| 摘要 |
An add/drop (7) node for an optical fiber network of WDM type has preamplifiers (21, 23) connected to the input fibers (3, 11). Part of the incoming signal power is tapped off by means of drop couplers or splitters (45, 47). The tapped-off power is provided to demultiplexers (49, 51), one demultiplexer being used for each direction, in which WDM information channels are separated from each other. The output signals of the two demultiplexers which comprise the same wavelength interval are combined in combining couplers (73, 75, 77) and then fed to optoelectrical receivers (15), where the information of the dropped channels is converted to electrical signals. In order to monitor and maintain a satisfactory transmission quality of the signal from the node (7), the optical power in each wavelength channel of the multiplexed light signal transmitted in the network is measured, independently for west and east traffic, by adding splitting couplers (61, 63, 65; 67, 69, 71) to the outputs of the demultiplexers (49, 51). These splitting couplers deflect a portion of the signal power to optical power detectors (53), which provide signals informing on the individual power levels. This design gives a node having a minimum number of multiplexers and also the node has a better performance in failure states. WDM information channels to be added in the node from electro-optical transmitters (17) are combined in a multiplexer (29), the resulting signal being split (31) and provided to add couplers (33, 35) to which also the signals incoming to the node are provided. |
