Fiber-optic simultaneous distributed monitoring of strain and temperature for an aircraft wing during flight.

We applied a fiber optic distributed simultaneous strain and temperature measurement technique to the structural monitoring of the main wing of a middle-sized passenger jet aircraft during flight. We used 40 10 cm long fiber Bragg gratings (FBGs), inscribed in a highly birefringent polarization-maintaining fiber. The FBGs were interrogated by optical frequency domain reflectometry, which could measure Bragg wavelength distributions at a sampling rate of 151 Hz. The simultaneous measurement technique could detect structural behaviors of the wing during flight under temperature-changing conditions. In addition, we discuss the effect of the polarization mode-coupling and the apparent position shift of the FBGs over time, which occurred during flight.