伴隨著科技的日益發達，人們漸漸對網路的需求越來越增加，轉眼間第四代通訊規格的網路規格量快要應付不了未來的網路量，因此人們開始探討第五代行動通訊的開發。在本論文中提出一個基於直接檢測光學正交分頻多工(DDO-OFDM)的架構，並透過偏振態多工(PDM)以及一組正交偏振態載波載上中頻訊號(IF)來成功達到偏振態無感(Polarization-insensitive)的上傳機制。在實驗過程中我們將先示範單一使用者傳送於25km單模光纖中(SMF)，再透過示範不同情境下的偏振態依舊都能將訊號解調回來，藉此證明偏振態無感確實存在。並在後續的實驗中，我們將訊號增加到多個使用者而接收端依舊維持單一接收者的情況下，成功解調出訊號，證明此系統在多使用者的情境下依舊穩定。
透過這樣的上傳機制概念，由於達到了偏振態無感的機制，不僅降低了整體系統的複雜度使成本降低，另外透過OFDM的應用，使得資料傳輸量提升，更加使得系統符合5G的規格，讓此系統有機會應用於5G世代中，提升未來人們可用的網路使用量。

Due to the technology’s large improvement, people’s demand for the internet has increased significantly. In the blink of an eye, Fourth Generation Mobile Communication (4G) can’t afford future network’s specification anymore. Therefore, people began to explore the Fifth Generation Mobile Communication (5G). In this thesis, we propose an architecture based on direct detection optical orthogonal frequency division multiplexing (DDO-OFDM), which is based on polarization state multiplex (PDM) and a set of orthogonal optical carriers with intermediate frequency signal (IF) to achieved a polarization-insensitive uplink system. In the experiment result, we will first demonstrate a single user in polarization-insensitive uplink system and transmit to 25km single-mode fiber (SMF) with different polarization state, to show that even every time the polarization is different, we can still demodulate the signal with a stable performance. After the single user, we will increase the transmitter from single user to multi-user, but with only one receiver, to show that polarization-insensitive uplink system is still work in this scenario.
With this kind of mechanism, we can not only reduce the complexity of the system, but also reduce the cost. In addition, we use OFDM as our modulation format to increase our data capacity, which makes our system more conform to 5g's standard, and more available to people nowadays.

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