渐变型声纤波导的理论研究

Theoritical Studies of Graded-velocity Fiber Acoustic waveguide

声纤传感技术是继光纤传感技术之后又一新的传感领域,目前尚属探索阶段。作为声纤传感技术的基础,本文对渐变型声纤波导模式理论进行了研究。首先以几何声学的方法简单描述了声速渐变型声纤波导的声传播图像;然后在声波波动方程的基础上,采用WKBJ 近似法分析了波导中导模的传播和截止特性。作者认为,渐变型声纤不仅是声纤传感器优先选择,还将是低损耗、长距离传输声纤的发展方向之一。

The fiber acoustic sensing technique which only at early stageat present,will become a new kind of sensing technique,following the devel-oping of fiber optic sensors,As a basis of fiber acoustic sensing technique.the theories for guide acoustic mode in a graded-velocity profile fiber acousticwaveguide are investigated in this paper.At first,acoustic propagation char-acteristics is described breifly by geometrical acoustics,and then,on the ba-sis of the wave equation and boundary conditions,the guide mode and cut-off conditions are analized by WKBJ approximation.We think that the graded-velocity profile fiber acoustic waveguide is mo-re suitable for sensing applications than step velocity profile fiber acousticwaveguide,in addition,is also more favorable for transmitting sound energyat a long distances.