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CN-117250172-B - Salinity sensing device for deep sea measurement field

CN117250172BCN 117250172 BCN117250172 BCN 117250172BCN-117250172-B

Abstract

The invention belongs to the technical field of sensing, and relates to a salinity sensing device for a deep sea measuring field, which comprises a main structure of a laser, an attenuator, an optical beam splitter, a gas absorption tank, an FP etalon, a detector, a circulator, a sensing probe, an analog-to-digital conversion module, an industrial personal computer and a control module, wherein the electric communication and coordination of all the components form an integrated structure, a current control module provided with a labview program in the industrial personal computer enables the laser to continuously and repeatedly output regular optical signals to realize sweep frequency, the optical signals are decomposed into three paths of light beams by the optical beam splitter after passing through the attenuator, sinusoidal signals are obtained at two ports through a salinity MZ detection path of the salinity sensing probe, the three paths of signals received by the detector are converted by the analog-to-digital conversion module and then returned to the industrial personal computer for demodulation, and then the laser is controlled by a voltage output, current control and temperature control module for realizing salinity measurement.

Inventors

  • WU QI
  • JI LANTING
  • YANG SHUQING

Assignees

  • 德州尧鼎光电科技有限公司

Dates

Publication Date
20260512
Application Date
20230207

Claims (5)

  1. 1. A salinity sensing device for deep sea measurement occasions is characterized by comprising a laser, an attenuator, an optical beam splitter, a first attenuator, a second attenuator, a gas absorption tank, an FP etalon, a detector, a circulator, a salinity sensing probe, an analog-to-digital conversion module, an industrial personal computer, a voltage output module, a current control module and a temperature control module, wherein the information of all the components is communicated and is optically matched to form an integrated structure, the industrial personal computer with the information processing and regulating functions is internally provided with a current control module of a labview program, the current control module enables the laser to continuously and repeatedly output optical signals with rules to realize sweep frequency, the optical signals are decomposed into three paths of light beams by the optical beam splitter after passing through the attenuator, the first path of light beams pass through the gas absorption tank and then pass through the detector, and finally pass through the peak of the sweep frequency processing and the gas absorption tank to realize calibration of system errors, the second path of light beams pass through the second attenuator and then pass through the detector and finally pass through the frequency sweep frequency conversion module to realize uniform peak demodulation, the third path of light beams is calibrated, the loop detector passes through the temperature control module and the Mach-Zehnder interferometer to obtain signals with the sine wave length, the sine wave length is obtained by the output of the laser after passing through the temperature control module after passing through the fiber-Mach-Zehnder interferometer and the fiber optics, the main structure of the salinity sensing probe comprises an optical fiber collimator, a beam splitting prism, a first reflecting mirror, a first optical path difference compensation window, a second reflecting mirror, a first detection solution and a second detection solution, all the components are matched according to the optical and mechanical structure principles to construct an integrated salinity sensing probe structure for measuring the deep sea environment, and the salinity sensing probe structure is connected into a salinity measuring device system through a circulator to realize salinity detection and treatment under the marine environment condition.
  2. 2. The salinity sensing device for deep sea measurement according to claim 1, wherein the laser, the attenuator, the industrial personal computer, the analog-to-digital conversion module, the detector and the laser controller are functionally distinguished to form a demodulation system, the fiber collimator, the beam splitting prism, the anti-reflection film-plated arm length control window structure, the reflector and the adjusting frame are cooperatively formed into a salinity sensing detection system, the fiber collimator can keep the optical path in a collimation state when the fiber inputs space light and realize the retraction of the reflection optical path, interference is realized in the fiber, the beam splitting prism divides the collimated light into two beams according to a ratio of 1:1 and respectively enters into seawater with different lengths to form two optical paths, the arm length control window structure of the anti-reflection film can ensure that the light transmission efficiency reaches more than 97% and control the length of the two optical signals to the water area detection, the reflector and the adjusting frame are adjusting structures for realizing the refraction and measurement of the optical path return fiber collimator, the opening detection optical path with two different lengths of the Mach-Zehnder interference structure can realize the refraction and measurement of the salinity interference structure, and the Mach-Zehnder interference structure can realize the return light interference structure with different lengths through the two Mach-Zehnder interference structures The optical path difference of the optical fiber is interfered to obtain the related information of the refractive index; the laser is a single-frequency mode-hop-free laser; the attenuator controls the input of light intensity, the industrial personal computer provides a platform for labview programs, and the analog-digital conversion module realizes the acquisition and recording of signals; the demodulation system realizes the measurement of the refractive index and the salinity by carrying out peak searching demodulation on the sine signal of the Mach-Zehnder interference structure, and the device is suitable for measuring the salinity and the refractive index of deep ocean.
  3. 3. The salinity sensor for deep sea measurement according to claim 2, wherein the related arm length control window structure with anti-reflection coating can keep light, the optical path difference of two paths of space light is composed of three parts of air length difference, window length difference and product of detection length difference and respective refractive index of two paths, the air length of the optical paths can be the same, the window lengths are consistent, the optical path difference compensation is realized through structural distribution, the optical path difference of the Mach-Zehnder interference structure is generated from the detection parts with different lengths 。
  4. 4. The salinity sensor for deep sea measurement according to claim 1, wherein the interference result of the Mach-Zehnder interference structure only carries the optical path difference generated by the passage of the liquid in the detection water area, and the two detection paths are in open circulation structure, so that the liquid to be detected passing through the two light paths has the same optical characteristics, and the formula is Obtaining the result that the interference result of the Mach-Zehnder interference structure is The determined condition carries refractive index information, and the sensing of the refractive index and the salinity is realized through later demodulation.
  5. 5. The salinity sensing device for deep sea measurement according to claim 2, wherein the demodulation system further comprises a gas absorption cell, an FP etalon and a LABVIEW demodulation program, wherein the demodulation system scans the wavelength of the single frequency laser, sweeps the absorption peak of the gas absorption cell and the resonance peak of the FP etalon, determines the wavelength of the laser and corrects parameters of the system, demodulates the refractive index of the mach-zehnder interference structure by using LABVIEW peak search algorithm for the demodulation of the recovered signal, and calculates the salinity.

Description

Salinity sensing device for deep sea measurement field Technical Field The invention belongs to the technical field of ocean optical sensing, and relates to a salinity sensing device for a deep sea measurement occasion, which adopts a sensing structure with MZ of different arm lengths, and (3) returning the light to the detector by using the reflector to collect the optical interference signal, and demodulating and calculating the signal to obtain the salinity. Background At present, the salinity sensing technology used in the ocean field is mainly mastered by a few developers with stronger professional technology, calibration of the product needs to be carried out in the original factory, and the problems of data loss and possible deviation of calibration are accompanied, so that domestic detection of the salinity of the seawater has higher requirements. The research on the salinity sensor in China mostly adopts a conductivity method for sensing, the electrical method only can test free ions in the seawater, and has more defects, in recent years, the method for testing the salinity based on the conductivity method has no obvious development, and the sensing method based on the electricity encounters a bottleneck. For the characteristics of high precision, high resolution and the like of the optical sensor, the method hopefully breaks the current electrical sensing precision. The salinity sensing based on optics not only can be suitable for researching the salinity environment change of the ocean, but also can be widely applied to various economic benefit places such as ocean pastures. The patent with the Chinese patent application number 202210762148.3 discloses a Fabry-Perot resonant cavity type salinity sensor, the main structure of which comprises a laser or a laser for short with the wavelength of 633mn, a beam collimator, an electronic controller, an FP cavity, a photoelectric detector, a focusing lens and a control panel; the output end of the laser is correspondingly connected with a beam collimator, the output end of the beam collimator is correspondingly connected with a focusing lens and is in light conduction connection with an FP cavity through the focusing lens, the FP cavity is connected with a photoelectric detector, the photoelectric detector is in electric information connection with the laser through an electronic controller with a control panel to form a salinity sensor with a photoelectric integrated structure, the salinity sensor is used for measuring salinity of liquid in the FP cavity, the electronic controller is an automatic photoelectric information control component with the control panel, the main structure of the electronic controller is formed by connecting a control chip, a low-pass filter, a local oscillator and a multiplier, the conversion detection and control of light and electric signals can be realized, the control process of the electronic sensor can realize operation through the control panel, the electronic controller is used for controlling the output of the laser and the received signals to be processed, the focusing lens is focused on the photoelectric detector through laser projected by the FP cavity, the light collimator is collimated into a collimated light beam by the laser, the liquid in the FP cavity, the change of refractive index or salinity can cause the resonance frequency to change, thus the feedback voltage is also changed, the FP signal is sent out through the laser collimator to the laser cavity, the laser signal is then sent to the laser cavity through the optical fiber, the laser signal is reflected by the optical fiber, the laser signal is then sent to the optical fiber through the optical fiber, the laser cavity, the laser signal is then the laser cavity is irradiated, the laser cavity is separated, the laser cavity is then the laser signal is irradiated, the error signal is calculated by a control chip of a PID structure after passing through a low-pass filter to obtain a control signal, the control signal is fed back to the laser, the laser frequency is controlled to change along with the change of the refractive index or the salinity of liquid in the FP cavity, the function of a salinity sensor is realized, and the sensor is difficult to meet the use of a large-depth ocean environment. The main structure of the FP cavity comprises a cavity mirror and a cavity, wherein the right end part of the FP cavity with a cylindrical hollow structure is fixedly connected with the cavity with a cylindrical structure in a butt joint way, the cavity mirror is coated with a reflection medium, liquid for measurement is filled in the cavity of the FP cavity, the reflectivity of the cavity mirror of the FP cavity is 90-97%, the material of the cavity of the FP cavity is microcrystalline glass or a material which is not easily affected by temperature and stretches, and the relation between the refractive index of the FP cavity and the frequency of a laser is as f