CN214372544U - High-sensitivity seawater salt temperature double-parameter sensor based on interference vernier effect - Google Patents
High-sensitivity seawater salt temperature double-parameter sensor based on interference vernier effect Download PDFInfo
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Abstract
The utility model relates to a high-sensitivity seawater salt temperature double-parameter sensor based on interference vernier effect, which is characterized by comprising a broadband light source, a 2 x 2 optical fiber coupler, two double FP-cavity Fabry-Perot interferometers arranged in parallel and a spectrometer; the double FP cavity Fabry-Perot interferometer comprises a single-mode optical fiber, an optical fiber micro-bulb structure with a micro-flow channel and a large mode field optical fiber which are sequentially arranged. The free spectral range of the air cavity and the quartz cavity of the interferometer is close by setting the optical fiber micro-bulb structure with different parameters and the large-mode-field optical fiber cavity length, so that the vernier effect is realized. The cavity lengths of the two double FP cavity Fabry-Perot interferometers are set, so that the frequencies corresponding to the output spectrums of the two Fabry-Perot interferometers keep interval. When the salinity and the temperature of the seawater change, the cavity length of the interferometer changes, Fourier transform and filtering are carried out on the output spectrum, and the output spectrum and the envelope of each interferometer are obtained. By enveloping the signal drift amount and combining the salinity temperature sensitivity matrix, the simultaneous measurement of double parameters can be realized. The utility model has the advantages of the practicality is strong, compact structure, simple manufacture, sensitivity are high, stability is strong, can simultaneous measurement multi-parameter.
Description
Technical Field
The utility model belongs to the optical fiber sensing field, concretely relates to high sensitive sea water salt temperature two parameter sensor based on interfere vernier effect. The sensor has the advantages of simple structure, high sensitivity, good repeatability and real-time on-site accurate detection.
Background
The vernier effect utilizes the principle that the alignment graduation of the main scale and the vernier scale can be changed in a large range under the condition that a tiny measurement value is changed, so that the tiny quantity can be amplified and read, and the measurement precision is improved. The vernier effect is widely applied in the field of measurement. The vernier effect is combined with the optical fiber Fabry-Perot interferometer, two FP interference cavities are cascaded, output spectrum signals are superposed to form a new fringe envelope signal, and the fringe envelope is demodulated, so that the high-precision measurement of the parameter to be measured can be realized.
The salinity and the temperature of the seawater are closely related to the marine environment and the climate change, and the acquisition of high-precision seawater salt temperature parameters has important research significance. The current common seawater salinity measuring methods comprise a conductivity method, a microwave remote sensing detection technology, a refractive index measuring method and the like; the common seawater temperature measuring method mostly adopts electronic sensors such as platinum resistors, thermistors and the like to measure the temperature. The optical fiber has the advantages of small volume, strong anti-interference capability and the like, and is widely applied to the field of ocean sensing at present, such as a common optical fiber salinity sensor based on the surface plasma resonance effect; fiber grating based ocean temperature sensors, and the like. The sensor based on the photorefractive method has high sensitivity when measuring salinity parameters, but needs other sensors when measuring temperature parameters, so that the sensitivity is low, the high-sensitivity measurement on the seawater salt temperature double parameters cannot be simultaneously carried out, the structure is complex, and the stability is poor; the sensor based on the surface plasma resonance effect has the advantages of fast response and high sensitivity, can realize seawater salinity and temperature double-parameter measurement by coating a temperature-sensitive material, but is easy to be eroded by seawater, and has the problems of salinity and temperature cross talk and the like; the sensor based on the fiber bragg grating can realize the simultaneous measurement of the salinity and the temperature of the seawater, the reusability is good, the demodulation method is mature, but the response is slow, and the sensitivity is low; the interference type sensor has the advantages of simple structure, good stability, high sensitivity and the like, but is mostly suitable for single-parameter measurement; these disadvantages have seriously hindered the development and application of the seawater salt temperature dual-parameter sensor.
To above-mentioned sensor sensitivity low, unable simultaneous measurement sea water salinity temperature biparameter, salinity temperature cross sensitive scheduling problem, the utility model provides a high sensitive sea water salt temperature biparameter sensor based on interfere vernier effect. The sensor has the advantages of simple structure, low manufacturing cost, good stability, high response speed, high sensitivity and the like, solves the problems that the traditional cascade interference structure is mostly suitable for single-parameter measurement, cross sensitivity of salinity and temperature and the like, and can realize high-sensitivity measurement of salinity and temperature double parameters of seawater.
SUMMERY OF THE UTILITY MODEL
Sensitivity to optic fibre salinity and temperature sensor ubiquitous is lower, and the salinity temperature is alternately sensitive, poor stability scheduling problem, the utility model provides a simple structure, with low costs, the practicality is strong one kind based on interfere vernier effect's high sensitive sea water salt temperature two parameter sensor.
The utility model discloses a solve the device that technical problem took:
a high-sensitivity seawater salt temperature double-parameter sensor based on an interference vernier effect comprises a broadband light source, a 2 x 2 optical fiber coupler, two single-mode transmission optical fibers, two double-FP cavity Fabry-Perot interferometers and a spectrometer; the broadband light source is connected with a double FP cavity Fabry-Perot interferometer through a 2 x 2 optical fiber coupler; the spectrometer is connected with another double FP cavity Fabry-Perot interferometer through a 2 x 2 optical fiber coupler; the double-FP cavity Fabry-Perot interferometer comprises a single-mode transmission optical fiber, an optical fiber micro-bulb structure with a micro-flow channel, namely an air cavity, and a large-mode-field optical fiber, namely a quartz cavity, which are sequentially arranged from the optical fiber transmission direction; the two double FP cavity Fabry-Perot interferometers are arranged in parallel at the same side of the 2 multiplied by 2 optical fiber coupler; the difference range of the free spectral ranges of the air cavity and the quartz cavity in the double FP cavity Fabry-Perot interferometer is between 0nm and 2.0 nm; the minimum frequency difference of the output spectra of the two Fabry-Perot interferometers with double FP cavities is more than 0.05; the microfluidic channel of the optical fiber micro-bulb structure is vertical to the direction of the fiber core, the top of the optical fiber micro-bulb structure is provided with a water filling port, and the bottom of the optical fiber micro-bulb structure is provided with a water outlet.
The utility model has the advantages that:
the utility model discloses utilize hydrofluoric acid solution sculpture and heat sealing machine to discharge the preparation that realizes optic fibre microballon bubble structure, utilize femto second laser at optic fibre microballon bubble structural sculpture miniflow passageway. The manufacturing process is simple and the cost is low. The manufactured sensing structure has good stability and higher mechanical strength.
The utility model discloses utilize vernier effect, greatly improved sensing structure's sensitivity. The vernier effect is realized through the double-FP cavity Fabry-Perot interferometer, the change speed of an envelope signal of an output spectrum formed after the spectrums are overlapped is far higher than the change speed of a spectrum peak value, and the envelope signal is detected to realize the amplification of sensitivity.
The utility model discloses utilize the cascaded two FP chamber fabry-perot interferometers in air chamber and quartz chamber to realize the biparametric measurement of salinity and temperature. The method comprises the steps of acquiring output spectra containing salinity change and temperature change information by utilizing the characteristics that an optical fiber micro-bulb structure and a quartz cavity are sensitive to refractive index and temperature respectively, acquiring the output spectra and spectral envelopes of two interferometers in a filtering mode, and constructing a sensitivity matrix for measuring temperature and salinity simultaneously, thereby realizing double-parameter measurement. The sensor has simple and compact structure, high sensitivity and good stability, and can be used for simultaneously measuring salinity and temperature.
Drawings
FIG. 1 is a schematic diagram of a high-sensitivity seawater salt temperature dual-parameter sensor based on an interference vernier effect.
FIG. 2 is a graph of the output spectrum of a high-sensitivity seawater salt temperature two-parameter sensor based on the interference vernier effect.
Fig. 3 is a spectral diagram of the output spectrogram after fourier transform.
FIG. 4 is a graph of the output spectra of two interferometers filtered from the spectrogram and a lower envelope fit.
FIG. 5 is a spectrum envelope diagram obtained after fitting of the output spectra of the two interferometers when the salt temperature of seawater changes.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, a high-sensitivity seawater salt temperature double-parameter sensor based on an interference vernier effect includes a broadband light source 1, a 2 × 2 optical fiber coupler 2, a single-mode optical fiber 3, an optical fiber micro-bubble structure 4, a water filling port 5, a water outlet 6, a large-mode optical fiber 7, a single-mode optical fiber 8, an optical fiber micro-bubble structure 9, a water filling port 10, a water outlet 11, a large-mode optical fiber 12, and a spectrometer 13. The broadband light source 1 and the spectrometer 13 are respectively connected with two ends of the left side of the 2 x 2 optical fiber coupler 2, one end of the right side of the 2 x 2 optical fiber coupler 2 is connected with the single-mode optical fiber 3, one end of the optical fiber microsphere bubble structure 4 is connected with the single-mode optical fiber 3, and the other end of the optical fiber microsphere bubble structure is connected with the large-mode-field optical fiber 7; the other end on the right side of the 2 x 2 optical fiber coupler 2 is connected with a single mode fiber 8, one end of the optical fiber microsphere bubble structure 9 is connected with the single mode fiber 8, and the other end is connected with a large mode field fiber 12. The single-mode optical fiber 3, the optical fiber micro-bubble structure 4 and the large-mode-field optical fiber 7 form a double-FP cavity Fabry-Perot interferometer I, and the single-mode optical fiber 8, the optical fiber micro-bubble structure 9 and the large-mode-field optical fiber 12 form a double-FP cavity Fabry-Perot interferometer II.
As shown in fig. 2, the output spectrum of a high-sensitivity seawater salt-temperature two-parameter sensor based on the interference vernier effect is the superposition of the output spectra of two interferometers. When the refractive index of the seawater to be detected changes, the output spectrum changes irregularly. And Fourier transform is carried out on the output spectrum to obtain a corresponding spectrogram.
As shown in fig. 3, the peaks in the spectrogram corresponding to the output spectrogram are far apart, peak 1 is the spectrum corresponding to the output spectrum of the dual FP cavity fabry-perot interferometer i, and peak 2 is the spectrum corresponding to the output spectrum of the dual FP cavity fabry-perot interferometer ii, and the output spectrogram of the single interferometer can be obtained by filtering.
As shown in fig. 4-1, the output spectrogram is fourier transformed and filtered to obtain an output spectrogram of a dual FP cavity fabry-perot interferometer i. As shown in fig. 4-2, the output spectrogram is fourier transformed and filtered to obtain the output spectrogram of the dual FP cavity fabry-perot interferometer ii. The dotted line in the figure is the envelope fit under the output spectrum.
As shown in fig. 5-1, when the salt temperature of seawater changes, the spectrum envelope obtained after the spectrum fitting is output by the double FP cavity fabry-perot interferometer i drifts. And 5-2 shows the spectral envelope change obtained by the spectral fitting of the output spectrum of the Fabry-Perot interferometer II with double FP cavities when the salt temperature of the seawater changes. Immersing the sensor into seawater with the same temperature and different salinity, and measuring the salinity sensitivity; and (4) immersing the sample in deionized water with different temperatures to measure temperature sensitivity, and constructing a sensitivity matrix of temperature and salinity. When the salinity and the temperature of the seawater to be measured change, the output spectra of the two interferometers drift. And (3) immersing the sensing structure into seawater to be measured, demodulating the output spectrum to obtain the spectrum envelope drift amount of the two interferometers, and substituting the spectrum envelope drift amount into the sensitivity matrix to realize simultaneous measurement of double parameters.
The utility model discloses a working method does: the signal light emitted by the broadband light source 1 is divided into two beams by the 2 x 2 optical fiber coupler 2, when one beam of light is transmitted to the optical fiber micro-bulb structure 4 along the fiber core of the single-mode optical fiber 3, due to the fact that the refractive indexes of air and quartz are different, one part of light is subjected to Fresnel reflection on the contact surface of the air and the quartz, and the other part of light is transmitted to the large-mode-field optical fiber 7 through the contact surface. Light reflected from the large mode field fiber 7 meets the two beams reflected from the fiber microsphere bubble structure 4 at the single mode fiber 3 to create interference. The other light output by the 2 x 2 optical fiber coupler 2 is transmitted to the optical fiber micro-sphere bubble structure 9 along the fiber core of the single-mode optical fiber 8, then a part of light is subjected to Fresnel reflection at the contact surface of air and quartz, and the other part of light is transmitted to the large-mode-field optical fiber 12 through the contact surface. Light reflected from the large mode field fiber 12 meets the two beams reflected from the fiber microsphere bubble structure 7 at the single mode fiber 6 to create interference. The superimposed spectrum formed after the reflected light is transmitted to the spectrometer 13 is taken as an output spectrum. Seawater to be measured is respectively injected into the optical fiber micro-bulb structure 4 and the optical fiber micro-bulb structure 9 from the water injection port 5 and the water injection port 10 and flows out from the water outlet 6 and the water outlet 11. When the temperature of seawater changes, the cavity length of a quartz cavity in the double FP cavity Fabry-Perot interferometer changes due to the length of a thermo-optic effect, so that the drift of an output spectrum envelope signal is caused; when the salinity of seawater changes, the length of the air cavity of the Fabry-Perot interferometer with the double FP cavities is unchanged, but the optical path changes due to the change of the refractive index of a medium in the cavity, so that the spectral envelope drift is caused. Immersing a double FP cavity Fabry-Perot interferometer in seawater with the same temperature and different salinity, and measuring the corresponding salinity sensitivity coefficient; and immersing the double FP cavity Fabry-Perot interferometer in deionized water with different temperatures, measuring corresponding temperature sensitivity coefficients, and constructing a sensitivity matrix of temperature and salinity. The utility model discloses the output spectrum that finally obtains comprises the different interference fringe of a series of intensity, carries out Fourier transform to sensing structure output spectrum and can obtain the spectrogram that corresponds. The minimum frequency difference of the output spectra of the two Fabry-Perot interferometers with the double FP cavities is larger than 0.05, the respective output spectra of the two interferometers can be obtained in a filtering mode, and the spectrum envelopes are obtained by performing sine fitting on the output spectra of the interferometers. And comparing the spectrum envelopes obtained by demodulating the output spectrum of the sensing structure in the seawater to be measured and the deionized water with the known temperature to obtain the envelope drift amount, and substituting the envelope drift amount into the sensitivity matrix to realize the high-sensitivity measurement of the double parameters of the seawater salinity and the temperature.
The device can realize that the key technology of a high-sensitivity sea water salt temperature double-parameter sensor based on interference vernier effect has:
the structural parameters of the FP interference cavity are controlled to ensure that the free spectral ranges of the air cavity and the quartz cavity in the double FP cavity Fabry-Perot interferometer are different and have small difference, and the difference range is between 0nm and 2.0nm so as to realize the vernier effect and generate an envelope signal. The period of the envelope signal is smaller than the wavelength range of the light source and the spectrometer, so that the change of the envelope signal can be observed conveniently.
And controlling the structural parameters of the FP interference cavity to ensure that the free spectral ranges of the two cavities of the double FP cavity Fabry-Perot interferometer I and the free spectral ranges of the two cavities of the double FP cavity Fabry-Perot interferometer II have larger difference, the corresponding output spectrum has longer distance between peaks in a frequency domain, and the minimum frequency difference is larger than 0.05 so as to realize the filtering function.
The manufacturing of the optical fiber micro-bulb is realized by controlling the etching time and setting appropriate welding parameters, and the high-sensitivity optical fiber sensor which is strong in stability and can be repeatedly used for a long time is realized.
And respectively measuring the sensitivity of salinity and temperature of each interferometer through the output spectrogram of the sensor, and constructing a sensitivity matrix related to the salinity and the temperature of the seawater.
Fourier transform and filtering are carried out on the output spectrum of the sensing structure, and the output spectra of the two interferometers are demodulated. And obtaining an envelope curve of the output spectrum of the interferometer by a sine fitting method, and substituting the spectrum envelope drift amounts of the two interferometers into a sensitivity matrix to realize the simultaneous measurement of the salt temperature of the seawater.
In one embodiment of the present invention, the broadband light source HL-2000 has an output wavelength of 360-2000 nm; the single-mode fiber is SMF-28e +, the large-mode-field fiber is LMA-GDF-10/125-M, the diameters of the optical fiber micro-bulb structure 4 and the optical fiber micro-bulb structure 9 are 65.330 mu M and 68.052 mu M respectively, and the lengths of the large-mode-field fiber 7 and the large-mode-field fiber 12 are 163.848 mu M and 150.194 mu M respectively; the effective reflectivities of three reflecting surfaces of the double FP cavity are respectively 0.03, 0.03 and 0.04, the spectrometer AQ6370 and the working wavelength is 350-2400 nm; measuring the refractive index of the sample as n1＝1.333，n21.340; corresponding to salinity0 per mill and 40 per mill, and the temperature of the sample measured is T1＝20℃，T2At 30 ℃. Experimental results show that the refractive index sensitivity of the high-sensitivity seawater salt temperature double-parameter sensor based on the interference vernier effect can reach 12821nm/RIU, the corresponding salinity sensitivity can reach 0.0039 per thousand, and the temperature sensitivity is 172 pm/DEG C.
The above description and the drawings are only examples of the present invention and do not limit the present invention. The structure, the working principle and the manufacturing method of the utility model are shown in the embodiment, without departing from the principle of the utility model, a plurality of variations and improvements can be made, and the variations and the improvements fall into the protection scope of the utility model.
Claims (1)
1. The utility model provides a high sensitive sea water salt temperature double parameter sensor based on interference vernier effect which characterized in that: the system comprises a broadband light source, a 2 x 2 optical fiber coupler, two single-mode transmission optical fibers, two double FP cavity Fabry-Perot interferometers and a spectrometer; the broadband light source is connected with a double FP cavity Fabry-Perot interferometer through a 2 x 2 optical fiber coupler; the spectrometer is connected with another double FP cavity Fabry-Perot interferometer through a 2 x 2 optical fiber coupler; the double-FP cavity Fabry-Perot interferometer comprises a single-mode transmission optical fiber, an optical fiber micro-bulb structure with a micro-flow channel, namely an air cavity, and a large-mode-field optical fiber, namely a quartz cavity, which are sequentially arranged from the optical fiber transmission direction; the two double FP cavity Fabry-Perot interferometers are arranged in parallel at the same side of the 2 multiplied by 2 optical fiber coupler; the difference range of the free spectral ranges of the air cavity and the quartz cavity in the double FP cavity Fabry-Perot interferometer is between 0nm and 2.0 nm; the minimum frequency difference of the output spectra of the two Fabry-Perot interferometers with double FP cavities is more than 0.05; the microfluidic channel of the optical fiber micro-bulb structure is vertical to the direction of the fiber core, the top of the optical fiber micro-bulb structure is provided with a water filling port, and the bottom of the optical fiber micro-bulb structure is provided with a water outlet.
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| CN115753682A (en) * | 2022-11-07 | 2023-03-07 | 山东大学 | Seawater salinity measuring device and method with temperature self-decoupling function |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115753682A (en) * | 2022-11-07 | 2023-03-07 | 山东大学 | Seawater salinity measuring device and method with temperature self-decoupling function |
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