What is Centralised Splitting?
A centralised splitting network is one in which the optical splitters between the optical line terminal (OLT) and the optical network unit (ONU) are in parallel, basically in the form of "OLT → optical splitter → ONU", where the splitting ratio of the optical splitters used is usually 1:64. In a centralised split network application, the optical splitter can be installed centrally at the central office, but in order to save on fibre costs, the optical splitter is usually installed between the OLT and the ONU in practice.
The OLT (Optical Line Terminal) active port in the central office (CO) will be connected/spliced to a fibre leaving the CO. This fibre passes through different closures to reach the input port of the fibre splitter, normally placed in a cabinet. A fibre exiting the central office (CO) will be joined or spliced to the OLT (Optical Line Terminal) active port. To get to the input port of the fibre splitter, which is often housed in a cabinet, this fibre must pass through various closures. This fibre splitter's output port connects to the FTTH distribution network, which connects to potential customers' houses via various closures and indoor/outdoor terminal boxes, or ONTs (Optical Network Terminal). With this centralised splitting architecture, the PON therefore links one OLT port to 32 ONTs.
What is Distributed Splitting?
In contrast to centralised splitting architecture, a distributed splitting strategy does not use fibre splitters in the central office. An outside plant fibre is directly attached to or spliced onto the OLT port. Near the main office, the first level of splitting (1:4 or 1:8) is built in a closure. The OLT fibre arriving from the central office is connected to the input of this first-level fibre splitter. Each splitter on the second level of fibre splitters (1:16 or 1:8), which are located in terminal boxes extremely close to the customer's premises, can cover 8 to 16 residences. The fibres from the outputs of the first level splitters mentioned above are the inputs of these PON splitters.
How to Choose Between Centralised Splitting vs Distributed Splitting?
The advantages and disadvantages of centralised splitting and distributed splitting networks are summarized in the table below:
The FTTH network architecture will be determined by a number of variables, including your financial situation and expected future scalability. The scale of your consumer base is another important determining factor. Distributed splitting would be ideal for connecting numerous customers quickly in urban areas. Nonetheless, centralised division is preferable since it offers more flexibility for remote or sparsely inhabited areas.
Conclusion
Please always take into account every particular component of your network scenario before choosing which splitting techniques to apply in a PON-based FTTH network. Given that both centralised and distributed splitting networks have advantages and disadvantages, the best architecture is the one that satisfies the provider's needs and expectations while lowering capital costs, maximizing long-term operational expenses, and creating a network that is future-proof and can adapt to new technologies without major changes.