High Intrinsic Sensitivity Etched Polymer Fiber Bragg Grating Pair for Simultaneous Strain and Temperature Measurements

Abstract

, "High intrinsic sensitivity etched polymer fiber Bragg grating pair for simultaneous strain and temperature measurements," IEEE Sensors Journal, vol. 16, (8) pp. 2453-2459, 2016 High intrinsic sensitivity etched polymer fiber Bragg grating pair for simultaneous strain and temperature measurements Abstract A sensing configuration for simultaneous measurement of strain and temperature with enhanced intrinsic sensitivity based on a fiber Bragg grating (FBG) pair with one grating inscribed in the etched and the other in unetched polymer fiber region is demonstrated. A poly (methyl methacrylate) based single-mode polymer fiber is etched to different diameters, and it is observed that etching can lead to change in the material properties of the fiber, such as Young's modulus and thermal expansion coefficient, which can play a vital role in improving its intrinsic sensing capabilities. Thus, exploiting the different strain and temperature sensitivities exhibited by etched and unetched polymer FBGs, strain and temperature can be simultaneously measured with very high sensitivity. Experimental results show that rms deviations of ±8.42 μ∈ and ±0.39 °C for strain and temperature, respectively, in a real simultaneous measurement. The effect of individual thermal and strain sensitivity coefficients on measurement accuracy is also analyzed. Abstract-A sensing configuration for simultaneous measurement of strain and temperature with enhanced intrinsic sensitivity based on a fibre Bragg grating pair (FBG) with one grating inscribed in the etched and the other in un-etched polymer fibre region is demonstrated. A PMMA based singlemode polymer fibre is etched to different diameters and it is observed that etching can lead to change in the material properties of the fibre such as Young's modulus and thermal expansion coefficient, which can play a vital role in improving its intrinsic sensing capabilities. Thus, exploiting the different strain and temperature sensitivities exhibited by etched and un-etched polymer FBGs, strain and temperature can be simultaneously measured with very high sensitivity. Experimental results show that rms deviations of ± 8.42 µϵ and ± 0.39 0 C for strain and temperature respectively in a real simultaneous measurement. The effect of individual thermal and strain sensitivity coefficients on measurement accuracy is also analysed.

Fibre Bragg Grating Based Strain Sensors: Review of Technology and Applications

“…On the other hand, the FBG filter in a ring laser cavity configuration achieved a resolution of 700 nε and a sensitivity of 74.5 pm/με. The sensor configuration of Reference [ 54 ] is based on a FBG pair (with different Bragg wavelengths): one of them is etched while the other shows an un-etched region of polymer fibre (POF). The strain has been applied by using a translation stage in order to measure the sensitivity.…”

Thermal and chemical treatment of polymer optical fiber Bragg grating sensors for enhanced mechanical sensitivity

“…A Youngs modulus reduction has been reported when a PMMA optical fiber was chemically etched with acetone [17]. The authors claimed that one possible reason for the material property changes could be the molecular chain relaxation due to solvent absorption.…”

“…This is because the distance between the fiber surface exposed to the external environment and the fiber core is less, which can reduce the time that water requires to reach the Bragg gratings location and be detected. However, recently it was shown that etching PMMA with acetone can change not only the physical dimensions of the POF, but also its material properties, such as its Youngs modulus [17].…”

Bandpass transmission filters based on phase shifted fiber Bragg gratings in microstructured polymer optical fibers

“…However, since the first polymer FBG reported in 1999 [22], several promising devices, mainly for the measurement of strain and temperature using step-index fiber and micro-structured fiber have been demonstrated [23][24][25]. Despite of this, for the inscription of the grating, the photosensitivity of the material is important; so far great advances have been done both in doped [26][27][28] and undoped fibers [29], but grating time stability is still an issue if the FBG is not properly annealed [24,30].…”