Development of new synthetic-heterodyne in sinusoidal phase modulation for optical fiber sensors

Y. L. Lo, C. H. Chuang

Research output: Contribution to journalConference articlepeer-review


In this study a new algorithm for modulating a PZT stack using a sine-wave signal instead of a saw-tooth signal was developed in order to resolve the flyback problem in a PZT driver. An improved synthetic heterodyne demodulator circuit was designed and arranged to interrogate the output signal from an interferometric sensor with a sine-wave modulation (phase-generated carrier). A depth of modulation or a gain amplifier to the circuit design was adjusted such that the standard heterodyne signal could be formed. The result is a conventional PM modulated carrier that can be demodulated using standard techniques, followed by a lock-in amplifier or a phase meter, to recover the phase shift in the sensing information. Implementing it into a path-matching differential interferometer (PMDI) for the signal modulation validates this new method. The new synthetic heterodyne is applied to a differential optical fiber refractometer for measuring the refractive index change. A lock-in amplifier is chosen as the demodulator to extract the phase shift. Therefore, the resolution of this sensing system is 7.52 × 10-7 refractive index unit (RIU) in 120 μm length of the sensing cavity.

Original languageEnglish
Pages (from-to)15-22
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 2001 Jan 1
EventSmart Structures and Materials 2001- Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials - Newport Beach, CA, United States
Duration: 2001 Mar 52001 Mar 6

All Science Journal Classification (ASJC) codes

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


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