Development of integrated optic pressure sensors with high sensitivity and high withstanding pressure for tsunami detection

该传感器基于传统的集成光学压力传感器，采用多式联运干涉，在膜片底部增加了一个半封闭空间和一个小孔。通过增加这个半封闭的空间，传感器不同于传统的传感器，可以承受高静压。当环境压力突然变化时，由于限制流体流动的小孔，半封闭空间内的压力无法快速调节。所以压力差会在隔膜上产生一小段时间。因此，传感器只对压力变化有响应，而对静压没有响应。在这个研究项目的第一年，我们检查了传感器的阶跃响应，即突然压力变化的输出特性。所制备传感器的膜片尺寸为14mm×14mm×0.22mm，半封闭空间的体积为14mm×14mm×1.8mm。一个小矩形孔的截面积为93μm×25μm。在这个实验中，在一个30cm×28cm×30cm封闭的盒子里，制作的传感器被放置，压力突然增加了0.78 kPa。由于压力的变化，输出强度下降了大约20%的初始强度水平。在压力阶跃变化后约1.4秒，输出强度恢复到初始水平。第二年，从理论分析中发现，诱导压差持续时间与半封闭空间体积与小孔截面积的V/A比成正比，与初始压差的平方根成正比。因此，通过实验研究了小孔截面积与持续时间的关系。圆孔半径分别为20μm、25μm和40μm。当环境压力突然变化0.7 kPa时，测量到的诱导压差持续时间约为2秒，但根据理论结果，持续时间必须与孔半径有关。这是由于放置传感器的封闭盒子的压力泄漏造成的。少

The proposed sensor is based on a conventional integrated optic pressure sensor using intermodal interference, with an added semi-closed space with a small hole under the bottom side of the diaphragm. By the addition of this semi-closed space, the sensor, unlike conventional sensors, can withstand high static pressure. When there is a sudden change in ambient pressure, pressure within the semi-closed space cannot quickly adjust due to the small hole that restricts fluid flow. So, pressure difference is induced on the diaphragm for a short while. Thus, the sensor shows a response only to changes in pressure, not to static pressure.In the first year of this research project, we examined the step response of the sensor, that is, the output characteristics for sudden pressure change. The diaphragm dimensions of the fabricated sensor were 14mm×14mm×0.22mm, and the volume of the semi-closed space was 14mm×14mm×1.8mm. The sectional area of a small rectangular hole was 93μm×25μm. In this exper … More iment, the pressure in a 30cm×28cm×30cm closed box, in which the fabricated sensor was placed, was suddenly increased by 0.78 kPa. Due to the pressure change, the output intensity decreased by approximately 20% of the initial intensity level. Approximately 1.4 sec after the step-like change in pressure, output intensity returned to the initial level.In the second year, it was found from the theoretical analysis that the duration of the induced pressure difference is proportional to the V/A ratio between the volume of the semi-closed space and the sectional area of the small hole, and proportional to the square root of the initial pressure difference. So, the relationship between the duration and the sectional area of the small hole was examined experimentally. The radii of the circular holes were 20μm,25μm, and 40μm. The measured duration of the induced pressure difference was approximately 2 sec when the ambient pressure was suddenly changed by 0.7 kPa, although the duration must be dependent on the hole radius according to the theoretical results. It is attributed to pressure leak from the closed box in which the sensor was placed. Less