Enter for the full results page · Esc to close
Decibels are convenient to add up but hard to feel. This converts insertion loss in dB into the fraction of power that survives — and back again — so you can see what a 3 dB splitter or a 0.35 dB connector really costs you.
What the numbers mean. Loss in dB is −10·log₁₀(P_out ÷ P_in). Because it is logarithmic, small dB numbers are worth more than they look at the top of the scale and less at the bottom: 0.35 dB — a good connector — costs you about 8% of the light, while 3 dB costs exactly half.
Numbers worth memorising. 0.1 dB ≈ 2.3% lost. 0.5 dB ≈ 11%. 1 dB ≈ 21%. 3 dB = 50% — exactly half. 10 dB = 90% lost. 20 dB = 99%. 30 dB = 99.9%. Those seven values cover almost every insertion-loss conversation you will have.
Splitters. An ideal 1×N splitter divides the power N ways, which is 10·log₁₀(N) dB: 3 dB for 1×2, 6 dB for 1×4, 9 dB for 1×8, 12 dB for 1×16. Real PLC splitters add roughly 0.5–1.5 dB of excess loss on top of the theoretical split.
Yes — it is the specified maximum for a quality factory-terminated single-mode connector, and it means about 92% of the light gets through. Extra-low-loss grades are specified at 0.25 dB or better. Field-terminated connectors typically land between 0.5 and 0.75 dB.
Because 10^(−3/10) = 0.501. It is not exactly a half — it is 50.12% — but the difference is far below anything you can measure, so the industry treats 3 dB and half power as the same thing.
The arithmetic is the same but the sign convention is reversed: return loss is quoted as a positive number you want to be large. 60 dB return loss means one millionth of the light comes back, which is why APC connectors are specified at ≥ 60 dB and flat UPC at ≥ 50 dB.
Convert optical power between logarithmic and linear units, in both directions
Open tool →Total channel loss, power budget and pass/fail margin for single-mode and multimode links
Open tool →ITU channel number ⇄ frequency ⇄ wavelength, for 100/50/25/12.5 GHz DWDM and the 20 nm CWDM grid
Open tool →Transceivers, MPO assemblies, WDM and patch cords — built and tested to the figures you just calculated.