Enhanced pressure and thermal sensitivity of polymer optical fiber Bragg grating sensors. (October 2020) - Woyessa, Getinet
Highlights: POF grating pressure and temperature sensitivities are enhanced by pre-straining. The pressure sensitivity of POF grating is improved by a factor of five. The temperature sensitivity of POF grating is boosted by more than a factor of ten. The sensitivity enhancement is stable above a certain threshold of pre-strain. Pre-straining enable well-conditioned simultaneous measurements with dual gratings. Abstract: One of the features of reliable polymer optical fiber (POF) Bragg grating sensors is high sensitivity. Towards this, we have investigated a method to enhance the intrinsic pressure and thermal sensitivity of fiber Bragg grating (FBG) sensors inscribed in POFs. By pre-straining the FBG we demonstrated that: (1) the pressure induced mechanical contraction of the fiber can be suppressed, resulting in an increase in the pressure sensitivity of the grating by a factor of 5; and (2) the temperature induced strain can be suppressed, resulting in an increase in the thermal response by more than a factor of 10. The pressure sensitivity enhancement was found to be independent of the amount of pre-strain for levels ranging from 0.07 to 0.33%. The enhancement of the temperature sensitivity was also found to be independent of the amount of pre-strain, but only for temperatures up to when the thermal expansion cancels the pre-strain.