目前以矽線波導為架構設計出的分波多工器(Wavelength Division Multiplexer, WDM)主要有三種，陣列波導光柵(Arrayed Waveguide Gratings, AWG)、階梯光柵(Echelle Grating)以及馬赫詹德延遲干涉儀(Delayed Mach-Zehnder Interferometer, MZI)。陣列波導光柵儘管製程較為簡單，但是將面臨比其他分波多工器更加嚴峻的相位問題；階梯光柵則較其他元件有更大的損耗問題；相對來說，馬赫詹德延遲干涉儀儘管輸出通道數不易增加和光隔離度表現較差，但是製程簡單以及較容易實現平頂帶寬(Flat Top Passband)的現象，馬赫詹德延遲干涉儀設計分波多工器不僅能夠達到低損耗的需求，且若要應用在長距離傳輸，則可以使用粗分波多工器(Couse Wavelength Division Multiplexing, CWDM)，CWDM與密分波多工器(Dense Wavelength Division Multiplexer, DWDM)的主要區別在於通道間距(Channel Spacing)，CWDM具有更寬的通道間距，且目前業界普遍的通道間距標準為20 nm，然而，若要達到如此寬的通道間距要求，寬頻耦合器便扮演了一個極為重要的角色。
在本論文中，我們以分光比分別為0.5與0.2之馬赫詹德方向耦合器(Mach-Zehnder Directional Coupler, MZDC)和0.05的方向耦合器(Directional Coupler, DC)組合成的三級(Three-stage)晶格濾波器(Lattice Filter)和另一以分光比為0.5與0.3的馬赫-詹德方向耦合器和0.05的方向耦合器組合成的二級(Two-stage)晶格濾波器串接組成一串擾損耗(Crosstalk)可達15 dB，並且工作波段可從1500 nm至1650 nm的串接型濾波器(Cascaded Filter)。同時更進一步討論馬赫-詹德方向耦合器中因彎曲波導結構之耦合相位對於兩個耦合區域分別貢獻高達約20%和30%的相位，因此在設計時須考慮此彎曲相位的影響，避免因彎曲相位導致分光比異常，進而影響寬頻波長濾波器的串擾損耗，理論計算顯示將有5 dB的影響。

There are three kinds of silicon waveguide based wavelength division multiplexer (WDM), such as arrayed waveguide gratings (AWG), echelle gratings and delayed Mach-Zehnder interferometer (DMZI), for optical fiber communications. Although AWG fabrication is relatively simple, the phase error from array waveguides will easily be induced from the process. Compared with AWG and DMZI, echelle grating has relatively higher optical loss. Even though the DMZI output channel count increases with the footprint besides a lack of significant extinction ratio, it is utilized here to demonstrate a flat top passband through easy process. The difference between CWDM and DWDM is the channel spacing, 0.2 nm to 1.2 nm for DWDM and 20 nm for CWDM. In order to achieve CWDM communication, a broadband coupler plays a very important role.
In this thesis, a three-stage lattice filter is composed of Mach-Zehnder directional couplers (MZDC) with splitting ratios of 0.5, 0.2, and 0.2 connected to a directional coupler (DC) ratio of 0.05. Followed by two-stage lattice filter with MZDC ratios of 0.5 and 0.3 connected to a DC ratio of 0.05, the cascaded five stage could demonstrate a wavelength filtering function with 15-dB crosstalk from 1500 nm to 1650 nm in the operating wavelengths. Furthermore, the bend structures of MZDC will contribute significant phase up to 30% and degrade the 5-dB crosstalk of MZDC based optical filter if appropriate compensation is not applied.

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