- 學位論文
混合式極化/光分碼多工於無線光通訊之研究
The Investigation of Hybrid PDM/OCDMA in Wireless Optical Communication
摘要
本研究採用一種基於頻譜振幅編碼之光分碼多重擷取(Spectral Amplitude Coding Optical Code Division Multiple Access, SAC OCDMA)的架構，並加入了極化多工(Polarization Division Multiplexing, PDM )的方式完成無線光通訊系統。使用者的編碼器與解碼器皆由光纖布拉格光柵完成，在使用者(User)的編碼配置完成後，讓兩個使用者利用電光調變器(Electro-Optics Modulator, EOM)分別加入不同的類比/數位訊號，在自由空間(Free Space)中同時傳送訊號，並共用同一組路徑進行傳輸。實驗證實該架構能正確的將使用者編碼字串，在自由空間中利用極化多工的方式完成共路徑無線傳輸，使用者加入的類比訊號能正確地被本系統的解碼器解調出正確的頻率，而數位訊號與類比訊號同時傳送時，解碼器也能正確地顯示數位訊號的眼圖，與類比訊號的頻率，並不會互相影響。本研究的自由空間架構在一般常溫空氣介質下傳輸，該架構能將使用者訊號分成水平極化狀態(0°，180°)與垂直極化狀態(90°，270°) ，並傳送到與使用者的極化狀態相匹配的水平端解碼器或垂直端解碼器。在本研究中，加入極化多工的方式，即使使用者的編碼字串重複也不會互相干擾，因此解碼端可以不受多個使用者所產生的多重擷取干擾(Multiple Access Interference，MAI)影響，這讓使用者訊號在進行解調時會有清晰的訊號頻率，此優點可以讓我們在編碼時有更靈活的配置與運用。
並列摘要
This research adopts a structure of Spectral Amplitude Coding Optical Code Division Multiple Access(SAC OCDMA)combined with Polarization Division Multiplexing (PDM) to complete wireless optical communication system. The encoder and decoder of User are both completed by Fiber Bragg Grating. After the coding configuration of User is completed, let the two users to add different analog /digital signal through Electro-Optics Modulator (EOM), thus simultaneously sending signal in Free Space and conducting the transmission through the same route. The experiment verifies that this structure could correctly complete common-route wireless transmission of users’ coded string through the method of Polarization Division Multiplexing. The analog signal added by User could be demodulated the correct frequency by the decoder of this system, while during the simultaneous transmission of digital signal and analog signal, the decoder could display the correct eye pattern of digital signal and frequency of analog signal and they would not influence each other. The Free Space Structure is transferred under the air medium in ordinary normal temperature, and this structure could divide the user signal into horizontal polarization state (0°，180°) and vertical polarization state (90°，270°) , and would send them to the horizontal side decoder and vertical side decoder that match with the polarized state of user. In this research, the method of Polarization Division Multiplexing is added, even the coded string of user is repeated, they would not interfere with each other, hence, the decoder side would not be influenced by(Multiple Access Interference (MAI) of multiple users, thus the user signal could have a clear signal frequency during the demodulation. This advantage could let us have a more flexible configuration and application during the encoding.