ahhaha, well here is HLIT's system,and a good description of how and where is was implemented. I am still deciphering the data,and going through my archives.
cedmagazine.com
Figures 5, 6 and 7 illustrate examples of DWDM implementations. Figure 5 shows the design implemented in the TCI system in Baton Rouge, La. Broadcast signal distribution from the secondary hub to the fiber nodes was already in place using 1310 nm technology. Narrowcast lasers operating at 1550 nm were added at the headend and multiplexed over a single fiber for transmission to the hub. At the hub, narrowcast wavelengths are amplified, de-multiplexed, and individually combined with the 1310 nm broadcast signal before transport to the node. Standard 1310/1550 WDM couplers are used to combine broadcast and narrowcast signals. This approach resulted in less than 0.5 dB of additional insertion loss for the 1310-nm broadcast signals, therefore minimizing the impact on their performance at the node.
Figures 6 and 7 show a design implemented in the TCI-Dallas system. Broadcast and narrowcast signal distribution is implemented using 1550 nm technology. Broadcast transport from the Arlington headend to two field OTNs (optical transport nodes) uses no more than two EDFAs in cascade to reach all fiber nodes, while maintaining the performance in Table 1.
Narrowcast services are transported using eight different wavelengths multiplexed over a single fiber. All narrowcast wavelengths are amplified and de-multiplexed at OTN 1. Six of them are individually combined with the broadcast 1550-nm signal and split to feed a number of fiber nodes. The other two are transported over two dedicated fibers from OTN 1 into OTN 2, where they are finally combined with the broadcast wavelength and split to feed the remaining nodes in the system.
Table 2: Available DWDM wavelengths.
Figure 8 is an example of a design for optical insertion of PEG channels at the hub. In this case, the 1310 nm lasers carrying PEG programming are located in the hub. Standard 1310/1550 WDM couplers are used for insertion of PEG programming. Each 1310 nm laser targets a group of fiber nodes as required. Downstream from the 1310 nm insertion point, 1550 nm narrowcast signals are inserted using standard couplers prior to final transport into the nodes.
DWDM is a practical alternative now available to HFC network designers. It has been deployed successfully in a number of TCI markets. The technology allows for the narrowcasting of high-speed data and other services, flexible network segmentation and a reduction in the number of active electronics that must be deployed outside the system headend. Bandwidth expansion is easily achieved through the activation of additional narrowcast wavelengths per service area with minimal interruption to existing services.
All of these installations are HLIT's,and the blueprints were made by their engineers.
Hiram
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