無源光網絡（PON）成為當今接取網路的首要架構。由於被動光網路架構僅在光線路終端（OLT）及用戶端光網絡單元（ONU）使用到主動元件，在兩端中間的傳輸線路中完全使用被動式光元件。因此，他們不僅提供高品質和寬帶服務，同時也避免了對維護和網絡建設的許多問題。 然而，也正因為上述PON的特性，被動式光纖分支的架構或是局端傳輸設備的好與壞，皆會影響著此網路系統的傳輸效能。因此對於電信業者而言，如何有效的即時監控PON以及同時具備保護裝置乃為實現PON系統的重要考量。同理，對於WDM-PON系統進行大容量的數據到多個用戶，信號通道故障監測確保系統的可靠性至關重要。可調光時域反射儀（OTDR）可用於檢測光纖線路之斷裂。放大自發輻射（ASE）源或其它多波長光源也可以在WDM-PON的通道故障監測系統中提供監控信號。通常在ONU端加入各種元件如光纖光柵(Fiber Bragg Grating, FBG)或者鏡面(Mirror)以改變其反射量，以便於監測其反射信號。 在本篇論文中，我們將提出並驗證一使用FP-LD做為調變式反射器和光接收器來設計用於WDM-PON之故障監測單元，監測光纖路徑與用戶端設備之工作情形。 Passive optical networks (PONs) nowadays become significant architectures of access networks. As a low-cost and wideband network scheme, PONs are composed of passive components in the networks, but only optical line terminal (OLT) and optical network unit(ONU) are active apparatuses. So they not only provide a service with high quality and wideband, but also avoid many problems on the maintenance and construction in the networks.
However, these characteristics of PONs also make defect. It is easy to affect the performance of the network transmission system by the branching structure on fiber or the quality of central office transmission equipment. For operators, to achieve PON systems, it is important to monitor in real-time and to have a protective scheme. Similarly, for a wavelength-division-multiplexed PON (WDM-PON) system carrying high-capacity data to many users, channel fault monitoring is essential for ensuring the system reliability.Tunable optical time-domain reflectometers can be used to detect fiber breaks in both the feeder and distribution fibers. An amplified spontaneous emission source or other multi-wavelength light sources can also be used to provide the monitoring signal for channel fault monitoring in a WDM-PON system. In addition, a fiber Bragg grating or a mirror can be designed in the ONU to carry out the channel fault monitoring.
In this thesis, the proposed optical monitoring unit based on a single low-cost coaxial-type FP-LD as a dithered reflector and a photo-receiver has been demonstrated in a simple WDM-PON architecture. It is very suitable for monitoring the status of fiber paths and ONUs.
