• Korean Journal of Optics and Photonics
• /
• v.34 no.2
• /
• pp.72-75
• /
• 2023

In this paper, a fiber-optic current sensor for a bus bar conductor based on the fiber Bragg grating (FBG) is proposed and demonstrated experimentally. The metal bus bar and a magnet are connected to each other through an FBG and the Bragg wavelength of the FBG is changed by magnetic force between the two connected devices. The experimental results showed that the Bragg wavelength of an FBG shifted by 650 pm as the 500 A direct current was applied to the bus bar.

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

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.36 no.6
• /
• pp.594-597
• /
• 2023

We have proposed and demonstrated a fiber optic RH (relative humidity) sensor based on fiber Bragg grating covered with a polyimide film. As the polyimide film absolves the moisture in the air, its volume expands. As a result, the grating period of the FBG (fiber Bragg grating) covered with a polyimide film becomes wide and the Bragg wavelength is shifted. The sensor is implemented by fixing a 30 ㎛ thickness polyimide film on the surface of an optical fiber grating using an adhesive, and the characteristics of the device according to humidity are analyzed. The fabricated FBG RH sensor showed a high sensitivity of 0.0186 nm/RH% and a wide measurement range from 30% to 90%. The influence of environmental temperature on the characteristics of the RH sensor was also measured and analyzed. The feasibility of commercialization is presented.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.8 no.4
• /
• pp.721-725
• /
• 2007

A fiber optic based weight sensor has fabricated using a fiber Bragg grating with a weight sensitive. The sensing concept exploits the inherent characteristics of the FBG and is based on the strain effect induced in the fiber Bragg grating through. A direct indication of the weight level is given by the shift of the Bragg wavelength caused by the expansion of the sensing material. A FBG behaves like a spectral filter which has inherent characteristics that render it very sensitive to strain and temperature. The sensing principle is also based on the strain effect induced in the FBG through the caused by the weight. The experimental setup used for the initial investigation to characterize the mass response of the sensor. The transmitted signal from the sensor was monitored using an optical spectrum analyzer with a resolution bandwidth of 0.4nm. In this paper, we presented the spectral characterization and shaping of FBG by scanning a mass element that affects a small grating fraction at a time, without permanent effects on the optical fiber when the various wavelength and strain is removed. That is, destruction when the optical fiber for weight is physically damaged.

• International Journal of Concrete Structures and Materials
• /
• v.3 no.1
• /
• pp.33-37
• /
• 2009

Fiber Bragg grating (FBG) sensors already have been the focus for structural health monitoring (SHM) due to their distinguishing advantages. However, as bare optical fiber is very fragile, bare FBG strain sensor without encapsulation can not properly be applied in practical infrastructures. Therefore encapsulation techniques for making encapsulated FBG strain sensor show very important in pushing forward the application of FBG strain sensors in SHM. In this paper, a simplified approximate method to analyze the stress transferring rules for embedded FBG strain sensors in concrete monitoring is put forward according to mechanics of composite materials. Shear lag theory is applied to analyze the stress transferring rule of embedded FBG strain sensor in measured host material at the first time. The measured host objects (concrete) and the encapsulated FBG strain sensor are regarded as a composite, and then the stress transfer formula and stress transfer coefficient of encapsulated FBG strain sensor are obtained.

• Journal of Sensor Science and Technology
• /
• v.9 no.4
• /
• pp.307-315
• /
• 2000

To set up the arrays system of FBG(Fiber Bragg Grating) Hydrophone sensor and realize the multi-point signal detection for the wide scope underwater, using WDM(Wavelength Division Multiplexing) method and Passive band-pass filter system, underwater acoustic signal detection of the newly designed two FBG Transducers is successfully experimented. As a result of the experiment, it was possible each signal with different frequent signals is detected for the multi-point up to 1.3KHz in underwater. We can, therefore, prove the possibility on the system design of Hydrophone sensor arrays, using the newly made FBG Transducers.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.184-189
• /
• 2000

Two types of fiber-optic sensors, EFPI(extrinsic Fabry-Perot interferometer) and FBG(fiber Bragg grating), have been investigated for measurement of thermal strain and temperature. The EFPI sensor is only for measurement of thermal strain and the FBG sensor is for simultaneous measurement of thermal strain and temperature. FBG temperature sensor was developed to measure strain-independent temperature. This sensor configuration consists of a single-fiber Bragg grating and capillary tube which makes it isolated from external strain. This sensor can then be used to compensate for the temperature cross sensitivity of a FBG strain sensor. These sensors are demonstrated by embedding them into a graphite/epoxy composite plate and by attaching them on aluminum rod and unsymmetric graphitelepoxy composite plate. All the tests were conducted in a thermal chamber with the temperature range $20-100^{\circ}C$. Results of strain measurements by fiber-optic sensors are compared with that from conventional resistive foil gauge attached on the surface.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.3
• /
• pp.211-216
• /
• 2016

In several industrial fields, epoxy resin is widely used as an adhesive for co-curing and manufacturing various structures. Controlling the manufacturing process is required for ensuring robust bonding performance and the stability of the structures. A fiber optic sensor is suitable for the cure monitoring of epoxy resin owing to the thready shape of the sensor. In this paper, a fiber Bragg grating (FBG) sensor was applied for the cure monitoring of epoxy resin. Based on the experimental results, it was demonstrated that the FBG sensor can monitor the status of epoxy resin curing by measuring the strain caused by volume shrinkage and considering the compensation of temperature. In addition, two types of epoxy resin were used for the cure-monitoring; moreover, when compared to each other, it was found that the two types of epoxy had different cure-processes in terms of the change of strain during the curing. Therefore, the study proved that the FBG sensor is very profitable for the cure-monitoring of epoxy resin.

• Composites Research
• /
• v.17 no.4
• /
• pp.32-39
• /
• 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 Geotechnical Society
• /
• v.16 no.4
• /
• pp.201-208
• /
• 2000

Axial load distribution in model piles was measured by fiber Bragg Grating(FBG) sensor to investigate a possibility of analyzing the load transfer mechanism by Fiber Optic sensor system. Since FBGs of different wave lengths can be multiplexed in an optical fiber, the installation of sensor system and the measurement of strains are relatively simple, compared with consisting strain gages. In this study, FBG sensors and electric strain gages were embedded in the same piles and the distributions of load transfer by two sensor systems were measured. It was observed from the test results that the variations of axial load by both systems showed insignificant difference and that the measurements by FBG were smoother than those by strain gage. Under the environments of laboratory testing, survival rate of embedded FBG system was higher than that of strain gage. Therefore, it was concluded that the use of FBG sensor has a great potential for the measurement of load transfer for pile foundation.