• 한국광학회지
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• 제15권5호
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• pp.409-414
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• 2004

본 논문에서는 광섬유 장주기 격자를 이용한 센서 신호처리 시스템을 구현하였다. SLD와 Fabry-Perot 필터를 이용한 동조 반도체 광원과 Fabry-Perot 필터내의 PZT의 히스테리시스 특성을 보상하기 위한 에탈론 필터를 사용하였으며, 절대적인 기준 파장을 제공하기 위하여 온도 안정화된 광섬유 브래그 격자를 사용하였다. 시스템에서 검출된 신호를 A/D 변환하여 컴퓨터로 입력하고 신호 처리하여 결과를 모니터상에 표시하였다.

• ETRI Journal
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• 제28권6호
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• pp.739-744
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• 2006

In this paper, we report numerically calculated results of testing a temperature-insensitive refractive sensor based on a planar-type long-period waveguide grating (LPWG). The LPWG consists of properly chosen polymer materials with an optimized thermo-optic coefficient for the core layer in a four-layer waveguide structure. The resonant wavelength shift below the spectral resolution of the conventional optical spectrum analyzer is obtained accurately over a temperature change of ${\pm}7.5^{\circ}C$ even without any temperature control. The refractive index sensitivity of the proposed grating scheme is about 0.004 per resonant wavelength shift of 0.1 nm for an optimized thermo-optic coefficient.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.221-225
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• 2008

We propose a simple hydrogen detection scheme based on a Mach-Zehnder interferometer formed with a pair of palladium-coated long-period fiber gratings (LPGs). Since an LPG pair offered a fine-structured interference fringe in its transmission spectrum, the resolution as a sensor could be appreciably enhanced compared to that of a single LPG. As the palladium layer absorbed hydrogen, the effective refractive indices of the cladding modes were increased so that the interference spectrum was blue-shifted up to 2.3 nm with a wavelength sensitivity of -0.29 nm/min for 4% of hydrogen concentration.

• Journal of the Optical Society of Korea
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• 제13권4호
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• pp.428-433
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• 2009

A photonic crystal fiber with two large air holes outside the holey cladding region is fabricated to induce an effective long periodic grating (LPG) in the core by an electric arc discharge. We believe that the two large air holes lead to the asymmetric perturbation in the core under the electric arc discharge, thereby introducing the coupling to the first higher-order mode. The transmission characteristics of the PCF with the LPG for the external perturbation such as strain, curvature, and temperature are also investigated. It was found that the shift of resonance peak in the transmission spectrum depends on the bending direction. The curvature of 8.55 $m^{-1}$ results in the center wavelength shifts of 1.8, 4.3, and 11 nm for a vertical, diagonal, and horizontal direction of the curvature to the large air-hole alignment, respectively.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.72-73
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• 2000

Optical fiber gratings have been intensively studied for applications in optical fiber communications and sensor systems due to their all-fiber configuration, low insertion loss, low cost, and high flexibility. Especially, cladding mode coupling fiber devices such as long period gratings (LPG) and acousto-optic tunable filters (AOTF) have been developed as a gain equalization filter in erbium doped fiber amplifier (EDFA) for wavelength division multiplexing (WDM) systems$^{(1-2)}$ . (omitted)