Fiber pressure sensors based on periodical mode coupling effects

Haim Lotem, Wen C. Wang, Michael Wang, David Schaafsma, Bob Skolnick, Haim Grebel

Research output: Contribution to journalConference articlepeer-review


Fiber optic sensor technology offers the possibility of implementing low weight, high performance and cost effective health and damage assessment for infrastructure elements. Common fiber sensors are based on the effect of external action on the spectral response of a Fabry-Perot or a Bragg grating section, or on the modal dynamics in multimode (MM) fiber. In the latter case, the fiber itself acts as the sensor, giving it the potential for large range coverage. We were interested in this type of sensor because of its cost advantage in monitoring structural health. In the course of the research, a new type of a rugged modal filter device, based on off-center splicing, was developed. This device, in combination with a MM fiber, was found to be a potential single point-pressure sensing device. Additionally, by translating the pressing point along a MM sensing fiber with a constant load and speed, a sinusoidal intensity modulation was observed. This harmonic behavior, during load translation, is explained by the theory of mode coupling and dispersion. The oscillation period, Λ∼0.43 mm, obtained at 980 nm in a Corning SMF-28™ fiber, corresponds to the wavevector difference, Δβ, between the two-coupled modes, Λ = 2π/Δβ. An additional outcome of the present research is the observation that the response of the loaded MM fiber is strongly dependent on the polarization state of the light traveling along the MM fiber due to different response of the modes to polarization active elements. Our main conclusions are that in MM fiber optic sensor design, special cautions need to be taken in order to stabilize the system, and that the sensitivity along a MM fiber sensor is periodic with a period of ∼ 0.4 - 0.5 mm, depending on various fiber parameters and excited modes.

Original languageEnglish (US)
Article number27
Pages (from-to)239-247
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2005
EventSmart Structures and Materials 2005 - Smart Sensor Technology and Measurement Systems - San Diego, CA, United States
Duration: Mar 7 2005Mar 9 2005

All Science Journal Classification (ASJC) codes

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


  • Accelerometer
  • Fiber sensor
  • Modal filter
  • Mode coupling
  • Pressure sensor
  • Structure health monitoring


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