Shot-noise limited optical hybrid based on fused fiber couplers

We describe a fiber-based coherent receiver topology which utilizes intrinsic phase shifts from fiber couplers to enable instantaneous quadrature projection with shot-noise limited signal-to-noise ratio (SNR). Fused 3x3 fiber couplers generate 3 phase-shifted signals simultaneously that can be combined with quadrature projection methods to detect magnitude and phase unambiguously. We present a novel differential detection topology which utilizes a combination of 3x3 and 2x2 couplers to enable quadrature projection with fully differential detection. We present a mathematical analysis of this 3x3 differential detection topology, extended methods for signal calibration, and SNR analysis. We characterize the SNR advantage of this approach and demonstrate a sample application illustrating simultaneous magnitude and phase imaging of a chrome-on-glass test chart

Features of the posterior vitreous and vitreoretinal interface observed in healthy eyes.

<p>Features of the posterior vitreous and vitreoretinal interface observed in healthy eyes.</p

Optical coherence tomography (OCT) images are typically displayed in logarithmic scale.

<p>Enhanced vitreous imaging with the vitreous window and high-dynamic-range methods improves visualization of structure in the posterior vitreous and vitreoretinal interface. Scale bars: 300 µm.</p

Vitreal detachment from the retina can be mapped in three-dimensional (3D) enhanced vitreous imaging volumetric datasets by examining each cross-sectional image in a 3D dataset (left) and marking the detached hyaloid (center) to generate a map where the area of vitreal detachment is highlighted (right).

<p>Vitreoretinal attachment is present at the macula (blue asterisk) and optic nerve head (yellow asterisk) as well as along a retinal vessel (red arrow) nasal to the optic nerve head. The measured areas of attachment are 20.9 mm² above the macula, 9.7 mm² over the optic nerve head, and 0.2 mm² along the retinal vessel within the imaging range. Scale bars: 300 µm.</p

Examples of features observed in the posterior vitreous and vitreoretinal interface in healthy eyes.

<p>Selected cross sections from two different eyes are shown with their locations marked on the optical coherence tomography (OCT) fundus images. Renderings of the 3D volumetric datasets are also shown. Note the cloudy gray appearance of reflective signal from the vitreous, where liquefied areas of the vitreous appear transparent and hyperreflective foci appear white. Observed features are marked in the cross-sectional images: <i>bursa premacularis</i> (BPM) (white asterisk), Cloquet's canal (Area of Martegiani) (white circle), Cloquet's/BPM septum (white circle arrow), posterior cortical vitreous (hyaloid) detachment (black arrowhead), papillomacular hyaloid detachment (double black arrowheads), Bergmeister papilla (black diamond arrow), hyaloid attachment to retinal vessel (white arrowhead), granular opacities within vitreous cortex (black dashed arrow), granular opacities within BPM (black dotted arrow), granular opacities within Cloquet's (black arrow). Scale bars: 300 µm.</p

Detection of vitreal and vitreoretinal features in healthy eyes.

<p>OCT  =  Optical Coherence Tomography; HDR  =  High-dynamic-range.</p

Three-dimensional (3D) enhanced vitreous imaging enables visualization of the posterior vitreous and vitreoretinal interface in arbitrary cross sections or any <i>en face</i> plane.

<p>Arbitrary cross-sectional images and arbitrary <i>en face</i> images are generated from the 3D motion-corrected volumetric dataset with high-speed SS-OCT enhanced vitreous imaging display. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102950#pone.0102950.s001" target="_blank">Videos S1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102950#pone.0102950.s002" target="_blank">S2</a> are cross-sectional and <i>en face</i> flythrough videos of the 3D volumetric dataset. Scale bars: 300 µm.</p

Enhanced vitreous imaging of vitreomacular traction (VMT).

<p>(Top left) Vitreous detachment map where the measured area of attachment is 4.4 mm² over the macula and 23.2 mm² over the optic nerve head and retinal vessels. (Second row left) Three-dimensional (3D) rendering of the long-wavelength, high-speed SS-OCT volumetric dataset. (i, ii, iii, iv) Selected cross-sectional images through the fovea and <i>en face</i> images are shown. Note the improved visualization of the contour and shape of the posterior hyaloid with enhanced vitreous imaging. The presence of vitreous fibers and hyperreflective reflective foci in the posterior vitreous are clearly visible in the <i>en face</i> images and three-dimensional rendering. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102950#pone.0102950.s004" target="_blank">Video S4</a> is a video animation of the rendering. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102950#pone.0102950.s005" target="_blank">Video S5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102950#pone.0102950.s006" target="_blank">S6</a> are cross-sectional and <i>en face</i> flythrough videos of the 3D volumetric dataset. Scale bars: 300 µm.</p