Optical coherence tomography (OCT) has been utilized for various functional imaging applications. One of its
highlights comes from spectroscopic imaging, which can simultaneously obtain both morphologic and spectroscopic
information. Assisting diagnosis and therapeutic intervention of coronary artery disease is one of the major
directions in spectroscopic OCT applications. Previously Tanaka et al. have developed a spectral domain OCT (SDOCT)
to image lipid distribution within blood vessel . In the meantime, Fleming et al. have demonstrated optical
frequency domain imaging (OFDI) by a 1.3-μm swept source and quadratic discriminant analysis model .
However, these systems suffered from burdensome computation as the optical properties’ variation was calculated
from a single-band illumination that provided limited contrast. On the other hand, multi-band OCT facilitates
contrast enhancement with separated wavelength bands, which further offers an easier way to distinguish different
materials. Federici and Dubois  and Tsai and Chan  have demonstrated tri-band OCT systems to further
enhance the image contrast. However, these previous work provided under-explored functional properties.
Our group has reported a dual-band OCT system based on parametrically amplified Fourier domain mode-locked
(FDML) laser with time multiplexing scheme  and a dual-band FDML laser OCT system with wavelength-division
multiplexing . Fiber optical parametric amplifier (OPA) can be ideally incorporated in multi-band
spectroscopic OCT system as it has a broad amplification window and offers an additional output range at idler
band, which is phase matched with the signal band. The sweeping ranges can thus overcome traditional wavelength
bands that are limited by intra-cavity amplifiers in FDML lasers. Here, we combines the dual-band FDML laser
together with fiber OPA, which consequently renders a simultaneous tri-band output at 1.3, 1.5, and 1.6 μm, for
intravascular applications. Lipid and blood vessel distribution can be subsequently visualized with the tri-band OCT
system by ex vivo experiments using porcine artery model with artificial lipid plaques.
A tri-band spectroscopic optical coherence tomography (SOCT) system has been implemented for visualization of lipid and blood vessel distribution. The tri-band swept source, which covers output spectrum in 1.3, 1.5, and 1.6 μm wavelength windows, is based on a dual-band Fourier domain mode-locked laser and a fiber optical parametric amplifier. This tri-band SOCT can further differentiate materials, e.g., lipid and artery, qualitatively by contrasting attenuation coefficients difference within any two of these bands. Furthermore, ex vivo imaging of both porcine artery with artificial lipid plaque phantom and mice with coronary artery disease were demonstrated to showcase the capability of our SOCT.
Dual-band optical coherence tomography (OCT) can greatly enhance the imaging contrast with potential applications in functional (spectroscopic) analysis. A new simultaneous dual-band Fourier domain mode-locked swept laser configuration for dual-band OCT is reported. It was based on a custom-designed dual-channel driver to synchronize two different wavelength bands at 1310 and 1550 nm, respectively. Two lasing wavelengths were swept simultaneously from 1260 to 1364.8 nm for the 1310-nm band and from 1500 to 1604 nm for the 1550-nm band at an A-scan rate of 45 kHz. Broadband wavelength-division multiplexing was utilized to couple two wavelength bands into a common catheter for circumferential scanning to form dual-band OCT. The proposed dual-band OCT scheme was applied to endoscopic OCT imaging of mouse esophageal wall ex vivo and human fingertip in vivo to justify the feasibility of the proposed imaging technique. The proposed dual-band OCT system is fast and easy to be implemented, which allows for in vivo high-speed biomedical imaging with potential applications in spectroscopic investigations for endoscopic imaging.