由於科技日新月異，人類對於資訊的需求量增加，通訊網路的需求也越來越高。近年來，由於光纖的高傳送速度，加上光放大器和光調變器的發達，光纖通訊系統開始發展起來，為了在相同成本下能增加傳送速度，大家開始對傳送端的的資料作訊號處理，希望在相同情況下能得到最好的結果，就目前的通訊系統上，以光的正交分頻多工系統為最新的架構，此架構利用複利葉轉換，將原本訊號載到多個正交載波上作處理，架構上只需用晶片即可達成，系統複雜度和整合上可以減化。此外，由於正交載波的特性，訊號可成功抵抗光纖中色散的問題，在遠距離的傳輸上，只要在光纖一定的距離放一個光放大器，即可使訊號傳達到各用作，由於不用在光纖中作色散補償的動作，系統的成本上可大幅降低，在實作上也較為可行，以最近的實驗結果可知，傳送速度為25.6Gbps下，在單模光纖中成功傳達4160公里。
由於訊號經光調變器調變後，和訊號功率相比，會有較高的載波功率，傳送訊號時會造成功率上的損失，為了改善此結果，本論文提出調整光調變器的偏壓點，抑制載波功率，不論在任何調變深度下，都可找出最佳的偏壓點，使調變後訊號和載波功率比為一比一，在直接偵測的情況下，能有最佳結果。
此外，在直接偵測的情況下，接收後的訊號受雜訊影響較大，接收時受載波功率影響較明顯，在同調偵測的情況下，訊號會有雷射線寬的問題，傳送端和接收端的射雷又有相位同步的問題，實作上需加上鎖相迴路才能解決，實驗上較為困難，基於上述原因，本論文提出新的接收端架構，對於以上兩點作改善，使系統有更好的結果。

[1] Richard van Nee and Ramhee Prasad, OFDM Wireless Multimedia Communication, (Artech House, Boston/London, 1999)
[2] H. Schulze and C.Luders, Theory and Applications of OFDM and CDMA, (John Wiley & Sons, Ltd, 2005)
[3] A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems”Opt. Express, 14, pp. 2079-2084, 2006
[4] A. J. Lowery and J. Armstrong, “Adapation of Orthogonal Frequency Division Multiplexing to Compensate Impairments in Optical Transmission Systems”, ECOC Tutorial: Berlin 2007
[5] A. J. Lowery, L. B. Du, and J. Armstrong, “Performance of Optical OFDM in Ultralong-Haul WDM Lightwave Systems”, Journal of Lightwave Technology, vol 25, NO. 1, January 2007
[6] W. Shieh, H. Bao, and Y. Tang”Coherent optical OFDM: theory and design”, Optical Society of America, 2008
[7] W. Shieh and C.Athaudage,“Coherent Optical Orthogonal Frequency Division Multiplexing,”IEE Electron. Lett., vol. 42, No. 10, May, 2006
[8] I. B. Djordjevic and B. Vasic,“Orthogonal Frequency Division Multiplexing for high-speed optical transmission,” Opt. Express, 14, pp. 3767-3775, 2006.
[9] D. Chanda, A. B. Sesay and B. Davids,“Performance of clipped OFDM signals in fiber”Proc. IEEE Candian Conference on Electrical and Computer Engineering 4, pp. 2401-2404, 2004
[10]M. Sieben, J. Conradi, and D. E. Dodds,”Optical Single Sideband Transmission at 10Gb/s Using Only Electrical Dispersion Compensation”, Journal of Lightwave Technology, vol 17, NO.10, October 1999
[11]R. I. Killey, P. M. Watts, V. Mikhailov, M. Glich, and P. Bayvel,”Electronic Dispersion Compensation by Signal Predistortion Using Digital Processing and a Dual-Drive Mach-Zehnder Modulator”, IEEE Photonic technology Letters, vol 17, NO. 3, March 2005
[12]B. J. C. Schmidt, A. J. Lowery, and J. Armstrong,”Experimental Dispersion Compensation for Long-Haul Transmission Using Direct-Detection Optical OFDM”,Journal of Lightwave Technology, Vol. 26, NO. 1, January 1, 2008
[13]A. J. Lowery,”Amplified-spontaneous noise limit of optical OFDM lightwave systems”, Optical Society of America, 2008
[14]K-Po Ho,”Phase-Modulated Optical Communication Systems”,(Springer Science and Business Media, 2005)
[15]G. P. Agrawal “Nonlinear Fiber Optics”, Third Edition, 2001, 1995 by Academic Press, San Diego San Francisco New York Boston London Sydney Tokyo
[16]R. Hiu, B. Zhu, R. Huang, C. T. Allen, K. R. Demarest, and D. Richards,”Subcarrier Multiplexing for High Speed Optical Transmission”,Journal of Lightwave Technology, Vol. 20, NO. 3, March 2002
[17]L. Xu, J. Hu, D. Qain,and T. Wang,”Coherent Optical OFDM Systems Using Self Optical Carrier Extraction”, OMU4, OFC/NFOEC 2008

[18]A. J. Lowery,”Improving Sensitivity and Spectral Efficiency in Direct-Detection Optical OFDM System”, OMM4, OFC/NFOEC 2008
[19]X. Yi, W. Shieh, and Y. Tang,”Phase Estimation for Coherent Optical OFDM Transmission”,COIN-ACOFT,24-27, July 2007