Free tool Updated 14 Oct 2026
Splitter loss calculator
An ideal 1×N splitter loses 10 × log10(N) dB; real PLC splitters lose a little more: 17.1 dB for a 1×32 and 20.4 dB for a 1×64 at catalogue maximum. Compare ratios and cascades below.
Calculator
Splitter loss
17.1dB
- Outputs per feeder fiber
- 32
- Ideal (theoretical) loss
- 15.1 dB
- Excess over ideal
- 2.0 dB
- Left in GPON class B+ after margin
- 7.9 dB
- Rough fiber reach
- 16 km
Losses are catalogue maxima (PLC with connectors, FBT without). Reach assumes 1.2 dB of connections and 0.4 dB/km of fiber and splices at 1310 nm; use the fiber loss calculator for your real link.
Splitter loss in one line
Ideal loss (dB) = 10 × log10(N) · one leg of an unequal split = −10 × log10(share)
Splitting light N ways leaves each output 1/N of the power: 3 dB for every halving. Real splitters add excess loss and non-uniformity between ports, so plan with the maximum insertion loss from the datasheet, not the ideal figure.
PLC splitter loss table
| Ratio | Ideal loss | Maximum insertion loss |
|---|---|---|
| 1×2 | 3.0 dB | 4.1 dB |
| 1×4 | 6.0 dB | 7.4 dB |
| 1×8 | 9.0 dB | 10.5 dB |
| 1×16 | 12.0 dB | 13.8 dB |
| 1×32 | 15.1 dB | 17.1 dB |
| 1×64 | 18.1 dB | 20.4 dB |
| 2×4 | 6.0 dB | 7.7 dB |
| 2×8 | 9.0 dB | 10.8 dB |
| 2×16 | 12.0 dB | 14.1 dB |
| 2×32 | 15.1 dB | 17.4 dB |
Maximum values include connectors and hold at 1310, 1490 and 1550 nm (FiberHome catalogue). A 2×N splitter has two inputs, for example for a protected or second OLT feed, and loses about 0.3 dB more than the 1×N.
FBT unequal splitter loss table
| Ratio | Small leg | Large leg |
|---|---|---|
| 50/50 | 4 dB | 4 dB |
| 45/55 | 4.65 dB | 3.65 dB |
| 40/60 | 5.3 dB | 3.3 dB |
| 35/65 | 5.95 dB | 2.9 dB |
| 30/70 | 6.7 dB | 2.5 dB |
| 25/75 | 7.65 dB | 2.2 dB |
| 20/80 | 8.8 dB | 1.8 dB |
| 15/85 | 10.1 dB | 1.5 dB |
| 10/90 | 11.5 dB | 1.25 dB |
| 5/95 | 14.8 dB | 0.9 dB |
| 2/98 | 19.4 dB | 0.8 dB |
| 1/99 | 22.7 dB | 0.75 dB |
Maximum values without connectors. Unequal taps suit linear routes, such as a road or a railway, where each tap drops a little light and the rest travels on.
Cascaded splits: 1×4 then 1×8, or one 1×32?
Both serve 32 homes. At catalogue maxima the cascade loses 7.4 + 10.5 = 17.9 dB against 17.1 dB for a single 1×32, and adds a connection or splice between the stages. In exchange, the first-stage 1×4 can sit in a central cabinet and the 1×8s closer to the homes, which saves feeder and distribution fiber. Run both options through the calculator above with your optics class.
How much budget is left for fiber?
Subtract the splitter loss and a safety margin from the class maximum. With GPON class B+ (28 dB), a 1×32 (17.1 dB) and a 3 dB margin, 7.9 dB is left for fiber, connections and splices: roughly 16 km at 1310 nm with four connections. Class C+ (32 dB) adds 4 dB, about 10 km more.
Every PLC splitter we supply ships with the insertion loss measured on each port, so you can replace these maxima with the real numbers. See ODN and FTTx components and the PLC splitter and GPON budget guide.
Sources
- FiberHome, optical splitter product catalogue, PLC and FBT insertion loss tables, 2024. fiberhome.com
- ITU-T, “G.984.2: Gigabit-capable passive optical networks (G-PON): Physical media dependent (PMD) layer specification”, August 2019. itu.int
- ITU-T, “G.9807.1: 10-Gigabit-capable symmetric passive optical network (XGS-PON)”, February 2023. itu.int
- The Fiber Optic Association, “Calculating Fiber Optic Loss Budgets”. thefoa.org
FAQ
Splitter loss questions
What is the loss of a 1×32 splitter?
About 15.1 dB in theory (10 × log10 32). Real PLC splitters add excess loss and port-to-port variation; catalogue maxima are about 17 dB, for example 17.1 dB with connectors.
Is a 1×4 then 1×8 cascade worse than one 1×32?
Slightly: 7.4 + 10.5 = 17.9 dB at catalogue maxima against 17.1 dB for a single 1×32, plus one more connection or splice. It serves the same 32 homes and can save feeder fiber, so check both against your budget.
What is the difference between a PLC and an FBT splitter?
A PLC splitter divides light equally on a silica chip and is the standard for 1×8 and larger PON splits. An FBT splitter is made by fusing fibers and suits 1×2 taps with unequal ratios, such as 10/90 on a linear route.
How do I calculate the loss of an unequal split?
In theory, loss = −10 × log10(share), so a 10% leg loses 10 dB and a 90% leg 0.46 dB. Real FBT couplers add excess loss: the catalogue maxima are 11.5 dB and 1.25 dB for a 10/90 coupler.
Which wavelength are splitter losses specified at?
PLC splitters are broadband and specified across 1260–1650 nm; the catalogue figures here were measured at 1310, 1490 and 1550 nm. FBT couplers are more wavelength-dependent, so check the window on the datasheet.
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