為提升單一光纖的傳輸頻寬，未來將建立以波長分工（Wave-Division Multiplexing，WDM）為基礎的全光學網路，而大型光學開關為其中最重要的元件之一，它的功能在於將一輸入埠（Port）的訊號切換導引至數千個輸出埠中任一個，最新的研究趨勢朝向以微機電（MEMS）技術製作光學鏡面，以鏡面直接反射光的方式作為訊號的導引，並控制角度以切換導引（Switching）至輸出位置，此方式光－光－光（O-O-O）轉換取代傳統光－電－光（O-E-O）的傳輸模式，目標在達到節降低耗能及設備成本。
在此應用中的光學鏡面必須達到三維的大角度轉動，期望減少光在空氣中傳輸的損耗，在本研究計畫選擇以電壓迴授的閉迴路方式，來對大型光學開關中的三維微鏡面做大角度且穩定的轉動控制，除了擴大光訊號引導的角度與位置外，穩定控制的鏡面亦達到較低的光損耗。基於減少佈局面積、操作耗能和製程難易的考量，過去多數的大型光學開關的研究均採取平行板作為致動的方式，並以靜電式開路驅動作為鏡面的驅動，此次的閉迴路除了沿用平行板的驅動方式，並經由電容式感測器作為位置的量測，另外加入了迴授控制能克服制動器在驅動時的非線性以及不穩定性，期望將平行板靜電驅動由三分之一初始間距的不穩定點往後延伸，增加轉動角度，文獻中亦提到以電荷控制的特殊方式來增加轉動角度，但其控制電路必須克服漏電流及電荷注入（Charge injection）以確保長期操作的穩定性，由於外界的擾動或雜訊會引起鏡面的角度變化，而造成光訊號的損耗，故迴授控制亦可用於抑制干擾。
而電壓迴授控制系統的設計構想上，將加入一個線性控制器和一個位置感測器，包含原本的致動器形成閉迴路系統，其中控制器用於延伸致動器的不穩定點，以增強系統穩定的強韌性，位置感測器則是用於控制器之前、致動器之後，將鏡面移動瞬態反應的訊號讀出；而製程方面則採用互補式金氧半微機電（CMOS MEMS）製程已為平台，將電路和結構整合在單一晶片之上，此整合方案除了將電容感測器最常遭遇到的寄生電容效應降至最小外，更期望將來以最低的成本可以大量製造，加速全光學網路的早日誕生。
　　本論文包含致動器、感測器與伺服控制器的分析與模擬，以及溼蝕刻、乾蝕刻兩步後製程的實驗，和釋放結構後的量測與驗證。

In order to deliver extremely high bandwidth in a single fiber, the vision for future optical communication is to build a WDM-based all-optical network, in which the large-scale optical switches are the most important constituent elements. In essence, a large-scale optical switch can handle network traffic of thousands of input/output ports, allowing any input signal to be routed to the desired output port. Micro-mirrors realized by MEMS technology are intended to replace the conventional optical-electrical-optical conversion by routing light signals using direct reflection. The purpose is to reduce the required power and overall cost.
In order to reduce the transmitting light path and the signal insertion loss in this large-scale optical switching application, the 3D-rotating angle of each micro-mirror has to be increased. In this design, we choose closed-loop control to realize a stable large rotation for the 3D micro-mirrors. Based on issues such as design area, power consumption and ease of fabrication, most research efforts on large-scale optical switches adopt open-loop parallel-plate electrostatic actuation. We expect to use feedback control to extend the travelled range of a parallel-plate actuator beyond one-third of the initial gap. Extended travelled range by charge control has been reported to overcome the pull-in limit. However this method has to use complex circuit to overcome leakage current and charge injection without guaranteed long-term stability. The applied closed-loop control can also perform sensitivity in face of external disturbance reduction.
A linear controller and a position sensor are used in the closed-loop system. The controller is used to stabilize the extended position beyond the pull-in, and a capacitive sensor is used to detect the position. The fabrication of the mirror is based on the CMOS-MEMS process in order to minimize signal attenuation due to the parasitic capacitance.
This theses includes the analysis and simulation of the actuator、the sensor and the servo-controller. The measurements of wet etching and dry etching, posting the CMOS process, verify the released structures.

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