• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.37-44
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• 2016

Optical fiber temperature sensing systems have incomparable advantages over traditional electrical-cable-based monitoring systems. However, the fiber optic interrogators and sensors have often been rejected as a temperature monitoring technology in real-world industrial applications because of high cost and over-specification. This study proposes a multiplexed fiber optic temperature monitoring sensor system using an economical Optical Time-Domain Reflectometer (OTDR) and Hard-Polymer-Clad Fiber (HPCF). HPCF is a special optical fiber in which a hard polymer cladding made of fluoroacrylate acts as a protective coating for an inner silica core. An OTDR is an optical loss measurement system that provides optical loss and event distance measurement in real time. A temperature sensor array with the five sensor nodes at 10-m interval was economically and quickly made by locally stripping HPCF clad through photo-thermal and photo-chemical processes using a continuous/pulse hybrid-mode laser. The exposed cores created backscattering signals in the OTDR attenuation trace. It was demonstrated that the backscattering peaks were independently sensitive to temperature variation. Since the 1.5-mm-long exposed core showed a 5-m-wide backscattering peak, the OTDR with a spatial resolution of 40 mm allows for making a sensor node at every 5 m for independent multiplexing. The performance of the sensor node included an operating range of up to $120^{\circ}C$, a resolution of $0.59^{\circ}C$, and a temperature sensitivity of $-0.00967dB/^{\circ}C$. Temperature monitoring errors in the environment tests stood at $0.76^{\circ}C$ and $0.36^{\circ}C$ under the temperature variation of the unstrapped fiber region and the vibration of the sensor node. The small sensitivities to the environment and the economic feasibility of the highly multiplexed HPCF temperature monitoring sensor system will be important advantages for use as system-integrated temperature sensors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.105.4-105
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• 2001

This paper describes a newly designed multipoint process monitoring system based on a NIR acousto-optic tunable filter. The NIR multipoint process monitoring system consists of a NIR AOTF device for wavelength selection, an InGaAs array sensor, and a specially designed iin-line type of optical fiber probe. Unlike a FTS(Fourier Transform Spectrometry) or grating based monitoring system, an AOTF has no moving parts, and it can be rapidly tuned to any wavelength in its operating range within microseconds. Thus, the AOTF is advantageous in terms of faster spectral imaging capability and rigidity required for industrial monitoring environment. In the current feasibility evaluation, an enhanced optical fiber probe with 3 monitoring points was used. However, ...

• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.173-182
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• 2014

We describe the application of a distributed optical fiber sensor based on stimulated Brillouin scattering, as an integrated system for safety monitoring of railway infrastructures. The strain distribution was measured statically and dynamically along 60 meters of rail track, as well as along a 3-m stone arch bridge. We show that, gluing an optical fiber along the rail track, traffic monitoring can be performed in order to identify the train passage over the instrumented sector and determine its running conditions. Furthermore, dynamic and static strain measurements on a rail bridge are reported, aimed to detect potential structural defects. The results indicate that distributed sensing technology represents a valuable tool in railway traffic and safety monitoring.

• Current Optics and Photonics
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• 제2권5호
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• pp.407-412
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• 2018

An optimal matching approach is proposed to maximally ensure the output power uniformity of the cascaded encoder in the passive optical network (PON) monitoring system based on a remote coding scheme. The calculation results show that the optimum arrangement can effectively reduce the difference of the total insertion loss in comparison to the random arrangement (i.e., 0.07 dB vs 2.67 dB in the cascaded encoder with 16 output ports). The proposed approach realizes the optimum configuration for the $1{\times}2$ optical splitters used without adding any extra components. The test results of the fabricated cascaded encoder with 32 output ports prove the feasibility of the proposed approach.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.449-450
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• 2015

이 논문에서는 XG-PON (10-Gbps-capable passive optical network) 시스템에서 전송요청을 사용하지 않는 동적대역할당 알고리즘의 성능을 평가한다. OLT (optical line termination)는 ONU(optical network unit)의 상향 대역폭 사용량을 monitoring 해서 ONU의 전송허가량을 추측한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.152-153
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• 2014

이 논문에서는 XG-PON (10-Gbps-capable passive optical network) 시스템에서 ONU (optical network unit)가 전송요청을 OLT (optical line termination)에게 보내지 않는 새로운 동적대역할당 알고리즘을 제안한다. OLT는 ONU의 상향 대역폭 사용량을 monitoring하고 주기적으로 ONU에게 probe용 대역을 할당하여 ONU의 전송허가량을 추측한다.

• 센서학회지
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• 제19권3호
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• pp.184-190
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• 2010

In this paper, a remote submersion warning system based on multi-mode optical fiber(MMF) sensors and a wireless sensor network(WSN) are proposed. To improve the reliability and stability of the sensors, the dual optical fiber sensors combined to the optical coupler are demonstrated. A slave zigbee as a wireless sensor module was used as a platform to monitor and record the signal from the MMF sensors and then transmits these information to a master zigbee wirelessly. The monitoring system running the $LabVIEW^{(R)}$ software was connected to the internet to support the short message service(SMS) through extensible markup language(XML) web service. No matter where the managers are, they can always receive the real-time remote-monitoring data for safety check.

• 정보저장시스템학회논문집
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• 제10권1호
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• pp.27-31
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• 2014

Optical Archive system consists of cartridge, drive and transfer robot. Transfer robot moves disc in cartridge to drive that reads data of disc. Distance between disc in cartridge and transfer robot very short, about 4mm. When disc projects, there is a danger of collision. Collision can cause breakage of disc and breakdown of system. To prevent collision of disc and transfer robot, projection of disc should be detected. In this paper, we proposed error monitoring method of projecting disc in archive data storage using camera. Proposed algorithm is evaluated by experiments with archive system.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.959-961
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• 2003

Cirrus clouds observation was conducted using a lidar system in order to measure their height, thickness and optical depth at Kwangju (35$^{\circ}$10'N, 126$^{\circ}$53'), Korea in winter, December 2002, and spring March and April 2003. Cirrus clouds at high altitude can be distinguished from atmospheric aerosols location by high depolarization ratio and high altitude. Cirrus clouds were observed at 5${\sim}$12km altitudes with a high depolarization ratio from 0.2 to 0.5. Optical depth of cirrus clouds had varied from 0.28 to 1.81. Radiative effect of observed cirrus cloud on climate system was estimated to be negative net flux from ?0.24 to ?31.04 W/m$^{2}$.

• KCI Concrete Journal
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• 제11권3호
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• pp.109-114
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• 1999

Recently the interest in the safety assessment of civil infrastructures has increased. As bridge structures become large-scale, it is necessary to monitor and maintain the safety of large bridges, which requires smart systems that can make long-term monitoring a reality . Civil engineers have applied monitoring systems to several bridges, such as the New Haeng-Ju Bridge and Riverside Urban Highway Bridge, but these applications have some problems with the sensors for long-term measurement, setup techniques for the bridge monitoring system and the assessment of measured data. In the present study, an optical fiber sensor smart system was tested and confirmed in laboratory tests on the concrete members. By Attaching optical fiber sensors to the structural parts of the Sung-San Bridge, the bridge load test was measured. These smart concrete structure systems can be applied to bridges and the load capacity of the bridge can assessed.