• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.144.2-144
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• 2003

• Journal of Information Display
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• v.4 no.3
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• pp.26-28
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• 2003

In the paper, we investigated the Bragg reflective cholesteric display based on polymer stabilization. We studied the bistability in the polymer stabilized cholesteric texture (PSCT) films and baused on which we achieved wider viewing angle though imperfect planar texture.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.190-191
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• 2002

• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.38-43
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• 2014

An external cavity laser supporting two wavelengths is demonstrated by incorporating polymer waveguide Bragg reflectors and a superluminescent light-emitting diode. An oversized rib waveguide structure and Bragg gratings are designed by using the effective-index and transmission-matrix methods. Bragg gratings with different periods are inscribed on a polymer waveguide through double-exposure laser interferometry. In order to tune the cavity loss affected by the reflectivity of Bragg gratings, a Bragg reflectors with varying length is incorporated. Two-wavelength-mode lasing is achieved for the device consisting of 2-mm long, 537-nm period gratings and 2.2-mm long, 540-nm period gratings; the lasing wavelengths are 1554 nm and 1564 nm, with an output power close to 0 dBm, a 20-dB bandwidth of 0.2 nm, and a side-mode suppression ratio of 45 dB.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.274-281
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• 2002

Numerical analysis for the Bragg reflection due to a sinusoidally and a doubly-sinusoidally varying seabeds was performed by using a couple of ordinary differential equations derived from the Boussinesq equations. Incident waves are a train of cnoidal waves. The effects of the dispersion and shape of seabed were investigated. It is shown that the reflection of a sinusoidally varying seabed is enhanced by increasing the dispersion and the amplitude of a seabed. The reflection of waves over a doubly-sinusoidally varying seabed can also be enhanced by increasing the amplitude of seabed decreasing the difference of wave numbers of seabed components.

• Smart Structures and Systems
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• v.12 no.1
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• pp.23-39
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• 2013

In this article, a smart multifunctional optical system-on-a-chip (SOC) sensor platform is presented and its application for fiber Bragg grating (FBG) sensor interrogation in optical sensor networks is investigated. The smart SOC sensor platform consists of a superluminescent diode as a broadband source, a tunable microelectromechanical system (MEMS) based Fabry-P$\acute{e}$rot filter, photodetectors, and an integrated microcontroller for data acquisition, processing, and communication. Integrated with a wireless sensor network (WSN) module in a compact package, a smart optical sensor node is developed. The smart multifunctional sensor platform has the capability of interrogating different types of optical fiber sensors, including Fabry-P$\acute{e}$rot sensors and Bragg grating sensors. As a case study, the smart optical sensor platform is demonstrated to interrogate multiplexed FBG strain sensors. A time domain signal processing method is used to obtain the Bragg wavelength shift of two FBG strain sensors through sweeping the MEMS tunable Fabry-P$\acute{e}$rot filter. A tuning range of 46 nm and a tuning speed of 10 Hz are achieved. The smart optical sensor platform will open doors to many applications that require high performance optical WSNs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2461-2465
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• 2013

This paper investigates the influence of hydrogen loading process on the radiation sensitivity of fiber Bragg gratings (FBG). We made the FBG inscribed in the same commercial Ge-doped fiber with different hydrogen loading periods. We measured the Bragg wavelength shift (BWS) of the FBG exposed to gamma-radiation up to a dose of 18 kGy, and evaluated the change of full width at half maximum (FWHM) and the FBG temperature sensitivity coefficient after irradiation. Varying hydrogen loading parameter led to BWS differences up to nearly a factor of two.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.330-335
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• 2009

A fiber-optic liquid level sensor based on bending cantilever beam has been proposed. A fiber Bragg grating(FBG) embedded in the cantilever beam is used to sensing elements. The basic concept is elongation and constriction of the FBG corresponding to the liquid level variation. The best FBG position on the cantilever for obtaining the high sensitivity was 4 cm from the fixing point. When the liquid level moves up and down vertically, the Bragg wavelength is linearly shifted. But, the wavelength sensitivity of the FBG installed on the upper side of cantilever was four times better than that of the FBG equipped in the lateral side due to the difference of unit strain applied to the FBG. Intensity demodulation using the low-cost edge filter is used to interrogate the Bragg wavelength through converting the wavelength signals into the optical intensity ones. Experiment results show that the electrical output is exponentially proportional to the liquid level. But, it should be overcome for applying to the ships.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.189-194
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• 2001

The present study describes the Bragg reflection of monochromatic water waves propagating over a train of doubly-sinusoidally varying topographies. A numerical model based on the boundary element method is firstly verified by calculating reflection and transmission coefficients of waves over a trench. Calculated solutions are compared with those of the eigenfunction expansion method. The model is then used to simulated reflection of monochromatic water waves propagating over doubly-sinusoidally varying bottom topographies. Obtained reflection coefficients are compared with those of available laboratory measurements, those of the eigenfunction expansion method and the extended mild-slope equation. A reasonable agreement is shown.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1283-1288
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• 2015

In general, IC chip circuit which is operating a cryptographic computation tends to radiate stronger electromagnetic signal to the outside. By using a power detecter such as a loop antenna near cryptographic device, the encryption key can be identified by probing a electromagnetic signal. To implement a method against non-invasive type attack, multi dielectric slab structure on IC chip to suppress radiated electromagnetic signal was introduced. Multiple dielectric slab was implemented by suitably configured to have the Bragg reflection characteristics, and then the reflection response was computed and verified its effectiveness. As a result, the thickness of the dielectric coating was 2mm and the reflection response characteristics for the vertical incidence was achieved to be 91% level.