光時域技術在被動光纖環狀網路上的偵測應用

Abstract

被動光纖環狀網路可以被應用在人口密集的都會網路上，它的網路效能是一個重要的議題，若能找到適當的監控方法，對於網路效能的管理會有很大的幫助。在被動光纖環狀網路中，所有的光主動元件都在中心節點上，因此設計一個具有監控功能的中心節點對於被動光纖環狀網路效能的維持是需要的。 在光效能偵測上有許多的項目可以達到監控的功能，在這篇論文，我們著重在光放大器控制以及光纖狀況的診斷。在此我們提出光時域技術的使用，因為光時域技術具有一個相當特別的優點—它能夠找出所想要偵測的參數或事件在光纖中發生的位置。我們研究兩種光時域技術—拉曼增益光時域分析技術和光時域反射儀技術。我們用實驗個別去證明這兩種技術在偵測光纖拉曼增益參數以及光纖損毀或斷裂偵測上的可行性，另一部分我們將這兩種光時域技術整合在一個被動光纖環狀網路的中心節點上並且利用共用元件的方式達到低成本的設計。 我們的設計分為兩部分，其一，在長距離的被動光纖環狀網路中，我們使用光纖拉曼放大器放大光信號已達到長距離的傳輸，並使用拉曼增益光時域分析技術去測量在被動光纖環狀網路中光纖拉曼增益參數的分佈，藉此控制光纖拉曼放大器的操作已達到光效能偵測中光放大器控制的功能。其二，我們使用光時域反射儀技術去偵測在被動光纖環狀網路中光纖正常或損毀的情形，藉此操作達到光效能偵測中光纖健康狀況診斷的功能。

The passive optical ring (POR) networks can be applied to metropolitan-area networks (MANs) in densely populated cities. Their performance is an important issue. Finding the suitable monitoring methods would help the management of POR networks. In POR networks, all active optical components are located in the central node, therefore, the design of a central node with monitoring functions is necessary. Many network parameters provide indications for performance monitoring. In this work, we focus on the optical amplifier control and fiber health diagnostic. We propose the optical time-domain techniques for monitoring. The reason of adopting time-domain techniques is because their can locate the parameters and events in the fibers. We investigated two optical time-domain techniques – Raman gain optical time-domain analysis (ROTDA) and optical time-domain reflectometer (OTDR). We perform experiment to prove that these two techniques can monitor Raman gain efficiency and fiber fault. In addition we combine these two optical time-domain techniques in a central node for POR networks and achieve low-cost design by component sharing between the two techniques. In long distance POR networks, we use fiber Raman amplifier (FRA) to enhance the performance. The ROTDA can measure the Raman gain efficiency distribution in order to determine the best operating conditions of FRA. This is an example of the “optical amplifier control” monitoring function mentioned above. We use OTDR to monitor fiber conditions in POR networks. This is an example of “fiber health diagnostic” monitoring function.