• 천문학회보
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• 제40권1호
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• pp.53.2-53.2
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• 2015

Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. It has been proved that real FBGs based filters were able to eliminate 63 bright sky lines with minimal interline losses in 2011 (GNOSIS). Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual SMFs, the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern (PRAXIS). Multi-mode fibers should be used and the number of modes has to be large enough to capture a sufficient amount of light from the telescope. However, the fiber Bragg gratings can only be inscribed in the single-mode fiber. A photonic lantern bi-directionally converts multi-mode to single-mode. The number of cores in MCFBGs corresponds to the mode. For a writing system consisting of a single ultra-violet (UV) laser and phase mask, the standard writing method is insufficient to produce uniform MCFBGs due to the spatial variations of the field at each core within the fiber. Most significant technical challenges are consequences of the side-on illumination of the fiber. Firstly, the fiber cladding acts as a cylindrical lens, narrowing the incident beam as it passes through the air-cladding interface. Consequently, cores receive reduced or zero illumination, while the focusing induces variations in the power at those that are exposed. The second effect is the shadowing of the furthest cores by the cores nearest to the light source. Due to a higher refractive index of cores than the cladding, diffraction occurs at each core-cladding interface as well as cores absorb the light. As a result, any core that is located directly behind another in the beam path is underexposed or exposed to a distorted interference pattern from what phase mask originally generates. Technologies are discussed to overcome the problems and recent experimental results are presented as well as simulation results.

• 동력기계공학회지
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• 제19권3호
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• pp.11-15
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• 2015

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

• 동력기계공학회지
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• 제16권6호
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• pp.86-91
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• 2012

A multi purpose environmental monitoring system has been developed as a commercially available standard using the techniques which are FBG(Fiber Bragg Grating), Hetero-core spliced fiber optic sensor and etc, for the purposes of monitoring large scaled structures and preserving natural environments. The monitoring system has been tested and evaluated in a possible outdoor condition in view of the full scaled operation at actual sites to be monitored. Additionally, the developed systems in the previous works conveniently provided us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. In this paper, we extend the previous results to a water leakage detection problem and develop a sensing system as a result. By the experimental study, it is verified that multi-point leakage detection is possible using single line optical fiber.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2691-2695
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• 2009

오늘날 광통신 시스템은 거의 무한대의 대역폭을 지니게 되었으며 이를 통하여 다양한 멀티미디어 데이터들을 신속하게 전송하는데 사용되고 있다. 이러한 광통신 시스템 하에서 텍스트, 이미지 및 동영상 등 다양한 멀티미디어 데이터들을 송수신 하기 위해서는 통합된 통신서비스시스템의 사용이 필수적이다. 본 논문에서는 멀티 비디오데이타와 오디오 데이타를 한가닥의 광통신 라인으로 주고받을 수 있도록 해주는 광 MVAD(Multi-Video Audio Data)쌍방향 다채널 링크시스템을 개발하였다. 개발된 광링크 시스템은 오직 하나의 광케이블을 사용하여 광통신시스템을 구축 할 수 있으며 우수한 영상과 음향을 공급하는 광섬유 매개체로 인하여 다양한 분야에 적용이 가능하다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권5호
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• pp.263-266
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• 2006

An optical microphone was developed using a dual-core multi-mode fiber block and a membrane type micromirror. The fiber block serves as a compact optical head, and the micromirror as a reflective diaphragm. The micromirror is designed to be suspended through a silicon bar connected t a frame, allowing for displacement induced by acoustic waves. The optical head is implemented by integrating two multi-mode fibers in a single block, and used to transfer light signals between it and the diaphragm. For the assembled microphone, its static characteristics were observed to reveal the operating point defined as the optimum distance between the optical head and the diaphragm. And its dynamic response was tested to exhibit a frequency bandwidth of 3 kHz with the variation of $\sim5dB$.

• 한국전자통신학회논문지
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• 제7권5호
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• pp.1079-1085
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• 2012

현재 전 세계의 많은 과학자들이 지속 가능한 에너지원을 찾기 위하여 많은 노력을 하고 있지만, 태양광에너지가 궁극적인 해답이 될 것으로 받아들여지고 있다. 이러한 광 에너지는 조명용, 발열용, 통신용 등으로 사용될 수 있으며, 심지어 최근에는 광에너지로 동작하는 광자구동 모터에 대한 연구결과도 나오고 있다. 본 논문에서는 이러한 광에너지를 광섬유를 통해 전송할 수 있는 기술에 대해 이론적인 분석을 수행하였다. 특히, 한 가닥의 광섬유에 여러 개의 코어(core)가 삽입된 멀티코어(multi-core) 광섬유를 이용한 광에너지 전송의 에너지 전송량에 대해 예측해 보았다. 본 논문의 분석 결과에 따르면, 한 가닥의 멀티코어 광섬유로 약 2 kW 의 광에너지 전송이 가능할 것으로 예측되었으며, 초고압선처럼 수 cm 의 직경으로 광섬유 다발을 묶을 경우에는 10 MW 이상의 광에너지 전송이 가능할 것으로 예측되었다. 이는 도체 전력선과 비교하여 절반수준의 에너지 전송량으로 충분한 경쟁력이 있을 것으로 생각된다.

• 한국정밀공학회지
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• 제21권5호
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• pp.38-45
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• 2004

As optical communication is being substituted for telecommunication, the demand of a large variety of fiber optic components is increasing. V-groove substrates, one of the module components, are used to connect optical fibers to optical planar circuits and to arrange fibers. Their applications are multi-channel optical connectors and optical waveguide fiber coupling, etc. Because these substrates are a critical part of the splitter in a multiplexer and a multi fiber connector, precise and reliable fabrication process is required. For precisely aligning core pitch between fibers, machined core pitch tolerance should be within sub-microns. Therefore, these are generally produced by state-of-the-art micro-fabrication like MEMS. However, most of the process equipment is very expensive. It is also difficult to change the process line for custom designs to meet specific requirements using various materials. For various design specifications such as different values of the V angle and low-priced process, the fabrication method should be flexible and low cost. To achieve this goal, we have suggested a miniaturized machine tool with high accuracy positioning system. Through this study, it is shown that this cutting process can be applied to produce V-groove subtracts. We also show the possibility of using a miniaturized machining system for producing small parts.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2002년도 봄 학술발표회 논문집
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• pp.13-16
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• 2002

The Intervertebral disc is a composite structure made up of the nucleus pulposus (NP) core surrounded by the multi-layered fibers of the annulus fibrosis (AF)[1]. Water is drawn into the NP by the presence of hydrophilic proteins called proteoglycans [2]. The AF, with successive layers oriented in alternating directions, surrounds the NP. These layers are placed under tension as the NP absorbs water and swells [3]. (omitted)

• 한국광학회지
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• 제15권1호
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• pp.28-33
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• 2004

상부 도파로와 중간 결합층이 적층된 단일모드 광섬유를 기본구조로 하는 측면 연마 광섬유 결합기를 상호 광 결합이 일어나는 영역을 다층막 도파로로 등가화하여 결합 효율을 해석하였다. 다층막 구조에서 중간 결합층의 유무에 따른 반사도를 계산하여 상부 도파로의 굴절률의 함수로 도시하였고, 상부 도파로의 굴절률이 광섬유 코어의 굴절률보다 클 경우 중간 결합층의 조건에 의해서 광 결합이 증가되어짐을 보였다. 리튬나오베이트를 상부 도파로로 가지는 결합기의 실험결과를 톤해 이론적 해석의 타당함을 보였고 계산 결과와 일치함을 보였다.

• 한국해양공학회지
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• 제21권3호
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• pp.46-51
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• 2007

A multi-purpose environmental monitoring system has been developed as a commercially available standard using the technique of hetero-core spliced fiber optic sensors, for the purposes of monitoring large-scale structures and preserving natural environments. The monitoring system has been tested and evaluated in a possible outdoor condition, in view of the full-scale operation at actual sites to be monitored. Additionally, the developed system in this work conveniently provides us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. Two channels of optical fiber line were monitored in each channel, three displacement sensor modules were connected in series, in order to examine the performance to a pseudo-cracking experiment in the outdoor situation and to clarify temperature influences an the system, in terms of the coupling of optical connectors and the OTDR stability. The results from the pseudo-cracking experiment agreed with the actual cracks, by means of calculation, based an the detected displacement values and their geometrical arrangement of the used sensor modules. The temperature change, ranging from 10 to $20^{\circ}C$ resulting from the 10-days free running operation, was found to influence the system stability of ${\pm}10{\mu}m$, primarily due to the coupling instability of the used optical connectors. It was found that fusion splicing, rather than the use of connectors, reduced the fluctuation dawn to ${\pm}2{\mu}m$. The specification and performance of various option modules have been demonstrated to show the capability of inspecting various physical quantities by use of the single system, which would be suitable for multi-purpose environmental monitoring.