Coherent optical communication critically relies on efficient digital signal processing (DSP). We demonstrate a lite DSP scheme to reduce the transmission cost and power consumption, which is mainly realized by reducing the sampling rate and simplifying the DSP algorithm. On the one hand, the baud-rate sampling technique based on the integral circuit can reduce the amount of data processing in DSP. On the other hand, we proposed a simplified joint modified constant modulus algorithm (MCMA) and phase-dependent decision-directed least mean square (DD-LMS) algorithm for adaptive blind polarization demultiplexing and phase recovery in which the butterfly structure is no longer needed for DD-LMS. And we compare the proposed simplified algorithm with the joint traditional CMA and blind phase search and the MCMA, in terms of performance in the 80-Gbaud dual-polarization 64QAM homodyne detection system. The results show that the proposed lite DSP mechanism can effectively reduce the power consumption of DSP by sub-rate sampling and simplifying the corresponding algorithm, which provides an alternative scheme for low-power optical interconnection of data centers.
{"title":"Low power digital signal processing-lite scheme for short-reach polarization demultiplexing-64 quadrature amplitude modulation coherent optical system","authors":"Qiang Li, Wei Ji, Penghui Li, Pengcheng Liu, Fengyu Liu, Yuqian Wang, Yanjun Zhu","doi":"10.1117/1.oe.62.11.118102","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.118102","url":null,"abstract":"Coherent optical communication critically relies on efficient digital signal processing (DSP). We demonstrate a lite DSP scheme to reduce the transmission cost and power consumption, which is mainly realized by reducing the sampling rate and simplifying the DSP algorithm. On the one hand, the baud-rate sampling technique based on the integral circuit can reduce the amount of data processing in DSP. On the other hand, we proposed a simplified joint modified constant modulus algorithm (MCMA) and phase-dependent decision-directed least mean square (DD-LMS) algorithm for adaptive blind polarization demultiplexing and phase recovery in which the butterfly structure is no longer needed for DD-LMS. And we compare the proposed simplified algorithm with the joint traditional CMA and blind phase search and the MCMA, in terms of performance in the 80-Gbaud dual-polarization 64QAM homodyne detection system. The results show that the proposed lite DSP mechanism can effectively reduce the power consumption of DSP by sub-rate sampling and simplifying the corresponding algorithm, which provides an alternative scheme for low-power optical interconnection of data centers.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"21 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134901233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-10DOI: 10.1117/1.oe.62.11.115102
Roman Duplov
{"title":"Exact formula for longitudinal chromatic aberration of a thick lens through design parameters","authors":"Roman Duplov","doi":"10.1117/1.oe.62.11.115102","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.115102","url":null,"abstract":"","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"121 35","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135136446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-10DOI: 10.1117/1.oe.62.11.113101
Yuantao Wang, Yongsheng Qiu, Haiyang Jiang, Yuanyao Lu
To address the issue of high miss rates for distant small objects and the diminished system detection performance due to the influence of hazy when autonomous vehicles operate on mountain highways. We propose a framework for small object vehicle detection in hazy traffic environments (SHTDet). This framework aims to enhance small object detection for autonomous driving under hazy conditions on mountainous motorways. Specifically, to restore the clarity of hazy images, we designed an image enhancement (IE), and its parameters are predicted by a convolutional neural network [filter parameter estimation (FPE)]. In addition, to enhance the detection accuracy of small objects, we introduce a cascaded sparse query (CSQ) mechanism, which effectively utilizes high-resolution features while maintaining fast detection speed. We jointly optimize the IE and the detection network (CSQ-FCOS) in an end-to-end manner, ensuring that FPE module can learn a suitable IE. Our proposed SHTDet method is adept at adaptively handling sunny and hazy conditions. Extensive experiments demonstrate the efficacy of the SHTDet method in detecting small objects on hazy sections of mountain highways.
{"title":"Small object detection for autonomous driving under hazy conditions on mountain motorways","authors":"Yuantao Wang, Yongsheng Qiu, Haiyang Jiang, Yuanyao Lu","doi":"10.1117/1.oe.62.11.113101","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.113101","url":null,"abstract":"To address the issue of high miss rates for distant small objects and the diminished system detection performance due to the influence of hazy when autonomous vehicles operate on mountain highways. We propose a framework for small object vehicle detection in hazy traffic environments (SHTDet). This framework aims to enhance small object detection for autonomous driving under hazy conditions on mountainous motorways. Specifically, to restore the clarity of hazy images, we designed an image enhancement (IE), and its parameters are predicted by a convolutional neural network [filter parameter estimation (FPE)]. In addition, to enhance the detection accuracy of small objects, we introduce a cascaded sparse query (CSQ) mechanism, which effectively utilizes high-resolution features while maintaining fast detection speed. We jointly optimize the IE and the detection network (CSQ-FCOS) in an end-to-end manner, ensuring that FPE module can learn a suitable IE. Our proposed SHTDet method is adept at adaptively handling sunny and hazy conditions. Extensive experiments demonstrate the efficacy of the SHTDet method in detecting small objects on hazy sections of mountain highways.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"116 28","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135137950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The current field of autonomous driving has achieved superior object detection performance in good weather conditions. However, the environment sensing capability of autonomous vehicles is severely affected in rainfall traffic environments. Although deep-learning-based image derain algorithms have made significant progress, integrating them with high-level vision tasks, such as object detection, remains challenging due to the significant differences between the derain and object detection algorithms. Additionally, the accuracy of object detection in real rain traffic environments is significantly reduced due to the domain transfer problem between the training dataset and the actual rain environment. To address this domain-shifting problem, we propose an adaptive rain image enhancement object detection network for autonomous driving in adverse weather conditions (ARODNet). This network architecture consists of an image adaptive enhancement module, an image derain module, and an object detection module. The baseline detection module (CBAM-YOLOv7) is built by incorporating the YOLOv7 object detection network into a feed-forward convolutional neural network, and it includes an attention module (CBAM). We propose a domain adaptive rain image enhancement module, DRIP, for low-quality images acquired under heavy rainfall conditions. DRIP enhances low-quality images on rainy days by adaptively learning multiple preprocessing weights. To remove the effects of rain patterns and fog clouds on image detection, we introduce DRIP-enhanced images into the depth estimation derain module (DeRain) to prevent rain and fog from obscuring the objects to be detected. Finally, the multistage joint training strategy is adopted to improve the training efficiency, and the object detection is performed while the image is derained. The efficacy of the ARODNet network for object detection in rainy weather traffic environments has been demonstrated through numerous quantitative and qualitative studies.
{"title":"ARODNet: adaptive rain image enhancement object detection network for autonomous driving in adverse weather conditions","authors":"Yongsheng Qiu, Yuanyao Lu, Yuantao Wang, Haiyang Jiang","doi":"10.1117/1.oe.62.11.118101","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.118101","url":null,"abstract":"The current field of autonomous driving has achieved superior object detection performance in good weather conditions. However, the environment sensing capability of autonomous vehicles is severely affected in rainfall traffic environments. Although deep-learning-based image derain algorithms have made significant progress, integrating them with high-level vision tasks, such as object detection, remains challenging due to the significant differences between the derain and object detection algorithms. Additionally, the accuracy of object detection in real rain traffic environments is significantly reduced due to the domain transfer problem between the training dataset and the actual rain environment. To address this domain-shifting problem, we propose an adaptive rain image enhancement object detection network for autonomous driving in adverse weather conditions (ARODNet). This network architecture consists of an image adaptive enhancement module, an image derain module, and an object detection module. The baseline detection module (CBAM-YOLOv7) is built by incorporating the YOLOv7 object detection network into a feed-forward convolutional neural network, and it includes an attention module (CBAM). We propose a domain adaptive rain image enhancement module, DRIP, for low-quality images acquired under heavy rainfall conditions. DRIP enhances low-quality images on rainy days by adaptively learning multiple preprocessing weights. To remove the effects of rain patterns and fog clouds on image detection, we introduce DRIP-enhanced images into the depth estimation derain module (DeRain) to prevent rain and fog from obscuring the objects to be detected. Finally, the multistage joint training strategy is adopted to improve the training efficiency, and the object detection is performed while the image is derained. The efficacy of the ARODNet network for object detection in rainy weather traffic environments has been demonstrated through numerous quantitative and qualitative studies.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"33 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135093260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-10DOI: 10.1117/1.oe.62.11.114103
Yi Bai, Geyou Zhang, Daniel L. Lau, Bo Zhang, Bin Xu, Kai Liu
In fringe projection profilometry, applying pre-distortion to fringe patterns reduces the errors caused by projector lens distortion. However, it is important to note that discontinuous fringe patterns, such as binary fringe patterns, introduce additional errors when using pre-distortion methods. While post-undistortion methods are applicable for discontinuous fringe patterns, the computation is typically time-consuming. We propose a linear-grid model for correcting lens distortion. First, we select multiple equidistant points within the grid to calculate the linear parameters and store them as look-up tables (LUTs). Second, by rounding down the captured distorted point to the nearest integer point, we obtain the index value for LUTs. Finally, we achieve real-time compensation for distortion error through linear expressions. The experimental results show that the proposed effectively mitigates the distortion by a factor of 6 × in terms of root mean squared error. Additionally, it exhibits a computational speed of 409.50 fps, which is an improvement compared to the traditional iterative model at 39.48 fps and the scale-offset model at 264.48 fps.
{"title":"Real-time compensation of projector lens distortion using a linear-grid model in fringe projection profilometry","authors":"Yi Bai, Geyou Zhang, Daniel L. Lau, Bo Zhang, Bin Xu, Kai Liu","doi":"10.1117/1.oe.62.11.114103","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.114103","url":null,"abstract":"In fringe projection profilometry, applying pre-distortion to fringe patterns reduces the errors caused by projector lens distortion. However, it is important to note that discontinuous fringe patterns, such as binary fringe patterns, introduce additional errors when using pre-distortion methods. While post-undistortion methods are applicable for discontinuous fringe patterns, the computation is typically time-consuming. We propose a linear-grid model for correcting lens distortion. First, we select multiple equidistant points within the grid to calculate the linear parameters and store them as look-up tables (LUTs). Second, by rounding down the captured distorted point to the nearest integer point, we obtain the index value for LUTs. Finally, we achieve real-time compensation for distortion error through linear expressions. The experimental results show that the proposed effectively mitigates the distortion by a factor of 6 × in terms of root mean squared error. Additionally, it exhibits a computational speed of 409.50 fps, which is an improvement compared to the traditional iterative model at 39.48 fps and the scale-offset model at 264.48 fps.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135137567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1117/1.oe.62.11.115101
Pengwei Cui, Junchi Ma, Yue Wang, Jiashun Zhang, Jin You, Junming An, Yuanda Wu
A silica-based 90 deg optical hybrid based on a 4 × 4 multimode interference coupler with a refractive index contrast of 0.36% is designed and fabricated for coherent receiver. The measured results of this device show that the common mode rejection ratios are better than 23 dB and excess loss including a coupling loss of −0.3 dB is less than −0.9 dB in C band (1530 to 1565 nm). The phase error is less than ±4 deg. The designed low-cost 90 deg optical hybrid is promising for further improving the sensitivity of quadrature phase shift keying coherent receivers.
{"title":"Low-loss silica-based 90 deg optical hybrid in c band based on 4 × 4 multimode interference coupler for coherent receiver","authors":"Pengwei Cui, Junchi Ma, Yue Wang, Jiashun Zhang, Jin You, Junming An, Yuanda Wu","doi":"10.1117/1.oe.62.11.115101","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.115101","url":null,"abstract":"A silica-based 90 deg optical hybrid based on a 4 × 4 multimode interference coupler with a refractive index contrast of 0.36% is designed and fabricated for coherent receiver. The measured results of this device show that the common mode rejection ratios are better than 23 dB and excess loss including a coupling loss of −0.3 dB is less than −0.9 dB in C band (1530 to 1565 nm). The phase error is less than ±4 deg. The designed low-cost 90 deg optical hybrid is promising for further improving the sensitivity of quadrature phase shift keying coherent receivers.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"28 39","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135390942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1117/1.oe.63.3.031004
Dajuan Lyu, Qing Huang, Xiaokun Wu, Yanbo Nie, Minghong Yang
Owing to their advantages of anti-electromagnetic interference, chemical resistance, high sensitivity, and fast response time, optical fiber sensors (OFSs) are widely used in biomedical, environmental monitoring, and food safety fields. We introduce the classification and principles of OFSs and summarize the applications and research progress of OFSs in water quality detection (heavy metals and microorganisms) and air quality monitoring (COx, NOx, and VOCs). Meanwhile, analytical performance, reliability, and environmental adaptability of OFSs are discussed and prospected.
{"title":"Optical fiber sensors for water and air quality monitoring: a review","authors":"Dajuan Lyu, Qing Huang, Xiaokun Wu, Yanbo Nie, Minghong Yang","doi":"10.1117/1.oe.63.3.031004","DOIUrl":"https://doi.org/10.1117/1.oe.63.3.031004","url":null,"abstract":"Owing to their advantages of anti-electromagnetic interference, chemical resistance, high sensitivity, and fast response time, optical fiber sensors (OFSs) are widely used in biomedical, environmental monitoring, and food safety fields. We introduce the classification and principles of OFSs and summarize the applications and research progress of OFSs in water quality detection (heavy metals and microorganisms) and air quality monitoring (COx, NOx, and VOCs). Meanwhile, analytical performance, reliability, and environmental adaptability of OFSs are discussed and prospected.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"115 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We comprehensively investigated the influence of laser wavelength on the detection distance at different clear air turbulence (CAT) intensities, distance resolutions, and Brunt–Väisälä frequency theoretically. It is found that there exists the optimal wavelength for maximal detection distance. When the distance resolution is fixed, the detection distance of 532 nm LiDAR is further compared with the 355 and 1064 nm counterparts and is more suitable under moderate to severe CAT. Our findings break the traditional cognition that “ultraviolet wavelength LiDAR is the most suitable for CAT detection” and may promote the remote detection research of CAT.
{"title":"Influence of airborne LiDAR wavelength on the detection distance of clear air turbulence","authors":"Jing Zhao, Xiujuan Luo, Zhaohui Liu, Hui Liu, Minglai Chen, Yu Zhang, Zelin Yue","doi":"10.1117/1.oe.62.11.114101","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.114101","url":null,"abstract":"We comprehensively investigated the influence of laser wavelength on the detection distance at different clear air turbulence (CAT) intensities, distance resolutions, and Brunt–Väisälä frequency theoretically. It is found that there exists the optimal wavelength for maximal detection distance. When the distance resolution is fixed, the detection distance of 532 nm LiDAR is further compared with the 355 and 1064 nm counterparts and is more suitable under moderate to severe CAT. Our findings break the traditional cognition that “ultraviolet wavelength LiDAR is the most suitable for CAT detection” and may promote the remote detection research of CAT.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"93 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Exploiting the phase transition of vanadium dioxide (VO2), a switchable terahertz multifunctional device integrating narrowband absorption and broadband polarization switching was proposed in our study. The transformation of VO2 from insulating state to metallic state can realize different functions. When VO2 was in metal state, the metamaterial device exhibited an absorption effect exceeding 90% in the range of 1.96 to 4.06 THz, and its amplitude was tunable via changing the conductivity of VO2. Further, the modulation depth reached 171%. This device was also used as a broadband cross-polarization converter, achieving more than 97% cross-polarization conversion in the range of 2.03 to 3.93 THz. When VO2 was in insulating state, a narrow-band absorption peak with an absorption rate exceeding 94% was obtained, and the device can be used as a biosensor with a sensitivity of 363 GHz/RIU. The designed THz metamaterials have broad application prospects in modulation, sensing, radar communication, and other fields.
{"title":"Vanadium dioxide-assisted multifunctional terahertz devices platform: modulator, polarization converter, and biosensor","authors":"Yonggang Zhang, Xin Cao, Haiyun Yao, Zhongjun Tian, Lanju Liang, Xin Yan, ChengCheng Huang, Fu Qiu, Rui Zhang, Wei Liu, Xiaofei Hu, Zhenhua Li, Ziqun Wang","doi":"10.1117/1.oe.62.11.117101","DOIUrl":"https://doi.org/10.1117/1.oe.62.11.117101","url":null,"abstract":"Abstract. Exploiting the phase transition of vanadium dioxide (VO2), a switchable terahertz multifunctional device integrating narrowband absorption and broadband polarization switching was proposed in our study. The transformation of VO2 from insulating state to metallic state can realize different functions. When VO2 was in metal state, the metamaterial device exhibited an absorption effect exceeding 90% in the range of 1.96 to 4.06 THz, and its amplitude was tunable via changing the conductivity of VO2. Further, the modulation depth reached 171%. This device was also used as a broadband cross-polarization converter, achieving more than 97% cross-polarization conversion in the range of 2.03 to 3.93 THz. When VO2 was in insulating state, a narrow-band absorption peak with an absorption rate exceeding 94% was obtained, and the device can be used as a biosensor with a sensitivity of 363 GHz/RIU. The designed THz metamaterials have broad application prospects in modulation, sensing, radar communication, and other fields.","PeriodicalId":19561,"journal":{"name":"Optical Engineering","volume":"93 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135476138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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