Optical Power Margin Calculator

Work out optical power margin instantly with clear inputs, formula shown and shareable results.

About Optical Power Margin Calculator

The optical budget is the transceiver's output power minus its receive sensitivity, and the margin is what remains after subtracting measured link loss and an allowance for ageing, connector degradation and future repair splices. A margin below about 2 dB means the link will fail as connectors get dirty or the plant is repaired.

Formula

Optical margin

budget = Tx power - Rx sensitivity; margin = budget - link loss - ageing allowance; received power = Tx - link loss

Worked example

With the default values below, Optical Power Margin Calculator returns Power margin after ageing allowance of 5.50. Change any input above and every figure here is recalculated in your browser.

Inputs used

Transmitter output poweraccepts -30–20 dBm: -3 dBm
Receiver sensitivityaccepts -40–0 dBm: -21 dBm
Measured link lossaccepts 0–60 dB: 9.5 dB
Ageing and repair allowanceaccepts 0–10 dB: 3 dB

Results

Power margin after ageing allowance: 5.50 dB
Optical budget of the transceiver pair: 18.00 dB
Power at the receiver: -12.50 dBm
Assessment: Healthy margin

Step by step

1Values used
2Optical margin
3Power margin after ageing allowance= 5.50 dB
4Optical budget of the transceiver pair= 18.00 dB
5Power at the receiver= -12.50 dBm
6Assessment= Healthy margin

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

Can the received power be too high?

Yes. Exceeding the receiver's overload threshold causes errors just as surely as too little power, which is why short links sometimes need an attenuator.

What should the ageing allowance cover?

Connector contamination, additional repair splices over the cable's life, temperature variation and transceiver output decline. Three dB is a common figure.