• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.303-314
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• 2017

With increased human activity in space, the risk of re-entry and collision between space objects is constantly increasing. Hence, the need for space situational awareness (SSA) programs has been acknowledged by many experienced space agencies. Optical and radar sensors, which enable the surveillance and tracking of space objects, are the most important technical components of SSA systems. In particular, combinations of radar systems and optical sensor networks play an outstanding role in SSA programs. At present, Korea operates the optical wide field patrol network (OWL-Net), the only optical system for tracking space objects. However, due to their dependence on weather conditions and observation time, it is not reasonable to use optical systems alone for SSA initiatives, as they have limited operational availability. Therefore, the strategies for developing radar systems should be considered for an efficient SSA system using currently available technology. The purpose of this paper is to analyze the performance of a radar system in detecting and tracking space objects. With the radar system investigated, the minimum sensitivity is defined as detection of a $1-m^2$ radar cross section (RCS) at an altitude of 2,000 km, with operating frequencies in the L, S, C, X or Ku-band. The results of power budget analysis showed that the maximum detection range of 2,000 km, which includes the low earth orbit (LEO) environment, can be achieved with a transmission power of 900 kW, transmit and receive antenna gains of 40 dB and 43 dB, respectively, a pulse width of 2 ms, and a signal processing gain of 13.3 dB, at a frequency of 1.3 GHz. We defined the key parameters of the radar following a performance analysis of the system. This research can thus provide guidelines for the conceptual design of radar systems for national SSA initiatives.

• 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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.173-176
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• 2000

we analyzed multiple ray tracing in the highly scattering optical transmission(HSOT) polymer plate by means of the Monte carlo simulation. Light transmission behavior in the light guide was simulated by a 3-dimensional ray tracing program considering scattering angle given by the Mie theory and mean free path. To improve the uniformity of the conventional HSOT backlight unit, We employed additionally dot patterns. For the proposed structure, we calculated the light transmission behavior and obtained a bright and uniform backlight unit for a large size LCD panel of more than 12 inch.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1116-1118
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• 1990

This paper describes the required frequency bandwidth which is used as a measure for the quality of the PFM transmission system to transmit the control signals. First, the PFM signal which has been distorted due to the frequency bandwidth limit on the transmission line is analyzed by Fourier transform and secondly distortion which has been observed at the receiver is numerically analyzed to make the frequency bandwidth required for transmitting the PFM signals. According to the analysis heretofore, the 50% threshold level for shaping the received PFM signal, which is of 50 % in TTL level, is superior than the 10- and 90-% threshold levels.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.978-982
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• 2010

For mass information transfer, the optical communication using optic fiber has been widely used. Especially, in the field of medical image, the large data is digitalized based on the standard image and it is used for telemedicine with this method. Therefore, to transfer the large amount of data fast and effectively POF (Plastic Optical Fiber) can be used and the development of optic connector for connection between POFs is very important. In this study, for stable optical coupling of POF optic fiber Ferrule and Sleeve were designed and produced by considering the bond stability and the insertion loss according to the physical contact and roughness profile was evaluated. As a result of examining the insertion loss by physical contact method of two optic fibers, it showed the loss was about 1.895dB. According to the results from studying the condition of grinding section for POF mass production, the mass production condition was established as POF profile roughness of 6nm and the loss of 0.2dB or lower by controlling the film size and time step by step.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2002년도 하계학술대회 및 세미나
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• pp.135-136
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• 2002

테라비트급 WDM 광전송시스템은 채널당 10Gb/s의 전송속도를 갖는 채널을 파장분할다중하여 하나의 광섬유로 전송하는 시스템이다. 시스템의 주요 영역으로는 광을 송수신하는 광트랜스폰더, 다채널의 광신호를 다중/역다중 하는 광 다중화기/역다중화기, 광신호를 증폭하기 위한 광증폭기, 그리고 광분기 삽입기 등으로. 구성된다. 우리가 구성하는 테라비트급 WDM 광전송시스템은 구조 변경없이 TM 및 ADM 방식을 수용한다. 시스템의 신뢰성을 위해 종속망 절체 및 광학적 계층에서의 보호절체 방식으로 1+1 OCh 및 1+1 OMS 절체 기능을 선택적으로 수용할 수 있어 시스템 운영에 따라 효율적이고 경제적인 망 운영을 할 수 있다. 감시채널은 시스템 유지보수에 필요한 신호(PMI, FDI, BDI 등) 및 시스템 DCC용으로 되어 있으며, WDM 망에 적합한 감시 체계를 설계하였다.

• 한국통신학회논문지
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• 제28권8A호
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• pp.657-662
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• 2003

광성능을 모니터하기 위해 필요한 것이 OPM(optical performance monitoring module)이다. OPM에서 가장 중요한 것은 광 신호의 파장을 측정하는 것이다. 기존에는 pilot tone을 사용하였으므로 파장값을 얻기가 어려웠지만, 그후 AWG(arrayed waveguide grating), AOTF (acousto optic tuneable filter) 등을 사용하여 다채널 신호에 대한 파장과 전송 품질을 모니터하게 되었다. 본 논문에서는 일반적으로 광 분해능이 우수하다고 평가되는 FFP-TF(fiber fabry perot tuneable filter)를 채택하였으며, FFP-TF를 사용하기 때문에 필요한 기준파장의 설정을 위하여 광섬유격자(FBG : fiber bragg grating)를 사용하였다.

• Journal of information and communication convergence engineering
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• 제21권2호
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• pp.103-109
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• 2023

We investigated the antipodal-symmetric dispersion maps of a dispersion-managed link with a midway optical phase conjugator to compensate for the distorted 960 Gb/s wavelength division multiplexed (WDM) signal caused by these effects. The proposed antipodal-symmetric dispersion map has various shapes depending on the detailed design scheme. We confirmed that the dispersion-managed link designed with the dispersion map of the antipodal-symmetric structure is more advantageous than the conventional uniform dispersion map for compensating WDM channels. It was also confirmed that among the antipodal-symmetric structures, the dispersion map configured with the S-1-profile, in which S is inverted up and down, was more effective for distortion compensation than the dispersion map configured with the S-profile. In particular, we confirmed that the S-1-profile can broaden the optical pulse width intensively at a short transmission distance, more effectively compensating for the distorted WDM channel. Because this structure makes the intensity of the optical pulse relatively weak, it can decrease the nonlinear Kerr effect.

• 한국전자파학회논문지
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• 제14권8호
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• pp.863-870
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• 2003

디지털시스템이 더 빠른 edge rate와 클럭 속도를 갖는 소자를 사용함으로 디지털 정보를 전송하는 시스템은 이제 초고주파 영역으로 진입하였으며, 더 많은 전송량을 얻기 위해 광경로를 활용하는 실정이다. 따라서 본 논문에서는 시스템 설계의 가장 중요한 변수가 되고 있는 디지털 신호의 무결성(Signal Integrity)을 확보하기 위한 병렬 광송수신 모듈에 전기 접속부의 중요성에 관한 시뮬레이션 및 실험적 분석을 수행하였다. 칩 구동을 위한 Access Line 및 Evaluation Board를 다른 두 경우로 모듈을 제작하였으며, S$_{11}$이 -10dB 이상인 마이크로 스트립의 경우, 2.5 Gb/s 광 신호의 왜곡이 많이 형성됨을 확인할 수 있었으며, 반면 S$_{11}$이 -15 dB 이하의 특성을 갖는 스트립라인에서는 완전한 Eye Opening신호를 확인할 수 있었다.

• 한국항행학회논문지
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• 제25권6호
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• pp.517-522
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• 2021

장거리 파장 분할 시스템을 위해 해결해야 하는 광 색 분산과 비선형 현상에 의한 광 신호 왜곡을 보상할 수 있는 광 위상 공액과 결합된 분산 제어 링크를 네트워크 토폴로지의 유연성 관점에서 제안하고 분석하였다. 비선형 효과에 의해 왜곡되는 광 신호의 보상을 위해 적용된 광 위상 공액기는 전체 전송로 중간이 아닌 곳에 위치시켰다. 그리고 광 위상 공액기를 중심으로 전반 전송 구획과 후반 전송 구획을 구성하는 각각의 중계 구간의 잉여 분산 (RDPS; residual dispersion per span)을 서로 다르게 한 분산 제어 링크를 적용하였다. 각 중계 구간의 RDPS가 전반 전송 구획과 후반 전송 구획의 전체 잉여 분산을 같게 만드는 값이 아닌 그 근처의 서로 다른 값으로 결정되어야 왜곡된 광 신호 보상에 효과적이라는 것을 시뮬레이션 결과를 통해 확인하였다.