Refractometric sensor based on a phase-shifted long-period fiber grating

Abstract

A refractometric sensor based on a phase-shifted long-period fiber grating written by electric-arc discharges is presented. Transmission and reflective configurations for refractive index measurements are studied. It is observed that the reflective topology permits better performance compared with the transmission one, which is the approach normally utilized in the context of long-period fiber sensing. The resolution achieved in the measurement of refractive index enables the application of this sensing head structure in demanding situations, such as the measurement of the level of salinity of water.

Tapered fiber Mach–Zehnder interferometer for simultaneous measurement of refractive index and temperature

“…2,4 Besides the approach with evanescent waves from nanometer fiber tips coated with gold particles, 5 a majority of fiber sensors for refractive index measurement utilized fiber gratings, i.e., long-period gratings ͑LPGs͒ and fiber Bragg gratings ͑FBGs͒. Recent work that reported refractive index measurement with LPGs are either gold coated, 6 arc-induced phase shifted, 7 asymmetric, 8 or inscribed in air-and water-filled photonic crystal fibers. 9 Reported refractive index measurement with FBGs includes a metal-coated grating in a special single-mode fiber of larger core ͑26 m͒ and thinner cladding ͑30 m͒, 10 a tilted FBG with gold coating in single-mode fiber, 11 and cladding mode resonances of etched-eroded FBG.…”

Fibre Sensing System Based on Long-Period Gratings for Monitoring Aqueous Environments

“…Gratings inscription was also achieved through the use of thermal effects by exposure to near-IR carbon-dioxide (CO 2 ) laser light (Davis et al, 1998;Kim et al, 2002) or electric arc discharges (Rego et al, 2001;Falate et al, 2006). Both techniques allow the inscription of the gratings without the need hydrogen-loaded or Ge-doped core fibres and are more flexible than the UV technique since it is not required the fabrication of a specific amplitude mask for each desired resonance wavelength (Humbert & Malki, 2003).…”

Oligonucleotide-Hybridization Fiber-Optic Biosensor Using a Narrow Bandwidth Long Period Grating

“…In general, the sensitivity will change for LPGs fabricated with different parameters, and it will also be different for each resonance of the same LPG, depending on the dispersion curve of the cladding modes involved in the coupling. Refractometers, solution concentration sensors and E. Coli biosensors have been demonstrated based on this sensing principle [12][13][14][15].…”