| 摘要 |
Disclosed is a system for accessing a wavelength-division-multiplexed ("WDM"), bidirectional optical fiber ring network having first and second network fibers for carrying WDM signals in opposite directions. The system comprises a network node intersecting the first and second fibers of the ring network. The network node is coupled to a network access station through a single pair of access fibers, the network access station having a single array of receiving elements and a single array of transmitting elements. The network node has two wavelength add drop multiplexers ("WADMs") each having a first input, a second input, a first output and a second output, and being individually setable to a bar or cross state for each one of the wavelengths on the ring network. The first WADM has its first input coupled to one of the access fibers for carrying signals provided by the array of transmitting elements, its second input coupled to the first network fiber entering the network node, its first output coupled to the first input of the second WADM, and its second output coupled to the first network fiber leaving the network node. The second WADM has its first input coupled to the first output of the first WADM, its second input coupled to the second network fiber entering the network node, its first output coupled to the other access fiber providing signals to the array of receiving elements, and its second output coupled to the second network fiber leaving the network node. If for a given wavelength on the ring network, both the first and second WADMs are in the bar state, signals having the given wavelength pass through the network node in both directions undisturbed. If for a given wavelength on the ring network, the first WADM is in the bar state and the second WADM is in the cross state, a signal having the given wavelength on the first network fiber passes through the network node undisturbed. However, a signal having the given wavelength on the second network fiber is routed to the array of photodetectors so as to be dropped from the second network fiber, and a signal having the given wavelength provided by the array of transmitting elements is routed to the second network fiber leaving the network node. If for a given wavelength on the ring network the first WADM is in the cross state and the second WADM is in the bar state, a signal having the given wavelength on the first network fiber entering the network node is routed to the array of receiving elements, and a signal having the given wavelength provided by the array of transmitting elements is routed to the first network fiber leaving the network node. In the latter case, a signal having the given wavelength on the second network fiber entering the network node passes through the network node undisturbed to the second network fiber leaving the network node.
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