IET Optoelectronics
Volume 11, Issue 5, October 2017
Volumes & issues:
Volume 11, Issue 5
October 2017
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- Author(s): A.C. Boucouvalas and K. Peppas
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 169 –170
- DOI: 10.1049/iet-opt.2017.0104
- Type: Article
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p.
169
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- Author(s): Zahra Vali ; Asghar Gholami ; David G. Michelson ; Zabih Ghassemlooy ; Masood Omoomi ; Hamed Noori
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 171 –175
- DOI: 10.1049/iet-opt.2016.0132
- Type: Article
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p.
171
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The vast majority of underwater wireless optical communication systems use collimated blue/green laser beams to deliver high-speed data over a transmission range of a few metres to tens of metres. However, such systems are extremely susceptible to misalignment of the transmitter and the receiver. The mitigation techniques for misalignment reported in the literature are complex and costly at times. In this study, the authors consider the simple approach of increasing the divergence angle of the transmitted Gaussian beam to mitigate misalignment. Both plane and spherical beams are considered as the limitation cases. Using Monte Carlo simulations, the authors show that an optimum divergence angle for the maximum acceptable lateral offset exists with respect to the receiver sensitivity in clear waters while this is not an efficient method in harbour waters. Results demonstrate that there is a design trade-off between acceptable lateral offset, power loss and channel bandwidth. Furthermore, the authors show how the proposed scheme of beam divergence affects the maximum allowed link span as well as the channel bandwidth for a given distance.
- Author(s): Victor Guerra ; Jose Rabadan ; Rafael Perez-Jimenez ; Julio Rufo
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 176 –179
- DOI: 10.1049/iet-opt.2016.0131
- Type: Article
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p.
176
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Underwater wireless optical communications (UWOCs) are subject to several phenomena related to light-matter interaction. Scattering due to particles and turbulences are factors that have been well studied in the last few years. However, for shallow-water links based on non-coherent sources as light emitting diodes, the impact of particles with higher dimensions that do not produce neither scattering nor diffraction has not been studied yet. In this work, a geometrical model to provide an estimation tool for shallow-water scenarios is presented. In this type of links, the emitter must be analysed as an extended source, since the effect of light-blocking particles cannot be correctly modelled using the traditional point-source approximation. The obtained results suggest that the effect of this kind of particles is large enough so as to take them into account when modelling UWOC links. The effect of these particles on the quality of the received optical signal depends on their size, concentration and other parameters such as the link's range and the endpoints’ surfaces. Some interesting conclusions are extracted such as the existence of an optimal emission area.
- Author(s): Kostas P. Peppas ; Anthony C. Boucouvalas ; Zabih Ghassemloy
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 180 –185
- DOI: 10.1049/iet-opt.2016.0130
- Type: Article
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180
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In this study, the performance of underwater optical wireless communication systems employing spatial diversity and multi-pulse position modulation techniques is assessed. The effects of inter-symbol interference, oceanic turbulence and receiver noise are taken into account. Oceanic turbulence is modelled by the log-normal distribution which is regarded as an appropriate model for weak turbulence conditions. For the system under consideration, approximate analytical expressions for the average bit error probability are deduced. The impact of the number of transmitting and receiving apertures, the achievable data rate and the water type on system performance is also investigated. Various numerical results are presented that demonstrate the proposed analysis.
Guest Editorial
Use of Gaussian beam divergence to compensate for misalignment of underwater wireless optical communication links
Effect of absorbing and non-diffracting particles in UWOC links
Performance of underwater optical wireless communication with multi-pulse pulse-position modulation receivers and spatial diversity
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- Author(s): David Dahan and Uri Mahlab
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 186 –200
- DOI: 10.1049/iet-opt.2016.0150
- Type: Article
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p.
186
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This study addresses the issues of optical network survivability to attacks in the optical physical layer. The authors comprehensively review and discuss the vulnerability of optical networks towards various types of security threats that could appear in the network optical layer: passive eavesdropping attacks and active optical attacks like in-band jamming, out-of-band crosstalk attacks, amplifier attacks and physical infrastructure attacks. They describe and discuss several protection procedures and monitoring techniques to improve network attack survivability. Numerical simulation performances of some attacks and protection schemes are also provided.
Security threats and protection procedures for optical networks
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- Author(s): Subhendu Saha ; Subhendu Biswas ; Sourangshu Mukhopadhyay
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 201 –207
- DOI: 10.1049/iet-opt.2016.0078
- Type: Article
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201
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The conversion of decimal number to its equivalent binary one and vice-versa is very important in the field of electronic/optical computing and data processing system. There are so many well established methods for this conversion. In this study, the authors propose a new scheme for optical conversion of a decimal number to its frequency encoded binary equivalent using tree architecture-based system and frequency-encoding principle. To implement the above conversion, some optical non-linear switches, such as Mach–Zehnder interferometer-based semiconductor optical amplifier (SOA), reflecting SOA based on SOA, have been used to get frequency encoded response.
- Author(s): Sajal Agarwal and Yogendra Kumar Prajapati
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 208 –212
- DOI: 10.1049/iet-opt.2016.0169
- Type: Article
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p.
208
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This study proposed a broadband polarisation independent quad helix metamaterial-based absorber for thermo-photovoltaic cell (TPVC) application. Absorber is a very important part of TPVC. The design and simulation of absorber is done for wide operating wavelength range of TPVC absorber. It is observed that the average absorbance is 92.38% for the wavelength range of 340–1680 nm in the proposed absorber. Furthermore, existing absorbers which are used in thermo-photovoltaic and solar cell are compared with proposed absorber and the proposed absorber is better in terms of operating wavelength range.
- Author(s): Michael Joseph Wishon ; Alexandre Locquet ; Guillaume Mourozeau ; Daeyoung Choi ; Sreejith K.R. ; Aakash Sahai ; David Citrin
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 213 –216
- DOI: 10.1049/iet-opt.2016.0118
- Type: Article
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213
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The authors demonstrate that the bits of a Compact Disc – Read Only Memory (CD-ROM) can be read without a photodiode (PD). A commercial CD-ROM drive was used and left unmodified except a beam splitter was removed which would route the light to a PD. This allowed for the reflected light to be incident on the laser within the laser package itself. By monitoring fluctuations in the voltage across the laser diode under constant-current injection, it was possible to read and interpret the bits from a spinning CD-ROM.
- Author(s): Nikhil Deep Gupta and Vijay Janyani
- Source: IET Optoelectronics, Volume 11, Issue 5, p. 217 –224
- DOI: 10.1049/iet-opt.2017.0002
- Type: Article
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The study proposes designs using 2D photonic crystal (PhC) structure-based thin film heterojunction gallium arsenide (GaAs) solar cell with a periodic pattern having PhC structure extends from top transparent conducting oxide (TCO) to inside the p-AlGaAs window layer placed just above the active layer of GaAs material in one design and in another PhC structure is etched only in TCO. The work presents the comparative analysis of the proposed structure with Lambertian light trapping limits and the planar cell, taken as reference. The study is also performed for double-layer anti-reflective coating (ARC) structure. The study presents the quantitative analysis of the effect of PhC structure in the performance of the design and how the effect varies with the thickness of absorption layer. It has been found that a considerable increase in efficiency has been achieved, especially for thinner active layers, demonstrating the advantage of a wavelength-scale, PhC-based structures for thin-film solar cells. The results have shown that PhC structure (etched till inside p-AlGaAs)-based solar cell exceeds the efficiency of the double ARC-based structure by more than 18% for 50 nm thin active layer cell. The parameters have been optimised and calculated by means of rigorous coupled wave analysis (RCWA).
Optical scheme of conversion of a positionally encoded decimal digit to frequency encoded Boolean form using Mach–Zehnder interferometer-based semiconductor optical amplifier
Analysis of metamaterial-based absorber for thermo-photovoltaic cell applications
Reading bits on a CD-ROM without a photodiode
Lambertian and photonic light trapping analysis with thickness for GaAs solar cells based on 2D periodic pattern
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