High frequency multifractality in return intervals from fading induced by turbulence

In this work, we study the multifractal properties of the return intervals between fading events defined as laser intensity drops induced by optical turbulence. A laboratory-controlled experiment was conducted in which the irradiance fluctuations were recorded at a high sampling rate. Return intervals were obtained by identifying fading events under a threshold defined in times of the standard deviation of the measured irradiance. Using multifractal detrended fluctuation analysis, we found a crossover between two different scaling regimes: a spurious multifractal slightly correlated at small scales and a monofractal correlated for large scales. Based on a surrogate analysis and numerical simulations of monofractal processes, we conclude the heavy tail of the probability distribution of the return interval is the origin of the multifractality observed at small scales.