• Title/Summary/Keyword: Long-period grating

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Resonant Wavelength Characteristics of Arc-Induced Long-Period Fiber Gratings (아크 유도 장주기 광섬유 격자의 공진 파장 특성)

  • Chung, Chul;Lee, Ho-Joon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.39 no.10
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    • pp.48-56
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    • 2002

  • A fabrication method of long--period fiber gratings (LPFGs) that can be easily controlled resonance wavelength and losses is introduced. We used the superposition method that core and cladding diameter are modulated by applying a number of small electric-arc to the normal fiber. We derived an equation of resonance wavelength change according to core diameter variation using the phase matching condition and showed the results are well matched with experiments. The measured resonant wavelengths of arc-induced superposition LPFGs according to grating period are well coincident with that of phase matching condition. The resonance wavelength is measured for the temperature changes and a slight mechanical strength degradation of arc-induced LPFGs is observed by increasing arc times.

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High-Resolution Interrogation Technique for Fiber Bragg crating Sensor Using Long-Period Fiber Grating Pair and Erbium-Doped fiber

  • Jung, Jae-Hoon;Lee, Yong-Wook;Lee, Byoung-Ho
    • Journal of the Optical Society of Korea
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    • v.6 no.1
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    • pp.5-12
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    • 2002

  • A novel interrogation scheme to detect fine Bragg wavelength shift using a long period fiber grating pair with erbium-doped fiber inserted between the two gratings is reported. The technique is shown to feature high resolution and much more immunity to temperature perturbation compared to the conventioned Mach-Zehnder interferometer demodulation system. For quasi-static strain measurement, this approach provides high wavelength resolution of 0.05 pm that corresponds to 41.7 ne in strain and $3.8 $\times$ 10^{-3}$$^{\circ}C$ in temperature. This interrogation system is also employed in dynamic measurement to obtain the minimum detectable strain perturbation of ~ 8.76 ne/H $z^{{\frac}{1}{2}}$ at 100 Hz. Moreover, this interrogation system has prominent thermal stability. This thermal stability comes from the fact that two arms of the interferometer, the core and cladding in erbium-doped fiber, are exposed to nearly the same environment .

  • https://doi.org/10.3807/JOSK.2002.6.1.005 인용 PDF KSCI

Polarization-controlled Interleaved Signal Gating Fiber Device (편광으로 조절되는 인터리빙 신호 게이팅 광섬유 소자)

  • Lee, Yong-Wook
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.10
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    • pp.1820-1822
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    • 2007

  • In this paper we fabricated a fiber device composed of cascaded long-period fiber gratings between which a birefringent erbium-doped fiber was inserted and proposed its application as a polarization-controlled interleaved signal gating fiber device. Because the core and cladding modes of the fabricated fiber device have polarization-dependent phase difference due to the birefringence of the erbium-doped fiber, its interference spectrum can be modulated by varying the input polarization.

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Bending Characteristics Change of Long-Period fiber Grating due to Co-doping of Boron for Optical fiber Sensors (광섬유 센서 구성을 위한 보론 첨가에 따른 장주기 광섬유 격자의 구부림 특성 변화)

  • Moon, Dae-Seung;Chung, Young-Joo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.5
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    • pp.339-342
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    • 2005

  • In long-period fiber grating (LPFG) to be made up optical fiber sensors, resonance coupling occurs between the forward-propagating core mode and cladding modes at the wavelength that satisfy the Phase matching condition. The resonance wavelength and the coupling strength depends strongly on the external environment like temperature, strain, and ambient index. These characteristics can be utilized for various applications as optical fiber sensors. fabrication of optical fiber gratings is typically based on the photosensitivity effect, i.e. the permanent change of the refractive index upon irradiation of the UV beam, and therefore, fabrication of the optical fiber with high phososensitivity is an important part of the research on optical fiber gratings. In this work, we measured the effort of to-doping of boron on the index difference between the core and cladding of the optical fiber and the sensitivity of the LPFC to the temperature and bending changes. We observed that the index difference between the core and the cladding decreased by $(1.69{\times}10^{-4}/SCCM)$ and the temperature sensitivity of the resonance wavelength shirt decreased by $(0.01145nm/^{\circ}C/SCCM)$. The dependence or the bending-induced changes or the transmission characteristics of LPFG on the tore-cladding index difference was investigated experimentally. The measurement results indicate that the bending sensitivity increases as the index difference decreases.

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