• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.707-708
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• 2012

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1400-1409
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• 2001

This paper describes a fiber optic sensor suitable for non-contact detection of ultrasonic waves. This sensor is based on a fiber optic Sagnac interferometer. Quadrature phase bias between two interfering laser beams in Sagnac loop is introduced by a polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output versus phase bias. This method eliminates a digital signal processing for detection of ultrasonic waves using Sagnac interferometer. Interference intensity is affected by the frequency of ultrasonic waves and the time delay of Sagnac loop. Collimator is attached to the end of the probing fiber to focus the light beam onto the specimen surface and to collect the reflected light back into the fiber probe. Ultrasonic waves produced by conventional ultrasonic transducers are detected. This fiber optic sensor based on Sagnac interferometer is very effective for detection of small displacement with high frequency such as ultrasonic waves used in conventional non-destructive testing.

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.203-210
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• 2012

Sagnac interferometer gyroscopes can be divided into three large generations using starting points of time or highlights of their research. As the first generational Sagnac interferometer, the ring laser gyroscopes have been studied since the 1960s by laser invention, and as the second generational Sagnac interferometer, the fiber optic gyroscopes have been studied since the 1970s by invention of optical fiber for communication. In the latter half of the 1990s, after having confirmed the wave theory of the atom, studies of atomic interferometers were started for a next generation gyroscope application. This paper discusses the operation principles, application, and future prospects of these three generations of Sagnac gyroscopes.

• The Journal of the Acoustical Society of Korea
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• v.21 no.7
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• pp.614-623
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• 2002

In this paper, it was manufactured an interferometric optical fiber sensor and measured partial discharge acoustic signal caused by defect of power facilities such as power cables, transformers and gas insulation. Acrylic and aluminium mandrels wound with fiber-optic were chosen as optical fiber sensor, Sagnac and Mach-Zehnder interferometers were chosen to detect discharge acoustic signals. The two fiber optic interferometers were identified by using the PZT. Discharge experimentation set in the discharge imitation cell in oil tank and the discharge phenomena was generated. Based on the experimental result, to detect the discharge acoustic signal, Sagnac interferometer can detect stably the acoustic signal than the Mach-Zehnder interferometer. It is shown that Sagnac optical fiber sensor can detect the discharge acoustic signals effectively.

• Korean Journal of Optics and Photonics
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• v.23 no.2
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• pp.71-76
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• 2012

A Sagnac-type Mach-Zehnder interferometer(SMZI) is a very stable instrument with respect to phase drift because all optical paths can share common optical components. We have observed very stable interference fringes in single photon interference experiments with an extremely attenuated laser beam, and with heralded single photons prepared from polarization correlated photon pairs in type-II spontaneous parametric down-conversion. The phase stability is measured to be about ${\pm}0.18$ rad for the SMZI, in contrast, conventional MZI showed the phase fluctuation of around ${\pm}1.02$ rad.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1607-1612
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• 1997

A new method of stabilizing a Sagnac optical fiber current sensor is presented. This method is characterized by creating aproper amount of circular birefringence the fibersagnac, whose correaponding value of rotation angle is (m+1/2)$\pi$-$2\Psi$, removes the effect of linear birefringence and leads to achieve good stability. Using the technique the stability of the current sensor was improved more than 10 times to within ${\pm}2.3{%}$ at 300Arms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.533-534
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• 2010

Fiber optic sensor has bee widely used in the industrial applications. For the application of acoustic detection of the high voltage electric transformer Sagnac interferometer can be used. In this paper several different materials of mandrel were used in the fiber sensor array. Based on the transformer oil fiber optic sensor is more sensitive than in the air.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.94-99
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• 1997

A new method of stbilizing the sagnac interferometric fiber optic current sensor inteh presence of birefringences and phase is presented. This method is realized by dividing the output of the ac current signal with the modulation signal output. Using the technique the stability of the current sensor was improve dmore than 4.5 times at 800Arms for 2 hours. The current sensor also shows good linearity up to 100Arms.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.277-281
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• 2012

We measured small optical beam deflection in an image rotating Sagnac interferometer. We used a weak value measurement scheme that involves a pre-selection, weak perturbation, and a post-selection procedure to obtain the amplified value of beam deflection. The amplification factor of the measured beam deflection varied from 11 to 63 depending on the settings of the post-selection polarizer in front of the photodetector and the settings of polarization compensator in the interferometer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.234-237
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• 2002

To detect external vibration signals on the latticed fence structure, distributed fiber optic sensor using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 170cm in width and 180cm in height, the optical fiber, 50m in length, distributed and fixed on the latticed structure. It was verified the sensitivity of the Sagnac interferometer using the PZT phase modulator. Fiber optic external vibration signal spplied to the latticed fence structure from 100Hz to several kHz. The interferometeric fiber optic sensor detected the excited vibration signal very effectively without any signal processing. The detected optical signals were compared and analyzed to the detected acclerometer signals.