「光分碼多工處理(OCDMA)技術」是運用於光纖通訊系統架構的一項重要技術，根據不同編碼方法可以多種不同架構達成多工傳輸的效能，其中頻域振幅編碼多工(SAC-OCDMA)是最適於傳輸訊息的技術，其具有架構簡單、保密性、不需考慮同步問題等優點，且解碼端使用的平衡檢測器(BPD)，在理想狀態下，可以有效抑制多重擷取干擾（MAI）。 然而，光纖的色度色散(Chromatic Dispersion)使得各波長於光纖中行徑速度不同，因此造成各波長無法同時到達接收端之平衡檢測器，導致多重擷取干擾無法抑制，而嚴重影響系統效能。為了解決此問題，在這篇論文中，我們將提出一種由馬赫-曾德爾干涉儀(Mach–Zehnder interferometer, MZI)串聯而成的色散斜率補償器，以補償色散造成的損失。此種馬赫-曾德爾干涉儀架構於矽質平面光波導(PLC)，故其具體積小且色散值較具彈性等優點，當使用之傳輸光纖種類及距離不同時，造成的色散曲線斜率亦將不同，僅需針對各使用中心波長設計不同之干涉儀臂長(光程差)，使補償器與光纖產生之色散曲線斜率互補，即可做較高正確性之補償。此外，此種干涉儀架構之色散斜率補償器相位易控制且其傳輸注入損失小。本論文中，即針對先前提出之頻域振幅編碼多工系統，依照所使用之各中心波長，分別設計兩組參數以補償傳輸距離為十公里、二十公里單模光纖系統，並藉由訊號載波干擾比（SIR）觀察系統效能。由色散斜率補償器各串產生之相對延遲時間曲線可驗證其與光纖色散正好為互補之斜率，因此，色散對光訊號的干擾可由適當設計之補償器補償。於論文最末並分析補償前後之系統效能，由訊號載波干擾比及使用者人數曲線可觀察出，經補償後之系統，其多重擷取干擾可順利由平衡檢測技術抑制，其系統效能亦將大幅提升。

Spectra-amplitude-coding Optical Code-Division Multiple-Access (SAC-OCDMA) is the most appropriate way for signal transmitting because it is uncomplicated and the information data can be regenerated without any synchronization. Besides, the decoder applies balance detection to suppress the multiple-access interference (MAI). However, chromatic dispersion from optical fiber produces temporal skews and destroys the rectangular structure of code patterns in the SAC-OCDMA system. Thus, the balance detection doesn’t work and the system performance will be degraded.
To improve the system performance, dispersion optical equalizers are needed. In this study, we apply cascaded Mach–Zehnder interferometers (MZIs) to design a dispersion slope equalizer for the SAC-OCDMA system. The dispersion slope of cascaded MZIs compensator based on silica-based planar lightwave circuit (PLC) could be adjusted by the arm length differences of MZIs and be complementary with the fiber links.
We present two sets of MZI length differences for 10 km-long and 20 km-long single-mode fibers and verify the compensation skill by relative delay time slope and signal-to-interference ratio (SIR). The dispersion slope equalizer with perfect complementary slope successfully compensates the dispersion from single-mode fibers and the system performance with dispersion slope equalizer is highly improved.

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