針對「使用偏振維持布拉格光柵的微波頻率偏移訊號生成」的討論

Abstract

中文摘要 藉由「偏極光學」課堂中的論文導讀報告，我選定了關於「使用偏振維持布拉格光柵的微波頻率偏移訊號生成」技術進行閱讀學習與報告整理。由於光學技術在大範圍的頻率諧調性上具有較佳的優勢，可用來提升現代無線通訊系統的表現。該論文以開發可用來搭配振幅調變及相位調變的微波頻率偏移(FSK)訊號為目的，為通訊領域提供更加優異的架構可行性。 文中是利用1590.98 nm波長的CW雷射作為訊號源，並在訊號源上載上RF-OOK調變訊號產生雙邊帶抑制載波，再經過PolM，該裝置為一種特殊的偏振調變器，會產生TE和TM兩種互為相反相位調變指數的訊號，之後透過PM-FBG，此為一種在維持原本偏振狀況下，進行特定波長光源反射的元件，將反射後的光再透過光循環器做傳送。而為了與Laser 2進行拍頻，會先透過一個polarizer將還原成原單一模態下傳輸的波形，最後再透過3 dB的光耦合器將調變光及欲做拍頻的光源訊號耦合後，透過PD將光從波長響應轉換至時間/頻率響應的光波，即為FSK訊號。本實驗最後產生載波頻率為9.5/12.5 GHz，傳輸速率為1 Gbps的FSK訊號，且透過BER測試儀及數位示波器觀測眼圖，成功在5 km光纖長度並加上2 m無線光傳輸下有穩定的傳輸品質。

Abstract In the "Polarized Optics" course, I selected the topic of "Microwave Frequency Offset Signal Generation Using Polarization-Maintaining Bragg Gratings" for my paper review report. Optical technology has advantages in a broad range of frequency coherence, which can enhance the performance of modern wireless communication systems. The paper aims to develop a microwave frequency shift keying (FSK) signal that can be used with amplitude modulation and phase modulation, providing a more effective framework for the communication field.

The study uses a continuous-wave (CW) laser with a wavelength of 1590.98 nm as the signal source. An RF-OOK modulation signal is applied to the signal source to generate a double-sideband suppressed carrier. This signal is then passed through a polarization modulator (PolM), which is a special type of polarization modulator that produces signals with TE and TM modes, each with phase modulation indices that are opposites of each other. The modulated signal is then transmitted through a polarization-maintaining fiber Bragg grating (PM-FBG), a device that reflects specific wavelengths while maintaining the original polarization state. The reflected light is sent through an optical circulator.

To perform beat frequency detection with Laser 2, a polarizer is used to restore the signal to its original single-mode state. Finally, a 3 dB optical coupler combines the modulated light with the signal source for beat frequency detection. The light is then converted from wavelength response to time/frequency response using a photodetector (PD), resulting in an FSK signal. The experiment successfully generated an FSK signal with carrier frequencies of 9.5/12.5 GHz and a transmission rate of 1 Gbps. Through BER testing and digital oscilloscope observation of the eye diagram, stable transmission quality was achieved over a 5 km fiber length and 2 meters of wireless optical transmission.