Optical Fiber Sensor Based on Air-Gap Long-Period Fiber Gratings

Abstract

In this work, we propose a novel fiber sensor that is based on an air-gap long-period fiber grating (AG-LPG), which is fabricated by combining fiber side polishing with fiber lithography. Its sensing mechanism is based on the loss-peak wavelength shift of the AG-LPG as the refractive index around the sensing head varies. Experimental results show that the maximum sensitivity is 620 nm/unit index (1.1 nm/%) in the sensing of various sugar solution concentrations. This novel sensing head provides a simple, reliable, repeatable, accurate, and nondestructive approach for detecting various chemical solutions and mixing gases and for biomedical applications.

Long Period Gratings in New Generation Optical Fibers

“…4 shows the original LPG transmission spectrum and that obtained after polishing: a red shift in the range of several nanometres is observable. Finally, special attention has to be dedicated to the air-gap LPG (AG-LPG) first proposed in 2009 (Fu et al, 2009). Differently from standard UV written LPGs, in fact, here the grating is an axially periodic structural modification of the core layer (periodic AGs).…”

“…The double-sided-polished D-fiber LPG was also proposed for liquid RI measurements in the bare configuration (Tien et al, 2009b), revealing a maximum SRI sensitivity of 143.396 nm/RIU. To complete the intra-core LPGs category, the applications of AG-LPGs needs to be mentioned: first, they were tested for SRI measurements (Fu et al, 2009). Fig.…”

Glucose Sensor Using U-Shaped Optical Fiber Probe with Gold Nanoparticles and Glucose Oxidase

“…The sensor sensitivity concentration of MRR1 (the first ring) was 35.2 ± 7.11 pm/%, while that of MRR2 (the second ring) sensor was 98.3 ± 8.19 pm/%. In 2009, Fu [ 4 ] presented a long cycle sugar water sensor fabricated using a 410-µm long raster of a single-mode fiber, SMF28. In 2009, Binu presented another fiber sensor probe used for glucose measurements [ 5 ].…”

Fabrication of Long Period Gratings by Periodically Removing the Coating of Cladding-Etched Single Mode Optical Fiber Towards Optical Fiber Sensor Development

“…Regarding the fabrication, the most well-known method for inscription of LPGs is a core RI change induced by UV laser radiation in standard communication fibers [ 1 ]. However, several other mechanisms have been exploited to obtain this optical structure: CO 2 [ 24 ] and IR femtosecond laser radiation [ 25 ], ion beam irradiation [ 26 ], etching [ 27 , 28 ], mechanically induced gratings [ 29 ], and electric arc discharges [ 30 ]. Besides, different kinds of fibers have been used for the development of this optical structure, such as standard single mode optical fibers (SMF28) [ 6 ], hydrogen loaded fibers [ 31 , 32 ], and Ge doped [ 33 ] and B/Ge co-doped fibers [ 30 ].…”

“…Other methods, based on lithography or wet-etching processes, have recently been used for the fabrication of the so-called corrugated LPGs [ 27 , 28 , 34 , 35 , 36 , 37 , 38 ]. During these processes, sections with different effective indices ( n eff ) were obtained by periodically decreasing the cladding diameter.…”