• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.39-44
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• 2004

Fiber Bragg grating sensors are fabricated by core index modulation using UV laser and phasemask. Bragg wavelength of the grating is changed by the external strain. In this paper, a signal processing system of fiber Bragg grating sensor has studied in the optical wavelength domain. The system is based on the sweep semiconductor light source that consists of SLD, F-P tunable filter and etalon filter. The hysteresis effects of PZT in the F-P tunable filter are compensated. The long term measurement stability is obtained by controlling the temperature of F-P tunable filter and the SLD. We compare the strain data from fiber Bragg grating sensor and that from strain gauge at concrete hume pipe. We also get very good results for the long gauge displacement using fiber Bragg grating sensor which are identical to the data with short gauge length ordinary displacement sensor.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.86-91
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• 2012

A multi purpose environmental monitoring system has been developed as a commercially available standard using the techniques which are FBG(Fiber Bragg Grating), Hetero-core spliced fiber optic sensor and etc, for the purposes of monitoring large scaled structures and preserving natural environments. The monitoring system has been tested and evaluated in a possible outdoor condition in view of the full scaled operation at actual sites to be monitored. Additionally, the developed systems in the previous works conveniently provided us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. In this paper, we extend the previous results to a water leakage detection problem and develop a sensing system as a result. By the experimental study, it is verified that multi-point leakage detection is possible using single line optical fiber.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.81-84
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• 2001

We propose the cascade FBG(Fiber Bragg Grating)s to compensate the dispersion, discuss the dispersion characteristics of such cascaded FBGs, compare with the single FBG dispersion compensator. For these, we theoretically consider the sencond- and third-order group-velocity dispersion(GVD) in the single fiber grating using plane wave solution and the coupled mode equation. We also theoretically find the group-velocity dispersion in the cascaded fiber gratings from the results in the single fiber grating and present the optimum disign data of the cascaded FBGs dispersion compensator in the N-channel WDM system through the numerical simulation.

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.227-232
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• 2012

A large-signal time-domain model is implemented to analyze an FG-LD (Fiber Grating Laser Diode) in which a reflective laser diode is hybrid-integrated with a fiber Bragg grating (FBG). When the length of the externally integrated resonator is 8 mm, in which the effective FBG length of 2.1 mm is included, a static frequency chirp of 0.44 GHz and a dynamic frequency chirp of 6.4 GHz are observed. In addition, it is also observed that the eye of the 10Gbps NRZ signal is well open. The FG-LD is expected to be a cost-effective solution for a 10Gbps-class single wavelength laser covering a span of 50 km range.

• Korean Journal of Optics and Photonics
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• v.27 no.6
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• pp.203-211
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• 2016

We have studied the hybrid method for reconstructing apodized chirped fiber Bragg gratings, using both an analytic estimation of grating parameters and an optimization algorithm. The Hilbert transform of the reflection spectrum was utilized to estimate grating parameters, and then the layer-peeling algorithm was used to obtain refined parameter values by the differential-evolution optimization process. Calculations for a fiber Bragg grating with wavelength chirp rate 2 nm/cm were obtained with an accuracy of $6{\times}10^{-5}nm/cm$ for the chirp rate and $3{\times}10^{-9}nm/cm$ for the index modulation, with much improved calculation speed and high reliability.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.60-61
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• 1999

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.83-83
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• 1996

• Optical Science and Technology
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• v.5 no.2
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• pp.46-52
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• 2001

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.343-349
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• 2005

In this research, the fiber Bragg grating sensors with long gauge for displacement measurement in the long distance is developed and tested. The sensors show an accuracy and a capability for displacement measurement oin long distance. Monitoring using static logger of system of FBG sensor with strained optical fiber shows the capability of measurement in the harsh environment such as strong wind. Measurement of long distance displacement by optical fiber sensor if use $250{\mu}m$ optical fiber and impose some strong pre-tension shows possibility in monitoring of nuclear containment structure.

• Journal of IKEEE
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• v.12 no.2
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• pp.102-109
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• 2008

In this paper, the thermal characteristics of a tunable all-optical fiber Bragg grating(FBG) filter was investigated by numerical analysis. From the results, it is possible to tune a Bragg center wavelength along temperature variation because a Bragg center wavelength is varied linearly according to its operating temperature, however, the reflectivity of a Bragg center wavelength was reduced over a limited high temperature. Accordingly, it is possible to obtain the stability of a tunable all-optical FBG filter within $600^{\circ}C$, but it is difficult to tune a Bragg center wavelength over this temperature.