Intrinsic fiber-optic Sagnac ultrasound sensor for process monitoring in composite structures

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

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


In this paper, we report the development of an intrinsic fiber-optic Sagnac-type ultrasound sensor for cure monitoring. The Sagnac ultrasonic sensor consists of a Sagnac demodulation unit and a sensing segment which can be embedded in a composite structure. The Sagnac optical demodulator is common-path and hence self-stabilized and much simpler than the alternate Fabry-Perot or Michelson type sensors which require external stabilization. Any phase variations that the sampling beams experience due to ultrasound impinging on the sensing segment are demodulated by the Sagnac sensor to produce a signal proportional to ultrasonic signal. The sensing fiber segment of the Sagnac is placed within the composite at the time of manufacture. As the composite is cured, this sensor detects ultrasound that is generated by a laser source or a pzt-transducer. The wavespeed and attenuation of the ultrasound are measured as the cure process proceeds, and these provide information on the state of cure of the composite. We discuss the details of the above intrinsic Sagnac sensor, as well as report on its characteristics including frequency response, sensitivity, and directionality. Results of a cure monitoring are also presented.

Original languageEnglish (US)
Pages (from-to)156-159
Number of pages4
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Mar 3 1999
EventProceedings of 1999 Process Control and Sensors for Manufacturing II - Newport Beach, CA, USA
Duration: Mar 3 1999Mar 4 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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