Research of a Next-Generation Laser Tsunami Measurement Network system

采用基于光频域反射的光纤传感器和频移反馈激光器，研制了一种用于海底海啸光学测定仪的光学液压计。通过测量光纤的光程长度，计算出液压压力。该传感器由一根870 m长的裸色散位移光纤卷绕在空心圆柱形铝筒子上组成，其压力灵敏度为-2.34 10^<-11> /Pa。振荡波长为1.55 μm的频移反馈激光器测量距离的精度为10^<-9>。该系统测压精度为62 Pa，对应深度为6.2 mm，可满足海啸测量的要求。此外，利用反向传播技术分析估计了海啸的场传播源。该方法在两个海底海啸米左右分别画出第一波海啸的最高高水位点和零交点的波峰线，并估计其交点为起源区域。通过对环太平洋海啸台网的模拟，在夏威夷群岛的周长上加入海底海啸米，可以估计出一个起源地，误差小于20%。在我国沿海地区，海啸夺去了许多人的生命，并经常造成严重的物质损失。及时提供准确的信息对减轻海啸损害是不可或缺的。利用频移反馈激光对激光液压压力表进行多路复用，实现了实时多点测量。海啸数值模拟可以准确地掌握海啸的规模和到达时间。如果在本研究成果的基础上实现大范围海底海啸仪的测量网络，就可以准确地发出海啸预警，并有望将损失降到最低。

An optical hydraulic-pressure gauge for an optical ocean bottom tsunami meter was developed using a frequency, shifted feedback laser with a rolled fiber sensor based on optical frequency domain reflectometry. Measuring the optical path length of the fiber, the hydraulic pressure is calculated. The sensor consisted of an 870 m-long bare dispersion-shifted fiber rolled on a hollow cylindrical aluminum bobbin, and its pressure sensitivity was confirmed as -2.34 10^<-11> /Pa. The accuracy of distance measurement was 10^<-9> using the frequency shifted feedback laser oscillating at 1.55 μm. Then the accuracy of pressure measurement using this system was 62 Pa, which corresponds to a depth of 6.2 mm and is sufficient performance for tsunami-measurement applications.Moreover, an origin with a field-spread of a tsunami was estimated using the reverse propagation technique analysis. This draws the wave crest lines to the maximum high-water level point and zero-cross point of the first wave of tsunami about each of two ocean bottom tsunami meters, and estimates the intersection as the origin area. As a result of carrying out a simulation about the tsunami network for the Pacific rim, by adding ocean bottom tsunami meters to the Hawaii Islands circumference realized that an origin area could be estimated with less than 20 % of error.On the coast of our country, human life is taken by tsunami and it is inflicting serious material damage frequently. It is indispensable to damage mitigation by tsunami offering exact information promptly. Real-time multi-point measurement is possible by the multiplexing the laser hydraulic pressure gauge using a frequency-shifted feedback laser. A tsunami numerical simulation can grasp correctly the scale and arrival time of tsunami. If the measurement network by the ocean bottom tsunami meter of a wide area based on this research result is realized, an exact tsunami warning can be issued and it is expected to minimize the damage.