributions 130

8.4 Future research directions 130

REFERENCES 132

APPENDIXES 147

LIST OF PUBLICATION 149

BIODATA OF STUDENT 151