1. Pick the fiber type and wavelength the optic uses (for example OS2 at 1310 nm for 1000BASE-LX or 10GBASE-LR, OM4 at 850 nm for 10GBASE-SR). For single-mode, choose the cable type: outside plant, indoor/outdoor or inside plant.
2. Enter the route length in km or m, the number of mated connector pairs (a patch panel at each end counts as one pair each, plus any cross-connects) and the number of splices.
3. Choose the loss preset: the TIA/ISO maximum for design and acceptance limits, Typical for an expected test result, or Custom for your cable and connector datasheets.
4. Add any PON splitter or other passive losses, and set a safety/repair margin (3 dB is the usual default).
5. In Power budget check, pick an optic preset or type the Tx minimum launch power and Rx sensitivity from the datasheet. Add Tx maximum and Rx overload to check short links.
6. Read the verdict: PASS means the margin covers your safety margin, MARGINAL means it works now but has no repair headroom, and FAIL means it will not work reliably. Check the reach and the application-limit warning.
7. Save the project, export it as JSON, or print to PDF for your design file. After installation, compare OTDR and power-meter results with the Typical and Max columns.

Tips & common mistakes

• Count connector pairs (mated connections), not individual connectors. A link with patch panels at both ends has at least 2 pairs.
• Power budget is not the only limit: multimode reach is limited by bandwidth (10GBASE-SR is 300 m on OM3, 400 m on OM4) even when the dB look fine.
• Long-reach optics (ER, ZR, PON OLTs) on short links can overload the receiver. Fit an in-line attenuator at the receiver.
• Use the minimum Tx power and the worst-case sensitivity from the datasheet, not the typical values.
• Clean and inspect every connector before testing: one dirty connector can add more than 1 dB.

Standards & assumptions

Maximum values: ANSI/TIA-568.3-D (cabled fiber 3.5 dB/km at 850 nm and 1.5 dB/km at 1300 nm for multimode; single-mode 1.0 dB/km inside plant, 0.5 indoor/outdoor, 0.4 outside plant at 1310 and 1550 nm; 0.75 dB per mated connector pair; 0.3 dB per splice) and ISO/IEC 11801-1 (OS2 0.4 dB/km at 1310, 1383 and 1550 nm). TIA-568.3-D lists 3.0 dB/km at 850 nm for laser-optimised OM3/OM4; this tool keeps the more conservative 3.5 dB/km also used in the IEEE 802.3 channel models. Typical values are representative installed figures, not normative. Optic figures follow IEEE 802.3 and ITU-T G.984.2 (GPON B+/C+) and are typical: always use the transceiver datasheet. Splitter losses are typical PLC maxima. The result is for guidance only and must be verified against the manufacturer's data, field test results and local code.