- 标题
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- 实验方案
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Laser Phase Noise Tolerance of Uniform and Probabilistically-shaped QAM Signals for High Spectral Efficiency Systems
摘要： We numerically and experimentally investigate the laser phase noise tolerance of probabilistically shaped (PS) and uniformly shaped (US) quadrature amplitude modulation (QAM) signals. In the simulations, we compare PS-64QAM to US-16QAM, PS-256QAM to US-64QAM, and PS-1024QAM to US-256QAM under the same information rate (IR). We confirm that a sufficient shaping gain is observed with narrow linewidth lasers, whereas degradation of the shaping gain is clearly observed when large phase noise and high order modulation formats are assumed. We also evaluate the pilot ratio dependency of the required optical signal-to-noise ratio at the forward error correction limit and the achievable information rate. Additionally, we compare the performance of two types of CPR updating schemes: updating phase estimation at only the pilot symbol or at all symbols.
关键词： Digital coherent,high order quadrature amplitude modulation,laser phase noise,probabilistic shaping,optical fiber communication
更新于2025-09-16 10:30:52
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Optical Scheme of Obtaining Highest Transmission Factor in Case of KDP Based Electro-Optic Crystal by the Adjustment of Suitable Biasing Voltage and Number of Feedback Passing
摘要： The electro-optic effect becomes prominent when an electric field is applied across the optic axis of a dielectric material inducing the changes in refractive indices of the medium. Kerr and Pockels cells are massively used as optical switches because of their nonlinear electro-optic character. Potassium di-hydrogen Phosphate (KDP) crystal is a very good electro-optic Pockels material as well as has a good switching behavior in optical and opto-electronic domain. The principle of this electro optic effect can be successfully used to develop optical switch based information processing devices. Transmission co- efficient of the polarized light beam have been modulated in a new way by introducing a multi passing scheme across a electro-optic material. Here transmission co-efficient plays a vital role to examine how much output intensity changes for developing feedback one by one in ascending order. In this paper a novel study for the sizable increase of transmission co-efficient of a KDP crystal for a fixed biasing voltage is reported adopting proper feedback mechanism of light. This paper we also observe an theoretical basis for achieving unit transmission coefficient which minimum amount of voltage require for adopting comparatively many large number of feedback.
关键词： electro-optic effect,amplitude modulation,KDP crystal,transmission co-efficient
更新于2025-09-11 14:15:04
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Blind Carrier Frequency Offset Estimation in Coherent Optical Communication Systems with Probabilistically Shaped M-QAM
摘要： We find that the conventional 4th power and circular harmonic expansion (CHE) algorithms, which are originally devised for blind frequency offset estimation (FOE) in the uniform M-quadrature amplitude modulation (MQAM) systems, cannot work properly for probabilistically shaped (PS)-MQAM under moderate or strong shaping. To solve this issue, two novel blind FOE algorithms, namely the radius directed (RD)-4th power algorithm and the generalized circular harmonic expansion (GCHE) algorithm, are proposed. The former one adopts QPSK-selection based on a radius threshold optimized for a specific constellation entropy; while the later one conducts maximum likelihood (ML) estimation with a theoretically derived nonlinear radius transfer function in the GCHE.
关键词： Carrier frequency offset estimation,coherent optical communication,probabilistically shaped (PS) M-quadrature amplitude modulation (MQAM)
更新于2025-09-11 14:15:04
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Differential pulse-amplitude modulation signalling for free-space optical communications
摘要： To improve the bandwidth efficiency of free-space optical systems and at the same time to reduce the impact of the background noise, a differential M-ary pulse-amplitude modulation (M-PAM) signalling scheme that uses two laser transmitters is proposed. The authors first consider the condition that the receiver perfectly knows the instantaneous channel coefficient and compare the performance of the proposed differential PAM with the conventional PAM signalling and show the improved performance when the background noise level is relatively high. Second, the practical situation where the receiver has to estimate the channel for signal detection is considered. The authors propose an estimation scheme based on the characteristics of the differential PAM signalling while requiring no pilot symbol transmission. The proposed data-aided channel estimation is performed on a sequence of received PAM symbols. The authors also show that for a sufficiently large observation window, the proposed estimation method allows achieving a performance close to the perfect channel knowledge.
关键词： bandwidth efficiency,channel estimation,background noise,free-space optical communications,differential M-ary pulse-amplitude modulation
更新于2025-09-11 14:15:04
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - SVM Classification Comparison for QAM Modulated Optical Interconnection
摘要： We experimentally investigated four SVM multi-classification methods for machine learning nonlinearity mitigation. The comparison results indicate very close BER performance with significant improvement. Meanwhile, the SVM multi-classifier based on the in-phase and quadrature component has the lowest complexity.
关键词： support vector machine,optical interconnection,quadrature amplitude modulation
更新于2025-09-11 14:15:04
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Four-PAM Modulation of Ambient FM Backscattering for Spectrally Efficient Low-Power Applications
摘要： Ambient backscatter uses radio frequency signals available in the environment (e.g., radio broadcasting, television, or mobile telephony) to transmit data effectively leading to significant energy and cost efficiency increase. This paper presents a novel wireless tag, which for the first time utilizes 4-pulse amplitude modulation technique to modulate the ambient backscattered FM signals in order to send data to a nearby low-cost software defined radio reader. The tag is based on an RF front-end that uses a single transistor controlled by an ultralow-power microcontroller. The microcontroller includes an analog-to-digital converter for sensing and a digital-to-analog converter for RF front-end control. A proof-of-concept prototype is demonstrated in an indoor environment with the low bit rate of 345 b/s and power consumption 27 μW. It operated using a real FM station at 34.5 km away and the tag-to-reader distance was tested at 1 m. The value of energy spent in this modulator was 78.2 nJ/bit at 345 b/s and 27.7 nJ/bit at 10.2 kb/s.
关键词： Internet-of-Things (IoT),backscatter communication,Ambient backscattering,software-defined radio (SDR),pulse amplitude modulation (PAM),FM modulation,radio frequency identification (RFID) sensors
更新于2025-09-10 09:29:36
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Low-Resolution Digital Pre-Compensation for High Speed Optical Links based on Dynamic Digital-to-Analog Conversion
摘要： Digital pre-compensation (DPC) is considered a promising technique for high throughput optical communication systems. The digital signal processing (DSP) at the transmitter relies on the availability of high-speed and high-resolution digital-to-analog devices to generate complex analog waveforms. However, one major challenge in current DACs technology is the limited resolution, which introduces dominant quantization distortions when extensive DSP is implemented. In this paper a dynamic quantization (DQ) approach is suggested, termed as digital-resolution-enhancer (DRE), which mitigates the quantization distortion effects. This approach is based on the underlying assumption that quantization is a non-linear deterministic operation, implying that its impact on transmission can be anticipated and minimized. The proposed method is theoretically and experimentally investigated with special focus on linear pre-compensation for bandwidth limited systems. Simulation results demonstrate that the DRE improves the signal-to-quantization-noise-ratio (SQNR) by up to 8dB. Thus, the DPC can be applied with reduced number of DAC’s bits. Conversely, the DRE can enable the use of more complex DPC schemes using the same DACs hardware, and consequently achieve extended reaches and higher transmission rates. Numerical simulations are verified by a set of extensive lab experiments. For electrical back-to-back (BTB) transmission, with an analog bandwidth of 13 GHz, 45 Gbaud QAM-64 is demonstrated using only 4 bits DACs. For optical BTB setup with an overall optoelectronic bandwidth of less than 5 GHz, 32 Gbaud QAM-4 is demonstrated using only 2.6 bits DACs.
关键词： Digital signal processing,digital-to-analog converters,quadrature amplitude modulation,coherent detection,digital pre-compensation
更新于2025-09-10 09:29:36
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Performance Analysis and Constellation Optimization of Star-QAM-Aided Differential Faster-than-Nyquist Signaling
摘要： In this letter, motivated by the recent differential faster-than-Nyquist (DFTN) signaling concept, we propose an improved 16-point double-ring star quadrature amplitude modulation (QAM)-aided DFTN signaling transmission, which allows us to attain a higher bandwidth ef?ciency as well as a simple receiver based on noncoherent detection. We derive an analytical error-rate bound for the proposed star-QAM DFTN signaling in an uncoded scenario. The derived bound is used for optimizing the star-QAM constellation for our DFTN signaling in terms of error-rate performance in an uncoded scenario. Our simulation results demonstrate that the proposed star-QAM DFTN scheme outperforms its conventional phase-shift-keying-based DFTN counterpart.
关键词： noncoherent detection,bandwidth efficiency,Differential faster-than-Nyquist (DFTN) signaling,star quadrature amplitude modulation (QAM),error-rate performance
更新于2025-09-10 09:29:36
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Low-complexity Blind Carrier Phase Recovery for C-mQAM Coherent Systems
摘要： A novel carrier phase recovery algorithm is proposed for coherent optical systems with circular multilevel quadrature amplitude modulation (C-mQAM). After amplitude segmentation and phase rotation, the particular distribution of the constellation points in a C-mQAM signal is exploited to construct a special cost function to provide a rough estimate of phase noise. The cost function can be replaced with a simple cosine function, and only two or three test phases are required for the calculation of its parameters. The performances of different cost functions are compared and simulation results show that the cost function can be chosen with the high phase noise tolerance and low computational complexity. Maximum-likelihood (ML) phase noise estimation algorithm is combined with the proposed algorithm to mitigate residual phase noise. Compared to the single-stage blind phase search (BPS) and n-phase shift keying (n-PSK) partitioning algorithms, the numerical results demonstrate that the proposed two-stage algorithm shares similar phase noise tolerance and offers a lower computational complexity for a 28GBaud back-to-back coherent optical QAM transmission system.
关键词： circular multilevel quadrature amplitude modulation (C-mQAM),coherent optical communication,blind phase recovery (BPR),computational complexity (CC)
更新于2025-09-09 09:28:46
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Real-Time Optronic Beamformer on Receive in Phased Array Radar
摘要： The development of phased array radar beamforming technologies has led to an ever-increasing demand for large antenna arrays and multiple beams. However, real-time processing becomes a difficulty for large array or multibeam beamforming due to huge data amount. To overcome the electronic mass data processing speed limitations, optronic technique is developed for beamforming in this letter. We present a novel real-time multibeam optronic beamforming (OPBF) system specially designed for large phased array. In our system design, beamforming is formulated as a finite-impulse response filtering process, of which radar raw data and weighting coefficients are encoded onto the laser beam by joint amplitude and phase control (JAPC) modules and two-dimension adding is performed by a lens. Ultrafast optical calculation and the proposed high-speed JAPC module make the system powerful for real-time processing. The proposed system has good expansibility in data capacity, which makes it applicable to massive data processing. What’s more, a practical low-power optronic beamformer is demonstrated. Measured results show that the presented OPBF system is able to accurately synthesize flexible and controllable multibeams and performs well in channel equalization.
关键词： phase modulation,digital micromirror device (DMD),optronic processing,Amplitude modulation,real-time processing,beamforming
更新于2025-09-04 15:30:14