Group-delay-based phase-shifting method for Fourier domain optical coherence tomography

Frequency-domain optical coherence tomography (FD-OCT) has the advantages of an improved sensitivity and a reduced acquisition time since it enables cross-sectional images of the sample of interest to be obtained using a broadband source or a swept source. The phase-shifting method can always be applied to reduce the additional noise within FD-OCT and provide accurate signal processing. We present a phase-shifting method in which a parallel diffraction grating pair is inserted into the reference arm of the OCT system. The gratings separate the spectrum of the illuminating light and stretch the optical pulse in time thereby producing a linear group delay between the adjacent wavelengths in the superluminescent diode light source. The simulation results show that the proposed group-delay-based phase-shifting method improves the precision of the sample parameters extracted using the FD-OCT procedure compared to those obtained using traditional techniques such as the 0/4 phase-shifting method.