| 摘要 |
A method for transmitting broadcast and narrowcast services in a system having a headend, a hub connected the headend, and a plurality of nodes connected to the hub. Instead of transmitting the signals directly from the headend to each node, the signals are transmitted from the headend to the hub. The signals transmitted from the headend to the hub include both broadcast services to be transmitted to each node and narrowcast services to be transmitted only to predetermined targeted nodes. The broadcast and narrowcast services are transmitted by optical signal beams operating at different wavelengths. Subscribers can transmit signals to the headend, via each node, on the reverse channel. The reverse channel information from subscribers is combined at each respective node into a single wavelength for each node. The narrowcast services are added at the headend instead of at the hub. By adding the narrowcast services at the headend, the processing of the narrowcast signals is performed by the electronic processing equipment at the headend. Therefore, the narrowcast signals leave the headend as optical signals, and the hub is only required to perform optical signal processing, and is not required to have any electrical processing equipment. In this manner, the hub performs only optical signal processing, which reduces the complexity and cost of the system.
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