Sensitivity Investigation of Instantaneous Complex Conjugate Resolved Swept-Source OCT Using a Mach-Zehnder Interferometer with a 3×3 Fiber Coupler

摘要

We present an instantaneous complex conjugate resolved swept-source optical coherence tomography (SS-OCT) using a 3×3 optical fiber coupler. A dual-channel balanced (dual-balanced) detection with phase shifted signals was formed by a Mach-Zehnder interferometer (MZI) with a 3×3 and one or more 2×2 optical fiber couplers. Non-complementary phase components of the complex interferometric signals from the dual-balanced detector were converted to quadrature components by a simple trigonometric formula. A-scans with resolved complex conjugate artifact were obtained by inverse Fourier transformation. This approach provides a two times increase in the effective depth of image. Two configurations of the quadrature interferometers based on Mach-Zehnder interferometer (MZI) topology are investigated. The first configuration with one 3×3 and three 2×2 optical fiber couplers is arranged for DC signal removal, and the second configuration with one 3×3 and one 2×2 optical fiber couplers is organised for optical power optimisation. We focus on the comparison of the measured sensitivity and complex conjugate artifact suppression between the two configurations of the quadrature MZI SS-OCT system. The suppression of complex conjugate artifact of > 25 dB for the second configuration, i.e. 3×3 SS-OCT with one 2×2 fiber couplers, was obtained, which is 6 dB higher than that for the first configuration, i.e. 3×3 SS-OCT with three 2×2 coupler. The reason for the performance of the second configuration over the first one is the optimisation of the optical power handling. In the second configuration, the DC components of the complex interferometric signal caused by unequal optical power level have been removed by the balanced detection and DC noise subtraction.