• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.157-163
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• 2007

Crack detection technique for concrete structures has been developed in this study. Experimental tests were carried out to detect a surface and internal crack, employing common fiber optic cables and OTDR(optical time domain reflectometry), an optical signal analyzer which is widely used to detect damages at fiber optic cables in the field of optical engineering. While initial concrete crack is ready to occur under cracking force, the occurrence and location of the crack are simultaneously detected to give the same damage to fiber optic cables which have been attached to and/or embedded into concrete in advance. It is obtained through successive tests that the principal factors for crack detection is the covering state of fiber optic cable, and total 4 tests including a preliminary test were conducted and the crack detection technique was verified. The practical usefulness would be expected at crack management and maintenance of concrete structures.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.307-309
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• 2003

In the initial deployment stage of optical access networks, optical network systems and optical fiber cables have been provided mainly for commercial buildings or users in KT. According to the demand of residential users who expect to subscribe broadband multimedia services as high bit rate services, the optical access networks get closer to the residential users as FTTCab or FTTH So, it is very important to install optical access networks economically and effectively because that the total cost and usability of optical fiber cables depends on that. Especially, one of characteristics in access networks is the possibility of variation on services demands and technology evolution. Also access networks must be prepared for the final deployment, FTTH. Therefore, the designing and planning of optical access networks are coming to be very important activity for most of telecommunications service providers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.347-352
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• 2010

Under harsh environments in which remote control is impossible, wire-guided control technology is effective for controlling distant underwater vehicles that serve mother ships in missions, such as exploration and installation. When the fiber is unwound from the spool, tension fluctuations occur in the fiber because of the relative velocity of the moving vehicles and unwinding velocity of the fiber. As a result, fiber cables exhibit complicated behaviors, become entangled, and may get cut. In this study, a spool-like design for winding tens of kilometers of fiber cables is proposed by analyzing cable winding. The unwinding performance of the designed spool is estimated by performing nonlinear dynamics analysis of the nonlinear behavior and tension fluctuations observed during the unwinding of the fiber.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.7
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• pp.77-83
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• 2012

Since power system is switching to smart grid, on-line monitoring technology has become necessary for underground distribution power cable. Therefore, the application of DTS(Distributed Temperature Sensing) technology using OFCPC(Optical Fiber Composite Power Cable) capable of monitoring underground distribution power cables has been developed. These can bring about reductions in faults and increases in operating capacity of underground distribution system. To date, the test-bed of optical fiber composite power cable on-line monitoring system has been constructed. Then, matters to be improved have been drawn through verification experiments. This paper presents the improvement and experiment results of the optical fiber composite power cable on-line monitoring system to apply to underground distribution lines in the field.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1801-1804
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• 1991

Described is a new type of control signal transmission system in which an optical fiber is used in place of metal wire cables. This optical transmission system is reliable against EMI and also eliminates the frequency band limitation on the metal wire cables. Since the Z80 CPU is used to distribute the instructions, many tasks can be carried out very easily, and many errors can be avoided. Although an experiment was carried out for 4 bit binary data, the number of bits can be increased to 6 or more without any degradation in reliability. Thus, a variety of applications can be expected to be actualized with this control signal transmission system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1180-1185
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• 2014

This paper describes the effects on SUS tube of power optical fiber composite cable on underground transmission lines. The effects on grounding, air gap between SUS tube and metal sheath, contact resistance between outer semi-conducting layer and metal sheath and grounding of SUS tube application or not are variously analysed using EMTP in normal operating condition as well as single line to ground fault. From these results, in this paper, the scheme for protecting the electrically abnormal phenomena will be established on power-optical fiber composite cable of underground transmission lines. This paper can contribute to specification of grounding reference of SUS tube of optical fiber composite power cable system.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.896-902
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• 2000

Crack detection technique for concrete structures has been developed in this study,. The technique utilizes OTDR(Optical Time Domain Reflectometer) method that is widely used in the field of optical engineering. At present, some techniques, such as the naked eye inspection, inspection by crack gauge, ultra sonic detection and os on, are used for crack detection. However, these are not economical and are often time-consuming works. This method employs a common optical fiber as a means of crack detection. Th optical fiber is fully attached to concrete surface, and a crack on concrete could be detected to synchronize with the crack on optical fiber. The experimental verification was performed for concrete beams and the intial crack on the beam was detected under cracking force.

• The Journal of the Acoustical Society of Korea
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• v.21 no.7
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• pp.614-623
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• 2002

In this paper, it was manufactured an interferometric optical fiber sensor and measured partial discharge acoustic signal caused by defect of power facilities such as power cables, transformers and gas insulation. Acrylic and aluminium mandrels wound with fiber-optic were chosen as optical fiber sensor, Sagnac and Mach-Zehnder interferometers were chosen to detect discharge acoustic signals. The two fiber optic interferometers were identified by using the PZT. Discharge experimentation set in the discharge imitation cell in oil tank and the discharge phenomena was generated. Based on the experimental result, to detect the discharge acoustic signal, Sagnac interferometer can detect stably the acoustic signal than the Mach-Zehnder interferometer. It is shown that Sagnac optical fiber sensor can detect the discharge acoustic signals effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.592-602
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• 2013

The purpose of this study is to optical cable closure and fiber line monitoring system. The current optical cable closure cases have not had any systems that help the central control station recognize opening as well as closing the cases in real-time when opening B2B and B2C lines. to solve this problem, it is considered to create systems that go off alarms, real-time fault location immediately, set alarms for open and close monitoring optical cable closure, and inspect regularly whether optical cables are deficient when monitoring the optical line in real-time and cutting them, in this paper, the monitoring system whose the central control station finds an optical signal block immediately and goes off the alarms when line workers separate components like a connector or a tray from the optical cable closure through OTDR. this study can contribute to stabilize the network quality through the quick and effective operation of the cables.

• Smart Structures and Systems
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• v.9 no.5
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• pp.461-472
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• 2012

This study proposes an optics-based active sensing system for continuous monitoring of underground pipelines in nuclear power plants (NPPs). The proposed system generates and measures guided waves using a single laser source and optical cables. First, a tunable laser is used as a common power source for guided wave generation and sensing. This source laser beam is transmitted through an optical fiber, and the fiber is split into two. One of them is used to actuate macro fiber composite (MFC) transducers for guided wave generation, and the other optical fiber is used with fiber Bragg grating (FBG) sensors to measure guided wave responses. The MFC transducers placed along a circumferential direction of a pipe at one end generate longitudinal and flexural modes, and the corresponding responses are measured using FBG sensors instrumented in the same configuration at the other end. The generated guided waves interact with a defect, and this interaction causes changes in response signals. Then, a damage-sensitive feature is extracted from the response signals using the axi-symmetry nature of the measured pitch-catch signals. The feasibility of the proposed system has been examined through a laboratory experiment.