Experimental setup of the SD-OCT system

This image shows the experimental setup of the SD-OCT system by using the proposed integrated spectrometer. Light from superluminescent diode (SLD) was sent to a 50:50 fiber coupler (FC) and the two output beams went to the reference arm and sample arm, respectively. In the reference arm, the light launched from the single mode fiber was first collimated by a collimator and then hit the coated silver mirror. In the sample arm, after being collimated by the collimator, light then went through the galvo system and was focused by the scan lens on the sample. The reflected light from the reference arm and sample arm recombined and formed interference pattern in spectral domain after passing through the 50:50 FC. The interference signals passed through the polarization controller (PC) and then was coupled to the on-chip integrated spectrometer for measurement by fiber-chip grating coupler. The photocurrents from individual spectrometer channels were measured by connecting 1 MΩ resistors and measuring the output voltages by using analog-to-digital converter (ADC) card