Fiber Link Budget
Total optical link loss budget calculator. Power budget vs. accumulated losses.
Channel Loss
12.00 dB
fibre 10.00 + splices 1.00 + connectors 1.00 dB
Received Power
-12.00 dBm
Tx power − channel loss
Margin above Sensitivity
16.00 dB
✓ 13.00 dB more than the 3 dB required
Maximum Length
115.0 km
keeping the margin, same splices and connectors
Power Level along the Link
Solid line: signal power from 0.0 dBm to -12.00 dBm, with connector and splice steps. Dashed violet: sensitivity plus the 3 dB margin. Dotted blue: receiver sensitivity.
Model
P_tx = P_rx + C_L + M_s C_L = α_f L + n_c α_con + n_s α_splice
The received power is the transmitter power minus the channel loss. The system margin M_s is not a loss: it is the part of the power above the receiver sensitivity kept in reserve for ageing, repairs, temperature and penalties the budget doesn't list. The link closes when P_rx − sensitivity ≥ M_s.
Not included: dispersion, reflection and other power penalties (add them to the margin), and receiver overload at short lengths. The diagram puts one connector at each end and spaces the others and the splices evenly.
Model and references
Exact. The equations are exact within the stated assumptions, or are a standard's tabulated values. The results are as good as the inputs. About the tiers
Decibel power budget P_tx = P_rx + C_L + M_s, with the margin held above the receiver sensitivity rather than subtracted from the received power. Dispersion and other penalties belong in the margin; overload not checked.
- Agrawal G. P. (2010). Fiber-Optic Communication Systems, 4th ed. Wiley. Ch. 5, lightwave system design: power budget P_tr = P_rec + C_L + M_s. doi:10.1002/9780470918524