Environmental Engineering Reference
In-Depth Information
Fig. 9.13 Experimental setup. PD Photodetector, PC Polarization controller, EOM Electro-optic
modulator, EDFA Erbium-doped fiber amplifier, DAQ Data acquisition
Fig. 9.14 Photo of the blade
fatigue test setup
was induced by the electric motor using single-axis resonance method. Figure
9.14
shows the photography of the blade fatigue test setup.
The layout of optic fiber sensors and strain gages on the blade is shown in
Fig.
9.15
. Polarization-maintaining optical fibers (PMF) were glued two circuits
on both sides of the blade surface, along the spanwise axis, to measure the lon-
gitudinal strain distribution. PMF can transmit optical power with very low loss
and maintain a stable performance over large temperature and strain range. Its
polarization-maintaining characteristic can remove the polarization fading of the
Brillouin signal and increase the SNR of the DPP-BOTDA system. In order to
increase the reliability of the optic fiber-sensing system, two optical fibers (Optical
Fiber 1 and Optical Fiber 2), of the same kind and length, went similar path on the
blade, monitoring the similar place with two lines of the single optical fiber.
Simultaneously, eight strain gauges are patched on the surface of the composite
