Single-channel Transmission Research Articles

Coupled topological edge and corner states in two-dimensional phononic heterostructures with nonsymmorphic symmetries

The exciting discovery of topological phononic states has aroused great interest in the field of acoustic wave control. However, conventional topological edge states and corner states localized at the interface and corner of the two-phase domain wall structures are limited by single channel transmission characteristics, which decreases the flexibility of designing multi-channel acoustic wave devices. Here, we propose a two-dimensional (2D) topological phononic heterostructure with nonsymmorphic symmetries to realize the multiple interface topological multimode interference effect based on the coupling of topological edge and corner states. Topological phase transitions are achieved by altering the rotation angle of the split-ring scatterers in a square lattice. The coupled edge states are generated by the coupling between the edge states of ordinary-topological-ordinary (OTO) interfaces. Moreover, the higher-order topology of the square phononic crystals (PCs) is characterized by nontrivial bulk polarization, the topological and coupled corner states splitting into two pairs appear in the square OTO bend structure owing to the nonsymmorphic PC lack of mirror symmetries. Finally, the topological robustness of the multimode interference effect of coupled edge and corner states against defects is demonstrated. Our results pave the way for guiding and trapping acoustic waves in topological nonsymmorphic heterostructures, whose multi-channel transmission capability can be employed for designing topological phononic filters, couplers and multiplexers.

Electrochemical Characterization of Nickel/Gadolinia Doped Ceria Fuel Electrodes under H2/H2O/CO/CO2-Atmospheres

Modelling of the co-electrolysis process requires understanding of the underlying reaction pathways under H2/H2O/CO/CO2-atmospheres. These include the electrochemical steam reduction/hydrogen oxidation, the electrochemical CO2 reduction/CO oxidation and their coupling via the catalytic (reverse) water gas shift reaction ((R)WGS). The assumption of a very fast RWGS and therefore neglectable electrochemical CO2 conversion is commonly used to model the co-electrolysis process. In contrast, previous studies on Ni/GDC fuel electrodes suggest that the electrochemical conversion of CO/CO2 can be present in H2/H2O/CO/CO2-atmospheres. To deconvolute surface-related and non-surface-related processes in the impedance response we present results from a complex variation of operating parameters for process identification by the use of electrochemical impedance spectroscopy and the subsequent impedance analysis by the distribution of relaxation times. A physically meaningful equivalent circuit model, based on a single channel transmission line, is then derived. The model enables quantification of the surface reaction resistance under varied C/H-ratios. From a kinetic analysis it is shown that the electrochemical H2/H2O conversion is dominant for yCO+yCO2≤ 50% and electrochemical CO/CO2-conversion onsets from yCO+yCO2 ≥ 60%.

Inhomogeneity mitigation for diffusion weighted MRI at 7T using TR-FOCI pulses.

The purpose of this study is to improve the image quality of diffusion-weighted images obtained with a single RF transmit channel 7 T MRI setup using time-resampled frequency-offset corrected inversion (TR-FOCI) pulses to refocus the spins in a twice-refocused spin-echo readout scheme. We replaced the conventional Shinnar-Le Roux-pulses in the twice refocused diffusion sequence with TR-FOCI pulses. The slice profiles were evaluated in simulation and experimentally in phantoms. The image quality was evaluated in vivo comparing the Shinnar-Le Roux and TR-FOCI implementation using a b value of 0 and of 1000 s/mm2. The b0 and diffusion-weighted images acquired using the modified sequence improved the image quality across the whole brain. A region of interest-based analysis showed an SNR increase of 113% and 66% for the nondiffusion-weighted (b0) and the diffusion-weighted (b = 1000 s/mm2) images in the temporal lobes, respectively. Investigation of all slices showed that the adiabatic pulses mitigated inhomogeneity globally using a conventional single-channel transmission setup. The TR-FOCI pulse can be used in a twice-refocused spin-echo diffusion pulse sequence to mitigate the impact of inhomogeneity on the signal intensity across the brain at 7 T. However, further work is needed to address SAR limitations.

Fractal acoustic metamaterials with near-zero index and negative properties

A subwavelength two-dimensional fractal acoustic metamaterial was designed based on the Hilbert fractal curve and spatial curl concept. The equivalent acoustic parameters of the fractal acoustic metamaterial were extracted by the equivalent parameter method, and the acoustic metamaterial exhibited near-zero density and negative density properties at specific frequency points. The analysis based on the finite element method shows that the acoustic prism constructed by using the near-zero density property of this acoustic metamaterial can realize the single-channel acoustic unidirectional transmission and multichannel acoustic unidirectional transmission effect, the bidirectional acoustic conduction and multidirectional acoustic conduction effect, and the bidirectional sound insulation effect. We also investigated the effect of embedding rigid scatterers inside the prism on the acoustic one-way transmission performance. Based on the acoustic direction selection mechanism of the near-zero refractive index acoustic metamaterial, arbitrary modulation of the plane acoustic wave emission direction can be achieved by changing the angle of the acoustic prism emission interface. In addition, the negative density property of the acoustic metamaterial is used to design an acoustic triangular prism to realize the acoustic negative refraction phenomenon. next, we discuss the trend of the influence of the geometrical parameters of the metamaterial on its effective properties, where the modulating wave frequency gradually moves to lower frequencies as the geometrical parameters of the metamaterial structural units increase. Finally, we fabricated the corresponding experimental samples of acoustic prisms using 3d printing technology and conducted experimental tests. The results show that the measured acoustic pressure field distribution matches well with the analytical results of the finite element method, which proves the accuracy of the results and the reasonableness of the structure, indicating that acoustic prisms composed of this acoustic super-material are expected to be used in ultrasonic imaging, acoustic energy rectification and other fields.

Design of a Ka-Band Heterogeneous Integrated T/R Module of Phased Array Antenna

The central element of a phased array antenna that performs beam electrical scanning, as well as signal transmission and reception, is the transceiver (T/R) module. Higher standards have been set for the integration, volume, power consumption, stability, and environmental adaptability of T/R modules due to the increased operating frequency of phased array antennas, the variability of application platforms, and the diversified development of system functions. Device-based multichannel T/R modules are the key to realizing low-profile Ka-band phased array antenna microsystem architecture. The design and implementation of a low-profile, high-performance, and highly integrated Ka-band phased array antenna T/R module are examined in this paper. Additionally, a dependable Ka-band four-channel T/R module based on Si/GaAs/Low Temperature Co-fired Ceramic (LTCC), applying multi-material heterogeneous integration architecture, is proposed and fabricated. The chip architecture, transceiver link, LTCC substrates, interconnect interface, and packaging are all taken into consideration when designing the T/R module. When compared to a standard phased array antenna, the module’s profile shrunk from 40 mm to 8 mm, and its overall dimensions are only 10.8 mm × 10 mm × 3 mm. It weighs 1 g, and with the same specs, the single channel volume was reduced by 95%. The T/R module has an output power of ≥26 dBm for single-channel transmission, an efficiency of ≥25%, and a noise factor of ≤4.4 dB. When compared to T/R modules based on System-on-Chip (SOC) devices, the RF performance has significantly improved, as seen by an increase in single channel output power and a decrease in the receiving noise factor. This work lays a foundation for the devitalization and engineering application of T/R modules in highly reliable application scenarios.

Demodulation Performance Comparison of High-Speed Coherent Nyquist Pulse Signal with Analog and Digital Demultiplexing Schemes

We compare the demodulation performance of an analog OTDM demultiplexing scheme and digitized OTDM demultiplexing with an ultrahigh-speed digital signal processor in a single-channel OTDM coherent Nyquist pulse transmission. We evaluated the demodulation performance for 40, 80, and 160 Gbaud OTDM signals with a baseline rate of 10 Gbaud. As a result, we clarified that the analog scheme performs significantly better since the bandwidth for handling the demultiplexed signal is as narrow as 10 GHz regardless of the symbol rate. This enables us to use a low-speed A/D converter (ADC) with a large effective number of bits (ENOB). On the other hand, in the digital scheme, the higher the symbol rate becomes, the more bandwidth the receiver requires. Therefore, it is necessary to use an ultrahigh-speed ADC with a low ENOB for a 160 Gbaud signal. We measured the ENOB of the ultrahigh-speed ADC used in the digital scheme and showed that the measured ENOB was approximately 1.5 bits lower than that of the low-speed ADC used in the analog scheme. This 1.5-bit decrease causes a large degradation in the demodulation performance obtained with the digital demultiplexing scheme.

Distributed Compressive Sensing for Wireless Signal Transmission in Structural Health Monitoring: An Adaptive Hierarchical Bayesian Model-Based Approach.

Signal transmission plays an important role in the daily operation of structural health monitoring (SHM) systems. In wireless sensor networks, transmission loss often occurs and threatens reliable data delivery. The massive amount of data monitoring also leads to a high signal transmission and storage cost throughout the system's service life. Compressive Sensing (CS) provides a novel perspective on alleviating these problems. Based on the sparsity of vibration signals in the frequency domain, CS can reconstruct a nearly complete signal from just a few measurements. This can improve the robustness of data loss while facilitating data compression to reduce transmission demands. Extended from CS methods, distributed compressive sensing (DCS) can exploit the correlation across multiple measurement vectors (MMV) to jointly recover the multi-channel signals with similar sparse patterns, which can effectively enhance the reconstruction quality. In this paper, a comprehensive DCS framework for wireless signal transmission in SHM is constructed, incorporating the process of data compression and transmission loss together. Unlike the basic DCS formulation, the proposed framework not only activates the inter-correlation among channels but also provides flexibility and independence to single-channel transmission. To promote signal sparsity, a hierarchical Bayesian model using Laplace priors is built and further improved as the fast iterative DCS-Laplace algorithm for large-scale reconstruction tasks. Vibration signals (e.g., dynamic displacement and accelerations) acquired from real-life SHM systems are used to simulate the whole process of wireless transmission and test the algorithm's performance. The results demonstrate that (1) DCS-Laplace is an adaptative algorithm that can actively adapt to signals with various sparsity by adjusting the penalty term to achieve optimal performance; (2) compared with CS methods, DCS methods can effectively improve the reconstruction quality of multi-channel signals; (3) the Laplace method has advantages over the OMP method in terms of reconstruction performance and applicability, which is a better choice in SHM wireless signal transmission.

Nonlinear wave equation for wavelength/polarization multiplexed signals in fiber transmission

Wavelength/polarization division multiplexing (WDM/PDM) schemes are standardly employed in trunk transmission systems, for which fiber nonlinearity is a serious problem. Generally, the signal transmission characteristics suffering from fiber nonlinearity have been analyzed using the nonlinear Schrödinger equation or the Manakov equation, which was originally presented for single-channel transmission. Therefore, when they are applied to WDM systems, the polarization states of each wavelength light are assumed to be identical, which is not fit to long-haul transmissions wherein the polarization states of WDM signals randomly and independently vary during the fiber transmission. Considering such conditions in WDM/PDM transmission systems, this paper presents a nonlinear wave equation for WDM/PDM signal transmission, which describes the signal behavior in systems where the polarization states of each WDM light are fully random and independent. A formula modified from the Manakov equation is derived using the polarization state coordinate of each signal light in WDM/PDM systems.

Two-Lane DNN Equalizer Using Balanced Random-Oversampling for W-Band PS-16QAM RoF Delivery over 4.6 km

For W-band long-range mm-wave wireless transmission systems, nonlinearity issues resulting from photoelectric devices, optical fibers, and wireless power amplifiers can be handled by deep learning equalization algorithms. In addition, the PS technique is considered an effective measure to further increase the capacity of the modulation-constraint channel. However, since the probabilistic distribution of m-QAM varies with the amplitude, there have been difficulties in learning valuable information from the minority class. This limits the benefit of nonlinear equalization. To overcome the imbalanced machine learning problem, we propose a novel two-lane DNN (TLD) equalizer using the random oversampling (ROS) technique in this paper. The combination of PS at the transmitter and ROS at the receiver improved the overall performance of the W-band wireless transmission system, and our 4.6-km ROF delivery experiment verified its effectiveness for the W-band mm-wave PS-16QAM system. Based on our proposed equalization scheme, we achieved single-channel 10-Gbaud W-band PS-16QAM wireless transmission over a 100 m optical fiber link and a 4.6 km wireless air-free distance. The results show that compared with the typical TLD without ROS, the TLD-ROS can improve the receiver‘s sensitivity by 1 dB. Furthermore, a reduction of 45.6% in complexity was achieved, and we were able to reduce training samples by 15.5%. Considering the actual wireless physical layer and its requirements, there is much to be gained from the joint use of deep learning and balanced data pre-processing techniques.

State estimation of reaction-diffusion inertial neural networks with Markovian switching channels via conjunct measurement

This paper addresses the state estimation of reaction-diffusion inertial neural networks (RDINNs) with Markovian switching channels based on conjunct measurement method. First, a suitable variable substitution is employed to transform the original second-order differential system into a first-order one, and a time-space sampled-data measurement strategy is adopted to replace the traditional continuous measurement method. As single-channel transmission may suffer from various communication deficiencies, a multi-channel switching scheme is considered in this paper to improve transmission efficiency. Then, by constructing Lyapunov-Krasovskii functional with relaxed conditions, sufficient conditions are derived to ensure that the error system is asymptotically stable. Finally, the feasibility of the proposed method is further validated by simulation results.

Photonics-Aided Terahertz-Wave Wireless Communication Employing Advanced Post-Equalizer

In this letter, a novel MIMO linear and Volterra nonlinear equalizer (MIMOL-VNLE) is proposed for signal recovery in the photonics-aided terahertz wave (THz-wave) wireless communication system, which is proven to compensate for linear impairments, nonlinear impairments, and I/Q mixing effects simultaneously. Adopting the proposed algorithm, we experimentally demonstrated the single-channel transmission of 20-Gbaud 16-ary quadrature amplitude modulation (16QAM) THz-wave signal at 440-GHz over 1-m wireless distance.

Optimized ultrahigh field parallel transmission workflow using rapid presaturated TurboFLASH transmit field mapping with a three-dimensional centric single-shot readout.

To evaluate the usage of three-dimensional (3D) presaturated TurboFLASH (satTFL) for and mapping on single channel and parallel transmission (pTx) systems. maps recorded with 3D satTFL were compared to maps from three other 3D mapping sequences in an agar phantom. Furthermore, individual-channel maps of 18 human subjects were recorded with 3D satTFL using interferometry. A neural network was trained for masking of the maps. Out of the sequences compared satTFL was the only one with a mapping range exceeding well over 90°. In regions with lower flip angles there was high correspondence between satTFL and AFI. DREAM and double angle method also showed high qualitative similarity, however the magnitude differed from the other two measurements. The individual-channel maps were successfully used for pTx pulse calculation in a separate study. 3D satTFL can record high-quality maps with a high dynamic range in a short time. Correspondence with AFI maps is high, while measurement duration is reduced drastically.

10.83 Tb/s Over 800 Km Nonlinear Frequency Division Multiplexing WDM Transmission

Nonlinear frequency division multiplexing (NFDM) transmission scheme has attracted great interest in optical fiber communication systems due to its potential for surpassing the Kerr nonlinearity limit. There have been very active studies on single-channel NFDM transmission systems recently. However, up to now, few experiments have validated the feasibility of applying NFDM into wavelength division multiplexing (WDM) optical communication systems toward high-capacity transmission for wideband coverage. Moreover, the overall performance of the NFDM system is restricted due to many challenges in theoretical design and practical implementation. Novel neural network-based equalization methods contribute to eliminating multi-dimensional crosstalk, hence prompting the NFDM system performance. In this article, we experimentally demonstrate a high-capacity NFDM-WDM transmission system enabled by the newly developed digital signal processing (DSP) algorithms. With data modulation on the continuous spectrum in nonlinear frequency domain, a 25-channel WDM system with polarization division multiplexing (PDM) 16-ary quadrature amplitude modulation (16-QAM) transmitting over 800 km standard single-mode fiber (SSMF) is successfully achieved. To mitigate the undesirable correlations between the nonlinear continuous spectral components, a nonlinear spectrum equalization scheme based on artificial neural network (ANN) is utilized in the receiver side DSP. Through this ANN-based spectrum equalization, a 0.63 dB Q <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -factor gain is achieved compared to the conventional equalization scheme. A record transmission capacity of 10.83 Tb/s is achieved in a 25-channel WDM system over 800 km SSMF, with a remarkable single-channel line rate of 433.3 Gb/s. Our work reports the highest capacity NFDM-WDM transmission up to date and helps to further explore the inherent ability of NFDM to resist fiber channel nonlinearity.

Research on High-Frequency Information-Transmission Method of Smart Grid Based on CNN-LSTM Model

In order to solve the problem of the slow transmission rate of high-frequency information in smart grid and improve the efficiency of information transmission, a research method of high-frequency information transmission in smart grids based on the CNN-LSTM model is proposed. It effectively combines the superiority of the CNN algorithm for high-frequency information feature extraction and the learning ability of the LSTM algorithm for global features of high-frequency information. Meanwhile, the client buffer is divided by the VLAN area division method, which avoids the buffer being too large due to line congestion. The intelligent control module is adopted to change the traditional control concept. In addition, the neural network optimization control module is used for intelligent control, which ensures the feedback speed of the control terminal and avoids the problem of increasing the buffer area caused by the feedback time difference. The experimental results show that via the method in this paper, the total efficiency of single-channel transmission reaches 96% and the transmission rate reaches 46 bit/s; the total efficiency of multiplex transmission is 89% and the transmission rate reaches 75 bit/s. It is verified that the method proposed in this paper has a fast transmission rate and high efficiency.

OFDM-PS-256QAM signal delivery at 47.45 Gb/s over 4.6-kilometers wireless distance at the W band

Photonics technology is a promising way to generate high-frequency millimeter waves, which is also a key technology to realize the convergence of fiber-optic and wireless communication. To meet the actual application requirements, kilometer-level wireless distance, large-capacity, and high-spectral-efficiency systems are urgent requirements. Based on the photonics-aided system at the W band, we achieve a net rate of 47.45-Gb/s signal delivery over a 10-km single-mode fiber-28 (SMF-28) and 4.6-km wireless free-space link. The spectral efficiency of the system is 4.97 bit/s/Hz. To the best of our knowledge, this is the first demonstration at more than a 4-km wireless distance level at the W band based on a photonics-aided system, and we achieve a record product of the single-channel transmission rate and wireless distance, i.e., 47.45 Gb/s × 4.6 km = 218.27 Gb/s km. The experimental results provide a good reference value for improving the transmission distance and data rate of the radio-over-fiber (ROF) system, and will play an important role in the future beyond the 5G era.

All-Fiber Laser-Self-Mixing Interferometer With Adjustable Injection Intensity for Remote Sensing of 40 km

In this article, we propose an all-fiber self-mixing velocimeter based on a DBR fiber laser with adjustable injection intensity for the first time, and theoretically and experimentally explore the behavior of fiber lasers in detecting non-cooperative target under different injection intensities. When the ultra-strong injection level is attained, the linewidth of the DBR fiber laser will be narrowed to about 10 kHz, thus extending the coherence distance of laser tremendously. Simultaneously, the intensity noise can be also significantly suppressed. The non-cooperative target velocity measurement with 40 km single-channel transmission distance has been successfully achieved. This velocimeter is shown to be of great significance in the field of remote sensing with simple and compact configuration, and adjustable dynamical monitoring range.

1.71 Tb/s Single-Channel and 56.51 Tb/s DWDM Transmission Over 96.5 km Field-Deployed SSMF

We report an industry leading optical dense wavelength division multiplexing (DWDM) field trial with line rates per channel <inline-formula> <tex-math notation="LaTeX">$\ge 1.66$ </tex-math></inline-formula> Tb/s using 130 GBaud dual-polarization probabilistic constellation shaping 256-ary quadrature amplitude modulation (DP-PCS256QAM) in a high capacity data center interconnect (DCI) scenario. This research trial was performed on 96.5 km of field-deployed standard single mode G.652 fiber infrastructure of Deutsche Telekom in Germany employing Erbium-doped fiber amplifier (EDFA)-only amplification. A total of 34 channels were transmitted with 150 GHz spacing for a total fiber capacity of 56.51 Tb/s and a spectral efficiency higher than 11bit/s/Hz. In the single-channel transmission scenario 1.71 Tb/s was achieved over the same link. In addition, we successfully demonstrate record net bitrates of 1.88 Tb/s in back-to-back (B2B) using 130 GBaud DP-PCS400QAM.

Comparison of Real- and Complex-Valued NN Equalizers for Photonics-Aided 90-Gbps D-band PAM-4 Coherent Detection

5G defines below 100 GHz as the millimeter-wave bands, whereas 100 GHz - 3 THz is categorized as THz band in 6G. Deep leraning (DL) is expected to enable a significant paradigm shift in 6G wireless networks. In this paper, D-band 90-Gbps single channel PAM-4 signal generation and transmission over 10-km SMF and 3-m wireless link at 140-GHz can be achieved. A novel complex-valued neural network (CVNN) equalizer using &#x2018;&Copf;ReLU&#x2019; activation function to directly recover PAM-4 signals from received noised signals is demonstrated. There are three DSP options in the experiment. In <i>Opt</i>.1, firstly conducted cascaded multi-modulus algorithm (CMMA) pre-equalization (pre-EQ) at transmitter, then processed via frequency offset estimation (FOE), carrier phase recovery (CPR) and finally real-valued neural network (RVNN) equalization at receiver. Here, the RVNN equalizers include DNN with a softmax output layer, two-step joint-DNN equalizer and LSTM. The experimental results show that LSTM-based equalizer outperforms the other real NN-based equalizers by average 0.5 to 1.5 dB at BER of 10^&#x2212;3 magnitude. Differently from <i>Opt</i>. 1, real-valued CMMA pre-EQ at transmitter is unexpected for CVNN in the other two options. In <i>Opt</i>. 2, we only combine down-conversion and CVNN regarded as &#x2018;pure data-driven&#x2019; training at receiver. This pure data-driven CVNN equalizer improves BER a lot and also has a larger computation burden, especially BER is as low as 1 &#x00D7; 10^&#x2212;4 with <i>n</i>₀ &#x003D; 571 and <i>n</i>₁ &#x003D; 200 training cells and the time complexity reaches 350000 in one iteration. Thanks to the aid of traditional mathematical-oriented models including FOE and CPR, the computation burden of CVNN in <i>Opt</i>. 3 is released significantly. Furthermore, we compare the performance of CVNN and RVNN in terms of BER decision accuracy, time complexity and receiver sensitivity. Followed by the same DSP with the same complexity, the comparison result between DNN and CVNN in the same structure of [371-260-1] with 11000 samples and 300 epochs shows that CVNN performs better due to its reservation of phase information. Therefore, we believe that the joint use of model-based, e.g., FOE, CPR steps and complex DL-based techniques has a potential for the future 6G wireless physical layer algorithms.

Analyses of dispersive effects and the distributed capacitance in the time and frequency domains of activated carbon nanofiber electrodes as symmetric supercapacitors

A novel and scalable method is reported to produce flexible and freestanding fabrics composed of high surface area activated carbon nanofibers (aCNF) for applications in supercapacitors. The electrochemical behavior of a symmetric supercapacitor using the aCNF electrodes and the operando Raman spectra study accomplished under polarization conditions are reported. The evolution of Raman spectra during polarization supported the aCNF stability and suggested the insertion of the HSO4− ions in carbon micropores. These findings evidenced a new symmetry at the aCNF/electrolyte interface, where electronic and ionic charges accumulate. The distributed capacitance in the time domain was studied by numeric differentiation of galvanostatic charge-discharge findings. The impedance behavior of the solid and liquid phases composing the aCNF/solution interface was modeled using a macro homogeneous description of two closely mixed phases represented by a single-channel transmission line incorporating the anomalous transport of the ionic charges in the disordered structure of aCNF. Electrochemical findings revealed outstanding charge-storage properties in neutral aqueous electrolyte resulting in long lifespan, low equivalent series resistance (12 mΩ g), high coulombic efficiency (∼99.8 %), a maximum distributed capacitance of 82 F g−1 (0.25 A g−1-1.1 V), maximum specific energy and power of 2.98 W h kg−1 and 72,672 W kg−1, respectively.

High Spectral Efficiency WDM Transmission Based on Hybrid Probabilistically and Geometrically Shaped 256QAM

We experimentally demonstrated a 10-channel 50-GHz-grid wavelength division multiplexing (WDM) signal transmission over 400-km standard single-mode fiber (SSMF) with the net bit rate of 614.4 Gbps/carrier and the spectral efficiency (SE) of 12.288 b/s/Hz, which is the highest SE for 256QAM to the best of our knowledge. Thanks to the joint pre-equalization and Volterra nonlinear equalization (VNLE), 49-Gbaud polarization division multiplexing (PDM) 256-ary quadrature amplitude modulation (256QAM) signal transmission with a novel constellation using probabilistic shaping (PS) and geometric shaping (GS) techniques is realized, considering the 0.828-normalized generalized mutual information (NGMI) low-density parity-check (LDPC) threshold with 25% overhead. Compared with the regular 256QAM at the same net bit rate, the designed hybrid PS/GS 256QAM at the expense of 1-Gbaud increase in the symbol rate obtains 1.7-dB and 1.5-dB shaping gain in single-channel case and WDM case, respectively. Meanwhile, an improvement of at least 0.6-dB in optical signal to noise ratio (OSNR) over the hybrid PS/GS 256QAM is achieved in comparison with PS-256QAM for both single-channel and WDM transmission.