Fiber Loss Budget
Calculate the optical power budget of your fiber link: add up the loss from distance, connectors and splices and compare it with the available power (Tx − Rx) to find the real margin in dB. All the calculation happens in your browser.
Loss breakdown
| Component | Detail | Loss (dB) |
|---|
How it is calculated
Link loss = distance (km) × attenuation (dB/km) + connectors × loss per connector + splices × loss per splice.
Power budget = Tx power (dBm) − Rx sensitivity (dBm).
Margin = Budget − Link loss.
The margin must be > 0 for the link to work. It is recommended to leave ≥ 3 dB of headroom. The maximum distance distributes the remaining budget (after subtracting connectors, splices and safety margin) across the fiber attenuation.
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How it works
The calculator builds the optical power budget (loss budget) of a fiber link: it sums the loss from distance (km × dB/km), connectors and splices, and compares it with the available power, which is Tx (dBm) − Rx sensitivity (dBm). The result is the link margin in dB and the maximum reachable distance with your chosen safety margin.
The defaults are reference plant values: 0.35 dB/km attenuation for OS2 single-mode at 1310 nm (0.22 at 1550 nm) and 3.0 dB/km for OM3/OM4 multimode at 850 nm; 0.3 dB loss per connector (the TIA-568 maximum is 0.75 dB) and 0.1 dB per fusion splice (0.3 dB mechanical). It includes IEEE 802.3 transceiver presets (1000BASE-SX/LX, 10GBASE-SR/LR) with their typical Tx power and Rx sensitivity, and recommends reserving at least 3 dB of headroom for aging and repairs.
Example: 10 km of OS2 at 1310 nm with −4/−17 dBm optics
- Link loss:
10 × 0.35 = 3.5 dBof fiber +4 × 0.3 = 1.2 dBof connectors +2 × 0.1 = 0.2 dBof splices = 4.9 dB. - Power budget:
−4 − (−17) = 13 dB. - Margin:
13 − 4.9 = 8.1 dB, above the 3 dB safety margin → link OK. - Maximum distance with that hardware:
(13 − 1.2 − 0.2 − 3) ÷ 0.35 ≈ 24.6 km.