 Noise-equivalent power

Noise-equivalent power expresses detector noise as an equivalent incident radiant power. In a bandwidth-normalized convention, divide the output amplitude amplitude spectral density by spectral responsivity; the units are $\mathrm{W}\mathrm{H}{\mathrm{z}}^{-1/2}$. It is the incident signal scale giving unit signal-to-noise ratio in a $1\mathrm{Hz}$ noise-equivalent detection bandwidth.^[ref]

For approximately white noise, a bandwidth $B$ gives equivalent rms radiant power $\mathrm{NEP}\sqrt{B}$. Thus $10^{-12}\mathrm{W}\mathrm{H}{\mathrm{z}}^{-1/2}$ over $100\mathrm{Hz}$ corresponds to $10^{-11}\mathrm{W}$. State the wavelength, operating conditions and bandwidth: a bandwidth-normalized specification is not itself a universal minimum detectable energy.

Noise-equivalent power (NEP) is a key parameter used to describe the sensitivity of a detector or sensor, often in the context of optical and infrared detectors. It quantifies the minimum power of an incoming signal that can be reliably detected above the noise level of the system. Specifically, NEP is defined as the incident power of a signal that produces a signal-to-noise ratio (SNR) of one when integrated over a given bandwidth.