QAM調製方法由於其高系統帶寬效率，強大的抗噪能力和有效的數位數據傳輸的優勢，已在當代的光纖通訊系統中被廣泛採用，尤其是在DSL（digital subscriber line）和cable modem中，但為了要滿足日益增長的傳輸帶寬需求，所以便提出了一種使用雙極化(dual-polarization, DP)QAM調製方案的新型同調光纖通訊。將改進的雙極化方法添加到QAM系統中，而提出的DP-QAM(dual-polarization quadrature amplitude modulation)系統具有比傳統QAM系統更好的頻譜效率的同時還可以一定程度的防止光纖中的線性與非線性影響，並增加傳統QAM系統的帶寬和效率。本論文採用OptiSystem光纖模擬程序，實現了一個同調的DP-QAM光纖通信系統的體系結構，並對其進行了適當的分析。在不同的操作和傳輸條件下，對性能參數BER(bit error rate)和EVM(error vector magnitude)以及星座圖(constellation)進行了分析和介紹，以驗證同調DP-QAM光纖通信系統的優勢。

A novel, coherent optical fiber communication using the dual-polarization QAM modulation scheme is proposed to meet the increasing demand for transmission bandwidth. The QAM modulation scheme has been widely adopted in contemporary, optical fiber commutation systems, especially in DSL (digital subscriber line) and cable modem, due to its advantages of high system bandwidth, strong anti-noise ability, and effective digital data transmission. Based on this commonly adopted QAM system, a modified DP method is added to the QAM system to increase the bandwidth and efficiency of the traditional QAM system. The proposed DP-QAM system has better spectral efficiency and higher capacity whereas it also shields against linear and nonlinear effects in optical fibers. In this thesis, the architecture of a coherent, DP-QAM optical fiber communications system is implemented and properly analyzed by the OptiSystem simulation program. The performance parameters, BER and EVM, are analyzed and presented under different operation and transmission conditions to validate the advantages of the coherent, DP-QAM optical fiber communication system.

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