CN116839640A - Three-core optical fiber parallel type interference sensor based on double-core optical fiber interference demodulation - Google Patents
Three-core optical fiber parallel type interference sensor based on double-core optical fiber interference demodulation Download PDFInfo
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- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35325—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using interferometer with two arms in reflection, e.g. Mickelson interferometer
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
- G01D5/35377—Means for amplifying or modifying the measured quantity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
- G01D5/3538—Optical fibre sensor using a particular arrangement of the optical fibre itself using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like
Abstract
The invention provides a three-core optical fiber parallel type interference sensor based on double-core optical fiber interference demodulation. The device consists of a light source, a single-mode fiber, an optical fiber circulator, an optical fiber 1 multiplied by 2 coupler, a fiber integrated coupler, a double-core optical fiber, a three-core optical fiber, an end surface reflecting film, piezoelectric ceramics, a photoelectric detector, a data acquisition card, a computer and a piezoelectric ceramics control system. The three fiber cores of the three-core optical fiber form two interferometers, and the two interferometers are overlapped to form a vernier effect for sensing. The interferometer composed of the double-core optical fiber is wound on the piezoelectric ceramics for signal demodulation. When the sensing signal changes, the computer analyzes the collected signal and feeds back the signal to the piezoelectric ceramic control system to regulate and control the signal of the double-core optical fiber interferometer, so that the detected signal returns to the initial state. The invention realizes signal demodulation by regulating and controlling the piezoelectric ceramic, and simultaneously generates vernier effect by superposition of three-core optical fiber spectra, thereby increasing the sensitivity of the system and being applicable to the technical field of optical fiber signal demodulation.
Description
Technical Field
The invention relates to a three-core fiber parallel type interference sensor based on dual-core fiber demodulation, and belongs to the technical field of fiber demodulation.
Background
The optical interferometry is a technique based on the principle of light wave interferometry, and has been widely used in the measurement field. Optical interferometry has higher sensitivity and accuracy than conventional optical measurement methods. Any physical quantity such as bending, temperature, strain, refractive index, displacement, vibration, pressure, temperature, etc., can be measured by the optical fiber interferometer as long as it can be represented by a change in the optical path difference of the optical fiber.
With the increasing demands of modern technologies on sensors, the rapid development of integrated optical waveguide sensors has been driven to meet the demands for rapid and specific detection of physical properties of mechanical, biological, chemical, etc. substances. Unlike the conventional optical fiber sensor, the integrated optical fiber sensor can be easily miniaturized, and thus it is possible to perform large-scale integration in a small area to realize a miniaturized experimental platform. Over the past several decades, many different configurations of fiber optic sensors have been obtained for various physical parameters. In general, these conventional sensors can meet the basic requirements for physical parameter detection.
In recent years, certain special application fields put higher demands on the sensitivity of optical fiber temperature and strain sensors, and researchers start to further apply vernier effect as a sensitization means in optical detection. The vernier effect is originally a phenomenon that the measuring sensitivity is improved by utilizing the tiny scale difference between the main scale and the vernier in the vernier caliper, and the vernier effect is applied to optical fiber sensing, so that the sensitivity and the dynamic range of the optical fiber interferometer can be improved simultaneously. The vernier effect is applicable to interferometers having periodic spectra, and in order to create the vernier effect, two interferometers having close free spectral ranges are typically cascaded. In the spectrum after cascade connection, the contrast ratio at the same phase position is higher, the contrast ratio at the phase position phase difference pi is very low, so that a large envelope is formed, the sensitivity and the dynamic range are obviously amplified, and the amplification factor depends on the dynamic range proximity degree.
In patent CN 113959606A, a hybrid transverse pressure sensor based on cascade enhancement vernier effect is proposed, where a Fabry-Perot interferometer and a Michelson interferometer are cascaded, the Fabry-Perot interferometer is used as a reference portion, the Michelson interferometer is used as a sensing portion, and free spectral ranges of the two interferometers are controlled during manufacturing, so that two interference signals are superimposed to form the vernier effect. When the interference fringes of the Fabry-Perot interferometer and the Michelson interferometer move in opposite directions due to the change of the external environment, the large interference envelope presents an enhanced vernier effect, and the transverse pressure is measured by extracting and demodulating the interference spectrum.
Patent CN 110057389A proposes an optical fiber sensor based on the side hole optical fiber dual mach-zehnder interference vernier effect, which utilizes a single mode optical fiber, a coreless optical fiber and a side hole optical fiber to form a dual mach-zehnder structure. Light transmitted along the single-mode fiber enters the fiber core of the side hole fiber, the hole communicated with the external environment and the closed hole through the coreless fiber. The three light paths are combined at the second coreless fiber and transmitted to the spectrometer through the single mode fiber. The fiber core of the side hole optical fiber is interfered with the light of the two holes at the same time to form a double Mach-Zehnder interferometer, the interferometer formed by the fiber core and the closed hole is used as a reference part, and the interferometer formed by the hole communicated with the external environment is used as a sensing part. The refractive index sensor has ultrahigh sensitivity.
However, the sensors for realizing the vernier effect of the optical fibers prepared at the present stage are all passive optical fiber devices, and the spectrum is not adjustable. And the demodulation means are large-scale equipment such as a spectrometer, and the like, so that the spectrum is firstly extracted and then the data analysis processing is carried out, the cost is high, the volume is huge, and the demodulation process is complex.
Disclosure of Invention
The invention aims to provide a three-core optical fiber parallel type interference sensor based on dual-core optical fiber interference demodulation, which omits large demodulation equipment such as a spectrometer and the like, has a simple overall structure and high integration level, and has the advantages that the three-core optical fiber interferometer forms a vernier effect, the sensitivity is high, the demodulation is performed through piezoelectric ceramic control voltage, and the response speed is high.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a three-core optical fiber parallel type interference sensor based on dual-core optical fiber interference demodulation. The device consists of a light source, a single-mode fiber, an optical fiber circulator, an optical fiber 1 multiplied by 2 coupler, a fiber integrated coupler, a double-core optical fiber, a three-core optical fiber, an end surface reflecting film, piezoelectric ceramics, a photoelectric detector, a data acquisition card, a computer and a piezoelectric ceramics control system. The three fiber cores of the three-core optical fiber form two interferometers with similar free spectrums, and the interferometers are overlapped to form a vernier effect for sensing. The interferometer composed of the double-core optical fiber is wound on the piezoelectric ceramics for signal demodulation. When the measured parameters change, the spectrum of the three-core optical fiber interferometer changes, so that the finally output optical signal changes, the photoelectric detector detects the output signal, the data acquisition card transmits the detected result to the data processing unit, the data processing unit analyzes the result and feeds back the result to the piezoelectric ceramic control system, the piezoelectric ceramic control system adjusts the voltage applied to the piezoelectric ceramic, the interference spectrum of the dual-core optical fiber interferometer changes, the finally detected signal is identical to the initial signal, and the demodulation of the sensing signal is realized by applying the voltage by utilizing the voltage-sensing quantity curve obtained by calibration in advance.
The light source is a tunable laser with narrow linewidth.
The fiber integrated coupler is manufactured by welding single-mode fibers with double-core fibers and three-core fibers respectively and then adopting modes of fusion tapering or thermal diffusion and the like, and plays roles of beam splitting and beam combining. Light transmitted along a single-mode fiber can be dispersed into each fiber core in a specific light splitting ratio after passing through the coupler, then the light transmitted by each fiber core is reversely transmitted through the end surface reflecting film, and the light is combined through the fiber integrated coupler to generate interference, so that a dual-core optical fiber Michelson interferometer and a three-core optical fiber Michelson interferometer are formed, and the system comprises a plurality of interferometers connected in parallel.
The dual-core optical fiber has two fiber cores, and the two fiber cores are not coupled during transmission.
The three-core optical fiber forms a parallel optical fiber interferometer through the fiber integrated coupler, and a vernier effect can be formed after spectrum superposition.
The dual-core optical fiber Michelson interferometer is wound on the piezoelectric ceramic to serve as a demodulation part, the three-core optical fiber Michelson interferometer serves as a sensing part and is used for detecting external environment parameters, and the two interferometers are connected through the optical fiber 1 multiplied by 2 coupler.
The piezoelectric ceramics can deform after voltage is applied, and can be single piezoelectric ceramics or combined by a plurality of piezoelectric ceramics with different elastic coefficients according to the change range of the detected sensing parameters.
Light emitted by the light source is transmitted to a dual-core optical fiber Michelson interferometer and a three-core optical fiber Michelson interferometer which are connected in parallel through an optical fiber 1X 2 coupler, and the spectrum of the dual-core optical fiber interferometer can be adjusted through piezoelectric ceramics; the three-core optical fiber is overlapped by two interferometers with similar free spectrums to form a vernier effect, so that the sensing sensitivity is amplified. When the measured parameters change, the optical signals output by the optical fiber circulator change, the photoelectric detector detects the output signals, the data acquisition card transmits the detected results to the data processing unit, the data processing unit analyzes the results and feeds back the results to the piezoelectric ceramic control system, the piezoelectric ceramic control system adjusts the voltage applied to the piezoelectric ceramic to control the interference spectrum change of the dual-core optical fiber interferometer, the finally detected signals are identical to the initial signals, and the demodulation of the sensing signals is realized by reading the voltage applied to the piezoelectric ceramic by utilizing a voltage-sensing quantity curve obtained by pre-calibration.
The principle used by the invention is as follows:
according to the light superposition principle, when two columns of monochromatic light waves are superposed, the emergent light intensity I is as follows:
wherein: i 1 And I 2 Is the light intensity of two columns of monochromatic light waves,the phase difference of two rows of light waves is:
to make two rows of light waves overlap each other and interfere each other, it is necessary to simultaneously satisfy that the frequencies of the two light waves are the same; the vibration directions of the two light waves at the meeting position are the same; the two light waves have a fixed phase difference at the meeting position. In an optical fiber, the phase difference between different light waves can be expressed as:
wherein Deltan is eff The effective refractive index of the mode for transmitting light waves in the optical fiber, delta L is the length difference of the transmission of two light waves, and lambda is the wavelength of input light. From the above equation, the output light intensity will change correspondingly with the change of the incident wavelength. When (when)Interference maxima occur when +.>At this time, an interference minimum occurs. The spacing of two adjacent peaks or valleys in the output spectrum is known as the Free Spectral Range (FSR) and can be approximated as:
when the difference between FSRs of the two interferometer resonance spectrums is not great, formants forming the transmission spectrums are overlapped and generate envelope signals of one period, so that vernier effect is formed, and the sensing sensitivity is amplified.
Assuming that the interference spectrums of the two interferometers are respectively
A and C are the non-interfering components of the two interferometers, respectively. B and D are the amplitudes of the two interferometers, respectively.And->The phases of the two interferometers are respectively represented and are related to the optical path difference between the interference optical paths in the interferometers. When the equivalent interferometers are connected in parallel, the output spectrum after superposition is as follows:
at this time, the FSR of the cascade interferometer is:
as can be seen from the above equation, the dynamic range of the interferometer is amplified, and compared with the interferometer 1, the dynamic range amplification factor is:
in addition to the vernier effect, which amplifies the dynamic range, the sensing sensitivity is also amplified. In sensing, assuming a first interferometer is used for sensing and a second interferometer is used as a reference, when the environment changes, the envelope shifts by an amount that satisfies:
it can be seen that the sensitivity is amplified by the factor:
if the sign of the sensitivity is not taken into account, the vernier effect has the same magnification factor for the dynamic range as the sensitivity and is determined only by the FSR of the two independent interferometers.
When the sensor is prepared, the spectrum of the dual-core optical fiber interferometer is ensured to have the same FSR as the envelope of the interference spectrum after the vernier effect is generated by the three-core optical fiber interferometer, and the pre-applied voltage is adjusted so as to facilitate demodulation, so that the wavelength at the spectral trough of the dual-core interferometer wound on the piezoelectric ceramic corresponds to the wavelength at the spectral peak of the envelope after the vernier effect is formed by the three-core interferometer, namely the wavelength at the trough of the demodulation interferometer is the same as the wavelength at the envelope peak of the three-core optical fiber interferometer.
Before the sensing measurement is carried out by using the method, the system is calibrated to obtain a voltage-sensing quantity correlation curve. When the measurement is carried out, light emitted by the light source is detected by the photoelectric detector after passing through the interferometer connected in parallel, and is uploaded to the data processing unit through the data acquisition card, and the data processing unit records an initial signal; when the external environment changes, the spectrum of the three-core optical fiber interferometer shifts, so that the signal detected by the photoelectric detector changes, the computer analyzes the signal, the result is fed back to the piezoelectric ceramic control unit, the voltage applied to the piezoelectric ceramic is changed, the spectrum of the dual-core optical fiber interferometer is adjusted, the interference spectrum of the parallel interferometer is changed, the finally detected signal is identical to the initial signal, the applied voltage is read, the variable quantity of the sensing quantity is obtained according to the calibrated curve, and the demodulation function is realized.
The beneficial effects of the invention are as follows:
1. the demodulation is realized by using a piezoelectric ceramic regulation and control means, large-scale equipment such as a spectrometer and the like are not needed, the integration level of the system is improved, and the data operation in the demodulation process is simplified;
2. the two cascade interferometers are connected through the optical fiber coupler, so that the distance between the two cascade interferometers can be long, and the problem that the demodulation interferometers are easily affected by sensing quantity is solved.
Drawings
FIG. 1 is a schematic diagram of a three-core fiber parallel interferometric sensor based on dual-core fiber interferometric demodulation;
FIG. 2 (a) is a schematic diagram of an asymmetric twin-core optical fiber structure, and FIG. 2 (b) is a schematic diagram of a symmetric twin-core optical fiber structure;
FIG. 3 (a) is a schematic diagram of a three-core optical fiber having cores arranged in a linear fashion, and FIG. 3 (b) is a schematic diagram of a three-core optical fiber having cores arranged in a triangular fashion;
FIG. 4 (a) is a three-core fiber interferometer spectrum, and FIG. 4 (b) is a two-core fiber interferometer spectrum;
fig. 5 is a spectrum of the two interferometers superimposed.
In the figure: 1. a light source; 2. a single mode optical fiber; 3. an optical fiber circulator; 4. an optical fiber 1 x 2 coupler; 5-1, 5-2, fiber integrated coupler; 6. a dual-core optical fiber; 7. a three-core optical fiber; 8. an end surface reflection film; 9. piezoelectric ceramics; 10. a photodetector; 11. a data acquisition card; 12. a computer; 13. a piezoelectric ceramic controller.
Detailed Description
For the purpose of promoting an understanding of the principles and advantages of the invention, reference will now be made to the drawings in which there will be illustrated, by way of illustration, and not as an actual or complete description, the embodiments of the invention. All other embodiments, based on the described embodiments, which a person of ordinary skill in the art would obtain without making any inventive effort, are within the scope of the invention.
The invention discloses a three-core optical fiber parallel type interference sensor based on dual-core optical fiber interference demodulation, which takes Michelson interferometer parallel connection as an example, and has the structure shown in figure 1, and consists of a light source, a single-mode optical fiber, an optical fiber circulator, an optical fiber 1 multiplied by 2 coupler, a fiber integrated coupler, dual-core optical fibers, three-core optical fibers, an end surface reflecting film, piezoelectric ceramics, a photoelectric detector, a data acquisition card, a computer and a piezoelectric ceramics control system. The dual-core optical fiber comprises two fiber cores, and typical dual-core optical fiber core arrangement is shown in fig. 2, wherein fig. 2 (a) is an asymmetric dual-core optical fiber, and fig. 2 (b) is a symmetric dual-core optical fiber. The dual-core optical fiber used in this embodiment is an asymmetric dual-core optical fiber. The three-core optical fiber comprises three fiber cores, the typical three-core optical fiber core arrangement is shown in fig. 3, fig. 3 (a) is a three-core optical fiber with fiber cores arranged in a linear manner, and fig. 3 (b) is a three-core optical fiber with fiber cores arranged in a triangular manner. The three-core optical fiber with the fiber cores in linear arrangement is used in the embodiment, the refractive indexes of the three fiber cores are different, wherein the refractive index difference of two fiber cores is far smaller than the refractive index difference of the two fiber cores and the other fiber core, when the three fiber cores form the interferometer, the FSR of the interferometer formed by the fiber cores with the smaller refractive index difference is far larger than the FSR of the other two interferometers, so that the influence of the interferometer on vernier effect is small and can be ignored.
Firstly, preparing a dual-core optical fiber interferometer, preparing a fiber integrated coupler by adopting a thermal diffusion technology, and firstly, welding a single-mode fiber with a dual-core optical fiber in a core-to-core manner, wherein the middle core can be completely connected with the single-mode fiber in the core-to-core manner due to the asymmetric dual-core optical fiber, so that a heating mode for the dual-core optical fiber can be adopted when thermal diffusion is carried out. And (3) placing a section of double-core optical fiber on the central shaft of a heating area of the furnace for heat diffusion treatment, and heating for a certain time to gradually change the concentration distribution of the medium-core dopant in the heat diffusion area of the double-core optical fiber into quasi-Gaussian distribution so as to realize the coupling of light beams. The length of the heating zone of the furnace is usually above the order of centimeters, ensuring that the refractive index in the gradient temperature field changes slowly to a quasi-gaussian distribution. After the fiber integrated coupler is prepared, a gold film is prepared on the end face of the double-core optical fiber through an ion sputtering technology for signal reflection so as to realize the preparation of a Michelson interferometer. The same method was used to prepare a three-core fiber interferometer.
The three-core optical fiber interferometer is used as a sensing interferometer for measuring external parameters, the spectrum of the three-core optical fiber interferometer is shown in fig. 4 (a), and the FSR of the spectrum envelope after superposition is 80nm. The dual-core optical fiber interferometer is used as a demodulation interferometer, is wound on the piezoelectric ceramic, and the voltage of the piezoelectric ceramic is regulated, so that the FSR of the dual-core optical fiber interferometer is 80nm as the envelope FSR of the three-core optical fiber interferometer, the wavelength of the trough of the dual-core optical fiber is as the same as the wavelength of the wave crest of the envelope of the three-core optical fiber interferometer, and the spectrum is shown in fig. 4 (b). The two interferometers are connected through the optical fiber 1×2 coupler, and the spectrum after superposition of the two interferometers is shown in fig. 5. By adjusting the light source output wavelength, the incident wavelength is made to be the wavelength at the trough of the spectral envelope of the three-core fiber optic interferometer, as indicated by the circle in fig. 5.
The parts are first connected as shown in fig. 1 and calibrated by known sensing variables. When the calibration is carried out, the photoelectric detector detects the light intensity when the sensing parameters are unchanged and records the light intensity as an initial value; then the determined sensing variable quantity is applied to the sensing interferometer, at the moment, the light intensity detected by the photoelectric detector can be changed, the data acquisition card uploads detected data to the computer, the computer applies voltage to the piezoelectric ceramic through the piezoelectric ceramic controller, the spectrum of the demodulation interferometer is changed, the signal detected by the photoelectric detector is changed, the finally detected signal value is the same as the initial value through adjusting the applied voltage, the currently applied voltage value is recorded and corresponds to the known sensing variable quantity, and the curve related to the applied voltage and the sensing variable quantity is finally obtained through changing the sensing variable quantity, so that the calibration of the system is realized.
When the system is used for sensing measurement, the sensing optical fiber is placed in an environment to be detected, when the measuring environment changes, the detection signal changes, the detected signal is finally the same as the initial value through continuously adjusting the applied voltage, the voltage value at the moment is read, and the change amount of the environment is determined through a curve calibrated in advance.
Claims (4)
1. The three-core fiber parallel type interference sensor based on the dual-core fiber interference demodulation consists of a light source, a single-mode fiber, a fiber circulator, a fiber 1 multiplied by 2 coupler, a fiber integrated coupler, a dual-core fiber, a three-core fiber, an end surface reflecting film, piezoelectric ceramics, a photoelectric detector, a data acquisition card, a computer and a piezoelectric ceramics control system; three fiber cores of the three-core optical fiber form two interferometers with similar free spectrums, and a vernier effect is formed by superposition and is used for sensing; the interferometer formed by the double-core optical fiber is wound on the piezoelectric ceramics and is used for signal demodulation; when the measured parameters change, the output optical signals change, the photoelectric detector detects the output signals, the data acquisition card transmits the detected results to the computer, the computer analyzes the results and feeds back the results to the piezoelectric ceramic control system, the piezoelectric ceramic control system adjusts the voltage applied to the piezoelectric ceramic, so that the interference spectrum of the dual-core optical fiber interferometer changes, the finally detected signals are the same as the initial signals, and the demodulation of the sensing signals is realized by applying the voltage by utilizing the voltage-sensing quantity curve obtained by calibration in advance.
2. The three-core fiber parallel interferometric sensor based on dual-core fiber interferometric demodulation of claim 1, wherein the sensor is characterized by: the light source is a tunable laser with narrow linewidth.
3. The three-core fiber parallel interferometric sensor based on dual-core fiber interferometric demodulation of claim 1, wherein the sensor is characterized by: the three-core optical fiber can form a parallel optical fiber interferometer through the fiber integrated coupler, and the spectrums of the three-core optical fiber can be overlapped to form a vernier effect.
4. The three-core fiber parallel interferometric sensor based on dual-core fiber interferometric demodulation of claim 1, wherein the sensor is characterized by: the piezoelectric ceramic can be a single piezoelectric ceramic or a combination of a plurality of piezoelectric ceramics with different elastic coefficients.
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