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

• Published in: Journal of lightwave technology 2020-12, Vol.38 (23), p.6492-6498
• Main Authors: Shirahata, Takuma, Set, Sze Y., Yamashita, Shinji
• Format: Article
• Language: English
• Subjects: Coherence; Coherence length; Compensation; Digital imaging; Dispersion tuning; fiber laser; Fiber lasers; Frequency modulation; Image acquisition; Laser tuning; Nonlinearity; optical coherence tomography; Optical interferometry; Point spread functions; Signal processing; swept-source; Tunable filters; Uncertainty; Vertical cavity surface emitting lasers
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2020.3013104

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.