Based on passive optical networking technology, Fiber-to-Home (FTTH) access network is a point-to-multipoint network structure, which utilizes optical splitters to transmit central station signals to multiple end-users. There are two different distribution methods of optical splitters in the FTTH network: centralized distribution and cascaded distribution, corresponding to one-stage and two-stage splitting modes, respectively. Each of these splitting methods has its own advantages and disadvantages, which will be discussed in detail below by Grandway.
One-stage splitting refers to the optical splitter between the optical line terminal and the optical network unit being parallel. Its basic form is "OLT → Optical Splitter → ONU", and the splitting ratio of the optical splitter used here is usually 1:64. In the application of one-stage splitting in the FTTH network, the optical splitter can be centrally installed at the central station, but in order to save the cost of the fiber, the optical splitter is usually installed between the OLT and the ONU. The central station and the optical splitter are connected by a backbone fiber cable (also called a feeder fiber cable), and the user terminal and the optical splitter are connected by a distribution fiber cable. The backbone fiber cables are generally selected from common outdoor fiber cables, with fiber core numbers ranging from 12 to 144; the distribution fiber cables should be selected according to specific application environments and are generally common outdoor fiber cables, while for some occasions, it may be necessary to choose flame-retardant fiber cables.
Two-stage splitting in the FTTH network refers to a cascaded optical splitter between the OLT and the ONU, which has a basic form of "OLT → Optical Splitter 1 → Optical Splitter 2 → ONU". The splitting ratio of optical splitter 1 is usually 1:4 or 1:8, and that of optical splitter 2 is usually 1:8 or 1:16. In two-stage splitting applications, the first-stage optical splitter is often installed in an optical distribution box or a fiber-splitting box, while the second-stage optical splitter is often installed in a local residence or community closer to the end-user.
As described above, in one-stage splitting applications, optical splitters are centrally distributed in one place, thus maximizing the utilization of the OLT port, making it suitable for applications with a large number of end-users. Two-stage splitting applications with cascaded distributed optical splitters are suitable for applications with dispersed end-users and a smaller number of end-users.
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