Low NEP balanced receivers generally do not result in better sensitivity in a shot-noise-limited swept source OCT system. However, there is an advantage if RIN is significant. A lower NEP, even in the shot-noise-limited case, does allow for lower reference arm powers. This, in turn, reduces fixed pattern artifact signals caused by stray optical component reflections inside a swept source laser cavity. An NEP reduction of √10 allows the reference power to be reduced 10 dB while maintaining SNR. This reduces the pattern to noise ratio by 10 dB because pattern noise is directly detected (20 dB scaling per decade reference power), whereas the image signal is heterodyne detected (10 dB scaling per decade of reference power). We present sensitivity and fixed pattern measurements taken with six commercial balanced receivers, including an APD receiver. We also present an NEP survey of 23 commercial receivers over a wide range of bandwidths and transimpedances.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.