A optical fiber coupler recombines the light backscattered from the sample and reflected from the reference mirror. This combined beam is routed to a purpose-built, high-speed spectrometer via the optical circulator. The spectrometer consists of a 30-mm focal length collimator, a transmission grating, an achromatic lens with 100 mm focal length, and a 12-bit, 4096-pixel CMOS line-scan camera (Basler Sprint spL4096-140 km), of which only 2048 pixels are used, to reduce data-acquisition time. To improve the signal-to-noise ratio, we use vertical binning as well as horizontal binning, both over 2 pixels, which effectively yields 1024 pixels. The maximum line-scan rate of the camera is 140 kHz. We use a reduced sample rate of 10 kHz to improve the signal-to-noise ratio, as the maximum frequency of interest is in this study.