使用並行資料傳輸與分頻多工概念之正交分頻多工技術(OFDM)在光纖通訊系統中可以有效地運用基本頻率以及通道間之正交性提升其傳輸容量，但是此技術在長距離光纖傳輸中面臨光纖色散與訊號失真的問題，因此在本論文中藉由電致光吸收調變器(EAM)整合半導體光放大器(SOA)的飽和特性達到預先補償色散實行於OFDM長距離傳輸。藉由此整合型元件的飽和特性與載子動態行為，經由非線性轉換曲線可以明顯改善波形失真程度。
本實驗中，使用EAM整合SOA之元件長度分別為80 m和570 m來達到預先頻擾補償克服單模光纖色散傳輸正交振幅調變(16-QAM) ，當EAM與SOA偏壓分別操作於2 V與60 mA時，可以得到頻擾參數為-1.4並且成功地達到100公里傳輸，相較於只考慮EAM特性的頻擾約為-0.1，SOA於灌入電流60mA可以有效提升其可使用頻寬為6GHz，且傳輸資料率達到24GB/s，並對不同的傳輸距離皆可以達到相同的效果。
再者，EAM操作於高偏壓時產生之非線性效果可以使用載子間混合干涉技術達到補償非線性特性，但是非線性系統仍然存在編碼相依問題，因此利用EAM與SOA因其相反之載子變化改善錯誤向量振幅(EVM)從-18dB提升至-20.5dB，有效改善非線性特性。

Optical orthogonal frequency-division multiplexing (OFDM) technique has attracted lots of interest for promoting transmission capacity in optical fiber communication due to its usage of low-carrier frequency and orthogonal properties between channels. However, such technique still suffers from the intrinsic dispersion problem in long distance fiber transmission as well as optical waveform distortion.
In this work, a novel pre-chirp scheme has been proposed and demonstrated by employing saturation properties of integration between electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA), compensating the dispersion in the long distance transmission of OFDM signal. Based on the intrinsic mutually reversed polarity in carrier dynamics of integrated devices, the optical transfer function after EAM can be reshaped by saturated SOA, improving optical waveform distortion and thus data transmission.
An 80μm long EAM integrated with 570μm long SOA has been used for testing the pre-chirp and chirp compensation under 16-quadrature amplitude modulation (QAM) format in a standard single mode fiber transmission. A pre-chirp of -1.4 by biasing EAM and SOA with 2V and 60mA has been obtained, leading to successful 100-km transmission. By comparing with EAM chirp (-0.1) transmission, the useful bandwidth of 3GHz (100 km, 16dB of signal-to-noise ratio (SNR) ) can be improved to 6GHz by pumping SOA with 60mA, suggesting pre-chirp properties of EAM-integrated SOA. Also, a distance-insensitive 24-Gbps OFDM (100 km) transmission system is demonstrated.
Moreover, the subcarrier-to-subcarrier intermixing interference (SSII) -based nonlinear compensation is adopted to mitigate the modulation nonlinearity under EAM higher-bias operation, such a nonlinear signal process causes the pattern effect. A distorted waveform by gain saturation of SOA can be corrected to send out a non-distorted optical waveform. An improved error vector magnitude (EVM) of data pattern from -18dB to -20.5dB is obtained by biasing EAM and SOA, confirming pattern waveform enhancement. Therefore, by using saturation behavior of EAM integrated SOA, the pattern effect and the mitigation of nonlinearity distortion have been demonstrated for OFDM modulation format.

Content
Acknowledgements iii
Abstract v
1. Introduction
1.1 Motivation 1
1.2 Fiber dispersion and frequency chirp 5
1.3 Orthogonal Frequency Division Multiplexing (OFDM) 8
1.4 Proposed pre-chirp technique 12
1.5 Organization 15
2. Pre-chirp modulation as the characteristics of material for EAM and SOA
2.1 Chirped Gaussian pulse propagation in optical fibers 16
2.2 Free carrier effects and Kramer-Kronig relations 18
2.3 Optical absorption in a quantum well (QW) EAM 22
2.4 Optical gain in a QW-SOA 29
3. Carrier dynamics and low-pattern-effect signal process
3.1 Pattern effect mitigation for OFDM scheme 35
3.2 Carrier dynamics and pattern effects in EAM 39
3.3 Carrier dynamics and pattern effects in SOA 41
3.4 Low-pattern-effect signal process 44
4. Data transmission system for OFDM modulation format
4.1 Measurements for DC optical characterization 46
4.2 Chirp measurement 49
4.3 Data transmission 51
4.4 Pattern effect analysis 58
5. Conclusion and further work
5.1 Conclusion 66
5.2 Future work 68
References 70

[1] Extreme Networks White Paper: 40 and 100 Gigabit Ethernet Overview.
[2] Brocade White Paper: 40 gigabit and 100 gigabit Ethernet are here
[3] Xing-Zhi Qiu, “Burst-mode receiver technology for short synchronization,” in OFC, 2013, paper OW3G.
[4] Gigopticx: Semiconductor technology for optical interconnection.
[5] Giuseppe Talli, and Paul D. Townsend, “Hybrid DWDM–TDM Long-Reach PON for Next-Generation Optical Access,” J. Lightwave Technol. 24(7), 2827–2834 (2006).
[6] C. H. Yeh, C. W. Chow, H. Y. Chen, and B. W. Chen, “Using adaptive four-band OFDM modulation with 40 Gb/s downstream and 10 Gb/s upstream signals for next generation long-reach PON,” Opt. Express, vol. 19, no. 27, pp. 26150-26160, December, 2011.
[7] Daniel J. F. Barros, and Joseph M. Kahn, “Comparison of Orthogonal Frequency-Division Multiplexing and On-Off Keying in Amplified Direct-Detection Single-Mode Fiber Systems,” J. Lightwave Technol. 28(12), 1811–1820 (2010).
[8] Tiago Alves, and Adolfo Cartaxo,” Distribution of Double-Sideband OFDM-UWB Radio Signals in Dispersion Compensated Long-Reach PONs,” J. Lightwave Technol. 29(16), 2467–2474 (2011).
[9] Peter Ossieur,Cleitus Antony, Alan Naughton, Aisling M. Clarke, Heinz-Georg Krimmel, Xin Yin, Xing-Zhi Qiu, Colin Ford, Anna Borghesani, David Moodie, Alistair Poustie, Richard Wyatt, Bob Harmon, Ian Lealman, Graeme Maxwell, Dave Rogers, David W. Smith, Sylvia Smolorz, Harald Rohde, Derek Nesset, Russell P. Davey, and Paul D. Townsend,”Demonstration of a 32 512 Split, 100 km Reach, 2x3x2 10 Gb/s Hybrid DWDM-TDMA PON Using Tunable External Cavity Lasers in the ONUs,” J. Lightwave Technol. 29(24), 3705–3718 (2011).
[10] Qi Guo, and An Vu Tran, ” Demonstration of 40-Gb/s WDM-PON System Using SOA-REAM and Equalization,” IEEE Photon. Technol. Lett. 24(11), 951–953(2012).
[11] J. Armstrong, “OFDM for optical communications,” J. Lightwave Technol. 27(3), 189–204 (2009).
[12] Giovanni Beninca de Farias, Sylvie Menezo, Badhise Ben Bakir, Antoine Descos, and Edouard Grellier, “12.4-Gb/s Adaptive OFDM Modulation of a Hybrid III/V-on-Silicon Laser Over 50-km SMF-Link,” IEEE Photon. Technol. Lett. 25(19), 1871–1874(2013).
[13] Govind P. Agrawal, and M. J. Potasek, “Effect of frequency chirping on the performance of optical communication systems,” Opt. Letter, vol. 11, no. 5, pp. 318-320, May, 1986.
[14] Naoya Henmi, Tomoki Saito, and Tomoko Ishida, “Prechirp Technique as a Linear Dispersion Compensation for Ultrahigh-Speed Long-Span Intensity Modulation Directed Detection Optical Communication Systems,” J. Lightwave Technol. 12(10), 1706–1719 (1994).
[15] Richard DeSalvo, Arthur G.Wilson, Jeff Rollman, David F. Schneider, Leda M. Lunardi, Stan Lumish, Nitish Agrawal, Andrew H. Steinbach, Ward Baun, Tom Wall, Rafael Ben-Michael, Mark A. Itzler, Alen Fejzuli, Russell A. Chipman, Grant T. Kiehne, and Karl M. Kissa,”Advanced Components and Sub-System Solutions for 40 Gb/s Transmission,” J. Lightwave Technol. 20(12), 2154–2181 (2002).
[16] Toshio Watanabe, Norio Sakaida, Hiroshi Yasaka, Fumiyoshi Kano, and Masafumi Koga, “Transmission Performance of Chirp-Controlled Signal by Using Semiconductor Optical Amplifier,” J. Lightwave Technol. 18(8), 1069–1077 (2000).
[17] Dar-Zu Hsu, Chia-Chien Wei, Hsing-Yu Chen, Jyehong Chen, Maria C. Yuang, Shih-Hsuan Lin, and Wei-Yuan Li, “21 Gb/s after 100 km OFDM long-reach PON transmission using a cost-effective electro-absorption modulator,” Opt. Express, vol. 18, no. 26, pp. 27758-27763, December, 2010.
[18] Bangjiang Lin, Juhao Li, Hui Yang, Yangsha Wan, Yongqi He, and Zhangyuan Chen, “Comparison of DSB and SSB Transmission for OFDM-PON,” J. OPT. COMMUN. NETW, vol. 4, no. 11, November, 2012.
[19] Dar-Zu Hsu, Chia-Chien Wei, Hsing-Yu Chen, Wei-Yuan Li, and Jyehong Chen, “Cost-effective 33-Gbps intensity modulation direct detection multi-band OFDM LR-PON system employing a 10-GHz-based transceiver,” Opt. Express, vol. 19, no. 18, pp. 17546-17556, August, 2011.
[20] Jui-Pin Wu, Wei-Zun Ding, and Yi-Jen Chiu, “Low-Pattern-Dependence Prechirp Optical Modulation by Using Saturation Behaviors of SOA-Integrated EAM,” J. Lightwave Technol. 31(23), 3651–3657 (2013).
[21] Y. J. Chiu, V. Kaman. P. Abraham, S. Z. Zhang and J. E. Bowers, “Low-bias and high saturation-power traveling-wave electroabsorption modulator by using InGaAsP/InGaAsP MQW,” LEOS '00, paper TuX4, 2000.
[22] Maria Morant, Roberto Llorente, Jerome Hauden, Terence Quinlan, Alexandre Mottet, and Stuart Walker, “Dual-drive LiNbO3 interferometric Mach-Zehnder architecture with extended linear regime for high peak-to-average OFDM-based communication systems,” Opt. Express, vol. 19, no. 26, pp. B450-B456, December, 2011.
[23] G. P. Agrawal, “Fiber-optic communication systems,” Third edition.
[24] Sune Højfeldt, and Jesper Mørk, “Modeling of Carrier Dynamics in Quantum-Well Electroabsorption Modulators,” IEEE J. of Sel. Top. in Quantum Electron., vol. 8, no. 6, pp. 1265-1276, Nov./Dec. 2002.
[25] Jeffrey B. Carruthers, and Joseph M. Kahn, “Multiple-subcarrier modulation for nondirected wireless infrared communication,” IEEE J. of Sel. Area in Communication, vol. 14, no. 3, pp. 538-546, April, 1996.
[26] Wei-Ren Peng, Itsuro Morita, Hidenori Takahashi, and Takehiro Tsuritani, “Transmission of High-Speed (>100Gb/s) Direct-Detection Optical OFDM Superchannel,” J. Lightwave Technol. 30(12), 2025–2034 (2012).
[27] Yon-Tae Moon, Jun Woo Jang, Woon-Kyung Choi, and Young-Wan Choi, “Simultaneous noise and distortion reduction of a broadband optical feedforward transmitter for multi-service operation in radio-over-fiber systems,” Opt. Express, vol. 15, no. 19, pp. 12167-12173, September, 2007.
[28] Yiming Shen, Bouchaib Hraimel, Xiupu Zhang, Glenn E. R. Cowan, KeWu, and Taijun Liu,” A Novel Analog Broadband RF Predistortion Circuit to Linearize Electro-Absorption Modulators in Multiband OFDM Radio-Over-Fiber Systems,” IEEE Trans. on Microwave Theory and Technique, vol. 58, no. 11, pp. 3327-3335, November, 2010.
[29] Bouchaib Hraimel and Xiupu Zhang, “Low-Cost Broadband Predistortion-Linearized Single-Drive x-Cut Mach–Zehnder Modulator for Radio-Over-Fiber Systems,” IEEE Photon. Technol. Lett. 24(18), 1571–1573(2012).
[30] Dennis R. Morgan, Zhengxiang Ma, Jaehyeong Kim, Michael G. Zierdt, and John Pastalan, “A Generalized Memory Polynomial Model for Digital Predistortion of RF Power Amplifiers,” IEEE Trans. on Signal Processing, vol. 54, no. 10, pp. 3852-3860, October, 2006.
[31] Lei Ding, G. Tong Zhou, Dennis R. Morgan, Zhengxiang Ma, J. Stevenson Kenney, Jaehyeong Kim, and Charles R. Giardina, “A Robust Digital Baseband Predistorter Constructed Using Memory Polynomials,” IEEE Trans. on Communication, vol. 52, no. 1, pp. 159-165, January, 2004.
[32] Daniel J. Fernandes Barros and Joseph M. Kahn, ”Optical Modulator Optimization for Orthogonal Frequency-Division Multiplexing,” J. Lightwave Technol. 27(13), 2370–2378 (2009).
[33] Prashant P. Baveja, Drew N. Maywar, Aaron M. Kaplan, and Govind P. Agrawal, “Self-Phase Modulation in Semiconductor Optical Amplifiers: Impact of Amplified Spontaneous Emission,” IEEE J. of Quantum Electron., vol. 46, no. 9, pp. 1396-1403, September, 2010.
[34] Dar-Zu Hsu, Chia-Chien Wei, Hsing-Yu Chen, Yi-Cheng Lu, Cih-Yuan Song, Chih-Chieh Yang, and Jyehong Chen, “SSII cancellation in an EAM-based OFDM-IMDD transmission system employing a novel dynamic chirp model,” Opt. Express, vol. 21, no. 1, pp. 533-543, January, 2013.