• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.2
• /
• pp.147-151
• /
• 2001

An optical fiber sensor is capable of nondestructive measurement of a structure and it has an advantage of the immunity to electromagnetic interference because light is not affected by electromagnetic wave. In addition, if optical fibers are buried in an object like a concrete, this sensor tan analyze defects and physical status of the object without disassembling it. Especially, the fiber Bragg grating sensor is a promising optical fiber sensor capable of nondestructive test of such an object. A fiber Bragg grating has the characteristics of reflecting or blotting light of a specific wavelength. If we apply physical quantity like strain to the fiber Bragg grating, the center wavelength of the reflected light is shifted and then we can find the physical quantity applied to the fiber Bragg grating by measuring the center wavelength shift of the reflected light. The fiber Bragg grating sensor capable ot static and dynamic strain measurement is being used in health-monitoring of buildings, structures, etc. Recently increasing is interest in dynamic strain measurement inevitable to the civil structures such as roads and bridges. In this study we implemented the optical fiber sensor system which can measure dynamic strain at multiple points using Fabry-Perot wavelength demodulation. And we measured the static and dynamic strain using this sensor system with a test structure(cantilever). Measurement results were similar to those obtained with the conventional electrical measurement methods.

• Proceedings of the Optical Society of Korea Conference
• /
• 2002.11a
• /
• pp.68-69
• /
• 2002

• Smart Structures and Systems
• /
• v.11 no.2
• /
• pp.185-197
• /
• 2013

We developed a simultaneous strain measurement and damage detection technique using a pair of surface-mounted piezoelectric transducers and a fiber connecting them. This is a novel sensor configuration of the fiber acoustic wave (FAW) piezoelectric transducer. In this study, lead-zirconate-titanate (PZT) transducers are installed conventionally on a plate's surface, which is a technique used in many structural health monitoring studies. However, our PZTs are also connected with an optical fiber. A FAW and Lamb wave are simultaneously guided in the optical fiber and the structure, respectively. The dependency of the time-of-flight of the FAW on the applied strain is quantified for strain sensing. In our experimental results, the FAW exhibited excellent linear behavior and no hysteresis with respect to the change in strain. On the other hand, the well-known damage detection function of the surface-mounted PZT transducers was still available by monitoring the waveform change in the conventional Lamb wave ultrasonic path.

• Journal of Sensor Science and Technology
• /
• v.14 no.3
• /
• pp.169-179
• /
• 2005

A multiplexed bend loss type single-mode fiber-optic sensor system was prepared to measure the displacement of several cm of the civil engineering structures such as many bridges, tunnels and various buildings. This bend loss type fiber-optic sensor used the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using OTDR (optical time domain reflectometer) for measuring displacements. And the experiments were conducted for showing the measurement feasibility on the range of 10 cm, and the multiplexing experiments were also performed to measure the displacements of 5 measuring positions of an object by setting these 5 fiber-optic sensors on a single mode fiber simultaneously.

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.02a
• /
• pp.151-152
• /
• 2008

• Journal of Sensor Science and Technology
• /
• v.20 no.4
• /
• pp.221-225
• /
• 2011

Intensity-based optical fiber sensors are devised using a blocker which is located between two polymer optical fibers(POFs), one fiber is light-in and the other is light-out. This blocker is moved by an external displacement. Therefore, finding a general formulation of the relation between this displacement and transmission light intensity of various blockers is important to help develop intensity-based optical fiber sensors. In this paper, we consider blockers with arbitrary shapes from circular holes to inclined angled blockers. The transmission light intensities of such blockers should be determined by this generalized equation. In order to verify this equation, the calculated intensities of the blockers are compared with the values acquired from experiment. In the comparison, it is shown that the analytic equation can give the exact values of the transmitted light intensities for the assorted blockers. The range of the displacement measurement is also shown to be about 6 times of the radius of the hole in the case of a 9 degree inclined angle blocker.

• Korean Journal of Optics and Photonics
• /
• v.12 no.4
• /
• pp.294-299
• /
• 2001

Recently great efforts and investment have been made in order to develop a structural health monitoring technology using fiber optic sensors. Therefore, in this study, we have focused on the development of a fiber optic BOTDA (Brillouin Optical Time Domain Analysis) sensor system in order to measure strains distributed on large structures by an optical fiber. The fiber optic BOTDA sensor was constructed simply, with only two electro-optic modulators. The results of strain measurement tests of an optical fiber showed that the strain can be determined accurately from the Brillouin frequency shift measurement on the strain induced range of 10 m in the total fiber length of 4.8 kIn using 200 averaged signals. Also, the strain sensitivity of Samsung single mode fiber was 4.81 MHz/O.Ol % under the test. test.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.12
• /
• pp.209-216
• /
• 2010

Optical Temperature Distribution Sensor Measurement System uses fiber optic sensors itself for temperature measurement is a system which can be measured the Installed surrounding entire temperature as a thousand points by laying a single strand of fiber optic. If there are a lot of measuring points in the distribution Measurement, the cost of each measuring point can be reduced the cost level of existing sensors and at the same time this has the advantage of connecting all sensors as one or two strands of fiber. Generally Optical Fiber is used for communication but Optical Fiber itself can be used for sensor and it has the characteristic of sensor function which can be measured Temperature in the at least each one meter distance. By using these characteristics each sensor and the number of Connection Lines can be reduced. In this paper, we implement a real time temperature monitoring system, which is easy to manage and control for data storage, data management, data storage using a computer and which has the functions of monitoring and correction according to Real-time temperature changes using historical temperature data.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.370-375
• /
• 2003

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile and indentation test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.04a
• /
• pp.42-45
• /
• 2003

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Indentation test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.