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Abstract\nHighlightsStreptophyte “glacier algae” thrive on the melting surfaces of glaciers and ice sheets, producing conspicuous blooms during summer ablation seasons. To-date, the direct application of pulse amplitude modulation (PAM) fluorometry to measure the in situ responses of glacier algae to their environment has been prevented by the high ambient light environment, causing over-saturation of fibre- and imaging-PAM systems. The use of cuvette-based systems has also relied upon bulk sampling and prolonged melting of surface ice, reducing or removing the short-term light history of glacier algae prior to measurements. Here, we outline a simple method that allows the rapid liberation of glacier algal cells into suspension for the measurement of their photophysiology using the sensitive Walz Water-PAM cuvette system, moving from ice to measurement with only a 5-min dark-adaptation period. We illustrate the effectiveness of our method by performing rapid light curves (RLCs) on glacier algae from naturally shaded versus fully exposed ice surfaces on the Greenland Ice Sheet and contrast this with typical 24 h melt/dark-adapt approaches employed to-date. Results highlight that fine-scale heterogeneity is apparent in glacier algal in situ photophysiology relative to dominant environmental forcings, with our method effective at constraining the near actual photochemistry of glacier algae as opposed to their more optimal photochemistry measured previously. Easy to implement on the ice, our method should allow future mapping of the fine-scale patterning in glacier algal responses to surface ice stressors. First method capable of measuring glacier algal actual photophysiology.Application and comparison of the method on Greenland Ice Sheet communities.First evidence of fine-scale heterogeneity in glacier algal photophysiology.First method capable of measuring glacier algal actual photophysiology.Application and comparison of the method on Greenland Ice Sheet communities.First evidence of fine-scale heterogeneity in glacier algal photophysiology. [ABSTRACT FROM AUTHOR]

This study proposes a high-frequency Pulse Amplitude-Modulation Temporal-Interference (PAM-TI) current stimulation device, which utilizes two sets of Amplitude-modulated transcranial alternating current stimulation (AM-tACS): one AM frequency at f0 (where f0 = 2 kHz) (source 1) and the other AM frequency at f1 = f0 + △ f (where f1 = 2.01 kHz) (source 2), to generate a △ f (where △ f = 10 Hz) envelope modulated at a fc (where fc = 100 kHz) high carrier frequency. The high carrier frequency reduces body impedance and conserves more stimulation power, allowing it to penetrate the skin and reach the subcutaneous region. The proposed PAM-TI technique elevates the two current sources to a 100 kHz carrier frequency. Instead of the challenges associated with generating high-frequency stimulation currents using an MCU and DAC, the proposed PAM-TI stimulation device achieves this by simply utilizing a pair of complementary pulse-width modulations (PWMs). The push–pull technique is employed to balance the charging currents between the anode and cathode, synchronizing the current timing of Source 1 and Source 2 under the fc modulation condition. To minimize signal attenuation, the PAM circuit is integrated directly into the electrode, ensuring the high-frequency signal is generated close to the body and preventing degradation from long wires. Additionally, a dry pin-type spring-loaded electrode is used to reduce interference caused by hair when placed on the head. The device's validity and current directionality were verified using a scalp tissue-mimicking phantom composed of agar and saline. [ABSTRACT FROM AUTHOR]

During a 2019 Chilean Antarctic Scientific Expedition (ECA 55) studying crustose coralline algae (CCA) diversity on the Antarctic Peninsula, bleaching of these algae was observed for the first time in this region. Here, we present initial findings on the physiological state of bleached and normally pigmented CCA (Clathromorphum sp.) assessed using chlorophyll- a fluorescence induction pulse amplitude modulation. The study site experienced high light exposure and salinity in the water column. Our analyses found that bleached CCA have relatively healthy photophysiology responses but lower photosynthetic efficiency, which could be associated with the low salinities recorded in the study area. However, seasonal monitoring and mesocosm experiments across the southern polar latitudes are urgently required to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

Germanium/silicon (Ge/Si) avalanche photodiode (APD) has emerged as a highly desirable component for optical communication, sensing, and computing, attributed to its inherent gain. Conventional schemes typically suffer from limited bandwidth and significant excess noise due to the high gain, restricting the high‐sensitivity detection in burgeoning high‐speed applications. Here, a Ge/Si APD is developed with an ultra‐large bandwidth at an optimal gain. This breakthrough is achieved by implementing an extremely narrow multiplication layer to enhance the space charge effect, overcoming the intrinsic bandwidth limitation in conventional APDs while elaborately harnessing the gain to a moderate value to ensure the optimal sensitivity. The device possesses a bandwidth of 67 GHz at an optimal gain of 6.6 and enables data reception of 240 Gb s−1 four‐level pulse amplitude modulation signal—the largest bandwidth and highest single‐channel bitrate among all reported APDs. The presented APD suggests promising applications for high‐speed and high‐sensitivity data communication owing to its competitive performance, cost‐effectiveness, and high‐yield production. [ABSTRACT FROM AUTHOR]

In this work, we implemented a short-reach real-time optical communication system using MLP for pre-distortion. Lookup table (LUT) algorithms are commonly employed for pre-distortion in intensity modulation and direct detection (IM/DD) systems. However, storage limitations typically restrict the LUT pattern length to 9, limiting its effectiveness in compensating for nonlinear effects. A multilayer perceptron (MLP) can overcome this limitation by predicting errors and generating pre-distorted signals, thus replacing the extensive storage requirements of LUTs with minimal computational resources. The MLP-based digital pre-distortion (MLP-DPD) technique enables the creation of long-pattern LUTs for improved nonlinear compensation. In this work, an MLP-DPD scheme was implemented on a field-programmable gate array (FPGA). The FPGA was used to generate a 14.7456 GBaud pre-distorted pulse amplitude modulation 4-level (PAM4) signal. This signal was then transmitted over 20 km of standard single-mode fiber (SSMF). At the receiver, the parallel constant modulus algorithm (PCMA) was applied for signal processing. The bit error rate (BER) achieved met the 2.4 × 10−2 threshold for soft-decision forward error correction (SD-FEC), enabling a net transmission bit rate of 24.576 Gbit/s. This approach demonstrates the feasibility of using MLP-DPD for effective nonlinear compensation in high-speed optical communication systems with limited resources. [ABSTRACT FROM AUTHOR]

Maintaining constant exposure concentrations during ecotoxicological studies while testing rapidly degradable substances is a challenge. To achieve stable concentrations during exposure, flow‐through systems are used. To assess the impact of substances on higher aquatic plants, the 14‐day macrophyte water–sediment Myriophyllum spicatum growth inhibition test (Organisation for Economic Co‐operation and Development [OECD, 2014a] test guideline 239) only includes a static or a semistatic test design. The main aim of our study was to investigate the applicability of a flow‐through system for M. spicatum. The standard OECD test design was miniaturized, and a flow‐through system with spill‐over was developed to achieve stable exposure concentrations of a rapidly degrading substance. The main endpoints were total shoot length and fresh and dry weight. Photosynthetic activity was used as an endpoint for the identification of early effects using the noninvasive Image‐Producing Pulse Amplitude Modulation (IMAGING‐PAM) procedure. Atorvastatin (AV; fast degrading) and bentazone (BT; photosynthesis inhibitor) were used as model substances to observe differences of the effect concentration depending on the test design. At higher exposure levels of AV, stronger necrosis combined with lower effect concentrations was observed in the flow‐through test compared with the semistatic test, indicating the applicability of the flow‐through test for evaluating degradable substances. The test with BT demonstrated a concentration‐dependent decrease in the photosynthetic yield (Y(II)) from day 3 onward even before macroscopically visible changes occurred. Our results show that the flow‐through system in the macrophyte growth inhibition test (OECD test guideline 239; 2014a) is a suitable alternative when one is testing rapidly degradable substances such as AV. In addition, we showed that photosynthetic yield can serve as a supplementary endpoint, when one is testing substances with photosynthesis inhibition as a mode of action. Environ Toxicol Chem 2024;43:2589–2600. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

We present a comprehensive performance analysis of injection-locked directly modulated laser (DML) for optical communication systems, focusing on both non-return-to-zero (NRZ) and 4-level pulse amplitude modulation (PAM4) signal transmission. We demonstrate real-time PAM4 40 Gbit/s transmission over 10 km of single-mode fiber enabled by optical injection locking without pre-emphasis or post-equalization, achieving a bit error rate (BER) below 10 - 6 , and doubling capacity compared to unlocked transmission with the same laser. Our study investigates the dependence of system performance on the injected power and frequency offset of the master laser. Results indicate that lower injection powers while maintaining a stable locking regime, yield better performance in terms of extinction ratio and BER. Optimized parameters lead to enhanced transmission performance, providing valuable insights into the design and optimization of injection-locked DML systems for optical communication applications employing direct modulation. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate an artificial intelligence (AI)-enabled efficient modulation classification technique for underwater optical wireless communication (UOWC) systems. Specifically, time-domain waveform histograms are adopted as classification features, where three modulation formats including direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM), asymmetrically clipped optical OFDM (ACO-OFDM) and pulse amplitude modulation (PAM) are considered. Moreover, AI algorithms such as decision trees (DT), k-nearest neighbors (k-NN), support vector machines (SVM) and convolutional neural networks (CNN) are utilized to realize efficient modulation classification based on the obtained waveform histogram features. Experimental results demonstrate that all the four algorithms can achieve accuracy surpassing 95% when the received signal-to-noise ratio (SNR) exceeds 6.3 dB. Furthermore, increasing the number of symbols in histograms enhances classification accuracy, whereas altering the number of histogram bins has minimal impact on classification accuracy. [ABSTRACT FROM AUTHOR]

In view of the problem of accurate estimation of symbol rate in non - collaborative communication, a high - precision symbol rate estimation algorithm based on the improved phase difference correction method is proposed on the basis of the envelope - square method. The algorithm compares the positions of the peaks of the envelope squared spectra of two sequences with the minimum shift relationship, discards the sequences that are seriously disturbed by noise, and selects the two sequences with the same peak positions to accurately estimate the symbol rate of the signal by the phase - difference correction method. Compared with the envelope - leveling method, this algorithm breaks the limitation that the estimation accuracy of the symbol rate depends on the number of sampling points of the signal, and has a very high estimation accuracy. Simulation experiment results show that the proposed algorithm can achieve accurate estimation of MPSK (Multiple Phase Shift Keying), MPAM (Multiple Pulse Amplitude Modulation) and MQAM (Multiple Quadrature Amplitude Modulation) signal element rates at low signal - to - noise ratios, and the complexity of the proposed algorithm is lower than that of existing high - precision estimation algorithms, making it suitable for application in engineering practice. [ABSTRACT FROM AUTHOR]

High‐speed electro‐optic modulators are key components in modern communication networks and various applications that require chip‐scale modulation with large bandwidth, high modulation efficiency, and compact footprint. However, fundamental trade‐offs make it challenging to achieve these metrics simultaneously, and thus new methodologies must be explored. To this end, a Mach–Zehnder modulator harnessing slow‐light waveguides and capacitively loaded slow‐wave electrodes are presented on silicon‐nitride‐loaded lithium niobate on an insulator platform. The increased group index and reduced microwave loss significantly improve the modulation efficiency. With the 1‐mm‐length modulation section, a low half‐wave voltage length product Vπ·L of 0.21 V cm is obtained, which is one order of magnitude smaller than that of conventional thin film lithium niobate Mach–Zehnder modulators, and a modulation bandwidth of surpassing 110 GHz is achieved. The digital signal processor‐free non‐return‐to‐zero signal and eight‐level pulse amplitude modulation signal of up to 180 and 300 Gbps, respectively, are generated by the modulator, which provides ultra‐large bandwidth, ultra‐high efficiency, and a compact solution for next‐generation electro‐optic systems. [ABSTRACT FROM AUTHOR]

This paper presents a non-return-to-zero (NRZ)/4-level pulse amplitude modulation (PAM-4) dual-mode wireline transmitter with an eye-opening enhancement technique to improve horizontal eye-opening. With the eye-enhancement pulse generator and the auxiliary pull-up device in the tail-less current-mode driver, the worst-case horizontal eye-opening increased by 30% in the PAM-4 eye diagram. The power efficiency of the NRZ mode was also improved by completely turning off the LSB path in the differential data path, resulting in only a 31% power efficiency degradation, which is far lower than that of the prior dual-mode transmitters. Fabricated in 28 nm CMOS, the transmitter achieves power efficiency of 1.4 pJ/bit at 56 Gb/s in PAM-4 mode and 1.84 pJ/bit at 28 Gb/s in NRZ mode, respectively. [ABSTRACT FROM AUTHOR]

Chlorophyll fluorescence measurement is a quick and efficient tool for plant stress‐level detection. The use of Pulse amplitude modulation (PAM), allows the detection of the plant stress level under field conditions. Over the years, several parameters estimating different parts of the chlorophyll and photosystem response were developed to describe the plant stress level. Despite all fluorescence parameters being based on the same measurements, their relationship remains unclear, and their response to drought stress is significantly influenced by the incoming light intensity. In this study, we use six different annual plants from different families, both C3 and C4 photosynthesis types, to describe the plant response to drought through the fluorescence parameters response (NPQ, Y(NPQ), and qN). To describe the dynamic response to drought, we employed light‐response curves, adapting and fitting an equation for each curve to compare the drought response for each fluorescence parameter. The results demonstrated that the non‐photochemical quenching (NPQ) and the quantum yield of non‐photochemical quenching [Y(NPQ)] maximal values decrease when the PSII functionality (Fv/Fm) is lower than ~0.7. The basal fluorescence level (F0$$ {F}_0 $$ and Fs)$$ {F}_s\Big) $$ remained unaffected by the stress level and stayed stable across the various plants and stress levels. Our results indicate that the response of different stress parameters follows a distinct order under continuous drought. Consequently, monitoring just one parameter during long‐term stress assessments may result in biased analysis outcomes. Incorporating multiple chlorophyll fluorescence parameters offers a more accurate reflection of the plant's stress level. [ABSTRACT FROM AUTHOR]

With the advantages of high speed, small size, and easy integration, the silicon photonic resonant ring modulator has gradually become a critical device for emerging integrated optical platforms. Ring modulators are primarily used in optical communications, optical computing, artificial intelligence, and other fields. In this work, the proposed ring modulator can operate in both the O- and C-bands. The 3 dB electro-optical (EO) bandwidth of the ring modulator is 39 GHz and 34 GHz at −4 V in the O-band and C-band, respectively. The modulation efficiency of the device is 0.92 V·cm and 0.95 V·cm in the O-band and C-band, respectively. The eye diagram of an optical output signal from the device is tested using a 100 Gbit/s non-return-to-zero (NRZ) input signal with a 2.5 Vpp in both the O-band and C-band. The modulation speed can reach 140 Gb/s and 120 Gb/s in the O-band and C-band with four-level pulse amplitude modulation (PAM-4) formats at a voltage swing of 2.5 Vpp, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally illustrate the effectiveness of neural networks (NNs) as non-linear equalisers for multilevel pulse amplitude modulation (PAM-M) transmission over an optical wireless communication (OWC) link. In our study, we compare the bit-error-rate (BER) performances of two decision feedback equalisers (DFEs)—a multilayer-perceptron-based DFE (MLPDFE), which is the NN equaliser, and a transversal DFE (TRDFE)—under two degrees of non-linear distortion using an eye-safe 850 nm single-mode vertical-cavity surface-emitting laser (SM-VCSEL). Our results consistently show that the MLPDFE delivers superior performance in comparison to the TRDFE, particularly in scenarios involving high non-linear distortion and PAM constellations with eight or more levels. At a forward error correction (FEC) threshold BER of 0.0038, we achieve bit rates of ~28 Gbps, ~29 Gbps, ~22.5 Gbps, and ~5 Gbps using PAM schemes with 2, 4, 8, and 16 levels, respectively, with the MLPDFE. Comparably, the TRDFE yields bit rates of ~28 Gbps and ~29 Gbps with PAM-2 and PAM-4, respectively. Higher PAM levels with the TRDFE result in BERs greater than 0.0038 for bit rates above 2 Gbps. These results highlight the effectiveness of the MLPDFE in optimising the performance of SM-VCSEL-based OWC systems across different modulation schemes and non-linear distortion levels. [ABSTRACT FROM AUTHOR]

Due to the nonlinear nature of continuous phase modulation (CPM), most existing unambiguous acquisition algorithms are ineffective in eliminating the ambiguity threat faced by semi‐integer CPM signals. To address this issue, this letter proposes an unambiguous acquisition algorithm based on sub‐correlation functions combination (SCFC). The main idea of this algorithm is to decompose the first pulse amplitude modulation waveform derived from the Laurent decomposition into sub‐signal waveforms that are appropriate for CPM signals. The final unambiguous function is obtained by combining the autocorrelation function of the received CPM signal with the sub‐correlation functions derived from the sub‐signal waveforms and the received CPM signal. Simulation results demonstrate that the SCFC algorithm can eliminate the ambiguity threat of semi‐integer CPM signals with relatively minor detection loss. Moreover, the proposed algorithm successfully retains a narrow main peak and exhibits superior multipath resistance. [ABSTRACT FROM AUTHOR]

This paper introduces a 400 Gbps free space optics (FSO) system to meet the expected surge in the demand for data traffic. The proposed system is based on using 4-level pulse amplitude modulation (PAM-4) signals in addition to polarization division multiplexing and orbital angular momentum (OAM) multiplexing schemes. To reduce spectrum usage, only a single wavelength of 1550 nm is used. A 400 Gbps is transmitted over two polarization states and eight OAM beams. The signal on each polarization carries the data of four different OAM beams ( LG 0 0 , LG 15 0 , LG 40 0 , and LG 80 0 ). The performance of the proposed model is examined under the influence of light haze, medium haze, heavy haze, low fog, medium fog, heavy fog, wet Snowfall, dry snowfall, light dust storms, medium dust storms, and heavy dust storms. The maximum transmission range and the Bit Error Rate (BER) are used for evaluating the system performance. The simulation results reported the longest FSO link with ranges from 800 to 1475 m under haze conditions. A slight decrease in these ranges is achieved under fog conditions (ranges from 450 to 859 m). The FSO highest attenuation is experienced for HDS case, which results in the shortest range of 73 m. These ranges are calculated at BER Forward Error Correction limit of 3.8 × 10–3. Subsequently, the proposed system can be used for the next 6G applications due to its simplicity in design and high transmission capacity. [ABSTRACT FROM AUTHOR]

In order to meet the increasing requirements of speed and distance, an advanced digital signal processing (DSP) algorithm is preferred without changing the system structure in intensity modulation and the direct detection (IM/DD) system. As the transmission distance increases, the power fading induced by dispersion must be mitigated. In addition, linear and nonlinear inter symbol interference (ISI) introduced by bandwidth limitation and device imperfections becomes an obstacle to achieving higher capacity. The Gerchberg–Saxton (GS) algorithm was recently used to compensate for dispersion. In this paper, GS-based pre- and post-compensation schemes in the IM/DD system with nonlinearity were investigated. We investigated and compared the performance of the GS-based pre- and post-compensation algorithm in a 28 GB aud four-level pulse amplitude modulation (PAM-4) transmission over 40 km standard single-mode fiber (SSMF). The bit error rate (BER) achieved a threshold of 3.8 × 10−3 using look-up-table (LUT), FFE, and the GS-based pre-compensation algorithm without iterations. Turning to the GS-based post-compensation scheme, 80 iterations are needed. However, the demand for FFE is reduced. The algorithm selection depends on the tolerance of the transmitter or receiver complexity in specific scenarios. The joint LUT and GS-based pre-compensation algorithm may be a preferable approach in scenarios where a low-complexity receiver is desired. [ABSTRACT FROM AUTHOR]

Photonic integrated circuits (PIC) devices are impacted by fabrication tolerances and therefore, prior knowledge of such variations could improve the PIC fabrication process and overall yield. This paper presents a method for predicting the fabrication impacts on a telecommunication optical digital to analog converter (oDAC)-based pulse amplitude modulator level four (PAM-4) transmitter as a case study where the certainty of this passive device is subjected to random variation. Our findings allow us to estimate the production yield in a fabrication scenario using the symbol error rate (SER) benchmark and this contributes to the study of the viability of oDAC PAM-4 transmitters to replace conventional electrical digital to analog converter (eDAC) PAM-4 transmitters. [ABSTRACT FROM AUTHOR]

The changes in the cell physiology (growth rate, cell size, and cell DNA content), photosynthetic efficiency, toxicity, and sexuality under variable light and nutrient (phosphates) conditions were evaluated in cultures of the dinoflagellate Alexandrium minutum obtained from a red tide in the Ría de Vigo (NW Spain). The cells were grown at low (40 and 150 µE m−2 s−1), moderate (400 µE m−2 s−1), and high (800 µE m−2 s−1) light intensities in a medium with phosphate (P+) and without (P−). Cultures were acclimated to the irradiance conditions for one week, and the experiment was run for ~1 month. The cell size and DNA content were monitored via flow cytometry. Two different clonal strains were employed as a monoculture (in a P− or P+ medium) or, to foster sexuality and resting cyst formation, as a mixed culture (only in a P− medium). A. minutum growth was favored by increasing light intensities until 400 µE m−2 s−1. The DNA content analyses indicated the accumulation of S-phase cells at the highest light intensities (400 and 800 µE m−2 s−1) and therefore the negative effects on cell cycle progression. Only when the cells were grown in a P− medium did higher light intensities trigger dose-dependent, significantly higher toxicities in all the A. minutum cultures. This result suggests that the toxicity level is responsive to the combined effects of (high) light and (low) P stress. The cell size was not significantly affected by the light intensity or P conditions. The optimal light intensity for resting cyst formation was 150 µE m−2 s−1, with higher irradiances reducing the total encystment yield. Encystment was not observed at the lowest light intensity tested, indicative of the key role of low-level irradiance in gamete and/or zygote formation, in contrast to the stressor effect of excessive irradiance on planozygote formation and/or encystment. [ABSTRACT FROM AUTHOR]

Self-generation of microwave nonlinear waveforms in the magnonic-optoelectronic oscillator (MOEO) was investigated. Nonlinear dynamics of the MOEO was due to both optical and magnonic paths of the oscillator circuit. Four-magnon parametric interactions in the magnonic path and cosine transfer function of the electro-optical modulator caused double nonlinearity of the MOEO. Gain coefficient was used as a control parameter. We found that during a route from regular to chaotic dynamics, the oscillator generates two unusual waveforms: symmetry-breaking soliton-like modes of Möbius type and periodic pulses with chaotic amplitude modulation. Nonlinear waveforms were characterized using a time series analysis. Peculiarities of the signals and their spectra in regular and chaotic regimes of self-generation are discussed. We expect that the multiple nonlinearity of the MOEO may be useful for investigation of various fundamental effects in complex time-delayed systems and for development of novel circuits for neuromorphic computing. [ABSTRACT FROM AUTHOR]

Mini‐LED and Micro‐LED have ultrahigh luminance and excellent color saturation to be used in MLED display based on COG (Chip on Class). In this paper, two pitch‐0.6 mm MLED displays with pulse hybrid modulation (PHM) and pulse amplitude modulation (PAM) driving Mode separately is proposed. And we discuss the influences of the intrinsic optical characteristics of Mini‐LED and Micro‐LED on the design of MLED display pixel circuit. In particular, surface brightness distributions of different gray scale are tested to theoretically analyze the pocking phenomenon in different ways. [ABSTRACT FROM AUTHOR]

In order to solve the problem of low gray level due to the few driving chips developed based on the photoelectric characteristics of electrowetting display, a driving method based on modulation is proposed to double the gray level of electrowetting display. In this method, the driving waveform based on pulse amplitude modulation and pulse width modulation hybrid modulation is designed, and the gray level-luminance curve of the electrowetting display is measured and analyzed. On this basis, the luminance nonlinear correction is carried out, and the improvement of 64 Gy levels to 127 Gy levels is realized by the principle of human visual persistence phenomenon. The experimental results show that the proposed driving scheme can break through the limitation of the driving chip and realize the multiplication of gray levels, in which 96% gray levels increase steadily with an average luminance difference of 0.07, and at the same time enhance the contrast and improve the display effect. [ABSTRACT FROM AUTHOR]

Light emitting diodes (LEDs) play an essential role in lighting, and green earth activities because of their high efficiency, longevity, and reduction of carbon dioxide emissions during illumination. However, the brightness level of LED light sources must be adjusted appropriately for the backlight source or illumination; therefore, pulse amplitude modulation (PWM) is a commonly used method of LED control. This article experimentally investigated human interaction with the visual comfort effect of the light obtained using different PWM frequencies on an object in a sensor-based intelligent lighting system. Critical light frequencies are vital for the eye to distinguish light stimuli according to time. Histograms of the object were created according to the light frequency, and the results are discussed. The eye's response to light frequencies changing over time is important for visual comfort, and examining light frequencies in the range of 25–250 Hz was sufficient to conclude the study. It has been experimentally shown that light frequencies around 160 Hz, and above this value provide visual comfort. [ABSTRACT FROM AUTHOR]

Underwater Passive Acoustic Monitoring (UPAM) has been used infrequently to register subsurface vocal behaviour in anurans. This study describes the underwater advertisement call of Telmatobius rubigo based on recordings made with UPAM technique. Telmatobius rubigo call is a low-frequency trill composed of 6 to 22 pulses with amplitude modulation. The spectral and temporal characters showed differences from other Telmatobius species. The UPAM, combined with automated call identification software, showed effectiveness in monitoring the calling behaviour of this aquatic Andean frog in their natural environment. UPAM and soundscape/riverscape analysis should be incorporated as a non-invasive tool for monitoring threatened aquatic species. [ABSTRACT FROM AUTHOR]

A fully differential lumped linear driver for Mach–Zehnder modulator has been presented and assessed in 130‐nm SiGe BiCMOS technology. Multitopology peaking techniques, especially T‐coil peaking method, have been employed to flatten the frequency response and increase the bandwidth. Degeneration resistors have been used to enhance circuit linearity. Simultaneously, improvements have been made to the output stage of the conventional single emitter follower push–pull) circuit to enhance the output eye diagram quality at higher transmission rates. The fabricated driver achieved a differential gain of 16.2 dB with a bandwidth of over 50 GHz, corresponding to a fixed output swing of over 3.2 Vppd within the automatic gain control loop. Time domain measurements, limited in speed by the measurement setup, reported a data rate up to 56 Gb/s none return to zero and 40‐GBaud 4‐levels pulse amplitude modulation with a bit error rate less than 10−12. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a Mach–Zehnder Interferometer (MZI)-based optical neural network (ONN) to classify and regenerate a four-level pulse-amplitude modulation (PAM4) signal with high inter-symbol interference (ISI) generated experimentally by a silicon microing modulator (SiMRM). The proposed ONN has a multiple MZI configuration achieving a transmission matrix that resembles a fully connected (FC) layer in a neural network. The PAM4 signals at data rates from 160 Gbit/s to 240 Gbit/s (i.e., 80 GBaud to 120 GBaud) were experimentally generated by a SiMRM. As the SiMRM has a limited 3-dB modulation bandwidth of ~67 GHz, the generated PAM4 optical signal suffers from severe ISI. The results show that soft-decision (SD) forward-error-correction (FEC) requirement (i.e., bit error rate, BER < 2.4 × 10−2) can be achieved at 200 Gbit/s transmission, and the proposed ONN has nearly the same performance as an artificial neural network (ANN) implemented using traditional computer simulation. [ABSTRACT FROM AUTHOR]

Bi-directionally operated amplifiers enabling efficient utilization of transmission wavelengths are promising candidates in densely integrated photonic circuits for future cost-effective, power-efficient optical networks. Here, we demonstrate, for the first time, a broadband semiconductor optical amplifier (SOA) based on a novel chirped multilayered quantum dot (QD) structure, which is suitable for bi-directional amplification via the dual ground state (GS) emission spectrum. The fabricated QD SOA has achieved a maximum 3-dB gain bandwidth of 50 nm while retaining on-chip gain above 20 dB at both GS wavelengths. Under an optimum pumping current of 280 mA, the bi-directionally operated QD SOA has shown around 10 dB receiver sensitivity improvement in ultra-high-speed 100 Gbaud non-return-to-zero and 53.125 Gbaud four-level pulse amplitude modulation data transmission systems. [ABSTRACT FROM AUTHOR]

This paper explores, through the utilization of analytical models and simulations, the bit error rate (BER) of 400GBASE-LR8/ER8 in back-to-back configuration, considering various extinction ratio (ER) values and photodetector types. Simulation of transmission over fiber is carried out to measure chromatic dispersion (CD) penalty in each scenario. To increase the distance, we simulated a multi-span transmission with inline optical amplifiers (OAs). We mitigated the effects of CD-induced power fading by employing equalization such that the channel under test (CUT) at 1274 nm could reach $7\times 30$ km. The effects of fiber nonlinearity were also investigated for both single-channel and 3 wavelength division multiplexing (WDM) at various channel spacings. Moreover, the relationship between ER and peak-to-average-power ratio (PAPR) at different distances was investigated. An ER optimization for a highly accumulated CD multi-span fiber link with amplification was effective in improving the BER. Finally, we successfully transmitted a 26.56 GBaud 4-level pulse amplitude modulation (PAM-4) signal up to $8\times 30$ km with the optimal ER of 5 dB.

In optical communication systems, the Q-factor is an important performance metric to evaluate the performance of an optical link. In this paper, a deep learning-based eye diagram analyzer is proposed to estimate the Q-factor. CNN architectures such as LeNet, Wide ResNet, and Inception-v4 are used for ON-Off Keying (OOK) and Pulse Amplitude Modulation (PAM) formats’ eye diagrams. The performance of these architectures is evaluated in terms of accuracy, Mean Squared Error (MSE), and error tolerance. This work shows that Wide ResNet demonstrates better performance in both OOK and PAM4 transmission schemes, achieving MSE values of 0.00188 and 0.00036, respectively. Additionally, it attains a high R-squared (R2) value of 0.9998. This deep learning-based eye diagram analyzer may be a promising approach for analyzing and optimizing optical communication systems without extensive human intervention.

This paper presents an all-optical time-extended optical code division multiplexing (TE-OCDM) system using two different optical en/decoders (E/Ds). The proposed system configuration alleviates the rigorous requirement for transmitter specifications in TE-OCDM systems. We numerically evaluate the use of PAM-4 with TE-OCDM for the first time by optimizing chip period to reduce inter-symbol interference (ISI). We utilize an analytical model and simulations to investigate the bit error rate (BER) in back-to-back scenario as a function of extinction ratio (ER) and total power contrast ratio (PCR). The fiber simulation with inline amplifications shows that 8 TE-OCDM PAM-4 signals at 12.5 Gbaud using 1274 nm could reach up to $8\times 30$ km. The total bit rate is equivalent to 200 Gbps (8 TE-OCDM users $\times 12.5$ Gbaud $\times 2$ bits/symbol) per wavelength. Further analysis of the scalability of TE-OCDM over the entire O-band through the optical E/D spectral periodicity, suggests that the feasible total bit rate that can be achieved is approximately 3 Tbps.

This paper proposes a new modulation-driven pipelining approach for reducing the complexity of speculative decision feedback equalizers (DFEs). The scalable receiver architecture enables the detection and equalization of multiple pulse amplitude modulation (PAM) signaling schemes using same hardware. The receiver is architected into parallel slices of pipelined layers that achieve significant energy and area savings compared to conventional realizations. The fine modularity in two dimensions of the proposed receiver circuit facilitates the clock gating of unused components to ensure energy-proportional behavior. Simulink simulations were used to discuss the parallel and multi-layer operation of the proposed receiver in both detection and equalization modes. The results from the model also show no performance degradation from the new receiver architecture when configured for PAM8/6/4/3/2 operation. Transistor level design and physical layout of a 1-tap PAM4 DFE/3-tap PAM2 DFE were used to discuss design considerations and trade-offs. Pre-layout validation results indicate that seamless reconfigurability and complexity reduction can be achieved at comparable or better area and power to architectures that constrain the receiver intersymbol interference (ISI).

Four-level pulse amplitude modulation (PAM4) can transmit more information in the same symbol interval, effectively improving the information transmission rate and frequency band utilization of visible light communication (VLC). This paper proposes a method for encoding and decoding the PAM4 signal based on FPGA. The PAM4 signal is studied and analyzed under different channel noise models. The research results show that the bit error rate (BER) performance of the PAM4 signal is the best under the additive noise model. The influence of the multiplicative noise on the BER of the PAM4 signal is much greater than that of the additive noise. The BER performance of the PAM4 signal depends on the variance of the noise data. The greater the variance, the worse the BER performance. At the same time, an indoor VLC system based on PAM4 is designed. The simulation results verify that the system scheme is feasible and provides a way to further realize high-speed signal transmission. [ABSTRACT FROM AUTHOR]

This article discusses the importance of phenotyping photosynthesis for crop improvement and breeding programs. The authors highlight the challenges of studying photosynthesis in natural conditions and the need for higher throughput tools to overcome these barriers. They discuss the use of controlled-environment systems and remote sensing methods, such as solar-induced fluorescence and laser/light-induced fluorescence transient, for phenotyping photosynthesis. The authors also mention the use of hand-held MultispeQ PAM fluorometers as affordable tools for field phenotyping. The article concludes by emphasizing the potential of photosynthetic phenotyping for driving yield improvement in crop breeding programs. [Extracted from the article]

Described here is the development of an ultrasound matrix transducer prototype for high-frame-rate 3-D intra-cardiac echocardiography. The matrix array consists of 16 × 18 lead zirconate titanate elements with a pitch of 160 µm × 160 µm built on top of an application-specific integrated circuit that generates transmission signals and digitizes the received signals. To reduce the number of cables in the catheter to a feasible number, we implement subarray beamforming and digitization in receive and use a combination of time-division multiplexing and pulse amplitude modulation data transmission, achieving an 18-fold reduction. The proposed imaging scheme employs seven fan-shaped diverging transmit beams operating at a pulse repetition frequency of 7.7 kHz to obtain a high frame rate. The performance of the prototype is characterized, and its functionality is fully verified. The transducer exhibits a transmit efficiency of 28 Pa/V at 5 cm per element and a bandwidth of 60% in transmission. In receive, a dynamic range of 80 dB is measured with a minimum detectable pressure of 10 Pa per element. The element yield of the prototype is 98%, indicating the efficacy of the manufacturing process. The transducer is capable of imaging at a frame rate of up to 1000 volumes/s and is intended to cover a volume of 70° × 70° × 10 cm. These advanced imaging capabilities have the potential to support complex interventional procedures and enable full-volumetric flow, tissue, and electromechanical wave tracking in the heart. [ABSTRACT FROM AUTHOR]

Intensity modulation/direct detection (IM/DD) optical interconnect systems are susceptible to waveform distortion caused by complex nonlinearities. To reduce the effect of waveform distortion on signal transmission accuracy, in this paper, a random forest (RF) equalization algorithm based on decision tree (DT) integration is proposed for cost-sensitive IM/DD systems, which has the characteristics of nonlinear classification and regression. The performance of the RF equalizer is verified by simulation experiments on a 120 Gbps 8-level pulse amplitude modulation (PAM8) transmission system using an electro-absorption-modulated laser (EML). Simulation studies show that whether it is a back-to-back (B2B) transmission system or a 10 km optical fiber transmission system, the RF equalization scheme can achieve much better bit error rate (BER) performance than the traditional equalization scheme. In addition, in both transmission cases, the RF equalization scheme enables efficient classification of signals and is much less simpler than the artificial neural network (ANN) equalization scheme. [ABSTRACT FROM AUTHOR]

Reducing SIC operations and interference while maintaining the same radio resources for users in a cluster is a potential research direction in non‐orthogonal multiple access (NOMA) systems. In order to reach this goal, a streamlined user grouping is proposed for a four‐user cluster in downlink NOMA systems, which is carried out based on the in‐phase and quadrature components of a constellation. In terms of bit error rate performance, the proposed scheme is superior in comparison with the conventional NOMA without user grouping and phase rotation‐based user grouping. This improvement is achieved in light of the three positive points of pulse amplitude modulation, the Gray mapping rule, and the joint maximum‐likelihood detector. [ABSTRACT FROM AUTHOR]

Upper limb amputation severely affects the quality of life of individuals. Therefore, developing closed-loop upper-limb prostheses would enhance the sensory-motor capabilities of the prosthetic user. Considering design priorities based on user needs, the restoration of sensory feedback is one of the most desired features. This study focuses on employing Transcutaneous Electrical Nerve Stimulation (TENS) as a non-invasive somatotopic stimulation technique for restoring somatic sensations in upper-limb amputees. The aim of this study is to propose two encoding strategies to elicit force and slippage sensations in transradial amputees. The former aims at restoring three different levels of force through a Linear Pulse Amplitude Modulation (LPAM); the latter is devoted to elicit slippage sensations through Apparent Moving Sensation (AMS) by means of three different algorithms, i.e. the Pulse Amplitude Variation (PAV), the Pulse Width Variation (PWV) and Inter-Stimulus Delay Modulation (ISDM). Amputees had to characterize perceived sensations and to perform force and slippage recognition tasks. Results demonstrates that amputees were able to correctly identify low, medium and high levels of force, with an accuracy above the 80% and similarly, to also discriminate the slippage moving direction with a high accuracy above 90%, also highlighting that ISDM would be the most suitable method, among the three AMS strategies to deliver slippage sensations. It was demonstrated for the first time that the developed encoding strategies are effective methods to somatotopically reintroduce in the amputees, by means of TENS, force and slippage sensations. [ABSTRACT FROM AUTHOR]

Abstract Visible light communication can be leveraged to establish a wireless link between neurons in spiking networks even when neural areas are in relative motions. In electro‐optical spiking neural networks (SNN), parallel transmission is often achieved through wavelength division multiplexing (WDM). However, WDM can be prohibitive in certain applications due to the need for multiple narrow‐band transmitters and receivers with optical bandpass filters. Instead of WDM, an alternative approach of using non‐orthogonal multiple access is explored (NOMA) with a pulse amplitude modulation (PAM) scheme in optical axons to enable parallel neural paths in an SNN. To evaluate NOMA with PAM, the authors implement an electro‐optical SNN that controls the force of two anthropomorphic fingers actuated by the shape memory alloy‐based actuators. An optical reference channel is used to dynamically adjust the optical receiver's gain to improve the receiver's decoding performance. Experimental results demonstrate that the electro‐optical SNN can maintain control over the fingers and hold an object under varying channel conditions. Hence, the proposed system offers robustness against dynamic optical channels induced by the relative motion of neurons.

The changes in the cell physiology (growth rate, cell size, and cell DNA content), photosynthetic efficiency, toxicity, and sexuality under variable light and nutrient (phosphates) conditions were evaluated in cultures of the dinoflagellate Alexandrium minutum obtained from a red tide in the Ría de Vigo (NW Spain). The cells were grown at low (40 and 150 µE m−2 s−1), moderate (400 µE m−2 s−1), and high (800 µE m−2 s−1) light intensities in a medium with phosphate (P+) and without (P−). Cultures were acclimated to the irradiance conditions for one week, and the experiment was run for ~1 month. The cell size and DNA content were monitored via flow cytometry. Two different clonal strains were employed as a monoculture (in a P− or P+ medium) or, to foster sexuality and resting cyst formation, as a mixed culture (only in a P− medium). A. minutum growth was favored by increasing light intensities until 400 µE m−2 s−1. The DNA content analyses indicated the accumulation of S-phase cells at the highest light intensities (400 and 800 µE m−2 s−1) and therefore the negative effects on cell cycle progression. Only when the cells were grown in a P− medium did higher light intensities trigger dose-dependent, significantly higher toxicities in all the A. minutum cultures. This result suggests that the toxicity level is responsive to the combined effects of (high) light and (low) P stress. The cell size was not significantly affected by the light intensity or P conditions. The optimal light intensity for resting cyst formation was 150 µE m−2 s−1, with higher irradiances reducing the total encystment yield. Encystment was not observed at the lowest light intensity tested, indicative of the key role of low-level irradiance in gamete and/or zygote formation, in contrast to the stressor effect of excessive irradiance on planozygote formation and/or encystment.

We proposed micro light‐emitting diode (μLED) pixel circuits and driving methods. Because the wavelength shift of μLEDs occurs as the current density is varied, we designed pixel circuits based on pulse width modulation (PWM), hybrid PWM and pulse amplitude modulation (PAM), and quaternary digital driving. [ABSTRACT FROM AUTHOR]

Monolithic multi‐color light‐emitting diodes (LEDs) offer numerous advantages as multi‐functional lighting sources. However, the achievement of full‐color monolithic LEDs spanning from red to blue wavelengths is limited by the InN‐GaN material system. To overcome this limitation, this work demonstrates a new approach using hexagonal epitaxial lateral overgrowth to reduce the density of crystal defects and form micro‐surface structures. By utilizing arrowhead‐like surfaces in semipolar GaN films, indium incorporation can be controlled, leading to larger band‐filling effects and enabling full‐color red, green, and blue emissions from a single LED. Nonetheless, the red emission in monolithic full‐color LEDs is weaker than the blue emission due to the band‐filling induced blueshift that occurs with increasing current injection. To address this issue, pulse amplitude modulation and pulse width modulation modes are introduced to control the emission intensity from red to blue wavelengths. As a result, the study achieves a monolithic trichromatic white LED with color coordinates of (0.2985, 0.3948) and a color temperature of ≈6700 K by simultaneously emitting red, green, and blue LEDs with the same emission intensities. This achievement holds great promise for the development of high‐performance full‐color LEDs for multifunctional lighting sources that can span red, green, and blue wavelengths. [ABSTRACT FROM AUTHOR]

Incoherent addition of three monochromatic laser sources is used to create four distinctive power levels to match the profile of standard quaternary pulse amplitude modulation (PAM4). The proposed PAM4 signal generation results in a lower symbol error rate as compared to standard PAM4 systems. This design improves the signal-to-noise ratio as compared to existing PAM4 schemes and can reduce the cost and power consumption of existing 200 G or higher optical transceivers. [ABSTRACT FROM AUTHOR]

This paper presents an eye-opening monitor technique leveraging four-level pulse amplitude modulation (PAM-4) symbol transition characteristics. This approach facilitates the evaluation of data transmission quality concerning the adaptive coefficient settings of PAM-4 equalizers. The two-dimensional (2D) symbol transition mapping visually depicts the degree of intersymbol interference (ISI). This work expands upon the 2D mapping model introduced in [14], adding more theoretical analysis and new simulation results. Both simulation and empirical results indicate that 2D symbol mapping can assess the quality of PAM-4 data transmission impaired by ISI and can visually represent the equalization effect. [ABSTRACT FROM AUTHOR]

Early detection of pathogens can significantly reduce yield losses and improve the quality of agricultural products. This study compares the efficiency of hyperspectral (HS) imaging and pulse amplitude modulation (PAM) fluorometry to detect pathogens in plants. Reflectance spectra, normalized indices, and fluorescence parameters were studied in healthy and infected areas of leaves. Potato virus X with GFP fluorescent protein was used to assess the spread of infection throughout the plant. The study found that infection increased the reflectance of leaves in certain wavelength ranges. Analysis of the normalized reflectance indices (NRIs) revealed indices that were sensitive and insensitive to infection. NRI700/850 was optimal for virus detection; significant differences were detected on the 4th day after the virus arrived in the leaf. Maximum (Fv/Fm) and effective quantum yields of photosystem II (ΦPSII) and non-photochemical fluorescence quenching (NPQ) were almost unchanged at the early stage of infection. ΦPSII and NPQ in the transition state (a short time after actinic light was switched on) showed high sensitivity to infection. The higher sensitivity of PAM compared to HS imaging may be due to the possibility of assessing the physiological changes earlier than changes in leaf structure. [ABSTRACT FROM AUTHOR]

The speed of BLDC motor can be varied by applying PWM technique to inverter while the DC-link voltage is constant. Another approach is PAM technique in which the speed of motor is controlled by varying the DC-link voltage. The problem with PWM based drive is switching losses and also restriction in wide speed range operation when the drive is fed by low voltage battery. For wide speed range of operation, a high voltage battery or else a boost derived converter can be used in the front end of the inverter such that the DC-link voltages can be varied. By using boost converter, wide speed range control is possible along with the reduction of ripples in input battery current. This paper presents a mixed current control strategy which combines the inverter based (PWM) and the converter based (PAM) current controller, in addition to that the starting current is limited. The detailed mathematical analysis was derived for boost converter fed BLDC motor drive. The effect of proposed current control in the speed and starting current of motor is verified experimentally [ABSTRACT FROM AUTHOR]

Advancements in display technology have primarily focused on discovering new materials to develop thin‐film transistors (TFTs) that complement mainstream technologies. The emerging 2D semiconductors are one of the most promising candidates due to their ultra‐thin thickness, exceptional electrical qualities, and large‐scale availability. However, these atomically thin materials are delicate and typically prepared through standard gate‐first fabrication processes, necessitating their transfer onto specific substrates. In this study, a demonstration of an in situ gate‐last process for 2D semiconductor‐based TFTs technology is presented. This approach bypasses the yield‐limiting transfer process, enabling large‐scale display applications. The as‐fabricated MoS2 TFTs retains their intrinsic properties with a current density reaching ≈≈10 µA µm−1. Additionally, it is successfully showcased that the two transistor‐one capacitor active‐matrix display driving circuits with a high pixel yield. The patterned matrix exhibits no crosstalk and can be driven by either the pulse amplitude modulation or pulse width modulation scheme, offering flexible applications. [ABSTRACT FROM AUTHOR]