A high-precision underwater sound velocity measurement method based on femtosecond laser frequency comb

Abstract

The invention discloses a high-precision underwater sound velocity measurement method based on a femtosecond laser frequency comb. By building a double Michelson interferometer and connecting the femtosecond laser to a rubidium clock, the repetition frequency and offset frequency of the optical frequency comb are directly locked On the rubidium clock, the frequency of the optical frequency comb has the same accuracy as that of the rubidium clock; the ultrasonic transducer is connected to the signal source and driven by a power amplifier; the flight distance of the sound pulse is measured by the displacement stage scanning method, using femtosecond The short pulse of the laser frequency comb measures the flight time of the sound pulse by interferometry, and finally realizes the high-precision measurement of the speed of sound underwater. The present invention utilizes the advantage of femtosecond laser, collects the information of the sound pulse with the optical comb, avoids the error factor caused by the piezoelectric effect, and reduces the error of the acoustic profiler directly measuring the underwater sound velocity. In the present invention, the flight distance and the flight time are measured at the same time, so that the obtained results are in a very high order of magnitude, and the accuracy of the sound velocity measurement is greatly improved.

Description

technical field [0001] The invention belongs to the field of underwater sound velocity measurement, in particular to a high-precision underwater sound velocity measurement method based on a femtosecond laser frequency comb. Background technique [0002] Seawater sound velocity measurement is of great significance to ocean detection, positioning and tracking. At present, the main technology for seawater sound velocity measurement is sonar. Sonar uses underwater sound waves to detect underwater targets, and is widely used in important marine engineering applications such as torpedo guidance, ship navigation, hydrographic survey, and submarine imaging. The earliest record of hydroacoustic sounding is from 1490, and the earliest measurement is from 1827. Since then, after long-term development, the seawater sound velocity measurement technology has become increasingly mature, making great contributions to the field of marine science and technology. [0003] The main measureme...

AI Technical Summary

Problems solved by technology

Commonly used methods such as the phase comparison method, by comparing the phase change of the received wave relative to the transmitted wave, have a high accuracy rate, but are limited to many sound waves that are not sine waves

However, in the direct measurement method based on piezoelectric transducers widely used at present, the actual sounding starting point and the sound wave receiving end point are vague, and the traceability is poor.

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