Attenuation converter
Convert attenuation between dB per kilometer and the per-hundred-feet figures on cable datasheets.
That's about the same as single-mode fiber at 1550 nm. After about 50 km only a tenth of the power is left.
What it means
How lossy is that?
Cable loss rises with frequency, so a datasheet figure always belongs to a stated frequency. Fiber loss depends on the wavelength instead.
Every unit
Your attenuation in every unit
Learn
Three things worth knowing
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3 dB means half the power
So a run long enough to cost 3 dB has thrown away half your signal. At 0.2 dB/km, that takes 15 km of fiber.
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Why per hundred feet
US cable was sold in hundred-foot reels, so the loss was quoted per reel. The unit outlived the packaging.
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Loss depends on frequency
A coaxial cable rated 20 dB/100 m at 100 MHz may lose 70 dB/100 m at 1 GHz. Quoting attenuation without the frequency says almost nothing.
Shortcuts
Popular attenuation conversions
Background
About attenuation
Attenuation is loss per unit length, in decibels. Single-mode fiber at 1550 nm loses about 0.2 dB/km, which is why a signal can cross an ocean. Coaxial cable at radio frequencies loses that much in a few meters.