Optical Power
Calculate received optical power at a fiber receiver given transmit power and losses.
About Optical Power
Optical power meters typically read out in dBm, computed as P(dBm) = 10·log10(P_mW). Comparing a measured power level against common reference points — typical transmitter output (often around 0 dBm for SFP+ optics), typical receiver sensitivity (around -17 to -22 dBm), and receiver overload thresholds (power too high can saturate a receiver just as easily as too little can starve it) — helps quickly assess whether a measured link power reading is healthy.
Formula
Power in dBm
P(dBm) = 10 × log10(P_mW)
Worked example
With the default values below, Optical Power returns Optical Power of 0.000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Optical Powerminimum 0 mW
- 1 mW
Results
- Optical Power
- 0.000 dBm
- Assessment
- Very high power — check for receiver overload risk on short links.
Step by step
- 1Values used
- 2Power in dBm
- 3Optical Power= 0.000 dBm
- 4Assessment= Very high power — check for receiver overload risk on short links.
Assumptions and limits
- The result is derived only from the single input 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 3 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 too much optical power be a problem?
Yes — receivers have a maximum input power (overload threshold), typically around -3 dBm or higher for many SFP/SFP+ optics, beyond which the receiver's photodiode can saturate and cause errors, so short fiber runs sometimes need an attenuator even though power is technically 'plenty'.
What's a typical transmit power for SFP/SFP+ optics?
Many common single-mode and multimode SFP/SFP+ transceivers launch around -1 to +2 dBm, though DWDM and long-haul optics can launch significantly higher (often 0 to +7 dBm or more) to overcome greater fiber attenuation over distance.
Why is receiver sensitivity a negative dBm value?
Because it represents the minimum usable power, which after traveling through fiber and connectors is inevitably far less than 1 mW (0 dBm) — a more negative sensitivity number (e.g. -28 dBm vs -17 dBm) means a more sensitive receiver that can detect a weaker signal.
How do I use this alongside a fiber loss budget?
Measure or estimate your transmitter's launch power in dBm here, then use the Fiber Loss Budget or Optical Budget calculators to see whether the resulting received power, after subtracting expected losses, stays comfortably above your receiver's sensitivity floor.