We report the development of a temperature-insensitive pressure sensor based on a pair of fiber Bragg gratings (FBGs) embedded in a polyurethane diaphragm. The pressure is transversely applied, causing a bending on the diaphragm. In such condition, the FBGs are positioned in opposite directions considering the diaphragm bending’s neutral line as a reference. Thus, when the pressure is applied on the diaphragm, the wavelength shift occurs in opposite directions, i.e., one FBG has a blue shift and the other, red shift. The wavelength shift difference between both FBGs is analyzed, leading to a system with higher sensitivity when compared with the individual responses of each FBG. In addition, if the temperature sensitivities of each FBG are compensated, there is no difference in the wavelength shift (considering the difference between both FBGs) when the system is subjected only to temperature variations. However, if the system suffers simultaneous variation of temperature and pressure, there is a variation in the pressure sensitivity due to changes in the elastic modulus of the diaphragm caused by the temperature variations. For this reason, a compensation approach is proposed using the wavelength shift of each FBG as well as their difference. The sensor was tested for temperature, pressure and moisture absorption, where the maximum wavelength shift for the moisture absorption was 4 pm. For temperature and pressure responses, the sensor presented high sensitivity and linearity for all analyzed cases, leading to a pressure resolution of 1.75 Pa for constant temperature conditions. In pressure cycles under different temperatures, the compensation technique showed the feasibility of applying the proposed sensor in practical applications, where temperature variations as high as 30 °C were tested. The sensor presented a temperature cross-sensitivity of 0.33 Pa/°C.

我们报告了基于对嵌入在聚氨酯膜片中的一对光纤布拉格光栅（FBG）的温度不敏感压力传感器的开发。横向施加压力，导致隔膜弯曲。在这种情况下，以膜片弯曲的中性线为基准，将FBG定位在相反的方向。因此，当在膜片上施加压力时，波长偏移发生在相反的方向，即一个FBG发生蓝移而另一个FBG发生红移。分析了两个FBG之间的波长偏移差异，与每个FBG的单个响应相比，该系统具有更高的灵敏度。另外，如果每个FBG的温度灵敏度得到补偿，当系统仅受到温度变化时，波长偏移没有差异（考虑两个FBG之间的差异）。但是，如果系统同时受到温度和压力的变化，则由于温度变化引起的隔膜的弹性模量变化，压力灵敏度会发生变化。因此，提出了使用每个FBG的波长偏移及其差异的补偿方法。测试了传感器的温度，压力和水分吸收，其中水分吸收的最大波长偏移为4 pm。对于温度和压力响应，该传感器在所有分析情况下均具有很高的灵敏度和线性度，因此在恒定温度条件下的压力分辨率为1.75 Pa。在不同温度下的压力循环中，补偿技术显示了在实际应用中应用该传感器的可行性，该应用测试了高达30°C的温度变化。该传感器的温度交叉敏感度为0.33 Pa /°C。