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UNIVERSITI PUTRA MALAYSIA
RAMZIA SALEM
FK 2011 133
MULTI-WAVE LENGTH BRILLOUIN-ERBIUM FIBER LASER UTILIZING BISMUTH-OXIDE ERBIUM DOPED FIBER
INCORPORATING HIGH AND LOW NONLINEAR FIBERS
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MULTI-WAVELENGTH BRILLOUIN-ERBIUM FIBER LASER UTILIZING
BISMUTH-OXIDE ERBIUM DOPED FIBER INCORPORATING HIGH AND LOW
NONLINEAR FIBERS.
By
RAMZIA SALEM
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in
Fulfilment of the Requirements for the Degree of Doctor of Philosophy
September 2011
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DEDICATION
This work is dedicated to the loving memory of my late parents and to my beloved supporting
sisters and brothers, nieces and nephews and last but not least to my loving husband and my
lovely kids, Rania and Rayan.
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of the
requirement for the degree of Doctor of Philosophy
MULTI-WAVELENGTH BRILLOUIN-ERBIUM FIBER LASER UTILIZING
BISMUTH-OXIDE ERBIUM DOPED FIBER INCORPORATING HIGH AND LOW
NONLINEAR FIBERS.
By
RAMZIA SALEM
September 2011
Chair: Mohd Adzir Bin Mahdi, PhD
Faculty: Engineering
Multiwavelength fiber lasers are of great interest in the wavelength division multiplexing
systems. To accommodate for the exponential growth in internet, the transmission capacity has
to be enhanced in terms of the number of channels. In order to achieve this aim, one approach is
to reduce the channel spacing between the wavelengths. The other approach is to increase the
gain bandwidth restricted by erbium doped fiber amplifier. Since the bandwidth is dependent on
the Er3+
structure in glass material, many fiber amplifiers have been developed to broaden the
gain bandwidth. Bismuth-based erbium-doped fiber (Bi-EDF) demonstrates fundamental
properties showing broadband emission range and can be doped with Er3+
without experiencing
the negative results of ion-quenching and clustering effects compared to silica-based glass
allowing the erbium concentration to be more than 3000 ppm. This dissertation presents
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experimental design and development of multiwavelength Brillouin-erbium fiber laser
(MWBEFL) sources operating in the L-band transmission window utilizing 2.49 m Bi-EDF.
Three different laser designs have been realized by utilizing stimulated Brillouin scattering
(SBS) effect in optical fibers to generate multiple lasers. Two types of special fibers, photonic
crystal fiber (PCF) with high nonlinearity and large effective area fiber (LEAF) with low
nonlinearity, are being investigated individually. These two types of fibers are then merged
together to investigate the laser’s performance parameters.
The first design for multiwavelength laser comb comprises of Bi-EDF and 50 m photonic crystal
fiber in a ring cavity configuration. This fiber laser is solely pumped by a single 1455 nm Raman
pump laser to exploit its higher power delivery compared to that of a single mode laser diode
pump. At 264 mW pump power and 1 mW Brillouin pump (BP) power, 38 output channels in
the L-band have been realized with optical signal-to-noise ratio above 15 dB and Stokes lines
spacing of 0.08 nm. The laser exhibits a tuning range of 12 nm and produces stable Stokes lines
across the tuning range between Brillouin pump wavelengths of 1603 and 1615 nm. The tuning
range of 12 nm is considered high since very short length, 50 m PCF is used. However, due to
the spectral broadening of the laser lines caused by four-wave mixing (FWM) effect associated
with high nonlinear fibers, the optical signal-to-noise ratio (OSNR) is degraded and the tuning
range is limited to only 12 nm.
Another multiwavelength laser comb using 2.49 m Bi-EDF with different lengths of LEAF in a
ring cavity configuration has been developed. The Bi-EDF is used as the linear gain medium
and LEAF is used as the non-linear gain medium for SBS. Out of the four different lengths, the
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longest length of 25 km LEAF exhibits the widest tuning range of 44 nm (1576 to 1620 nm) in
the L-band at 264 mW pump power and 5 mW Brillouin pump power. In addition, a total of 15
output channels are achieved with total average output power of –8 dBm from this laser
structure. All Brillouin Stokes signals exhibit high peak power of above –20 dBm per signal and
their OSNR of greater than 15 dB. The Bi-EDF based MWBEFL is also characterized with 22
km Vascade® L1000, another type of LEAF, as the Brillouin gain medium. This fiber generates
more Stokes lines than the 25 km LEAF with higher Stokes lines output power. However, the
tuning range achieved is 38 nm compared to 44 nm for 25 km LEAF.
The third structure of MWBEFL incorporating cascaded PCF and two different lengths of LEAF
individually is demonstrated. In this design, the tuning range is enhanced significantly reaching
54 nm from 1566 -1620 nm, at 264 mW pump power and 5 mW BP power, without a trace of
self-lasing throughout, utilizing 22 km Vascade® L1000 along with 50 m PCF. Five output
channels can be tuned along the whole region of 54 nm. Although this design provides high
tuning range, but the number of output channels is reduced. At Raman pump power of 395 mW
and 5 mW BP power, up to 9 channels can be widely tuned over 49 nm. The channels exhibit
high output power and high stability with average power fluctuation of 0.34 dB over 60 minutes
time span. The effect of FWM is reduced thus enhancing the OSNR by 5.2 dB due to the
suppression of turbulent waves effect owing to the larger core size in LEAF.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi
keperluan untuk ijazah Doktor Falsafah
LASER GENTIAN BRILLOUIN-ERBIUM PELBAGAI JARAK GELOMBANG
MENGGUNAKAN GENTIAN TERDOP BISMUTH-OKSIDA ERBIUM BERSAMA
GENTIAN TIDAK LINEAR TINGGI DAN RENDAH
Oleh
RAMZIA SALEM
September 2011
Pengerusi: Mohd Adzir Bin Mahdi, PhD
Fakulti: Kejuruteraan
Laser gentian pelbagai jarak gelombang adalah sangat menarik dalam sistem multipleks divisyen
jarak gelombang. Bagi memenuhi perkembangan eksponensial internet, kapasiti transmisi telah
diperbaiki dari segi bilangan saluran. Untuk mencapai sasaran ini, satu cara adalah
mengurangkan jarak pemisahan saluran antara jarak gelombang. Cara yang lain adalah
meningkatkan lebar jalur yang dihadkan oleh penguat gentian terdop erbium.Memandangkan
lebar jalur bergantung kepada struktur Er3+ dalam bahan gelas, banyak penguat gentian
dibangunkan untuk meluaskan lebar jalur. Gentian terdop erbium berasaskan bismusth (Bi-EDF)
mendemonstrasikan ciri-ciri asas yang menunjukkan lingkungan pancaran jalur lebar dan boleh
didopkan dengan Er3+ tanpa menghadapi keputusan negatif penghapusan ion dan kesan
pengelompokan berbanding gelas berasaskan silika lalu membenarkan konsentrasi ion erbium
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untuk melebihi 3000 ppm. Disertasi ini membentangkan rekabentuk dan pembangunan
eksperimental punca laser gentian Brillouin-erbium pelbagai jarak gelombang (MWBEFL)
menggunakan 2.49 m Bi-EDF yang beroperasi di tingkap transmisi L-band. Tiga rekabentuk
laser berlainan telah diwujudkan dengan menggunakan kesan penyerakan Brillouin terangsang
(SBS) dalam gentian optik bagi menghasilkan laser yang banyak. Dua jenis gentian khas disiasat
secara individu iaitu, gentian kristal fotonik (PCF) dengan ketidaklinear yang tinggi dan gentian
kawasan efektif besar (LEAF) dengan ketidaklinear yang rendah. Kedua-dua gentian ini
kemudiannya digabungkan bersama untuk menyiasat parameter prestasi laser itu.
Rekabentuk pertama bagi laser sikat pelbagai jarak gelombang mengandungi Bi-EDF dan 50 m
PCF dalam konfigurasi rongga cincin. Laser gentian ini adalah dipamkan sendirian oleh satu
laser pam Raman 1455 nm bagi mempergunakan penghantaran kuasa yang tinggi berbanding
pam diod laser mod tunggal. Pada kuasa pam 264 mW dan 1 mW kuasa pam Brillouin (BP), 38
saluran hasilan dalam L-band diwujudkan dengan nisbah isyarat kepada gangguan optikal
(OSNR) di atas 15 dB dan jarak pemisahan garisan Stokes pada 0.08 nm. Laser itu menunjukkan
lingkungan talaan sebanyak 12 nm dan menghasilkan garisan Stokes yang stabil merentasi
lingkungan talaan di antara jarak gelombang pam Brillouin pada 1603 dan 1615 nm. Lingkungan
tallan 12 nm ini dikira tinggi memandangkan PCF 50 m yang sangat pendek digunakan. Walau
bagaimanapun, oleh kerana peluasan spektral garisan laser itu disebabkan kesan pencampuran
empat-gelombang (FWM) yang dikaitkan dengan gentian tidak linear yang tinggi, OSNR
berkurangan dan lingkungan talaan dihadkan kepada hanya 12 nm.
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Satu lagi laser sikat pelbagai jarak gelombang menggunakan 2.49 m Bi-EDF dengan LEAF
berbeza kepanjangan dalam konfigurasi rongga cincin telah dibangunkan. Bi-EDF digunakan
sebagai perantara penambah linear dan LEAF digunakan sebagai perantara penambah tidak
linear bagi SBS. Daripada 4 panjang yang berbeza, LEAF yang terpanjang pada 25 km
menunjukkan lingkungan talaan yang terluas sebanyak 44 nm (1576 to 1620 nm) dalam L-band
pada kuasa pam 264 mW dan BP 5 mW. Sebagai tambahan, sejumlah 15 saluran hasilan dicapai
dengan purata kuasa hasilan pada -8 dBm bagi struktur laser ini. Semua isyarat Stokes Brillouin
menunjukan kuasa puncak yang tinggi melebihi -20 dBm bagi setiap isyarat dan OSNR melebihi
15 dB. MWBEFL berasaskan Bi-EDF ini turut dikaji sifatnya dengan 22 km Vascade L1000,
sejenis LEAF lain, sebagai perantara penambah Brillouin. Gentian ini menghasilkan lebih
garisan Stokes berbanding 25 km LEAF dengan kuasa hasilan garisan Stokes yang lebih tinggi.
Walau bagaimanapun, lingkungan talaan yang dicapai adalah 38 nm berbanding 44 km bagi 25
km LEAF.
Struktur ketiga MWBEFL menggabungkan PCF berturutan dan dua kepanjangan LEAF yang
berbeza didemonstrasikan secara individu. Dalam rekabentuk ini yang menggunakan 22 km
Vascade L1000 disamping 50 m PCF, lingkungan talaan telah ditingkatkan dengan jelas,
mencapai 54 nm dari 1566 kepada 1620 nm, pada kuasa pam 264 mW dan BP 5 mW tanpa
sebarang tanda lasing sendirian. 5 saluran hasilan boleh ditala sepanjang seluruh kawasan 54 nm
itu. Walaupun rekabentuk ini memberikan lingkungan talaan yang luas, tetapi bilangan saluran
hasilan berkurangan. Pada kuasa pam maksimum, 395 mW kuasa pam dan 5 mW kuasa BP,
sehingga 9 saluran hasilan boleh ditala seluas 49 nm. Saluran-saluran itu menunjukkan kuasa
hasilan dan kestabilan yang tinggi dengan purata perubahan kuasa sebanyak 0.34 dB dalam sela
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masa 60 minit. Kesan FWM dikurangkan lalu OSNR diperbaiki sebanyak 5.2 dB kerana
peredaman gelombang bergolak disebabkan saiz teras yang lebih besar di dalam LEAF.
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ACKNOWLEDGEMENTS
First and foremost, it is with the help of God that this PhD dissertation was possible and
accomplished.
I consider myself one of the lucky ones whom had parents and family who from the start had
done everything to motivate, support and guide me to set the goals and strive to achieve them.
Both have stressed the importance of hard work, education, regimented discipline, and constant
and never ending improvement. Without their endless love and support, I would not have been
able to go on.
I would also like to express my deepest gratitude to my supervisor Prof. Mohd Adzir Mahdi who
has given me the privilege to work under him. By accepting me at the very late stage of my
school studies has utterly been a savior and no words could express my endless gratitude. My
sincere thanks and gratitude go to my co-supervisor Assoc. Prof. Mohammad Al-Mansoori. His
continuous mental and professional support has been beyond words. I also would like to extend
my thanks to Dr. Hashim B. Hizam and Dr. Samsul Bahari B. Mohd Noor for their support
throughout my PhD program. Many thanks extended to my lab mates at the Photonics lab for
their encouraging talks and smiles.
Last but not least, my special thanks and gratitude extended to my family in Yemen, my husband
and my little girl, Rania. I hope I can make it up to her one day for all the times she needed me
but I had to complete this work. As for my husband and my sisters and brothers, I can not thank
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them enough for standing by me and believing in me. Without their love and support, this
dissertation would not have come true.
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Approval Sheet 1
I certify that an Examination Committee has met on _______________ to conduct the final
examination of Ramzia Abdulmalik Salem on her degree thesis entitled “Multiwavelength
Brillouin-Erbium Fiber Laser Utlilizing Bismuth-Oxide Erbium Doped Fiber
incorporating High and Low Nonlinear Fibers” in accordance with Universiti Pertanian
Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree)
Regulations 1981. The Committee recommends that the student be awarded the Doctor of
Philosophy.
Members of the Examination Committee were as follows:
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Faculty of Engineering
University Putra Malaysia
(Internal Examiner)
Faculty of Science
University Putra Malaysia
(Internal Examiner)
(External Examiner)
Bujang Kim Huat, PhD Professor and 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
fulfillment of the requirement for the degree of Doctor of Philosophy. The members of the
Supervisory Committee were as follows:
Mohd Adzir bin Mahdi, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Hashem B. Hizam, PhD
Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Samsul Bahari b. Mohd. Noor, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Mohammed Hayder Al-Mansoori, PhD
Associate Professor,
Faculty of Engineering
Sohar University, Oman
(External Member)
BUJANG BIN KIM HUAT, 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 at any other institution.
RAMZIA SALEM
Date: 8 September 2011
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TABLE OF CONTENTS
Page
DEDICATION iii
ABSTRACT iv
ABSTRAK vii
ACKNOWLEDGEMENTS xi
APPROVAL xiii
DECLARATION xv
LIST OF TABLES xix
LIST OF FIGURES xx
LIST OF ABBREVIATIONS xxiv
CHAPTER
1 INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 4
1.3 Research Objectives 5
1.4 Scope of Work 6
1.5 Thesis organization 7
2 LITERATURE REVIEW AND THEORETICAL
BACKGROUND
2.1 Introduction 9
2.2 Laser Action
2.3 Fiber Lasers
2.4 Fiber Non-linearities
2.4.1 Nonlinear Refraction
2.4.2 Nonlinear Phase Shift
2.4.2.1 Self-Phase Modulation
2.4.2.2 Cross-Phase Modulation
2.4.3 Four-Wave Mixing
2.4.4 Stimulated Inelastic Scattering
2.4.4.1 Stimulated Raman Scattering
2.4.4.2 Stimulated Brillouin Scattering
2.5 Optical Fiber Amplifiers
2.6 Erbium Doped Fiber Amplifier
2.6.1 Background
2.6.2 Operating Principles in EDFA
10
13
14
14
15
16
17
18
21
21
22
28
29
29
30
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2.6.3 Bismuth Oxide based Erbium Doped Fiber
2.6.4 Amplification properties of bismuth-oxide erbium
doped fiber
2.6.5 Numerical Model for Bi-EDFA
2.7 Multiwavelength Brillouin Erbium Fiber Lasers
2.7.1 Theory of multiwavelength Brillouin/erbium fiber
laser
2.8 Critical Review
2.9 Summary
32
33
34
38
42
48
50
3 RESEARCH METHODOLOGY
3.1 Introduction 52
3.2 Research Design Flow Chart 52
3.3 Design of MWBEFL Bi-EDF based incorporating PCF 55
3.4 Multiwavelength BEFL with large effective area fiber 57
3.5 Multiwavelength BEFL with Cascaded Brillouin gain
from PCF and LEAF
3.6 Experimental Setup
3.7 Characterization of MWBEFL Source
3.7.1 Threshold Power
3.7.2 Channels’ Peak Power and Total Output Power
3.7.3 Number of Output Channels
3.7.4 Free-running Cavity Modes
3.7.5 Tuning Range
3.7.6 Optical Signal to Noise Ratio
58
59
61
61
63
64
65
66
67
3.8 Summary
67
4 MUTLIWAVELENGTH BEFL WITH PHOTONIC
CRYSTAL FIBER
4.1 Introduction
4.2 Principle of Operation of Bi-EDF
4.3 Performance Parameters of Multiwavelength BEFL
4.3.1 BEFL Threshold Power
4.3.2 Number of Stokes lines
4.3.3 Total Stokes lines Output Power
4.3.4 Tuning Range
4.3.5 Stability
4.4 Summary
69
69
70
71
74
84
86
91
92
5 MULTIWAVELENGTH BEFL WITH LARGE EFFECTIVE
AREA FIBER
5.1 Introduction 94
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5.2 Performance Parameters of BEFL with LEAF
5.2.1 Threshold Power
5.2.2 Total Stokes lines Output Power
5.2.3 Number of Stokes lines
5.2.4 Tuning Range
5.3 Performance Parameters of BEFL with 22 km
Vascade®L1000 Fiber
5.3.1 Introduction
5.3.2 Threshold Power
5.3.3 Total Stokes Lines Output Power
5.3.4 Number of Stokes lines
5.3.5 Tuning Range
5.3.6 Stability
5.4 Summary
95
95
98
99
102
105
105
105
107
108
112
114
115
6 MULTIWAVELENGTH BEFL WITH CASCADED
PHOTONIC CRYSTAL FIBER AND LEAF
6.1 Introduction 116
6.2 Principle of Operation
6.3 Results and Discussions
116
120
6.3.1 Threshold power
6.3.2 Number of output channels
6.3.3 Total Stokes Lines Output Power
6.3.4 Tuning Range
6.3.4.1 Effect of Raman Pump Power on Tuning
Range
6.3.4.2 Effect of Brillouin Pump Power on
Tuning Range
6.3.5 Stability
6.3.6 Optical Signal-to-Noise Ratio
6.4 Conclusion
120
123
129
131
132
133
139
140
143
7 CONCLUSION AND FUTURE WORK
7.1 CONCLUSION
7.2 SUMMARY
7.3 FUTURE WORK
145
149
150
REFERENCES/BIBLIOGRAPHY 151
BIODATA OF STUDENT 159