本論文主要目的在量測行波式電致吸收光調變器(Traveling-wave electroabsorption modulator,TW-EAM)的電-光響應(E-O response)，我們採用行波式電致吸收光調變器的原因，主要是其在相同的速度需求下，能傳遞於較長的元件，且具有較低驅動電壓、提升消光比(extinction ratio)和光飽和功率的優點，此元件的最大特點為可操作在高速，因此如何準確的做好高速的元件特性量測，為本論文的最重要課題。

在正式量測電-光響應之前，我們必須先了解在TW-EAM元件中微波是如何傳遞，以及微波的特性為何，所以我們先做了一個純微波(E-E response)的量測，利用網路分析儀量測元件的散射參數(S-parameter)，藉以得知微波傳遞於元件中的反射傳輸等特性，在了解微波的特性後，也必須知道光傳遞於元件中的特性，我們必須先量測直流傳輸曲線(DC transmission curve)，改變不同偏壓去探討DC power的transmission 狀況，這些實驗都是正式量測電-光響應之前必備的。

接者我們可以正式的進行電-光響應的量測，我們會採用縮腰式蝕刻(Undercut-etching)的波導結構來和傳統的脊狀(Ridge)波導結構作比較，使用模擬分析和實際量測同時去探討這2種結構的特性優劣，同時加入電和光的訊號至光調變器中，使用交流電訊號調變輸入的光。由於TW-EAM的終端可能會有反射現象的產生，所以必須加入一個負載阻抗，進而造成傳輸線阻抗匹配無反射的特性，以此消弭TW-EAM的終端反射現象，在我們的實驗中也會將有無加入負載的狀況加以比較，最後，我們還會用光調變器架構一光纖系統，量測其眼圖(Eye diagram)和位元誤碼率(Bit error rate)藉以得知此光纖網路系統的可用性。

This paper is to present the measurement of high-speed traveling-wave electroabsorption modulator (TW-EAM). A traveling-wave electrode structure can overcome RC limitation and allows longer device for the high-speed performance. Low driving voltage, high extinction ratio and high optical saturation power can thus be obtained. Two structures of TW-EAMs are taken as examples, namely ridge- (ri-) and undercut-etching-active (un-) types. The topic of this work includes all the electrical, optical and electrical-to-optical measurement for the characterization of TW-EAM.

The characterization on EAM is divided by three steps : electrical-to-electrical, optical-to-optical and electrical-to-optical measurement. Firstly, by using a 40GHz vector network analyzer, the microwave-propagation loss and reflection loss are extracted from scattering-parameters (S-parameters). Secondly, the optical propagation loss in waveguide is obtained by comparing the optical transmission of different lengths of EAMs. Finally, the electrical-to-optical response is obtained by transferring the high-speed-modulated optical signal to electrical signal by a high-speed photodetector. It has been shown that the un-TW-EAM can have advantages over the ri- types due to the lower microwave and optical propagation loss.

目錄

1. 序論.................................................1
1.1 直接調變和外部調變 1
1.2 電致吸收效應 2
1.3 集總式電致吸收光調變器和行波式電致吸收光調變器 2
1.4 論文架構 6
2. 網路分析儀校正方法及其原理..........................7
3. 傳輸線介紹及行波式電極模擬分析....................... 17
3.1傳輸線結構 17
3.2混合式共平面波導 19
3.3行波式模型電極結構模擬 20
4. 電致吸收光調變器特性的量測技巧與實驗設置............. 25
4.1光對光傳輸特性 26
4.2電對電微波傳輸特性 33
4.2.1長直波導型光調變器微波特性 34
4.2.2共平面波導型光調變器微波特性
4.3 電對光傳輸特性 45
4.4 縮腰式蝕刻波導結構和脊狀波導結構之電光響應比較 47

5. 傳輸實驗............................................. 53
5.1眼圖量測 53
5.2位元誤碼率量測 56
6. 結論和未來改善方向................................... 57
6.1 結論 57
6.2 未來改善方向 57

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