We report experimental evidence of a novel method to quench the resonances of a Fabry-Perot tunable filter typically
used as a wavelength selective element in swept source OCT systems. The method is based on applying a non-sinusoidal,
synthesized waveform to the tunable filter, waveform that can be found experimentally in a few iteration steps. A
significant improvement in the OCT image quality has been obtained without any software recalibration method.
We report the development of a swept wavelength laser at 1 micron based on a linear cavity fibre configuration with an
intra-cavity half symmetrical confocal Fabry-Perot tunable filter and a semiconductor optical amplifier as a gain
medium. The performances of the source in terms of parameters like: sweep repetition rate (1-20 kHz), center
wavelength (1065 nm), wavelength scanning range (max. 50nm), instantaneous line-width (<0.1nm) and a boosted
output power of around 40 mW are demonstrated. The new source tested on an OCT system is exhibiting sufficient
linearity in wave-number (k-space) at 1 kHz repetition rate; therefore no k-trigger, or wavelength rescaling process was
needed.
Optical coherence tomography (OCT) imaging at 1060 nm region proved to be a successful alternative in ophthalmology
not only for resolving intraretinal layers, but also for enabling sufficient penetration to monitor the sub-retinal
vasculature in the choroids when compared to most commonly used OCT imaging systems at 800 nm region. To
encourage further clinical research at this particular wavelength, we have developed a compact fiber optic source based
on amplified spontaneous emission (ASE) centered at ~1060 nm with ~70 nm spectral bandwidth at full-width half
maximum (FWHM) and output power >20 mW. Our approach is based on a combination of slightly shifted ASE
emission spectra from a combination of two rare-earth doped fibers (Ytterbium and Neodymium). Spectral shaping and
power optimization have been achieved using in-fiber filtering solutions. We have tested the performances of the source
in an OCT system optimized for this wavelength.
Recent developments on broadband optical sources emitting at 1050 nm wavelength for medical applications, in particular optical coherence tomography (OCT), have revealed enhanced depth penetration into the choroid, reduced scattering losses and improved image performances in eyes with turbid media, when compared to the most commercial
used semiconductor optical source technology at 820 nm. In this paper, we present our study of fibre optic broadband sources (BBS) at 1 micron region, based on the amplified spontaneous emission (ASE) from rare-earth doped silica fibres for the integration into OCT systems. The target specifications for this type of sources are: 1050 nm central emission wavelength, with spectral width of ~70 nm, tens of miliwatts of output power and smoothly shaped output
spectra. Several combinations of rare-earth doped optical fibres integrated into different fibre optic configurations have
been tested. Optical bandwidth optimization and spectral shaping using different fibre optic techniques are presented and
their autocorrelation function compared.
A new approach of acquiring quasi-simultaneous optical coherence tomography (OCT) and confocal images is presented. The two images are generated using different principles, OCT and confocal microscopy. When the system is used to image the retina, the two images have depth resolutions, at present, of <20 µm and ~1 mm, respectively. The acquisition and display of en face OCT and confocal images are quasi-simultaneous, without the need of a beamsplitter. By using a chopper to periodically obstruct the reference beam in the OCT interferometer, synchronized with the XY-transversal scanner, much higher acquisition speed is obtained than in a previous report where we flipped an opaque screen in the reference arm of the interferometer. Successful operation of the novel configuration was achieved by: (1) stable synchronization of the chopper's movement with the horizontal line scanner and (2) fast self-adjusting of the gain value of avalanche photodiodes, depending on the optical power. Images from coin, leaves, and retina in vivo have been collected to demonstrate the functionality of the system.
A new approach of acquiring quasi-simultaneous OCT and confocal images is presented. The two images are generated
using different principles, optical coherence tomography (OCT) and confocal microscopy (CM). When the system is
used to image the retina, the two images have depth resolutions, at present, of less than 20 μm and approximately 1 mm
respectively. The acquisition and display of en-face OCT and confocal images are quasi-simultaneous, without the need
of a beam splitter. By using a chopper to periodically obstruct the reference beam in the OCT interferometer,
synchronized with the XY-transversal scanner, much higher acquisition speed is obtained than in a previous report where
we flipped an opaque screen in the reference arm of the interferometer. Successful operation of the novel configuration
was achieved by: (1) stable synchronization of the chopper's movement with the horizontal line scanner and (2) fast self-adjusting
of the gain value of avalanche photodiodes depending on the optical power. Images from coin, leafs and retina in vivo have been collected to demonstrate the functionality of the system.
The authors report investigations into the suitability of a broadband supercontinuum fiber laser (SCFL) for use in Optical
Coherence Tomography (OCT). The supercontinuum of light extending from 400 nm to 1800 nm can be used selectively
in several spectral wavebands from 600 nm to 1700 nm in order to characterize the performance of single mode (SM)
fiber OCT systems through spectral and auto-correlation measurements, dispersion measurements and image acquisition.
Spectral selection and tailoring is made possible through a combination of bandpass optical filters. In addition, for the
first time, given the optical bandwidth available, we perform evaluation of effective noise bandwidths which take into
consideration the spectral behavior of the optical splitter in the balanced detection receiver.
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