光纖系統監控及效能改進技術

Abstract

在本論文中，我們提出並驗證三種新穎的技術，適用於光效能監控以及系統的線性化。第一個方法是使用非對稱”馬赫□詹德光濾波器”來做色散監控，適用於高速數位傳輸系統（>40 Gb/s）。另外，無論發射機是否加入導頻載波，或是帶有頻擾（由馬赫-詹德光調變器有限的消光比或是由光纖自我相位調變所造成），這個方法皆能正常工作。第二個提出的方法可用在RZ-DPSK系統中，脈衝產生器和相位調變器間的自動時序調整。主要是利用光學頻率鑑別器來偵測因為時序誤差所造成的光頻譜增寬效應。相較於已知的技術，使用這種方式可以得到較佳的偵測動態範圍，同時不受光極化性質的影響。最後一個方法是使用外調式光發射機的有線電視系統之線性化技術。這個方法同時能夠抑制在傳輸系統上所產生的非線性失真，也可以提高接收端的載波雜訊比。

In this dissertation, we propose and demonstrate three novel techniques for optical performance monitoring (OPM) and impairment mitigation. The first one is proposed for dispersion monitoring at 40 Gb/s or beyond, and it is a novel post-detection method based on an optical delay-and-add filter (DAF). The proposed method can be used with or without a pilot tone, and works well even when there exists a residual chirp due to the finite DC extinction ratio of a Mach Zehnder (MZ) modulator or self-phase modulation (SPM). The second technique is proposed and demonstrated for monitoring the timing alignment between a pulse carver and a phase modulator in RZ differential phase shift keying (RZ-DPSK) systems. An optical frequency discriminator is used to monitor the spectrum broadening caused by timing misalignment. After photo-detection, microwave bandpass filtering and envelope detection, a correct timing is achieved by minimizing the detected microwave power. This proposed method has a large detection dynamic range and is polarization independent. Finally, a novel linearization technique is proposed and demonstrated for cable TV (CATV) external-modulated systems, and it can simultaneously suppress the nonlinear distortions (NLDs) generated in a transmission system and increase the received carrier-to-noise ratio (CNR). This technique is based on offsetting the bias voltage of MZ modulator from its inflection point. Both analytical and experimental results are presented.