• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.406-410
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• 2005

we propose an external cavity laser which can adjust the number of longitudinal laser mode by using a tunable chirped fiber. Bragg grating. By inducing a tunable temperature gradient in a uniform fiber Bragg grating, the bandwidth of the unform fiber Bragg grating can be tuned. With the chirped fiber Bragg grating as an external reflector of the external cavity laser, the number of longitudinal laser mode was able to be tuned from one to two or three modes.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.153-158
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• 2009

Stable and tunable dual-wavelength erbium-doped fiber ring laser(EDFL) using a single fiber Bragg grating(FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 nm of wavelength under the electrical power with a 1000 mW. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.925-931
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• 2009

This paper reports a preliminary experimental investigation and characterization of an optical fiber-based submersion sensor system for applications in water flooding and leakage. The sensor system comprises a multi-mode fiber spliced with fiber Bragg grating and an intensity-based interrogator. Submersion tests were conducted in water-air and Glycerin-air environments. By the refractive index of the fiber-probe surrounding materials, the reflectance and the detecting power level is determined. When the probe is dipped into the water, the optical output power dramatically decreases from -7.5dBm to -17.5dBm. But, the center of Bragg wavelength is not affected in spite of external material changes. Temporal response characteristics of the sensor system is investigated to verify the real-time reaction. When the probe is immersed into the liquid, there is no transition time.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.399-400
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• 2006

Etched fiber Bragg grating, Sensitivity of fiber-Bragg-grating sensors to index of surrounding, Hybridization of DNA

• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.108-116
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• 2002

Lasing modes of laser-diode-pumped fiber grating lasers are analyzed by coupled-mode theory. First, a power series solution of the coupled-mode equations is derived under the assumption of an exponentially-decreasing longitudinal modal gain profile for a laser-diode-pumped grating section, followed by determination of the transfer matrix for such a section. Based on these results, an eigenvalue equation for oscillation is then derived and solved numerically for the lasing modes of uniform and phase-shifted fiber grating lasers. Comparisons made with the uniform-gain results indicate that, surprisingly, the lasing mode characteristics are not as significantly altered as might be expected in most cases, even for a highly nonuniform gain profile. In the case of a phase-shifted grating, the phase-shift position appears to have a much greater impact on determining the threshold gain, the modal field distribution, and the front-to-back output power ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.8
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• pp.513-517
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• 2015

We proposed and demonstrated a simultaneous measurement method to detect the refractive index and temperature of a medium using a side-polished fiber involving FBG (fiber Bragg grating). The temperature of a medium was obtained by using the Bragg wavelength shift of FBG, while the refractive index of medium were calculated by using the transmission loss. The Bragg wavelength is independent on the refractive index of the covering medium placed on surface of side-polished fiber, while the transmission loss at off-Bragg wavelength highly depends on the environmental temperature because of thermo-optic effect of the medium.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3039-3045
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• 2023

Fiber-reinforced polymer (FRP) composites are considered suitable candidates for structural materials of spacecrafts due to their excellent properties of high strength, light weight, and corrosion resistance. An online health monitoring method for FRP composites must be applied to space structures. However, the application of existing health monitoring methods to space structures is limited due to the harsh space environment. Here, carbon fiber-reinforced polymer (CFRP) composites embedded with fiber Bragg grating (FBG) sensors were prepared to explore the feasibility of strain monitoring using embedded FBG sensors in γ-radiation environment. The analysis of the influence of radiation on the strain monitoring demonstrated that the embedded FBG can be successfully applied to the health monitoring of FRP composites in radiation environment.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.2
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• pp.175-178
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• 2011

An optical fiber-based beam width measurement technique is presented. The proposed system can be applied to the optical fiber industry in applications such as lensed fiber, optical fiber based laser beam source, and fiber optic sensor. The measurement system is composed of optical fiber, which is used as a transceiver, and a single grating panel which consists of a multi-reflection area with an even non-reflection area. The grating panel is used to vary the reflected light. When the widths of the reflection area and non-reflection area are larger than the optical beam width, the reflected light is varied at the interface between the reflection area and the non-reflection area by the movement of the grating panel. Experiments were conducted in order to verify the feasibility of the proposed technique. Multi-mode fiber combined with a collimator was selected as an emitter and a receiver, and the beam width measurement system was contrived. Subsequently, the proposed method and the system were verified by comparing the experimental results with the results of the conventional charge-coupled device technique.

• Current Optics and Photonics
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• v.2 no.3
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• pp.221-225
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• 2018

We suggested the use of miniature hollow glass tubes having high ultraviolet (UV) transmission characteristics for the protection of optical-fiber-type UV sensors. We have recently proposed a highly sensitive optical sensor in the UV spectral range, using a fiber Bragg grating (FBG) coated with an azobenzene polymer as the photoresponsive material. In this study, we used UV-transparent miniature glass tubes to protect the etched FBG with the azobenzene polymer coating. This technique will be very useful for protecting various fiber-based UV sensors.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.58-62
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• 1997

A new, simple lasing loop configuration employing a fiber grating was proposed and demonstrated for all-optical gain control of erbium-doped fiber amplifier. The lasing loop was designed such that the fiber grating acts as a notch filter to cutoff the lasing light as well as selects the lasing wavelength. The operating gain was clamped to the same level as the loop loss and it could be varied with a tunable directional coupler in the loop. It is believed that this type of gain-controlled erbiumdoped fiber amplifier can have several advantages when used in wavelength-division-multiplexed transmission systems.