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In this paper, an improved complex-valued convolutional neural network (CvCNN) structure to be placed at the received side is proposed for nonlinearity compensation in a coherent optical system. This complex-valued global convolutional kernel-assisted convolutional neural network equalizer (CvGNN) has been verified in terms of Q-factor performance and complexity compared to seven other related nonlinear equalizers based on both the 64 QAM experimental platform and the QPSK numerical platform. The global convolution operation of the proposed CvGNN is more suitable for the calculation process of perturbation coefficients, and the global receptive field can also be more effective at extracting effective information from perturbation feature maps. The introduction of CvCNN can directly focus on the complex-valued perturbation feature maps themselves without separately processing the real and imaginary parts, which is more in line with the waveform-dependent physical characteristics of optical signals. Based on the experimental platform, compared with the real-valued neural network with small convolutional kernel (RvCNNC), the proposed CvGNNC improves the Q-factor by ∼2.95 dB at the optimal transmission power, while reducing the time complexity by ∼44.7%. [ABSTRACT FROM AUTHOR]

The high standard of communication quality in optical access networks makes forward error correction (FEC) schemes, such as LDPC, an integral part of the system. However, pipeline conflict arising from data dependencies is a common issue encountered in the hardware implementation of layered QC-LDPC decoders. This paper proposes an efficient layered decoding architecture to reduce pipeline conflicts without introducing stall cycles. It can solve some of the pipeline conflicts by flexibly reordering the processing order of inter-layer and intra-layer submatrices offline. In addition, the patch method, based on variable-to-check messages, allows for the delayed use of gains between layer iterations, which can further minimize the performance loss caused by the remaining pipeline conflicts. The experimental results on the LDPC code of the IEEE802.16 standard in the OFDM-PON system demonstrate that the proposed architecture has sensitivity improvements of 0.125 dBm and 0.375 dBm, respectively, compared with our previous work and the method described in the other work. The optimized architecture improves the reliability of the decoder and can also make a contribution to efficient PON systems. [ABSTRACT FROM AUTHOR]

In this paper, a 4 amplitude shift keying (4-ASK) fast orthogonal frequency division multiplexing (FOFDM) scheme was experimentally investigated over a turbulent air–water channel for optical wireless communications. The experiment results showed that the 4-ASK-FOFDM modulated signals were not sensitive to weak atmospheric turbulence, and the bit-error rate (BER) was lower than the 7% forward error correction (FEC) limit of 3.8 × 10−3. Under the condition of the same spectra efficiency, the 4-ASK-FOFDM scheme just had a tiny performance penalty compared to the 16-QAM-OFDM scheme. Consequently, the 4-ASK-FOFDM scheme is a promising alternative to the conventional 16-QAM-OFDM scheme in optical wireless communications. [ABSTRACT FROM AUTHOR]

A modulation format identification (MFI) scheme based on multi-dimensional amplitude features is proposed for elastic optical networks. According to the multi-dimensional amplitude features, incoming polarization division multiplexed (PDM) signals can be identified as QPSK, 8QAM, 16QAM, 32QAM, 64QAM and 128QAM signals using the k-nearest neighbors (KNNs) algorithm in the digital coherent receivers. The proposed scheme does not require any prior training or optical signal-to-noise ratio (OSNR) information. The performance of the proposed MFI scheme is verified based on numerical simulations with 28GBaud PDM-QPSK/-8QAM/-16QAM/-32QAM/-64QAM/-128QAM signals. The results show that the proposed scheme can achieve 100% of the correct MFI rate for all six modulation formats when the OSNR values are greater than their thresholds corresponding to the 20% forward error correction (FEC) related to a BER of 2.4 × 10−2. Meanwhile, the effects of residual chromatic dispersion, polarization mode dispersion and fiber nonlinearities on the proposed scheme are also explored. Finally, the computational complexity of the proposed scheme is analyzed, which is compared with relevant MFI schemes. The work indicates that the proposed technique could be regarded as a good candidate for identifying modulation formats up to 128QAM. [ABSTRACT FROM AUTHOR]

Public awareness of preventing pathogenic microorganisms has significantly increased. Among numerous microbial prevention methods, the deep-ultraviolet (DUV) disinfection technology has received wide attention by using the nitride-based light-emitting diode (LED). However, the light extraction efficiency of DUV LEDs and the utilization rate of emitted DUV light are relatively low at the current stage. In this study, a light distribution design (referred to as the reflective system) was explored to enhance the utilization of emitted DUV from LEDs, leading to successful and efficient surface and air disinfection. Optical power measurements and microbial inactivation tests demonstrated an approximately 79% improvement in average radiation power density achieved by the reflective system when measured at a 5 cm distance from the irradiation surface. Moreover, a statistically significant enhancement in local surface disinfection was observed with low electric power consumption. The reflective system was integrated into an air purifier and underwent air disinfection testing, effectively disinfecting a 3 m3 space within ten minutes. Additionally, a fluorine resin film at the nanolevel was developed to protect the light module from oxidation, validated through a 1200 h accelerated aging test under humid conditions. This research offers valuable guidance for efficient and energy-saving DUV disinfection applications. [ABSTRACT FROM AUTHOR]

Photonic routing holds immense significance in the fields of photonic integrated circuits (PICs) for free‐space optical linking. The emergence of programmable metasurfaces with powerful phase regulation capability provides a promising strategy for achieving designated wavefront modulation and thus photonic routing in the optical communication waveband. Here, a bilayer metasurfaces with four‐level codable unit pixels, which realize controllable photonic routing in near‐infrared (NIR) region is reported. The unit pixel of the metasurfaces consists of the underneath amorphous silicon (α‐Si) nanofin and the upper Ge2Sb2Te5 (GST) nano‐antenna, which contribute to the cross‐polarization generation and amplitude modulation of cross‐polarization light, respectively. Each unit pixel can be designated with desired states, thus achieving on‐demand non‐volatile photonic routing for coherent NIR light. In particular, polarization conversion modulation of the tunable metasurfaces comprising identical unit cell with large cross‐polarization switching (≈55%) at ≈1550 nm is demonstrated. Moreover, the metasurfaces with coded unit pixels to realize designated photonic routing are prototyped. The metasurfaces with four‐level programmability portend a new paradigm in NIR photonic routing for PICs. [ABSTRACT FROM AUTHOR]

Optical frequency combs, featuring evenly spaced spectral lines, have been extensively studied and applied to metrology, signal processing, and sensing. Recently, frequency comb generation has been also extended to MHz frequencies by harnessing nonlinearities in microelectromechanical membranes. However, the generation of frequency combs at radio frequencies (RF) has been less explored, together with their potential application in wireless technologies. In this work, we demonstrate an RF system able to wirelessly and passively generate frequency combs. This circuit, which we name quasi-harmonic tag (qHT), offers a battery-free solution for far-field ranging of unmanned vehicles (UVs) in GPS-denied settings, and it enables a strong immunity to multipath interference, providing better accuracy than other RF approaches to far-field ranging. Here, we discuss the principle of operation, design, implementation, and performance of qHTs used to remotely measure the azimuthal distance of a UV flying in an uncontrolled electromagnetic environment. We show that qHTs can wirelessly generate frequency combs with μWatt-levels of incident power by leveraging the nonlinear interaction between an RF parametric oscillator and a high quality factor piezoelectric microacoustic resonator. Our technique for frequency comb generation opens new avenues for a wide range of RF applications beyond ranging, including timing, computing and sensing. In contrast to the commonly studied optical frequency combs, here, the authors demonstrate a radio frequency system able to wirelessly and passively generate frequency combs as a battery-free solution for far-field ranging of unmanned vehicles in GPS-denied settings. [ABSTRACT FROM AUTHOR]

It is crucial to demonstrate a robust correlation between the simulated and manufactured parallel-transmit (pTx) arrays performances to release the currently-used, very restrictive safety margins. In this study, we describe the qualitative and quantitative validation of a simulation model with respect to experimental results for an 8-channel dipole array at 7T. An approach that includes the radiofrequency losses into the simulation model is presented and compared to simulation models neglecting these losses. Simulated S-matrices and individual B1+-field maps were compared with experimentally measured quantities. With the proposed approach, an average relative difference of ~1.1% was found between simulated and experimental reflection coefficients, ~4.2% for the 1st coupling terms, and ~9.4% for the 2nd coupling terms. A maximum normalized root-mean-square error of 4.8% was achieved between experimental and simulated individual B1+-field maps. The effectiveness of the simulation model to accurately predict the B1+-field patterns was assessed, qualitatively and quantitatively, through a comparison with experimental data. We conclude that, using the proposed model for radiofrequency losses, a robust correlation is achieved between simulated and experimental data using the 8-channel dipole array at 7T. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Within the past decade, the aerospace engineering industry has evolved beyond the constraints of using single, large, custom satellites. Due to the increased reliability and robustness of commercial, off-the-shelf printed circuit board components, missions have instead transitioned towards deploying swarms of smaller satellites. Such an approach significantly decreases the mission cost by reducing custom engineering and deployment expenses. Nanosatellites can be quickly developed with a more modular design at lower risk. The Alpha mission at the Cornell University Space Systems Studio is fabricated in this manner. However, for the purpose of development, the initial proof of concept included a two-satellite system. The manuscript will discuss system engineering approaches used to model and mature the design of the pilot satellite. The two systems that will be primarily focused on are the attitude control system of the carrier nanosatellite and the radio frequency communications on the excreted femto-satellites. Milestones achieved include ChipSat to ChipSat communication, ChipSat to ground station communication, packet creation, error correction, appending a preamble, and filtering the signal. Other achievements include controller traceability/verification and validation, software rigidity tests, hardware endurance testing, Kane damper, and inertial measurement unit tuning. These developments matured the technological readiness level (TRL) of systems in preparation for satellite deployment. [ABSTRACT FROM AUTHOR]

In channel coding, reducing power consumption and improving energy efficiency are major challenges in sliding window decoding (SWD) architectures for spatially coupled low-density parity-check (SC-LDPC) codes. In contrast to the well-elaborated literature on energy-efficient decoder implementations of classical LDPC block codes (LDPC-BCs), there is little research on the aforementioned challenges for SC-LDPC codes. Thus, in this paper, we investigate a novel approach for energy-efficient implementation of very high-throughput SWD for SC-LDPC codes. First, our approach proposes an analogy to state-ofthe- art iteration control techniques for LDPC-BC decoders, by dynamically adapting the window size for the decoding of SC-LDPC codes. For this purpose, we derive new algorithms that sequentially activate and/or deactivate the processors inside the window, without loss in error correction performance. Second, we propose an architecture for very high-throughput decoder implementations. Furthermore, to meet the high throughput requirements and improve energy efficiency, we revisit the window-size adaption criteria and slightly relax the derived algorithms in terms of error correction capability. Implementation results of the new revisited full-adaptive decoder in a 12 nm technology show that, at a negligible loss in error correction performance, the proposed adaptive SWD approach improves the energy efficiency by a factor of 1.4 to 3.4 compared to the state-of-the-art in the 4 dB to 7 dB signal-to-noise-ratio (SNR) range. This improvement is further increased up to a factor of 6.5 at higher SNRs.

We consider in this paper the practical implementation of a siftingless quantum key distribution protocol. The protocol is considered siftingless since it combines sifting and error correction in a single step for basis and information reconciliation, respectively. The protocol can be efficiently implemented even assuming the existence of errors in the communication. In this case, the correlations between the legitimate parties can be modeled by a binary symmetric channel with erasures. Specific codes for this channel are included and simulated for intermediate block lengths. Simulation results show that a key reconciliation step carrying simultaneously both basis and information reconciliation can be efficiently implemented.

Event cameras are bio-inspired devices that have revolutionized the acquisition of visual information by mimicking the neural architecture of the eye. These cameras respond asynchronously to changes in scene illumination at the pixel level, providing high-precision time information with low latency, typically in the order of microseconds. In this work, we experimentally evaluate an optical camera communication (OCC) link using an LED-based transmitter and an event camera as the receiver. We propose n-pulse modulation to encode data, adapting the system to the specific characteristics and operational principles of event cameras. The proposed scheme significantly reduces the demodulation complexity compared to other alternatives found in the literature. Furthermore, a set of experiments considering different camera bias sensitivities, encoding duty cycles, and LED radiant fluxes were carried out. The results showed that the BER performance was strongly dependent on the received optical power and the bias sensitivity. In addition, duty cycles between 0.3 and 0.7 at a 200 Hz transmission frequency presented the best performance, with a BER below 1.25 × 10 − 4 , which is under the forward error correction (FEC) limit. This work showcases the cutting-edge capabilities of event-camera-based OCC technology and contributes to the ongoing revolution in optical wireless communication (OWC). [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of cuprous iodide (CuI) has drawn significant attention in the scientific community. In order to investigate the growth methods and environmental conditions on the fluorescence, we first prepared CuI via immersion of copper in hydroiodic acid. This method is beneficial for the growth of large grains (> 20 μm) with intensive red fluorescence emission at 708 nm. The fluorescence has a high quantum yield (34 %), and superior stability. Then we studied the fluorescence behaviors in water. We observed fluorescence quenching, which is due to the energy transfer. Additionally, we studied the effect of temperature on the fluorescence. We found that the fluorescence intensity increased initially then decreased as the temperature increased. The underlying mechanism was analyzed in terms of fluorescence quencher (water) removal and thermal quenching. By controlling heating, we successfully obtained intensive and pure red fluorescence. Finally, we explored the potential application of the red fluorescent of CuI in optical communication. The results demonstrate bit error rates within permissible range of forward error correction, highlighting the superior performance of CuI in optical communication systems. [ABSTRACT FROM AUTHOR]

Free space optical (FSO) communication is a wireless alternative to fiber-based communication as it may provide a backbone emergency communication link in disaster-hit areas. This paper proposes a full duplex millimeter wave (mm-wave) enabled FSO system to provide a high data rate communication link for search and rescue operations. The proposed system consists of a central unit which is connected to multiple unmanned aerial vehicles (UAVs) through an optical-amplify and forward relay over an FSO channel represented by Log-Normal channel model. An optical comb is generated and Laguerre-Gaussian modes of each wavelength of the optical comb are exploited to carry 10 Gbps differential phase shift keying modulated signals. 60 GHz mm-wave signals are generated at the remote UAVs by employing optical heterodyne detection for downlink transmission towards the user equipment. For the uplink transmission, a dedicated wavelength is used to carry 10 Gbps on-off keying baseband data for live streaming of the disaster-hit area. Furthermore, a single hop scheme is employed to counter the non-line of sight issue of the FSO link. The performance of the proposed model is evaluated under different weather conditions and refractive index structure parameter values. A maximum distance of 3.3 km is achieved for clear sky under low turbulence conditions. Moreover, the effect of misalignment due to hovering of the UAVs on the system performance is also investigated and tolerance in the x (horizontal) and y (vertical) directions is observed at the forward error correction BER limit of 10 - 9 . The simulation results reveal that the proposed system has the potential to provide reliable and quick emergency communication services in disaster-struck areas. [ABSTRACT FROM AUTHOR]

For high-speed optical communication systems, laser phase noise (LPN) stands as a pivotal factor influencing the quality of the received signal. Therefore, the employment of a highly accurate carrier phase recovery (CPR) algorithm at the receiving end is indispensable to ensure the reliability of transmission. While a CPR algorithm called principal component-based phase estimation (PCPE) has been proven to be capable of achieving low-complexity and high-performance phase recovery for even-bit quadrature amplitude modulation (QAM) (i.e., square QAM) signals, it is not compatible with traditional cross-shaped odd-bit QAM signals. To circumvent this problem, a signal constellation design scheme based on geometric shaping (GS) is proposed. The pair-wise optimization (PO) algorithm is used to optimize the constellation structure of 32QAM and 128QAM signals in order to obtain results that are compatible with the PCPE algorithm. Monte Carlo simulation results reveal that for odd-bit QAM signals utilizing PCPE for phase recovery, the proposed GS constellations enhance the mutual information (MI) performance across the entire measured signal-to-noise (SNR) range. Moreover, compared with regular 32QAM and 128QAM constellations using the well-known blind phase search (BPS) algorithm, the proposed GS and PCPE scheme can achieve SNR gains of 1.10 dB and 2.59 dB, respectively, when considering the 20% soft-decision forward error correction (SD-FEC) overhead. Verification through commercial simulation software corroborates these findings, demonstrating that the proposed GS constellations are particularly suitable for the PCPE algorithm, especially under conditions of high optical signal-to-noise ratio (OSNR). To the best of our knowledge, this is the first time that the incompatibility between the PCPE algorithm and odd-bit QAM signals has been investigated, and the proposed GS scheme has broadened the application scope of the low-complexity CPR algorithm. [ABSTRACT FROM AUTHOR]

We describe a system with multi‐input multi‐output (MIMO) transmission over 7‐core few‐mode fiber (FMF) by incorporating polarization division multiplexing and mode division multiplexing. Three optical modes with x and y polarizations were used for 42 × 42 MIMO transmission over 7‐core FMF. We simulate the optical MIMO transmission at 20 Gbps with quadrature phase‐shift keying signals. By using the adaptive recursive least squares constant modulus algorithm (RLSCMA) at the receiver side, transmission data is successfully recovered by mitigating the effects of modal delay and mode coupling of received signals. The simulation results show that adaptive RLSCMA can improve the system performance of optical MIMO transmission systems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The blocking probability is studied for improving the quality of service of the network. The call blocking model for mode of operation to determine the types of applications suitable for Generalized Multi-Protocol Label Switched (GMPLS) networks is proposed. The performance of optical network depends upon various parameters such as number of channels, number of sources, traffic intensity which directly affect the blocking probability of the network. A mathematical model of an optical network for blocking probability of cleared calls and holding calls is developed. In the proposed model, blocking probability of the network gets reduced with a large number of servers. The proposed models decrease the blocking probability of the network to a level of 10–40. In addition, the blocking performance for held calls is also analyzed to compare the amount of traffic intensity that can be handled and completed properly with that of the cleared calls probability. The blocking probability is less for cleared calls than that for held calls as more traffic intensity can be handled in case of cleared calls but the chances for call completion increases in case of held calls. [ABSTRACT FROM AUTHOR]

This paper aims to explore the potential benefits and performance enhancements of combining a novel error correction code with polar codes through serial and parallel concatenation. The BGCC-EDAC (Binary to Gray Code Conversion Based Error Detection and Correction) code is a novel forward error correction code that functions as a channel coding technique. It has shown promising results in effectively detecting and correcting errors. This study presents an empirical analysis of the application of serial concatenation of BGCC-EDAC-aided polar code (SC-BPC) and parallel concatenation of BGCC-EDAC-aided polar code (PC-BPC). The simulation results obtained using Cadence 90 nm technology demonstrate that the SC-BPC and PC-BPC architectures presented in this study require fewer hardware resources compared to the other error correction codes currently available. The empirical analysis conducted using MATLAB demonstrates that the proposed codes exhibit a significant performance improvement compared to CRC-aided polar codes. The PC-BPC code proposed in this study exhibits a slight enhancement of 0.18 dB compared to the parallel concatenation technique of CRC-aided polar codes at a bit error rate of 10−4. Similarly, the SC-BPC code introduced in this research displays an identical improvement of 0.3dB when compared to the serial concatenation approach with CRC-aided polar codes at the same BER level. The PC-BPC and SC-BPC architectures are expected to be widely adopted in 5G wireless communication systems due to their advantageous features such as low latency, high throughput, and improved BER performance. [ABSTRACT FROM AUTHOR]

Many disordered lattices exhibit remarkable universality in their low-temperature properties, similar to that found in amorphous solids. Recently, a two-TLS (two-level system) model was derived based on the microscopic characteristics of disordered lattices. Within the two-TLS model, the quantitative universality of phonon attenuation, and the energy scale of 1–3K below which universality is observed, are derived as a consequence of the existence of two types of TLSs, differing by their interaction with the phonon field. In this paper, we calculate analytically and numerically the densities of states (DOS) of the weakly and strongly interacting TLSs. We find that the DOS of the former can be well described by a Gaussian function, whereas the DOS of the latter have a power-law correlation gap at low energies, with an intriguing dependence of the power on the short distance cutoff of the interaction. Both behaviors are markedly different from the logarithmic gap exhibited by a single species of interacting TLSs. Our results support the notion that it is the weakly interacting τ -TLSs that dictate the standard low-temperature glassy physics. Yet, the power-law DOS we find for the S-TLSs enables the prediction of a number of deviations from the universal glassy behavior that can be tested experimentally. Our results carry through to the analogous system of electronic and nuclear spins, implying that electronic spin flip rate is significantly reduced at temperatures smaller than the magnitude of the hyperfine interaction. [ABSTRACT FROM AUTHOR]

Wireless communications using highly directive terahertz (THz) waves exhibit lower immunity to obstructions than microwaves, limiting their applications. This study demonstrates an obstacle-tolerant THz wireless link established by a self-healing Bessel beam at 300 GHz. The Bessel beam is generated by sending a Gaussian beam through a dielectric axicon lens. Furthermore, experiments were conducted to investigate the short-range transmission (98 mm) reception characteristics with and without the dielectric cubic obstacle (7.5 λ in size) and the metallic obstacle (22 λ in length and 8 λ in width) in the Gaussian beam and self-healing Bessel beam cross sections. The maximum attenuation of the received power due to obstruction was 8.8 and 2.2 dB for the Gaussian and Bessel beams, respectively, when the dielectric obstacle is placed in the middle of the transmission path (49 mm from a transmission lens). This study further investigated the bit error rate (BER) characteristics (1 Gbps, on–off keying) with the dielectric obstacle crossing the beam cross section. When the obstacle crosses the Gaussian beam, the BER degrades as the obstacle approaches the optical axis, breaking the wireless link. In contrast, when the obstacle crosses the Bessel beam cross section, the BER is maintained at <3.8 × 10−3 (the forward error correction limit), and the wireless link is maintained. A self-healing beam, such as the Bessel beam, makes the THz wireless link more tolerant than the Gaussian beam to obstacle and expand applications for THz wireless communications. [ABSTRACT FROM AUTHOR]

The optical transmission window around 2000 nm is getting significant attention for terrestrial and deep-space communication due to lowest absorption. Moreover, it is also being considered as an alternate optical window for spectral expansion beyond C-, L-, and U-bands to resolve the capacity related issues of future optical networks. Holmium-doped gain materials have the capacity to emit light in the 2000–2200 nm wavelength range where Thulium-doped gain materials are comparatively inefficient. In this paper, the design of high power and repetition rate tunable actively mode-locked Holmium-doped fiber laser (AML-HDFL) is demonstrated through numerical simulations. The design is based on a single ring cavity for bidirectional transmission of data over optical wireless channel (OWC) at the rate of 25 Gb/s between two high-altitude platform stations (HAPS). A wide wavelength tuning range from 2000–2150 nm at a side-mode suppression ratio (SMSR) of 35 dB is observed. Train of mode-locked pulses having peak power of 21 W, full-width at half maximum (FWHM) of 7.4 ps, pulse energy of 0.148 nJ and signal to noise ratio (SNR) of 40.6 dB is generated. Moreover, the performance of tunable AML-HDFL using 1950 nm pumping is compared with 1840 nm pumping. Performance of the downlink (DL) and uplink (UL) channels are observed using Gamma-Gamma channel model for medium and strong turbulence where forward error correction (FEC) limit of 3.8 × 10 - 3 is achieved between two HAPS that are separated by a distance of 200 km. [ABSTRACT FROM AUTHOR]

Photonics-based computing approaches in combination with wavelength division multiplexing offer a potential solution to modern data and bandwidth needs. This paper experimentally takes an important step towards wavelength division multiplexing in an integrated waveguide-based photonic reservoir computing platform by using a single set of readout weights for up to at least 3 ITU-T channels to efficiently scale the data bandwidth when processing a nonlinear signal equalization task on a 28 Gbps modulated on-off keying signal. Using multiple-wavelength training, we obtain bit error rates well below that of the 1.5 × 10 - 2 forward error correction limit at high fiber input powers of 18 dBm, which result in high nonlinear distortion. The results of the reservoir chip are compared to a tapped delay line filter and clearly show that the system performs nonlinear equalization. This was achieved using only limited post processing which in future work can be implemented in optical hardware as well. [ABSTRACT FROM AUTHOR]

The future digital evolution poses challenges that need to be spectral and energy-efficient, as well as highly reliable and resilient. The non-orthogonal multiple access (NOMA) accomplishes massive connectivity, spectral efficiency, effective bandwidth utilization, and low latency. The proposed work involves the code domain NOMA scheme called Sparse Code Multiple Access (SCMA) which provides shaping gain through multi-dimensional constellation and the best performance in terms of bit error rate (BER). It achieves overloading of users through the non-orthogonal allocation of resources which enhances the spectral efficiency and serves more users. The shaping gain can be further improved by reducing the BER and enhancing the capacity of the channel through constellation shaping. This work employs a probabilistic-shaped (PS) constellation where each symbol is transmitted with different probabilities which achieves a reduction of average symbol power and forward error correction (FEC) through channel coding using polar codes which aid in energy efficiency. The output is two-dimensionally spread over Orthogonal Frequency Code Division Multiplexing (OFCDM) subcarriers to achieve a flexible transmission rate through a variable spreading factor. Computer simulations showed better BER performance under AWGN and Rayleigh channels with remarkable gain in SNR which paves the way for future applications in Fifth Generation (5G) beyond networks. [ABSTRACT FROM AUTHOR]

In the dynamic network environment, real-time video transmission based on streaming protocols will encounter a large number of packet loss issues. This paper proposed an adaptive forward error correction code method based on GA-BP neural network. This method recovered lost data packets by designing adaptive forward error correction codes. Firstly, the paper designed a frame level forward error correction framework, which mainly includes video codec, RS forward error correction codec module, and forward error correction code redundancy calculation module, to simulate the general video transmission environment; Then, the paper designed the GA-BP model and applied it to the redundancy calculation of RS-FEC to achieve a frame level unequal protection scheme; Finally, based on GE channel simulation network, it generated packet loss data, trained offline model, and conducted experimental verification. The experiments results show that compared to StaticRS and DeepRS, this method can recover lost data packets more efficiently with lower redundancy, resulting in higher quality video. [ABSTRACT FROM AUTHOR]

A soft and tunable microwave bandpass Chebyshev microstrip end-coupled filter is demonstrated on a polydimethylsiloxane substrate based on high electrically conductive composites made of silver nanoparticle-covered flakes, even with large strain. To achieve a precise design, key microwave parameters such as the impedance, S-parameters, and transmission matrix are defined as a function of strain. This strain vector polar coordinate is used to represent the relationship between the type and the performance of a filter. Then, the most important Chebyshev or quasi-Chebyshev type of filter can be accurately realized by looking up its polar coordinates to find the corresponding strain magnitude and direction of stretching. An end-coupled Chebyshev microstrip bandpass filter with a center frequency of 12.8 GHz and bandwidth of 22% was designed and fabricated for demonstration. Experimentally, at a lateral elongation of 8% and 10.7%, the center frequency decreases by 0.61 and 0.88 dB, respectively, matching the simulation results very well. One potential application for this tunable filter is a front-end module mounted on the biomimetic robot driven by its mechanic movements. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a hybrid communication architecture that combines millimeter-wave (MMW) in the radio frequency (RF) domain and free-space-optics (FSO) technologies using adaptive combining and hybrid automatic repeat request (HARQ) techniques. At the receiving end, we employed joint signal processing with an adaptive diversity combining technique (ADCT) based on a maximum ratio combining (MRC) algorithm. We derived closed-form expressions for the outage probability and throughput of the hybrid RF and FSO (RF/FSO) system, considering various characteristics of atmospheric turbulence in the FSO link. Experimental testing with 10-Gbaud quadrature phase shift keying (QPSK) data was conducted under different simulated atmospheric turbulence intensities, FSO and MMW speed-ratios, and forward error correction (FEC) overheads. Additionally, we validated improvements in terms of bit error ratio (BER), outage probability, and throughput performance. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the secrecy performance of a dual-hop hybrid radio frequency–visible light communication (RF–VLC) system in which we consider a single source antenna (S) transmitting data signals via RF channel through decode and forward (DF) relay (R) toward an authorized receiving antenna (D) at the destination via VLC channel. In this system, we assume that the eavesdropper (E) attempts to eavesdrop the RF channel (S,R) during transmission of the signal. The relay decodes the incoming RF signal into corresponding optical signal and retransmits toward destination via VLC channel (R,D). The RF and VLC channels of the hybrid system are modelled using generalized-K fading distribution and generalized Lambertian radiant intensity distribution respectively. Also the receiver is assumed to be mobile and its mobility is defined by random waypoint (RWP) model. The channels statistics are used to derive the exact analytical expressions for average secrecy capacity and intercept probability in terms of Meijer's G-function. The derived closed form analytical expressions are the efficient tool to illustrate the impact of variation in different channel parameters on the secrecy performance, namely, shadowing parameters of RF channel, field of view (FOV), semiangle, and the order of Lambertian emission of the VLC channel. Further, numerical analysis is carried out to support the mathematical analysis of the RF–VLC hybrid system. [ABSTRACT FROM AUTHOR]

In this paper, the integration of the radio over fiber technology into a passive optical network (RoF-PON) is proposed to simultaneously distribute wired and two wireless standards each one transports 2 × 2 multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) signals. This simultaneous transmission is operated based on a single centralized optical wavelength and enabled by a polarization division multiplexing technique. The proposed RoF-PON system offers high spectral efficiency and is designed for unlicensed industrial, scientific, and medical bands at 2.4 and 5.8 GHz. The system performance is assessed by measuring the bit error rates (BERs) according to different access distances up to 30 km. After determining the optimum extinction ratio (ER) to modulate the baseband wired signal that allows jointly optical modulation of wireless signals using the same optical wavelength; all the 2 × 2 quadrature amplitude modulation (QAM) MIMO-OFDM wireless signals with a wired signal are successfully delivered without using forward error correction limit. Additionally, the system reliability has been confirmed by adopting other modulations schemes such as 8 and 16 phase-shift keying (PSK) that maintained good constellation diagrams performances. Whereas, the wired signal is analyzed according to its BER and quality Q-factor including high-quality eye diagram patterns. Also, the results revealed that the MIMO-OFDM signals mapped by 16 QAM scheme are given a better performance than PSK schemes when they are accompanied with high data rate baseband wired signal via a PON distance of 30 km. [ABSTRACT FROM AUTHOR]

Ten Gigabit-capable ethernet passive optical network (GEPON) can quickly improve network bandwidth, meet multilevel business needs, and quickly improve the comprehensive competitiveness of the network. It is well known that the 10G EPON access network technology is used to carry IPTV services, VoIP services and high-speed Internet access, known as "triple play", and IPTV services have been particularly popular in recent years. As the demand for IPTV service increases exponentially, a large amount of data will be generated, occupying a large access bandwidth and causing an impact on other services. Therefore, reasonable scheduling of IPTV service queue is an urgent problem to be solved under multiservice environment at present. Therefore, the design of PON bearing IPTV robustness algorithm to meet user experience is the focus of this paper. This paper proposes a Forward Error Correction with Weight Round Robin algorithm (FWRR), which adopts RS error correction code and Weighted Round Robin algorithm based on IP layer. When IPTV packet is lost at optical line terminal (OLT) end, downlink optical network unit (ONU) can recover the lost data through received packets. This mechanism can effectively solve the problem of packet loss caused by the blocking of OLT end, and realize the scheme of PON carrying IPTV multicast service. Simulations results in OPNET show that compared with weighted round robin (WRR) algorithm and round robin (RR) algorithm, FWRR mechanism can reduce packet loss, delay and jitter, in addition, improve the robustness of IPTV service in GEPON. [ABSTRACT FROM AUTHOR]

LoRa technology is being integrated into industrial applications as part of Industry 4.0 owing to its longer range and low power consumption. However, noise, interference, and the fading effect all have a negative impact on LoRa performance in an industrial environment, necessitating solutions to ensure reliable communication. This paper evaluates and compares LoRa's performance in terms of packet error rate (PER) with and without forward error correction (FEC) in an industrial environment. The impact of integrating an infinite impulse response (IIR) or finite impulse response (FIR) filter into the LoRa architecture is also evaluated. Simulations are carried out in MATLAB at 868 MHz with a bandwidth of 125 kHz and two spreading factors of 7 and 12. Many-to-one and one-to-many communication modes are considered, as are line of sight (LOS) and non-line of Sight (NLOS) conditions. Simulation results show that, compared to an environment with additive white Gaussian noise (AWGN), LoRa technology suffers a significant degradation of its PER performance in industrial environments. Nevertheless, the use of forward error correction (FEC) contributes positively to offsetting this decline. Depending on the configuration and architecture examined, the gain in signal-to-noise ratio (SNR) using a 4/8 coding ratio ranges from 7 dB to 11 dB. Integrating IIR or FIR filters also boosts performance, with additional SNR gains ranging from 2 dB to 6 dB, depending on the simulation parameters. [ABSTRACT FROM AUTHOR]

This paper introduces a technique to mitigate the Rayleigh backscattered (RB) noise generated in optical access links. Based on digital signal processing (DSP), the proposed technique reduces RB noise by utilizing the Lorentzian distribution function as a weighting function and leveraging the property that the derivative of an analog waveform is significantly greater than that of a digital waveform. The experimental results confirm that the proposed technique yields an input signal-to-noise ratio (SNR) gain of 4 dB. An observed reduction of 4-dB in power penalty is achieved based on the 1st generation forward error correction (GFEC) bit error rate (BER) threshold when utilizing the proposed technique. Thus, based on the significant experimental results, it is confirmed that the proposed technique is highly effective in reducing RB noise. [ABSTRACT FROM AUTHOR]

In this paper, the downlink of the multicast based spatial modulation systems is investigated. Specifically, physical layer multicasting is introduced to increase the number of access users and to improve the communication rate of the spatial modulation system in which only single radio frequency chain is activated in each transmission. To minimize the bit error rate (BER) of the multicast based spatial modulation system, a joint optimizing algorithm of antenna selection and multicast precoding is proposed. Firstly, the joint optimization is transformed into a mixed-integer non-linear program based on single-stage reformulation. Then, a novel iterative algorithm based on the idea of branch and bound is proposed to obtain the quasi-optimal solution. Furthermore, in order to balance the performance and time complexity, a low-complexity deflation algorithm based on the successive convex approximation is proposed which can obtain a sub-optimal solution. Finally, numerical results are showed that the convergence of our proposed iterative algorithm is between 10 and 15 iterations and the signal-to-noise-ratio (SNR) of the iterative algorithm is 1-2dB lower than the exhaustive search based algorithm under the same BER accuracy conditions. [ABSTRACT FROM AUTHOR]

The article focuses on the potential of DNA as a versatile code beyond life, envisioning its role in broader human society and civilization by capturing and processing digital information or driving molecular circuits and machines. Topics include the promising attributes of DNA for digital data storage, recent advances in DNA sequencing and synthesis technologies, and the exploration of DNA-based biocomputers with unique functionalities.

The emergence of new applications is driving a dramatic growth in the capacity of data center interconnects. Intensity modulation and direct detection (IM/DD) has the characteristics of low cost, low power consumption and a small footprint. Industry and academia have conducted much research on IM/DD systems as a cost-effective solution. However, optical/electronic bandwidth and fiber dispersion are the restricting factors for the improvement of transmission capacity. Pattern-dependent distortion is an important aspect that affects system performance. In this paper, we propose a look-up table (LUT)-based direct-detection-faster-than-Nyquist (DDFTN) algorithm to compensate for pattern-dependent distortion. The performances of feedforward-equalization (FFE) only, the original DDFTN, least-squares (LS)-based DDFTN, and LUT-based DDFTN algorithms in IM/DD-based 112/140 Gbit/s four-level pulse-amplitude modulation (PAM-4) signal transmission were evaluated. The experimental results indicate that LUT-based DDFTN performs better with low computational complexity. [ABSTRACT FROM AUTHOR]

A limitation of present elastic metasurfaces remains in their modest flexibility to meet convertible functions on demand. Here, a feasible single-layered lossless metasurface is theoretically proposed and experimentally demonstrated for adjusting the asymmetric transmission of flexural waves. The easily reconstructed unit is derived from multiple pillared resonators; then, the number of units per period can be changed depending on the desired integer parity. In addition, the asymmetric transmission is physically realized by the uneven diffraction of the ±1st orders in opposite fields of the designed metasurface. Requiring neither active modules nor passively multilayer or loss-induced strategies, our design using only a layer of lossless metasurface allows the elastic-wave behavior to switch between efficient symmetric and asymmetric transmissions. Furthermore, a high contrast ratio of transmitted energy is verified in experiments and simulations within a wide-angle range. The present work is connected with the pragmatic applications of metasurfaces in timely directional vibration control and compactly elastodynamic rectifications. [ABSTRACT FROM AUTHOR]

Combining integrated photonics and radiofrequency (RF) signals in the optical domain can help overcome the limitations of traditional RF systems. However, it is challenging to achieve environmentally insensitive filtering in wireless communications using integration schemes. In this report, the performance of robust RF filters based on a single silicon in-phase/quadrature modulator with significantly improved temperature and optical carrier wavelength sensitivities, which were suppressed by more than three orders of magnitude compared with those of silicon resonators, was experimentally evaluated. Upconversion and the processing of signals were simultaneously realized on the modulator by setting the relative phases of the arms and the bias voltages. Moreover, the filters can be reconfigured as low-pass, high-pass, band-pass, or band-stop filters. From 25 to 75 °C, the center frequency variation was within 0.2 GHz. From 1500 to 1600 nm, the center frequency variation was within 2 GHz. The proposed scheme allows for filtering and reconfiguration without the use of optical processing modules such as resonators or delay lines, thus providing a novel approach to signal processing and a new robust filter for scenarios with dynamic environments. [ABSTRACT FROM AUTHOR]

Compared to single ticket purchase behavior, the impact of ticket cancellation behavior on revenue is full of complexity. Due to the cancelled tickets will be resold with uncertain demand, ticket cancellation behaviors and ticket purchase behaviors are intertwined and influenced, composed of a dynamic and complex system in the presale period. How to charge for ticket cancellation behavior in the name of refund service fee to reduce losses as much as possible is an urgent problem for high-speed railway enterprises. However, there has been little research on this issue. Therefore, a pricing optimization approach for refund service fee based on negative binomial distribution was proposed in this article. Firstly, we proved that the probability of passengers arriving based on the accumulated ticket sales obeyed the negative binomial distribution, which was used to fit the uncertainty demand of passengers. Then, we categorized the passengers to build an optimization model with the objective of maximizing compensation for losses caused by ticket cancellation. A case study was implemented to show that the proportion of refund service fee to ticket price is generally higher than 50%. The refund service fee remains monotonously nondecreasing as the departure date approaches. It also indicated that the current charging standard for refund service fees was too low to offset the losses. In addition, passenger preferences and passenger flow have significant impacts on the dynamic pricing strategy for refund service fees. [ABSTRACT FROM AUTHOR]

In the paper, a dual-bidirectional ring-type wavelength-division-multiplexing (WDM) access network with downlink and uplink signal access simultaneously using a single fiber backbone in clockwise and counterclockwise directions, respectively. The proposed network architecture is simple and easy to implement via the designed remote node (RN) and optical line termination (OLT) modules, but it also can double the downlink traffic using the original WDM downlink wavelengths. The presented ring-type WDM network can also avoid the Rayleigh backscattering (RB) beat noise when the same wavelengths are applied as downlink and uplink channels concurrently. In the measurement, 50 km long-reach and 15 km short-reach fiber transmission lengths are achieved for the symmetrical 10 and 28 Gbit/s on-off keying (OOK) data access, respectively. In addition, based on the obtained power budgets of eight downlink WDM signals and network design at the forward error correction (FEC) threshold, 16 optical network units (ONUs) can be supported simultaneously. [ABSTRACT FROM AUTHOR]

Any communication scheme's principal goal is providing error-free data transmission. By increasing the rate at which data could be transmitted through a channel and maintaining a given error rate, this coding is advantageous. The message bits to be transmitted will gradually receive more bits thanks to the convolution (channel) encoder. At the receiver end of the channel, a Viterbi decoder is utilized in order to extract original message sequence from the received data. Widely utilized error correction approaches in communication systems for the enhancement of bit error rate (BER) performance are Viterbi decoding and convolutional encoding. The Viterbi decoder and convolution encoder rate for constraints with lengths of 2 and 6 and bit rates of 1/2 and 1/3 are shown in this study in the presence of (1/f) noise. The performance regarding the convolutional encoding/hard decision Viterbi decoding forward error correction (FEC) method affects the simulation outcomes. The findings demonstrate that the BER as function of signal to noise ratio (SNR) acquired for uncoded binary phase shift keying (BPSK) with the existence of additive white Gaussian noise (AWGN) is inferior to that acquired with the use of a hard decision Viterbi decoder. [ABSTRACT FROM AUTHOR]

The increasing demand for transmission capacity in fiber-optic communications makes multimode fibers (MMFs) attractive by enabling simultaneous multi-channel data transmission. However, inherent mode crosstalk among transmission channels limits its applicability. In this Letter, we propose to overcome this problem via wavefront shaping. By actively modulating the incident light with a special wavefront, not only the transmitted power for a specific channel can be enhanced but also crosstalk among different transmission channels can be mitigated. As a proof of concept, we experimentally demonstrated wavefront shaping assisted dual-channel optical communications through a single MMF. 10 Gbaud four-level pulse amplitude modulation signals were sent through both channels simultaneously, enabling a total bit rate of 40 Gbps. Both channels were analyzed with bit error rates below the hard-decision forward error correction limit, confirming the validity of the proposed scheme. [ABSTRACT FROM AUTHOR]

Since there are differences between students' understanding level, it is easy to produce wrong actions during the process of sports teaching. In order to improve the video detection effect, the video fidelity and compression rate, a remote video detection algorithm for sports wrong actions under wireless network is proposed. By extracting key frames in video clips, a real-time video transmission model is established based on wireless network, which transmits key frame extraction results real time with the support of real-time transmission protocol and forward error correction mechanism. The deterministic constrained nonlinear optimization method is used to estimate joint and overall motion parameters. Based on each parameter, the aggregated channel feature method is used to identify the target in the video sequence, and the support vector machine is used as a classifier of sports actions to recognize wrong actions. Then, the multi-scale space of moving images is constructed, the multi-layer box filter is used to simulate Gaussian convolution, and the simulation results are corresponded to the target areas in the remote video of sports wrong actions, thereby realizing the remote video detection of sports wrong actions. The experimental results show that the fidelity rate of the proposed algorithm is always above 90.3%, the compression rate is more than 80%, and only one key point is omitted. This proves that the video fidelity rate and compression rate of this method are high, and the detected key points are the same as the actual key points, which verifies the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The data acquisition system (DAQ) was designed for data taking from the TPC/MPD detector. The detector contains 95232 registration channels, includes 1488 Front-End Cards (FEC) and other modules grouped into 24 DAQ subsystems. Each FEC has an individual full-duplex few-gigabit communication channel with Readout and Control Unit (RCU). The RCU manages each FEC within the group, collects the data and then transmits them via a high-speed optical channel. Optical lines from each group of four RCUs are connected to the Local Data Concentrator (LDC) computer via a Data Concentrator Unit (DCU) module installed. Each of the six DCUs controls four RCUs, receives data from them and stores them into the LDC computer memory via the PCIe interface. The DAQ system is operating with a raw TPC event of the size up to 37 MB containing information up to 2000 tracks at the central collision and the event trigger rate of up to 7 kHz in zero suppression mode. The article presents the overall structure of the system and the realized functionality of its main components. Section 1 describes the arrangement of DAQ subsystems and modules inside MPD. Section 2 gives the function, structure and connections of DAQ subsystems. Section 3 describes in detail one of the 24 DAQ subsystems. Section 4 presents the scheme of the local storage of TPC data and communication with MPD DAQ. In Section 5, the system throughput is estimated. Section 6 summarizes the main performance indicators and key technologies used in the construction of the system. [ABSTRACT FROM AUTHOR]

Circularly polarized light interacts preferentially with the biomolecules to generate spectral fingerprints reflecting their primary and secondary structure in the ultraviolet region of the electromagnetic spectrum. The spectral features can be transferred to the visible and near‐infrared regions by coupling the biomolecules with plasmonic assemblies made of noble metals. Nanoscale gold tetrahelices were used to detect the presence of chiral objects that are 40 times smaller in size by using plane‐polarized light of 550 nm wavelength. The emergence of chiral hotspots in the gaps between 80 nm long tetrahelices differentiate between weakly scattering S‐ vs R‐molecules with optical constants similar to that of organic solvents. Simulations map the spatial distribution of the scattered field to reveal enantiomeric discrimination with selectivity up to 0.54. [ABSTRACT FROM AUTHOR]

Herein, elastic, optical, and thermoelectric properties of zinc chalcogenides with 2D square lattice and hexagonal phases [s‐ and h‐ZnX (X = GrVI)] are reported. The s‐ZnX and h‐ZnX structures are achieved to be dynamically stable, according to the phonon dispersion studies. All s‐ and h‐ZnX compounds are found to be semiconductor, with direct and indirect bandgaps ranging from 0.81 to 2.77 eV under PBE and 1.70 to 4.15 eV by HSE06 calculations. The effective mass, mobility, and relaxation time of electron and hole carriers in the band structures of s‐ and h‐ZnX are investigated to gain a better insight of these materials. In addition to the phonon dispersion analysis, their mechanical stability in terms of elastic properties is evaluated, and the resulting elastic parameters validate their mechanical stability. The optical properties of s‐ and h‐ZnX are inspected in the occurrence of field polarizations across parallel and perpendicular directions. At room temperature, s‐ZnTe compound has an optimum figure of merit (ZT) value, indicating it as the superlative thermoelectric material in the entire series. These compounds may also be explored in ultraviolet lasers, solar cells, electronic image displays, high‐density optical memory, photodetectors, and solid‐state laser devices. [ABSTRACT FROM AUTHOR]

We present a novel approach to generate Bessel–Gauss modes of arbitrary integer order and well-defined optical angular momentum in a gradient index medium of transverse parabolic profile. The propagation and coherence properties, as well as the quality factor, are studied using algebraic techniques that are widely used in quantum mechanics. It is found that imposing the well-defined optical angular momentum condition, the Lie group S U (1 , 1) comes to light as a characteristic symmetry of the Bessel–Gauss beams. [ABSTRACT FROM AUTHOR]