High-precision seawater sound velocity measuring method based on optical frequency comb interference

Abstract

The invention discloses a high-precision seawater sound velocity measuring method based on optical frequency comb interference. The method comprises the following steps: a high-precision seawater sound velocity measuring optical path based on optical frequency comb interference is set up, so that a precise displacement platform continuously moves so as to change the optical distance of an interference optical path and a first reflection optical path; oscilloscope measurement data are collected; moment points t1 and t2 at which the optical distance of the interference optical path are equal tothe optical distance of the measuring optical distance and a reference optical path separately are obtained according to interference fringes at optical frequency combs A and B; the number of continuous light interference fringes between t1 and t2 is calculated, thereby determining the flight distance of sound waves; and the flight time of sound waves is calculated according to a sudden change oflight intensity caused by a pulse acousto-optic effect. The high-precision seawater sound velocity measuring method based on optical frequency comb interference takes the optical frequency comb interference and the pulse acousto-optic effect as fundamental principles to detect a seawater sound velocity profile, and aims at realizing sound velocity measurement with high accuracy and high stability.

Description

technical field [0001] The invention relates to the field of seawater sound velocity measurement, in particular to a high-precision seawater sound velocity measurement method based on optical frequency comb interference. Background technique [0002] The sound velocity measurement in seawater generally includes two types of methods, one is the direct measurement method by measuring the flight time of ultrasonic waves within a fixed distance or measuring the wavelength and frequency of ultrasonic waves; the other is by measuring seawater temperature, salinity, and depth parameters based on Indirect measurement method calculated by empirical formula. Indirect measurement methods are mainly calculated based on existing model formulas, but there are often large errors. In comparison, the direct measurement method involves fewer parameters in principle (only time and distance, or frequency and wavelength), and has higher measurement accuracy. [0003] At present, conventional s...

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Problems solved by technology

However, in the measurement of the time parameter, the transmission and reception of the sound signal of the conventional sound velocity profiler requires a certain time delay due to the piezoelectric effect. Flying back and forth multiple times, that is, use the received reflected echo to trigger the circuit, and then transmit the next pulse, so that the cycle continues, which leads to a cumulative error effect, and the echo interferes with the transmitted signal, so the time cannot be guaranteed high precision of measurement

[0004] In the measurement of the distance parameter, because the ultrasonic probe is embedded in the distance parameter, it is difficult to ensure that the ultrasonic travel distance is strictly consistent with the calibration distance, and it is also difficult to ensure the accuracy of the measurement; there are also sound velocity profilers with calibrated ultrasonic flight distances on the market. However, due to the complex environment in which the instrument is used, it is difficult to ensure the accuracy of the calibration distance

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