【作者】 刘超；

【导师】 薛彬；

【作者基本信息】 天津大学 ， 海洋技术， 2021， 硕士

【摘要】 海水声速是海洋声学探测技术体系中的关键参量,海水声速的测量精度对海底地形测量、水下导航与定位等应用有重要影响。在海水声速的量值传递与溯源体系中,目前仍以纯水温盐压值间接计算声速的方法构建海水声速基准,尚无可复现声速定义的直接法海水声速基准装置,这是海洋计量学科中长期未得到解决的计量基准构建问题。研究基于距离和时间测量的直接法海水声速定义复现性基准装置,既有计量层面的科学意义,也有保证海水声速量传一致的应用价值。本文提出以重复频率锁定的飞秒激光作为海水声速基准构建手段,研究声速定义中距离和时间直接向频率基准溯源的原理和方法。首先,研究了飞秒激光的声光效应,分析介绍了水中声波与飞秒激光的相互作用机理,研究结果表明声波的相位调制了飞秒激光的相位,进而影响了飞秒激光的脉冲间距;其次,研究了水中声波的飞行距离和飞行时间调制到飞秒激光重频的激光干涉方法,以及相应的激光干涉解调方法,主要采用多构型的迈克尔逊干涉技术进行声波信息的调制和解调,实验结果表明这是一种有效的实现声波信息与激光参量转接的技术手段;最后,根据以上思路,搭建实验装置进行海水声速测量的性能验证,结果表明,在不同的海水盐度、温度条件下,与商用声速仪相比,本装置的实验室海水声速测量最大误差优于0.016 m/s。在完成以上研究内容基础上,对所搭建的装置进行不确定度分析,测量声速合成不确定度为0.023 m/s。结果表明本文提出的方案有比较好的定义复现性,可为基于飞秒激光的海水声速基准装置研制储备一定的前期基础。更多还原

【Abstract】 The seawater sound velocity is a key parameter in the marine acoustic detection technology system.The accuracy of seawater sound velocity measurement has an important effect on applications such as seabed topography measurement,underwater navigation and positioning.At present,in the transfer and trace of the value of quantity system of the seawater sound velocity,the indirect calculation method of sound velocity based on the water temperature,salt,and pressure,is still used to construct the seawater sound velocity standard.There is no direct seawater sound velocity standard device that can reproduce the definition.It is a long-term unresolved measurement standard construction problem in marine metrology.The research of the direct method based on distance and time measurement of seawater sound velocity definition repeatability standard device,has not only the scientific significance of measurement level,but also the application value of guaranteeing the consistency of the value of quantity of seawater sound velocity.In this paper,a femtosecond laser with repetitive frequency lock is proposed as a standard for the construction of seawater sound velocity.It is used to study the principle and method that the distance and time are traced directly to the frequency standard in the sound velocity definition.Firstly,I studied the acousto-optic effect of the femtosecond laser,and discussed the interaction mechanism between the sound wave and femtosecond laser underwater.The experimental results show that the phase of the sound wave modulates the phase of the femtosecond laser,which in turn affects the pulse interval of the femtosecond laser.Secondly,I studied the laser interferometry method of modulating the flight distance and flight time of the sound wave underwater to the femtosecond laser repetition frequency,and the corresponding laser interferometry demodulation method.I mainly use multi-configuration Michelson interference technology to modulate and demodulate sound wave information.The experimental results show that it is an effective technical means to realize the conversion of sound information and laser parameters.Finally,based on the above ideas,I built an experimental device to verify the performance of seawater sound velocity measurement.The results show that the maximum error of the sound velocity measurement in the laboratory is better than 0.016 m/s compared with the sound velocity sensor,under different conditions of seawater salinity and temperature.Based on completing the above research content,I have carried out an uncertainty analysis of the experimental device,and the combined uncertainty is 0.023 m/s.The results show that the proposed scheme has good definition reproducibility.And it can be used as a preliminary basis for the development of the seawater sound velocity standard device based on the femtosecond laser.更多还原