All measurement systems have a resolution limited by random fluctuations (noise) or by variations in parameters with time (drift). The Allan deviation statistical method allows different noise and drift types to be readily identified at various timescales.

We have used the Allan deviation method to measure the noise and drift in the power of a supercontinuum laser with and without power-stabilisation feedback control.

The Allan deviation method clearly shows that the feedback control removes drift. The random uncertainty in the mean stabilized laser power, determined using the Allan deviation method, is <0.01 % for averaging times longer than 100 s.

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