FTTH PON split planner

On a passive optical network, one fiber leaving the OLT is fanned out to many homes by a passive splitter. The split ratio is how many ways that one feed is divided: 1:32 means one PON port serves up to 32 subscribers. Higher ratios share the fiber and the port across more homes, which lowers cost per home but leaves less optical power for each one.

Start from subscribers, not homes passed. Multiply homes passed by your take rate to get subscribers, then divide by the split ratio and round up: that is your splitter count. In a single-stage design each splitter takes one OLT PON port, so ports equal splitters. For example 1,000 homes at a 40% take rate at 1:32 gives 400 subscribers, 13 splitters and 13 ports.

A 1:32 passive splitter adds roughly 17.5 dB of insertion loss, and a 1:64 adds about 21 dB. That loss subtracts straight from your optical power budget before any cable, connector or splice loss is counted, which is why high split ratios shorten the distance the signal can reach. Feed the split loss into the fiber loss budget calculator at /tools/fiber-loss-budget to see whether the whole link still closes.

Take rate is the share of homes passed that actually subscribe. New FTTH builds often plan around 30% to 40% in the early years and climb higher as the network matures, though it varies a lot by market and competition. Planning splitters and ports to the take rate you expect (with some room to grow) avoids buying hardware for homes that never sign up.

Single-stage puts one splitter between the OLT port and the homes, which is what this planner assumes. Two-stage splitting uses a primary splitter at the cabinet and smaller secondary splitters closer to the homes (for example 1:4 then 1:8 to reach 1:32 total). Two-stage can save fiber in the feeder but the combined insertion loss is higher, so always recheck the power budget.