Pasyviosios magistralės panaudojimas optinės prieigos tinkluose

Abstract

The development of the Internet is inseparable from increasing the speed of information transmission between computer network devices using optical cables, which may contain several dozen or hundreds of optical fibres. A separate optical fibre can simultaneously transmit information from different information sources using signals with different wavelengths. A network infrastructure with such capabilities is called a Passive Optical Network. Using a separate optical fibre makes it possible to increase the real-time data transfer rates by millions of times compared to the existing data transfer rates. The need for high information transmission speeds arises when connecting important national or interstate networks. A much lower data transfer speed is sufficient for an individual user of Internet services. Literature sources describe optical access networks in which individual optical fibres are connected to the devices of service users, and the fibres themselves are interconnected according to the tree principle: primary fibre branches are first connected to the trunk, then secondary fibre branches are connected to their remote ends, and so on. Connections are made using optical splitters. The main feature of such a network is that the distances from the beginning of the trunk to the remote ends of the fibres are usually relatively small (up to a few kilometres), and the attenuation of optical signals in such lines differs little (up to a few dB). The networks created in such a way are called FTTx (Fibre To The x). The article investigates a network configuration in which user devices can be serially connected to the same optical fibre called a trunk. The length of such a trunk fibre can reach tens of kilometres. In this case, there can be different lengths of the optical line from the beginning of the line to the individual consumer devices, and the signal attenuations could also be different (up to 30 dB). To equalise optical signal attenuations, an optical signal splitter with appropriate parameters must be used at each point of connection of the user device to the trunk. The methodology for calculating the parameters of optical splitters connected to the trunk is presented. The functional dependence of the coverage of the passive optical network on the number of trunk splitters was found.