What absolute power value is Zero dBm referenced to?

Zero dBm is a reference point in the decibel scale specifically used in telecommunications and fiber optics to express power levels. The 'dBm' notation indicates that the power level is measured in decibels relative to 1 milliwatt (mW). Therefore, when a signal power level is stated as 0 dBm, it means that the power is exactly equal to 1 mW.

In practical terms, this reference is widely utilized in various contexts, such as when assessing the power output of laser sources in fiber optic systems or the sensitivity levels of detectors. The decibel (dB) scale itself is logarithmic, allowing for a convenient means to express large variations in power levels compactly. By referencing to 1 mW, it provides a standard benchmark for comparing various signal strengths and losses within optical networks.