Extrinsic and intrinsic fiber optic Sagnac ultrasound sensors

Pavel A. Fomitchov, Sridhar Krishnaswamy, Jan D. Achenbach

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


A compact, dual-probe, fiberized Sagnac ultrasound sensor (SUS) capable of detecting ultrasonic waves of various types is described. The main advantages of the proposed device are (1) the ability to detect ultrasonic waves on the surface (extrinsic mode) as well as in the interior of structures (intrinsic mode); (2) improved SNR, which has been achieved using an optical frequency shifting technique for biasing to quadrature and for elimination of parasitic interference between the desired sampling beams and other nonessential beams in the interferometer; (3) the ability to detect ultrasonic signals on rough surfaces by the use of an electromechanical speckle-hunting technique (in the extrinsic mode); (4) dual-probe configuration; and (5) directional sensitivity to ultrasound when the system is operated in the intrinsic mode or on a polished surface in the extrinsic mode. Several applications of the SUS for nondestructive characterization of material properties and testing of structures for flaws are presented. Bulk longitudinal waves, Rayleigh waves and Lamb waves are measured using the SUS to (1) characterize piezoelectric ultrasonic transducer beam profiles, (2) study the scattering of ultrasonic waves by flaws, (3) identify and size surface breaking flaws in aircraft wheel components, and (4) monitor in real time the cure process of an epoxy resin.

Original languageEnglish (US)
Pages (from-to)1972-1984
Number of pages13
JournalOptical Engineering
Issue number7
StatePublished - Jul 1 2000

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering(all)


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