先進光調變與多工技術在直接偵測光傳輸系統上的性能評估與分析

國 立 交 通 大 學

光電工程研究所

博士論文

先進光調變與多工技術在直接偵測光傳

輸系統上的性能評估與分析

Advanced Modulation and Multiplexing

Techniques for Direct Detection Optical

Transmission Systems

先進光調變與多工技術在直接偵測光傳

輸系統上的性能評估與分析

Advanced Modulation and Multiplexing

Techniques for Direct Detection Optical

Transmission Systems

國立交通大學 電機學院

光電工程研究所

博士論文

A Dissertation

Submitted in Partial Fulfillment of the Requirements

for the Degree of Doctor of Philosophy in

The Institute of Electro-Optical Engineering

College of Electrical and Computer Engineering

National Chiao Tung University

Hsin-Chu, Taiwan, R.O.C.

I

先進光調變與多工技術在直接偵測光傳輸

系統上的性能評估與分析

研究生：彭煒仁 指導教授：祁 甡

國立交通大學 電機學院

光電工程研究所

摘要

在本論文中我們將簡介數種已提之先進光調變格式以及光多工技術，其工作原理以 及目前所遇到的議題將一併於論文中予以討論以及部分解決。其中光多工技術包含光正 交頻分多工 (OFDM) 以及光碼分多工 (OCDMA) 兩種技術，而光調變格式主要是高頻 譜效能(>1 bit/symbol) 之格式包含多階相位或多階振幅調變格式 。

針對直接偵測OFDM 下我們提出射頻輔助正交分頻多工(RF-tone assisted OFDM)以 及廣義虛擬單邊帶正交頻分多工(Generalized Virtual SSB-OFDM)等兩種技術。此技術置 放一射頻次載波於信號頻帶邊緣作為遠端直接偵測參考信號之用。使用我們的技術後， 和同性質的直接升頻(direct up-conversion) 調變器相比，可節省一半數位轉類比器 (DAC) 的取樣速度，而其 DAC 有限的取樣速度在高容量 (≥ 10 Gbps) 的光通訊傳輸下 目前乃是主要瓶頸。此外，我們成功地傳輸10 Gbps OFDM 訊號經過 1600 km 的標準單 模光纖後僅3 dB 的損傷，驗證此技術在未來光通訊的應用潛力。 於光調變格式中，我們實驗以及理論驗證其使用簡易、低廉的單顆光調變器產生數 種複雜傳輸訊號的可能性。這在未來講求低價格，高效能的光通訊網路上是一大躍進。 除此之外我們更進而分析數種不同調變格式的性能理論上限: 量子限制 (quantum limit)。 此一限制給出最佳性能指標以簡化工程應用上所能達成的最佳性能。 最後我們研究光碼分多工技術在局部網路(LAN)上的應用。我們使用費比布洛自注 入雷射以及光纖光柵串列提出廉價光碼分多工光源。藉著針對每一個光柵施以溫度或應

II

力的控制我們可以改變所要傳送地點的用戶碼。接著提出交叉頻率分組方式以降低在多 用戶光碼分多工系統下所遭遇到的多重存取干擾。最後，我們首次實驗驗證多載波碼分 多工系統於光接取網路上的應用可能。

III

Advanced Modulation and Multiplexing Techniques for

Direct Detection Optical Transmission Systems

Student: Wei-Ren Peng Advisor: Sien Chi

Institute of Electro-Optical Engineering

College of Electrical and Computer Engineering

National Chiao Tung University

ABSTRACT

In this dissertation, we review and propose several new approaches for orthogonal frequency division multiplexing (OFDM), advanced modulation formats, and code division multiplexing (OCDM) techniques in optical transmission systems.

For OFDM, we propose an RF-tone assisted OFDM and virtual single-sideband OFDM (VSSB-OFDM) systems for direct detected optical transmission. With an RF tone inserted at the edge of the signal band, the sensitivity and CD tolerance are both improved compared to the previous power modulated SSB-OFDM. Besides, our approach also relaxes the bandwidth requirement for digital to analog converter (DAC) which would be very critical in a high speed transmission with a data rate of ≥ 10 Gbps. In addition, we firstly propose a 2x2 matrix equalization technique to jointly compensate the distortions resulted from both the transmission and the imbalances of the optical modulator. Moreover, we successfully transmit a 4-QAM, 10-Gbps signal through 1600 km uncompensated standard single mode fiber (SSMF) with only ~ 3 dB penalty, which is smaller than any other proposed direct-detected transmission systems.

For advanced modulation formats, we numerically evaluate and experimentally demonstrate the generation of complex modulation formats by using one dual-drive

IV

Mach-Zehnder modulator (DD-MZM). We also analyze the performance bound, i.e. quantum limit, of 4ASK format. We further propose a phase modulated 4ASK (PM4ASK) format which shows a better CD, PMD and filtering tolerances compared to conventional 4ASK format.

For CDMA, we propose a simple and cost-effective fast frequency hopping CDMA (FFH-CDMA) light source which uses a self-injected Fabry Perot laser and one string of fiber Bragg grating array (FBGA). By tuning the stress of each individual grating, we can encode the transmitted data by the destination codeword. Aimed to eliminate the inherent multiple access interference (MAI) in optical FFH-CDMA, we propose a frequency-interleaved multi-group approach which fully uses the frequency gap between the gratings to reduce the spectrum overlapping among different users, and design the new codeword searched by computers which is suitable for this proposed technique. Finally we versify this technique by some simulation results.

V

誌 謝

(Acknowledgements)

感謝祁甡 (Dr. Sien Chi) 老師這段期間在學業上細心地指導與教誨，也讓我學習到 許多做人處事之道。同時也感謝南加州大學電機系教授 Dr. Alan E. Willner 耐心地教導， 使得在研究上所遇到的瓶頸，總是能迎刃而解。 此外，也感謝實驗室合作教授交大光電所陳智弘 (Dr. Jyehong Chen)以及清大電通 所馮開明 (Dr. Kai-Ming Feng) 的長期幫忙和指點。特別感謝台灣交通大學: 彭朋群 (Peng-Chun Peng)，錢鴻章(Hung-Chang Chien)，林俊廷(Chun-Ting Lin)以及黃明芳 (Ming-Fang Huang)博士；以及南加州大學: 章波(Bo Zhang)，張林(Lin Zhang)，武曉霞 (Xiaoxia Wu)以及台灣同胞楊振源(Jeng-Yuan Yang)同學等同儕的相互勉勵及協助，使研 究之路得以順利且充滿樂趣。

VI

Contents

Chinese Abstract……….………

I

English Abstract………...……

III

Acknowledgement………....

V

Contents………...………

VI

List of Figures……….

XII

List of Table…….………...

XIX

List of Acronyms……….…...

XX

Chapter 1

Introduction

1.1 Background…..………...1

1.2 Motivation………..………..……….4

1.3 Organization of the Dissertation………..….………...5

References……….………...……….7

Chapter 2

Overviews of Optical Modulation and Multiplexing Techniques

2.1 Introduction……….………...8

2.2 Optical Orthogonal Frequency Division Multiplexing (OFDM) 2.2.1 Coherent Detection………9

2.2.2 Direct Detection………...………11

2.3 Advanced Modulation Formats 2.3.1 Differential Phase Shift Keying (DPSK)………..………13

VII

2.3.3 Other Four-Level Modulation Formats……….14

2.3.4 Analysis Tools for Modulation Formats…………...………15

2.4 Optical Code division Multiplexing (OCDM) 2.4.1 Direct-Sequence CDMA (DS-CDMA)………16

2.4.2 Fast Frequency Hopping CDMA (FFH-CDMA)……….17

2.4.3 Spectra-Encoded CDMA (SE-CDMA)………...……….17

References………...18

Chapter 3

Optical Orthogonal Frequency Division Multiplexing

3.1 Introduction……….28

3.2 RF tone Assisted Optical OFDM Systems 3.2.1 Experimental Demonstration of a Coherently Modulated and Directly Detected Optical OFDM System Using an RF-Tone Insertion 3.2.1.1 Introduction…………...………29

3.2.1.2 Concept………30

3.2.1.3 Equalization………...…………..….31

3.2.1.4 Experimental Setup and Results………...………32

3.2.1.5 Summary………...……34

3.2.2 Experimental Demonstration of Compensating the I/Q Imbalance and Bias Deviation of the Mach-Zehnder Modulator for an RF Tone Assisted Optical OFDM System 3.2.2.1 Introduction………...……34

3.2.2.2 Effects of I/Q Imbalance and Bias Deviation………..…….35

3.2.2.3 Compensation for I/Q Imbalance and Bias Deviation………..……36

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3.2.2.5 Summary………..….37

3.2.3 Tunable Optical Wavelength Conversion of a 10 Gb/s OFDM Data Signal Using a Periodically-Poled Lithium Niobate Waveguide 3.2.3.1 Introduction………...38

3.2.3.2 Concept……….39

3.2.3.3 Experimental Results………....39

3.2.3.4 Summary………...…41

3.2.4 Theoretical Investigations 3.2.4.1 The Optimum Carrier to Signal Power Ratio (CSPR)……….…….41

3.2.4.2 Bit Error Rate Calculation for a Single Sideband OFDM Signal with Direct Detection optically Pre-amplified Receivers……….………42

3.3 Virtual Single Sideband OFDM (VSSB-OFDM) 3.3.1 Experimental Demonstration of 340 km SSMF Transmission Using a Virtual Single Sideband OFDM Signal that Employs Carrier Suppressed and Iterative Detection Techniques 3.3.1.1 Introduction………...………46 3.3.1.2 Concept………..47 3.3.1.3 Equalization ……….49 3.3.1.4 Experimental Results………50 3.3.1.5 Summary………...52

3.3.2 Experimental Demonstration of 1600 km SSMF Transmission of a Generalized Direct Detection Optical Virtual SSB-OFDM System 3.3.2.1 Introduction………..………….52

3.3.2.2 Concept……….…………53

IX

3.3.2.4 Summary……….………..55

References………..………..56

Chapter 4

Advanced Modulation Formats

4.1 Introduction……….79

4.2 DQPSK Generation by Using One Dual-Drive Mach-Zehnder Modulator (DD-MZM) 4.2.1 Introduction……….79

4.2.2 Concept………...80

4.2.3 Experimental Setup and Results……….82

4.2.4 Summary……….83

4.3 Theoretical Investigations for DQPSK signal generated by one DD-MZM 4.3.1 Introduction……….………84

4.3.2 Optical Spectra and Bit Error Rate Analysis……….………..85

4.3.3 Numerical Results………..……….86

4.3.4 Summary………...………..88

4.4 Generation of ASK/RZ-DPSK signal by using one DD-MZM 4.4.1 Introduction………..88

4.4.2 Concept………...………90

4.4.3 Numerical Results………..……….91

4.4.4 Summary……….93

4.5 Quantum Limit of 4-level ASK System 4.5.1 Introduction……….………93

4.5.2 The Optimum Level and Quantum Limit for 4ASK…….………..95

X

4.5.4 Summary………...………100

4.6 Improvement of Dispersion and Optical Filtering Tolerances for Quaternary Intensity Detection Using Phase Modulation and Balanced Detection Technique 4.6.1 Introduction………..101

4.6.2 Generation of 4ASK and PM4ASK………..102

4.6.3 Performance Bound, Dispersion and Optical Filtering Tolerances…….…..103

4.6.4 Summary………..……….106

References……….107

Chapter 5

Optical Code Division Multiplexing

5.1 Introduction……….130

5.2 Light Source of OCDMA 5.2.1 Introduction……….130

5.2.2 Concept………131

5.2.3 Experimental Setup and Results……….132

5.2.4 Summary……….134

5.3 Reducing Multiple Access Interference in an Optical Fast Frequency Hopping CDMA (OFFH-CDMA) System 5.3.1 Introduction……….135

5.3.2 Concept………137

5.3.3 Code Design and Performance Analysis..………...139

5.3.4 Numerical Results….………..145

5.3.5 Summary……….148

5.4 Multi-Carrier CDMA 5.4.1 Introduction……….149

XI

5.4.2 Concept……….150

5.4.3 Experimental Setup and Results………151

5.4.4 Summary………...…..152

References………...153

Chapter 6

Conclusions and Future Work

6.1 Conclusions………...……...169

6.2 Future Work………...170

References………...…………..173

XII

List of Figures

Chapter 2

Fig. 2.1 OFDM fundamentals: transmitter and receiver………..21 Fig. 2.2 (a) The transmitter and (b) receiver in a Coherent Optical OFDM (CO-OFDM)

system. ………...…………..21

Fig. 2.3 Coherent transmitter and receiver for polarization division multiplexing

(PDM). …...………....………...22

Fig. 2.4 Various proposed direct detection OFDM: (a) using Hermitian symmetry and an

optical filter; (b) using up-conversion and an optical filter, (c) using a frequency domain Hilbert transform. For all the three types of OFDM formats, only one photodiode is needed at the receiver………23

Fig. 2.5 Optical DPSK: (a) transmitter and (b) receiver………....24 Fig. 2.6 Optical DQPSK: (a) transmitter and (b) receiver. The purpose of the two sets of

optical delay interferometers is to feed the data into a simple binary decision circuit………...……….25

Fig. 2.7 Optical ASK/DPSK: (a) transmitter and (b) receiver..……….……...……...…....26 Fig. 2.8 Optical four level ASK (4ASK): transmitter and receiver……...……….…..26 Fig. 2.9 Optical CDMA: (a) direct sequence (DS-CDMA) and (b) fast frequency hopping

(FFH-CDMA), (c) spectra encoding CDMA (SE-CDMA)………...…………...27

Chapter 3

Fig. 3.1 Operation principles for (a) the conventional power-modulated SSB-OFDM, and

(b) the proposed RF-tone assisted OFDM-A (gapped) and OFDM-B (interleaved)..………...……59

XIII

Fig. 3.3 Experimental results of error vector magnitude versus the carrier to signal power

ratio.………...…………..60

Fig. 3.4 Experimental results of error vector magnitude versus the input power per

span..………...………...…..60

Fig. 3.5 Experimental results of BER versus OSNR. The OSA resolution is 0.2

nm…...………...…………...61

Fig. 3.6 Simulation of the error vector magnitude as a function of the chromatic

dispersion………..………...…61

Fig. 3.7 (a) The MZM imbalance and bias deviation, and the corresponding output spectrum

of the RF-tone assisted OFDM and (b) the interfered signals after photodiode and the proposed 2x2 equalization matrix compensating the imbalance effects. ………...…………..62

Fig. 3.8 Experimental setup of the joint equalization technique for MZM imbalances and

fiber CD. ……….………...…………..63

Fig. 3.9 Measured RF spectra after PD, (a) ideal operation, (b) with a amplitude imbalance

of α = 1.38, (c) with a phase deviation of 0.1 π, (d) with a bias deviation of ∆V / Vrms, where Vrms is the root-mean square of the input signal, (e) with a time

misalignment of Td = 10 ps. ………...…...…………..64

Fig. 3.10 EVM versus amplitude imbalance, (b) EVM versus phase deviation, (c) EVM

versus bias deviation, where Vrms is the root-mean square of the input signal, (d) EVM versus the time misalignment.………..………....…………..65

Fig. 3.11 Bit error rate (BER) versus the optical signal to noise ratio (OSNR) for without

and without I/Q compensation scheme, before and after 800 km uncompensated transmission. Note that there is no I/Q imbalance for this plot………...….65

Fig. 3.12 Required OSNR (0.1 nm) for BER = 10-3 versus the fiber distance with MZM

XIV

Fig. 3.13 Concept of waveleng th conversion using SFG/DFG in a PPLN

waveguide………..………..66

Fig. 3.14 Experimental setup of OFDM wavelength conversion. The constellation and RF

spectra of 8 & 16-QAM are inserted. ………....…………..67

Fig. 3.15 Optical spectra after wavelength conversion. QPM: quasi-phase matching

wavelength.………...……...67

Fig. 3.16 BER performance of the 10 Gb/s RF-tone assisted OFDM signal for both back to

back and after conversion………...…………..68

Fig. 3.17 BER performance of 8-QAM and 16-QAM for both back to back (bb) and after

wavelength conversion………...…………..68

Fig. 3.18 BER with different subcarrier numbers….………..69 Fig. 3.19 The progress of the power spectra of the SSB-OFDM signal and the ASE noise

before and after the photodiode………...………...…………..69

Fig. 3.20 Simulated electrical power spectra of the OFDM signal………...……..70 Fig. 3.21 BER versus OSNR with different optical filter bandwidth (OBW). The data rate is

10 Gbps with 4-QAM. The OFDM bandwidth is ~11.8 GHz. The Q-factor is extracted from all the received constellation point.………...…………..70

Fig. 3.22 BER versus OSNR with different OFDM QAM formats. The optimum optical

bandwidths for 4-, 16- and 64-QAM 10-Gbps SSB-OFDM signals are 13, 6.7 and 4.6 GHz. ………...………….…..71

Fig. 3.23 Transmitter architectures for the (a) conventional SSB-OFDM and (b) the

proposed virtual SSB-OFDM. (H. T.: Hilbert Transform) ……...…………..72

Fig. 3.24 Iterative detection for the virtual SSB-OFDM………...…………..72 Fig. 3.25 Experimental setup of the virtual SSB-OFDM...………...…………..73 Fig. 3.26 Measured error vector magnitude (EVM) versus the receiver iteration

XV

Fig. 3.27 Measured EVM versus the carrier to signal power ratio (CSPR)…..…………..74 Fig. 3.28 Measured bit error rate versus the optical signal to noise ratio for the conventional

and the virtual SSB-OFDM. The OSA resolution is 0.2 …………...…………..74

Fig. 3.29 Simulated results for the conventional and the virtual SSB-OFDM. OMI (optical

modulation index) is defined as [Vin]rms/Vπ, where [Vin]rms is the root-mean square of the electrical input to the MZM and Vπ is the switching voltage of the MZM……….………...…………..75

Fig. 3.30 The proposed generalized VSSB-OFDM (GVSSB-OFDM) with tunable gap. The

optimum gap trades the signal-signal beat interference (SSBI) with the image interference………...…………..76

Fig. 3.31 Experimental setup for the GVSSB-OFDM system...………...…………..76 Fig. 3.32 Measured EVM versus the frequency gap for different values of CSPR.…..…..77 Fig. 3.33 Measured EVM versus the carrier to signal power ratio……..…...…..………..77 Fig. 3.34 Measured EVM versus the iteration number…..………...…………..78 Fig. 3.35 Measured BER versus the OSNR. ………...………...78

Chapter 4

Fig. 4.1 (a) Principle of the generation of an optical DQPSK signal with a single MZM. (b)

Symbol positions and the constellation diagram.………...…..113

Fig. 4.2 Experimental setup…..………...…………..113 Fig. 4.3 Optical spectra of the generated NRZ, and RZ signals with different duty

cycle……….114

Fig. 4.4 Back to Back eye diagrams of the NRZ and RZ signals with different duty cycles

before and after detection. The horizontal scales are all with 20 ps/div. ………114

Fig. 4.5 Bit error ratio of the DQPSK signals before and after 60 km fiber

XVI

Fig. 4.6 (a) DQPSK transmitter with one DD-MZM and one pulse carver, (b) DQPSK

transmitter with two parallel MZMs and one pulse carver, and (c) Receiver numerical model.……...………...…………115

Fig. 4.7 (a) The optical spectra of the DQPSK signal generated by conventional two

parallel MZMs. (b) The optical spectra of DQPSK signal generated by one DD-MZM.………...…………..116

Fig. 4.8 (a) BER versus OSNR for one-MZM scheme with Td = 20 ps time mismatch

between the data and the pulse modulators. (b) The power penalty of the RZ formats versus the relative delay between the data and the pulse modulators.………...…………..117

Fig. 4.9 (a) BER of the two-MZMs schemes. (b) BER of the one-MZM scheme…..…..118 Fig. 4.10 The proposed scheme for ASK/ CSRZ-DPSK modulation………..119 Fig. 4.11 System test link for the proposed ASK/RX-DPSK modulation scheme.…...…..119 Fig. 4.12 Back to back receiver sensitivities of label and payload versus label extinction

ratio. ………...…...………..120

Fig. 4.13 Eye patterns of the payload before and after the low pass electrical filter, with and

without the optimization scheme.………...…...…………..120

Fig. 4.14 BER performances of the label in back to back and 120 km SSMF

transmission……….………...…………..121

Fig. 4.15 BER performances of the payload in back to back and 120 km SSMF

transmission.………...…………..121

Fig. 4.16 The bit error rate for 4-ASK as a function of photons/bit with various

M. ………...……….……..122

Fig. 4.17 The optimum normalized multilevel spacing and thresholds as a function of

photons/ bit with (a) M = 1, (b) M=10, (c) M=30, (d) M=50. (e) The optimum normalized multilevel spacing and thresholds at a bit error rate of 10-9 as a

XVII

function of M………..……….………...…………..123

Fig. 4.18 Required photons/bit to achieve a bit error rate of 10-9 for both the binary and the

quaternary formats…………..………...…………..124

Fig. 4.19 Bit error rate versus the photons/bit for the RZ-4ASK format for the back to back

and CD = 510 ps/nm with the exact and Gaussian approximation method……….………...…………..124

Fig. 4.20 The modulation and demodulation of (a) the conventional 4ASK and (b) the

proposed PM4ASK formats.………..………...…………..125

Fig. 4.21 (a) Bit error rates for RZ-4ASK and RZ-PM4ASK formats calculated by

Monte-Carlo (MC) error counting and Karhunen-Loeve (KL) semi-analytical method. (b) BER versus SNR for both 4ASK and PM4ASK formats under the matched (QL) and optimum practical filters…...………...…………....126

Fig. 4.22 (a) Required SNR for BER=10-9 versus residual dispersion. (b) Required SNR for

BER=10-9 versus differential group delay…...………...…………..127

Fig. 4.23 Required SNR for BER=10-9 versus differential group delay with residual

dispersion of 255 and 510 ps/ nm………...………...…………..128

Fig. 4.24 Required SNR at BER = 10-9 versus the optical bandwidth for the conventional

RZ4ASK and proposed RZ-PM4ASK formats………..…………...…………..128

Chapter 5

Fig. 5.1 Experimental setup of the proposed OFFH-CDMA light source

module……….………...…………..157

Fig. 5.2 Time domain waveforms at positions of A, B, and C, respectively..…………..157 Fig. 5.3 (a) Optical spectrum of the FP-LD output. The inset shows the detail near the

center wavelength, and (b) the time domain single pulse with a pulse-width of ~ 56.4 ps.………...…………..158

XVIII

Fig. 5.4 (a) The output spectrum after encoding, where, λ1=1548.82 nm, λ2=1549.9 nm,

and λ3=1550.98 nm. (b) Encoded waveform with a bit and chip durations of 2.1 ns and 500 ps, respectively. The sequence order in time domain is λ1Æλ2Æλ3……….………...…………..159

Fig. 5.5 (a) The output spectrum after encoding, where λ1=1548.82 nm, λ2=1549.9 nm,

and λ4=1552.06 nm. (b) Encoded signal with bit and chip durations of 2.1ns and 5 0 0 p s , r e s p e c t i v e l y. T h e s e q u e n c e o r d e r i n t i m e d o m a i n i s λ1Æλ2Æλ4……….………...…………..160

Fig. 5.6 The transmitter and receiver for an OFFH-CDMA system with the fiber Bragg

grating (FBGA) as the encoder and decoder……...………...…………..161

Fig. 5.7 (a) and (b) are a star network and the frequency allocation approach for

conventional scheme. (c) and (d) are a star network and the frequency allocation approach with our proposed multi-group scheme.…………..……...…………..161

Fig. 5.8 The frequency slots assigned to the i-th and the j-th group. The reflected optical

power by a grating is denoted as Aov and the two possible partial reflected power

shown in figure are denoted as A|m-j| and A|NR-(m-j)|…………..…...…………..162

Fig. 5.9 The FBGA spectra of the 2-group codes. Note the frequency slots of different

groups are overlapping…………..………..………...…………..162

Fig. 5.10 Received signals at the i-th receiver from the j-th group. (a) Interference in the l-th

transmitter from the m-th group. The used code is denoted as Fl, m (b) Received signal of the desired transmitter, the i-th transmitter from j-th group. The used code is denoted as Fi, j. “bl,m,n” is the earlier or the present bit of the l-th transmitter from the m-th group when n = -1 or 0. represents the relative delay chips between the two inputs………...…………..163

Fig. 5.11 (a) One-bit of all the 24 users are synchronously sent to the decoder of the first

XIX

24 for code lengths of 12, from 25 available un-overlapping frequency slots and 24 simultaneous users. The center shows the auto-correlation peaks and the side lobes are the cross-correlation interference……….…...…………..164

Fig. 5.12 The adjacent non-overlapping Gaussian apodization grating spectra. The

frequency spacing is determined to allow the first nulls of adjacent gratings are coincided to increase the spectra efficiency.………...…...…………..165

Fig. 5.13 (a) BER versus simultaneous users with different group numbers. The number of

frequency slots q and the code weight N are equal to 25 and 12, respectively, and (b)The number of frequency slots q and the code weight N are equal to 17 and 12, respectively…….………...…………..165

Fig. 5.14 BER of systems with parameters (q, N) = (17, 12) and (q, N) = (25,

12). ……….………...…………..166

Fig. 5.15 Block diagram of MC-CDMA, upper part is the transmitter and lower part is the

receiver.………...………...167

Fig. 5.16 Experimental setup of MC-CDMA….………...…………..167 Fig. 5.17 BER curves of different number of active users and corresponding equalized

constellations…...………...…………..168

Fig. 5.18 B E R c u r v e s a n d e q u a l i z e d c o n s t e l l a t i o n s f o r d i f f e r e n t Q A M

mappings………….………...…………..168

List of Tables

Table 4.1The Optimum optical and electrical filters and the 3-dB tolerances to CD and PMD

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List of Acronyms

Acronyms Descriptions

AABN ASE-ASE Beat Noise

ADC Analog to Digital Converter

ASE Accumulated Spontaneous Emission ASK Amplitude Shift Keying

AWG Array Waveguide Grating

BER Bit Error Rate

BERT Bit-Error-Ratio Tester BPF Band-Pass Filter

CD Semiconductor Optical Amplifier CDMA Code Division Multiple Access

CDR Clock and Data Recovery CO-OFDM Coherent Optical OFDM CSPR Carrier to Signal Power Ratio

CW Continuous Wave

DAC Digital to Analog Converter

DCF Dispersion Compensating Fiber DCM Dispersion Compensating Module

DD-MZM Dual Drive MZM

DFB-LD Distributed Feedback Laser Diode DFG Difference Frequency Generation DPSK Differential Phase Shift Keying

DQPSK Differential Quadrature Phase Shift Keying

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DS-CDMA Direct Sequence CDMA DSP Digital Signal Processing

EDFA Erbium-Doped Fiber Amplifier EOM Electric Optical Modulator

ER Extinction Ratio

EVM Error Vector Magnitude

FBG Fiber Bragg Grating

FBGA Fiber Bragg Grating Array

FDL Fiber Delay Line

FEC Forward Error Correction

FFH-CDMA Fast Frequency Hopping CDMA

FFT Fast Fourier Transform

FP-LD Fabry-Pérot Laser Diode FWM Four Wave Mixing

GVSSB-OFDM Generalized Virtual Single Sideband OFDM

IFFT Inverse FFT

KLSE Karhunen-Loeve Series Expansion

LAN Local Access Network

LO Local Oscillator

MAI Multiple Access Interference MAN Metropolitan Area Network MC-CDMA Multi-Carrier CDMA

MGF Moment Generating Function

MLSE Maximum Likelihood Sequence Estimation

MZM Mach-Zehnder Modulator

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OBW Optical Filter Bandwidth OC Optical Circulator

OCDMA Optical CDMA

ODI Optical Delay Interferometer

OFDM Orthogonal Frequency Division Multiplexing

OMI Optical Modulation Index

ONU Optical Network Unit

OOK On Off Keying

OSA Optical Spectrum Analyzer OSNR Optical Signal to Noise Ratio

PBS Polarization Beam Splitter PC Polarization Controller

PDM Polarization Division Multiplexing

PMD Electro-Absorber Modulator

PON Passive Optical Network

PPLN Periodically Poled Lithium Niobate PRBS Pseudo Random Binary Sequence PSD Power Spectra Density

QAM Quadrature Amplitude Modulation

QPM Quasi-Phase Matching

ROF Radio over Fiber

RZ Return to Zero

SABN Signal-ASE Beat Noise

SC Super Continuum

SCM Subcarrier Multiplexing

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SFG Sum Frequency Generation SMSR Side Mode Suppression Ratio

SPM Self-Phase Modulation

SSBI Signal-Signal Beat Interference SSFBG Super-Structured Fiber Bragg Grating

SSMF Standard Single Mode Fiber TDM Time Division Multiplexing VOA Variable Optical Attenuator VSSB-OFDM Virtual Single Sideband OFDM

WDM Wavelength Division Multiplexing

WH Walsh-Hadamard