Instantaneous complex conjugate resolved spectral domain and swept-source OCT using 3×3 fiber couplers

We report that the complex conjugate artifact in Fourier domain optical coherence tomography approaches (including spectral domain and swept source OCT) may be resolved by the use of novel interferometer designs based on 3×3 and higher order fiber couplers. Interferometers built from N×N (N>2) truly fused fiber couplers provide simultaneous access to non-complementary phase components of the complex interferometric signal. These phase components may be converted to quadrature components by trigonometric manipulation, then inverse Fourier transformed to obtain A-scans and images with resolved complex conjugate artifact. We demonstrate instantaneous complex conjugate resolved Fourier domain OCT using 3×3 couplers in both spectral domain and swept source implementations. Complex conjugate artifact suppression by factors of ~20 dB and ~25 dB are demonstrated for spectral domain and swept source implementations, respectively