Kang, Chun Hong; Trichili, Abderrahmen; Alkhazragi, Omar; Zhang, Huafan; Subedi, Ram Chandra; Guo, Yujian; Mitra, Somak; Shen, Chao; Roqan, Iman S.; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.(Optics Express, The Optical Society, 2019-10-08)[Article]
Underwater wireless optical communication (UWOC) can offer reliable and secure connectivity for enabling future internet-of-underwater-things (IoUT), owing to its unlicensed spectrum and high transmission speed. However, a critical bottleneck lies in the strict requirement of pointing, acquisition, and tracking (PAT), for effective recovery of modulated optical signals at the receiver end. A large-area, high bandwidth, and wide-angle-of-view photoreceiver is therefore crucial for establishing a high-speed yet reliable communication link under non-directional pointing in a turbulent underwater environment. In this work, we demonstrated a large-area, of up to a few tens of cm2, photoreceiver design based on ultraviolet(UV)-to-blue color-converting plastic scintillating fibers, and yet offering high 3-dB bandwidth of up to 86.13 MHz. Tapping on the large modulation bandwidth, we demonstrated a high data rate of 250 Mbps at bit-error ratio (BER) of 2.2 × 10−3 using non-return-to-zero on-off keying (NRZ-OOK) pseudorandom binary sequence (PRBS) 210-1 data stream, a 375-nm laser-based communication link over the 1.15-m water channel. This proof-of-concept demonstration opens the pathway for revolutionizing the photodetection scheme in UWOC, and for non-line-of-sight (NLOS) free-space optical communication.
Free-space optical (FSO) communication, considered as a last-mile technology, is widely used in many urban scenarios. However, the performance of urban free-space optical (UFSO) communication systems fades in the presence of system vibration caused by many factors in the chaotic urban environment. In this paper, we develop a dedicated indoor vibration platform and atmospheric turbulence to estimate the Bifurcated-Gaussian (B-G) distribution model of the receiver optical power under different vibration levels and link distances using nonlinear iteration method. Mean square error (MSE) and coefficient of determination ($R^2$) metrics have been used to show a good agreement between the PDFs of the experimental data with the resulting B-G distribution model. Besides, the UFSO channel under the effects of both vibration and atmospheric turbulence is also explored under three atmospheric turbulence conditions. Our proposed B-G distribution model describes the vibrating UFSO channels properly and can easily help to perform and evaluate the link performance of UFSO systems, e.g., bit-error-rate (BER), outage probability. Furthermore, this work paves the way for constructing completed auxiliary control subsystems for robust UFSO links and contributes to more extensive optical communication scenarios, such as underwater optical communication, etc.
Shamim, Md. Hosne Mobarok; Alkhazragi, Omar; Ng, Tien Khee; Ooi, Boon S.; Khan, Mohammed Zahed Mustafa(IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2019-10-01)[Article]
We implemented a tunable dual-longitudinal-mode spacing InGaN/GaN green (521–528 nm) laser diode by employing a self-injection locking scheme that is based on an external cavity configuration and utilizing either a high-or partial-reflecting mirror. A tunable longitudinal-mode spacing of 0.20 – 5.96 nm was accomplished, corresponding to a calculated frequency difference of 0.22–6.51 THz, as a result. The influence of operating current and temperature on the system performance was also investigated with a measured maximum side-mode-suppression ratio of 30.4 dB and minimum dual-mode peak optical power ratio of 0.03 dB. To shed light on the operation of the dual-wavelength device arising from the tunable longitudinal-mode spacing mechanism, the underlying physics is qualitatively described. To the best of our knowledge, this tunable longitudinal-mode-spacing dual-wavelength device is novel, and has potential applications as an alternative means in millimeter wave and THz generation, thus possibly addressing the terahertz technology gap. The dual-wavelength operation is also attractive for high-resolution imaging and broadband wireless communication.
Al-Jarrah, Mohammad; Park, Kihong; Al-Dweik, Arafat; Alouini, Mohamed-Slim(IEEE Transactions on Wireless Communications, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-27)[Article]
Amplitude-coherent (AC) detection is an efficient technique that can simplify the receiver design while providing reliable symbol error rate (SER). Therefore, this work considers AC detector design and SER analysis using M-ary amplitude shift keying (MASK) modulation with receiver diversity over Rician fading channels. More specifically, we derive the optimum, near-optimum and a suboptimum AC detectors and compare their SER with the coherent, phase-coherent, noncoherent and the heuristic AC detectors. Moreover, the analytical and asymptotic SER at high signal-to-noise ratios (SNRs) are derived for the heuristic detector using single and multiple receiving antennas. The obtained analytical and simulation results show that the SER of the AC and coherent MASK detectors are comparable, particularly for high values of the Rician K-factor, and small number of receiving antennas. In most of the considered scenarios, the heuristic AC detector outperforms the optimum noncoherent detector significantly, except for the binary ASK case at low SNRs. Moreover, the obtained results show that the heuristic AC detector is immune to phase noise, and thus, it outperforms the coherent detector in scenarios where the system is subject to considerable phase noise.
Wang, Congli; Fu, Qiang; Dun, Xiong; Heidrich, Wolfgang(Scientific Reports, Springer Science and Business Media LLC, 2019-09-24)[Article]
Phase imaging techniques are an invaluable tool in microscopy for quickly examining thin transparent specimens. Existing methods are limited to either simple and inexpensive methods that produce only qualitative phase information (e.g. phase contrast microscopy, DIC), or significantly more elaborate and expensive quantitative methods. Here we demonstrate a low-cost, easy to implement microscopy setup for quantitative imaging of phase and bright field amplitude using collimated white light illumination.
Shan, Maocheng; Zhang, Yi; Tran, Tinh Binh; Jiang, Jie’an; Long, Hanling; Zheng, Zhihua; Wang, An’ge; Guo, Wei; Ye, Jichun; Chen, Changqing; Dai, Jiangnan; Li, Xiaohang(ACS Photonics, American Chemical Society (ACS), 2019-09-20)[Article]
In this Letter, we report on deep UV laser emitting at 249 nm based on thin GaN quantum wells (QWs) by optical pumping at room temperature. The laser threshold was 190 kW/cm2 that is comparable to state-of-the-art AlGaN QW lasers at similar wavelengths. The laser structure was pseudomorphically grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition, comprising 40 pairs of 4 monolayer (ML) GaN QWs sandwiched by 6 ML AlN quantum barriers (QBs). The low threshold at the wavelength was attributed to large optical and quantum confinement and high quality of the material, interface, and Fabry-Pérot facet. The emissions below and above the threshold were both dominated by transverse electric polarizations thanks to the valence band characteristics of GaN. This work unambiguously demonstrates the potentials of the binary AlN/GaN heterojunctions for high-performance UV emitters.
Nam, Sung Sik; Ko, Young-Chai; Hwang, Duckdong; Alouini, Mohamed-Slim(IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-19)[Article]
In this paper, we introduce a systematic and unified stochastic tool to determine the joint statistics of partial products of ordered random variables (RVs). With the proposed approach, we can systematically obtain the desired joint statistics of any partial products of ordered statistics in terms of the Mellin transform and the probability density function in a unified way. Our approach can be applied when all the K-ordered RVs are involved, even for more complicated cases, for example, when only the Ks (Ks<K) best RVs are also considered. As an example of their application, these results can be applied to the performance analysis of various wireless communication systems including wireless optical communication systems. For an applied example, we present the closed-form expressions for the exponential RV special case. We would like to emphasize that with the derived results based on our proposed stochastic tool, computational complexity and execution time can be reduced compared to the computational complexity and execution time based on an original multiple-fold integral expression of the conventional Mellin transform based approach which has been applied in cases of the product of RVs.
Mao, Yuan; Ashry, Islam; Alias, Mohd Sharizal; Ng, Tien Khee; Hveding, Frode; Arsalan, Muhammad; Ooi, Boon S.(IEEE Photonics Journal, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-17)[Article]
We experimentally investigated the performance of a distributed acoustic sensor (DAS) designed using a few-mode fiber (FMF), when launching different spatial modes under intentional index perturbation within the fiber. Our demonstration showed that the quasi-single mode (QSM) operated FMF offers higher signal-to-noise ratio (SNR) for the DAS, compared with the case when launching other degenerate higher order modes. Additionally, we compared the behavior of the single-mode fiber (SMF)- and FMF-based DAS when using optical pulses of varying power levels. The FMF enables the realization of a DAS with longer sensing range and higher spatial resolution. The developed FMF-based DAS is further tested via sensing various vibration events produced by piezoelectric transducer (PZT) cylinder, pencil break, and loudspeaker.
Elserougi, Ahmed; Abdelsalam, Ibrahim; Massoud, Ahmed; Ahmed, Shehab(IEEE Access, Institute of Electrical and Electronics Engineers (IEEE), 2019-09-13)[Article]
This paper presents small-signal modeling, stability analysis, and controller design of a nonisolated bidirectional hybrid-modular DC-DC Converter for DC grid applications. The DC-DC converter can be used to interconnect two different DC voltage levels in a medium-/high-voltage DC grid. Half-bridge Sub-Modules (SMs) and a high-voltage valve are the main components of the converter. The high-voltage valve can be implemented via employing series-connected Insulated-Gate Bipolar Transistors (IGBTs). Operation with zero voltage switching of the involved high-voltage valve is feasible, i.e., there is no concern pertinent to dynamic voltage sharing among the series-connected IGBTs. The power is transferred from one side to another through the involved SMs, where their capacitors are connected in series across the high-voltage side, while they are connected sequentially across the low-voltage side. In this paper, the state-space averaging technique is employed to derive the small-signal model of the presented converter for controller design. Closed-form expression of the duty cycle-to-inductor current transfer function is extracted. Comparison between simulation results of the small-signal model and the detailed circuit model is presented to authenticate the accuracy of the derived small-signal model. Finally, a scaled-down prototype is used to verify the accuracy of the small-signal model.
Damdam, A. N.; Qaisar, N.; Hussain, Muhammad Mustafa(Applied Physics Letters, AIP Publishing, 2019-09-09)[Article]
The shape reconfiguration is an arising concept in advanced electronics research, which allows the electronic platform to change in shape and assume different configurations while maintaining high electrical functionality. The reconfigurable electronic platforms are attractive for state of the art biomedical technologies, where the reshaping feature increases the adaptability and compliance of the electronic platform to the human body. Here, we present an amorphous silicon honeycomb-shaped reconfigurable electronic platform that can reconfigure into three different shapes: the quatrefoil shape, the star shape, and an irregular shape. We show the reconfiguration capabilities of the design in microscale and macroscale fabricated versions. We use finite element method analysis to calculate the stress and strain profiles of the microsized honeycomb-serpentine design at a prescribed displacement of 100 μ m. The results show that the reconfiguration capabilities can be improved by eliminating certain interconnects. We further improve the design by optimizing the serpentine interconnect parameters and refabricate the platform on a macroscale to facilitate the reconfiguration process. The macroscale version demonstrates an enhanced reconfiguration capability and elevates the stretchability by 21% along the vertical axis and by 36.6% along the diagonal axis of the platform. The resulting reconfiguring capabilities of the serpentine-honeycomb reconfigurable platform broaden the innovation opportunity for wearable electronics, implantable electronics, and soft robotics.
The export option will allow you to export the current search results of the entered query to a file. Different
formats are available for download. To export the items, click on the button corresponding with the preferred download format.
By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.
For anonymous users the allowed maximum amount is 50 search results.
To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export.
The amount of items that can be exported at once is similarly restricted as the full export.
After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.