Supercontinuum sources in optical coherence tomography: how pulse-to-pulse fluctuations affect the noise performance

Supercontinuum sources are increasingly applied to spectral domain optical coherence tomography (OCT) due to their high power across octave-spanning bandwidths from the visible to the mid-infrared, enabling ultra-high resolution imaging with great flexibility in choice of operating wavelength region [1]. However, one of the main drawback of supercontinuum sources in OCT imaging is the large pulse-to-pulse fluctuations which often acts as the limiting factor in terms of sensitivity rather than the shot noise [2]. The theoretical noise description widely used by the OCT community assumes that the light source operation is based on spontaneous emission, which is not the case for supercontinuum laser source [3]. As a result, the optimal operating conditions must be evaluated experimentally without a reliable prediction [2,4]. Without a reliable theoretical noise model, optimization can be challenging. We present a new and simple noise model that allows prediction of the noise performance of an OCT system driven by a supercontinuum sources, without any assumptions regarding the type of light source. We show that the predictions are in excellent agreement with the experimental results obtained by employing a widely used commercial supercontinuum source. We further investigate the shape of the noise floor in an A-scan obtained with a commercial supercontinuum source, which is not flat, as expected for shot-noise limited light sources. We demonstrate that this shape is predicted solely by the spectral correlations of the supercontinuum, which therefore must be taken into account when characterizing the sensitivity of the OCT system driven by a supercontinuum source.