Ultralow RuO2 Doped NiS2 Heterojunction as a Multifunctional Electrocatalyst for Hydrogen Evolution linking to Biomass Organics Oxidation.

Hydrogen energy and biomass energy are green and sustainable forms that can solve the energy crisis all over the world. Electrocatalytic water splitting is a marvelous way to produce hydrogen and biomass platform molecules can be added into the electrolyte to reduce the overpotential and meanwhile are converted into some useful organics, but the key point is the design of electrocatalyst. Herein, ultralow noble metal Ru is doped into NiS2 to form RuO2@NiS2 heterojunction. Amongst them, the 0.06 RuO2@NiS2 has low overpotentials of 363 mV for OER and 71 mV for HER in 1 m KOH, which are superior to the RuO2 and Pt/C. Besides, the 0.06 RuO2@NiS2 shows a low overpotential of 173 mV in 1 m KOH+0.1 m glycerol, and the glycerol is oxidized to glyceraldehyde and formic acid via the high Faraday efficiency GlyOR process, and the splitting voltage is only 1.17 V. In addition, the 0.06 RuO2@NiS2 has a low overpotential of 206 mV in 1 m KOH+0.1 m glucose, and the glucose is converted to glucaric acid, lactic acid, and formic acid. This work has a "one stone three birds" effect for the production of hydrogen, low splitting voltage, and high-value-added biomass chemicals.

Pairwise Tomlinson-Harashima precoding for multiple-lane IM-DD transmissions.

As for the photonic interconnection based on the multiple-lane intensity modulation direct detection (IM-DD) transmission, both intra-channel inter-symbol-interference (ISI) originating from bandwidth constraint, and inter-channel performance discrepancy emerging from inter-channel component differences are the major bottleneck for the throughput enhancement. Here, we propose a pairwise Tomlinson-Harshima precoding (P-THP) scheme, in order to simultaneously deal with both intra-channel ISI and inter-channel performance discrepancy. The effective function of the proposed P-THP scheme is experimentally evaluated by transmitting 4-channel 81-GBaud PAM4 signals over 2 km standard single-mode fiber (SSMF). Compared with the conventional scheme with only applying THP on individual wavelength channel, the required optical received power (ROP) under the back-to-back (B2B) transmission can be reduced by 0.75∼1 dB with the help of proposed P-THP in different experimental component configurations, at the 7% hard decision forward error correction (HD-FEC) threshold of BER = 3.8 × 10-3. After the 2 km SSMF transmission, only the use of proposed P-THP can guarantee to reach the designated HD-FEC threshold, leading to a net rate of >600 Gbit/s.

Non-sweep DC component estimation method for a virtual-carrier assisted Kramers-Kronig receiver.

The Kramers-Kronig (KK) receiver has attracted much attention in short-range optical interconnection because of its ability to recover the phase of the signal from the intensity information through KK algorithm. In high-speed KK systems, such as virtual-carrier (VC) assisted ones, an alternating current (AC) coupled photo-detector (PD) is preferred due to relaxing the requirements of analog-to-digital converter (ADC) and electronic amplifier by filtering direct current (DC) component. However, the loss of the DC component will cause the KK algorithm to break down, so it is necessary to accurately recover DC value in the digital domain with multiple-sweep. In this paper, we propose what we believe is a novel non-sweep DC component estimation scheme based on optimized digital carrier-to-signal power ratio (OD-CSPR) method, which can accurately estimate the DC component with only 3-4 iterations in the scenario of VC-assisted KK receiver optical transmission. The scheme utilizes the one-dimensional search optimization algorithm based on golden section search and parabolic interpolation without sweeping. The simulation and experimental results of the proposed non-sweep OD-CSPR method show that the DC component can be estimated accurately in a large CSPR range, and the system performance is close to that of the conventional DC-sweep method. Compared with the typical defined digital CSPR (DD-CSPR) based optimization method, the proposed one can realize optical signal-to-noise ratio (OSNR) gains of 0.9 dB in the back-to-back (B2B) and 0.7 dB under 80 km fiber transmission scenarios respectively with a total bit rate of 160Gb/s.

Frame-rate adaptive fractionally spaced equalization enabled high-throughput optical camera communication.

Optical camera communication (OCC) has garnered worldwide research attention, due to its immunity to electromagnetic interference (EMI) and efficient utilization of spectrum resources. However, the limited bandwidth of the OCC system and the timing offset of the camera result in low system throughput. To enhance the OCC throughput, we propose and experimentally demonstrate a frame-rate adaptive fractionally spaced equalization algorithm (FA-FSE) for the joint mitigation of severe inter-symbol interference (ISI) and timing offset arising in OCC. Experimental results validate its correct and power-efficient function, leading to a record aggregated throughput of 250.96 kbit/s, when the 8-level pulse amplitude modulation (PAM-8) signals are independently modulated to eight chip-on-board light emitting diode (COB-LED) light strips, while simultaneously received by a smartphone 10 cm away.

Fractionally spaced nonlinear Tomlinson-Harashima precoding with weight clustering for C-band 100†Gbaud/λ PAM-4 transmission.

A nonlinear Tomlinson-Harashima precoding (NTHP) scheme has been verified for its capability to effectively address both the linear and nonlinear inter-symbol interferences (ISIs) arising in the intensity-modulation direct-detection (IM-DD) fiber optics transmission. Nevertheless, the application of the NTHP scheme may significantly increase the number of levels for the intensity modulated signals, resulting in the reduction of both eye width and receiver sensitivity. Here, we propose a fractionally spaced NTHP with a weight clustering (FS-NTHP-WC) scheme. Consequently, an accurate ISI feedback can be obtained to enlarge the eye width; meanwhile a hardware-efficient implementation without the equalization penalty can be achieved by weight clustering and pruning. When the C-band 100 Gbaud/λ PAM-4 signals are transmitted, our proposed FS-NTHP-WC scheme not only can achieve 0.25 dB and 0.5 dB gains of receiver sensitivity under back-to-back (B2B) and 2-km standard single-mode fiber (SSMF) transmission conditions, respectively, but can also cut down the computational complexity by 90% and 76% in terms of the number of multiplications and additions, respectively, in comparison with the NTHP scheme.

Low-loss and compact photonic lantern based on a step-index double cladding fiber.

The fulfilment of the adiabatic criterion is indispensable for the realization of a low-loss photonic lantern (PL), concurrently imposing a stringent restriction on the taper transition length of the PL. Here, by relaxing the adiabatic criterion, a low-loss and compact PL based on a step-index double cladding fiber (SI-DCF) is theoretically proposed and experimentally demonstrated. The use of SI-DCF can reduce the mode field diameter (MFD) expansion ratio during the tapering processing and greatly decrease the taper transition length required for adiabatic tapering. We initially evaluate the variation of both MFD and effective refractive index (RI) along the fiber tapering based on three types of fiber structures, including the modified standard single-mode fiber (SSMF), the graded-index fiber (GIF), and the proposed SI-DCF. In comparison with the commonly used fiber geometry, the SI-DCF can reduce the MFD expansion ratio from 77.73% to 38.81%, leading to more than half reduction of the tapering length for both 3-mode and 6-mode PLs. Then, two kinds of SI-DCF with different core diameters are fabricated to realize a 3-mode PL. The fabricated PL possesses a 1.5 cm tapering length and less than 0.2 dB insertion loss (IL). After splicing with the commercial few-mode fiber, the PL has an average IL of 0.6 dB and more than 13 dB LP11 mode purity over the C-band. Finally, a transfer matrix measurement indicates that the fabricated PLs have a mode coupling of less than -10 dB at 1550 nm.

Bias-drift insensitive full-field frequency response characterization of a thin-film lithium niobate-based intensity modulator.

We propose a rapid and precise scheme for characterizing the full-field frequency response of a thin-film lithium niobate-based intensity modulator (TFLN-IM) via a specially designed multi-tone microwave signal. Our proposed scheme remains insensitive to the bias-drift of IM. Experimental verification is implemented with a self-packaged TFLN-IM with a 3 dB bandwidth of 30 GHz. In comparison with the vector network analyzer (VNA) characterization results, the deviation values of the amplitude-frequency response (AFR) and phase-frequency response (PFR) within the 50 GHz bandwidth are below 0.3 dB and 0.15 rad, respectively. When the bias is drifted within 90% of the Vπ range, the deviation fluctuation values of AFR and PFR are less than 0.3 dB and 0.05 rad, respectively. With the help of the full-field response results, we can pre-compensate the TFLN-IM for the 64 Gbaud PAM-4 signals under the back-to-back (B2B) transmission, achieving a received optical power (ROP) gain of 2.3 dB. The versatility of our proposed full-field response characterization scheme can extend to various optical transceivers, offering the advantage of low cost, robust operation, and flexible implementation.

Single wavelength MDM-PDM 800-Gb/s net data rate transmission over a standard multimode fiber employing a Kramers-Kronig receiver.

We propose a high-speed multimode fiber short-reach optical interconnect system based on a Kramers-Kronig (KK) field reconstruction with the mode division multiplexing (MDM) and polarization division multiplexing (PDM) technology. In this work, the LP01, LP21a, LP21b, and LP02 modes are selected as independent channels to carry information. The demonstration achieved the 800 Gb/s net data rate per wavelength with a bit-rate-distance-product (BDP) of 8 Tb/s·km. To the best of our knowledge, this is the highest experimental record of a single wavelength BDP over the SMMF with KK detection. In addition, we discuss the system performance after all multiple-input multiple-output (MIMO) and partial MIMO processing and give guidance on the trade-off between system performance and computational resource.

On the multipath interference mitigation for high-speed IM-DD transmissions with Nyquist subcarrier modulation.

The performance of high-speed intensity modulation direct detection (IM-DD) transmissions is severely degraded due to the occurrence of multipath interference (MPI), especially when a higher-order modulation format is utilized. Here, we propose and demonstrate, for the first time to the best of our knowledge, that a Nyquist subcarrier modulation (Nyquist-SCM) format inherently exhibits resistance to the MPI. We experimentally evaluate the MPI tolerance by transmitting 56 Gbit/s PAM-4 signals and Nyquist-SCM 16QAM signals over the 2 km standard single-mode fiber (SSMF) when the C-band semiconductor laser with a linewidth of 1.7 MHz is utilized. In comparison with the PAM-4 format, the Nyquist-SCM 16QAM format can lead to an enhanced MPI tolerance of 4 dB at the KP4-FEC threshold of BER = 2 × 10-4. In addition, even with the help of MPI mitigation for the PAM-4 signals based on two newly reported methods, the utilization of Nyquist-SCM 16QAM signal can still guarantee an improved MPI tolerance of 1 dB.

Global, regional and national burdens of depression in adolescents and young adults aged 10-24 years, from 1990 to 2019: findings from the 2019 Global Burden of Disease study.

BACKGROUND: Depression is a significant mental health concern affecting the overall well-being of adolescents and young adults. Recently, the prevalence of depression has increased among young people. Nonetheless, there is little research delving into the longitudinal epidemiology of adolescent depression over time. AIMS: To investigate the longitudinal epidemiology of depression among adolescents and young adults aged 10-24 years. METHOD: Our research focused on young people (aged 10-24 years) with depression, using data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2019. We explored the age-standardised prevalence, incidence and disability-adjusted life-years (DALYs) of depression in different groups, including various regions, ages, genders and sociodemographic indices, from 1990 to 2019. RESULTS: The prevalence, incidence and DALYs of depression in young people increased globally between 1990 and 2019. Regionally, higher-income regions like High-Income North America and Australasia recorded rising age-standardised prevalence and incidence rates, whereas low- or middle-income regions mostly saw reductions. Nationally, countries such as Greenland, the USA and Palestine reported the highest age-standardised prevalence and incidence rates in 2019, whereas Qatar witnessed the largest growth over time. The burden disproportionately affected females across age groups and world regions. The most prominent age effect on incidence and prevalence rates was in those aged 20-24 years. The depression burden showed an unfavourable trend in younger cohorts born after 1980, with females reporting a higher cohort risk than males. CONCLUSIONS: Between 1990 and 2019, the general pattern of depression among adolescents varied according to age, gender, time period and generational cohort, across regions and nations.

Navigating sexual minority identity in sport: a qualitative exploration of sexual minority student-athletes in China.

BACKGROUND: Sexual minority student-athletes (SMSAs) face discrimination and identity conflicts in intercollegiate sport, impacting their participation and mental health. This study explores the perceptions of Chinese SMSAs regarding their sexual minority identities, aiming to fill the current gap in research related to non-Western countries. METHODS: A qualitative methodology was adopted, utilising the Interpretive Phenomenological Analysis (IPA) approach with self-categorization theory as the theoretical framework. Participants were recruited through purposive and snowball sampling, and data were collected via semi-structured interviews, documents, and field notes. Sixteen former and current Chinese SMSAs participated in this study. RESULTS: The study reveals four themes: hidden truths, prioritisation of athlete identity, self-stereotyping, and attempt. The results revealed that while SMSAs were common in intercollegiate sport, their identities were often concealed and not openly discussed. The predominant focus on athlete identity in sport overshadowed their sexual minority identities. Additionally, SMSAs developed self-stereotypes that influenced their thoughts and behaviours. The non-heterosexual team atmosphere in women's teams led to the development of intimate relationships among teammates. CONCLUSIONS: The findings from this study could be incorporated into existing sport policies to ensure the safe participation of SMSAs in Chinese intercollegiate sports. This research offers valuable insights for the development and implementation of inclusive policies. Future research in China could investigate the attitudes of coaches and heterosexual student-athletes toward sexual minority identities to inform targeted interventions.

Association between vitamin B2 intake and prostate-specific antigen in American men: 2003-2010 National Health and Nutrition Examination Survey.

BACKGROUND: Accumulating evidence suggests a pivotal role of vitamin B2 in the pathogenesis and progression of prostate cancer (PCa). Vitamin B2 intake has been postulated to modulate the screening rate for PCa by altering the concentration of prostate-specific antigen(PSA). However, the relationship between vitamin B2 and PSA remains indeterminate. Hence, we conducted a comprehensive evaluation of the association between vitamin B2 intake and PSA levels, utilizing data from the National Health and Nutrition Examination Survey (NHANES) database. METHODS: From a pool of 20,371 participants in the NHANES survey conducted between 2003 and 2010, a cohort of 2,323 participants was selected for the present study. The male participants were classified into four distinct groups based on their levels of vitamin B2 intake. We employed a multiple linear regression model and a non-parametric regression method to investigate the relationship between vitamin B2 and PSA levels. RESULTS: The study cohort comprised of 2,323 participants with a mean age of 54.95 years (± 11.73). Our findings revealed a statistically significant inverse correlation between vitamin B2 intake (mg) and PSA levels, with a reduction of 0.13 ng/ml PSA concentration for every unit increase in vitamin B2 intake. Furthermore, we employed a fully adjusted model to construct a smooth curve to explore the possible linear relationship between vitamin B2 intake and PSA concentration. CONCLUSIONS: Our study in American men has unveiled a notable inverse association between vitamin B2 intake and PSA levels, potentially posing a challenge for the identification of asymptomatic prostate cancer. Specifically, our findings suggest that individuals with higher vitamin B2 intake may be at a greater risk of being diagnosed with advanced prostate cancer in the future, possibly indicating a detection bias. These results may offer a novel explanation for the observed positive correlation between vitamin B2 intake and prostate cancer.

Meta-analysis of the dosage of balance training on ankle function and dynamic balance ability in patients with chronic ankle instability.

OBJECTIVE: To explore and compare the dosage of balance training on ankle function and dynamic balance ability in patients with chronic ankle instability (CAI). METHODS: The PubMed, Embase, Web of Science, Medline, and Cochrane databases were searched up to December 2023. Quality assessment was carried out using the risk-of-bias guidelines of the Cochrane Collaboration, and the standardized mean differences (SMD) or mean differences (MD) for each outcome were compute. RESULTS: Among 20 eligible studies, including 682 participants were analyzed in this meta-analysis. The results of the meta-analysis demonstrated that balance training was effective in enhancing ankle function with self-functional scores (SMD = 1.02; 95% CI, 0.61 to 1.43; p < 0.00001; I2 = 72%) and variables associated with the ability of dynamic balance such as SEBT-A (MD = 5.88; 95% CI, 3.37 to 8.40; p < 0.00001; I2 = 84%), SEBT-PM (MD = 5.47; 95% CI, 3.40 to 7.54; p < 0.00001; I2 = 61%), and SEBT-PL (MD = 6.04; 95% CI, 3.30 to 8.79; p < 0.0001; I2 = 79%) of CAI patients. Meta-regression indicated that the intervention time might be the principal cause of heterogeneity (p = 0.046) in self-functional scores. In subgroup analyses of self-functional score across intervention types, among the intervention time, more than 20 min and less than 30 min had the most favorable effect (MD = 1.21, 95% CI: 0.96 to 1.46, p < 0.00001, I2 = 55%); among the intervention period, 4 weeks (MD = 0.84, 95% CI: 0.50 to 1.19, p < 0.00001, I2 = 78%) and 6 weeks (MD = 1.21, 95% CI: 0.91 to 1.51, p < 0.00001, I2 = 71%) had significant effects; among the intervention frequency, 3 times (MD = 1.14, 95% CI: 0.89 to 1.38), p < 0.00001, I2 = 57%) had significant effects. Secondly, in subgroup analyses of SEBT across intervention types, a 4-week and 6-week intervention with balance training 3 times a week for 20-30 min is the optimal combination of interventions to improve SEBT (dynamic balance) in patients with chronic ankle instability. CONCLUSION: Balance training proves beneficial for ankle function in patients with CAI. Intervention time constitutes a major factor influencing self-function in patients with CAI. It is recommended that the optimal dosage of balance training for CAI involves intervention three times a week, lasting for 20 to 30 min over a period of 4 to 6 weeks for superior rehabilitation.

Global, regional, and national burden and trends of migraine among youths and young adults aged 15-39 years from 1990 to 2021: findings from the global burden of disease study 2021.

BACKGROUND: Migraine, a widespread neurological condition, substantially affects the quality of life, particularly for adolescents and young adults. While its impact is significant, there remains a paucity of comprehensive global research on the burden of migraine in younger demographics. Our study sought to elucidate the global prevalence, incidence, and disability-adjusted life-years (DALYs) associated with migraine in the 15-39 age group from 1990 to 2021, utilizing data from the Global Burden of Disease (GBD) 2021 study. METHODS: Our comprehensive study analyzed migraine data from the GBD 2021 report, examining the prevalence, incidence, and DALYs across 204 countries and territories over a 32-year span. We stratified the information by age, sex, year, geographical region, and Socio-demographic Index (SDI). To evaluate temporal trends in these metrics, we employed the estimated annual percentage change (EAPC) calculation. RESULTS: Between 1990 and 2021, the worldwide prevalence of migraine among 15-39 year-olds increased substantially. By 2021, an estimated 593.8 million cases were reported, representing a 39.52% rise from 425.6 million cases in 1990. Global trends showed increases in age-standardized prevalence rate, incidence rate, and DALY rate for migraine during this period. The EAPC were positive for all three metrics: 0.09 for ASPR, 0.03 for ASIR, and 0.09 for DALY rate. Regions with medium SDI reported the highest absolute numbers of prevalent cases, incident cases, and DALYs in 2021. However, high SDI regions demonstrated the most elevated rates overall. Across the globe, migraine prevalence peaked in the 35-39 age group. Notably, female rates consistently exceeded male rates across all age categories. CONCLUSION: The global impact of migraine on youths and young adults has grown considerably from 1990 to 2021, revealing notable variations across SDI regions, countries, age groups, and sexes. This escalating burden necessitates targeted interventions and public health initiatives, especially in areas and populations disproportionately affected by migraine.

Frequency offset estimation for nonlinear frequency division multiplexing with continuous spectrum modulation.

Carrier frequency offset (CFO) estimation is very important for the optical fiber communications and has been studied widely in linear coherent systems, while only a few works have been reported for nonlinear Fourier transform (NFT) based systems. In continuous spectrum (CS) modulation nonlinear frequency division multiplexing (CS-NFDM) systems, frequency offset (FO) has a great influence on its performance, requiring an improved frequency offset estimation (FOE) method. We found that the oversampling rate R0 adopted in NFDM to ensure the accuracy of the NFT and inverse NFT (INFT) calculations, would cause the estimation accuracy of the traditional FFT-FOE method to decrease by R0 times. Moreover, CS-NFDM signals with higher baud rate require more subcarriers and then result in an oversampling factor greater than 16. This makes the traditional FFT-FOE method be ineffective to use the common training sequence (TS) overhead to meet the FOE error requirement of CS-NFDM system. Therefore, a modified FOE method based on FFT assisted by TS and autocorrelation has been proposed. The theoretical analysis and simulation results show that the proposed method is applicable to CS-NFDM system, no matter what modulation format is used. For 512 subcarriers, with a high rate of 70GBaud and the TS length of 8192, the proposed method can obtain a minimum FO estimation error about 0.1 MHz, which is better than the other two typical FFT-FOE and Schmidl & Cox methods. In addition, the proposed method can save at least 87.5% and 50% overhead. Thus, the proposed method has obvious improvement for CS-NFDM system with requiring high oversampling rate.

Mode multicasting without parasitic wavelength conversion.

Optical multicasting, which involves delivering an input signal to multiple different channels simultaneously, is a key function to improve network performance. By exploiting individual spatial modes as independent channels, mode-division-multiplexing (MDM) can solve the capacity crunch of traditional standard single-mode fiber (SSMF) transmission system. In order to realize mode multicasting with high flexibility in future hybrid wavelength-division-multiplexing (WDM) and MDM networks, we propose a mode multicasting scheme without parasitic wavelength conversion, based on the inter-modal four-wave mixing (FWM) arising in the few-mode fiber (FMF). The operation mechanism including nonlinear phase shift for efficient mode multicasting is analytically identified. Then, based on the derived operation condition, we numerically investigate the impact of the dual-pump power and the FMF length on the performance of mode multicasting. By properly setting the pump wavelength and the dual-pump power, mode multicasting performance, in terms of mode multicasting efficiency, 3-dB bandwidth, and destination wavelength, can be tuned according to various application scenarios. After the performance optimization, mode multicasting of 25-Gbaud and 100-Gbaud 16-quadratic-amplitude modulation (16-QAM) signals is numerically demonstrated. The proposed reconfigurable mode multicasting is promising for future WDM-MDM networks.

Characterization of differential modal group delay in few-mode fiber using a digital re-sampling technique.

We characterize the differential modal group delay (DMGD) arising in few-mode fibers (FMFs) based on the digital re-sampling technique, which is commonly used in current digital signal processing flow at the receiver-side. When the DMGD of a 291-m two-mode fiber is characterized over the C-band by using a 500-Mb/s non-return-to-zero (NRZ) signal and 1-GSa/s real-time oscilloscope, the experimental results are consistent with the DMGD obtained from the traditional time-of-flight (TOF) method. However, the wide-bandwidth instruments of the traditional TOF method can be replaced by cheap ones with a bandwidth of only a few hundred MHz, but the same temporal precision is achieved. Moreover, our proposed DMGD characterization method is not limited by the number of guided modes arising in the FMF, together with the capability to obtain both the DMGD value and its sign between two arbitrary guided modes.

Complex amplitude field recovery of a scattering media obstructed object with multi-captured images.

An iterative-based method for recovering the complex amplitude field behind scattering media is presented in this Letter. This method compensates the random phase modulation of scattering media by using multiple captured scattered light fields. Complex amplitude reconstruction with local iterative averaging of scattered light fields, and double weighted feedback is efficiently applied. Two feasible types of system setups, with varying detector positions and wavelength, are proposed. Simulations and proof-of-concept experiments are employed to demonstrate the effectiveness of the proposed method in reconstructing complex amplitude of a hidden target.

Transmitter dispersion eye closure quaternary assessment based on linear CNN with 1 × 1 convolutional kernel.

Transmitter dispersion eye closure quaternary (TDECQ) is a vital metric to characterize the quality of four-level pulse amplitude modulation (PAM-4) optical signals. However, the traditional TDECQ assessment scheme is complex and time consuming, with heavy iterative operations. Therefore, accelerating the TDECQ assessment has great significance for photonic data-center interconnection (DCI) applications. Here, we propose and experimentally demonstrate a TDECQ assessment based on linear-convolutional neural network (L-CNN) with the 1 × 1 convolutional kernel to reduce the implementation complexity. Our experimental results verify that the lightweight L-CNN can realize the accurate TDECQ assessment, without the involvement of nonlinear activation functions (NAFs). The mean absolute error (MAE) of 26.5625 and 53.125 GBaud PAM-4 signals are 0.16 dB and 0.18 dB, respectively, over a TDECQ range from 1.5 to 4.0 dB. Meanwhile, in comparison with existing CNN-based schemes, the L-CNN based TDECQ assessment scheme only needs 2048 multiplications, which have been reduced by five orders of magnitude.

C-band 100-GBaud/λ PAM-4 transmission enabled by hardware-efficient nonlinear equalizer with weight-sharing pruning.

A Volterra nonlinear equalizer (VNLE) can effectively mitigate both linear and nonlinear impairments arising in intensity-modulation direct-detection (IM-DD) transmission systems. However, the high computational complexity of the VNLE hinders its applications. Here, we propose a hardware-efficient Volterra equalizer with weight-sharing pruning (VE-WSP). Such an equalizer first uses the k-means++ clustering algorithm for the weight sharing within the same cluster, and then ranks the cluster centroid weight for pruning, leading to a significant computational complexity reduction without sacrificing any equalization performance. We experimentally verified that the use of VE-WSP can enable the C-band 100-GBaud/λ PAM-4 transmission over a 1-km standard single-mode fiber (SSMF), to reach the 20% soft-decision forward error correction (SD-FEC) threshold. Meanwhile, the proposed VE-WSP can reduce the computational complexity by 51% and 21%, in terms of multiplication and addition, respectively, in comparison with the VNLE.