Relative intensity noise (RIN), describes the instability in the power level of a laser.
The noise term is important to describe lasers used in fiber-optic communication and LIDAR remote sensing.
Hence, when the signal to noise ratio (SNR) is limited by RIN, it does not depend on laser power.
In contrast, when SNR is limited by shot noise, it improves with increasing laser power.
It may also be specified as a percentage, a value that represents the relative fluctuations per Hz multiplied by the RIN bandwidth.