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Photonics, Volume 1, Issue 3 (September 2014), Pages 162-282

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Research

Jump to: Review

Open AccessArticle FTTA System Demo Using Optical Fiber-Coupled Active Antennas
Photonics 2014, 1(3), 198-210; doi:10.3390/photonics1030198
Received: 1 July 2014 / Revised: 24 July 2014 / Accepted: 29 July 2014 / Published: 5 August 2014
Cited by 1 | PDF Full-text (6439 KB) | HTML Full-text | XML Full-text
Abstract
The convergence of optical and wireless systems such as Radio-over-Fiber (RoF) networks is the key to coping with the increasing bandwidth demands due to the increasing popularity of video and other high data rate applications. A high level of integration of optical [...] Read more.
The convergence of optical and wireless systems such as Radio-over-Fiber (RoF) networks is the key to coping with the increasing bandwidth demands due to the increasing popularity of video and other high data rate applications. A high level of integration of optical technologies enables simple base stations with a fiber-to-the-antenna (FTTA) approach. In this paper, we present a complete full-duplex RoF–FTTA system consisting of integrated active fiber-coupled optical receiving and transmitting antennas that are directly connected to a standard single mode fiber optical link. Data rates up to 1 Gbit/s could be shown without advanced modulation formats on a 1.5 GHz carrier frequency. The antennas as well as the whole system are explained and the results of the system experiments are discussed. Full article
(This article belongs to the Special Issue Microwave Photonics)
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Open AccessArticle Photostress Testing Device for Diagnosing Retinal Disease
Photonics 2014, 1(3), 211-219; doi:10.3390/photonics1030211
Received: 14 July 2014 / Revised: 1 August 2014 / Accepted: 1 August 2014 / Published: 8 August 2014
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Abstract
Retinal diseases such as Age-Related Macular Degeneration (ARMD) affect nearly one in three elderly patients. ARMD damages the central vision photoreceptors in the fovea. The Photostress Test is a simple technique for testing for the early effects of ARMD. Here, the illumination [...] Read more.
Retinal diseases such as Age-Related Macular Degeneration (ARMD) affect nearly one in three elderly patients. ARMD damages the central vision photoreceptors in the fovea. The Photostress Test is a simple technique for testing for the early effects of ARMD. Here, the illumination sources in a novel self-administered Photostress Testing device were modeled for safety and distribution in illumination software. After satisfying the design constraints in the model, a prototype of the illumination system was fabricated and tested to confirm the modeling results. The resultant prototype can be used to aid in the diagnosis of retinal disease and is well within retinal safety levels. Full article
(This article belongs to the Special Issue Optics and Technologies for Ophthalmology and Visual Science)
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Open AccessArticle Energy-Saving Mechanism in WDM/TDM-PON Based on Upstream Network Traffic
Photonics 2014, 1(3), 235-250; doi:10.3390/photonics1030235
Received: 21 July 2014 / Accepted: 5 August 2014 / Published: 12 August 2014
Cited by 2 | PDF Full-text (1174 KB) | HTML Full-text | XML Full-text
Abstract
One of the main challenges of Passive Optical Networks (PONs) is the resource (bandwidth and wavelength) management. Since it has been shown that access networks consume a significant part of the overall energy of the telecom networks, the resource management schemes should [...] Read more.
One of the main challenges of Passive Optical Networks (PONs) is the resource (bandwidth and wavelength) management. Since it has been shown that access networks consume a significant part of the overall energy of the telecom networks, the resource management schemes should also consider energy minimization strategies. To sustain the increased bandwidth demand of emerging applications in the access section of the network, it is expected that next generation optical access networks will adopt the wavelength division/time division multiplexing (WDM/TDM) technique to increase PONs capacity. Compared with traditional PONs, the architecture of a WDM/TDM-PON requires more transceivers/receivers, hence they are expected to consume more energy. In this paper, we focus on the energy minimization in WDM/TDM-PONs and we propose an energy-efficient Dynamic Bandwidth and Wavelength Allocation mechanism whose objective is to turn off, whenever possible, the unnecessary upstream traffic receivers at the Optical Line Terminal (OLT). We evaluate our mechanism in different scenarios and show that the proper use of upstream channels leads to relevant energy savings. Our proposed energy-saving mechanism is able to save energy at the OLT while maintaining the introduced penalties in terms of packet delay and cycle time within an acceptable range. We might highlight the benefits of our proposal as a mechanism that maximizes the channel utilization. Detailed implementation of the proposed algorithm is presented, and simulation results are reported to quantify energy savings and effects on network performance on different network scenarios. Full article
(This article belongs to the Special Issue All Optical Networks for Communications)
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Open AccessArticle Coal Char Derived Few-Layer Graphene Anodes for Lithium Ion Batteries
Photonics 2014, 1(3), 251-259; doi:10.3390/photonics1030251
Received: 18 July 2014 / Revised: 18 August 2014 / Accepted: 18 August 2014 / Published: 25 August 2014
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Abstract
Few-layer graphene films were synthesized through chemical vapor deposition technique using coal char as solid carbon source. Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and selected area electron diffraction were used to characterize the graphene films. The electrochemical performance of the coal [...] Read more.
Few-layer graphene films were synthesized through chemical vapor deposition technique using coal char as solid carbon source. Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and selected area electron diffraction were used to characterize the graphene films. The electrochemical performance of the coal char derived few layer graphene anodes for lithium ion batteries was investigated by charge/discharge curves  and  discharge  capacity  at  different  current  densities.  The  graphene  anode maintained the reversible capacity at ~0.025, 0.013, and 0.007 mAh/cm2  at a current density of 10, 30, and 50 µA/cm2, respectively. The coal char derived graphene anodes show potential applications in thin film batteries for nanoelectronics. Full article
Open AccessArticle Preliminary Design and Evaluation of a B-Scan OCT-Guided Needle
Photonics 2014, 1(3), 260-266; doi:10.3390/photonics1030260
Received: 4 August 2014 / Revised: 7 September 2014 / Accepted: 8 September 2014 / Published: 12 September 2014
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Abstract
Real-time intraoperative B-scan optical coherence tomography (OCT) visualization of intraocular tissues is a desired ophthalmic feature during retinal procedures. A novel intraocular 25-gauge B-mode forward-imaging OCT probe was combined with a 36-gauge needle into a prototype instrument. Imaging of the needle tip [...] Read more.
Real-time intraoperative B-scan optical coherence tomography (OCT) visualization of intraocular tissues is a desired ophthalmic feature during retinal procedures. A novel intraocular 25-gauge B-mode forward-imaging OCT probe was combined with a 36-gauge needle into a prototype instrument. Imaging of the needle tip itself and the effects of saline injection into a gelatin phantom were performed. A combined B-scan forward-imaging OCT-needle prototype was capable of real-time-imaging of saline injection into a gelatin phantom. Additional future miniaturization may permit this instrument to be an adjunctive real-time imaging and procedure tool for vitreoretinal surgery. Full article
(This article belongs to the Special Issue Optics and Technologies for Ophthalmology and Visual Science)
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Open AccessArticle A Rapid and Convenient Procedure to Evaluate Optical Performance of Intraocular Lenses
Photonics 2014, 1(3), 267-282; doi:10.3390/photonics1030267
Received: 24 August 2014 / Revised: 14 September 2014 / Accepted: 14 September 2014 / Published: 18 September 2014
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Abstract
A new portable lens scanner was developed and tested for measuring focal lengths and relative contrast transfer of mono- and multifocal intraocular lenses (IOLs). A photograph of a natural scene was imaged in white light through an IOL in a water-filled cuvette, [...] Read more.
A new portable lens scanner was developed and tested for measuring focal lengths and relative contrast transfer of mono- and multifocal intraocular lenses (IOLs). A photograph of a natural scene was imaged in white light through an IOL in a water-filled cuvette, with their +21D base power largely neutralized by a −20D trial lens, using a USB monochrome video camera that could be focused via a laptop-controlled stepping motor from −8.5 to + 8.0D. The output of 10000 ON-OFF antagonistic “receptive fields” measuring the video image with adjustable diameter was continuously recorded by custom written software to quantify focus and relative contrast. Six monofocal and four multifocal IOLs, as well as two radial refractive gradient (RRG) lenses were measured. After calibration with trial lenses the optical powers and relative contrast transfer of mono- and multifocal IOLs were readily measured. Refractive power profiles measured in RRG lenses closely matched data obtained from the manufacturer. The lens scanner uses a rapidly operating procedure, is portable and can be used to verify positions of the focal planes of mono- and multifocal IOLs in less than 3 s. Full article
(This article belongs to the Special Issue Optics and Technologies for Ophthalmology and Visual Science)

Review

Jump to: Research

Open AccessReview Monolithically Integrated Ge-on-Si Active Photonics
Photonics 2014, 1(3), 162-197; doi:10.3390/photonics1030162
Received: 27 May 2014 / Revised: 19 June 2014 / Accepted: 19 June 2014 / Published: 2 July 2014
Cited by 14 | PDF Full-text (3694 KB) | HTML Full-text | XML Full-text
Abstract
Monolithically integrated, active photonic devices on Si are key components in Si-based large-scale electronic-photonic integration for future generations of high-performance, low-power computation and communication systems. Ge has become an interesting candidate for active photonic devices in Si photonics due to its pseudo-direct [...] Read more.
Monolithically integrated, active photonic devices on Si are key components in Si-based large-scale electronic-photonic integration for future generations of high-performance, low-power computation and communication systems. Ge has become an interesting candidate for active photonic devices in Si photonics due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS) processing. In this paper, we present a review of the recent progress in Ge-on-Si active photonics materials and devices for photon detection, modulation, and generation. We first discuss the band engineering of Ge using tensile strain, n-type doping, Sn alloying, and separate confinement of Γ vs. L electrons in quantum well (QW) structures to transform the material towards a direct band gap semiconductor for enhancing optoelectronic properties. We then give a brief overview of epitaxial Ge-on-Si materials growth, followed by a summary of recent investigations towards low-temperature, direct growth of high crystallinity Ge and GeSn alloys on dielectric layers for 3D photonic integration. Finally, we review the most recent studies on waveguide-integrated Ge-on-Si photodetectors (PDs), electroabsorption modulators (EAMs), and laser diodes (LDs), and suggest possible future research directions for large-scale monolithic electronic-photonic integrated circuits on a Si platform. Full article
Open AccessReview Basic Technology and Clinical Applications of the Updated Model of Laser Speckle Flowgraphy to Ocular Diseases
Photonics 2014, 1(3), 220-234; doi:10.3390/photonics1030220
Received: 20 July 2014 / Revised: 7 August 2014 / Accepted: 7 August 2014 / Published: 12 August 2014
Cited by 9 | PDF Full-text (918 KB) | HTML Full-text | XML Full-text
Abstract
Laser speckle flowgraphy (LSFG) allows for quantitative estimation of blood flow in the optic nerve head (ONH), choroid and retina, utilizing the laser speckle phenomenon. The basic technology and clinical applications of LSFG-NAVI, the updated model of LSFG, are summarized in this [...] Read more.
Laser speckle flowgraphy (LSFG) allows for quantitative estimation of blood flow in the optic nerve head (ONH), choroid and retina, utilizing the laser speckle phenomenon. The basic technology and clinical applications of LSFG-NAVI, the updated model of LSFG, are summarized in this review. For developing a commercial version of LSFG, the special area sensor was replaced by the ordinary charge-coupled device camera. In LSFG-NAVI, the mean blur rate (MBR) has been introduced as a new parameter. Compared to the original LSFG model, LSFG-NAVI demonstrates a better spatial resolution of the blood flow map of human ocular fundus. The observation area is 24 times larger than the original system. The analysis software can separately calculate MBRs in the blood vessels and tissues (capillaries) of an entire ONH and the measurements have good reproducibility. The absolute values of MBR in the ONH have been shown to linearly correlate with the capillary blood flow. The Analysis of MBR pulse waveform provides parameters including skew, blowout score, blowout time, rising and falling rates, flow acceleration index, acceleration time index, and resistivity index for comparing different eyes. Recently, there have been an increasing number of reports on the clinical applications of LSFG-NAVI to ocular diseases, including glaucoma, retinal and choroidal diseases. Full article
(This article belongs to the Special Issue Optics and Technologies for Ophthalmology and Visual Science)
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