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.