隨著網路傳輸需求量大幅度上升，資料中心的資訊容量需求也跟著上升，為此建立一個低成本、高傳輸量的通訊系統成了當務之急。
光學四階脈衝振幅調變格式是一種可行的方法，其傳輸量為二進制訊號的兩倍，可以提高訊號頻譜效益，然而當四階脈衝振幅調變訊號在高速傳輸時，因為色散現象限制傳輸的距離，本論文我們將四階脈衝振幅調變格式編碼為雙二進制四階脈衝振幅調變格式，此種低成本、低複雜度的編碼方式將訊號頻寬需求降低一半，藉此提升系統色散容忍力、傳輸距離，此外在本論文我們分析光調變器線性度進行系統訊號雜訊比之優化，藉此找到一種最節省成本、最有效益的通訊系統。

As the increase of the growing demand for network transmission, it requires huge data capacity in data centers. It is necessary that establishing a communication system with lower cost and higher capacity.
Optical 4-ary pulse amplitude modulation format(PAM4) is a feasible method. Relative to binary signal, PAM4 can double the data rate and offers higher spectral efficiency. However, when PAM4 in the high-speed transmission, the dispersion limits the transmission distance of signal.
In the thesis, we transform the PAM4 format into Duobinary PAM4 format. This low cost and low-complexity encoding reduces the requirement of the signal by half, increasing the dispersion tolerance and transmission distance. In addition, we analyze the linearity of the optical modulator to optimize the signal-to-noise ratio(SNR) of the system. We find a most cost-effective and most efficient communication system.

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