Loss Bandwidth Research Articles

Germanium photodetector with distributed absorption regions.

The bandwidth and saturation power of germanium photodetectors are two crucial parameters for implementing analog and microwave photonics circuits. In conventional schemes, it is hard to optimize these two parameters simultaneously, due to different requirements for the size of absorption region. We report the design and demonstration of a high-power and high-speed germanium photodetector with distributed absorption regions. In this distributed-absorption photodetector (DAPD), the junction is formed by a multiple absorption region (n-cell) on a mutual substrate, and the input light is split and fed into the n cells. A comprehensive theoretical model is developed, and the device bandwidth and power loss in aspect of the number of cells is discussed. Experimentally, 2-, 4- and 8-cell DAPDs are investigated, and the 2-cell scheme shows the superior performance with the radio-frequency saturation photocurrent as high as 16.1 mA and the 3 dB bandwidth as high as 50 GHz. Without changing the standard process in the silicon photonic foundry, the DAPD can be seamlessly integrated with other photonics devices, and it is very attractive to applications such as integrated microwave photonics systems.

Random weather phenomena in free-space optical - FTTx communication system

In the last few decades, optical wireless communication became an essential technology in various applications. Researchers have paid more attention to achieving high bandwidth and low loss. However, the random weather phenomena cause attenuation of optical signals, thus will decrease the bandwidth in optical wireless communication. In this article, we investigate a hybrid free-space optical (FSO) and fiber-to-the-x (FTTx) communications link based on wavelength-division multiple access (WDMA) over different random weather phenomena that operate over different wavelengths. The performance of the hybrid FSO-FTTx system is evaluated under clear sky weather phenomena, heavy rain weather phenomena, and heavy haze weather phenomena based on BER and Q-Factor measurements. The results show that we can transmit 140 Gbit/s data over 9650 meters a hybrid link under the clear sky and heavy rain weather phenomena, 3950 meters over. Additionally, the transmission of 140 Gbit/s data can be achieved for 1450 meters under the heavy haze weather phenomenon.

Investigation of the microwave attenuation performance and structure‐property relationship for graphite‐filled cyclo‐olefin copolymer composites

AbstractThis study examined the morphological, rheological, viscoelastic, electrical, and microwave attenuation properties (RADAR absorbent and EMI shielding) of cyclo‐olefin copolymer (COC) composites prepared with the melt mixing method by using different amounts of graphite (0‐75 phr). Rheological percolation threshold of the graphite was determined as ∼38 phr. The RL analyses of the composites showed that the composites containing a moderate filler content (45 phr) exhibited the best radar absorption performance. Absorption bandwidth and minimum reflection loss (RL) value for the sample containing 45 phr of graphite were determined as 2.335 GHz (10.165‐12.5 GHz) and −39.89 dB, respectively. Total shielding effectiveness (SET) values of the sample including 75 phr of graphite varied in the ranges of 30 to 47.5 dB for the sample thicknesses of 7 mm. The correlation of the microstructural parameters and microwave attenuation properties of the composites indicated that the minimum RL value could be obtained at a filler concentration close to the rheological and electrical percolation thresholds. However, it was also revealed that acceptable shielding effectiveness values for commercial applications could be obtained by the samples with higher filler concentrations than the electrical percolation threshold.

In brief

PAGE 632 Chinese researchers propose a symbol cyclic reconstruction scheme for universal-filtered multi-carrier systems (UFMC). The overlap-add technique is used to lower the computational complexity of the system transmitter, with ISI cancellation used at the receiver to remove interference between neighbouring symbols. Simulation results show the superiority of the scheme over state-of-the-art systems. PAGE 616 Researchers from Iran present a monitoring technique for tracking the state-of-health of batteries, suitable for use in battery management systems. The method can detect early degradation of batteries by monitoring the switching and battery transitions in a battery management system. Experiments on a typical charge balancing circuit verify the performance of the technique. Block diagram of SCR-UFMC with multipath fading channels. PAGE 589 Indian researchers propose a novel estimation technique for a noise-influenced electronic circuit, unifying the Carleman linearisation with the Fokker-Planck equation for Itô's Stochastic Differential Equations. Numerical simulation results are presented for a benchmark tunnel diode oscillator circuit. The method may prove useful for estimating state trajectories under the influence of randomness when observations are not possible. Laboratory test bench. PAGE 612 A collaboration of researchers from Japan present an evaluative study on the current and luminance characteristics of powder electroluminescent devices prepared on gravure offset-printed invisible Ag-grid electrodes. Results show that the luminance is strongly dependent on the transparency and light-extraction efficiency of the Ag-grid electrodes. Flow of the proposed estimation technique.. PAGE 609 Researchers from China propose a wideband differential filtering power divider, using a three-lined coupled structure with multiple lumped elements. Compared with other differential filtering power dividers, the proposed design shows the advantages of a wide bandwidth, compact size and low insertion loss. A prototype validates the simulated results. Optical microscopy image of the emitted light from PELDs on the Ag-grid electrodes. Photograph of the proposed wideband differential filtering power divider.

Compact wideband differential filtering power divider based on three‐line coupled structure with lumped elements

A wideband differential filtering power divider using three-line coupled structure with multiple lumped elements is proposed. The equal power division ratio, filtering response, isolation and common-mode suppression are mainly derived from the symmetrical structure, three-line coupled lines with capacitors, resistors and the short lines along the vertical symmetrical line, respectively. Compared to the reported differential filtering power dividers, the proposed design shows advantages of wide bandwidth, compact size and low insertion loss (IL). A prototype with the small size of 0.5λ g × 0.08λ g (λ g is the guided wavelength at the centre frequency) was designed for demonstration, which exhibits the 3 dB fractional bandwidth of 79.2% and the minimum IL of 0.48 dB.

Structured decomposition of a multi-snapshot nine-reconstructables Mueller matrix polarimeter.

Snapshot channeled polarimeters forgo temporal modulation in favor of modulating polarization information in either space or wavenumber. We have recently introduced methodologies for describing both channeled and partial polarimeters. In this paper, we focus on the nine-reconstructables design, which limits the resolution loss by reducing the number of carriers. The architecture offers a number of favorable trade-offs: a factor of 5.44 increase in spatial bandwidth or a factor of 3.67 increase in spectral bandwidth, for a smaller amount of temporal bandwidth loss as dictated by the number of snapshots taken. The multi-snapshot structured decomposition given here allows one to analytically shape the measured space with optimal noise characteristics and minimum system complexity. A two-snapshot system can measure a premeditated set of 14 reconstructables; we provide the null space for the subset of optimal systems that also achieve better SNR than the baseline single-snapshot system. A three-snapshot system can measure all 16 Mueller elements while offering an overall 26.3% or 50.4% better bandwidth-SNR figure of merit for the spectral and spatial systems, respectively. Finally, four-snapshot systems provide diminishing returns, but may be more implementable.

Broadband Plasmonic Polarization Filter Based on Photonic Crystal Fiber with Dual-Ring Gold Layer.

Polarization filter is a very important optical device with extinction characteristics. Due to the design flexibility of photonic crystal fibers and the high excitation losses of the gold layer, the polarization filter based on the photonic crystal fiber and surface plasmonic resonance effect is widely studied. Considering these, we present a simple and high-performance polarization filter using the finite element method. Numerical simulations show that there is a large difference in energy between the two polarization directions by reasonable adjustment of the structural parameters, the confinement loss in the x-pol direction is less than that in the y-pol direction, which is suitable to realize a broadband polarization filter. When the fiber length is 2 mm, the extinction ratio peak can reach −478 dB, and the bandwidth with the extinction ratio better than −20 dB is 750 nm, which covers communication wavelengths of 1.31 μm and 1.55 μm (1.05–1.8 μm). It also has a low insertion loss of 0.11 dB at 1.31 μm and 0.04 dB at 1.55 μm. In addition, our design has high feasibility in fabrication and better tolerance. The proposed filter with compactness, high extinction ratio, broad bandwidth, and low insertion loss would play an important role in the sensing detection, bio-medical, and telecommunication field.

Event-triggered fault detection for T-S fuzzy systems subject to data losses

ABSTRACTThis work focuses on the fault detection for nonlinear networked systems. A fault detection filter is designed to detect the fault signal under the effect of disturbance. The communication channel of the networked system is supposed to be influenced by the limited bandwidth and random data losses. To deal with these, event-triggered scheme and Bernoulli process are employed to describe the problems, respectively. According to the above situation, we employ a formulated random series to describe the input of fuzzy filter. Differential mean value theorem based method is presented to handle the asynchronous membership functions. Synthetically, linear matrix inequality approach is employed to obtain the stability conditions and the filter design process. At last, we verify the performance of this method acting in the simulation example.

Attenuation of receiver ghosts in variable-depth streamer high-resolution seismic reflection data

Receiver ghosts attenuate marine seismic reflection data at harmonic frequencies that depend on the propagation angle and the streamer depth below the sea surface. The resulting loss of bandwidth is one of the major factors hampering seismic resolution. In near-surface and legacy multi-channel data, receivers depth is often unknown and may vary significantly both along the streamer length and during the survey, making frequency–slowness deghosting techniques unsuitable. In this work, we present a method for the attenuation of receiver ghost reflections in data with an arbitrary streamer depth profile varying during the survey. For each trace, a different deghosting operator is estimated and applied at different two-way-time windows, in order to account for depth-dependent changes in reflection angles. The ghost null frequencies are picked on the time-varying power spectrum via an automatic algorithm, guided by a user-dependent a priori function, and optimised to respect the harmonics’ periodicity. The power of the inverse filter is adjusted by adaptively damping abnormal amplitudes in the deghosted spectra. The algorithm is applied to high-resolution (GI-gun, 20–400 Hz) and ultra-high-resolution (Sparker, 0.2–3.0 kHz) multi-channel datasets, yielding an excellent bandwidth recovery and gain in resolution in the final stacks. Limited computing time and straightforward application make the method widely applicable and cost-effective.

Broadband low loss and ultra-low crosstalk waveguide crossings based on a multimode interferometer for 840 nm operation

Broadband low loss and ultra-low crosstalk waveguide crossings are a crucial component for photonic integrated circuits to allow a higher integration density of functional components and an increased flexibility in the layout. We report the design of optimized silicon nitride waveguide crossings based on multimode interferometer structures for intersecting light paths of TE/TE-like, TM/TM-like, and TE/TM-like polarized light in the near infrared wavelength region of 790 nm to 890 nm. The crossing design for diverse polarization modes facilitates dual polarization operation on a single chip. For all configurations the loss of a single crossing was measured to be ~0.05 dB at 840 nm. Within the 100 nm bandwidth losses stayed below 0.16 dB. The crosstalk was estimated to be on the order of −60 dB by means of 3D finite difference time domain simulations.

Dynamical Control of Broadband Coherent Absorption in ENZ Films.

Interferometric effects between two counter-propagating beams incident on an optical system can lead to a coherent modulation of the absorption of the total electromagnetic radiation with 100% efficiency even in deeply subwavelength structures. Coherent perfect absorption (CPA) rises from a resonant solution of the scattering matrix and often requires engineered optical properties. For instance, thin film CPA benefits from complex nanostructures with suitable resonance, albeit at a loss of operational bandwidth. In this work, we theoretically and experimentally demonstrate a broadband CPA based on light-with-light modulation in epsilon-near-zero (ENZ) subwavelength films. We show that unpatterned ENZ films with different thicknesses exhibit broadband CPA with a near-unity maximum value located at the ENZ wavelength. By using Kerr optical nonlinearities, we dynamically tune the visibility and peak wavelength of the total energy modulation. Our results based on homogeneous thick ENZ media open a route towards on-chip devices that require efficient light absorption and dynamical tunability.

Node to Node Performance Evaluation through RYU SDN Controller

Over the last few years, networks became more innovative for constructing and managing with the support of Software Defined Networking (SDN). The inflexibility of typical network architecture gives a great challenge to researchers. SDN is replacing current inflexible and complex networks with an innovative way where the control plane is decoupled from the data plane and fixing some limitations, including manual configuration, debugging, security, scalability, and mobility. Therefore, SDN controllers (e.g., NOX, POX, ONOS, OpenDaylight, Floodlight, Beacon, RYU, etc.) have emerged as a brain to manage such networks. SDN controller’s performance study provides an excellent impact on enhancing the flexibilities and capabilities of an underlying SDN infrastructure network. This paper contextualizes the performance test analysis on the SDN controller is carried out through criterion (e.g., Throughput, Round-Trip Time, etc.). To implement an SDN architecture, this work uses a Mininet emulator containing a controller RYU with switching hub component, one OpenFlow switch, and three nodes. The aim is to evaluate the performance parameters such as Bandwidth, Throughput, Round-Trip Time, Jitter, and Packet loss between nodes using the RYU controller.

High-Fidelity Router Emulation Technologies Based on Multi-Scale Virtualization

Virtualization has the advantages of strong scalability and high fidelity in host node emulation. It can effectively meet the requirements of network emulation, including large scale, high fidelity, and flexible construction. However, for router emulation, virtual routers built with virtualization and routing software use Linux Traffic Control to emulate bandwidth, delay, and packet loss rates, which results in serious distortions in congestion scenarios. Motivated by this deficiency, we propose a novel router emulation method that consists of virtualization plane, routing plane, and a traffic control method. We designed and implemented our traffic control module in multi-scale virtualization, including the kernel space of a KVM-based virtual router and the user space of a Docker-based virtual router. Experiments show not only that the proposed method achieves high-fidelity router emulation, but also that its performance is consistent with that of a physical router in congestion scenarios. These findings provide good support for network research into congestion scenarios on virtualization-based emulation platforms.

Influence of wavelength on the bandwidth of W-type plastic-clad silica optical fibers

The bandwidth and steady-state loss of multimode W-type plastic-clad silica optical fibers are investigated by solving the time-dependent power flow equation. The results show how the bandwidth of W-type plastic-clad silica optical fibers can be enhanced by shifting from the red to the infrared wavelength region for different intermediate layer widths and refractive indices of the outer cladding. Such characterization of these fibers is consistent with their manifest effectiveness in reducing modal dispersion and increasing bandwidth.

Research on negative curvature terahertz fiber based on nested triangle structure cladding

In the terahertz communication and imaging systems, terahertz fibers have aroused great interest in the past several years. Countering the terahertz wave applications ‘inefficient transmission’ calls for a rapid development in terahertz fibers that could achieve low confinement loss, chromatic dispersion and large refraction of power at the same time. In this paper, a new type of negative curvature terahertz fiber is designed, which consists of six cladding tubes evenly distributed in the cladding and nested with equilateral triangle structure. By using full vector finite element method and changing the thickness of cladding tube and triangle, the effective mode field area, core power ratio, confinement loss, dispersion and other parameters of negative curvature fiber are studied. Here, the thickness range of 70–100 μm is selected. It is found that the confinement loss of optical fiber can reach 0.005 dB/cm at 2.36 THz, the dispersion coefficient can float up and down at ±0.1 ps/(THz·cm) at the frequency range of 2.1–2.8 THz, the core power ratio can reach above 99% in the same frequency range. Compared with the known terahertz negative curvature fiber, the nested triangle negative curvature fiber has lower confinement loss and wide transmission bandwidth of 2.1–2.8 THz. After that, when the cladding tube and the triangle thickness are kept at 90 μm, the bending degree of the triangle edge is changed, and the above properties are further studied. When the triangle edge is bent in and out, the transmission performance of the fiber is analyzed. It is found that when the triangle edge is bent inward, the transmission characteristics of terahertz wave is much better than that when the triangle edge is bent outward. When the triangle edge is bent inwards, the confinement loss is obviously reduced, reaching 0.002 dB/cm at 2.36 THz. Compared with triangle straight edge, the confinement loss is reduced by 40% and still maintaining 99% core power ratio at certain frequency band. The designed terahertz fiber will have an important application value in the fields of sensing and imaging systems with low loss and wide bandwidth. This makes the Topas COC-based terahertz fiber very suitable for guiding terahertz wave over the desired frequency range.

Multispectral image denoising methods: A literature review

The Multispectral images appear to give a more true representation of real-world scenes to improve the efficiency of many tasks involving computer vision and object extraction, identification and quantification, tagging operations and imagery segmentation, compared to standard RGB or grayscale images. The use of visible multi-spectral spectrum images as opposed to standard RGB systems enables high colour reproduction characteristics due to the achievement of minimal data from RGB images. Due to the restriction of facilities, restricted bandwidth and radiant energy losses, MSIs are impaired during capture by many noises. The formulation of a new mathematical definition of the deep study model for denoising is a complex investigation problem and several researchers have defined various MSI denoising algorithms or methods. Many researchers suggested its use as a sparse coding of noisy patches in the application of the neural network. These additionally allow different methods to change themselves with an algorithm for a mission. In reality, however, multiple noises often come across a multi-spectral image. We presented in this study the previous techniques for the MSI influenced by noise. The literature survey explains the description and advantages of previous approaches relative to each other.

A Novel 1-Bit Reconfigurable Transmitarray Antenna Using a C-Shaped Probe-Fed Patch Element With Broadened Bandwidth and Enhanced Efficiency

A 16 ×16 -element reconfigurable transmitarray antenna (RTA) is designed and experimented in this paper. The proposed element consists of a receiving (Rx) structure and a transmitting (Tx) structure. The rectangular patch with C-shaped probe-fed is designed as the Tx structure to obtain the characteristics of broad bandwidth and low loss, where the U-shaped slot patch is designed as the Rx structure to obtain simple structure. Two PIN diodes are symmetrically integrated on the C-shaped feeding line. By turning them ON or OFF simultaneously, the induced current directions are reversed, thus achieving two phase states with 180° phase difference. The low insertion loss of 0.47 dB and the 3-dB transmission bandwidth of 16.0% are achieved by employing the stepped impedance matching technique. A Ku-band 256-element reconfigurable prototype with 512 PIN diodes is designed, fabricated, and measured. The measured peak gain at 12.2 GHz are 22.1 dBi with aperture efficiency of 21.2% and a 3-dB gain bandwidth of 12.3%. The measured results demonstrate the two-dimensional electronic beam scanning capability within ±60° as well. The proposed 1-bit RTA design exhibits good radiation performance, making it a promising candidate for advanced wireless communication applications.

Design and Implementation of Self-Expanding System of Unmanned Vehicles Group Based on Signal Strength

Unmanned vehicles are widely used in the military field. They are equipped with a wide variety of sensors so that they can flexibly complete tasks such as enemy surveillance. At present, unmanned vehicles generally control the movement by an obstacle avoidance system or an ultrasonic ranging system without considering the signal strength, which may cause poor communication. In this paper, we present a model based on signal strength for unmanned vehicles self-expansion to solve the problem. In the experiment, we consider and measure the relationship between signal strength, network bandwidth and packet loss rate, and select the optimal signal strength threshold. By applying this model, the vehicles group can realize the self-expansion and multi-hop communication of the vehicles in the network, which make the vehicles reach the maximum coverage areas and the optimal communication quality.

Enabling Technology in High-Baud-Rate Coherent Optical Communication Systems

High-baud-rate coherent optical system is essential to support the ever-increasing demand for high-speed applications. Owing to the recent progress in advanced modulation formats, over 1 Tb/s single-carrier data transmission has been achieved in the laboratory, and its commercial application is envisioned in the near future. This paper presented the trend of increasing baud rate and utilizing high-order quadrature-amplitude modulation (QAM), and several enabling technologies in the coherent optical communication systems. We first discussed recent progress of high-order QAM system and digital signal processing technology. Furthermore, we compared the transmission performance of three different ultrahigh-order QAM formats. The paper then reviewed the commonly used methods of achieving over 100 GBaud optically modulated signals. Besides, five attractive modulators and their corresponding modulation structures are illustrated. Key performance parameters including electrode length, 3-dB bandwidth, half-wave voltage, extinction ratio and optical loss are also compared. Finally, the trade-off between the baud rate and QAM orders in implementing high-speed systems are investigated in simulations. The results show that for the coming 800 GbE or 1.6 TbE, PDM-64-QAM might be an idea choice by considering the trade-off between the link reach and required system bandwidth. By adopting the latest probabilistic shaping technology, higher-order QAM signals, such as PS PDM-256-QAM, could be favorable for long reach applications while using extra system bandwidth.

Resource and Network Management for Satellite Communications Systems: A Chance-Constrained Approach

In this paper, we propose an optimization framework for the resource and network management in large-scale satellite communications (SATCOM) systems with stochastic and time-varying communication requests. Because further expansions of SATCOM systems are expected in the near future, it is of practical importance to develop management methodologies for efficiently and robustly operating large-scale SATCOM systems. To address this problem, in this paper, we formulate a SATCOM network optimization problem within the framework of the chance-constrained model predictive control. In this problem, we require that a joint chance constraint on the bandwidth loss rate is satisfied with a user-specified performance and probability. Because the joint chance constraint is nonlinear in design variables, we relax the constraint to a linear deterministic one for reformulating the original problem into a relaxed deterministic problem. We numerically verify that the proposed method outperforms a baseline methodology and therefore allows us to efficiently manage large-scale SATCOM systems.