Compensation of Phase-Uncertainty-Induced Impairments in Dispersion-Tuned Swept Laser OCT using Digital Coherent Detection

The dispersion-tuned swept laser (DTSL) is a wavelength-swept source, which can achieve fast sweep without using any mechanical tunable filter. Such fast wavelength-swept sources are highly suitable for swept-source optical coherent tomography (SS-OCT). DTSL-based SS-OCT (DTSL-OCT) can deliver a very fast imaging speed, however, it suffers from a limited imaging depth due to the its limited coherence length. In this article, digital coherent detection techniques are applied to the DTSL-OCT to improve the imaging depth and axial resolution. We show that the two phase-uncertainty-induced impairments, namely, the image degeneracy and the wavelength-sweep-nonlinearity, can be compensated by signal processing on the complex interferometric signals acquired using digital coherent detector. Removal of the mirror images resulting from complex conjugate artifact enables the full-range measurement, and the wavelength-sweep-nonlinearity compensation improves the axial resolution. We experimentally demonstrated that the OPD corresponding to a 6 dB-drop in the point-spread function (PSF) peak level can be improved from 1.4 mm to 7.2 mm.