Fpc030

Here a spectral‐domain OCT system was used as the 3D imaging platform for the placenta villi's three‐dimensional morphological revealing, as Figure 2 shows. The spectral‐domain OCT setup used a superluminescent diode‐based broadband light source (cBLMD‐T‐850‐HP, Superlum) with a center wavelength of 855 nm and a 160 nm bandwidth, a 2048‐pixel spectrometer (Cobra‐S 800, Wasatch Photonics), a 2‐axis scanning galvanometer scanner (GVSM002‐EC/M, Thorlabs), a 2 × 2 850‐nm wideband fiber optic coupler (TW850R5A2, Thorlabs), two identical collimators (TC25APC‐850, Thorlabs), and two polarization controllers (FPC030, Thorlabs), one for the sample arm and one for the reference arm. 4× objective (Olympus) lens was configured when imaging samples. The axial and transverse optical resolutions were ~2.3 μm in air and ~6.9 μm, respectively. The OCT imaging exposure time 𝑡_𝑒 used was 25.0 μs, and both the A‐scan number per B‐scan and B‐scan number used were 800. The light power on the sample was ~8.9 mW and the sensitivity of the OCT system was ~102 dB. The maximum imaging depth into the villi was ~1.7 mm.