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This Letter presents simulation and experimental results of orientation-dependent transverse stress fiber sensors using fiber Bragg gratings (FBGs) inscribed in four-hole suspended-core fibers. Resonant peak shifts and splitting of FBGs were studied as functions of the applied transverse load and fiber orientation. Both simulation and experimental results revealed that the response of FBGs in suspended-core fibers is sensitive to both the orientation and magnitude of an applied transverse stress.

The idea of Bragg gratings generated during the drawing process of a fiber dates back almost 20 years. The technical improvement of the draw tower grating (DTG) process today results in highly reliable and cost-effective Bragg gratings for versatile application in the optical fiber sensor market. Because of the single-pulse exposure of the fiber, the gratings behave typically like type I gratings with respect to their temperature stability. This means that such gratings only work up to temperatures of about 300 °C. To increase temperature stability, we combined DTG arrays with hydrogen postloading and a thermal regeneration process that enables their use in high-temperature environments. The regenerated draw tower gratings are demonstrated to be suitable for temperatures of more than 800 °C. © 2011 Optical Society of America.