For many years, fiber manufacturers have devoted research efforts to develop fibers with improved radiation
resistance, keeping the same advantages and basic properties as standard fibers. Today, both single-mode (SMF) and
multimode (MMF) RadHard (for Radiation-Hardened) fibers are available; some of them are MIL-49291 certified and
are already used, for example in military applications and at the Large Hadron Collider (LHC) in CERN or in certain
nuclear power plants. These RadHard fibers can be easily connected to standard optical networks for classical data
transfer or they can also be used for command control. Using some specific properties (Raman or Brillouin scattering,
Bragg gratings...), such fibers can also be used as distributed sensing (temperature or strain sensors, etc) in radiation
environments. At least, optical fibers can also be used for signal amplification, either in telecom networks, or in fiber
lasers. This last category of fibers is called active fibers, in opposition to passive fibers used for simple signal
transmission. Draka has also recently worked to improve the radiation-resistance of these active fibers, so that Draka can
now offer RadHard fibers for full optical systems.
The application of electro-optic holography (EOH) for measuring the center bay vibration modes of an aircraft fuselage panel under forced excitation is presented. The requirement of free-free panel boundary conditions made the acquisition of quantitative EOH data challenging since large scale rigid body motions corrupted measurements of the high frequency vibrations of interest. Image processing routines designed to minimize effects of large scale motions were applied to successfully resurrect quantitative EOH vibrational amplitude measurements from extremely noisy data. EOH and scanning laser doppler vibrometer results have been used to validate and update finite element models of the fuselage panel. Various modeling techniques were evaluated for characterization of the panel normal modes at frequencies up to 1000 Hz. These models are briefly described, and comparisons between computational predictions and experimental measurements are presented.