• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.170-177
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• 2012

A force/torque sensor using carbon fiber plate was designed and developed to make the sensor be able to measure a wide range of multi degree of force and torque. Using carbon fiber plate of 0.3 mm thickness, the sensor was designed and developed, which has a ${\mu}N$ level order of resolution and about 0.01 N ~ 390 N of wide measurement range. The elastic deformation part has a tripod plate structure and strain gauges are attached on the part to detect the force/torque. The coefficient of determination for the sensor is over 0.955 by the calibration experiment so that the linearity of the sensor is confirmed to be good. Also, experiments on applying 0.005 ~ 40 kg (0.05 ~ 390 N) to each axis were implemented and the sensor is proved to be safe under a high load. Finally, to verify the function calculating the direction of load vector, the directions of various load vectors which have the same magnitude but different directions and the directions of the calculated load vectors are compared and analyzed to accord well.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.44-48
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• 2002

In this paper, we demonstrated the simultaneous measurment of triple parameters such as strain, temperature, and vibration using single FBG/EFPI hybrid sensor. The FBG/EFPI sensor system for the strain and temperature measurement and the EFPI sensor system for the the vibration measurement were combined by a wavelength division multiplexer. The optical source of FBG/ EFPI sensor system is a wavelength-swept fiber laser(WSFL) and that of an EFPI sensor system is a laser diode. We performed the simultaneous measurement of thermal strain, temperature, and vibration of a aluminum beam placed in a thermal chamber and validated the efficiency of the constructed measurment system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.7
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• pp.418-423
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• 2000

The fiber Fabry-Perot interferometric(FFPI) sensor is well known in the field of industrial diagnosis due to its outstanding properties such as tiny size, simple and rugged structure, and easy interrogation. As other fiber interferometric sensors, it also suffers from ambiguous output caused by highly periodic feature in its optical transfer function. In most cases, the ambiguity leads to relatively short dynamic operating range and long processing time during power-on reset, which limits its application to some specific fields requiring very high resolution. In this paper a method based on double sensing scheme was proposed to overcome the above difficulty. By employing a fringe selection auxiliary FFPI sensor the original FFPI sensor can identify its true position on the phase domain. The performance test with 10mm FFPI sensor and a thermocouple temperature sensor for reference shows wide dynamic range 0-900$\ell$ keeping a reasonable resolution of 0.1$\ell$ over the entire range.

• Current Optics and Photonics
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• v.2 no.4
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• pp.303-307
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• 2018

We propose a simple ultraviolet (UV) sensor consisting of a conventional single-mode optical fiber capped with an azobenzene-moiety-containing polymer. The UV light changes the dimensions of the azobenzene polymer, as well as the refractive index of the material. Incident light with a wavelength of 1550 nm was reflected at the fiber/polymer and polymer/air interfaces, and interference of the reflected beams resulted in spectral interference that shifted the wavelength by 0.78 nm at a UV input power of $2.5mW/cm^2$. The UV sensor's response to wavelength is nonlinear and stable. The response speed of the sensor is limited by detection noise, which can be improved by modifying the insertion loss of the UV sensor and the signal-to-noise ratio of the detection system. The proposed compact UV sensor is easy to fabricate, is not susceptible to electromagnetic interference, and only reacts to UV light.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.22-27
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• 2017

In this paper, a walking vibration sensing system (WVS system) using a Fiber Bragg Grating sensor (FBG sensor) is proposed. The seismic part of the FBG sensor was redesigned for sensitivity enhancement. The external excitation was assumed to be the walking cycle of an adult male. The FBG seismic sensor was redesigned using CATIA and ABAQUS such that the sensor's first mode natural frequency is 3.5 Hz (which is a value near the external excitation frequency). Compared with existing walking vibration sensing systems, this newly created system improves sensitivity 15 times. It is also suitable for intrusion detection applications.

• 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.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.15-19
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• 2008

A fiber-optic interferometric voltage sensor with high sensitivity is investigated. The fiber-optic voltage sensor is composed of an In-Line Michaelson interferometer bonded on a PZT. The In-Line Michaelson interferometer is a hollow optical fiber spliced to a single-mode fiber at one end and cleaved at the other end. The phase shift of the sensor output signal was induced by the applied AC voltage. The relation between the amplitude of the applied voltage and the phase shift of the sensor output signal was approximately linear and the sensitivity was $0.065{\pi}$ radian/V.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.163-166
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• 2000

Fiber Bra99 grating (FBG) sensor, one of the fiber optic sensor (FOS) offers lots of advantages for structural health monitoring due to its multiplexing capability. Also, it is proper to measure the structural vibration with no mass concentration effect. In this paper, we constructed two sensor arrays composed of 9 FBG sensors for the vibration and mode sensing of a composites beam. For an accurate measurement of wavelength shift, a signal processing board with an electric circuit based on time-interval counting was developed. This sensor system showed a good resolution of dynamic strain (<10${\mu}{\varepsilon}$). Using this sensor system, dynamic strains at 9 points of composite beam was measured and strain measured mode shape of the beam was calculated from the acquired strains and compared with numerical results by ABAQUS.

• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.82-85
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• 2018

This paper proposes a new temperature-compensative displacement sensor with a pair of fiber Bragg gratings (FBG) attached to the inner and outer surfaces of an elastic metal band. The sensor can be also used as a temperature sensor with high sensitivity. The FBG pair shifted Bragg wavelengths in the same direction according to changes in the temperature. However, because the pressure of the metal band shifted a pair of Bragg wavelengths in the opposite direction, the displacement sensor could compensate for the effect of the temperature change in the proposed FBG pair. Results of the experiments showed that the two FBG displacement sensors responded linearly and symmetrically with respect to the displacement, and the displacement could be obtained using the difference between the two Bragg wavelengths.

• Journal of Sensor Science and Technology
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• v.14 no.5
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• pp.302-307
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• 2005

Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown and verified the sinusoidal approximation algorithm that estimates past and coming fringe values. Real-time signal processing program was developed and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below $0.36{\sim}8.6$ nm in the displacement range of $0{\sim}300{\mu}m$ was obtained. The nano-positioner with a piezoelectric actuator and the EFPI sensor system was designed and tested. The positioner successfully reached to the desired destination within 1 nm accuracy.