• 정보와 통신
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• 제3권1호
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• pp.52-63
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• 1986

본 고는 통신망 발전 전략, 광 통신의 세계적인 추세, KTA 가입자망에서의 fiber hubbing망, 새로운 디지털 서어비스를 위한 가입자망 전략-DLC(Digital Loop Carrier), CSA(Carrier Serving Area)의 개념과 광전송기술을 이용하여 기존 가입자망에 중첩하는 overlay 방식 및 그것의 ISDN적용을 논의한다

• 한국광학회지
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• 제15권5호
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• pp.415-422
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• 2004

교량과 각종 건물을 비롯한 대형 토목 구조물에서 발생하는 수 mm의 변위를 한 개의 광섬유로 간편하게 측정하기 위하여 광커넥터에서 반사가 굽힘 손실에 의하여 변하는 현상을 이용한 새로운 다중화된 광섬유 변위센서를 제안하고 실험하였다. 한 쌍의 광커넥터 양끝에서 반사광의 신호차이가 두 광커넥터 사이에서 발생한 굽힘 변위에 의해서 달라지는 것을 Optical Time Domain Reflectometer로 측정하여 선형으로 그 변화가 측정되는 변위센서를 만들고, 이 센서 4개를 직렬형으로 배열하여 여러 지점의 변위를 동사에 측정이 가능한 다중화 센서 시스템을 구성하고 실험하였다. 그 결과 이 변위센서를 이용하면 4개 지점에서 각각 최대 6 mm까지의 변위를 6%의 오차범위 내에서 0.9942의 선형성을 가지고 변위를 측정할 수 있음을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.4835-4855
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• 2018

In this paper, we study the sparse signal recovery that uses information of both support and amplitude of the sparse signal. A convergent iterative algorithm for sparse signal recovery is developed using Majorization-Minimization-based Non-convex Optimization (MM-NcO). Furthermore, it is shown that, typically, the sparse signals that are recovered using the proposed iterative algorithm are not globally optimal and the performance of the iterative algorithm depends on the initial point. Therefore, a modified MM-NcO-based iterative algorithm is developed that uses prior information of both support and amplitude of the sparse signal to enhance recovery performance. Finally, the modified MM-NcO-based iterative algorithm is used to estimate the time-varying sparse wireless channels with temporal correlation. The numerical results show that the new algorithm performs better than related algorithms.

• 한국광학회지
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• 제16권6호
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• pp.485-489
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• 2005

본 논문에서는 광섬유 내에서 유도 브릴루앙 산란을 억제하는 방법에 대하여 연구하였다. 광섬유 내에 샘플링 브라그 격자를 사용함에 의하여 강한 Q-스위치 펄스를 전송할 수 있도록 하였다. 격자는 유도 블릴루앙 산란으로 생성되는 스토크 펄스의 스펙트럼이 모두 브라그 격자의 반사 대역에 오도록 설계된다. 1 m 내에 샘플링 광섬유 브라그 격자의 수가 결합계수 보다 유도 브릴루앙 산란의 억제에 직접적인 영향을 미친다는 것을 보였다. 이것은 후방 스토크 파의 발생을 억제하며 유도 브릴루앙 산란의 악 영향을 감소시킨다. 본 연구 방법을 통하여 1 kW 최대 파우어를 갖는 15 ns 펄스가 작은 에너지 손실을 발생시키며 전송될 수 있다는 것을 시뮬레이션을 통해 보였다.

• Journal of the Optical Society of Korea
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• 제7권3호
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• pp.193-196
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• 2003

We have developed a laser welding monitoring system to monitor laser welding process conditions such as sample feed rate, laser focal position, and laser power. A 2 ㎾ Nd:YAG CW laser beam has been applied to the welding of a stainless steel plate (SUS306) to investigate the welding monitoring. Theradiation signal from the weld pool was guided back through the focusing optics and the laser delivery fiber, and measured by a photo detector. By changing the focus of the laser beam along the z-direction, the penetration depth of the welding material has been measured. That shows the penetration depth depends on the frequency fluctuations of the plume signals which can be used in welding quality control.

• Journal of the Optical Society of Korea
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• 제20권5호
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• pp.567-574
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• 2016

We propose a highly birefringent and dispersion compensating photonic crystal fiber based on a double line defect core. Using a finite element method (FEM) with a perfectly matched layer (PML), it is demonstrated that it is possible to obtain broadband large negative dispersion of about -400 to -427 ps/(nm.km) covering all optical communication bands (from O to U band) and to achieve the dispersion coefficient of -425 ps/(nm.km) at 1.55μm. In addition, the highest birefringence of the proposed PCF at 1.55 μm is 1.92 × 10^-2 and the value of birefringence from the wavelength of 1.26 to 1.8 μm (covering O to U bands) is about 1.8 × 10^-2 to 1.92 × 10^-2. It is confirmed that from the simulation results, the confinement loss of the proposed PCF is always less than 10^-3 dB/km at 1.55 μm with seven fiber rings of air holes in the cladding.

• 한국광학회지
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• 제24권1호
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• pp.17-22
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• 2013

High performance plastic optical fiber (POF) $N{\times}N$ star couplers are implemented based on fusing and combining technology. A set of cladding-removed POFs are fused into a solid body by heating and pressing them together to form the transition region between the input and output sides. The operation principle of the proposed star coupler is explained based on ray optics. To demonstrate the performance of the device, $2{\times}2$, $4{\times}4$ and $6{\times}6$ type POF couplers were fabricated and characterized. Performances of the POF star couplers were evaluated in terms of the flatness of the coupling ratios and excess losses.

• Current Optics and Photonics
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• 제5권2호
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• pp.121-128
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• 2021

We propose a novel, tiny optical receiver engine utilizing an all-in-one package based on embedded optics technology. The package's best transmission S21 and reflection S22 opto-electric (OE) bandwidths are 49.8 GHz and 34.9 GHz, respectively, and the reflectance of the optical engine is below -31.7 dB for all channels. The engine satisfies the MIL-STD-883G standard for reliability tests, such as mechanical and thermal shock, and vibration resistance. The sensitivity after 10 km single-mode fiber (SMF) transmission is below -8 dBm. The optical receiver engine is cost-competitive and applicable for 400G coarse wavelength division multiplexing 4 (CWDM4) 10 km optical transceivers.

• Current Optics and Photonics
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• 제5권3호
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• pp.238-242
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• 2021

In this paper, we present an in line plastic-optical-fiber (POF) temperature sensor based on intensity modulation. The in line POF temperature sensor is composed of a POF, including an in-fiber micro hole filled with reversible thermochromic material, the transmittance of which depends on temperature. The reversible thermochromic material was cobalt chloride/polyvinyl butyral gel. A cobalt chloride solution of concentration 30.8 mM was formulated using 10% water/90% ethanol (v/v) solution, and gelled by dissolving polyvinyl butyral in this solution. Four types of in line POF sensors, with in line micro holes of four different diameters, were fabricated to measure temperature in the range of 25 to 75 ℃. The output optical power of all of these in line POF temperature sensors was inversely proportional to the temperature; the relation between output power and temperature was approximately linear, and the sensitivity was proportional to the diameter of the in-fiber micro hole. The experimental results indicate that an in line POF sensor can be used effectively for measuring moderate temperatures.

• 발명특허
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• 제4권4호통권38호
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• pp.30-31
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• 1979