To benchmark the intensity noise levels of different sources, a supercontinuum source (WhiteLase Micro, Fianium), an SLD (Broadlighter D840, Superlum), and a swept source (Santec, HSL-2100-WR) have been studied. To measure the source intensity noise, only the reference arm is used. A variable neutral density filter (VNDF), which was placed before the input of the detector in order to avoid stray light or any potential light leakage, was used to adjust the level of light incidence on the detector in the context of noise measurements as a function of the overall light power. Readings from one chosen pixel or time stamp were recorded for a fixed light intensity level, from which the mean and variance of the digital number were calculated. Then as we adjusted the position of the VNDF, the intensity of the light reaching the detector monotonically increased. After quantifying the mean and the corresponding variance at different light intensity levels, the relation of the variance of the power spectrum versus its mean value is plotted in Fig. 2, for a supercontinuum, a swept source, and an SLD, respectively. The coefficients , , of the curves were evaluated for each source and are listed in Table 1. The results show that the SLD has the least intensity noise, followed by the swept source, and then the supercontinuum. It is important to note that, besides the intensity noise, the swept source may suffer from trigger jittering, which may impose an uncertainty in the wavelength, and thus affect its performance in thickness estimation. The following section discusses the swept source in two cases: (1) in the best scenario, an ideal swept source is considered with only intensity noise and (2) a swept source, in a real lab setting, is investigated with trigger jittering noise.