Patent ID: 6597482
Filing Date: 2003-07-22
Classification: H04J

Abstract:
A wavelength division multiplexed passive optical subscriber network including a central office, and at least one remote node which is coupled to the central office by way of at least one first optical fiber and further is coupled to a plurality of subscriber's units by way of at least one second optical fiber, the maximum number of said subscriber's units being Nâˆ’1 where N is a natural number, wherein(i) said central office comprises: a first optical signal generating means for generating an optical signal; a multi-channel signal generating means for generating Nâˆ’1 wavelength divided channel signals using the optical signal generated by said first optical signal generating means; Nâˆ’1 modulating means each for modulating the channel signals generated by said multi-channel signal generating means; a first NÃ—N multiplexing/demultiplexing means having N input ports and N output ports, wherein wavelength divided downstream signals, inputted from each of said Nâˆ’1 modulating means through Nâˆ’1 of the N input ports and not through one remaining input port among the N input ports, are multiplexed onto one output port among the N output ports and not onto Nâˆ’1 remaining output ports of the N output ports, and simultaneously, multiplexed upstream signals inputted from said remote node through the one remaining input port among the N input ports are demultiplexed onto the Nâˆ’1 remaining output ports of the N output ports; and Nâˆ’1 first detection means each coupled to said Nâˆ’1 remaining output ports of said first NÃ—N multiplexing/demultiplexing means for receiving the demultiplexed channel signals of each subscriber's unit; (ii) said remote node comprises: a second NÃ—N multiplexing/demultiplexing means having N input ports and N output ports, wherein the multiplexed downstream signals inputted from the one output port of the first NÃ—N multiplexing/demultiplexing means through one input port of the second NÃ—N multiplexing/demultiplexing means are demultiplexed onto Nâˆ’1 output ports of the second NÃ—N multiplexing/demultiplexing means, and simultaneously, signals inputted from said subscriber's units through the Nâˆ’1 remaining input ports of the first NÃ—N multiplexing/demultiplexing means are multiplexed onto the one remaining output port of the second NÃ—N multiplexing/demultiplexing means and then transmitted to the one remaining input port of the first NÃ—N multiplexing/demultiplexing means as the multiplexed upstream signals, and (iii) each subscriber's unit comprises: a second detection means for receiving the signals demultiplexed by said second NÃ—N multiplexing/demultiplexing means; and a second optical signal generating means for generating an optical signal, wherein, first band-pass filters (BPF1) are used in the first optical signal generating means and the second detection means, and second band-pass filters (BPF2) are used in the second optical signal generating means and each of the Nâˆ’1 first detection means, said first and second band-pass filters (BPF1 and BPF2) having a center wavelength different from each other to limit the spectrum band of said first and second optical signal generating means, so that wavelength bandwidths of downstream signals transmitted from said central office to said remote node and upstream signals transmitted from said remote node to said central office are different from each other.