PON optical splitter bandwidth decreases

In a PON, increasing the optical splitter ratio reduces the bandwidth available per user because the total OLT bandwidth is shared among more endpoints and signal power per port decreases.Bandwidth Sharing in PON NetworksIn a Passive Optical Network, a single Optical Line Terminal (OLT) port serves multiple Optical Network Terminals (ONTs) through an optical splitter. The splitter divides the optical signal, allowing one fiber to reach multiple users, but this also means that the total available bandwidth is shared among all connected ONTs. For example, a 1:32 splitter divides the OLT bandwidth among 32 users, while a 1:64 splitter divides it among 64 users, effectively halving the bandwidth per user if the total OLT capacity remains constant .Impact of Split Ratios and Signal PowerHigher split ratios not only share bandwidth but also reduce optical power per output port. Each doubling of the split ratio typically reduces the power by about 3 dB. Lower optical power can limit the maximum distance the signal can travel and may require higher-quality ONTs or additional amplification to maintain performance . For instance, a 1:32 splitter introduces roughly 15 dB of insertion loss, while a 1:64 splitter adds about 18 dB, leaving less margin for fiber attenuation and potentially reducing effective bandwidth at the user end .Splitter Architectures and Bandwidth DistributionThe placement and type of splitter also influence bandwidth distribution:Centralized splitting uses a single-stage splitter near the OLT, which simplifies management but concentrates the bandwidth sharing at one point .Cascaded (distributed) splitting uses multiple stages of splitters closer to subscribers, which can balance optical power more effectively but may slightly increase complexity and insertion loss .Practical ConsiderationsNetwork designers must balance split ratio, distance, and bandwidth demand. Using a higher split ratio reduces per-user bandwidth but lowers infrastructure costs. Conversely, lower split ratios provide higher bandwidth per user but require more fibers and OLT ports . Non-uniform splitters can allocate more power to high-demand users, but they are more expensive and require careful planning . In summary, PON optical splitter bandwidth decreases primarily due to the sharing of OLT capacity among more users and the reduction of optical power per port, with the effect amplified by higher split ratios and longer fiber distances. Proper network design, including split ratio selection and splitter placement, is essential to maintain adequate bandwidth for all subscribers .