Appendix. Units of Optical Power Measurement: Decibel
The power level in optical fiber communications is too wide ranged to express on a linear scale. A logarithmic scale known as decibel (dB) is used to express power in optical communications. The wide range of power values makes the decibel a convenient unit to express the power levels that are associated with an optical system. The gain of an amplifier or attenuation in fiber is expressed in decibels. The decibel does not give a magnitude of power, but it is a ratio of two powers. See the following equation:
Example:
Calculate the gain of the amplifier in dB, when 1 watt is applied to the input ...
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