Figure 1 shows a sample setup of the INT-MSI-1300B in a Time Domain OCT system. The incoming broadband light source, which has a central wavelength of 1300 nm, passes through a circulator and a broadband 50/50 fusion coupler. Back-reflected light from both the sample and reference arms of the interferometer are combined in the 50/50 fusion coupler, generating the interference fringe signals that pass through the circulator and the WDM coupler to the inputs of the balanced detector. The balanced detector output signal is acquired by the data acquisition device and processed to obtain the reconstructed OCT image. Figure 2 is a schematic showing how the IN-MSI-1300B can be incorporated into a frequency domain OCT system by replacing the translating mirror on the end of the reference arm with a fixed mirror.
Figure 1: Schematic of the INT-MSI-1300B in a Time Domain OCT Design
Figure 2: Schematic of the INT-MSI-1300B in a Sample Fourier Domain OCT Design
The internal fiber length of both arms of the interferometer match to within 0.2 mm, while the optical path lengths between the 50/50 fusion coupler and the inputs of the balanced detector are also matched to achieve optimal noise suppression (i.e., the maximum common mode rejection ratio CMRR). The internal couplers are optimized for flat wavelength response and very low PDCR (polarization-dependant coupling ratio), which makes the detected signal nearly independent of input polarization changes. Figure 3 shows the percentage of the input power at the reference and sample ports. Equal power for both ports is measured at 1300 nm (center wavelength).
Figure 3: Coupling of the INT-MSI-1300B Measured From 1300 nm IN Port to the SAMPLE and REFERENCE ARM Ports