Our systems for bridges utilize sensors with fiber Bragg gratings

  • Established technology, internationally proven
  • High resolution, accurate, field-reliable
  • Small, lightweight, easy to surface-mount or embed into structures
  • Simultaneous, real-time point sensing at speeds up to kHz
  • Static and dynamic measurements with single instrument
  • Wide temperature range:  –65 to +300°C for standard fiber
  • Radiation hardened fiber available
  • Multiplexing –   up to 40 –50 sensors per channel on a single fiber, regardless of sensor type
FBG Construction
  • Using an intense UV source or high-power laser, a grating pattern is permanently “written” into a section of the glass fiber
  • For broadband light input into fiber, the FBG reflects back one wavelength, called l Bragg
  • All other wavelengths pass through FBG thus acts as a spectrally selective mirror
  • Wavelength of Bragg is determined  by the spacing (period) of the pattern
FBG Strain and Temperature Measurement
  • Glass fiber is slightly elastic, so FBG can stretch
  • If FBG stretches or changes temperature, FBG pattern pitch changes, causing l Bragg to shift
  • Bragg is continuously sensed using an optical interrogator
  • Bragg may be calibrated to quantify temperature and strain values
Multi-point Sensing on One Fiber
  • Multiple FBGs, each tuned to a different l Bragg, may be written on one fiber
  • FBGs operate independently and may be multiplexed on one fiber