Noise-equivalent power

Noise-equivalent power (NEP) is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal-to-noise ratio of one in a one hertz output bandwidth. An output bandwidth of one hertz is equivalent to half a second of integration time. The units of NEP are watts per square root hertz. The NEP is equal to the noise spectral density (expressed in units of ${\displaystyle \mathrm {A} /{\sqrt {\mathrm {Hz} }}}$ or ${\displaystyle \mathrm {V} /{\sqrt {\mathrm {Hz} }}}$) divided by the responsivity (expressed in units of ${\displaystyle \mathrm {A} /\mathrm {W} }$ or ${\displaystyle \mathrm {V} /\mathrm {W} }$, respectively).

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