現今在光纖通訊系統始終是一直在追求更高的電光轉換效率與高速誤碼率反應。但光纖通訊系統因具有色散問題，成為限制光纖通訊傳輸效率與速率的主要因素之一。
本研究以馬克-詹德延遲干涉儀(Mach-Zehnder Interferometer)架構來監測色散。首先以近年來廣泛應用於高速電子元件的絕緣層上覆矽(Silicon-on-insulator)為主，因其具有高折射率係數，可大幅縮小元件體積，同時製作方式與互補式金屬氧化物半導體製程相容，對發展光電積體電路具有極大的潛力。文中所設計的絕緣層上覆矽馬克-詹德延遲干涉儀架構，由兩個2x2多模干涉耦合器(Multimode Interfering Coupler)與延遲100ps的路徑組成，此延遲也等同於10 Gb/s的調變速率所對應之兩光路徑8689.6 m長度差。同時影響延遲干涉儀輸出隔離度(Isolation)特性之主要參數為耦合器分光率及延遲路徑光損耗，利用非對稱2x2多模干涉耦合器，也就是分光率約為66/33做設計時，來補償延遲干涉儀延遲兩路徑光能量不平均之缺陷(延遲路徑光耗損可訂為3dB)，隔離度理想應為無限大；由於光波導蝕刻後幾何形狀呈現為梯形，實際量測非對稱2x2多模干涉耦合器分光率為90/10，又因其光波導實際傳輸損耗為5dB/cm，隔離度測量顯示為2dB，欲以實際量測的波導傳輸損耗來提高馬克-詹德干涉儀之隔離度，2x2多模干涉耦合器分光率應在70/30下為最理想。.
由於前述製程在光波導形狀與光損耗上，所引起不確定因素，使得多模干涉耦合器分光率與延遲干涉儀隔離度未達預期，因而無法監測色散，於是使用極化保持光纖馬克-詹德延遲干涉儀做色散監測系統。極化保持光纖延遲干涉儀可依傳輸速率不同，而使用步進馬達為主的低同調干涉系統來精確控制延遲路徑差。在雷射光源波長為1550nm下，傳輸速率為10 Gb/s，干涉儀延遲時間為100ps時，可提供監測色散範圍達-2000ps/nm，其靈敏度約為4x10-3dB.nm/ps(色散每增加500ps/nm，射頻功率上升2dB)。
一般均以自由光譜範圍(Free Spectral Range)來校正馬克-詹德延遲干涉儀路徑差，而可調光波長雷射(Tunable Laser Source)與光頻譜分析儀(Optical Spectrum Analyzer)光波長解析度通常為0.01-0.02nm，以本論文所探討之10 Gb/s的調變速率即100ps (8689.6 m)延遲路徑差為例，自由光譜範圍可引起0.016nm波長相差，此將產生延遲干涉儀延遲路徑差與實際長度誤差為7.5mm，色散監測之靈敏度則為每增加500ps/nm，射頻功率上升1dB。本研究使用可調干涉式馬克-詹德延遲干涉儀可以精度為0.001mm做微調來平價並有效地提高監測色散之靈敏度。

In recent years, fiber optic communication system is always pursuing the higher efficiency in transfer rate and faster speed response in bit error rate. Because of the dispersion issue in the fiber optic communication system, it becomes one of the main factors that limits the performance on the system’s transfer efficiency and speed response.
The Mach-Zehnder delayed interferometer (MZDI) system was utilized to monitor the chromatic dispersion (CD) in this thesis. The CD monitoring system was first made by the silicon-on-insulator (SOI) platform, which has been developed and demonstrated as high speed electronics and highly optoelectronic integrated circuits (OEIC) due to the large refractive index and its compatibility with the complementary metal oxide semiconductor (CMOS) standard process.
The SOI based MZDI consists of two 2x2 multimode interfering coupler (MIC) and delayed 100-ps optical path between two arms. The optical delay is equal to 8689.6-m physical length difference from 10 Gb/s modulation speed. We can see that the MZDI output optical isolation is mainly affected by the coupling ratio and delay optical path propagation loss. An asymmetric 2x2 MIC was then utilized to get the splitting ratio of 66/33 for the optical loss compensation between two MZDI arms. The output optical isolation should be infinite. Due to the optical waveguide trapezoidal geometry after processing, the experimental data from 2x2 MIC were showing 90/10 splitting ratio and the isolation was only 2dB due to the higher propagation loss of 5 dB/cm on SOI waveguides. To improve the MZDI isolation based on the current SOI waveguide propagation loss, 2x2 MIC splitting ratio should be maintained at 70/30.
Due to the difficulty in the waveguide geometry and optical loss from SOI waveguide processing control, the polarization maintain fiber (PMF) based MZDI was taken as the CD monitor, which delay optical path difference can be precisely controlled by the stepper motor stage in the optical low coherence interferometer. At the wavelength of 1550 nm, the CD monitoring range was up to -2000 ps/nm at 10-Gb/s modulation speed and 100-ps delayed optical path and the sensitivity could achieve 4x10-3dB.nm/ps.
The MZDI path difference was typically calibrated by the free spectral range (FSR). However, the resolution from the tunable laser source and optical spectrum analyzer was normally around 0.01 – 0.02 nm, which will cause 10-Gb/s modulation, which is equal to 8689.6 m delayed optical path, up to 0.016-nm wavelength variation, same as 7.5-mm optical path difference in MZDI. The CD monitoring sensitivity was then degraded, the 500-ps/nm CD increased at the increased 1-dB RF power. The tunable and adjustable MZDI could effectively improve the CD monitoring sensitivity at low cost.

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