| 1. |
- Pang, Xiaodan, Dr., et al.
(author)
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Free-Space Communications Enabled by Quantum Cascade Lasers
- 2021
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In: Physica Status Solidi (a) applications and materials science. - : Wiley-VCH Verlag. - 1862-6300 .- 1862-6319. ; 218:3
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Journal article (peer-reviewed)abstract
- Future generations of wireless communication systems are expected to support orders of magnitude faster data transfer with much lower latency than the currently deployed solutions. Development of wireless transceivers of higher bandwidth, low energy consumption, and small footprint becomes challenging with radio frequency (RF) electronic technologies. Photonics-assisted technologies show many advantages in generating signals of ultrabroad bandwidth at high carrier frequencies in the millimeter-wave, terahertz, and IR bands. Among these frequency options, the mid-IR band has recently attracted great interest for future wireless communication due to its intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. A promising source for mid-IR free-space communications is the semiconductor quantum cascade laser (QCL), which can be directly modulated at a high speed and facilitates monolithic integration for compact transceivers. Herein, the research and development of QCL-based free-space communications are reviewed and a recent experimental study of multi-gigabit transmission with a directly modulated mid-IR QCL and a commercial off-the-shelf IR photodetector is reported on. Up to 4 Gb s−1 transmission of two advanced modulation formats, namely, four-level pulse amplitude modulation (PAM-4) and discrete multitone (DMT) modulation, is demonstrated. © 2020 The Authors.
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| 2. |
- Puerta, Rafael, et al.
(author)
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Coherent Joint Transmission with 1024-QAM for 6G Distributed-MIMO Networks with Analog Radio-over-LWIR FSO Fronthaul Links
- 2023
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In: 2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings, ACP/POEM 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- Distributed-MIMO (D-MIMO) is a prospective solution for next-generation mobile networks to increase capacity and coverage. We experimentally validate 1024-QAM coherent joint transmissions in a two transmitter D-MIMO network including radio-over-LWIR FSO fronthaul links facilitating deployment and achieving diversity and power gains close to theoretical values.
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| 3. |
- Fan, Yuchuan, et al.
(author)
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Linear Regression vs. Deep Learning for Signal Quality Monitoring in Coherent Optical Systems
- 2022
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In: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers Inc.. - 1943-0655. ; 14:4
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Journal article (peer-reviewed)abstract
- Error vector magnitude (EVM) is a metric for assessing the quality of m-ary quadrature amplitude modulation (mQAM) signals. Recently proposed deep learning techniques, e.g., feedforward neural networks (FFNNs) -based EVM estimation scheme leverage fast signal quality monitoring in coherent optical communication systems. Such a scheme estimates EVM from amplitude histograms (AHs) of short signal sequences captured before carrier phase recovery (CPR). In this work, we explore further complexity reduction by proposing a simple linear regression (LR) -based EVM monitoring method. We systematically compare the performance of the proposed method with the FFNN-based scheme and demonstrate its capability to infer EVM from an AH when the modulation format information is known in advance. We perform both simulation and experiment to show that the LR-based EVM estimation method achieves a comparable accuracy as the FFNN-based scheme. The technique can be embedded with modulation format identification modules to provide comprehensive signal information. Therefore, this work paves the way to design a fast-learning scheme with parsimony as a future intelligent OPM enabler.
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| 4. |
- Yu, Xianbin, et al.
(author)
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Terahertz Photonics in Radar and ISAC Applications
- 2023
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In: 2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings, ACP/POEM 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- This paper reviews our recent progress on photonic terahertz radar and integrated sensing and communication (ISAC) systems in the 300GHz band with distinguished sensing performance.
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| 5. |
- Jia, Shi, et al.
(author)
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Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications
- 2022
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Journal article (peer-reviewed)abstract
- Photonic generation of Terahertz (THz) carriers displays high potential for THz communications with a large tunable range and high modulation bandwidth. While many photonics-based THz generations have recently been demonstrated with discrete bulky components, their practical applications are significantly hindered by the large footprint and high energy consumption. Herein, we present an injection-locked heterodyne source based on generic foundry-fabricated photonic integrated circuits (PIC) attached to a uni-traveling carrier photodiode generating high-purity THz carriers. The generated THz carrier is tunable within the range of 0-1.4 THz, determined by the wavelength spacing between the two monolithically integrated distributed feedback (DFB) lasers. This scheme generates and transmits a 131 Gbits(-1) net rate signal over a 10.7-m distance with -24 dBm emitted power at 0.4 THz. This monolithic dual-DFB PIC-based THz generation approach is a significant step towards fully integrated, cost-effective, and energy-efficient THz transmitters. A photonic Terahertz source based on injection-locking an integrated dual-laser chip generates and transmits a 131 Gbps THz signal over 10.7-m distance, showing great potential towards fully integrated and energy-efficient THz transmitters for 6G.
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| 6. |
- Feng, Xingxing, et al.
(author)
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Human recognition with the optoelectronic reservoir-computing-based micro-Doppler radar signal processing
- 2022
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In: Applied Optics. - : Optica Publishing Group (formerly OSA). - 1559-128X .- 2155-3165. ; 61:19, s. 5782-5789
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Journal article (peer-reviewed)abstract
- Current perception and monitoring systems, such as human recognition, are affected by several environmental factors, such as limited light intensity, weather changes, occlusion of targets, and public privacy. Human recognition using radar signals is a promising direction to overcome these defects; however, the low signal-to-noise ratio of radar signals still makes this task challenging. Therefore, it is necessary to use suitable tools that can efficiently deal with radar signals to identify targets. Reservoir computing (RC) is an efficient machine learning scheme that is easy to train and demonstrates excellent performance in processing complex time-series signals. The RC hardware implementation structure based on nonlinear nodes and delay feedback loops endows it with the potential for real-time fast signal processing. In this paper, we numerically study the performance of the optoelectronic RC composed of optical and electrical components in the task of human recognition with noisy micro-Doppler radar signals. A single-loop optoelectronic RC is employed to verify the application of RC in this field, and a parallel dual-loop optoelectronic RC scheme with a dual-polarization Mach–Zehnder modulator (DPol-MZM) is also used for performance comparison. The result is verified to be comparable with other machine learning tools, which demonstrates the ability of the optoelectronic RC in capturing gait information and dealing with noisy radar signals; it also indicates that optoelectronic RC is a powerful tool in the field of human target recognition based on micro-Doppler radar signals.
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| 7. |
- Li, Lianyi, et al.
(author)
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THz-Over-Fiber System With Orthogonal Chirp Division Multiplexing for Integrated Sensing and Communication
- 2024
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In: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 42:1, s. 176-183
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Journal article (peer-reviewed)abstract
- To achieve integrated sensing and communication (ISAC) applications with high data rates and high resolution, the terahertz-over-fiber (ToF) system has been recognized as a promising solution. However, the frequency-selective fading would deteriorate the performance of the ToF-based ISAC systems. In this work, we propose the orthogonal chirp division multiplexing (OCDM) waveform-based ToF system for high-performance ISAC applications. The system encodes data with the phase of the sub-chirps and obtains radar images by processing echoes with the zero-padded matched filtering algorithm. We experimentally demonstrate a proof-of-concept OCDM-ToF system, which simultaneously achieves a 32 Gbit/s data rate and 1.875 cm range resolution after transmission over a 10 km optical fiber and a 3.14 m wireless link at the THz band, for the first time. The experimental results indicate that the OCDM-ToF system can enhance robustness against the frequency-selective fading issue, as a benefit improving communication performance with high data rates while preserving the high sensing resolution of OFDM in the THz ISAC applications.
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| 8. |
- Lyu, Zhidong, et al.
(author)
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A Beam-Scannable Photonic THz-ISAC System Based on Risley Prisms
- 2023
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In: 2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings, ACP/POEM 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Conference paper (peer-reviewed)abstract
- We demonstrate a beam-scannable photonic terahertz-integrated sensing and communication (THz-ISAC) system using Risley prisms. 20 Gbps data rate and 1.5 cm resolution are simultaneously achieved at 300 GHz with 40 deg field of view (FoV).
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| 9. |
- Ozolins, Oskars, et al.
(author)
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High Baudrate Short-Reach Communication
- 2022
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In: Proceedings OECC/PSC 2022 - 27th OptoElectronics and Communications Conference/International Conference on Photonics in Switching and Computing 2022. - : Institute of Electrical and Electronics Engineers (IEEE). - 9784885523366
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Conference paper (peer-reviewed)abstract
- We demonstrate a 200 Gbps IM/DD link without any optical amplification using C-band externally modulated laser with 3.3 dBm of modulated output power and O-band directly modulated laser with 7.3 dBm of modulated output power.
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| 10. |
- Pang, Xiaodan, Dr., et al.
(author)
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Direct Modulation and Free-Space Transmissions of up to 6 Gbps Multilevel Signals With a 4.65-μQuantum Cascade Laser at Room Temperature
- 2022
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In: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers Inc.. - 0733-8724 .- 1558-2213. ; 40:8, s. 2370-2377
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Journal article (peer-reviewed)abstract
- A roadmap for future wireless communications is expected to exploit all transmission-suitable spectrum bands, from the microwave to the optical frequencies, to support orders of magnitude faster data transfer with much lower latency than the deployed solutions nowadays. The currently under-exploited mid-infrared (mid-IR) spectrum is an essential building block for such an envisioned all-spectra wireless communication paradigm. Free-space optical (FSO) communications in the mid-IR region have recently attracted great interest due to their intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. Future development of viable mid-IR FSO transceivers requires a semiconductor source to fulfill the high bandwidth, low energy consumption, and small footprint requirements. In this context, quantum cascade laser (QCL) appears as a promisingtechnological choice. In this work, we present an experimental demonstration of a mid-IR FSO link enabled by a 4.65-μm directly modulated (DM) QCL operating at room temperature. We achieve a transmission data rate of up to 6 Gbps over a 0.5-m link distance. This achievement is enabled by system-level characterization and optimization of transmitter and receiver power level and frequency response and assisted with advanced modulation and digital signal processing (DSP) techniques. This work pushes the QCL-based FSO technology one step closer to practical terrestrial applications, such as the fixed wireless access and the wireless mobile backhaul. Such a QCL-based solution offers a promising way towards the futuristic all-spectra wireless communication paradigm by potentially supporting the whole spectrum from the MIR to the terahertz (THz).
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