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NONCONTACT DETECTION OF ULTRASONIC WAVES USING FIBER OPTIC

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					Number:     558

Title:      NONCONTACT DETECTION OF ULTRASONIC WAVES USING
            FIBER OPTIC SAGNAC INTERFEROMETER
Authors:    Tae Seong Jang, Seung Seok Lee, Il Bum Kwon, Wang Joo Lee, and
            Jung Ju Lee
Citation:   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency
            Control, Vol. 49, No. 6, pp. 767-775, June 2002
Keywords:   ultrasonics

Abstract:   This paper describes a fiber optic sensor suitable for noncontact detection
            of ultrasonic waves. This sensor is based on the fiber optic Sagnac
            interferometer, which has a path-matched configuration and does not
            require active stabilization.      Quadrature phase bias between two
            interfering laser beams in the Sagnac loop is applied by controlling the
            birefringence using a fiber polarization controller. A stable quadrature
            phase bias can be confirmed by observing the interferometer output
            according to the change of phase bias. Additional signal processing is not
            needed for the detection of ultrasonic waves using the Sagnac
            interferometer.      Ultrasonic oscillations produced by conventional
            ultrasonic piezoelectric transducers were successfully detected, and the
            performance of this interferometer was investigated by a power spectrum
            analysis of the output signal. Based on the validation of the fiber optic
            Sagnac interferometer, noncontact detection of laser=generated surface
            waves was performed. The configured Sagnac interferometer is very
            effective for the detection of small displacement with high frequency, such
            as ultrasonic wave used in conventional nondestructive testing (NDT).

Pro/Cons:   The proposed fiber optic Sagnac interferometer is effective for noncontact
            detection of ultrasonic waves and can be applied for the detection of
            surface acoustic waves and any other ultrasonic measurements.

				
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posted:3/13/2010
language:English
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