Free engineering tool
Fiber Link Loss Calculator
Estimate the total loss of a fiber link from its length, connector count, splice count and wavelength. Every number is an editable planning default — replace it with your own measured or supplier data.
Runs in your browser. No sign-up, nothing sent to a server.
Estimated link loss
Total loss
| Breakdown | dB | Share |
|---|---|---|
| Fiber attenuation | 0.035 | 6% |
| Connectors | 0.60 | 94% |
| Splices | 0.00 | 0% |
Formula
Total loss = (length ÷ 1000 × attenuation) + (connectors × loss per connector) + (splices × loss per splice)
= (100.00 ÷ 1000 × 0.35) + (2.00 × 0.30) + (0.00 × 0.10)
Actual loss depends on components and installation; use measured data for acceptance.
How to use it
Three steps
- 1
Enter the link length
Use the cable route in metres, including slack and the patch leads at both ends.
- 2
Count connectors and splices
Count each mated pair once: equipment ports, patch panel ports and ODF adapters. Count every fusion or mechanical splice.
- 3
Choose the wavelength, then replace the defaults
1310 nm and 1550 nm have different attenuation. Overwrite the three loss values with your cable and connector data before you rely on the result.
Where the loss comes from
Why the connector count matters most
On a short link the glass contributes very little: 100 m at 1550 nm is 0.025 dB, while one mated connector pair at the 0.30 dB planning value is 0.30 dB — twelve times more. Two connectors already outweigh the fiber, and every extra patch panel adds another pair.
- Fiber: 0.25 dB/km at 1550 nm means 0.025 dB per 100 m.
- Connectors: one mated pair per adapter; the default is a planning value, not a specification.
- Splices: on a short indoor link this is usually the smallest term.
Common mistakes
Four things that make the estimate wrong
Counting connectors instead of mated pairs
Two plugs in one adapter are a single loss event. Counting them twice doubles the connector term.
Leaving out the patch leads
A route measured only between panels still has cords at both ends — and two more mated pairs.
Mixing measured and catalogue values
A measured connector loss combined with a catalogue attenuation gives a number that matches neither.
Forgetting splices on long outdoor runs
Spliced routes carry real loss at every splice; a zero count hides part of the budget.
From estimate to hardware
Need the cords, or a second opinion?
Fiber optic patch cords
SC, LC, ST and FC assemblies in UPC and APC, made to the length and polarity you specify.
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Stainless-steel armored cords for runs where crush or rodent protection matters.
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Send the route and the components you plan to use; we will check the numbers with you.
Contact usQuestions
About the calculation
- What formula does the calculator use?
- It adds three loss terms: fiber attenuation over the route length (length ÷ 1000 × dB/km), connector loss per mated pair, and splice loss per splice. No safety margin is included.
- Are the default values measured data?
- No. They are planning defaults, editable: 0.30 dB per connector, 0.10 dB per splice, 0.35 dB/km at 1310 nm and 0.25 dB/km at 1550 nm. Replace them with your own measured or supplier values before you use the result for acceptance.
- How many connectors should I count?
- Count every place where two connectors are mated through an adapter: equipment ports, patch panel ports, ODF adapters. A cord between two devices with no panel has two mated pairs, one at each end.
- Does the result include splices and margins?
- Splices are included when you enter a count. The calculator does not add a design margin, repair margin or aging allowance; add those separately if your project requires them.
Ready to specify the cords?
Tell us the length, connector type and polish, and we will quote patch cords or armored assemblies against your loss budget.