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Fibre Optic Loss Budget Calculator

Work out fibre optic loss budget instantly with clear inputs, formula shown and shareable results.

About Fibre Optic Loss Budget Calculator

A fibre loss budget adds attenuation per kilometre to the loss of each connector pair and splice. Single-mode fibre loses about 0.35 dB per km at 1310 nm and 0.22 at 1550, while connectors cost roughly 0.5 dB each and fusion splices only 0.1. TIA guidance is to add about 3 dB of margin for ageing, repairs and temperature.

Formula

Loss budget

total = length x attenuation per km + connector pairs x 0.5 dB + splices x 0.1 dB; add 3 dB margin

Worked example

With the default values below, Fibre Optic Loss Budget Calculator returns Total link loss of 6.80. Change any input above and every figure here is recalculated in your browser.

Inputs used

Fibre lengthminimum 0.001 km
12 km
Wavelengthone of 850 nm multimode (3.0 dB/km), 1310 nm single mode (0.35 dB/km), 1550 nm single mode (0.22 dB/km)
1310 nm single mode (0.35 dB/km)
Connector pairsminimum 0
4
Fusion splicesminimum 0
6

Results

Total link loss
6.80 dB
Loss from the fibre itself
4.20 dB
Loss from connectors and splices
2.60 dB
Budget including a 3 dB margin
9.80 dB

Step by step

  1. 1Values used
  2. 2Loss budget
  3. 3Total link loss= 6.80 dB
  4. 4Loss from the fibre itself= 4.20 dB
  5. 5Loss from connectors and splices= 2.60 dB
  6. 6Budget including a 3 dB margin= 9.80 dB

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is 1550 nm used for long spans?

Its attenuation is the lowest of the standard windows, about 0.22 dB per km, which extends reach substantially and is also where erbium-doped amplifiers operate.

Why are connectors so much worse than splices?

A connector is a mechanical mating with an air gap and alignment tolerance; a fusion splice welds the cores together. Contamination on a connector face can add several dB.

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