Conventional endoscopic systems provide two-dimensional images of three-dimensional structures. Real depth information is lost in these systems. Therefore, depth perception relies uniquely on monocular cues, such as occlusions, shadows or motion parallax. Three-dimensional endoscopy has been proposed to mitigate these adverse effects. Nevertheless, as it is usually based on aperture sub-sampling, the provided images suffer from a strong reduction in resolution, vulnerability to off-axis aberrations, and very low light efficiency. To face the challenge, we report here a 3D-imaging endoscopy system based on the implementation of an optical add-on that incorporates an electrically tunable lens. We demonstrate that, when attached to a standard commercial endoscope, the proposed system allows the capture of stacks of 2D images focused at different depths, with the same resolution as that provided by the endoscope alone. To demonstrate that the system is capable of capturing stacks of images with distinguishable depths, we calculated the depth map of a 3D simulated biological scenario with a standard free image-processing software. All these capabilities can be of great utility in surgery practice that require the 3D reconstruction of the surgical field.
{"title":"3D-Imaging Endoscopy Through Electronic Focusing","authors":"Ines Nohales;Angel Tolosa;Genaro Saavedra;Manuel Martinez-Corral;Nicolo Incardona","doi":"10.1109/JPHOT.2025.3646731","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3646731","url":null,"abstract":"Conventional endoscopic systems provide two-dimensional images of three-dimensional structures. Real depth information is lost in these systems. Therefore, depth perception relies uniquely on monocular cues, such as occlusions, shadows or motion parallax. Three-dimensional endoscopy has been proposed to mitigate these adverse effects. Nevertheless, as it is usually based on aperture sub-sampling, the provided images suffer from a strong reduction in resolution, vulnerability to off-axis aberrations, and very low light efficiency. To face the challenge, we report here a 3D-imaging endoscopy system based on the implementation of an optical add-on that incorporates an electrically tunable lens. We demonstrate that, when attached to a standard commercial endoscope, the proposed system allows the capture of stacks of 2D images focused at different depths, with the same resolution as that provided by the endoscope alone. To demonstrate that the system is capable of capturing stacks of images with distinguishable depths, we calculated the depth map of a 3D simulated biological scenario with a standard free image-processing software. All these capabilities can be of great utility in surgery practice that require the 3D reconstruction of the surgical field.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-7"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11309710","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.1109/JPHOT.2025.3647160
Avi Karsenty;Jeremy Belhassen;Binyamin Kusnetz
Interest in the ever-expanding field of nanoscopy techniques has greatly increased in recent years. Specifically, in-depth characterization through optical techniques capable of nano-resolution enables a deep understanding of nanostructures and their near field domain. Due to the need to detect evanescent waves and other complicated physical phenomena, the physics of these techniques are quite involved. The scanning tips used in experiments can be either apertured or apertureless, depending on the physical principle used for the measurements. Numerical analysis of proposed experimental setups can provide significant advantages to researchers, as well as complementary results to measurements. After the setup has been defined, parameters (optical, electrical, thermal, structural and dimensional) can be virtually varied and provide a preliminary forecast of the expected experimental results. It is then necessary to make assumptions about real world conditions (experimental setup) to allow the simulations to be conducted efficiently. The research reviews significant photonics/bio-photonics case studies in which physical concerns and considerations simplified the analysis and demonstrated excellent results. Moreover, this numerical practical guide can help contribute to simulations on observed phenomena/signals via the selected optical techniques, especially for chemical engineers and biological scientists looking for forecasts of sensing in dynamic and fluidic environments.
{"title":"Practical Guide of Key Physical Considerations in Numerical Analysis for Nanophotonic Experiments","authors":"Avi Karsenty;Jeremy Belhassen;Binyamin Kusnetz","doi":"10.1109/JPHOT.2025.3647160","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3647160","url":null,"abstract":"Interest in the ever-expanding field of nanoscopy techniques has greatly increased in recent years. Specifically, in-depth characterization through optical techniques capable of nano-resolution enables a deep understanding of nanostructures and their near field domain. Due to the need to detect evanescent waves and other complicated physical phenomena, the physics of these techniques are quite involved. The scanning tips used in experiments can be either apertured or apertureless, depending on the physical principle used for the measurements. Numerical analysis of proposed experimental setups can provide significant advantages to researchers, as well as complementary results to measurements. After the setup has been defined, parameters (optical, electrical, thermal, structural and dimensional) can be virtually varied and provide a preliminary forecast of the expected experimental results. It is then necessary to make assumptions about real world conditions (experimental setup) to allow the simulations to be conducted efficiently. The research reviews significant photonics/bio-photonics case studies in which physical concerns and considerations simplified the analysis and demonstrated excellent results. Moreover, this numerical practical guide can help contribute to simulations on observed phenomena/signals via the selected optical techniques, especially for chemical engineers and biological scientists looking for forecasts of sensing in dynamic and fluidic environments.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-13"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11311466","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-18DOI: 10.1109/JPHOT.2025.3645783
Kai Qiao;Yu Chang;Zefang Xu;Fei Yin;Chang Su;Liyu Liu;Tianye Liu;Chunliang Liu;Jinshou Tian;Xing Wang
Using a 1550 nm array-based single-photon LiDAR system, we demonstrated depth profiling of both static and dynamic targets up to a distance of 10 kilometers. The system comprises a 1550 nm pulsed laser source, a bistatic optical transceiver system, and a 64 × 64 InGaAs/InP Single Photon Avalanche Diode (SPAD) array camera, with an angular resolution of 20 μrad. By employing a recovery optimization algorithm guided by multi-scale time resolution, we utilized unsupervised learning methods to achieve three-dimensional (3-D) image segmentation. Subsequently, we accomplished pixel-level algorithm matching, facilitating efficient long-range 3-D imaging reconstruction with significantly reduced binary frame data. Notably, after offline processing of real point cloud data collected by our system, we obtained depth images of various targets within a 4 to 10 km range. Furthermore, we successfully captured dynamic 3-D video of targets at a frame rate exceeding 50 fps. The video was reconstructed using offline processing with an average of fewer than 2 photons returned per pixel. These depth results highlight the potential of the proposed system and reconstructed method for depth profiling, feature extraction, and target recognition of distant static and dynamic targets.
{"title":"Multi-Temporal Resolution-Guided 3-D Imaging for Array-Based Single-Photon LiDAR","authors":"Kai Qiao;Yu Chang;Zefang Xu;Fei Yin;Chang Su;Liyu Liu;Tianye Liu;Chunliang Liu;Jinshou Tian;Xing Wang","doi":"10.1109/JPHOT.2025.3645783","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3645783","url":null,"abstract":"Using a 1550 nm array-based single-photon LiDAR system, we demonstrated depth profiling of both static and dynamic targets up to a distance of 10 kilometers. The system comprises a 1550 nm pulsed laser source, a bistatic optical transceiver system, and a 64 × 64 InGaAs/InP Single Photon Avalanche Diode (SPAD) array camera, with an angular resolution of 20 μrad. By employing a recovery optimization algorithm guided by multi-scale time resolution, we utilized unsupervised learning methods to achieve three-dimensional (3-D) image segmentation. Subsequently, we accomplished pixel-level algorithm matching, facilitating efficient long-range 3-D imaging reconstruction with significantly reduced binary frame data. Notably, after offline processing of real point cloud data collected by our system, we obtained depth images of various targets within a 4 to 10 km range. Furthermore, we successfully captured dynamic 3-D video of targets at a frame rate exceeding 50 fps. The video was reconstructed using offline processing with an average of fewer than 2 photons returned per pixel. These depth results highlight the potential of the proposed system and reconstructed method for depth profiling, feature extraction, and target recognition of distant static and dynamic targets.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-8"},"PeriodicalIF":2.4,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11303763","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Continued loss reduction in hollow-core anti-resonant fibers remains an essential challenge. This work presents an ultra-low loss hollow-core anti-resonant fiber design featuring a triple-nested cladding architecture with elliptical nested elements and six auxiliary compensation tubes located between the external circular tubes. Through fiber structure optimization using the finite element method, a broad transmission bandwidth from 1380–1700 nm and a confinement loss of less than 4.63 × 10−5 dB/km is achieved. At the 1550 nm operating wavelength, the structure exhibits a minimum confinement loss of 3.29 × 10−6 dB/km, which is two orders of magnitude lower than that of double-layer circular nested structures, and surface scattering loss of approximately 1.1 × 10−2 dB/km. At a 6 cm bending radius, the bending loss is below 5.8 × 10−3 dB/km. The low-loss performance of this fiber structure has potential applications including long-haul optical fiber communications, fiber gas lasers, and distributed sensing systems.
{"title":"Ultralow Loss Hollow-Core Anti-Resonant Fiber With Elliptical Nested Elements","authors":"Pufan Zhong;Jian Tang;Zhe Zhang;Min Zhou;Min Lu;Yan He;Shuyu Xi;Yongmei Wang;Hanglin Lu;Junhui Hu","doi":"10.1109/JPHOT.2025.3645570","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3645570","url":null,"abstract":"Continued loss reduction in hollow-core anti-resonant fibers remains an essential challenge. This work presents an ultra-low loss hollow-core anti-resonant fiber design featuring a triple-nested cladding architecture with elliptical nested elements and six auxiliary compensation tubes located between the external circular tubes. Through fiber structure optimization using the finite element method, a broad transmission bandwidth from 1380–1700 nm and a confinement loss of less than 4.63 × 10<sup>−5</sup> dB/km is achieved. At the 1550 nm operating wavelength, the structure exhibits a minimum confinement loss of 3.29 × 10<sup>−6</sup> dB/km, which is two orders of magnitude lower than that of double-layer circular nested structures, and surface scattering loss of approximately 1.1 × 10<sup>−2</sup> dB/km. At a 6 cm bending radius, the bending loss is below 5.8 × 10<sup>−3</sup> dB/km. The low-loss performance of this fiber structure has potential applications including long-haul optical fiber communications, fiber gas lasers, and distributed sensing systems.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-12"},"PeriodicalIF":2.4,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11303121","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optical frequency combs generated in high-Q microresonators have unique applications, and the precise dispersion measurement is crucial to the research and design of microresonators and the generation of optical frequency combs. Here, we demonstrate a dispersion measurement method for the high-Q microresonator assisted by a lightwave component analyzer (LCA). By scanning the modulation-sideband frequencies, LCA can determine the precise frequency separation of the microresonator resonance modes on the left and right sides of the probe light. Next, the dispersion parameters of all resonance modes in the high-Q microresonator can be obtained by varying the position of the probe light. The microresonator’s dispersion parameters are also characterized using a fiber ring scheme, thereby verifying the accuracy of the LCA. The results from the two methods matched well, but the LCA method showed superior accuracy and required no additional reference frequency markers.
{"title":"High-Precision and Self-Calibrated Dispersion Measurement for High-Q Resonator","authors":"Zhen Tao;Zichun Liao;Shuai Li;Lei Liu;Liao Chen;Chi Zhang;Xinliang Zhang","doi":"10.1109/JPHOT.2025.3645243","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3645243","url":null,"abstract":"Optical frequency combs generated in high-Q microresonators have unique applications, and the precise dispersion measurement is crucial to the research and design of microresonators and the generation of optical frequency combs. Here, we demonstrate a dispersion measurement method for the high-Q microresonator assisted by a lightwave component analyzer (LCA). By scanning the modulation-sideband frequencies, LCA can determine the precise frequency separation of the microresonator resonance modes on the left and right sides of the probe light. Next, the dispersion parameters of all resonance modes in the high-Q microresonator can be obtained by varying the position of the probe light. The microresonator’s dispersion parameters are also characterized using a fiber ring scheme, thereby verifying the accuracy of the LCA. The results from the two methods matched well, but the LCA method showed superior accuracy and required no additional reference frequency markers.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-5"},"PeriodicalIF":2.4,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11303133","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1109/JPHOT.2025.3644351
Huitong Jiang;Weijing Kong;Junsen Wang;Xuanxin Chang;Yu Lu;Xiaochang Ni
Bloch Surface Waves have emerged as a promising alternative to Surface Plasmon Resonance for high-sensitivity sensing applications, owing to their low optical losses, sharp resonance dips, and tunable polarization properties. This paper explores a high-performance Bloch surface wave sensor based on an optimized one-dimensional photonic crystal structure for ultra-sensitive refractive index detection. The sensor architecture consists of a periodic stack of TiO2 and SiO2 layers with a TiO2 cap layer, designed using the transfer matrix method to operate in aqueous environments. Through numerical simulations and theoretical analyses, we systematically engineer the photonic bandgap structure to achieve enhanced field localization and low transmission loss. A Kretschmann-Raether prism coupling setup with precision angular control is employed to experimentally validate the device’s exceptional performance. The narrow resonance feature (FWHM = 0.036°) and high quality factor (Q > 1480) confirm excellent sensing capabilities, demonstrating high sensing sensitivity and an intensity-based detection resolution of 4.51 × 10−7 RIU. This work establishes BSW sensors as a next-generation platform for label-free biochemical sensing with low detection limit in the near-infrared regime.
{"title":"High Performance Bloch Surface Wave Sensing: Optimized Photonic Bandgap Structure for Low Detection Limit","authors":"Huitong Jiang;Weijing Kong;Junsen Wang;Xuanxin Chang;Yu Lu;Xiaochang Ni","doi":"10.1109/JPHOT.2025.3644351","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3644351","url":null,"abstract":"Bloch Surface Waves have emerged as a promising alternative to Surface Plasmon Resonance for high-sensitivity sensing applications, owing to their low optical losses, sharp resonance dips, and tunable polarization properties. This paper explores a high-performance Bloch surface wave sensor based on an optimized one-dimensional photonic crystal structure for ultra-sensitive refractive index detection. The sensor architecture consists of a periodic stack of TiO<sub>2</sub> and SiO<sub>2</sub> layers with a TiO<sub>2</sub> cap layer, designed using the transfer matrix method to operate in aqueous environments. Through numerical simulations and theoretical analyses, we systematically engineer the photonic bandgap structure to achieve enhanced field localization and low transmission loss. A Kretschmann-Raether prism coupling setup with precision angular control is employed to experimentally validate the device’s exceptional performance. The narrow resonance feature (FWHM = 0.036°) and high quality factor (Q > 1480) confirm excellent sensing capabilities, demonstrating high sensing sensitivity and an intensity-based detection resolution of 4.51 × 10<sup>−7</sup> RIU. This work establishes BSW sensors as a next-generation platform for label-free biochemical sensing with low detection limit in the near-infrared regime.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-6"},"PeriodicalIF":2.4,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11300772","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1109/JPHOT.2025.3644369
Jonghyun Kim;Dohyun Shin;Jinwook Burm
Frequency Modulated Continuous Wave (FMCW) LiDAR systems require the precise generation of linear chirp signals for high-resolution distance measurements. While previous studies have primarily focused on the intrinsic frequency nonlinearity of laser diode, this work considers the broader impact of the entire transmit (TX) chain on ranging accuracy. The nonlinearity of the TX system is newly classified into a static component and a residual component, each requiring independent optimization strategies. To address this, we introduce a double-resampling approach that combines pre-distortion with a post-processing algorithm. Both stages employ similar Hilbert transform-based structures, minimizing algorithmic complexity while enabling high-precision operation even with low-cost or aged TX hardware, which demonstrates strong commercial potential. Experimental results under free-space conditions show a standard deviation (STD) of 0.18 mm and an error rate (Accuracy) of 0.17% at 1 m, with a full width at half maximum (FWHM) of 6.28 mm, indicating the distance resolution.
{"title":"Double Resampling Architecture for Distance Measurement in FMCW LiDAR With Degraded Transmitter Systems","authors":"Jonghyun Kim;Dohyun Shin;Jinwook Burm","doi":"10.1109/JPHOT.2025.3644369","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3644369","url":null,"abstract":"Frequency Modulated Continuous Wave (FMCW) LiDAR systems require the precise generation of linear chirp signals for high-resolution distance measurements. While previous studies have primarily focused on the intrinsic frequency nonlinearity of laser diode, this work considers the broader impact of the entire transmit (TX) chain on ranging accuracy. The nonlinearity of the TX system is newly classified into a static component and a residual component, each requiring independent optimization strategies. To address this, we introduce a double-resampling approach that combines pre-distortion with a post-processing algorithm. Both stages employ similar Hilbert transform-based structures, minimizing algorithmic complexity while enabling high-precision operation even with low-cost or aged TX hardware, which demonstrates strong commercial potential. Experimental results under free-space conditions show a standard deviation (STD) of 0.18 mm and an error rate (Accuracy) of 0.17% at 1 m, with a full width at half maximum (FWHM) of 6.28 mm, indicating the distance resolution.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-7"},"PeriodicalIF":2.4,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11300780","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soliton fiber laser is widely regarded as the paradigm for ultrafast fiber lasers due to its simple and flexible configuration. Meanwhile, to overcome its limitation in pulse energy and bandwidth, dispersion-management and spectral filtering effects are routinely used to mitigate nonlinearity-induced instabilities through temporal and spectral stretching in the cavity. In this work, we demonstrate that, by simply introducing a large lumped attenuation in a soliton fiber laser, significant temporal and spectral stretching can be achieved despite the dominant anomalous dispersion of the fiber cavity, allowing for a stretched-pulse-like operation without using dispersion-compensation fibers and bandpass filters. In experiment, we achieved prominent pulse energy and bandwidth scaling by applying a lumped 13-dB attenuation before the gain section, which leads to 8-nm pulse bandwidth. Numerical simulations were performed to reveal the dramatic oscillation of the pulse chirp in the cavity in the all-anomalous fiber sections. This work revealed the critical role of lump attenuation in mode-locked cavity in manipulating the intra-cavity dynamics of soliton laser, and may serve as a simple and useful degree of freedom for optimization of mode-locked fiber lasers.
{"title":"Spectral-Temporal Stretching and Bandwidth Scaling in Soliton Fiber Lasers Induced by Large Lumped Attenuation","authors":"Siqi Fan;Xintong Zhang;Qi Huang;Xiaogang Tang;Xiaocong Wang;Benhai Wang;Haochen Lin;Jinxin Zhan;Xin Jiang;Wenbin He;Meng Pang","doi":"10.1109/JPHOT.2025.3643502","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3643502","url":null,"abstract":"Soliton fiber laser is widely regarded as the paradigm for ultrafast fiber lasers due to its simple and flexible configuration. Meanwhile, to overcome its limitation in pulse energy and bandwidth, dispersion-management and spectral filtering effects are routinely used to mitigate nonlinearity-induced instabilities through temporal and spectral stretching in the cavity. In this work, we demonstrate that, by simply introducing a large lumped attenuation in a soliton fiber laser, significant temporal and spectral stretching can be achieved despite the dominant anomalous dispersion of the fiber cavity, allowing for a stretched-pulse-like operation without using dispersion-compensation fibers and bandpass filters. In experiment, we achieved prominent pulse energy and bandwidth scaling by applying a lumped 13-dB attenuation before the gain section, which leads to 8-nm pulse bandwidth. Numerical simulations were performed to reveal the dramatic oscillation of the pulse chirp in the cavity in the all-anomalous fiber sections. This work revealed the critical role of lump attenuation in mode-locked cavity in manipulating the intra-cavity dynamics of soliton laser, and may serve as a simple and useful degree of freedom for optimization of mode-locked fiber lasers.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-5"},"PeriodicalIF":2.4,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11298501","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Coarse-to-fine partitioning (CFP) algorithm is proposed for angle-of-arrival (AoA) estimation with a controllable liquid crystal display (LCD) in front of a photodetector (PD). By electrically switching each pixel of the LCD in transparent or opaque, the position of the aperture through which the incident light passes is controlled to estimate the AoA of the incident light to the PD. The size of the aperture needs to be a certain size to maintain the accuracy of the AoA estimation, which consists of a region of several pixels. In the conventional algorithm, with a fixed size of the aperture equal to the size of resolution unit, the entire surface of the LCD was exhaustively searched horizontally and vertically. In our CFP algorithm, the entire surface is partitioned into two or three equal-area regions, and the intensities observed at the PD when pixels consisting of each of such regions are alternately switched to transparent mode are compared. Among them, the region with the highest intensity observed is chosen as the next candidate region through which the incident light passes. This process is iteratively applied, partitioning the candidate region from coarse to fine, until the region reaches the resolution size. For the LCD consisting of 2560 × 1440 pixels with the resolution unit size of 10 × 10 pixels, to estimate the AoA, our CFP algorithm requires 30 searches while the conventional algorithm requires 400 searches. Experimental results show that although intensity measurements are repeated fifteen times for each search to stabilize the intensity measurement values in both of the conventional algorithm and our CFP algorithm, our algorithm estimates it with the error less than one degree. Furthermore, by adding another PD into the system, from the AoA estimation for the two PDs with our CFP algorithm, the distance estimation to the light source from 200 mm to 900 mm is experimentally shown with a relative error of 4.5$%$.
{"title":"Coarse-to-Fine Partitioning Algorithm for Angle-of-Arrival Estimation in Visible Light Positioning Using Liquid Crystal Display","authors":"Ryunosuke Fukuda;Koji Kamakura;Masayuki Kinoshita;Takaya Yamazato","doi":"10.1109/JPHOT.2025.3643362","DOIUrl":"https://doi.org/10.1109/JPHOT.2025.3643362","url":null,"abstract":"Coarse-to-fine partitioning (CFP) algorithm is proposed for angle-of-arrival (AoA) estimation with a controllable liquid crystal display (LCD) in front of a photodetector (PD). By electrically switching each pixel of the LCD in transparent or opaque, the position of the aperture through which the incident light passes is controlled to estimate the AoA of the incident light to the PD. The size of the aperture needs to be a certain size to maintain the accuracy of the AoA estimation, which consists of a region of several pixels. In the conventional algorithm, with a fixed size of the aperture equal to the size of resolution unit, the entire surface of the LCD was exhaustively searched horizontally and vertically. In our CFP algorithm, the entire surface is partitioned into two or three equal-area regions, and the intensities observed at the PD when pixels consisting of each of such regions are alternately switched to transparent mode are compared. Among them, the region with the highest intensity observed is chosen as the next candidate region through which the incident light passes. This process is iteratively applied, partitioning the candidate region from coarse to fine, until the region reaches the resolution size. For the LCD consisting of 2560 × 1440 pixels with the resolution unit size of 10 × 10 pixels, to estimate the AoA, our CFP algorithm requires 30 searches while the conventional algorithm requires 400 searches. Experimental results show that although intensity measurements are repeated fifteen times for each search to stabilize the intensity measurement values in both of the conventional algorithm and our CFP algorithm, our algorithm estimates it with the error less than one degree. Furthermore, by adding another PD into the system, from the AoA estimation for the two PDs with our CFP algorithm, the distance estimation to the light source from 200 mm to 900 mm is experimentally shown with a relative error of 4.5<inline-formula><tex-math>$%$</tex-math></inline-formula>.","PeriodicalId":13204,"journal":{"name":"IEEE Photonics Journal","volume":"18 1","pages":"1-10"},"PeriodicalIF":2.4,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11298384","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145830841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-10DOI: 10.1109/JPHOT.2025.3642726
David Esteban Farfán-Guillén;André Eugênio Lazzaretti;Alexandre de Almeida Prado Pohl
Visible light communication (VLC) systems face performance limitations due to optical channel nonlinearities and pilot overhead, which constrain signal quality and spectral efficiency. This paper presents an integrated dual-stage framework combining Extreme Learning Machine (ELM) nonlinearity compensation with wavelet-based channel estimation enhancement. The proposed approach utilizes ELM processing in the time domain to mitigate optical channel distortions, followed by wavelet enhancement that exploits energy compaction properties to enhance frequency-domain channel estimates with minimal pilot overhead. Experimental validation using a 2 × 1 MISO testbed over 2-meter indoor links with 16-QAM and 64-QAM OFDM demonstrates enhanced performance, achieving BER below 10$mathrm{^{-3}}$ under varying LED-luminaire operating conditions while conventional methods fail to meet this threshold. A comparative analysis confirms that the proposed method outperforms deep neural networks and polynomial compensation techniques, while energy compaction analysis validates the channel energy concentration in wavelet coefficients. The framework demonstrates feasibility for short-range indoor VLC applications, achieving enhanced signal quality and reduced pilot overhead, thereby improving spectral efficiency.
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