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In this study, we experimentally demonstrate a PPLN-based free-space to SMF (single-mode fiber) conversion system capable of efficient long-wavelength down-conversion from 518 nm, optimized for minimal loss in highly turbid water, to 1540 nm, which is ideal for low-loss transmission in standard SMF. Leveraging the nonlinear optical properties of periodically poled lithium niobate (PPLN), we achieve a wavelength conversion efficiency of 1.6% through difference frequency generation while maintaining a received optical signal-to-noise ratio of 10.4 dB. Our findings underscore the potential of integrating PPLN-based wavelength conversion with fiber optic networks, offering a viable solution for next-generation optical sensor systems that demand real-time, low-latency, and reliable data transmission. This work represents a significant advancement in developing robust and efficient optical sensor technologies, addressing the challenges associated with long-distance transmission and broad-linewidth light sources in optical remote sensing applications. [ABSTRACT FROM AUTHOR]

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In this study, we report a cross gain modulation (XGM)-based Indium Phosphide (InP) photonic integrated wavelength conversion of 128 GBaud DP-16QAM signals in semiconductor optical amplifiers (SOAs). An Indium Phosphide photonic integrated circuit (InP-PIC) is most advanced platform for variety of applications including free space optical communications, microwave photonics, and LiDAR (light detection and ranging). The InP-PIC consists two cascaded Semiconductor optical amplifiers (SOAs), integrated band pass filter and a delay-line interferometer (DLI) filter to exploit double stage cross gain modulation (XGM). The wavelength converter is characterized at various power levels over a wide range of converted wavelengths. The system performance is analyzed using bit error rate (BER), Extinction ratio (ER), ON-OFF gain and conversion efficiency (CE). BER is measured over a received power range of -12 dBm to 4 dBm. At , power penalties are lowered to less than 1 dB for down-converting signals and 2 dB for up-converting signals, respectively. A 12 dB gain in CE is achieved over a 60 nm frequency shift. Measured valued of ER are 15.2 dB, 14.5 dB, and 12.95 dB for back-to-back (b2b), down-conversion, and up-conversion at 128 GBaud (1 Tbps) spanning a wavelength range of 35 nm from 1525 nm to 1565 nm. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a novel dual-pump feedback-based polarization-insensitive wavelength conversion technique using four-wave mixing (FWM) in highly nonlinear fiber (HNLF). By feeding the residual pumps at the output of the HNLF back to the fiber in orthogonal polarization state with respect to the original forward path pumps, we achieve approximately 6 dB improvement in FWM conversion efficiency with negligible polarization sensitivity. A simple theoretical treatment of polarization independent operation is presented. The experimental results closely match the theory and simulation results. Comprehensive comparisons with co-polarized dual pumps, orthogonal pumps, and single pump schemes highlight the significant reduction in polarization sensitivity from over 8 dB in the single pump scheme to approximately 0.7 dB, by the proposed scheme. As an application to the proposed technique, we experimentally demonstrate successful wavelength conversion of 10 and 20 Gbps 4-PAM format signals from 1552.58 nm to 1554.28 nm.

In this article, a power-split-based wireless charging system (WCS) with communication-free coordination control is proposed to combat wide load and coupling variations. By using a magnetic integrated inductor, two power delivery channels are created from a single receiver coil. Large portion of received energy is directly delivered to the load. Small amount of energy is converted by using a low-voltage low-power dc–dc converter to regulate the output voltage or current achieving constant voltage (CV) or constant current (CC) charging operation. This proposal achieves higher power conversion efficiency than the traditional two-stage cascaded converter WCS. Since the dc–dc converter only processes partial power of the WCS system, this proposal reduces the voltage stress of the devices and design difficulty. A communication-free coordination control is applied, which is established by sensing the input current drop caused by the burst operation of the partial-power dc–dc converter. Thus, the CC-CV charging is realized by PWM control at the receiver (Rx) side, and the inverter is regulated with subharmonics control scheme to maintain nearly constant Rx coil current. Simulation results for both high-voltage high-power scenarios and low-voltage low-power (LVLP) scenarios are provided to investigate the operation of the proposed WCS. Finally, experimental results are captured from a 250 W/60–84 V LVLP prototype to validate the feasibility and practicability of proposed concept. [ABSTRACT FROM AUTHOR]

The optical signal processing is the future of communication network. High speed all-optical packet routing is one of the essential applications of all-optical networks which is only possible with the development of all-optical logic technology. The development of optical logic elements and circuits are the steps in the growth of this technology and higher speed up to Tbit/sec can be achieved. The optical carrier frequency range 1013 to 1016 Hz provides enormous potential bandwidth with superior information carrying capacity over a long transmission distance. The need of higher capacity is continuing to encourage research in wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM) based transmission systems, which need optical demultiplexing and wavelength conversion technology. Therefore, for high-speed optical networks, it is required to develop the all-optical gates to avoid power consumption in opto-electronics conversion. All optical logic gates perform computing operations, storage and transmission of data using light also known as optical computing. Optical technology promises massive upgrades in the efficiency and speed of computers, as well as significant shrinkage in their size and cost. The non-linear optical device to be used i.e. Semiconductor Optical Amplifier (SOA) has proved to be the promising for all optical functions like wavelength conversion, logic functions, signal representation in all optical domain. Its compact size, high gain, fast response, strong refractive index variation, easy to manufacture and integration, and power efficiency makes it most optimum device for optical signal processing. In this paper, the application of SOA in optical processing is thoroughly reviewed and orient towards the latest application in neural networks. [ABSTRACT FROM AUTHOR]

Accurate and real-time measurement of water cut (WC) and flowrate of oil–water flow is a critical factor in achieving intelligent digital oil field. In this article, a dual-parameter (WC and water flowrate) measurement method for oil–water flow is proposed based on a Venturi embedded with microwave transmission line sensor (V&MS). Dynamic experiments of horizontal fine dispersed oil–water flow are conducted. A two-dimensional finite element simulation model for V&MS under the fine dispersed flow is developed to simulate microwave phase outputs at 0%–100% WC. The simulation results agree with the experiments, providing a low-cost alternative to expensive oil–water dispersed flow tests. Furthermore, it is found that the flow patterns for 0%–10% WC and 40%–100% WC are water-in-oil and oil-in-water flows, respectively, but the flow patterns for 10%–40% WC are dispersions of water-in-oil and oil-in-water flow, and 20% WC is the transition point of the dominant continuous phase. When the water phase is continuous, V&MS has a higher sensitivity to phase signals. Finally, a WC prediction model (40%–100%) is developed by combining a modified Bruggeman model with microwave transmission line theory. Then, a discharge coefficient model is developed and the water flowrate is obtained by combining the pressure drop and the predicted WC. The absolute average relative deviation (AARD) of the predicted WC and water flowrate is 1.49% and 1.54%, respectively. The results suggest that appropriate sensing technology integration can offer a powerful solution for accurate and real-time determination of dual-parameter in oil–water flow systems. [ABSTRACT FROM AUTHOR]

In this study, magnetic field emission (MFE) of the high-power double-D (DD) coil-based wireless charging system is investigated and a shielding technique is proposed. The MFE pattern produced by the DD coils is significantly different from the MFE of the unipolar (e.g., circular, square, or rectangular) coils, and the traditional aluminum shield does not suppress the MFE from the DD coils. This study shows that a conventional aluminum shield increases the MFE, and a magnetic shield effectively suppresses the MFE of the DD coils. Therefore, a magnetic shield consisting of high-permeability magnetic material, such as ferrites, nanocrystalline, etc., is proposed for the DD pads. The shielding effectiveness of the proposed shield is evaluated through finite-element analysis and verified through experiments. An 11-kW DD coil-based wireless charging system was used to test the proposed shielding technique. The experimental results show that a traditional aluminum shield increased the MFE by 29.8%, and the proposed magnetic shield suppressed the MFE by 50.5%. [ABSTRACT FROM AUTHOR]

Enabling simultaneous and high-resolution quantification of the total concentration of hemoglobin ($\text{C}_{{\text {Hb}}}$), oxygen saturation of hemoglobin (sO2), and cerebral blood flow (CBF), multi-parametric photoacoustic microscopy (PAM) has emerged as a promising tool for functional and metabolic imaging of the live mouse brain. However, due to the limited depth of focus imposed by the Gaussian-beam excitation, the quantitative measurements become inaccurate when the imaging object is out of focus. To address this problem, we have developed a hardware-software combined approach by integrating Bessel-beam excitation and conditional generative adversarial network (cGAN)-based deep learning. Side-by-side comparison of the new cGAN-powered Bessel-beam multi-parametric PAM against the conventional Gaussian-beam multi-parametric PAM shows that the new system enables high-resolution, quantitative imaging of $\text{C}_{{\text {Hb}}}$ , sO2, and CBF over a depth range of $\sim 600~\mu \text{m}$ in the live mouse brain, with errors 13–58 times lower than those of the conventional system. Better fulfilling the rigid requirement of light focusing for accurate hemodynamic measurements, the deep learning-powered Bessel-beam multi-parametric PAM may find applications in large-field functional recording across the uneven brain surface and beyond (e.g., tumor imaging). [ABSTRACT FROM AUTHOR]

In this article, we propose application layer coding schemes to recover lost data in delay-sensitive uplink (sensor-to-gateway) communications in the Internet of Things. Built on an approach that combines retransmissions and forward erasure correction, the salient features of the proposed schemes include low computational complexity and the ability to exploit sporadic receiver feedback for efficient data recovery. Reduced complexity is achieved by keeping the number of coded transmissions as low as possible and by devising a mechanism to compute the optimal degree of a coded packet in $\mathcal {O} (1)$. Our major contributions are as follows: 1) an enhancement to an existing scheme called windowed coding, whose complexity is greatly reduced and data recovery performance is improved by our proposed approach; 2) a technique that combines elements of windowed coding with a new feedback structure to further reduce the coding complexity and improve data recovery; and 3) a coded forwarding scheme, in which a relay node provides further resilience against packet loss by overhearing source-to-destination communications and making forwarding decisions based on overheard information. [ABSTRACT FROM AUTHOR]

The article presents an applied physics research on Free-access optomechanical liquid probes using a twin-microbottle resonator. Topics include performance is substantially improved when the optomechanical structure has a high optical and mechanical quality factor; and e applicable condition of cavity optomechanical structures wit focus of interest for metrological applications in biology and rheology.

Although the wireless charging system (WCS) achieves flexible power transmission, high system operating performance needs strong anti-misalignment capability and excellent charging controllability. Hence, this article proposes a mistuned WCS that features dual transmission channels using half-bridge inverters, magnetic flux controlled inductors (MFCIs), magnetic couplers with hybrid coils (HMCs), and the series–series compensation. Then, high misalignment tolerance and high-efficient constant power (CP) charging are achieved. First, the interrelation among the mutual inductance, adjustable inductance, load resistance, charging power, and system efficiency is analyzed based on the optimally designed system structure. Second, the circuit structure and working principle of the MFCI are illustrated. Third, the anti-misalignment capability of the optimized HMC is verified by analyzing its coupling characteristics. Then, the relative spatial position between the two HMCs is determined to ensure the negligible cross-coupling influence. In addition, the closed-loop controller's working principle and design method is analyzed to achieve high-efficient and high-controllable CP charging within a wide range of misalignment distance and load resistance. Finally, the experimental results validate the feasibility of the proposed WCS. For CP charging of 150 W, x- and y-direction misalignment ranges reach ±95% and ±47%, and system efficiency exceeds 90%, superior to the commonly used anti-misalignment methods. [ABSTRACT FROM AUTHOR]

In the evolution of optical networks, spectral efficiency (SE) enhancement has been the most cost-efficient and thus the main driver for capacity increase for decades. As a result, the development of optical transport systems has been focused on the $C$ - and $L$ -bands, where silica optical fiber exhibits the lowest attenuation, and erbium-doped fiber amplifiers provide an efficient solution to compensate for the optical loss. With a gradual maturity in the SE growth, however, the extension of the optical bandwidth beyond the $C + L$ -band is expected to play a significant role in future capacity upgrades of optical networks and, thus, attract increasing research interests. In this article, we discuss the merits and challenges of ultrawideband optical transport systems and networks beyond conventional bands. [ABSTRACT FROM AUTHOR]

Impairments baseband model in-phase and quadrature-phase Imbalance (IQI) and Residual hardware impairments (RHI) are two key factors degrading the performance of wireless communication systems (WCSs), particularly when high-frequency bands are employed, as in 5G systems and beyond. The impact of either IQI or RHI on the performance of various WCSs has been investigated exclusively in a separate way. To fill this gap, in this paper, the joint effect of both IQI and RHI on the performance of a WCS subject to Hyper Fox’s H-fading (HFHF) channel, is investigated. Such a fading model generalizes most, if not all, of well-known fading and turbulence models. To this end, closed-form expressions for the outage probability (OP), Average channel capacity (ACC) under constant power with optimum rate adaptation (ORA) policy, and average symbol error probability (ASEP) for both coherent and non-coherent modulation schemes are derived. Specifically, all the analytical expressions are derived for three different scenarios: (i) ideal Tx and Rx impaired, (ii) Tx impaired and ideal Rx, and (iii) both Tx and Rx are impaired. Further, asymptotic expressions for OP, ACC under ORA policy, and ASEP are obtained, based on which, insightful discussions on the IQI and RHI impacts are made. $\alpha -\mu $ and Málaga $\mathcal {M}$ turbulence with pointing error distribution models have been considered as particular cases of the HFHF distribution. The analytical derivations, endorsed by simulation results, demonstrate that the RF impairments’ effects should be seriously taken into account in the design of next-generation wireless technologies. [ABSTRACT FROM AUTHOR]

Multi-photon microscopy has played a significant role in biological imaging since it allows to observe living tissues with improved penetration depth and excellent sectioning effect. Multi-photonmicroscopy relies onmulti-photon absorption, enabling the use of different imaging modalities that strongly depends on the properties of the sample structure, the selected fluorophore and the excitation laser. However, versatile and tunable laser excitation for multi-photon absorption is still a challenge, limited by e.g. the narrow bandwidth of typical laser gain medium or by the tunability of wavelength conversion offered by optical parametric oscillators or amplifiers. As an alternative, supercontinuum generation can provide broadband excitations spanning from the ultra-violet to far infrared domains and integrating numerous fluorophore absorption peaks, in turn enabling different imaging modalities or potential multiplexed spectroscopy. Here, we report on the use of machine learning to optimize the spectro-temporal properties of supercontinuum generation in order to selectively enhance multi-photon excitation signals compatible with a variety of fluorophores (or modalities) for multi-photon microscopy. Specifically, we numerically explore how the use of reconfigurable (femtosecond) pulse patterns can be readily exploited to control the nonlinear propagation dynamics and associated spectral broadening occurring in a highly-nonlinear fiber. In this framework, we show that the use of multiple pulses to seed optical fiber propagation can trigger a variety of nonlinear interactions and complex propagation scenarios. This approach, exploiting the temporal dimension as an extended degree of freedom, is used to maximize typical multi-photon excitations at selected wavelengths, here obtained in a versatile and reconfigurable manner suitable for imaging applications. We expect these results to pave the way towards on-demand and real time supercontinuum shaping, with further multi-photon microscopy improvements in terms of spatial 3D resolution, optical toxicity, and wavelength selectivity. [ABSTRACT FROM AUTHOR]

The photoluminescent composite, which consists of micro-/nanoscale photoluminescent particles and a polymer matrix, plays a key role in optical wavelength conversion in white-light-emitting diodes (WLEDs). Heat is inevitably generated within the composite due to the energy lost through conversion and cannot be easily dissipated due to the extremely low thermal conductivity of the polymer matrix. Consequently, the composite suffers from a high working temperature, which severely deteriorates its optical performance as well as its long-term stability in WLEDs. To tackle this thermal issue, in this work three-dimensional (3D)-interconnected thermal conducting pathways composed of hexagonal boron nitride (hBN) platelets were constructed inside a photoluminescent composite, using a simplified bubbles-templating method. The thermal conductivity of the composite was efficiently enhanced from 0.158 to 0.318 W/(m∙K) under an ultralow hBN loading condition of 2.67 wt%. As a result, the working temperature of the photoluminescent composite in WLEDs was significantly reduced by 32.9 °C (from 102.3 °C to 69.4 °C, under 500 mA). Therefore, the proposed strategy can improve the heat accumulation issue in photoluminescent composites and thus improve the optical stability of WLEDs. [ABSTRACT FROM AUTHOR]

Second-order optical nonlinearity is the essential concept for realizing modern technologies of optical wavelength conversion. The emerging helical polarization fluid, dubbed helielectric nematic, now makes it possible to design and easily fabricate various polarization structures and control their optical responses. The matter family is demonstrated as an ideal liquid platform for nonlinear optical conversion and amplification with electricreconfigurable tunability. We here develop a universal phase matching theory and reveal a nonclassic chirality-sensitive phase-matching condition in the polarization helices through both the numerical calculation and the experimental validations. The nonlinear optical amplification can be dramatically modulated with a contrast ratio of >100:1 by an in-plane electric field. Furthermore, we employ the director relaxation under electric fields coupled with nonlinear optical simulation to clarify the topology-light interactions. [ABSTRACT FROM AUTHOR]

This article proposes a real-time method to control the contour error for industrial five-axis machine tools by combining the generalized predictive control (GPC) and the feedback correction (FBC) with dynamic contour error estimation (CEE). The CEE is developed by well considering the curve’s curvature and torsion based on Taylor series expansion and Frenet frame theory. By utilizing the spherical linear interpolation, the tool orientation and the tool tip position are synchronized with respect to the curve length. A novel dynamic foot point searching procedure is established to weaken the influences of the tracking errors’ magnitude on the CEE precision. To tackle the transmission effect, the GPC is adopted to predict the servo systems’ outputs, and then, the induced tool pose deviations, which are subsequently utilized to counteract the contour errors, are predicted by constructing Jacobian matrixes. Especially, the FBC loops are constructed to suppress the influences of disturbances and further to reduce the magnitudes of contour errors. Simulations and experiments are conducted to verify the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Practical applications implementing integrated photonic circuits can benefit from nonlinear optical functionalities such as wavelength conversion, all-optical signal processing, and frequency-comb generation, among others. Numerous nonlinear waveguide platforms have been explored for these roles; the group of materials capable of combining both passive and active functionalities monolithically on the same chip is III–V semiconductors. AlGaAs is the most studied III–V nonlinear waveguide platform to date; it exhibits both second- and third-order optical nonlinearity and can be used for a wide range of integrated nonlinear photonic devices. In this review, we conduct an extensive overview of various AlGaAs nonlinear waveguide platforms and geometries, their nonlinear optical performances, as well as the measured values and wavelength dependencies of their effective nonlinear coefficients. Furthermore, we highlight the state-of-the-art achievements in the field, among which are efficient tunable wavelength converters, on-chip frequency-comb generation, and ultra-broadband on-chip supercontinuum generation. Moreover, we overview the applications in development where AlGaAs nonlinear functional devices aspire to be the game-changers. Among such applications, there is all-optical signal processing in optical communication networks and integrated quantum photonic circuits. [ABSTRACT FROM AUTHOR]

Hence, the load of traffic which is offered equals HT ht NUTs. The frequency slices width is hence given as HT ht . An optical carrier, which uses a MF HT ht , is allowed to carry a BR HT ht . We generate the results using the HT ht method and evaluate the performances considering the traffic which is accepted for a 1 % of the BwBP threshold value. [Extracted from the article]

The optical parametric amplifier (OPA) has attractive features for optical communications, such as a wideband, high gain, and fast transient response. In addition, by using idler light, which is phase-conjugated light generated in the amplification process, various kinds of optical signal processing, such as fiber-nonlinearity mitigation, wavelength conversion, and phase-sensitive amplification, can be performed. A periodically poled LiNbO3 (PPLN) waveguide is an χ(2)-based optical parametric amplification medium, and it makes both wideband and high-gain amplification possible. We developed a 4-port PPLN module that can combine signal light and pump light into a PPLN waveguide with low loss. In this paper, we overview the applications of OPA to WDM optical fiber transmission and explain the configurations of an OPA using 4-port PPLN modules. As applications of our PPLN-based OPA, we introduce the demonstration of wideband inline amplification exceeding 5 THz. Furthermore, we demonstrate inter-band wavelength conversion between C- and S-bands using PPLN waveguides developed for multi-band optical transmission applications. [ABSTRACT FROM AUTHOR]

The internet heavily relies on optical networks to carry an increasingly growing amount of traffic. This paper analyzes and explores different ways and architectures to efficiently scale terrestrial core optical networks. Discussed and reviewed are several means to increase network capacity and their potential to address the anticipated growth. Finally, a full network simulation allows to gauge the merit of the proposed architectures which allow for a seamless transition between wavelength switched and band or fiber switched core networks while gradually benefiting from the increased cost efficiency of the latter. [ABSTRACT FROM AUTHOR]

We focus on different modes in MO nanophotonic devices with an emphasis on the recent development of novel magneto-nanophotonic structures and the observation of new MO effects in both magnetoplasmonic and all-dielectric MO nanostructures. Keywords: all-dielectric resonator; biosensor; chiromagnetic metasurface; magnetic field sensing; magneto-optical effects; magnetoplasmonics EN all-dielectric resonator biosensor chiromagnetic metasurface magnetic field sensing magneto-optical effects magnetoplasmonics 2639 2659 21 05/19/22 20220601 NES 220601 Abbreviations PMOKE polar magneto-optical Kerr effect TMOKE transverse magneto-optical Kerr effect LMOKE longitudinal magneto-optical Kerr effect BIG bismuth iron garnet SPR surface plasmon resonance LSPR localized surface plasmon resonance PSPR propagating surface plasmon resonance SLR surface lattice resonance LMPIE longitudinal magneto-photonic intensity effect FOM figure of merit TMPIE transverse magnetophotonic intensity effect EIT electromagnetically induced transparency BIC bound state in continuum LOD limit of detection MOSPR Magneto-optical surface plasmon resonance 1 Introduction Faraday first studied the interaction between light and magnetism in 1845 [[1]] and Kerr studied it in magnetized materials in 1877, 1878 [[2]]. We discuss the recent development of magnetoplasmonic nanostructures, which features the observation of dark mode-induced strong MO effects, asymmetric/aperiodical plasmonic structures induced multiband MO effect enhancement, observation of optical gyromagnetism, and chiral magnetoplasmonic devices. Magnetoplasmonic and all-dielectric MO nanostructures allow magnetic field-induced modulation of the amplitude and phase of each nanostructure, which adds the "time" degree of freedom. [Extracted from the article]

The integration of optical receivers in nanoscale CMOS technologies is challenging due to less intrinsic gain and more noise compared to SiGe BiCMOS technologies. Recent research revealed that low-noise, high-gain, and low-power CMOS optical receivers can be designed by limiting the bandwidth of the front-end followed by equalization techniques that benefit from good switching characteristics offered by CMOS technologies. In this tutorial brief, the operation of decision-feedback equalization, feed-forward equalization, and continuous-time linear equalization is reviewed in the context of high baud-rate 2-PAM and 4-PAM modulation. Recent advances and techniques in 4-PAM optical receivers are reviewed and compared in terms of speed, sensitivity, bandwidth, and efficiency. [ABSTRACT FROM AUTHOR]

The excessive use of nodes and communication links in a wireless control system (WCS) causes unnecessary utilization of resources. In this article, a strategic topological formation is studied for a WCS, where a previously proposed topology consisting of a plant system, a controller system, and an intermediate network system is further developed. More specifically, this article presents a modeling framework and a design procedure for the topology that results in the utilization of a reduced number of nodes and communication links. It also discusses several conditions for the connectivity of the nodes under different topological scenarios. This article uses a four-tank process system as an application example to demonstrate the strategic topological formation of its WCS. [ABSTRACT FROM AUTHOR]

An improved locally 1-D (LOD) finite-difference time-domain (FDTD) method with a one-step leapfrog scheme has been developed, and its numerical dispersion has been further optimized due to the introduction of controlling parameters. On the premise of unconditional stability, we further simplified the implementation through auxiliary field variables. Moreover, the internal relationship between numerical dispersion and important parameters, such as propagation angle, the Courant–Friedrich–Levy number, and frequency, was analyzed in detail. Numerical examples verified the performance of the proposed method in terms of memory, efficiency, and accuracy. [ABSTRACT FROM AUTHOR]

Manual titration of positive airway pressure (PAP) is a gold standard to provide an optimal pressure for the treatment of obstructive sleep apnea-hypopnea syndrome (OSAS). Since manual titration studies were costly and time-consuming, many statistical models for predicting effective PAPs were reported. However, the prediction accuracies of the models associated with nocturnal parameters still remain low. This study proposes a fuzzy neural prediction network (FNPN) with input candidate variables, selected among easily available measurements (e.g., body mass index (BMI), waist circumstance (WC), and body composition) and OSAS related questionnaires, to rapidly predict an optimal PAP. The FNPN comprises fuzzy rules and is characterized with the ability of automatic rule growing and pruning from training data. A total of 147 participants from April 2018 to April 2019 were enrolled in Taichung Veterans General Hospital, Taiwan. After two selection processes for feature extraction, WC and BMI were the significant variables for entering the FNPN to predict optimal PAP. Experimental results showed that the average successful prediction rate of the proposed method was 71.8%. This study also found that Epworth sleepiness scales (ESS) and body composition, such as visceral fat area and percent body fat, were excluded in the final prediction model. Compared with existing models, the proposed prediction approach provided a rapid prediction of optimal PAP with higher accuracy. [ABSTRACT FROM AUTHOR]

In this article, a multifunctional optical processing unit for differential eight phase‐shift‐keying (D8PSK) and differential quadrature phase‐shift‐keying (DQPSK) based on four‐wave mixing (FWM) effects in semiconductor optical amplifier (SOA) is proposed. All‐optical wavelength conversion, D8PSK‐to‐DQPSK format conversion and signal encryption of 10‐Gbaud DQPSK and D8PSK optical signals are achieved simultaneously by simulation. Detailed theoretical analysis and simulation results are conducted to verify the feasibility of the scheme. The Q factor of the electrical signals and the bit error rate recovered from wavelength and format converted components are approximated to be around 6, and 10−9, which indicates the feasibility of the scheme. For the encrypted signal, the FWM effect of another SOA is utilized to decrypt the encrypted signal, and the encryption function of 10‐Gbaud DQPSK and D8PSK optical signals is also verified. [ABSTRACT FROM AUTHOR]

As a member of the MXene family, tungsten carbide (WC), with its unique physical structure and excellent optical properties, possesses enormous development potentials in ultrafast optoelectronics. In this letter, A WC film saturable absorber (SA) is successfully demonstrated to induce passive Q-switching in an erbium-doped fiber laser (EDFL). The WC nanoparticles (NPs) are synthesized by a hydrothermal method. Stable Q-switched pulses are generated at 1558 nm with a threshold pump power of 141 mW, after inserting the prepared WC film into the EDFL ring cavity. As the pump power ranges from 141 mW to 193 mW, the repetition rate increases from 32.34 kHz to 35.8 kHz, while the pulse duration decreases from $5.5~\mu \text{s}$ to $4.16~\mu \text{s}$. When the pump power reaches a maximum power of 193 mW, the corresponding maximum pulse energy and output power are 81 nJ and 2.9 mW, respectively. To our best knowledge, this is the first report of utilizing WC as SA to achieve Q-switched pulses. Our research results provide a new reference for the realization of pulsed laser using MXene materials and reveal that WC has immense applications in nonlinear optics and ultrafast laser technology, which greatly broadens the frontier of materials for optoelectronic techniques. [ABSTRACT FROM AUTHOR]

To realize the misalignment insensitivity and stable constant current/voltage (CC/CV) charging without using the extra dc–dc converter, composite compensation topology, and wireless communication modules, a primary-side control method based on the phase-shift full-bridge inverter and the laminated magnetic coupler (LMC) is proposed for the wireless charging system. First, the load-independent output current and voltage characteristics for the series–series compensation are analyzed. The equations for estimating the charging current and voltage are deduced by only using the primary-side parameters. Second, the excellent antimisalignment capability of the LMC with the primary-side integrated auxiliary coil is verified. As a result, the influence of horizontal misalignment on the estimation precision is reduced; the controllability of the charging current is ensured. Third, the dual-loop cascade PI controller is designed, and CC/CV charging is realized by adjusting the phase-shift angle. Finally, both the simulation and experimental results show that the primary-side control method realizes CC/CV charging with high precision within the reasonable horizontal misalignment range. Compared to the conventional primary-side control methods, the proposed one avoids both the load resistance estimation and mutual inductance identification. Meanwhile, the compact and lightweight receiver module is ensured. [ABSTRACT FROM AUTHOR]

This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ~1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferred into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs. [ABSTRACT FROM AUTHOR]

In this article, we experimentally demonstrate, for the first time, an all-optical bistable monolithically integrated photonic waveguide memory of distinctive simplicity, relying on two travelling waveguide Semiconductor Optical Amplifiers with Cross Gain modulation (SOA-XGM) phenomena. Experimental proof-of-principle memory operation and wavelength switching operation are demonstrated at 5Gb/s, featuring an Extinction Ratio of 6 dB and a 4.6 dB BER penalty, in the case of the memory operation, as well as a power penalty of 3.5 dB at 10−9 BER value, in the case of the wavelength switching. Being entirely designed and fabricated using standard library-based components, the proposed photonic memory fits within a 3.5 mm waveguide configuration of a generic monolithic InP platform, while its overall footprint is $3.5\times 2$ mm2 demonstrating a footprint reduction of 40% compared to previous hybrid SOA-MZI SR-FF architectures, holding the credentials for a fast photonic memory unit. [ABSTRACT FROM AUTHOR]

Radar-embedded communication (REC) systems use a series of radar echoes as a mask to send covert communication signals. In this article, we consider a multiapproach method to improve the reliability of the message reception process in REC systems. First, a match-after-filtering strategy is proposed to improve the overall reliability of message reception. Theoretical analysis and simulation results show that, compared with traditional receiving methods, this strategy can dramatically improve the reliability of message reception. Second, precise radar waveform extraction is necessary for communication waveform construction. To precisely extract the radar waveform at the radio frequency tag, we propose an extraction technique using array processing. Finally, in many REC systems, smooth multiple signal classification algorithms and reiterative super-resolution (RISR) algorithms are used for the direction of arrival (DOA) estimation. We develop an improved RISR algorithm, based on a least squares model, to improve DOA estimation accuracy without increasing the complexity. [ABSTRACT FROM AUTHOR]

We experimentally demonstrated a photoelectric nonlinear compensation scheme of optical phase conjugation (OPC) with complex-valued deep neural network (CVDNN) to mitigate fiber nonlinearity in wavelength division multiplexing (WDM) 64-QAM coherent optical transmission system. The factors to affect the performance of OPC and CVDNN are comprehensively considered. OPC in WDM system is experimentally optimized to alleviate the deployment requirements of strict symmetrical distributed power and chromatic dispersion. The performance penalty caused by the simplification of the OPC is further compensated by the CVDNN. The selections of the input neurons’ number and the optimization algorithm are also considered to design a simple two-hidden-layer-structure CVDNN. The proposed method is experimentally verified and evaluated in a 12.5-GBd 4-channel WDM 64-QAM 160-km standard single-mode fiber (SSMF) transmission system with channel spacing of 50-GHz. The experimental results show that the proposed nonlinear equalizer based on the OPC with CDVNN has a strong robustness to the input signal power and wavelength, which can not only improve the Q factor of the signal by 1.5-dB, but also greatly increase the total launched signal power. [ABSTRACT FROM AUTHOR]

Robust look-ahead dispatch (RLAD) is essential to manage uncertainties in power systems. As its key step, the worst-case scenario identification (WCSI) problem is cast to a max-min program. This computationally intensive procedure has to be performed repeatedly, impairing the computational efficiency of RLAD. To address this issue, an efficient RLAD scheme incorporating critical region preparation in gap time is proposed. The computation burden is mostly transferred from the online decision stage to the gap time via a customized technique based on multi-parametric programming. The accuracy of computing the critical regions is validated by the test in a six-bus system, and the proposed method is shown to cut down 21% of total iterations and save computational time dramatically by the test in a practical-scale system in Northeastern China. [ABSTRACT FROM AUTHOR]

Water is mixed with the crude oil to form complex multiphase fluid during oil extraction process. Some of the traditional methods to measure the relative amount of water mixed with the crude oil (known as water-cut or WC) are intrusive, which are prone to wear and tear. Few other methods, used for WC sensing, are either unable to cover full range (0-100% WC) or require good mixing of the production fluid to be sensed accurately. This paper presents a unique and robust design of a dual spiral microwave resonator, which has been integrated on the extended throat of a venturi. Venturi measures the flow rate of the overall fluid while the microwave resonator measures the relative fraction of water in oil. Unlike existing meters, the presented design is fully non-intrusive, covers full WC range and does not require any mixing of production fluid for accurate measurement. The meter has been designed to withstand harsh field conditions of 1000 psi pressure and 125°C temperature and its performance has been validated in a commercial industrial flow loop with variable salinity conditions. “Phase inversion” phenomenon where the mixture changes from “oil continuous” to “water continuous” or vice versa, has been characterized thoroughly under varying test conditions. Microwave sensor’s resonance frequency (${\text f}_{o}$) and quality (Q) factor are used to measure WC in oil continuous and water continuous conditions respectively. The meter has been tested over wide range of flow rates and full range (0-100%) of WC. Liquid flow rate accuracy of ±3% and water cut accuracy of ±2% has been obtained from the industrial flow loop measurements. [ABSTRACT FROM AUTHOR]

We present a scheme for spatial-mode-selective frequency conversion in a few-mode fiber and experimentally demonstrate upconversion of arbitrary superpositions of LP01 and LP11a signal modes from C-band to the fundamental mode in S-band with all conversion efficiencies within 1 dB range of one another. [ABSTRACT FROM AUTHOR]

We explore the potential of a combination of two fiber parametric wavelength converters and an erbium-doped fiber amplifier to serve as a hybrid amplifier for S-band. We experimentally confirm the validity of a simple quantum model of the wavelength-converter noise figure (NF) and use it to extrapolate the measurement results and find the optimum hybrid amplifier settings. We find that the total NF can be below 6 dB, if the wavelength conversion efficiency of the first stage is above 4 dB. Furthermore, the total NF can be as low as 4 dB, if the conversion efficiency of the first stage is 10 dB or higher. Finally, we estimate the potential impact of pump relative noise on the NF. [ABSTRACT FROM AUTHOR]

Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes in the accretion flow lead to stochastic variability of this emission on a wide range of time scales. We measured the optical continuum variability observed in 67 active galactic nuclei and the characteristic time scale at which the variability power spectrum flattens. We found a correlation between this time scale and the black hole mass extending over the entire mass range of supermassive black holes. This time scale is consistent with the expected thermal time scale at the ultraviolet-emitting radius in standard accretion disk theory. Accreting white dwarfs lie close to this correlation, suggesting a common process for all accretion disks. [ABSTRACT FROM AUTHOR]

The fault riding-through (FRT) capability is a key problem in the dc distribution network. In order to achieve the FRT, it is necessary to analyze the worst-case scenario (WCS) of the short-circuit transient process of distribution components. This article analyzes the whole fault characteristic in a dual active bridge (DAB) in the WCS when a short-circuit occurs on the load at different locations that has not been considered in the existing literature. The short-circuit in the WCS can cause various fault current in the whole circuit, introducing a risk of the overcurrent. In order to overcome this problem, FRT-based methods are proposed in this article. One of the methods is to block the power switches for a certain period and restart the circuit, and another is to add a series output inductor with a reasonable inductance. By these methods, the faulty branch can be cut off by the corresponding circuit breaker in time. The results are verified by the simulations on a 50-kW DAB by MATLAB/Simulink, and the experiments on a 3-kW prototype. The results presented in this article provide a theoretical reference for FRT of DABs. [ABSTRACT FROM AUTHOR]

Surface states generally degrade semiconductor device performance by raising the charge injection barrier height, introducing localized trap states, inducing surface leakage current, and altering the electric potential. We show that the giant built-in electric field created by the surface states can be harnessed to enable passive wavelength conversion without utilizing any nonlinear optical phenomena. Photo-excited surface plasmons are coupled to the surface states to generate an electron gas, which is routed to a nanoantenna array through the giant electric field created by the surface states. The induced current on the nanoantennas, which contains mixing product of different optical frequency components, generates radiation at the beat frequencies of the incident photons. We utilize the functionalities of plasmon-coupled surface states to demonstrate passive wavelength conversion of nanojoule optical pulses at a 1550 nm center wavelength to terahertz regime with efficiencies that exceed nonlinear optical methods by 4-orders of magnitude. Semiconductor surface states often stand in the way of device performance, but here, the authors take advantage of them for wavelength conversion. They present a compact, passive conversion device insensitive to optical alignment by using plasmon-coupled surface states that enable the efficient conversion without nonlinear phenomena. [ABSTRACT FROM AUTHOR]

Computation of the internal electric field induced in the human body by low-frequency power systems is time-consuming. We compute an approximate solution in nearly real time by using a reduced basis for the internal field. The basis is computed once (off-line) by approximating the source by multipoles, the coefficients of which can be computed for any position of the human body due to analytic translation and rotation formulas. The results are validated with respect of finite element method (FEM) computation. [ABSTRACT FROM AUTHOR]

Modal phase matching (MPM) is a widely used phase matching technique in AlxGa1−x As and other χ(2) nonlinear waveguides for efficient wavelength conversions. The use of a non-fundamental spatial mode compensates the material dispersion but also reduces the spatial overlap of the three interacting waves and therefore limits the conversion efficiency. In this work, we develop a technique to increase the nonlinear overlap by modifying the material nonlinearity, instead of the traditional method of optimizing the modal field profiles. This could eliminate the limiting factor of low spatial overlap inherent to MPM and significantly enhance the conversion efficiency. Among the design examples provided, this technique could increase the conversion efficiency by a factor of up to ~ 290 in an AlxGa1−x As waveguide. We further show that this technique is applicable to all χ(2) material systems that utilize MPM for wavelength conversion. [ABSTRACT FROM AUTHOR]

Access-metro convergence networks (AMCN) have been proposed as a future optical communication network to realize flexible and dynamic bandwidth allocation. An AMCN requires transceivers with different wavelengths for the optical network units (ONUs). This causes an increase in production costs. Although an all-optical wavelength converter (AOWC) mitigates this issue, the AOWC increases the installation cost because it consists of many expensive optical devices. We propose the use of a remotely pumped AOWC (RP-AOWC) with an AMCN. The proposed technique can reduce the number of pump light sources in the AOWC. This paper demonstrates this reduction in the number of light sources and the feasibility of wavelength conversion using pump light propagation. We calculate the reduction in the number of pump sources and the number of transceiver types caused by the use of RP-AOWC and experiment with the wavelength conversion using pump light propagation. [ABSTRACT FROM AUTHOR]

Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO2 films form on Te surfaces, as a result of irradiation, with an interface layer of amorphous Te intervening between them. It is shown that irradiation, apart from enabling the controllable transformation of bulk Te to onedimensional nanostructures, such as Te nanotubes and hybrid core-Te/sheath-TeO2 nanowires, causes also a series of light-driven (athermal) phase transitions involving the crystallization of the amorphous TeO2 layers and its transformation to α multiplicity of crystalline phases including the γ-, β-, and α-TeO2 crystalline phases. The kinetics of the above photo-induced processes is investigated by Raman scattering at various laser fluences revealing exponential and non-exponential kinetics at low and high fluence, respectively. In addition, the formation of ultrathin (less than 10 nm) layers of amorphous TeO2 offers the possibility to explore structural transitions in 2D glasses by observing changes in the short- and medium-range structural order induced by spatial confinement. [ABSTRACT FROM AUTHOR]

High‐yield wavelength conversion is one of the key requirements for efficient photon energy harvesting. Attempts to realize efficient conversion by simply stacking layers of chromophores have failed so far, even when using highly crystalline assemblies and employing the recently discovered long‐range (>100 nm) Förster resonance energy transfer (LR‐FRET). Optical conversion efficiency is drastically improved using chromophoric metal–organic framework heterolayers fabricated layer‐by‐layer in connection with an "antenna doping" strategy. Systematic investigations reveal that the LR‐FRET mechanism, reported previously in chromophoric aggregates, is highly anisotropic for neat materials but can be made more isotropic by employing doping strategies. Using optimized fabrication parameters and dopant concentrations, a three‐layer, two‐step cascade with an overall optical conversion efficiency of ≈75% is realized. [ABSTRACT FROM AUTHOR]

We report the design of a microstructured silica-based fiber for widely tunable soliton self-frequency shift, suitable for pumping with two most common fiber laser wavelengths: 1.04 and 1.55 μm. Depending on the pump source, the output spectrum can be continuously tuned up to 1.67 (pump at 1.04 μm) or 1.95 μm (pump at 1.55 μm) in the same 1.5 m-long fiber sample, with pump-to-soliton conversion efficiency higher than 20%. The fiber is highly birefringent, which results in an excellent polarization extinction ratio of the soliton, reaching 26 dB. The shifted solitons have a high degree of coherence confirmed by pulse-to-pulse interference measurement. The available soliton tuning range covers the wavelengths inaccessible for fiber lasers, e.g., 1.3 μm and 1.7, highly important for multi-photon microscopy and imaging. Our work shows that it is possible to design and fabricate one universal optical fiber that supports soliton shift when pumped at two different wavelengths separated by over 500 nm. [ABSTRACT FROM AUTHOR]

Toward wireless medical microrobot applications driven by an electromagnetic actuation (EMA) system, challenges associated with movability, the electromagnetic force, and the coil system size must be addressed. This paper presents an enhanced EMA system with a higher magnetic field via new coil configurations, an independent magnetic field control method, and application to the multi-degree-of-freedom (DOF) motion of an untethered capsule endoscope. The magnetically actuated capsule endoscope (MACE) system proposed herein consists of an endoscopic capsule with a permanent magnet in the body, eight air-cored stationary electromagnetic coils, and a control system. The coil system is designed to maximize the working space available within a limited equipment space. The MACE is designed to perform full 5-DOF motion, including 3-DOF translation and 2-DOF rotation. The independent magnetic field control method with the new coil configuration enables orientation-independent-driving (OID) control of the capsule endoscope that could not be accomplished by previous EMA systems. The developed system performance was verified by simulations and experiments. The MACE motion in the spatial domain was evaluated with a robotic endoscopic procedure and diagnostic performance by in-vitro and ex-vivo experiments. [ABSTRACT FROM AUTHOR]

Due to the lack of optical buffer, high packer loss caused by packet contention is one of the main challenges for the optical switching data centers (DCs). Flow control (FC) protocol employing electrical buffers at the top of racks (ToRs) and exploiting packet retransmission mechanism in case of contention has been extensively investigated to decrease the packet loss in optical DCs. However, the packet retransmission and the head-of-line (HOL) blocking in electrical buffers at substantial load traffic introduce extra latency and buffer-overflow that still cause packet loss. To overcome these issues, a novel contention resolution technique based on a software-defined networking (SDN) enabled optical polling flow control is proposed and experimentally assessed in this article. Experimental assessments show that the proposed contention resolution scheme achieves zero packet loss and 7.4 μs latency performance at the load of 0.4. In addition, we numerically modelled and investigated the scalability of the proposed contention resolution technique in a large scale DCN based on the experimental parameters. Results prove the excellent scalability performance of OPFC scheme, in which the packet loss increases from 2.1E-3 to 9.02E-3 and the average latency increases 5.17 μs at the load of 0.5 as the OPFC based network scales from 4 to 40960 servers. [ABSTRACT FROM AUTHOR]