• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.1465-1467
• /
• 2004

Compared with other transport means, safety and timeliness are the merits of railways. Unexpectedly when accident happens, much time and human strength are required to cope with the accident. And for swift recovery, systematic rehabilitation is needed. Recently using MTS(Moving picture Transmission System), we can perform accident rehabilitation and recording work efficiently. MTS is the device that transmits continuous picture information from accident field to control center. e are developing the appropriate system to railway situation to make use of the existing information communication technology, processing technology of video-tex, super high speed transmission technology through fiber-optic, copper cable and network description of information Technology, etc. If these communication-based can technologies are applied to railway system, railway managers can control the accident by inspecting the picture of accident field and can contribute to the safe train operation and the improvement of railway management. In this paper, we investigate the connecting methods when optical fiber is used for moving picture data transmission of train accidents, and its problems. And, we validate MTS's performance through about 28km section of field test.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.485-489
• /
• 2004

We demonstrated numerically that both the chromatic dispersion and the dispersion slope could be compensated by using purely phase-sampled superstructure fiber Bragg gratings provided with chirp of coupling coefficient along the wavelength axis. Also, we propose a purely phase-sampled Bragg grating for dispersion and dispersion slope compensation by introducing a chirp in coupling coefficient and sampling function. The bandwidth of all reflected channels can be equalized.

• Proceedings of the Optical Society of Korea Conference
• /
• 2007.07a
• /
• pp.329-330
• /
• 2007

Today some many types of 3D display are developed but that are not possibly multiviewer, multiview and full parallax. Our new research work uses the Quantum optic to develop 3D display. Quantum mechanically, we can think of the first photon making a virtual transition to the second state. If the second photon appears within the lifetime of that state, the absorption sequence to the third level can be completed. When the electron, located in the third state, shifts to the first state, that electron emits one visible photon. We controlled the two invisible lights to draw a pixel in volume.

• Journal of Astronomy and Space Sciences
• /
• v.36 no.3
• /
• pp.169-180
• /
• 2019

In this study, a batch least square estimator that utilizes optical observation data is developed and utilized to determine geostationary orbits (GEO). Through numerical simulations, the effects of error sources, such as clock errors, measurement noise, and the a priori state error, are analyzed. The actual optical tracking data of a GEO satellite, the Communication, Ocean and Meteorological Satellite (COMS), provided by the optical wide-field patrol network (OWL-Net) is used with the developed batch filter for orbit determination. The accuracy of the determined orbit is evaluated by comparison with two-line elements (TLE) and confirmed as proper for the continuous monitoring of GEO objects. Also, the measurement residuals are converged to several arcseconds, corresponding to the OWL-Net performance. Based on these analyses, it is verified that the independent operation of electro-optic space surveillance systems is possible, and the ephemerides of space objects can be obtained.

• International Journal of Internet, Broadcasting and Communication
• /
• v.13 no.2
• /
• pp.93-102
• /
• 2021

In this research, we present a natural lighting system with transmission distance of 30m and lighting efficiency of 35% (30m standard) for operating hours of 7h/day (based on clear sky). The system is composed of parabolic reflective mirror and modified light pipe that can secure more than 88% of light concentration efficiency. The light loss rate of newly designed light pipe transmission system is demonstrated to 0.8 %/m in the straight-line part and 2%/m in the curved part. Modified light pipe daylighting system shows better performance over fiber optic daylighting system in terms of transmission distance (1.5 times longer) and illuminance (3.05 times higher).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.4
• /
• pp.543-550
• /
• 2018

The rapid growth of IoT technology induced by the fourth industrial revolution has resulted in research into various types of wireless sensors, and applications based on this technology are prevalent in many areas. However, among the various sites where this technology is used, railway bridges and tunnels with lengths of tens of kilometers have problems with data acquisition, due to the signal noise induced by the long distance measurement and EMI induced by the high voltage power feeding system, when conventional electric sensors are used. To overcome these problems, many studies on fiber optic sensors have been conducted as a substitute for the conventional electric sensors. However, restrictions on the types of fiber optic sensors have limited their application in railways. For this reason, a hybrid measurement system with IoT based wireless data communication, in which both electric and fiber optic sensors can be applied simultaneously, has been developed. In this study, in order to evaluate the applicability of the hybrid measurement system developed in the previous study, a real-time test for 4 types of measurement environments, which reflect possible railway sites, is performed. As a result, it was confirmed that the signals from both the electric and fiber optic sensors, which were acquired at a remote area in real-time, showed good agreement with each other and that this measurement system has the potential to handle sensors with a sampling rate of 2.5 kHz. In the future, it is expected that the IoT-based hybrid measurement system will contribute to the improvement of structural safety by enabling real-time structural health monitoring when applied to various measurement sites.

• Journal of information and communication convergence engineering
• /
• v.9 no.6
• /
• pp.753-757
• /
• 2011

The possibility of implementing nonuniform residual dispersion per span (RDPS) in optical links with net residual dispersion (NRD) controlled by precompensation and postcompensation for 960 Gbps WDM transmissions is studied and discussed. The fiber optic communication links investigated in this paper consist of inline dispersion management (DM) for each fiber spans and optical phase conjugator (OPC) at mid-way of total transmission length in order to compensate for WDM signal distortions due to group velocity dispersion (GVD) and nonlinearities. It is confirmed that the effect of nonuniform RDPS distribution on system performance is not significant. It is also confirmed that the optimal NRD is obtained to be one of two values of +10 ps/nm or -10 ps/nm, which depend on the deciding of NRD controlled by precompensation or postcompensation, and the exact RDPS configurations. The effective NRD ranges resulting eye opening penalty (EOP) below 1 dB are independent on the exact RDPS distribution for relative low launch power. Therefore, results show the possibility of implementing the flexible optical links to expand network construction for WDM transmission of high bit-rate capability.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
• /
• v.2 no.2
• /
• pp.22-31
• /
• 2003

The existing training courses for the optical communication construction in even a college and the university, consist of simple cutting and connecting cable technique and the subjects are splitted into parts, to which can not be grasped in a whole. Now, it is strongly demanded that the educational curriculum involves the whole process of the optical communication system construction, which includes design, supervision and up to the fusion splice connection. In this paper, the essential training elements for the optic execution worker are investigated and suggested with the appropriating solution for the experiment room.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.4
• /
• pp.63-69
• /
• 2014

Visible light communication is a communication method using an LED's blinking(ON/OFF), it has a feature of light because of the limit of perception by the human's optic nerve. LED' dimming control used in the VLC system is important factor needed to provide energy saving and life benefits. With advances in VLC system, MIMO technology has received much attention in that it can be obtain channel capacity proportionate to the number of antenna. Therefore, in this paper, with RC method which is one of the MIMO style in VLC system, it is compared communication performance using RZ-OOK, VPPM, MPPM and OPPM. As a result of the simulation was run against this, MPPM works well in terms of Power requirement and OPPM works well in terms of Spectral efficiency and Bandwidth requirement, also it was confirmed that there is a significant impact on the communication performance of each modulation scheme according to the dimming.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.818-821
• /
• 2006

We demonstrate the vertical alignment of liquid crystal on $a-SiO_x$ film surface using the ion beam exposure. Liquid crystal can be aligned vertically by the rotational oblique evaporation of $a-SiO_x$ film. However, the electro-optic switching behavior of liquid crystal along random directions results in disclination lines. We found that we can achieve highly uniform alignment of liquid crystal without disclination lines by using the ion beam exposure. We found from XRD and XPS data that the vertical alignment can be achieved when x approaches 1.5 at the $a-SiO_x$ film surface. We have shown that the pretilt angle can be controlled by changing ion beam parameters, such as the ion beam energy, the angle of incidence, and the exposure time. We found that whether liquid crystals can be aligned vertically or homogeneously on $a-SiO_x$ film can be predicted simply by measuring the change in optical transmittance by deposition of $a-SiO_x$ thin film layers. We also have shown that a liquid crystal cell aligned vertically by the ion beam exposure exhibits the voltage-transmittance curve similar to that of a rubbed polyimide cell.