The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform

Kentaro Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • Simplified optical correlation-domain reflectometry employing proximal Reflection Point
    Japanese Journal of Applied Physics, 2016
    Co-Authors: Makoto Shizuka, Heeyoung Lee, Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We develop a new configuration of simplified optical correlation-domain reflectometry using a proximal Reflection Point. The experimental setup is basically composed of standard silica fibers and includes neither an optical frequency shifter such as an acousto-optic modulator nor an explicit reference path. The light reflected at the proximal Reflection Point, which is artificially fabricated near an optical circulator, is used as the reference light. Unlike the conventional silica-based setup, this configuration can perform a distributed reflectivity measurement along the distal half of the sensing fiber. After demonstration of the basic operation, the incident optical power dependence of the reflectivity distribution is investigated, and the existence of the optimal incident power is clarified.

  • Alternative implementation of simplified Brillouin optical correlation-domain reflectometry
    arXiv: Optics, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the 0th correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multi-mode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise ratio.

  • Alternative Implementation of Simplified Brillouin Optical Correlation-Domain Reflectometry
    IEEE Photonics Journal, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the zeroth correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multimode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise (SN) ratio.

Neisei Hayashi - One of the best experts on this subject based on the ideXlab platform.

  • Simplified optical correlation-domain reflectometry employing proximal Reflection Point
    Japanese Journal of Applied Physics, 2016
    Co-Authors: Makoto Shizuka, Heeyoung Lee, Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We develop a new configuration of simplified optical correlation-domain reflectometry using a proximal Reflection Point. The experimental setup is basically composed of standard silica fibers and includes neither an optical frequency shifter such as an acousto-optic modulator nor an explicit reference path. The light reflected at the proximal Reflection Point, which is artificially fabricated near an optical circulator, is used as the reference light. Unlike the conventional silica-based setup, this configuration can perform a distributed reflectivity measurement along the distal half of the sensing fiber. After demonstration of the basic operation, the incident optical power dependence of the reflectivity distribution is investigated, and the existence of the optimal incident power is clarified.

  • Alternative implementation of simplified Brillouin optical correlation-domain reflectometry
    arXiv: Optics, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the 0th correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multi-mode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise ratio.

  • Alternative Implementation of Simplified Brillouin Optical Correlation-Domain Reflectometry
    IEEE Photonics Journal, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the zeroth correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multimode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise (SN) ratio.

Zongqiang Liu - One of the best experts on this subject based on the ideXlab platform.

  • Improving the Positioning Accuracy of Satellite-Borne GNSS-R Specular Reflection Point on Sea Surface Based on the Ocean Tidal Correction Positioning Method
    Remote Sensing, 2019
    Co-Authors: Wei Zheng, Li Zhaowei, Zongqiang Liu
    Abstract:

    The positioning error of the specular Reflection Point is the main error source of Global Navigation Satellite System Reflectometry (GNSS-R) satellite sea surface altimetry. The existing specular Reflection Point geometric positioning methods do not consider the static-state elevation difference of tens of meters and the decimeter-level time-varying elevation difference between the Reflection reference surface and the instantaneous sea surface. The resulting positioning error restricts the GNSS-R satellite sea surface altimetry from reaching cm-level high accuracy on the reference datum. Under the premise of the basic static-state elevation positioning error correction, reducing the time-varying elevation positioning error is the key to improving positioning accuracy. In this study, based on the principle of elevation correction of GNSS-R Reflection reference surface, the main parameter that determines the real-time variation of sea surface height, ocean tide, is used to correct the specular Reflection Point from geoid to ocean tidal surface. The positioning error caused by the time-varying elevation error of the Reflection reference surface is reduced, the positioning accuracy is improved, and the improvement is quantified. According to the research results, the ocean tidal correction positioning (OTCP) method improves the positioning accuracy by 0.31 m. The positioning accuracy improvement has a good correlation with the corresponding tidal height modulo, and the improvement is 1.07 times of the tidal height modulo. In the offshore, the tidal height gradient modulo is greater than the deep sea, the gradient of the tidal positioning correction has a good response to the tidal height gradient modulo, while the sensitivity of this response decreases in the deep sea.

  • Improving the GNSS-R Specular Reflection Point Positioning Accuracy Using the Gravity Field Normal Projection Reflection Reference Surface Combination Correction Method
    Remote Sensing, 2018
    Co-Authors: Wei Zheng, Li Zhaowei, Zongqiang Liu
    Abstract:

    Global Navigation Satellite System Reflectometry (GNSS-R) is of great significance for the extraction and research of precise information of sea surface topography. Improving measurement accuracy is necessary for realizing spaceborne GNSS-R sea surface altimetry application. The main error source of GNSS-R distance measurement is the error of the specular Reflection Point positioning, which directly affects the sea surface altimetry accuracy on the reference datum. There is an elevation error of several tens of meters between the Reflection reference surface used by the existing specular Reflection Point geometric positioning methods and the sea surface elevation, which is importantly influenced by the earth’s gravity field. Therefore, the gravity field Reflection reference surface correction is the key to improving the specular Reflection Point positioning accuracy. In this study, based on the correction of the GNSS-R Reflection reference surface, research on improving the positioning accuracy of the specular Reflection Point is carried out. Firstly, in order to reduce the positioning error caused by the elevation difference between the Reflection reference surface and the sea surface, the gravity field Reflection reference surface correction method (GFRRSCM) which corrects the Reflection reference surface from the WGS-84 ellipsoid to geoid is proposed, and the positioning accuracy is improved by 25.15 m. Secondly, the normal projection Reflection reference surface correction method (NPRRSCM) is proposed to correct the specular Reflection Point determined by the GFRRSCM from the Reflection reference plane of the radial to that of the normal. Additionally, in the process of solving the spatial geometric relationship of the Reflection path, the approximate substitution error is reduced by directly solving the normal projection on the plane, and the positioning accuracy is further improved by 13.05 m towards the normal. Thirdly, based on the gravity field normal projection Reflection reference surface combination correction method (GF-NPRRSCCM), the specular Reflection Point positioning accuracy is synthetically improved by 28.66 m.

Yosuke Mizuno - One of the best experts on this subject based on the ideXlab platform.

  • Simplified optical correlation-domain reflectometry employing proximal Reflection Point
    Japanese Journal of Applied Physics, 2016
    Co-Authors: Makoto Shizuka, Heeyoung Lee, Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We develop a new configuration of simplified optical correlation-domain reflectometry using a proximal Reflection Point. The experimental setup is basically composed of standard silica fibers and includes neither an optical frequency shifter such as an acousto-optic modulator nor an explicit reference path. The light reflected at the proximal Reflection Point, which is artificially fabricated near an optical circulator, is used as the reference light. Unlike the conventional silica-based setup, this configuration can perform a distributed reflectivity measurement along the distal half of the sensing fiber. After demonstration of the basic operation, the incident optical power dependence of the reflectivity distribution is investigated, and the existence of the optimal incident power is clarified.

  • Alternative implementation of simplified Brillouin optical correlation-domain reflectometry
    arXiv: Optics, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the 0th correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multi-mode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise ratio.

  • Alternative Implementation of Simplified Brillouin Optical Correlation-Domain Reflectometry
    IEEE Photonics Journal, 2014
    Co-Authors: Neisei Hayashi, Yosuke Mizuno, Kentaro Nakamura
    Abstract:

    We developed an alternative configuration of simplified Brillouin optical correlation-domain reflectometry, which can overcome the drawbacks of the original configuration. This system uses, as reference light, the light that is Fresnel reflected at a partial Reflection Point artificially produced near an optical circulator. We show that the influence of the zeroth correlation peak fixed at the partial Reflection Point can be suppressed by replacing the nearby fibers with other fibers having different Brillouin frequency shift values (here, multimode fibers are used). Finally, we demonstrate a distributed measurement for detecting a 1.46-m-long strained section with a high signal-to-noise (SN) ratio.

Amélia Novais - One of the best experts on this subject based on the ideXlab platform.

  • Migration Velocity Analysis using Time-Remigration Trajectory: Regions with Strong Velocity Variations
    SEG Technical Program Expanded Abstracts 2015, 2015
    Co-Authors: H. B. Santos, Tiago A. Coimbra, Joerg Schleicher, Amélia Novais
    Abstract:

    Remigration trajectories describe the position of an image Point in the image domain for different source-receiver offsets as a function of the migration velocity. They can be used for prestack time-migration velocity analysis by means of determining kinematic migration parameters, which in turn, allow to locally correct the velocity model. The main advantage of this technique is that it takes the Reflection-Point displacement in the midPoint direction into account, thus allowing for a moveout correction for a single Reflection Point at all offsets of a common image gather (CIG). We have tested the feasibility of the method on synthetic data from three simple models and the Marmousoft data. Our tests show that the proposed tool increases the velocity-model resolution and provides a plausible time-migrated image, even in regions with strong velocity variations. The most effort was spent on the event picking, which is critical to the method.

  • Remigration-trajectory Time-migration Velocity Analysis in Regions with Strong Velocity Variations
    77th EAGE Conference and Exhibition 2015, 2015
    Co-Authors: H. B. Santos, Tiago A. Coimbra, Jörg Schleicher, Amélia Novais
    Abstract:

    Remigration trajectories describe the position of an image Point in the image domain for different source-receiver offsets as a function of the migration velocity. They can be used for prestack time- migration velocity analysis by means of determining kinematic migration parameters, which in turn, allow to locally correct the velocity model. The main advantage of this technique is that it takes the Reflection-Point displacement in the midPoint direction into account, thus allowing for a moveout correction for a single Reflection Point at all offsets of a common image gather (CIG). We have tested the feasibility of the method on synthetic data from three simple models and the Marmousoft data. Our tests show that the proposed tool increases the velocity-model resolution and provides a plausible time-migrated image, even in regions with strong velocity variations. The most effort was spent on the event picking, which is critical to the method.