Abstract
We report on the investigation of the sensing features of the Long-Period fiber Gratings (LPGs) fabricated in hollow core photonic crystal fibers (HC-PCFs) by the pressure assisted Electric Arc Discharge (EAD) technique. In particular, the characterization of the LPG in terms of shift in resonant wavelengths and changes in attenuation band depth to the environmental parameters: strain, temperature, curvature, refractive index and pressure is presented. The achieved results show that LPGs in HC-PCFs represent a novel high performance sensing platform for measurements of different physical parameters including strain, temperature and, especially, for measurements of environmental pressure. The pressure sensitivity enhancement is about four times greater if we compare LPGs in HC and standard fibers. Moreover, differently from LPGs in standard fibers, these LPGs realized in innovative fibers, i.e., the HC-PCFs, are not sensitive to surrounding refractive index.
Highlights
The need for real time, in situ monitoring of physical, chemical and biological parameters is increasing in various commercial and defense fields
Long-Period Gratings (LPGs) are formed by longitudinal periodic refractive index and/or structural modulation along an optical fiber that have periods typically in the range 100 μm to 1 mm, and they promote coupling between the propagating core mode and co-propagating higher order modes [5]
This paper presented and discussed the sensing features of recently fabricated long period grating in hollow core fibers
Summary
The need for real time, in situ monitoring of physical, chemical and biological parameters is increasing in various commercial and defense fields. LPGs are formed by longitudinal periodic refractive index and/or structural modulation along an optical fiber that have periods typically in the range 100 μm to 1 mm, and they promote coupling between the propagating core mode and co-propagating higher order modes [5] These modes decay rapidly as they propagate along the fiber axis resulting in the transmission spectrum containing a series of attenuation bands centered at discrete wavelengths, corresponding to the coupling with a different cladding mode. It is worth noting that, differently from LPGs in standard fibers, these novel gratings are not sensitive to surrounding refractive index, whereas LPGs in standard fibers received the most of Their popularity in (bio)chemical application field thank to this sensing feature itself. Not yet investigated, we believe that this limitation can be overcome by taking advantage by the air core characteristic of the hosting hollow core fiber, as proposed by recent papers [9]
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