Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Frequency-time coherence for all-optical sampling without optical pulse source.

ABSTRACT: Sampling is the first step to convert an analogue optical signal into a digital electrical signal. The latter can be further processed and analysed by well-known electrical signal processing methods. Optical pulse sources like mode-locked lasers are commonly incorporated for all-optical sampling, but have several drawbacks. A novel approach for a simple all-optical sampling is to utilise the frequency-time coherence of each signal. The method is based on only using two coupled modulators driven with an electrical sine wave. Since no optical source is required, a simple integration in appropriate platforms, such as Silicon Photonics might be possible. The presented method grants all-optical sampling with electrically tunable bandwidth, repetition rate and time shift.

SUBMITTER: Preußler S

PROVIDER: S-EPMC5043285 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Frequency-time coherence for all-optical sampling without optical pulse source.

Preußler Stefan S Raoof Mehrpoor Gilda G Schneider Thomas T

Scientific reports 20160930

Sampling is the first step to convert an analogue optical signal into a digital electrical signal. The latter can be further processed and analysed by well-known electrical signal processing methods. Optical pulse sources like mode-locked lasers are commonly incorporated for all-optical sampling, but have several drawbacks. A novel approach for a simple all-optical sampling is to utilise the frequency-time coherence of each signal. The method is based on only using two coupled modulators driven ...[more]

PMID: 27687495

Similar Datasets

Akinetic swept-source optical coherence tomography based on a pulse-modulated active mode locking fiber laser for human retinal imaging.

Project description:Optical coherence tomography (OCT) is a noninvasive imaging modality that can provide high-resolution, cross-sectional images of tissues. Especially in retinal imaging, OCT has become one of the most valuable imaging tools for diagnosing eye diseases. Considering the scattering and absorption properties of the eye, the 1000-nm OCT system is preferred for retinal imaging. In this study, we describe the use of an akinetic swept-source OCT system based on a pulse-modulated active mode locking (AML) fiber laser at a 1080-nm wavelength for in-vivo human retinal imaging. The akinetic AML wavelength-swept fiber laser was constructed with polarization-maintaining fiber that has an average linewidth of 0.625?nm, a spectral bandwidth of 81.15?nm, and duty ratio of 90% without the buffering method. We successfully obtained in-vivo human retinal images using the proposed OCT system without the additional k-clock and the frequency shifter that provides a wide field of view of 43.1°. The main retina layers, such as the retinal pigment epithelium, can be distinguished from the OCT image with an axial resolution of 6.3 ?m with this OCT system.

| S-EPMC6281618 | biostudies-literature

Complex conjugate resolved heterodyne swept source optical coherence tomography using coherence revival.

Project description:We describe a simple and low-cost technique for resolving the complex conjugate ambiguity in Fourier domain optical coherence tomography (OCT) that is applicable to many swept source OCT (SSOCT) systems. First, we review the principles of coherence revival, wherein an interferometer illuminated by an external cavity tunable laser (ECTL) exhibits interference fringes when the two arms of the interferometer are mismatched by an integer multiple of the laser cavity length. Second, we report observations that the spectral interferogram obtained from SSOCT systems employing certain ECTLs are automatically phase modulated when the arm lengths are mismatched this way. This phase modulation results in a frequency-shifted interferogram, effectively creating an extended-depth heterodyne SSOCT system without the use of acousto-optic or electro-optic modulators. We suggest that this phase modulation may be caused by the ECTL cavity optical pathlength varying slightly over the laser sweep, and support this hypothesis with numerical simulations. We also report on the successful implementation of this technique with two commercial swept source lasers operating at 840nm and 1040nm, with sweep rates of 8kHz and 100kHz respectively. The extended imaging depth afforded by this technique was demonstrated by measuring the sensitivity fall-off profiles of each laser with matched and mismatched interferometer arms. The feasibility of this technique for clinical systems is demonstrated by imaging the ocular anterior segments of healthy human volunteers.

| S-EPMC3296548 | biostudies-literature

Optical sampling depth in the spatial frequency domain.

Project description:We present a Monte Carlo (MC) method to determine depth-dependent probability distributions of photon visitation and detection for optical reflectance measurements performed in the spatial frequency domain (SFD). These distributions are formed using an MC simulation for radiative transport that utilizes a photon packet weighting procedure consistent with the two-dimensional spatial Fourier transform of the radiative transport equation. This method enables the development of quantitative metrics for SFD optical sampling depth in layered tissue and its dependence on both tissue optical properties and spatial frequency. We validate the computed depth-dependent probability distributions using SFD measurements in a layered phantom system with a highly scattering top layer of variable thickness supported by a highly absorbing base layer. We utilize our method to establish the spatial frequency-dependent optical sampling depth for a number of tissue types and also provide a general tool to determine such depths for tissues of arbitrary optical properties.

| S-EPMC6675966 | biostudies-literature

Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit.

Project description:Advances in swept source laser technology continues to increase the imaging speed of swept-source optical coherence tomography (SS-OCT) systems. These fast imaging speeds are ideal for microvascular detection schemes, such as speckle variance (SV), where interframe motion can cause severe imaging artifacts and loss of vascular contrast. However, full utilization of the laser scan speed has been hindered by the computationally intensive signal processing required by SS-OCT and SV calculations. Using a commercial graphics processing unit that has been optimized for parallel data processing, we report a complete high-speed SS-OCT platform capable of real-time data acquisition, processing, display, and saving at 108,000 lines per second. Subpixel image registration of structural images was performed in real-time prior to SV calculations in order to reduce decorrelation from stationary structures induced by the bulk tissue motion. The viability of the system was successfully demonstrated in a high bulk tissue motion scenario of human fingernail root imaging where SV images (512 × 512 pixels, n = 4) were displayed at 54 frames per second.

| S-EPMC3395481 | biostudies-other

Comparison of two swept-source optical coherence tomography biometers and a partial coherence interferometer.

Project description:PurposeTo compare biometry and prediction of postoperative refractive outcomes obtained by two swept-source optical coherence tomography (SS-OCT) biometers (IOLMaster 700 and Argos), and a partial coherence interferometry (IOLMaster ver 5.4).MethodsBiometric values were measured using two SS-OCT and PCI device and evaluated against one another. Predictive errors were compared at one month after cataract surgery.ResultsOne hundred forty six eyes were considered. Axial length (AXL) measurements were not successful in 3 eyes measured by IOLMaster 700 and Argos devices, and in 17 eyes measured by IOLMaster ver. 5.4 devices. AXL as measured by Argos showed a tendency to be shorter in long eyes with AXL more than 26.0 mm (p < .001) and to be longer in short eyes with AXL less than 22.5 mm (p = .005). Anterior chamber depth as measured by IOLMaster ver. 5.4 was longer than that measured by the other two SS-OCT devices (vs. IOLMaster 700: p = .003; vs. Argos: p = .006). White-to-white diameter measured using Argos was significantly different measurements obtained using two IOLMaster (p < .001, respectively). The mean absolute postoperative prediction errors were 0.41 ± 0.31 diopters (D), 0.42 ± 0.32 D, and 0.35 ± 0.30 D for IOLMaster ver. 5.4, IOLMaster 700, and Argos, respectively.ConclusionThe ocular biometric measurements using three devices showed high agreement. AXL measured by Argos showed a significant difference compared with the measurements from two IOLMaster. ACD was highly correlated between two SS-OCT devices except IOLMaster ver 5.4. LT and CCT values between IOLMaster 700 and Argos were different significantly. SS-OCT devices demonstrated a superior ability to successfully perform measurements compared with PCI device.

| S-EPMC6788676 | biostudies-literature

Comparison of choroidal thickness measurements between spectral domain optical coherence tomography and swept source optical coherence tomography in children.

Project description:Choroidal thickness is associated with many ocular conditions, interchangeability among different generations of optical coherence tomography is therefore important for both research purpose and clinical application. Hence, we compared choroidal thickness measurements between spectral-domain optical coherence tomography (SD-OCT) and swept-source optical coherence tomography (SS-OCT) in healthy paediatric eyes. A total of 114 children from the population-based Hong Kong Children Eye Study with mean age of 7.38 ± 0.82 years were included. Choroidal thickness of the right eye was measured by both devices. The central foveal choroidal thickness (CFCT) measured by SD-OCT and SS-OCT was 273.24 ± 54.29 μm and 251.84 ± 47.12 μm respectively. Inter-device correlation coefficient was 0.840 (95% CI 0.616-0.918). However, choroidal thickness obtained by SD-OCT was significantly thicker than that measured by SS-OCT with a mean difference of 21.40 ± 33.13 μm (P < 0.001). Bland-Altman limit of agreement on the relative difference scale for SD-OCT/SS-OCT was 86.33 μm. Validated conversion equation for translating SD-OCT CFCT measurement into SS-OCT was SS-OCT = 35.261 + 0.810 × SD-OCT. In conclusion, intra-class correlation coefficient (ICC) shows an acceptable agreement between SD-OCT and SS-OCT, however, there was a significant inter-device difference of choroidal thickness measurements in normal children eyes. Therefore, the measurements are not interchangeable.

| S-EPMC8253773 | biostudies-literature

Choroidal Neovascularization Analyzed on Ultrahigh-Speed Swept-Source Optical Coherence Tomography Angiography Compared to Spectral-Domain Optical Coherence Tomography Angiography.

Project description:To compare visualization of choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) using an ultrahigh-speed swept-source (SS) optical coherence tomography angiography (OCTA) prototype vs a spectral-domain (SD) OCTA device.Comparative analysis of diagnostic instruments.Patients were prospectively recruited to be imaged on SD OCT and SS OCT devices on the same day. The SD OCT device employed is the RTVue Avanti (Optovue, Inc, Fremont, California, USA), which operates at ?840 nm wavelength and 70 000 A-scans/second. The SS OCT device used is an ultrahigh-speed long-wavelength prototype that operates at ?1050 nm wavelength and 400 000 A-scans/second. Two observers independently measured the CNV area on OCTA en face images from the 2 devices. The nonparametric Wilcoxon signed rank test was used to compare area measurements and P values of <.05 were considered statistically significant.Fourteen eyes from 13 patients were enrolled. The CNV in 11 eyes (78.6%) were classified as type 1, 2 eyes (14.3%) as type 2, and 1 eye (7.1%) as mixed type. Total CNV area measured using SS OCT and SD OCT 3 mm × 3 mm OCTA were 0.949 ± 1.168 mm(2) and 0.340 ± 0.301 mm(2), respectively (P = .001). For the 6 mm × 6 mm OCTA the total CNV area using SS OCT and SD OCT were 1.218 ± 1.284 mm(2) and 0.604 ± 0.597 mm(2), respectively (P = .0019). The field of view did not significantly affect the measured CNV area (P = .19 and P = .18 for SS OCT and SD OCT, respectively).SS OCTA yielded significantly larger CNV areas than SD OCTA. It is possible that SS OCTA is better able to demarcate the full extent of CNV vasculature.

| S-EPMC4811690 | biostudies-literature

Choroid structure analysis following initiation of hemodialysis by using swept-source optical coherence tomography in patients with and without diabetes.

Project description:We aimed to evaluate choroid structural changes using swept-source optical coherence tomography (SS-OCT) following hemodialysis initiation in diabetic and nondiabetic patients with end-stage kidney disease (ESKD). In this multicenter, prospective, cross-sectional study, diabetic (DM group; 30 eyes; 16 patients) and nondiabetic patients (NDM group; 30 eyes; 15 patients) with ESKD were evaluated after hemodialysis initiation. SS-OCT findings were analyzed using a manual delineation technique and binarization method before the first and last hemodialysis sessions, conducted approximately 2 weeks apart. Subfoveal choroidal thickness changes and mean large choroidal vessel layer thickness were significantly greater in the DM group (-13.3% ± 2.5% and -14.5% ± 5.2%, respectively) than the NDM group (-9.5% ± 3.1% and -9.2% ± 3.4%, respectively; p = 0.049 and p = 0.02, respectively). Binarized SS-OCT analysis revealed that the mean subfoveal choroidal area was significantly larger in the DM group (-21.9% ± 6.5%) than the NDM group (-17.2% ± 5.9%; p = 0.032). The change ratio in mean luminal area values was significantly greater in the DM group (-27.7% ± 8.7%) than the NDM group (-17.7% ± 5.8%; p = 0.007). The DM group exhibited substantial changes in the choroidal layer, possibly reflecting choroidal vascular disorders caused by diabetes.

| S-EPMC7485894 | biostudies-literature

Real-time high-resolution mid-infrared optical coherence tomography.

Project description:The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4?µm and an axial resolution of 8.6?µm is demonstrated. The system produces two-dimensional cross-sectional images in real time enabled by a high-brightness 0.9- to 4.7-µm mid-infrared supercontinuum source with a pulse repetition rate of 1?MHz for illumination and broadband upconversion of more than 1-µm bandwidth from 3.58-4.63?µm to 820-865?nm, where a standard 800-nm spectrometer can be used for fast detection. The images produced by the mid-infrared system are compared with those delivered by a state-of-the-art ultra-high-resolution near-infrared optical coherence tomography system operating at 1.3??m, and the potential applications and samples suited for this technology are discussed. In doing so, the first practical mid-infrared optical coherence tomography system is demonstrated, with immediate applications in real-time non-destructive testing for the inspection of defects and thickness measurements in samples that exhibit strong scattering at shorter wavelengths.

| S-EPMC6342823 | biostudies-literature

Real-time compressive sensing spectral domain optical coherence tomography.

Project description:We developed and demonstrated real-time compressive sensing (CS) spectral domain optical coherence tomography (SD-OCT) B-mode imaging at excess of 70 fps. The system was implemented using a conventional desktop computer architecture having three graphics processing units. This result shows speed gain of 459 and 112 times compared to the best CS implementations based on the MATLAB and C++, respectively, and that real-time CS SD-OCT imaging can finally be realized.

| S-EPMC4114772 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data