Check whether your FTTH link closes: total optical loss from OLT to ONT — splitter, fiber, connectors, splices — against the ITU-T G.984.2 / G.9807.1 class budget, with a pass/marginal/fail verdict, max-reach solver, and the receiver-overload minimum-loss check most calculators skip. Built by the OSP engineers behind 44,000+ miles of designed plant.
GPON: 1490 nm down / 1310 nm up (ITU-T G.984.2). XGS-PON: 1577 nm down / 1270 nm up (ITU-T G.9807.1).
OLT to the farthest ONT along the actual cable route, not straight-line.
Centralized split = stage 1 only (e.g., 1:32 in the FDH). Cascaded/distributed = both stages (e.g., 1:4 × 1:8). Balanced PLC splitters only — unbalanced/tap splitters are not supported.
Count every mated pair: OLT patch panel, ODF, FDH/splitter ports, drop terminal / ONT.
Roughly one per reel end, plus closures and the drop splice.
Default 0.35 dB/km — a conservative planning value at the worst-case 1310 nm upstream wavelength. Use ≈0.25 dB/km if budgeting the 1490 nm downstream only; TIA-568 OSP maximum is 0.5 dB/km.
FOA recommends ≥ ~3 dB for aging, repairs, and temperature.
WDM1r coexistence element (~1–1.5 dB), extra patch panels, aging allowance.
Prefilled with typical datasheet maxima (conservative). Always confirm against the vendor datasheet — values vary by manufacturer; each doubling of split ratio adds ≈3 dB plus excess loss.
Engineering estimate only. This calculator produces a planning-level optical loss budget using ITU-T class limits and typical published component losses. It is not a substitute for design by a qualified engineer, vendor datasheet values, or field acceptance testing with an OTDR and optical power meter. Actual losses depend on workmanship, component quality, temperature, and aging. Draftech International assumes no liability for designs built solely on this output. For a stamped, buildable FTTH design, talk to our fiber design team.
Maximum-loss check. …
Minimum-loss (receiver overload) check. …
| Component | Loss (dB) | % of Class Budget |
|---|
Reviewed by: ______________________________________ Signature: ______________________________________ Date: ______________
Engineering estimate only — planning-level loss budget per ITU-T class limits (G.984.2 / G.9807.1) and typical published component losses. Verify against vendor datasheets and field acceptance testing (OTDR / optical power meter) before construction.
Generated with the free Draftech PON Power Budget Calculator — https://draftech.com/tools/pon-power-budget-calculator · Draftech International, LLC · info@draftech.com · 305-306-7407
A PON link closes when the total optical loss between the OLT and the farthest ONT stays inside the optical path loss window defined for the transceiver class — and only then. This GPON power budget calculator (and XGS-PON link budget checker) sums every loss element in the ODN and tests the result against both ends of the class window:
splitter_total = IL(stage 1) + IL(stage 2)
total_loss = km × dB/km + connectors × dB + splices × dB + splitter_total + additional
margin = class_max − total_loss
PASS margin ≥ design margin
MARGINAL 0 ≤ margin < design margin (link may close, no aging headroom)
FAIL margin < 0 (link will not close on this class)
overload total_loss < class_min → receiver-overload risk (add attenuation)
max_reach = (class_max − design_margin − fixed losses) ÷ dB/kmResults are computed at the worst-case (upstream) wavelength so they are conservative by default: 0.35 dB/km covers 1310 nm GPON upstream planning (the 1490 nm downstream typically runs ≈0.25 dB/km). Component defaults are FOA typical values — 0.3 dB per mated connector pair, 0.1 dB per fusion splice — with the TIA-568 acceptance maxima (0.75 dB / 0.3 dB) selectable when you want the pessimistic case.
The ODN class sets the loss window. GPON classes come from ITU-T G.984.2; XGS-PON classes from ITU-T G.9807.1. Note that every class has a minimum loss as well as a maximum — that minimum is what the receiver-overload check below enforces.
| Technology | Class | Min Loss (dB) | Max Loss (dB) |
|---|---|---|---|
| GPON (ITU-T G.984.2) | A | 5 | 20 |
| GPON | B | 10 | 25 |
| GPON | B+ | 13 | 28 |
| GPON | C | 15 | 30 |
| GPON | C+ | 17 | 32 |
| XGS-PON (ITU-T G.9807.1) | N1 | 14 | 29 |
| XGS-PON | N2 | 16 | 31 |
| XGS-PON | E1 | 18 | 33 |
| XGS-PON | E2 | 20 | 35 |
The splitter is almost always the largest single consumer of the budget. Each doubling of the split ratio adds ≈3 dB plus excess loss. The calculator defaults to the max column (conservative); edit per-ratio values under Advanced to match your vendor's datasheet.
| Split Ratio | Typical IL (dB) | Max IL (dB) — tool default |
|---|---|---|
| 1:2 | 3.5 | 3.8 |
| 1:4 | 7.0 | 7.3 |
| 1:8 | 10.5 | 10.7 |
| 1:16 | 13.7 | 13.9 |
| 1:32 | 17.0 | 17.2 |
| 1:64 | 20.4 | 20.5 |
Always confirm against the vendor datasheet — values vary by manufacturer; each doubling of split ratio adds ≈3 dB plus excess loss.
Free PON calculators check whether total loss stays under the class maximum and stop there. But an ODN class is a window, not a ceiling: GPON Class B+ is 13–28 dB. An ONT sitting a few hundred meters from the OLT behind a small split can arrive at the receiver hot — total loss below the class minimum, received power above the Rx overload threshold — and take errors on a link whose "budget" looks fine. This tool runs the minimum-loss check on every calculation and tells you when to add an inline attenuator or verify the transceiver's overload specification. On mixed-length PONs (a business park leg next to a rural run), that check is the difference between a clean turn-up and a truck roll.
Constants and limits used by this calculator, cited by standard:
Scope notes. Balanced PLC splitters only — unbalanced/tap architectures need a leg-by-leg budget. Effective splits above 1:64 generally require Class C+ era optics, and anything above 1:128 exceeds the GPON TC-layer limit. Blank inputs are treated as zero; negative values are blocked. This is a planning screen: acceptance is an OTDR trace and a power-meter reading, not a web page.
A loss budget that closes is the start of an FTTH design, not the end of one. The same engineering team that built this tool delivers FTTH design end to end — serving-area and FDH sizing, splitter placement, LLD with splice-level detail, and full fiber network design from HLD through construction-ready packages. If a class budget on this page won't close, the fix is usually architectural — split ratio, FDH placement, class upgrade — and that is exactly the trade-off analysis our designers run every day. We'll design your first 20,000 LF free, no commitment, so you can judge the output before you send the full route.
FREE FTTH DESIGN — FIRST 20,000 LF
Budget closes but the design doesn't exist yet? Send us your serving area and we'll design the first 20,000 LF free — splitter architecture, FDH sizing, and a loss budget that ties out. Active in 22 states. Available across all 50 U.S. states.
Start Free Design →A PON power budget — formally the optical path loss budget — is the amount of optical loss a passive optical network link can tolerate between the OLT transmitter and the ONT receiver while still operating reliably. ITU-T defines it per ODN class: GPON Class B+ allows 13–28 dB of path loss under ITU-T G.984.2, for example. Every element between the two ends — fiber attenuation, splitters, mated connectors, fusion splices — consumes part of that budget. The link closes when total loss stays under the class maximum with enough margin left for aging, repairs, and temperature effects; FOA guidance is to hold at least about 3 dB of design margin.
The math is identical — only the class limits and wavelengths change. GPON (ITU-T G.984.2) defines Classes A, B, B+, C, and C+ with maximum optical path loss from 20 to 32 dB; B+ (28 dB) and C+ (32 dB) are the classes deployed in practice. XGS-PON (ITU-T G.9807.1) defines classes N1, N2, E1, and E2 with 29, 31, 33, and 35 dB maximums. GPON runs 1490 nm downstream / 1310 nm upstream; XGS-PON runs 1577 nm downstream / 1270 nm upstream. Because both ride the same ODN, an ODN engineered to close on GPON B+ (28 dB) typically closes on XGS-PON N1 (29 dB) — but verify the budget, especially if a WDM1r coexistence element (roughly 1–1.5 dB) is added for overlay deployments.
Each ODN class specifies a minimum path loss as well as a maximum — Class B+ is 13–28 dB, not 0–28 dB. If an ONT sits close to the OLT on a low-split leg, total loss can fall below the class minimum and the received power can exceed the receiver's overload threshold, causing errors even though the budget looks fine on paper. Most free calculators only check the maximum. This tool flags any configuration whose total loss is below the class minimum so you can add an attenuator or pad, or verify the transceiver's Rx overload specification.
Balanced PLC splitter insertion loss runs roughly 3.5 dB per doubling of the split ratio, plus excess loss: about 7.3 dB maximum for 1:4, 10.7 dB for 1:8, 13.9 dB for 1:16, 17.2 dB for 1:32, and 20.5 dB for 1:64 (typical datasheet maxima including the splitter's connectors). Cascaded stages add together — a 1:4 × 1:8 cascade is about 18 dB across both stages. Values vary by manufacturer, so always confirm against the vendor datasheet; this calculator lets you edit the per-ratio values under Advanced.
A typical centralized-split FTTH link passes through about four mated connector pairs — OLT patch panel, ODF, the FDH/splitter ports, and the drop terminal or ONT — and roughly six fusion splices (reel ends, closures, and the drop splice); adjust to your actual splice diagram. Plan with 0.3 dB per mated connector pair and 0.1 dB per fusion splice (FOA typical values); TIA-568 acceptance maxima are 0.75 dB and 0.3 dB respectively. Designing at typical values and accepting at TIA maxima is common practice — just be consistent, and keep at least a 3 dB design margin on top.
Send us your serving area, target architecture, and homes passed. Our in-house FTTH designers will engineer the split architecture, FDH sizing, and LLD — with loss budgets that tie out on every leg. Active in 22 states. Available across all 50 U.S. states.
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