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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.

, "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.

The significance of etched single-mode polymer optical fibers and their potential for the development of highsensitivity sensors are presented. A polymethyl methacrylatebased single-mode polymer optical fiber is etched to various 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. This can play a vital role in improving the intrinsic sensing capabilities of sensors based on etched polymer optical fiber. To demonstrate that the modified material properties of the etched polymer fiber can enhance its intrinsic sensing capabilities, sensing characteristics of etched polymer fiber Bragg gratings for strain, temperature, and pressure are obtained. From the results, it is confirmed that the sensors based on etched polymer fibers exhibit high intrinsic sensitivity compared with un-etched ones. The potential of developing a sensing system for simultaneous measurement of strain and temperature is also demonstrated.