Studies have proven the relationship between cutaneous vasculature abnormalities and dermatological disorders, but to image vasculature noninvasively in vivo, advanced optical imaging techniques are required. In this study, we imaged a palm of a healthy volunteer and three subjects with cutaneous abnormalities with photoacoustic tomography (PAT) and optical coherence tomography with angiography extension (OCTA). Capillaries in the papillary dermis that are too small to be discerned with PAT are visualized with OCTA. From our results, we speculate that the PA signal from the palm is mostly from hemoglobin in capillaries rather than melanin, knowing that melanin concentration in volar skin is significantly smaller than that in other areas of the skin. We present for the first time OCTA images of capillaries along with the PAT images of the deeper vessels, demonstrating the complementary effective imaging depth range and the visualization capabilities of PAT and OCTA for imaging human skin in vivo. The proposed imaging system in this study could significantly improve treatment monitoring of dermatological diseases associated with cutaneous vasculature abnormalities.
We demonstrate a scheme for the interrogation of arrays of FBG sensors based on a Swept Laser Distributed Sensing
system which can achieve 1000 sensors or more in a single fiber, while retaining the sensitivity and repeatability
expected with FBG sensors of better than 0.5 μepsilon and 0.05 C. The system utilizes an ‘akinetic’ wavelength swept source
and an arrival time-dependent detection approach to allow potentially 1000s of very low reflectivity FBGs to be
monitored via a form of Wavelength-to-Time Domain Reflectometry. We demonstrate the interrogation of 250 gratings
in a system architecture designed to support 1000 gratings.
We demonstrate a new swept-wavelength laser for optical coherence tomography using a monolithic semiconductor
device with no moving parts. The laser is based on a Vernier-Tuned Distributed Bragg Reflector (VTDBR) structure. We
show highly-linear sweeps at 200 kHz sweep repetition rates, with peak output power of 20 mW. Using a test
interferometer, we demonstrate point-spread functions with 45-55 dB dynamic range. The source provides long
coherence length (> 40mm) at up to 200 kHz sweep rates. The laser system has sufficient linearity in optical frequency
and stability over time to provide an electronic sample trigger clock (an Electronic K-Clock) that denotes equal optical
frequency intervals during the sweep. The laser tuning mechanism is all-electronic, easily adjustable and programmable.
We demonstrate both flat and Gaussian power vs. wavelength profiles, programmable sweep rates with the same device,
and an adjustable duty cycle of up to 85% at full speed. Because the laser is a monolithic semiconductor structure based
on reliable, wafer-scale processes, the manufacturing cost of the laser will decrease rapidly in volume production.
A novel swept-wavelength laser for optical coherence tomography (OCT) using a monolithic semiconductor device with
no moving parts is presented. The laser is a Vernier-Tuned Distributed Bragg Reflector (VT-DBR) structure exhibiting a
single longitudinal mode. All-electronic wavelength tuning is achieved at a 200 kHz sweep repetition rate, 20 mW
output power, over 100 nm sweep width and coherence length longer than 40 mm. OCT point-spread functions with 45-
55 dB dynamic range are demonstrated; lasers at 1550 nm, and now 1310 nm, have been developed. Because the laser's
long-term tuning stability allows for electronic sample trigger generation at equal k-space intervals (electronic k-clock),
the laser does not need an external optical k-clock for measurement interferometer sampling. The non-resonant, allelectronic
tuning allows for continuously adjustable sweep repetition rates from mHz to 100s of kHz. Repetition rate
duty cycles are continuously adjustable from single-trigger sweeps to over 99% duty cycle. The source includes a
monolithically integrated power leveling feature allowing flat or Gaussian power vs. wavelength profiles. Laser
fabrication is based on reliable semiconductor wafer-scale processes, leading to low and rapidly decreasing cost of
manufacture.
We propose that without rapid advances, optical testing of optical components will continue to be a major obstacle in the economical deployment of optical communications. We explore the communications-system drivers of these changes, the implications of these changes on the test process and apparatus, and identify certain obstacles which must be overcome. In some cases, solution paths are being identified, and we outline a number of these.
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