Bragg Wavelength

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 6039 Experts worldwide ranked by ideXlab platform

Stephen F Collins - One of the best experts on this subject based on the ideXlab platform.

  • Optical fibre Bragg gratings at harmonics of the Bragg Wavelength and their sensing properties
    Measurement Science and Technology, 2013
    Co-Authors: Stephen F Collins, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter
    Abstract:

    Spectral features in optical fibre Bragg gratings (FBGs) at various harmonics of the Bragg Wavelength arise due to saturation of the writing process. Additionally, phase-mask-produced FBGs possess a complex refractive index pattern, producing an extra periodicity equal to the phase-mask periodicity that supplements the desired periodicity of half that of the phase-mask, as shown via differential interference contrast microscopy. Some spectral peaks or dips occur as doublets with a Wavelength spacing that depends upon fibre alignment relative to the phase mask. These spectral properties are of importance, as they allow the realization of alternative FBG sensors of various measurands.

  • Understanding fiber Bragg gratings at harmonics of the Bragg Wavelength through spectra and images
    OFS2012 22nd International Conference on Optical Fiber Sensors, 2012
    Co-Authors: Stephen F Collins, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter
    Abstract:

    Fiber Bragg gratings written using a phase-mask exhibit a complex refractive index pattern in the fiber core, as observed in differential interference contrast (DIC) microscopy. This results in dual periodicities along the fiber core and gratings at both the Bragg Wavelength, twice the Bragg Wavelength, and the harmonics of these. Features in grating spectra arise from one or both of these periodicities and spectra for twice the Bragg Wavelength (or its odd harmonics) are very sensitive to the details of how the UV complex diffraction field of the phase mask becomes imprinted as refractive index changes in the fiber core.

  • Effect of phase mask alignment on fiber Bragg grating spectra at harmonics of the Bragg Wavelength
    Journal of The Optical Society of America A-optics Image Science and Vision, 2012
    Co-Authors: Scott A Wade, Gregory W Baxter, Fotios Sidiroglou, William G. A. Brown, Stephen F Collins
    Abstract:

    Effects of fabrication conditions on the double-peak structure observed in fiber Bragg gratings at harmonics of the Bragg Wavelength were investigated, showing that slight variations in the alignment of the phase mask can affect the grating spectra significantly. A single peak occurs only when the incident beam direction is perfectly normal with respect to the fiber.

  • Effect of phase mask alignment on FBG spectra at harmonics of the Bragg Wavelength
    2012
    Co-Authors: Scott A Wade, Fotios Sidiroglou, Greg W. Baxter, F Stephen, Stephen F Collins
    Abstract:

    ABSTRACT: Effects of fabrication conditions on the double peak structure observed in fiber Bragg gratings at harmonics of the Bragg Wavelength were investigated, showing that slight variations in the alignment of phase mask can affect the grating spectra significantly. A single peak occurs only when the incident beam direction is perfectly normal with respect to the fiber. 1. INTRODUCTION The demonstration of permanent periodic refractive index perturbations along the core of an optical fiber, and their application as narrowband reflection filters, was first reported by Hill et al. in 1978 [1]. This effect has subsequently been the basis of extensive research and commercial efforts and allowed the development of an extensive range of optical devices used, for example, in various telecommunications and sensing applications [2-4]. These devices, commonly known as fiber Bragg gratings (FBGs), exhibit a wide variety of characteristics as determined by a number of parameters including the fabrication methodology and the geometrical and material properties of the optical fiber. FBGs are typically inscribed via the side illumination of a short length of the core of an optical fiber using suitable laser light. This results in small changes in the core refractive index, the extent of which is related to the integrated fluence at a given point. Due to the many possible variations in the process FBGs may be described in several ways including the manner in which the refractive index of the core of the fiber changes with time, e.g. Type I, Type II, etc. and as

  • Effect of phase mask misalignment on alternative type of pi-phase-shifted FBGs at twice the Bragg Wavelength
    2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim incorporating the Australasian, 2011
    Co-Authors: William G. A. Brown, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter, Nicoleta Dragomir, Stephen F Collins
    Abstract:

    Effects of fabrication conditions on an alternative type of pi-phase-shifted fibre Bragg grating at twice the Bragg Wavelength were investigated, showing that slight variations in the alignment of phase mask affect the grating spectra.

Kazuo Hotate - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of Bragg-Wavelength Distribution in a Long-Length Fiber Bragg Grating with High Speed Sampling
    Applied Physics Express, 2009
    Co-Authors: Koji Kajiwara, Kazuo Hotate
    Abstract:

    We have performed a measurement of Bragg Wavelength distribution in a long-length fiber Bragg grating (FBG) with kHz order sampling rate. We have also realized the total distribution measurement with a repetition rate faster than 1 Hz. The proposed sensing system is based on a reflectometry technique “synthesis of optical coherence function”. The advantage of this system is the capability of random access distributed measurement and fast speed interrogation. At two points of a long-length FBG, we have performed the reflection spectrum variation measurement when an 80 Hz vibration is applied to part of the FBG.

  • Measurement of Bragg Wavelength distribution in a long-length fiber Bragg grating by synthesis of optical coherence function
    19th International Conference on Optical Fibre Sensors, 2008
    Co-Authors: Kazuo Hotate, Koji Kajiwara
    Abstract:

    A sensor system for measuring continuous Bragg Wavelength distribution in a long-length fiber Bragg grating is newly proposed and implemented, based on the technique of synthesis of optical coherence function. Experimental results and simulations are comparatively examined.

  • Proposal and experimental verification of Bragg Wavelength distribution measurement within a long-length FBG by synthesis of optical coherence function.
    Optics express, 2008
    Co-Authors: Kazuo Hotate, Koji Kajiwara
    Abstract:

    In this paper, a sensor system for measuring continuous Bragg Wavelength distribution in a long-length fiber Bragg grating is newly proposed, using synthesis of optical coherence function (SOCF), which is one of the spatial resolving techniques used for reflectometry. Experimental results are also reported. In the process of synthesizing optical coherence function, it is found that an apodization scheme is necessary to obtain the reflection spectrum of local section in a long-length FBG around the coherence peak. As a verification of this method, the detection of local Bragg Wavelength shift due to temperature change within a short section in a long-length FBG is demonstrated experimentally.

  • High-speed interrogation of multiplexed fiber Bragg grating sensors with similar Bragg Wavelength by synthesis of optical coherence function
    Fiber Optic Sensor Technology and Applications IV, 2005
    Co-Authors: Zuyuan He, Tetsuya Hayashi, Kazuo Hotate
    Abstract:

    We have reported recently a multiplexed fiber Bragg grating (FBG) strain sensor by using the technique of synthesis of optical coherence function. By modulating the optical frequency of the light source in a sinusoidal waveform, the coherence function is synthesized into a series of periodical peaks in the meaning of time- integration. Using one of the coherence peaks as a measurement window, and sweeping it along a string of FBGs by adjusting the repetitive frequency of the sinusoidal modulation waveform, we can selectively pick up the reflection as interference signal from any one FBG from the string. Therefore, the FBGs are resolved spatially; they are not necessarily different to each other in Bragg Wavelength. By sweeping the center frequency of the light source in a sawtooth waveform, the shape of the FBG reflection spectrum can be obtained, and thus the amount of the strain applied to the FBG can be estimated. Up to date, 100-Hz interrogation speed was achieved with this method, and the measurement range is limited to within the coherence length of the light source. In this presentation, novel methods are proposed to enhance the interrogation speed and the measurement range further. The performance-limiting factors on the interrogation speed and the measurement range are evaluated. It is found that the detected interference signal appears at a certain frequency shifted from the heterodyne beat due to the sweeping of the center frequency. By observing at the shifted frequency, 1-kHz interrogation speed and measurement range beyond coherence length of the light source are achieved.

  • a multiplexing technique for fibre Bragg grating sensors with the same reflection Wavelength by the synthesis of optical coherence function
    Measurement Science and Technology, 2004
    Co-Authors: Kazuo Hotate, Momoyo Enyama, Shinji Yamashita, Yusuke Nasu
    Abstract:

    We propose a technique for multiplexing fibre Bragg grating (FBG) sensors with the same Bragg Wavelength. We have already developed a technique for the synthesis of an optical coherence function, in which we can select one signal among various reflections along an optical path in an interferometer. By applying the technique, the reflection spectrum of each FBG in arrayed FBGs can selectively be obtained, even if the array is composed of FBGs with the same Bragg Wavelength. In this paper, we first describe the principle of the proposed system, and then show the experimental results.

Scott A Wade - One of the best experts on this subject based on the ideXlab platform.

  • Optical fibre Bragg gratings at harmonics of the Bragg Wavelength and their sensing properties
    Measurement Science and Technology, 2013
    Co-Authors: Stephen F Collins, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter
    Abstract:

    Spectral features in optical fibre Bragg gratings (FBGs) at various harmonics of the Bragg Wavelength arise due to saturation of the writing process. Additionally, phase-mask-produced FBGs possess a complex refractive index pattern, producing an extra periodicity equal to the phase-mask periodicity that supplements the desired periodicity of half that of the phase-mask, as shown via differential interference contrast microscopy. Some spectral peaks or dips occur as doublets with a Wavelength spacing that depends upon fibre alignment relative to the phase mask. These spectral properties are of importance, as they allow the realization of alternative FBG sensors of various measurands.

  • Understanding fiber Bragg gratings at harmonics of the Bragg Wavelength through spectra and images
    OFS2012 22nd International Conference on Optical Fiber Sensors, 2012
    Co-Authors: Stephen F Collins, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter
    Abstract:

    Fiber Bragg gratings written using a phase-mask exhibit a complex refractive index pattern in the fiber core, as observed in differential interference contrast (DIC) microscopy. This results in dual periodicities along the fiber core and gratings at both the Bragg Wavelength, twice the Bragg Wavelength, and the harmonics of these. Features in grating spectra arise from one or both of these periodicities and spectra for twice the Bragg Wavelength (or its odd harmonics) are very sensitive to the details of how the UV complex diffraction field of the phase mask becomes imprinted as refractive index changes in the fiber core.

  • Effect of phase mask alignment on fiber Bragg grating spectra at harmonics of the Bragg Wavelength
    Journal of The Optical Society of America A-optics Image Science and Vision, 2012
    Co-Authors: Scott A Wade, Gregory W Baxter, Fotios Sidiroglou, William G. A. Brown, Stephen F Collins
    Abstract:

    Effects of fabrication conditions on the double-peak structure observed in fiber Bragg gratings at harmonics of the Bragg Wavelength were investigated, showing that slight variations in the alignment of the phase mask can affect the grating spectra significantly. A single peak occurs only when the incident beam direction is perfectly normal with respect to the fiber.

  • Effect of phase mask alignment on FBG spectra at harmonics of the Bragg Wavelength
    2012
    Co-Authors: Scott A Wade, Fotios Sidiroglou, Greg W. Baxter, F Stephen, Stephen F Collins
    Abstract:

    ABSTRACT: Effects of fabrication conditions on the double peak structure observed in fiber Bragg gratings at harmonics of the Bragg Wavelength were investigated, showing that slight variations in the alignment of phase mask can affect the grating spectra significantly. A single peak occurs only when the incident beam direction is perfectly normal with respect to the fiber. 1. INTRODUCTION The demonstration of permanent periodic refractive index perturbations along the core of an optical fiber, and their application as narrowband reflection filters, was first reported by Hill et al. in 1978 [1]. This effect has subsequently been the basis of extensive research and commercial efforts and allowed the development of an extensive range of optical devices used, for example, in various telecommunications and sensing applications [2-4]. These devices, commonly known as fiber Bragg gratings (FBGs), exhibit a wide variety of characteristics as determined by a number of parameters including the fabrication methodology and the geometrical and material properties of the optical fiber. FBGs are typically inscribed via the side illumination of a short length of the core of an optical fiber using suitable laser light. This results in small changes in the core refractive index, the extent of which is related to the integrated fluence at a given point. Due to the many possible variations in the process FBGs may be described in several ways including the manner in which the refractive index of the core of the fiber changes with time, e.g. Type I, Type II, etc. and as

  • Effect of phase mask misalignment on alternative type of pi-phase-shifted FBGs at twice the Bragg Wavelength
    2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim incorporating the Australasian, 2011
    Co-Authors: William G. A. Brown, Scott A Wade, Fotios Sidiroglou, Greg W. Baxter, Nicoleta Dragomir, Stephen F Collins
    Abstract:

    Effects of fabrication conditions on an alternative type of pi-phase-shifted fibre Bragg grating at twice the Bragg Wavelength were investigated, showing that slight variations in the alignment of phase mask affect the grating spectra.

Koji Kajiwara - One of the best experts on this subject based on the ideXlab platform.

Hiroshi Tsuda - One of the best experts on this subject based on the ideXlab platform.

  • A Bragg Wavelength-Insensitive Fiber Bragg Grating Ultrasound Sensing System that Uses a Broadband Light and No Optical Filter
    Sensors, 2011
    Co-Authors: Hiroshi Tsuda
    Abstract:

    An optical filter is incorporated in a conventional ultrasound detection system that uses a fiber Bragg grating (FBG) and broadband light source, to demodulate the FBG sensor signal. A novel ultrasound sensing system that does not require an optical filter is presented herein. Ultrasound could be detected via the application of signal processing techniques, such as signal averaging and frequency filters, to the photodetector output that corresponds to the intensity of the reflected light from a broadband light-illuminated FBG. Ultrasonic sensitivity was observed to be enhanced when an FBG was installed as a resonant sensor. This FBG ultrasound detection system is small and cheap to fabricate because it does not use a demodulating optical filter. The experimental results demonstrate that this system could be applied to ultrasonic damage inspection and acoustic emission measurements. Furthermore, this system was able to detect ultrasound despite the amount of strain or temperature that was applied to the FBG sensor because the ultrasound detection was not sensitive to the Bragg Wavelength of the FBG sensor.

  • Bragg Wavelength-insensitive fiber Bragg grating ultrasound detection system based on a fiber ring laser
    21st International Conference on Optical Fiber Sensors, 2011
    Co-Authors: Hiroshi Tsuda
    Abstract:

    A fiber Bragg grating (FBG) ultrasound detection system incorporating a fiber ring laser was developed. In the system, an FBG was used not only as a sensor but also as the ring cavity mirror. The fiber ring laser emitted lasing light at the Bragg Wavelength of the FBG sensor and the intensity of the lasing light varied with ultrasonic vibration applied to the FBG sensor. The system proved to detect ultrasonic response consistent with the characteristics of the ultrasound impinging on the FBG and to have ultrasound sensitivity enough to detect acoustic emission. This system is quite simple configuration and small in size. Moreover, this system can work irrespective of the Bragg Wavelength of the FBG sensor.

  • Fiber Bragg grating vibration-sensing system, insensitive to Bragg Wavelength and employing fiber ring laser.
    Optics letters, 2010
    Co-Authors: Hiroshi Tsuda
    Abstract:

    A fiber Bragg grating (FBG) vibration-sensing system employing a fiber ring laser utilizing an FBG sensor as the ring cavity mirror was designed and developed herein. The fiber ring laser emitted lasing light at the Bragg Wavelength of the FBG sensor, and the intensity of the lasing light varied with vibrations applied to the FBG sensor. Experiments demonstrated that this system could detect, with good sensitivity, vibrations over a broad band, ranging from just a few hertz up to ultrasound. This sensing system should be able to detect vibrations regardless of both the strain and temperature applied to the FBG sensor.