• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1680-1686
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• 2010

Optical fiber Bragg grating to have the lowest transmitivity at 1549.9nm wavelength was fabricated using a Gaussian distributed KrF Eximer laser of 248nm lasing wavelength and a phase mask of 1.072um period. The proper alignment of an optic setup to fabricate fiber gratings was investigated and the reproductivity of the grating fabrication was examined using the obtained optimum fabrication condition in this experiment.

• ETRI Journal
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• v.26 no.4
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• pp.371-374
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• 2004

We propose and demonstrate a fabrication method of chirped fiber gratings by a thermal diffusion process. The method could suggest a direction for a simple and cost-effective implementation of chirped fiber grating-based devices.

• Composites Research
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• v.17 no.4
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• pp.32-39
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• 2004

Among many fiber optic sensors, FBG sensors are being studied more actively than any other sensor due to good multiplexing capabilities. Recently, the application fields of FBG sensors are mainly focused on the composite materials through embedding rather than attaching on the surface. However, there are many limitations on the embedding FBG sensors into composite materials because of the birefringence effects which is induced when FBG sensors are not embedded parallel to the reinforcing fiber. In this study, the fabrication method of FBG sensors with various grating length that are easy to fabricate with good multiplexing capabilities and more stable from the birefringence effects are investigated. The signal characteristics of the FBG sensors are also verified through the cure monitoring of 2 kinds of composite materials.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.51-56
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• 2006

This paper shows the development of flexible force sensor using the fiber Bragg grating. This force sensor consists of a Bragg grating fiber and flexible silicone rubber (DC184, Dow corning co. Ltd). This sensor does not have special structure to maximize the deflection or elongation, but have good sensitivity and very flexible characteristics. In addition, this sensor has the immunity to the electro magnetic field and can be multiplexed easily, which is inherited from the characteristics of fiber Bragg grating sensor. In the future, this sensor can be utilized the tactile sensor system minimizing the sensor size and developing the fabrication method.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1238-1241
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• 2000

The deformations of concrete specimens were measured at early at early ages, in order to verify the applicability of FBG(Fiber Bragg Grating) sensors. The FBG sensors were directly buried at various locations in the beam-type RC specimens at the time of fabrication. In this experiment, the changes of strains in concrete at early age were successfully measured as the movement in wavelength of light signals. The FBG sensors may be a very effective tool to investigate the mechanical/thermal behavior inside of concrete structures.

• Composites Research
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• v.18 no.5
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• pp.1-8
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• 2005

Among many fabrication methods of composite materials, filament winding is the most effective method for fabricating axis-symmetric structures such as pressure tanks and pipes. Filament wound pressure tanks are under high internal pressure during the operation and it has the complexity in damage mechanisms and failure modes. For this reason, it is necessary to monitor the tank through its operation as well as whole fabrication process. A large number of sensors must be embedded into multi points of the tank from its fabrication step for monitoring the whole tank. Fiber optic sensors, especially fiber Bragg grating(FBG) sensors are widely used for various applications because of good multiplexing capabilities. However, we need to develop the embedding technique of FBG sensors into harsh inner environment of the tank far the successful embedment. In this paper, we studied the embedding technique of a number of FBG sensors into filament wound pressure tanks considering multiplexing.

• Journal of the Optical Society of Korea
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• v.20 no.2
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• pp.291-299
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• 2016

We have investigated the ultimate limits of nonuniform grating couplers (NGCs) for optimized fiber coupling to silicon waveguides, compared to uniform grating couplers (UGCs). Simple grating coupler schemes, which can be fabricated in etching steps of the conventional complementary metal-oxide semiconductor (CMOS) process on silicon-on-insulator (SOI) wafers without forming any additional overlay structure, have been simulated numerically and demonstrated experimentally. Optimum values of the grating period, fill factor, and groove number for ultimate coupling efficiency of the NGCs are determined from finite-difference time-domain (FDTD) simulation, and confirmed with experimentally demonstrated devices by comparison to those for the UGCs. Our simulated results indicate that maximum coupling efficiency of NGCs is possible when the minimum pattern size is below 50 nm, but the experimental value for the maximum coupling efficiency is limited by the attainable fabrication tolerance in a practical device process.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.423-428
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• 2001

Fiber Bragg Grating sensors currently attract a great deal of attentions, mainly due to their potentials in health monitoring for civil structures and composite materials. In this experimental study, the strains of reinforced concrete beams were measured to failure In order to verify the applicability of FBG(Fiber Bragg Grating) sensors. The FBG sensors were directly buried in concrete and attached to re-bars at the time of fabrication. In this experiment, the changes of strains in concrete and re-bars were successfully measured as the movement in wavelength of light signals. The FBG sensors may be a very effective tool to investigate the behavior inside of reinforced concrete structures.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.227-231
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• 1990

A SiO2/Si concave diffraction grating(period: 1.3${\mu}{\textrm}{m}$) for the angular dispersive element of WDM was fabricated by sandwiching the SiO2/Si plane diffraction grating between a slab waveguide and a cylindrical concave block. Using this concave grating and input/output fiber, and wavelength division demultiplexer was composed. The demultiplexer has five channels, the insertion loss of 30dB, the wavelength spacing per channel of 7nm and crosstalk of-15dB.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.155-160
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• 2002

A new fabrication method of FBG sensor with gage length shorter than 10 mm is introduced using the reflection prism with special coating on the surface. It is verified that the bandwidth of FBG sensor increases exponentially as the gage length of it decreases. The transverse stress and strain gradient induced by local stress concentration which occurs during curing has an influence on the FBG sensor with gage length of 2 mm less than that of 10 mm.