Simultaneous independent measurement of strain and temperature based on long-period fiber gratings inscribed in holey fibers depending on air-hole size.

We propose and experimentally demonstrate a simple and flexible scheme for the simultaneous measurement of strain and temperature using long-period fiber gratings (LPFGs) based on versatile holey fibers (HFs) with different air-hole sizes. The strongly resonant LPFGs (as much as approximately 24 dB) can be successfully achieved. The LPFGs inscribed in the HFs have similar temperature sensitivities regardless of air-hole size because of the same material composition. The strain sensitivities of the LPFGs, however, are different, since holey fibers have different cross-sectional areas depending on the air-hole size. The strain sensitivities of the HF-based LPFGs are enhanced by a factor larger than 2 as the air-hole size increases.