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A Multimode Neuromorphic Vision Sensor With Improved Brightness Measurement Performance by pulse coding Method

IEEE INTERNET OF THINGS JOURNAL 2024年第4期11卷 6266-6277页

作者： Ding, Zewei Wu, Qijuan Wang, Mingyu Liu, Jingjing Zeng, Xiaoyang Li, Wenhong Huang, Wei Liu, Zhi Zhang, Xiao-Ping Fudan Univ State Key Lab ASIC & Syst Shanghai 200433 Peoples R China Shandong Univ Sch Informat Sci & Engn Qingdao 266237 Peoples R China Ryerson Univ Dept Elect Comp & Biomed Engn Toronto ON M5B 2K3 Canada

This article proposes a multimode neuromorphic event-frame integrated vision sensor that enables event detection (ED) with simultaneous brightness measurement based on the pulse width modulation mechanism. The logarithmic voltage is directly taken as intensity information. Brightness measurement involves in-pixel voltage-to-pulse conversion and out-pixel pulse coding. The maximum event bandwidth is improved to 366 Meps by pipelining the time-prior arbiter along with the address-events grouping circuit. A wide intensity dynamic range of 105 dB can theoretically be achieved through logarithmic photoelectric conversion and pulse coding. Our sensor supports a 128x64 frame-like image with an improved signal-to-noise ratio of 49 dB. The experimental results indicate that the log sensitivity of the optimized logarithmic photoreceptor was measured as 164 mV/dec. The equivalent frame rate for both event and intensity reaches kilo fps, making it a promising candidate in high-speed wireless sensing applications.

关键词： Equivalent frame rate event detection (ED) intensity measurement (IM) pulse coding wide dynamic range

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Enhanced Underwater LiDAR via Dual-Comb Interferometer and pulse coding

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2024年 62卷 1页

作者： Zhao, Haihan Shi, Haonan Zhu, Zhiwei Qian, Zhiwen Xu, Xinyang Zhai, Jingsheng Chen, Xue Li, Xiaobo Tianjin Univ Sch Marine Sci & Technol Tianjin 300072 Peoples R China Chinese Univ Hong Kong Dept Mech & Automat Engn Hong Kong Peoples R China No 53 Res Inst China Elect Technol Grp Corp Natl Key Lab Electromagnet Space Secur Tianjin 300054 Peoples R China Tianjin Univ Law Sch Tianjin Peoples R China

Underwater distance/length sensing serves a fundamental function and plays a crucial role in a wide range of applications, including topography and geomorphology in remote sensing. Advanced light detection and ranging (LiDAR) systems and algorithms are significant for underwater tasks, such as objection positing, target searching, and rescuing. In this article, we propose a dual-comb interferometer-based LiDAR system to achieve accurate underwater absolute distance measurement. Specifically, the system applies a well-designed pulse coding strategy that significantly expands the nonambiguity range (NAR) for underwater distance measurements, allowing for precise long-distance measurements in a single attempt. Besides, we introduce a correction process to handle the water group refractive index problem. Compared with reference values, experimental results show that the range fluctuation is within +/- 15 m at a 12 m measurement range, and the Allan deviation is 0.62 mu m over an average time of 100 s. In practice, this LiDAR solution with a micrometer-level precision is promising for various applications in ocean engineering.

关键词： pulse measurements Interference Distance measurement Optical interferometry Encoding Measurement by laser beam Laser radar Absolute distance dual-comb interferometer laser pulse remote sensing micrometer-level precision pulse coding underwater light detection and ranging (LiDAR)

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pulse coding in Distributed Optical Fiber Vibration Sensor: A Review

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IEEE SENSORS JOURNAL 2021年第20期21卷 22371-22387页

作者： Li, Peihong Wang, Yu Wang, Pengfei Bai, Qing Gao, Yan Zhang, Hongjuan Jin, Baoquan Taiyuan Univ Technol Coll Phys & Optoelect Key Lab Adv Transducers & Intelligent Control Sys Minist Educ & Shanxi Prov Taiyuan 030024 Peoples R China Taiyuan Univ Technol Coll Elect & Power Engn Taiyuan 030024 Shanxi Peoples R China State Key Lab Coal & CBM Comining Jincheng 048000 Peoples R China

Distributed optical fiber vibration sensor (DOFVS) is suitable for remote monitoring of vibration signals generated by external perturbations. In order to improve the sensing performance, various pulse coding techniques are applied in DOFVS, which have attracted an increasing amount of research attention. In this paper, recent advances of pulse coding methods used in DOFVS are reviewed, from pulse compression, including linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM), pulse coding modulation based on the linear combination and correlation operation, such as Simplex code, Golay code and random code, as well as pulse sequence modulation (PSM), such as phase-shift pulses, differential frequency pulses, etc. Characteristics, working principles and the latest research results of pulse coding methods are discussed. Furthermore, some application progresses of pulse coding for performance enhancement in DOFVS are also introduced. By combining these technologies, the sensing performance could be improved in aspects of sensing distance, spatial resolution (SR), and frequency response, which show considerable potential applications in perimeter security, oil and gas monitoring, pipeline leakage, and structural health monitoring.

关键词： Vibrations Sensors Optical fiber sensors Frequency modulation Encoding Optical fibers Refractive index Distributed optical fiber vibration sensor performance improvement pulse coding pulse compression pulse sequence modulation

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Notch Frequency Generation Methods in Noise Spread Spectrum for pulse coding Switching DC-DC Converter 13

Notch Frequency Generation Methods in Noise Spread Spectrum ...

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13th Latin America Symposium on Circuits and System (LASCAS)

作者： Dong, Gui-Yi Katayama, Shogo Sun, Yifei Kobori, Yasunori Kuwana, Anna Kobayashi, Haruo Gunma Univ Div Elect & Informat Kiryu Gumma Japan Shenyang Univ Chem Technol Sch Elect & Informat Engn Shenyang Peoples R China

ISBN: (纸本)9781665420082

This paper introduces two pulse coding control methods for generating notch frequency automatically in noise spread spectrum for switching DC-DC converters;these are based on our previously proposed method. Our two methods here generate the notch frequency F-n automatically according to the received frequency F-in. The first one is a constant frequency PWM-controlled buck DC-DC converter where the clock frequency and coding pulse width are automatically set according to the frequency of the received signal to generate notch characteristics. The second one is a pulse frequency modulation (PFM) pulse coding DC-DC converter which generates a composite notch characteristic where both the constant pulse width and the periodic modulation coding pulse width are automatically matched with input frequency F-in. Our simulation results show that the transient response is fast and the output voltage overshoot is small.

关键词： switching converter spread spectrum EMI reduction notch frequency pulse coding PWM PFM

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pulse coding Controlled Switching Converter that Generates Notch Frequency to Suit Noise Spectrum

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IEICE TRANSACTIONS ON COMMUNICATIONS 2020年第11期E103B卷 1331-1340页

作者： Sun, Yifei Kobori, Yasunori Kuwana, Anna Kobayashi, Haruo Gunma Univ Div Elect & Informat Kiryu Gumma 3768515 Japan

This paper proposes a noise reduction technology for a specific frequency band that uses the pulse coding controlled method to automatically set the notch frequency in DC-DC switching converters of communication equipment. For reducing the power levels at the frequency and its harmonics in the switching converter, we often use a frequency-modulated clock. This paper investigates a technology that prevents modulated clock frequency noise from spreading into protected frequency bands;this proposed noise reduction technology does not distribute the switching noise into some specified frequency bands. The notch in the spectrum of the switching pulses is created by the pulse Width coding (PWC) method. In communication devices, the noise in the receiving signal band must be as small as possible. The notch frequency is automatically set to the frequency of the received signal by adjusting the clock frequency using the equation F-n = (P + 0.5)F-ck. Here F-n is the notch frequency, F-ck is the clock frequency, and P is a positive integer that determines the noise spectrum location. Therefore, simply be setting the notch frequency to the received signal frequency can suppress the noise present. We confirm with simulations that the proposed technique is effective for noise reduction and notch generation. Also we implement a method of automatic switching between two receiving channels. The conversion voltage ratio in the pulse width coding method switching converter is analyzed and full automatic notch frequency generation is realized. Experiments on a prototype circuit confirm notch frequency generation.

关键词： switching converter noise spectrum notch frequency pulse coding

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Theoretical and experimental study on reducing coherent Rayleigh noise of Rayleigh scattering distributed optical fiber sensing system using PSK pulse coding

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OPTICAL FIBER TECHNOLOGY 2021年 64卷 102539-102539页

作者： Li, Yongqian Wang, Lei Zhang, Lixin Fan, Haijun Liu, Yanrui North China Elect Power Univ Dept Elect & Commun Engn Baoding 071003 Peoples R China

A new method of reducing coherent Rayleigh noise (CRN) by using Phase Shift Keying (PSK) pulse coding is characterized and demonstrated theoretically and experimentally. A phase modulator driven by an arbitrary function generator is employed to encode pulses with PSK modulation, the traces obtained by coded pulses with different coding orders are superposed and averaged to reduce CRN. The experimental results validate that our method can realize about 0.49 dB amplitude fluctuation in 10 km optical fiber with 10 m spatial resolution when the coding length is 6bit. Compared with the method of FSAV, the method presented in this paper has almost the same CRN reduction effect at different spatial resolutions. From a practical point of view, the proposed method may be attractive in reducing the CRN for the Rayleigh scattering distributed optical fiber sensing system especially when the high spatial resolution and high accuracy are the main concerns.

关键词： Coherent Rayleigh noise Frequency shift averaging Phase shift keying pulse coding Multi-coding sequence

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pulse Intensity coding Phase-Sensitive OTDR With Mismatched Filtering

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2024年第3期16卷 1页

作者： Xie, Yaning Xu, Tuanwei Cao, Kai Zhang, Jing Deng, Dimin Li, Fang Chinese Acad Sci Inst Semicond State Key Labs Transducer Technol Beijing Peoples R China Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China Univ Chinese Acad Sci Coll Mat Sci & Optoelect Technol Beijing 100049 Peoples R China

Optical pulse coding phase-sensitive optical time-domain reflectometry (phi-OTDR) sends a series of pulses into the sensing fiber to enhance signal-to-noise ratio (SNR). And the spatial resolution is determined by the subpulse duration. The current challenges in optical pulse coding phi-OTDR include long measurement time, complex coding design, and intricate modulation process. In this paper, pulse intensity coding and mismatched filtering is introduced, which could reach the theoretical measurement time determined by the fiber length. Additionally, it also simplifies coding design and modulation process. In order to obtain satisfactory decoding results, the least-squares criterion is used to design the mismatched filter. Experimental result demonstrates a 6.6 dB improvement in the SNR of the demodulated signal using a 10-bit coding pulse.

关键词： pulse coding mismatched filtering least-squares criterion phase-sensitive optical time-domain reflectometry

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Vector Brillouin optical time-domain analysis with Raman amplification and optical pulse coding 6

Vector Brillouin optical time-domain analysis with Raman amp...

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Conference on Photonic Instrumentation Engineering VI

作者： Lu, Ping Lalam, Nageswara Liu, Bo Buric, Michael Ohodnicki, Paul R. Leidos 626 Cochrans Mill Rd Pittsburgh PA 15236 USA Natl Energy Technol Lab 626 Cochrans Mill Rd Pittsburgh PA 15236 USA West Virginia Univ Corp Res 3610 Collins Ferry Rd Morgantown WV 26505 USA Natl Energy Technol Lab 3610 Collins Ferry Rd Morgantown WV 26505 USA Carnegie Mellon Univ Dept Mat Sci & Engn 5000 Forbes Ave Pittsburgh PA 15213 USA Carnegie Mellon Univ Dept Engn & Publ Policy 5000 Forbes Ave Pittsburgh PA 15213 USA

ISBN: (纸本)9781510624931

This paper proposes a new vector Brillouin optical time-domain analysis optical fiber sensor with large dynamic range and high signal-to-noise ratio that combines distributed Raman amplification with optical pulse coding. The optimized Raman pumping configurations are numerically simulated by solving the coupled differential equations of the hybrid Brillouin-Raman process, and experimentally investigated with respect to the Brillouin pump pulse. A vector network analyzer is adopted to extract both the amplitude and phase spectrograms of the Brillouin interaction in a distributed fashion which effectively lessens the impact of the Raman relative intensity noise transfer problem and achieve high accuracy measurement over a long sensing distance. Advanced pulse coding is further introduced to increase the sensing range under high spatial resolution. Initial experimental results of phase and amplitude from a custom built BOTDA system is presented. Compared to typically tens of kilometers measurement distance of conventional Brillouin optical time-domain analysis techniques, the proposed optical fiber Brillouin sensor has the potential to greatly enhances sensing range up to one hundred kilometers or greater, providing distributed temperature and strain monitoring of high spatial resolution and high sensing resolution in structures such as oil and natural gas pipelines.

关键词： Brillouin optical time domain analysis Raman amplification pulse coding

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Interference-Fading-Suppressed pulse-coding Φ-OTDR Using Spectrum Extraction and Rotated-Vector-Sum Method

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2021年第6期13卷 1页

作者： Cui, Kexin Liu, Fei Wang, Kuiru Liu, Xiaojun Yuan, Jinhui Yan, Binbin Zhou, Xian Beijing Univ Posts & Telecommun State Key Lab Informat Photon & Opt Commun Beijing 100876 Peoples R China Univ Sci & Technol Beijing Res Ctr Convergence Networks & Ubiquitous Serv Beijing 100083 Peoples R China

With phase-sensitive optical time-domain reflectometry (Phi-OTDR), an optic fiber can be used as a distributed vibration sensor to perceive the external disturbance along the fiber through the phase variation of the Rayleigh backscatter light. However, due to the inevitable interference fading phenomenon, the signal-to-noise ratio (SNR) of Rayleigh backscatter light at certain points is insufficient, thus affecting the fidelity of vibration sensing. In this paper, we propose the spectrum extraction and the rotated-vector-sum (SERVS) method to suppress the interference fading in the pulse-intensity-coding Phi-OTDR, which applies Golay complementary sequence through acousto-optic modulator (AOM). Benefited from the easier implementation, the experimental results demonstrate that the percentage of fading points can be reduced from 2.98% to 0.33% significantly and the standard deviation of differential phase is also decreased from 0.6556 rad to 0.2901 rad. Also the minimum level of averaged power spectral density (PSD) of the differential phase at whole locations along the fiber is reduced about 6 dB/Hz effectively. For the demodulated disturbance signal, no influence on the SNR is observed thus it maintains a SNR improvement of 8.6 dB compared to the traditional single pulse Phi-OTDR system, achieving a noise floor of 2.38 pe/root Hz.

关键词： Distributed optical fiber sensing phase-sensitive optical time-domain reflectometry pulse coding interference fading

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Distributed Acoustic Sensing Based on pulse-coding Phase-Sensitive OTDR

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IEEE INTERNET OF THINGS JOURNAL 2019年第4期6卷 6117-6124页

作者： Wang, Zinan Zhang, Bin Xiong, Ji Fu, Yun Lin, Shengtao Jiang, Jialin Chen, Yongxiang Wu, Yue Meng, Qingyang Rao, Yunjiang Univ Elect Sci & Technol China Key Lab Opt Fiber Sensing & Commun Chengdu 611731 Sichuan Peoples R China Univ Elect Sci & Technol China Ctr Informat Geosci Chengdu 611731 Sichuan Peoples R China

Phase-sensitive optical time-domain reflectometry (Phi-OTDR), which utilizes the phase information of Rayleigh scattered lightwave inside optical fiber, could turn a fiber cable into a massive sensor array for distributed acoustic sensing (DAS), i.e., an emerging infrastructure for Internet of Things. Given a certain fiber length, there are tradeoffs among the sensing bandwidth, the sensitivity, and the spatial resolution. In this paper, the concept of linearization and Golay pulse-coding for heterodyne Phi-OTDR are proposed and experimentally verified for the first time. First, we gave a full theoretical treatment on how an intensity-coded yet phase-retrieved Phi-OTDR can be built up as a fully linear system, therefore a significant enhancement of signal-to-noise ratio becomes viable and the sensing bandwidth equals the four-times averaging case. Second in the proof-of-concept experiment, submeter gauge length and nano-strain resolution were realized with 10 km sensing range, in other words, more than ten thousand sensitive sensing units were realized along the fiber. This paper makes a significant step toward high-performance DAS with orders-of-magnitude performance enhancement.

关键词： Acoustic sensors Internet of Things (IoT) optical fiber sensors pulse coding reflectometry sensor design

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