• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.55-59
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• 2000

Nonlinearity is one of the primary causes of error in precision length measurement using laser interferometer. It arises periodically. The periodical nonlinearity usually ranges from sub-naometre to several namertres. In the homodyne interferometer, it results from a number of factors including polarization mixing, imperfect optical clement, unequal gain of detectors, misalignment of axes between input beam and beam splitter. In this paper, we described a method for measuring and compensating the nonlinearity of homodyne interferometer using the elliptical least-square fitting technique associated with electric method and experimental results in one frequency polarization interferometer.

• Journal of KSNVE
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• v.7 no.6
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• pp.931-936
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• 1997

Optical fiber sensor is a subject which has been attracted considerable attention in recent years. Detection of sound pressure with optical fibers positioned in the arms of a Mach-Zehnder interferometer is presented in this paper. A fiber length of the order of 150m is wounded is made by hollow cylinder type. To increase the sound signal 3${\times}3$ directional coupler is used. Fiber optic hydrophone is the underwater tank with 2kHz sound source. Finally, it is shown that the fiber optic hydeophone can stably detec 2kHz sound.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.397-402
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• 2003

The FM demodulation method for a bulk homodyne laser interferometer is presented. The Doppler frequency that represents the surface velocity of a vibrating object is obtained by using the bulk homodyne laser interferometer, and converted to the voltage signal by using the proposed analogue FM demodulation circuit. The DC offsets of the interferent signals that are obtained from the bulk homodyne interferometer are eliminated by using a simple subtraction. The new method for compensation of the asymmetry of each channels is presented. The light power variation of the interferometer is normalized by using the Auto Gain Controller(AGC). The proposed FM demodulation algorithm is proved by the theoretical method, and validated by the experimental results. In experiments, the proposed FM demodulation algorithm is compared with the conventional demodulation methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.373-378
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• 2007

On the homodyne interferometers, high pass filter(HPF) is usually used to remove the electrical noise in the interferent signal. Heterodyne interferometer has modulating frequency is shifted in the frequency region where the electrical noise effect is minimized by HPF effect. However, on the homodyne interferometer, the interferent DC-component of homodyne interferometer is unfortunately eliminated by using a HPF because its shifted frequency does not exist. Moreover, this effect is more serious the vibration amplitude is smaller. So, when unstable interferent signals via HPF are demodulated, a velocity is distorted. In this work, the mathematical explanation for the distortion of the homodyne interferent signal using the HPF is given. New synthetic heterodyne LDV based on the homodyne interferometer by exciting the reference mirror is proposed for the cancellation of the distortion. The optimum excitation condition of the mirror to compensate the distortion is discussed. The numerical simulation using the commercial MATLAB code is provided to show the effect of the proposed synthetic heterodyne LDV. The experimental results are also given and the effect of the proposed LDV is discussed.