基于双片锯齿电极的宽带声光偏转器

传统具有单片换能器结构的声光偏转器存在布拉格带宽与衍射效率的权衡关系。为了增加布拉格带宽而又不降低衍射效率,提出一种基于双片锯齿电极的换能器结构的声光偏转器。首先采用双片换能器结构实现超声跟踪,使超声波方向能随频率改变,提高布拉格带宽。在此基础上应用锯齿形电极增大超声波的发散程度,进一步提高布拉格带宽。仿真结果表明,电极的锯齿边缘使声波波动性增大,即增大了超声波的发散程度。实验结果表明,在相同实验条件下,具有双片锯齿电极换能器结构的声光偏转器的3 dB带宽比单片矩形电极换能器结构的声光偏转器高62.5%。

Temperature-insensitive fiber Bragg grating strain sensor

A fiber Bragg grating strain sensor,whose reflection bandwidth is insensitive to temperature,is presented.The cross-sec-tional area is designed to change linearly.Under axial stress,there is a linear relationship between stress and average strain.Experimental results show that when temperature increases,reflection center wavelength shifts to longer wavelength,and there is a good linear relationship between center wavelength and temperature.When stress increases,reflection center wavelength shifts to longer wavelength,and reflection bandwidth increases.There are good linear relationships between reflection center wavelength and stress as well as reflection bandwidth and stress.

Simultaneous sensing of displacement and temperature with a single FBG

A novel fiber Bragg grating(FBG) sensor with simultaneous sensing of displacement and temperature is presented.The FBG is affixed on the cantilever inclinedly.The midpoint of FBG exactly coincides with the zero strain layer of a rectangular beam.The vertical displacement can be measured by the broadened bandwidth of FBG as the bandwidth is insensitive to temperature,while the temperature can be measured by the center wavelength shift as the wavelength shift is insensitive to vertical displacement.With 0.1 nm spectral resolution of the analyzer,sensitivities of bandwidth-displacement and center wavelength-temperature are 0.48 nm/mm and 0.05 nm/℃,resolutions are 0.2 mm and 2.0 ℃,and sensing ranges of displacement and temperature are up to 8.5 mm and 45℃ respectively.Experimental results match theoretical analyses very well.