• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.192-196
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• 2007

A fiber-optic interferometric temperature sensor is fabricated using a hollow optical fiber with 8 um air hole. This interferometric sensor for measuring temperature consists of 13 mm long hollow optical fiber whose one end is attached to the single mode fiber and the other end is cleaved. After the sensor is put in a furnace, the phase change of the sensor output signal is measured as the temperature of the furnace increases from $28^{\circ}C$ to $100^{\circ}C$. The phase change of the fiber sensor is proportional to the change of temperature and the relationship between the change of phase and temperature is approximately linear. The sensitivity of this sensor is $2.7{\;}radians/^{\circ}C$.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.143-146
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• 1987

Fiber optics provide a solution to the problems at interference, capacity and reliability in communication. Approximately 20 kilometera of a six-fiber, multimode, longwave($1.3{\mu}m$), graded index silica glass fiber optic cable was helically wrapped around a phase conductor at a Korea Electric Power Corporation(KEPCO) 154KV transmission line. This paper presents an economic comparison of several fiber optic cable installation alternative and discusses the characteristics at the helically wrapped fiber cable, as well as the entire installation, including high voltage phase-to-ground (PTG) end termination, and splicing. The fiber link was installed for the field trial and practical use with overhead composite optical fiber cable which installation performed a few years earlier some other location and is intended to accommodate not only telephone but also supervisory Control and Data Acquisition(SCADA), protective relaying, and telemetry functions.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.415-422
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• 2004

We propose and present a new multiplexed bend loss type single-mode fiber-optic sensor system for displacement measurement in order to measure the displacement of several mm of civil engineering structures such as bridges and buildings. We make a bend loss type fiber-optic sensor for measuring displacements using the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using the optical time domain reflectometer. And we fabricate a multiplexed bend loss type fiber-optic sensor detecting linear displacements of 4 measuring positions of an object by setting these new 4 fiber-optic sensors on a single mode fiber simultaneously. We find that the multiplexed fiber-optics displacement sensor has linearity of 0.9942, maximum displacement of 6 mm, and accuracy of 6% for 4 measuring points.

• Journal of Sensor Science and Technology
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• v.9 no.2
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• pp.96-105
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• 2000

Fiber optic TR-EFPI(total reflected extrtinsic Fabry-Perot interferometric) sensor was developed to measure the strain of structures, such as building, bridge, aircraft, etc. It has been difficult to distinguish the increase and decrease of the strain from the conventional fiber optic EFPI sensor because their signals only have a sinusoidal wave pattern related to the change of strain. Also, the absolute strain could not be measured by the simple fiber optic EFPI sensor. In this study, in order to measure the magnitude of strain with the direction of strain, the fiber optic sensor was simply constructed with the total reflected EFPI sensor probe. This probe was manufactured with a single mode fiber and a mirror coated fiber in a silica glass capillary tube. The output signal of this fiber optic TR-EFPT sensor can give the information about the magnitude and the direction of strain. The loading-unloading test was performed by the universal testing machine with alluminum beam specimen to compare the strain from fiber optic TR-EFPI sensor with the value from electrical strain gauge. In the result of this experiment. the strain from fiber optic TR-EFPI sensor had a good agreement with the values from the electrical strain gauge.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.142-148
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• 2004

In this paper, to detect exciting frequency on the latticed fence structure, fiber optic sensor using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 180 cm wide and 180 cm high, the optical fiber, 50 m in length, distributed and fixed on the latticed structure. Single mode fiber, a laser with 1,550 m wavelength, and $3{\times}3$ coupler were used. Excited vibration signal applied to the latticed structure from 200 Hz to 1 KHz. The detected optical signals were compared to the detected acceleration signals and analyzed on the time and frequency domain. Based on the experimental results, fiber optic sensor using Sagnac interferometer detected exciting frequency, effectively. This system can be applied to the structural health monitoring system.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.28-33
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• 2006

Optical-fiber sensors have been developed to determine the concentrations of glucose and lactic acid in blood samples. Fluorescence dye [tris(2,2'-biphenyridine)-ruthenium(II)-chloride (RuBPY)] was entrapped by using a silicon to the unclad tip of a glass optic fiber. Enzymes like glucose oxidase (GOD) and lactate oxidase (LOD) have been immobilized by acrylamide resin adhesive, adsorption with zeolite or covalent bonding with aminopropyl-triethoxysilan. The fiber-optic glucose/lactate sensor was then used to analyze the concentrations of glucose and lactate in blood samples. The results were compared with the results of HPLC analysis and their difference was in error by less then 5 %.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.499-507
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• 2004

We have studied tile detection techniques, which can determine the location and the weight of an intruder into infrastructure, by using fiber-optic ROTDR (Rayleigh optical time domain reflectometry) sensor and fiber-optic BOTDA (Brillouin Optical time domain analysis) sensor, which can use an optical fiber longer than that of ROTDR sensor Fiber-optic sensing plates of ROTDR sensor, which arc buried in sand, were prepared to respond the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR could be used up to 10km at the pulse width of 30ns. The location error was less than 2 m and the weight could be detected as 4 grades, such as 20kgf, 40kgf, 60kgf and 80kgf. Also, fiber optic BOTDA sensor was developed to be able to detect intrusion effect through an optical fiber of tells of kilometers longer than ROTDR sensor. fiber-optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulate all intrusion effect. In the result of this experiment, the intrusion effort was well detected as the distance resolution of 3m through the fiber length of about 4.81km during 1.5 seconds.

• 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.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.173-177
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• 2014

A Rhodamine-based fiber-optic sensor has been developed to detect mercury ions in aqueous environments. The fiber-optic sensor was composed of a mercury-sensing thin film, plastic optical fibers, and a spectrometer. The mercury-sensing thin film with the synthesized Rhodamine derivatives was fabricated with Sol-Gel process. A light emitted by a light source is guided by plastic optical fibers into the thin film in an aqueous solution and a reflected light is analyzed with the spectrometer. The experiment exhibits that an absorbance in the thin film is increased as mercury concentration is increased in the solution and the absorbance by mercury is higher than that by other heavy metals. The fiber-optic sensor exhibits high chromogenic phenomenon of mercury ions among various heavy metals and the correlation between absorbance and mercury concentration in the aqueous environments.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.80-82
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• 1997

An analytical study of the Dynamic Characteristics of a Fiber Optic Gyro is presented. A mathematical model appropriate to the Fiber Optic Gyro system suffering from the system vibration of a driving motor is derived. It is shown that the analysis is directly applicable to the Gyrocompass system.