1. Schematic 1 shows a 1xn optical splitter is added to a standard WDM-PON system by inserting it before the WGR at RN. A MxN WGR instead of a 1xN WGR is used at RN. With this arrangement, the WDM-PON uses only m wavelengths (mxn=N, number of ONUs); and n ONUs share the same wavelength such that TDM mechanism must be adopted to provide the multiple access among the shared ONUs. Each ONU has in average B/n bandwidth, where B is the bit rate of each transmitter. If larger bandwidth or other services are needed in the future, one set of extended channels with the wavelengths {e1, e2, …, eN} can be used to provide each ONU with one full-bandwidth (say 10 Gb/s) channel. Channel fault monitoring needs an optical bandwidth covering m wavelengths rather than N wavelengths. If n is small, the OTDR should be able to resolve the reflected signals or the distribution fibers can easily arranged to have different lengths among the shared ONUs. The operation principles can be achieved by using the cyclic property of an waveguide grating router (WGR), and the wavelength w (the w-th wavelength) to connect Input x to output y can be expressed as w=(N-x+y+1) mod N.
2. Schematic 2 can provide flexible bandwidth management and allow for upgrading bandwidth by adding extra WDM channels and offers three different classes of services. The service path including point-to-point, point-to-multpoint, and broadcasting services can be provided by the same architecture. Also provides flexible installation and easy upgrading of the service, each distribution fiber for hybrid PON services can be further extended to service more ONUs by attaching a splitter at the end. The channel fault monitoring needs smaller optical bandwidth while implementing.
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