| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系所 === 95 === The purpose of this thesis is to improve the traditional passive optical network structure including the passive optical network and fault detecting technology. The traditional tree topology is unable to survive and discriminate the fault location immediately once the optical path encounters a mistake while transmitting. Therefore, we utilize optical switch to switch over two routes P1 and P2 which are normal feeder fiber P1 and protecting fiber P2. Signal pass P1 and P2 and through 2X2 coupler, splitter, and 2X1 coupler into the drop fiber. Finally pass through WDM coupler and filter into ONU. The upstream signal is also transmitted in the same way. We can also utilize optical switch to switch over two routes P3 and P4 to monitor the feeder fiber and drop fiber, respectively.
We have done the following experiment of improved passive optical network structure: (1) we compare the difference of the received optical power and optical spectrum of improved and traditional passive optical network structure. The optical power from our improved passive optical network structure is reduced because of the additional couplers loss (2X2 coupler and 2X1 coupler) and connector loss but the reduction is in our acceptance. Thus, the improved passive optical network can still provide the structure for fault detecting. (2) We use OTDR to monitor the fault locations which are feeder fiber bending, or connector of drop fiber loosing, or optical passive component failure. The received optical power, eye diagram, and optical spectrum are showing the fault occurrence. OTDR traces are indicating the fault locations. The results of our experiment tell the fault locations accurately which provide the functions of monitoring and restoring. Our improved passive optical network structure not only has the survival ability which is lack in the traditional passive optical network but also benefit from the loss reduction resulting from the break or bending of the optical path.
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