Modulation Loop Research Articles

Two-Dimensional Liquid Chromatography-Isotope Ratio Mass Spectrometry Opens New Possibilities in the Field of Compound-Specific Stable Isotope Analysis.

Compound-specific stable isotope analysis (CSIA) using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) is a powerful tool for determining the isotopic composition of carbon in analytes from complex mixtures. However, LC-IRMS methods are constrained to fully aqueous eluents. Previous efforts to overcome this limitation were unsuccessful, as the use of organic eluents in LC-IRMS was deemed impossible. In our study, we developed a two-dimensional (2D) LC-IRMS method that, for the first time, enables the use of organic-containing eluents in an LC-IRMS setting. Initial experiments with caffeine were performed using a sample loop modulator with 20% methanol in the mobile phase of the first dimension, while separating the organic fraction from the analyte in the second dimension. Comparing results with one-dimensional (1D) LC-IRMS methods showed high precision with δ13C values in 2D measurements (-34.98 ± 0.04 ‰) closely matching 1D results (-34.95 ± 0.12 ‰). In the next step, incorporation of an at-column dilution (ACD) modulator allowed for the successful use of methanol concentrations up to 40% in the first dimension, with the ACD modulator effectively mitigating both peak fronting and carbon background interference, without losing any precision or accuracy of the measurements (δ13CCaffeine = -34.92 ± 0.03 ‰). All developed methods showed a method detection limit lower than 5 mg of carbon L-1 (mgC L-1), which is a major improvement compared with previous studies on caffeine analysis with LC-IRMS. This proof-of-concept study on 2D-LC-IRMS opens vast new possibilities for future CSIA research across diverse fields, including environmental science, pharmaceuticals, and food chemistry.

Two-dimensional liquid chromatography based on different modulations for the determination of Aristolochic Acid Ⅰ in Asari Radix et Rhizoma

Asari Radix et Rhizoma (ARR) is a traditional Chinese herbal medicine derived from the genus Asarum in the Aristolochiaceae family, which has been widely used for years. Aristolochic acids in it significantly restrict the clinical application of ARR due to its nephrotoxic and carcinogenic properties, of which aristolochic acid I (AA I) is the most representative. The present paper describes two 2D-LC systems modulated by a sample loop and a trap column respectively for the detection of trace aristolochic acid I in ARR. An Inertsil ODS-3 C18 column and a Luna 3u Phenyl-Hexyl column were separately utilized in the first-dimension (1D) and second-dimension (2D) chromatography. A mixed-mode column with reversed-phase and ion-exchange was selected for trap column modulation of 2D-LC system. Method validation results showed that these two 2D-LC methods performed well in terms of repeatability, linearity, intra/interday precision, stability, and accuracy, which were demonstrated qualified for the simultaneous determination of trace AA I in ARR. The AA Ⅰ contents in three batches of ARR were 0.466∼0.812 μg/g by the two 2D-LC methods, which were below the limit requirement in the Chinese Pharmacopoeia. The comprehensive comparison between the two methods showed that a significant solute focusing effect was obtained by trap column modulation, which led to four-time lower LOD compared with loop modulation, while the loop-modulation-based method achieved higher analytical efficiency when analyzing a large batch of samples.

Two conserved arginine residues facilitate C-S bond cleavage and persulfide transfer in Suf family cysteine desulfurases.

Under conditions of oxidative stress or iron starvation, iron-sulfur cluster biogenesis in E. coli is initiated by the cysteine desulfurase, SufS, via the SUF pathway. SufS is a type II cysteine desulfurase that catalyzes the PLP-dependent breakage of an L-cysteine C-S bond to generate L-alanine and a covalent active site persulfide as products. The persulfide is transferred from SufS to SufE and then to the SufBC2D complex, which utilizes it in iron-sulfur cluster biogenesis. Several lines of evidence suggest two conserved arginine residues that line the solvent side of the SufS active site could be important for function. To investigate the mechanistic roles of R56 and R359, the residues were substituted using site-directed mutagenesis to obtain R56A/K and R359A/K SufS variants. Steady state kinetics indicated R56 and R359 have moderate defects in the desulfurase half reaction but major defects in the transpersulfurase step. Fluorescence polarization binding assays showed that the loss of activity was not due to a defect in forming the SufS/SufE complex. Structural characterization of R56A SufS shows loss of electron density for the α3-α4 loop at the R56/G57 positions, consistent with a requirement of R56 for proper loop conformation. The structure of R359A SufS exhibits a conformational change in the α3-α4 loop allowing R56 to enter the active site and mimics the residue's position in the PLP-cysteine aldimine structure. Taken together, the kinetic, binding, and structural data support a mechanism where R359 plays a role in linking SufS catalysis with modulation of the α3-α4 loop to promote a close-approach interaction of SufS and SufE conducive to persulfide transfer.

A fully integrated charge pump with double-loop control and differentiator-based transient enhancer for neural stimulation applications

This paper proposes a fully integrated charge pump (CP) with a double-loop control and a differentiator-based transient enhancer (DTE) for high-voltage neural stimulation applications. The double-loop control includes a clock-supply-voltage (VCLK) modulation loop and a pulse-frequency modulation (PFM) loop. The VCLK modulation loop regulates the output voltage by adjusting VCLK while the PFM loop adjusts the operating frequency of the CP in accordance with the load current in order to improve power efficiency. The proposed CP combines the function of output voltage regulation and VCLK generation into a single unit, leading to significantly reduced circuit complexity. The proposed double-loop control is capable of dealing with different dc current requirements while the proposed DTE suppresses the undershoots and overshoots of the output voltage during load transients. The proposed CP has been simulated using a 0.18-μm triple-well CMOS process and occupies an area of 0.537 mm2. The post-layout simulation results show that it can provide a regulated 9-V output voltage from a 3.6-V input voltage with a peak power efficiency of 73.4 % at 2-mA load condition. The Monte-Carlo simulation demonstrates that the overshoot and undershoot of the output voltage are kept below 3 % when undergoing a 2-mA load transient.

Encryption Technology of Optical Communication Network Based on Artificial Intelligence Technology

At present, research on enhancing information transmission security by addressing the two key issues of time delay signal elimination and key space expansion in chaotic secure communication systems has become a hot topic. In order to improve the encryption effect of optical communication network, this paper analyzes the encryption technology of optical communication network with AIT (artificial intelligence technology), designs the encryption scheme of optical communication network with the help of AIT, and takes the digital random sequence as the key. Moreover, this paper uses the digital signal processor to control the arbitrary wave generator to generate multi-ary step square wave, modulate the optical feedback and realize the highly random change of external cavity delay, thus eliminating the long external cavity delay information. This article proposes a chaotic secure communication system using digital sequences as keys and external cavity optical feedback, a device for forming a chaotic source through arbitrary wave phase modulation and single loop feedback, and a chaotic secure communication system with single feedback key phase modulation and injection synchronization. At the same time, this paper proposes a system scheme using single-loop optical feedback phase modulation, the CS(chaotic signal) with complex dynamic behavior is output, and the time-delay signal is effectively eliminated. This paper analyzes the strength and phase information of CS by autocorrelation and mutual information technology, and verifies the effect of optical communication network encryption technology. Through the analysis of experimental results, it can be seen that the optical communication network encryption technology based on AIT proposed in this paper can effectively improve the encryption effect of optical communication network. The algorithm model camera proposed in this article can be used in subsequent practice to improve communication encryption performance

More than the clock: distinct regulation of muscle function and metabolism by PER2 and RORα.

Circadian rhythms, governed by the dominant central clock, in addition to various peripheral clocks, regulate almost all biological processes, including sleep-wake cycles, hormone secretion and metabolism. In certain contexts, the regulation and function of the peripheral oscillations can be decoupled from the central clock. However, the specific mechanisms underlying muscle-intrinsic clock-dependent modulation of muscle function and metabolism remain unclear. We investigated the outcome of perturbations of the primary and secondary feedback loops of the molecular clock in skeletal muscle by specific gene ablation of Period circadian regulator 2 (Per2) and RAR-related orphan receptor alpha (Rorα), respectively. In both models, a dampening of core clock gene oscillation was observed, while the phase was preserved. Moreover, both loops seem to be involved in the homeostasis of amine groups. Highly divergent outcomes were seen for overall muscle gene expression, primarily affecting circadian rhythmicity in the PER2 knockouts and non-oscillating genes in the RORα knockouts, leading to distinct outcomes in terms of metabolome and phenotype. These results highlight the entanglement of the molecular clock and muscle plasticity and allude to specific functions of different clock components, i.e. the primary and secondary feedback loops, in this context. The reciprocal interaction between muscle contractility and circadian clocks might therefore be instrumental to determining a finely tuned adaptation of muscle tissue to perturbations in health and disease. KEY POINTS: Specific perturbations of the primary and secondary feedback loop of the molecular clock result in specific outcomes on muscle metabolism and function. Ablation of Per2 (primary loop) or Rorα (secondary loop) blunts the amplitude of core clock genes, in absence of a shift in phase. Perturbation of the primary feedback loop by deletion of PER2 primarily affects muscle gene oscillation. Knockout of RORα and the ensuing modulation of the secondary loop results in the aberrant expression of a large number of non-clock genes and proteins. The deletion of PER2 and RORα affects muscle metabolism and contractile function in a circadian manner, highlighting the central role of the molecular clock in modulating muscle plasticity.

Development of bipolar high-current correction magnet power supply for TPS facility

Taiwan Photon Source (TPS) is a globally renowned 3 GeV synchrotron accelerator light source. With a successful decade of operation, various subsystems have continuously improved and maintained an optimal research facility environment. Presently, there is a concerted effort towards energy conservation. This technical report focuses on the future development of the TPS-II Permanent Magnet Trim Coil Power Supply for the correction magnet, emphasizing a Bipole high-current correction magnet power source. According to the prototype specifications, the maximum output current is 20 A with an operating voltage of 48 V. This augmentation increases the amplitude of the magnetic field correction in the permanent magnet-associated Trim core, providing greater flexibility in manufacturing the permanent magnet correction coils. To design a power supply with high current and stability, the system adopts the Danisense DP50-IP-B DC Current Transducers (DCCT) as the current feedback component and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) as power switches in a full-bridge (H-bridge) configuration. The driving frequency is set at 40 kHz. Analog modulation control circuitry and protective circuits ensure precise control loop modulation. In the power laboratory, a hardware prototype circuit was constructed, featuring a 48 V input voltage, 20 A output current, a maximum power of 960W, and a current ripple component maintained within 100 μA. This experiment validates the control loop design of the prototype, showcasing the ability to achieve rapid and stable output current performance. Using a 1 V input reference signal for small-signal testing, the bandwidth displayed a -3 dB bandwidth of 8.51 kHz. Long-term current stability is within ± 10 ppm, and interface compatibility with the existing TPS correction magnet power source interface allows direct operation within the current system.

A Novel Approach for Realizing Loop-Filter in Low-Distortion Noise-Coupled ΣΔ Modulators

This paper presents an innovative general structure for a single-loop Sigma-Delta ([Formula: see text]) modulator that combines low-distortion and noise-coupled techniques to achieve high-resolution for low-power applications. The low-distortion technique adjusts the signal transfer function of the proposed structure to unity, while the noise-coupled technique enhances the order of quantization noise-shaping at the modulator output. These techniques were incorporated into the design to increase the modulator order without requiring additional operational amplifiers during its circuit implementation, resulting in a low-power modulator compared to similar structures. To reduce the number of required amplifiers, a second-order infinite impulse response (IIR) filter was used in the modulator loop filter, in place of two integrators. To assess the proposed structure’s performance, a third-order modulator sample was implemented and simulated for speech recognition applications, specifically, digital hearing aids, using 180[Formula: see text]nm complementary metal oxide semiconductor (CMOS) technology. The results indicate that for a third structure with a sampling rate of 64, an input sine signal of −6[Formula: see text]dBFS and a sampling frequency of 2.56[Formula: see text]MHz, the signal to noise plus distortion (SNDR) was 81.9[Formula: see text]dB, and the dynamic range (DR) was 88[Formula: see text]dB for a 20[Formula: see text]KHz bandwidth. The modulator’s power consumption was 126.9[Formula: see text][Formula: see text]W. Circuit and system-level simulations demonstrate the effectiveness of the proposed method.

Competition between drift and topological transport of colloidal particles in twisted magnetic patterns

We simulate the motion of paramagnetic particles between two magnetic patterns with hexagonal symmetry that are twisted at a magic angle. The resulting Morié pattern develops flat channels in the magnetic potential along which colloidal particles can be transported via a drift force of magnitude larger than a critical value. Colloidal transport is also possible via modulation loops of a uniform external field with time varying orientation, in which case the transport is topologically protected. Drift and topological transport compete or cooperate giving rise to several transport modes. Cooperation makes it possible to move particles at drift forces weaker than the critical force. At supercritical drift forces the competition between the transport modes results e.g. in an increase of the average speed of the particles in integer steps and in the occurrence of subharmonic responses. We characterize the system with a dynamical phase diagram of the average particle speed as a function of the direction of the topological transport and the magnitude of the drift force.

Spatial diversity processing mechanism based on the distributed underwater acoustic communication system.

To address the problem of unreliable single-link underwater acoustic communication caused by large signal delays and strong multipath effects in shallow water environments, this paper proposes a distributed underwater acoustic diversity communication system (DUA-DCS). DUA-DCS employs a maneuverable distributed cross-medium buoy network to form multiple distributed, non-coherent, and parallel communication links. In the uplink, a receiving diversity processing mechanism of joint decision feedback equalizer embedded phase-locked loop and maximum signal-to-interference ratio combining (DFE-PLL-MSIRC) is proposed to achieve waveform-level diversity combining of underwater signals. A phase-locked loop module is embedded in each branch of the decision feedback equalizer to eliminate the residual frequency and phase errors after Doppler compensation. Meanwhile, the combining coefficients are determined based on the maximum signal-to-interference ratio criterion, taking into account the residual inter-symbol interference after equalization, resulting in efficient and accurate computation. Additionally, the combined decision values are fed back to the feedback filters in each branch to ensure more accurate feedback output. Simulation and lake experiment results demonstrate that, compared to the single-link communication system, DFE-PLL-MSIRC can achieve a diversity gain of more than 5.2 dB and obtain about 3 dB more diversity gain than the comparison algorithm. And the BER of DFE-PLL-MSIRC can be reduced by at least one order of magnitude, which is lower by at least 0.6 order of magnitude compared to the comparison algorithm. In the downlink, a transmitting diversity processing mechanism of complex orthogonal space-time block coding (COSTBC) is proposed. By utilizing a newly designed generalized complex orthogonal transmission matrix, complete transmission diversity can be achieved at the coding rate of 3/4. Compared to the single-link communication system, the system can achieve a diversity gain of more than 6 dB.

A Cyto-silicon Hybrid System with On-chip Closed-loop Modulation.

We introduce a bioelectronic interface between biological electrogenic cells and a mixed-signal CMOS integrated circuit with an array of surface electrodes, where not only is the CMOS electrode array capable of electrophysiological recording and stimulation of the cells with 1,024 recording and stimulation channels, but it can also provide low-latency artificial signal pathways from cells it records to cells it stimulates. This on-chip closed-loop modulation has an intrinsic latency less than 5 μs. To demonstrate the utility of the on-chip closed loop modulation as an artificial feedback pathway between biological cells, we develop a silicon-cardiomyocyte self-sustained oscillator with a tunable frequency to which both the relevant part of the CMOS chip and cells are locked, and also a silicon-neuron interface with a silicon inhibitory connection between neuronal cells. This line of cyto-silicon hybrid system, where the boundary between biological and semiconductor systems is blurred, may find applications in prosthesis, brain-machine interface, and fundamental biology research.

A Compact MEMS Microphone Digital Readout System Using LDO and PPA-Less VCO-Based Delta-Sigma Modulation Technique

This paper presents a compact Micro-Electro-Mechanical System (MEMS) microphone digital readout system. The system is characterized by a low-dropout regulator (LDO) and a pre-amplifier and programmable-gain amplifier (PPA)-less voltage controlled oscillator (VCO)-based ΔΣ modulation technique, which improve compactness and design scalability. Specifically, to improve signal accuracy and maintain loop stability without a gain-tuning range trade-off, an active low pass filter (ALPF) and a current mode feed-forward path (CMFFP) are incorporated in a VCO-based delta-sigma modulation loop. By means of VCOs and SCG phase variation robustness and current source array feedback (CSAFB), the system achieves a high power supply rejection ratio (PSRR) and gain tuning without the need to design an extra regulator and PPA. The design was fabricated using a 180 nm Bipolar-CMOS-DMOS (BCD) process and measured at a 1.2 V supply voltage. According to the measurement results, the signal-to-noise and distortion ratio (SNDR) achieves 62 dB@1 kHz with 40 dB gain and a 10 kHz bandwidth. Furthermore, PSRR@1 kHz is below −55 dB, and power dissipation is within 57 µW.

An in-silico approach to the potential modulatory effect of taurine on sclerostin (SOST) and its probable role during osteoporosis

The cysteine-knot containing negative regulator of the Wnt (Wingless-related integration site) signaling pathway, sclerostin (SOST) is an emerging therapeutic target for osteoporosis. Its inhibition is responsible for the promotion of osteoblastogenesis. In this study, taurine, an amino sulfonic acid was used to study its mechanism of action for the inhibition of the SOST protein. Molecular docking and dynamic studies were performed as a part of the study whereby, it was observed that taurine binds to a probable allosteric pocket which allows it to modulate the structure of the SOST protein affecting all of the loops – loops 1, loop 2, and loop 3 – as well as the cysteine residues forming the cysteine-knot. The study also identified a set of seven taurine analogues that have better pharmacological activity than their parent compound using screening techniques. The conclusions derived from the study support that taurine has a probable antagonistic effect on the SOST protein directly through the modulation of HNQS motif and loops 2 and 3 and indirectly through its influence on the cysteine residues - 134, 165 and 167 C. Based on the results, it can be assumed that the binding of taurine with SOST protein probably reduces its binding affinity to the LRP6 protein greatly, while also inhibiting the target protein from anchoring to LRP4. Furthermore, it was noted that probable additional binding with any small molecule inhibitor (SMI) at the active site (PNAIG motif), in the presence of an already allosterically bound taurine, of the SOST protein would result in a complete potential antagonism of the target protein. Additionally, the study also uncovers the possible role of the GKWWRPS motif in providing stability to the PNAIG motif for the purpose of binding with LRP6. Communicated by Ramaswamy H. Sarma

A 143 dB Delta-Sigma Modulator for Biomedical Applications

This paper presents a single loop forth-order delta-sigma modulator topology of cascade of integrator with multiple feedback This paper presents a single loop forth-order delta-sigma modulator topology of cascade of integrator with multiple feedback (CIFB) . The number of levels in the quantizer increases for higher performance. The modulator noice transfer function (NTF) and signal transfer function (STF) exploited for higher performance. The out-of-band gain (OBG) of 1.5 selected considering the stability of higher order modulator. The high oversampling ratio (OSR) considered for small bandwidth applications. The maximum quantization noise is suppressed by NTF zeros optimization. A full-scale signal of the modulator is 0.55-V considering the higher order loop filter stability. Due to CIFB topology, there is no peaking in the STF while STF response is flat. The zeros of the NTF are optimized for maximum quantization noise and poles are placed inside the unit circle. The complete modulator loop filter has four integrators in the loop filter with multiple feedback digital-to-analog converter (DAC) for maximum stability. The complete modulator simulation shows it an achieve signal-to-noise (SNR) of 1.43 dB with oversampling ratio (OSR) of 128.

Tunable and switchable multi-wavelength actively Q-switched random fiber laser based on an electro-optic modulator and Sagnac loop filter.

In this article, an actively Q-switched multi-wavelength random fiber laser based on a Sagnac loop filter and electro-optic modulator is proposed and demonstrated experimentally. The random distributed feedback media is a section of a 25km long single-mode fiber. When the pump power is 350mW, the polarization angle of the Sagnac loop filter can be adjusted by polarization controller to achieve the switching of a single, double, triple, and quadruple channels laser output. In the case of a single laser channel, dual laser channels, and three laser channels output, multiple laser channels can be tuned simultaneously with a fixed wavelength interval. In addition, by changing the waveform of the external signal source, the light and dark pulses can be switched. Owing to the half-open cavity structure and the high gain of the erbium-doped fiber, the laser threshold was reduced to 25mW, and the light conversion efficiency was 0.67%. The laser is an ideal light source for medical imaging and long-distance sensing.

Tunable and switchable actively Q-switched multi-wavelength random fiber laser based on electro-optic modulator and Sagnac loop filter

Tunable and switchable actively Q-switched multi-wavelength random fiber laser based on electro-optic modulator and Sagnac loop filter

Voltage and frequency stabilization control strategy of virtual synchronous generator based on small signal model

Power system with large scale Inverter-based Resources (IBR) penetration is challenged with insufficient voltage and frequency support capacity. This paper restructures the control blocks of virtual synchronous generator (VSG) from the perspective of traditional synchronous generators’ control, the control path of the system over its active and reactive power output is clarified and simplified, which has facilitated the tuning of virtual inertia and damping parameters. Firstly, the small signal model of VSG control IBR is established, including instantaneous power calculation module, LC filter and power loop, voltage and current loops. In the meantime, the improved VSG voltage and frequency regulation control strategy is proposed based on the stability analysis of the small signal model. The stable operation range of the VSG control grid-connected inverter system is studied with the objective to improve the stability and robustness of the VSG-controlled grid-connected inverter system. Finally, MATLAB/Simulink simulation verifies the correctness of the proposed VSG’s dynamic model of power grid voltage and frequency regulation. The effectiveness of the restructures of VSG is verified as well. The results show that the control strategy not only improves the inertia of the system, but also enables the IBR to support the frequency and voltage of the system.

Packed modulation loops to reduce band broadening in two-dimensional liquid chromatography

Modulation interfaces employing sample loops are applied in many hyphenated separations such as two-dimensional liquid chromatography (2D-LC). When the first-dimension effluent in 2D-LC is eluted from the modulation loop, dispersion effects occur due to differences in the laminar flow velocity of the filling and emptying flow. These effects were recently studied by Moussa et al. whom recommended the use of coiled loops to promote radial diffusion and reduce this effect. In the 1980s, Coq et al. investigated the use of packed loops, which also promote radial diffusion, in large volume injection 1D-LC. Unfortunately, this concept was never investigated in the context of 2D-LC modulation. Our work evaluates use of packed loops in 2D-LC modulation and compares them to unpacked coiled and uncoiled modulation loops. The effect of the solvents, loop volume, differences in filling and emptying rates, and loop elution direction on the elution profile was investigated. Statistical moments were used as a pragmatic tool to quantify elution profile characteristics. Decreased dispersion was observed in all cases for the packed loops compared to unpacked loops and unpacked coiled loops. In particular for larger loop volumes the dispersion was reduced significantly. Furthermore, countercurrent elution resulted in narrower elution profiles in all cases compared to concurrent elution. We found that packed modulation loops are of high interested when analytes are not refocussed in the second-dimension separation (e.g. for size-exclusion chromatography). Moreover, our work suggests that the use of packed loops may aid in prevention of loop overfilling.

M³LVI: a multi-feature, multi-metric, multi-loop, LiDAR-visual-inertial odometry via smoothing and mapping

PurposeThe purpose of this paper is to propose a multi-feature, multi-metric and multi-loop tightly coupled LiDAR-visual-inertial odometry, M3LVI, for high-accuracy and robust state estimation and mapping.Design/methodology/approachM3LVI is built atop a factor graph and composed of two subsystems, a LiDAR-inertial system (LIS) and a visual-inertial system (VIS). LIS implements multi-feature extraction on point cloud, and then multi-metric transformation estimation is implemented to realize LiDAR odometry. LiDAR-enhanced images and IMU pre-integration have been used in VIS to realize visual odometry, providing a reliable initial guess for LIS matching module. Location recognition is performed by a dual loop module combined with Bag of Words and LiDAR-Iris to correct accumulated drift. M³LVI also functions properly when one of the subsystems failed, which greatly increases the robustness in degraded environments.FindingsQuantitative experiments were conducted on the KITTI data set and the campus data set to evaluate the M3LVI. The experimental results show the algorithm has higher pose estimation accuracy than existing methods.Practical implicationsThe proposed method can greatly improve the positioning and mapping accuracy of AGV, and has an important impact on AGV material distribution, which is one of the most important applications of industrial robots.Originality/valueM3LVI divides the original point cloud into six types, and uses multi-metric transformation estimation to estimate the state of robot and adopts factor graph optimization model to optimize the state estimation, which improves the accuracy of pose estimation. When one subsystem fails, the other system can complete the positioning work independently, which greatly increases the robustness in degraded environments.

Simultaneous modulation format identification and OSNR monitoring based on optoelectronic reservoir computing.

An approach for simultaneous modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring in digital coherent optical communications is proposed based on optoelectronic reservoir computing (RC) and the signal's amplitude histograms (AHs) obtained after the adaptive post-equalization. The optoelectronic RC is implemented using a Mach-Zehnder modulator and optoelectronic delay feedback loop. We investigate the performance of the proposed model with the number of symbols, bins of AHs and the hyperparameters of optoelectronic RC. The results show that 100% MFI accuracy can be achieved simultaneously with accurate OSNR estimation for different modulation formats under study. The lowest achievable OSNR estimation mean absolute errors for the dual-polarization (DP)-quadrature phase-shift keying signal, the DP-16-ary quadrature amplitude modulation (16QAM) signal, and the DP-64QAM signal are 0.2 dB, 0.32 dB and 0.53 dB, respectively. The robustness of the proposed scheme is also evaluated when the optoelectronic RC is in presence of additive white Gaussian noises. Then, a proof of concept experiment is demonstrated to further verify our proposed method. The proposed approach offers a potential solution for next-generation intelligent optical performance monitoring in the physical layer.