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Fiber-Perot water hearing device arbitrarily non-linear sound pressure demodulation method and system

A technology of nonlinear acoustic and demodulation methods, applied in instruments, measuring ultrasonic/sonic/infrasonic waves, measuring devices, etc., can solve the problems of uncertain phase increase or decrease, large calculation error, phase ambiguity, etc., and achieve linearity Good accuracy, simple demodulation system, good repeatability

Active Publication Date: 2021-08-10
CHONGQING UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But this method also has the following disadvantages: 1) Since the linear range is very narrow, the sound pressure demodulated after exceeding the linear range is obviously smaller than the actual sound pressure, resulting in large calculation errors; 2) Since it is a linear demodulation method, There is an upper limit for interference signal output, so there is an upper limit for sound pressure demodulation; 3) There is a phase ambiguity problem, that is, when the phase change caused by sound pressure is near the extreme point, the slight change of the phase of the fiber optic Fabry-Perot hydrophone will be extremely Insensitive, small changes in the phase hardly cause changes in the interference signal, and it is not possible to determine whether the change in the phase is increasing or decreasing
Therefore, limited by these three problems, the optical fiber Fabry-Perot hydrophone is greatly limited when it uses the best linear bias point direct measurement method for sound pressure demodulation

Method used

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  • Fiber-Perot water hearing device arbitrarily non-linear sound pressure demodulation method and system
  • Fiber-Perot water hearing device arbitrarily non-linear sound pressure demodulation method and system
  • Fiber-Perot water hearing device arbitrarily non-linear sound pressure demodulation method and system

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Embodiment 1

[0036] Example 1: Nonlinear Sound Pressure Demodulation System at Any Working Point of Optical Fiber Fabry-Perot Hydrophone

[0037] see figure 1 The structure of the optical fiber Fabry-Perot hydrophone involved in the nonlinear sound pressure demodulation method at any working point of the optical fiber Fabry-Perot hydrophone provided by the present invention includes: input / output single-mode optical fiber 003, reflective optical fiber 001 and quartz capillary 002, The two ends of the quartz capillary are respectively fused with the single-mode optical fiber and the reflective optical fiber, and the air cavity in the quartz tube is used as an interference cavity; an optical fiber Fabry-Perot hydrophone is naturally formed between the two reflective surfaces of the air cavity Fabry-Perot cavity of the device.

[0038] figure 2Shown is a schematic diagram of the system structure of an embodiment of the method for demodulating the nonlinear sound pressure at any working poi...

Embodiment 2

[0039] Embodiment 2: Demodulation method of nonlinear sound pressure at any working point of optical fiber Fabry-Perot hydrophone

[0040] image 3 The flow chart of the demodulation method for this system includes the following steps:

[0041] 1. Obtain the reflection spectrum: the ultrasonic transducer 107 does not output to ensure that the ultrasonic wave does not act on the optical fiber Fabry-Perot hydrophone 106, and the data acquisition card 110 records the output voltage V of the photodetector 109 along with the wavelength of the tunable laser 102 wavelength Discrete point data, i.e. reflectance spectrum, with increasing λ variation, such as Figure 4 shown. Then the ultrasonic transducer 107 outputs the ultrasonic wave to act on the fiber optic Fabry-Perot hydrophone.

[0042] 2. Adjust the working point of the laser and determine the initial phase: 101 pairs of PCs Figure 4 The mid-reflection spectrum is subjected to Fourier transform, the cavity length L of the...

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Abstract

The invention provides a nonlinear sound pressure demodulation method and system at any working point of an optical fiber Fabry-Perot hydrophone, belonging to the technical field of optical fiber sensing. The method comprises the following steps: 1) obtaining the reflection spectrum; 2) adjusting the working point of the laser to determine the initial phase; 3) phase conversion of the reflection spectrum, curve fitting and solving the inverse function; 4) calculating the change amount of the optical phase and determining the cavity 5) demodulate the nonlinear sound pressure according to the coupling model. Compared with the existing linear demodulation method, the method and system provided by the invention can overcome the phase ambiguity problem while ensuring that the sound pressure demodulation range of the optical fiber Fabry-Perot hydrophone has no theoretical upper limit and accurate demodulation.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to the sound pressure demodulation technology of an optical fiber hydrophone. Background technique [0002] High intensity focused ultrasound (HIFU) technology is a non-invasive treatment technology. It focuses low-energy ultrasound outside the body on the target area in the body, and generates transient high temperature in the target area to achieve the purpose of ablation of tissue. As the sound pressure is the core parameter of HIFU, it is extremely important to accurately measure and demodulate the sound pressure. Since the HIFU sound field has obvious characteristics such as small size of the acoustic focal area, high temperature effect, cavitation effect, and mechanical effect, there is no completely ideal method for sound pressure measurement and demodulation so far. The optical fiber Fabry-Perot hydrophone is an ideal sound pressure measurement sen...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01H9/00
CPCG01H9/004
Inventor 王代华王杰
Owner CHONGQING UNIV