Instrumentation for interrogating many-element fiber Bragg grating arrays

Fiber Bragg grating (FBG) arrays have provided the Smart Structures community with a powerful means for real-time and absolute point measurements of strain throughout extended structures. The mechanical properties of these optical fiber sensors uniquely suit them for unobtrusive and reliable incorporation into composite materials, while wavelength encoding of the measurand enables independent interrogation of many devices distributed along a single fiber. In view of recent progress towards practical and economical FBG array fabrication via the computer-controlled in-line writing process during fiber draw, there is a complementary need for economical instrumentation which makes efficient use of the reflected signals. This is an important issue, especially since the reflectivity of narrow-line, type I gratings produced during fiber draw is typically less than 5%.