This paper presents the results of the analysis of acoustic emission signals registered by using fiber-optic sensors during the propagation of ultrasonic waves in a polymer composite material. Fiber-optical sensors for acoustic emission were constructed according to the scheme of an adaptive holographic interferometer. Unlike piezoelectric sensors, fiber-optic sensors are distributed type sensors. This imposes certain features on the detection of signals in plates in which fiberoptic sensors are embedded. It is established that the difference of the spectrum of acoustic emission signals registered in different directions of wave propagation. The local maximums of the spectrum are determined by the mode of wave propagation in the plate in different directions and the location of fiber-optic sensors.
In this paper, we propose a theoretical model of vectorial two-wave mixing in optically active photorefractive cubic crystals of the point group 23 and 43m in orthogonal geometry. Proposed model takes into account polarization states of coupling waves, their dependence on the location in the crystal, orientation of wave vectors relative to the main crystallographic axes and optical activity of a crystal. Sets of the wave parameters which provide either a maximum efficiency of wave coupling or wave coupling efficiency insensitive to polarization state of signal wave are found with use of proposed model.
The paper presents the results of an analysis of the acoustic emission signals recorded both by piezoelectric and adaptive fiber-optical sensors. Fiber-optical sensors have been embedded into the polymer composite material during their manufacture. Fiber-optical sensors are designed on the base of adaptive interferometer that uses a dynamic hologram formed in the photorefractive crystal. It has been shown that the sensitivity of adaptive interferometer allows the detection of acoustic emission signals generated by the Hsu-Nielsen source. Peculiarities of material sound velocity determination with use of acoustic signals detected by distributed fiber-optical sensors are discussed.
We present the multichannel fiber-optical system for detection and reconstruction of weak acoustic field. Developed system is based on 32-channel adaptive holographic interferometer that employs multiplexing of dynamic holograms in a single photorefractive crystal of CdTe. The multichannel fiber-optical sensory system was tested for registration and spatial reconstruction of acoustic field created in a solid plate.
In this paper, we developed and investigated an adaptive fiber-optic hydrophone based on adaptive holographic interferometer which key element is dynamic hologram recorded in a photorefractive crystal of cubic symmetry in orthogonal geometry. Different modifications of primary fiber-optic receivers of acoustic pressure are designed and studied. The adaptive hydrophone provides high sensitivity to acoustic pressure (up to 8.6 mV/Pa) and high level of immunity to all kind of noisy instabilities of environment.
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