Experimental Study and Analysis of Hydrostatic Pressure Sensitivity of Polymer Fibre Bragg Gratings

Abstract

The intrinsic hydrostatic pressure sensitivity of polymer optical fibre Bragg grating (POFBG) with different diameters are investigated. POFBGs are inscribed in singlemode polymer fibre and etched down to different diameters. We have experimentally demonstrated that the material properties of the polymer optical fibre can change after etching and thus the etching procedure can have an impact on the pressure sensitivity of the POFBG. It is observed from the experimental results that hydrostatic pressure induce a positive wavelength shift to the POFBG and the pressure sensitivity of the POFBG shows significant increase as the fibre diameter reduces through etching. A pressure sensitivity of 0.20 pm/kPa is obtained for an un-etched POFBG while for an etched POFBG with 55 µm diameter a sensitivity of 0.75 pm/kPa is observed. Temperature compensation techniques are also successfully implemented to extract the true intrinsic pressure sensitivity of the POFBG. Through this study, the intrinsic pressure sensitivity of POFBG with different diameters are obtained and also the significance of etching and its impact on pressure sensitivity is demonstrated. This information can lead to further research and development on high sensitivity pressure transducers based on etched POFBGs.

Phase-Shifted Bragg Grating Inscription in PMMA Microstructured POF Using 248-nm UV Radiation

“…As Young's modulus of the polymer fibe (∼2.9 GPa) is much lower than that of silica fibe (∼70 GPa), the pressure sensitivity of sensors based on POF could be comparatively higher than that of silica fibe [55]. It should be noted that, in the case of a silica FBG, the hydrostatic pressure induced grating period change (strain effect) dominates the change in refractive index and as a result a negative sensitivity is observed [55], [56]. While for a POFBG, the dominant effect is the refractive index change than the grating period change and as a result the sensitivity becomes positive as shown in Fig.…”

“…4(c) we observe that there is a linear shift of the center wavelengths of the two dips with increasing/decreasing pressure, with a sensitivity of 0.46 ± 0.03 pm/kPa, which is 2 times more sensitive than a uniform POFBG [54]. As Young's modulus of the polymer fibe (∼2.9 GPa) is much lower than that of silica fibe (∼70 GPa), the pressure sensitivity of sensors based on POF could be comparatively higher than that of silica fibe [55]. It should be noted that, in the case of a silica FBG, the hydrostatic pressure induced grating period change (strain effect) dominates the change in refractive index and as a result a negative sensitivity is observed [55], [56].…”

Effects of pre-strain on the intrinsic pressure sensitivity of polymer optical fiber Bragg gratings

“…Previous research includes POFBGs for strain 1,2 , temperature 3,4 and humidity 5,6 sensing, but also investigations towards measuring hydrostatic pressure have been carried out [7][8][9] . These investigations show that, contrary to FBGs in silica fibers, the pressure response in POFBGs is positive, i.e.…”

Characterization of Polymer Fiber Bragg Grating With Ultrafast Laser Micromachining

“…Due to its unique properties, PMMA has become one of the most common polymers used for the fabrication of gratings and waveguides. PMMA-based optical fiber Bragg gratings (POFBGs) were found to be sensitive to relative humidity, temperature, strain and pressure with high sensitivity [8][9][10][11]. The sensing response time of POFBGs can be significantly improved either by reducing the fiber diameter with chemical etching [9] or by spatial modification of fiber geometry using laser micromachining [12].…”