FP demodulation system based on piezoelectric ceramic dynamic scanning

Abstract

The invention discloses an FP demodulation system based on piezoelectric ceramic dynamic scanning, and belongs to the field of optical fiber sensors. The problem that an existing MEMS optical fiber FP pressure sensor demodulation system is difficult to achieve high precision while achieving high-speed measurement is solved. Broadband light output by a broadband light source enters an FP pressure sensor to be measured through an optical fiber circulator, enters a first collimating lens through the optical fiber circulator after being reflected by the FP pressure sensor to be measured, sequentially penetrates through a first plane mirror, a second plane mirror and a second collimating lens after being collimated by the first collimating lens, and then is transmitted to the FP pressure sensor to be measured. A detection signal generated after the light enters the photoelectric detector and is subjected to photoelectric conversion is sent to the upper computer through the data acquisition card; the upper computer acquires a driving signal output by the signal generator through the data acquisition card; and the upper computer calculates the detection signal according to the driving signal and the mapping relation between the driving signal and the displacement so as to obtain the variable quantity of the FP cavity of the FP pressure sensor to be detected. The method is mainly applied to the field of pressure detection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical fiber sensors. BACKGROUND

[0002] The MEMS fiber FP pressure sensor has the advantages of strong anti-electromagnetic interference ability, simple structure, high sensitivity, low preparation cost, and suitability for extreme harsh environments. It is currently widely researched and applied in aerospace engines, gas turbines, petrochemical industry, industrial control and other fields. The MEMS fiber FP pressure sensor is usually composed of an FP interference structure formed by the end face of the optical fiber and the surface of the sensitive structure. When the sensitive structure changes under the action of the measured quantity, the interference spectrum signal of the FP interference structure changes. Therefore, the FP demodulation system is one of the core key devices of the MEMS fiber FP pressure sensor.

[0003] In the FP demodulation system, the emitted light of the light source part is incident into the FP pressure sensor, and the reflected light carries information about the FP cavity length. After the photoelectric conversion device, the reflected light is sent into the computer for operation processing, so as to obtain the FP cavity length information, and then obtain the measured quantity. The common FP demodulation system usually has two schemes, which are intensity demodulation scheme and phase demodulation scheme. In the intensity demodulation scheme, narrow-band light is generally used as probe light, and photoelectric detector is used to receive light intensity information, so as to obtain the change information of the cavity length by measuring the change of the output light intensity. The patent "Fiber F-P sensor vibration demodulation system and method based on polarization switching" proposes a polarization switching F-P sensor vibration signal demodulation system, which realizes the same light source, photoelectric detection and two-way interference signal demodulation on the same light path, and effectively overcomes the problem of light path imbalance in the traditional dual-wavelength demodulation system. The patent "Three-wavelength fiber Fabry-Perot acoustic sensor demodulation method and system based on phase compensation" proposes to construct two-way orthogonal signals by processing three-way signals, which realizes the problem of demodulation precision decline when the cavity length changes greatly. However, the above two methods need to use ellipse fitting algorithm in application, which leads to the weak demodulation ability of the demodulation system to small signals, that is, low demodulation precision.

[0004] The intensity-based demodulation scheme has the advantages of low cost and fast demodulation speed, but the demodulation precision is low, usually only 5% FS, and is easily affected by the external environment.

[0005] In the phase demodulation scheme, a broadband light is generally used as the probe light, a spectrum analyzer is used to collect the interference spectrum signal of the FP pressure sensor, and an algorithm is used to extract the absolute cavity length information of the FP cavity. The correlation algorithm and the fast Fourier transform are the most commonly used demodulation algorithms. However, the correlation algorithm has the defect of large amount of calculation, and the fast Fourier transform has the problem of low demodulation accuracy. In the patent 'Variable Step Size Fast High Precision Signal Demodulation Method of Fiber F-P Sensor', a demodulation technology combining the fast Fourier transform and the correlation algorithm is proposed, which improves the cavity length resolution while improving the demodulation speed. Another scheme is to use a wedge structure combined with a linear array CCD for hardware correlation demodulation, as described in the patent 'Fiber Fabry-Perot Sensor Demodulation System and Method'. This scheme avoids the use of expensive spectrum receiving devices and has the advantage of compact structure. However, due to the limitations of the pixel size and acquisition speed of the linear array CCD, the demodulation speed and accuracy of this scheme are difficult to meet the needs of high-speed and high-precision demodulation.

[0006] The phase-based demodulation scheme has high demodulation accuracy, which can reach 0.1% FS, but the demodulation speed is slow, only reaching the order of hundreds of hertz, and the cost is high.

[0007] With the development of new generation aerospace engines and gas turbines, the control system needs to be more accurate, so the sensor needs to be able to meet the needs of high-speed measurement while achieving high precision. SUMMARY

[0008] In view of the problem that the existing MEMS fiber FP pressure sensor demodulation system cannot achieve high-speed measurement while achieving high precision, the present application provides a FP demodulation system based on piezoelectric ceramic dynamic scanning.

[0009] The FP demodulation system based on piezoelectric ceramic dynamic scanning comprises an upper computer, a signal generator, a piezoelectric ceramic driver, a broadband light source, a fiber optic circulator, a first collimating lens, a first plane mirror, a piezoelectric ceramic vibrator, a second plane mirror, a second collimating lens, a photodetector and a data acquisition card.

[0010] The first plane mirror and the second plane mirror form an interference cavity, and the first plane mirror is fixed on the piezoelectric ceramic vibrator.

[0011] The driving signal output by the signal generator is used to control the piezoelectric ceramic vibrator to stretch and contract in the horizontal direction through the piezoelectric ceramic driver, so as to change the displacement of the interference cavity, wherein the driving signal and the displacement have a mapping relationship.

[0012] The broadband light output by the broadband light source is incident on the to-be-tested FP pressure sensor through the optical fiber circulator, is reflected by the to-be-tested FP pressure sensor, is incident on the first collimating lens through the optical fiber circulator, is transmitted through the first plane mirror, the second plane mirror and the second collimating lens in sequence after being collimated by the first collimating lens, is incident on the photodetector to generate a detection signal after photoelectric conversion, and the detection signal is sent to the upper computer through the data acquisition card; the upper computer also collects a driving signal output by a signal generator through the data acquisition card;

[0013] The upper computer calculates the detection signal according to the driving signal and the mapping relationship between the driving signal and the displacement amount, and obtains the change amount of the FP cavity of the to-be-tested FP pressure sensor.

[0014] Preferably, the implementation manner in which the upper computer calculates the detection signal according to the driving signal and the mapping relationship between the driving signal and the displacement amount, and obtains the change amount of the FP cavity of the to-be-tested FP pressure sensor is as follows:

[0015] The upper computer aligns the received detection signal and the driving signal, and obtains a voltage sequence corresponding to the detection signal and a pressure sequence corresponding to the driving signal;

[0016] According to the mapping relationship between the driving signal and the displacement amount, a displacement sequence corresponding to the pressure sequence is obtained;

[0017] The displacement sequence is taken as the abscissa, and the voltage sequence is taken as the ordinate, so as to construct a correlation curve between the voltage and the displacement;

[0018] The maximum voltage in the correlation curve is found, and the displacement corresponding to the maximum voltage is taken as the change amount of the FP cavity of the to-be-tested FP pressure sensor.

[0019] Preferably, the bandwidth range of the broadband light source is C band or C+L band.

[0020] Preferably, the incident light surface and the emergent light surface of the first plane mirror are parallel, the incident light surface is coated with an anti-reflection film of C band or C+L band, and the emergent light surface is not coated with a film.

[0021] Preferably, the thickness range of the first plane mirror is 300 microns to 500 microns.

[0022] Preferably, the piezoelectric ceramic vibrator is made of PZT material, and the vibration frequency range is 1 Hz to 10 kHz.

[0023] Preferably, the incident light surface and the emergent light surface of the second plane mirror are parallel, the incident light surface is coated with an anti-reflection film of C band or C+L band, and the emergent light surface is not coated with a film.

[0024] Preferably, the thickness range of the second plane mirror is 300 microns to 500 microns.

[0025] Preferably, the distance between the first plane mirror and the second plane mirror ranges from 50 microns to 200 microns.

[0026] Advantages of the present application:

[0027] The present application designs a demodulation system based on hardware cavity length matching, utilizes a large-stroke high-speed piezoelectric ceramic to construct a fast tunable interference cavity, makes the interference cavity length match with a pressure-sensitive FP cavity of a fiber sensor, then utilizes a photodetector to collect light intensity information, so that length information of the pressure-sensitive FP cavity can be obtained at high speed, so that high dynamic range demodulation of the fiber FP pressure sensor is realized.

[0028] The demodulation system of the present application utilizes a piezoelectric ceramic to drive a tunable interference cavity, under specific signal driving, the piezoelectric ceramic can realize high-speed and nanometer-level step distance movement, so that the demodulation scheme improves measurement precision while ensuring measurement speed. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structural schematic diagram of the FP demodulation system based on piezoelectric ceramic dynamic scanning according to the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0032] The present application will be further described below in combination with the drawings and specific embodiments, but is not limited by the present application.

[0033] DETAILED DESCRIPTION Figure 1 The present embodiment provides an FP demodulation system based on piezoelectric ceramic dynamic scanning, which comprises a host computer 1, a signal generator 2, a piezoelectric ceramic driver 3, a broadband light source 4, a fiber circulator 6, a first collimating lens 7, a first plane mirror 8, a piezoelectric ceramic vibrator 9, a second plane mirror 10, a second collimating lens 11, a photodetector 12 and a data acquisition card 13.

[0034] An interference cavity is formed between the first plane mirror 8 and the second plane mirror 10, and the first plane mirror 8 is fixed on the piezoelectric ceramic vibrator 9.

[0035] The driving signal output by the signal generator 2 controls the piezoelectric ceramic vibrator 9 to stretch and contract in the horizontal direction through the piezoelectric ceramic driver 3, so as to change the displacement of the interference cavity, wherein the driving signal and the displacement have a mapping relationship;

[0036] The broadband light output by the broadband light source 4 is incident on the to-be-tested FP pressure sensor 5 through the optical fiber circulator 6, is reflected by the to-be-tested FP pressure sensor 5, is incident on the first collimating lens 7 through the optical fiber circulator 6, is collimated by the first collimating lens 7, and then is transmitted through the first plane mirror 8, the second plane mirror 10 and the second collimating lens 11 in sequence, and is incident on the photodetector 12 to generate a detection signal through photoelectric conversion, and the detection signal is sent to the host computer 1 through the data acquisition card 13; the host computer 1 also collects the driving signal output by the signal generator 2 through the data acquisition card 13.

[0037] The host computer 1 calculates the detection signal according to the driving signal and the mapping relationship between the driving signal and the displacement, and obtains the change amount of the FP cavity of the to-be-tested FP pressure sensor 5.

[0038] In the embodiment, a large-stroke high-speed piezoelectric ceramic is used to construct a fast tunable interference cavity, which is matched with the pressure-sensitive FP cavity of the fiber sensor in length, and then the light intensity information is collected by the photodetector, so that the length information of the pressure-sensitive FP cavity can be obtained at a high speed, thereby realizing high-precision and large-dynamic-range demodulation of the fiber FP pressure sensor.

[0039] In a specific application, the piezoelectric ceramic vibrator 9 is made of PZT material, and the vibration frequency range is 1 Hz to 10 kHz.

[0040] Further, the host computer 1 calculates the detection signal according to the driving signal and the mapping relationship between the driving signal and the displacement, and obtains the change amount of the FP cavity of the to-be-tested FP pressure sensor 5.

[0041] After the host computer 1 aligns the received detection signal and the driving signal, a voltage sequence corresponding to the detection signal and a pressure sequence corresponding to the driving signal are obtained.

[0042] According to the mapping relationship between the driving signal and the displacement, a displacement sequence corresponding to the pressure sequence is obtained.

[0043] The displacement sequence is taken as the abscissa, and the voltage sequence is taken as the ordinate, so as to construct a correlation curve between the voltage and the displacement.

[0044] The maximum voltage in the correlation curve is found, and the displacement corresponding to the maximum voltage is taken as the change amount of the FP cavity of the to-be-tested FP pressure sensor 5.

[0045] In the preferred embodiment, the implementation of obtaining the variation of FP cavity is given, which has the advantage of realizing high-precision measurement while ensuring the measurement speed. In specific application, the bandwidth range of the broadband light source 4 is C band or C+L band. The bandwidth range of the C band is 1525nm-1565nm, the bandwidth range of the L band is 1565nm-1625nm, and the bandwidth range of the C+L band is 1525nm-1625nm.

[0046] Further, the incident light surface and the emergent light surface of the first plane mirror 8 are parallel, and the incident light surface is coated with an anti-reflection film of C band or C+L band, and the emergent light surface is not coated. The thickness of the first plane mirror 8 ranges from 300 microns to 500 microns.

[0047] In the preferred embodiment, the two surfaces of the first plane mirror 8, one of which is coated and the other is not, transmit the optical signal, which has the advantage of improving the utilization efficiency of the optical signal, and limits the thickness range of the first plane mirror 8. The advantage of this thickness is to avoid parasitic interference and signal light crosstalk.

[0048] Further, the incident light surface and the emergent light surface of the second plane mirror 10 are parallel, and the incident light surface is coated with an anti-reflection film of C band or C+L band, and the emergent light surface is not coated. The thickness of the second plane mirror 10 ranges from 300 microns to 500 microns.

[0049] In the preferred embodiment, the two surfaces of the second plane mirror 10, one of which is coated and the other is not, transmit the optical signal, which has the advantage of improving the utilization efficiency of the signal light, and limits the thickness range of the second plane mirror 10. The advantage of this thickness is to avoid parasitic interference and signal light crosstalk.

[0050] Further, the distance between the first plane mirror 8 and the second plane mirror 10 ranges from 50 microns to 200 microns. The distance between the two plane mirrors defined can be accurately matched with the sensor pressure FP cavity.

[0051] Although the present application is described herein with reference to particular embodiments, it is to be understood that these examples are merely illustrative of principles and applications of the present application. It should therefore be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present application as defined by the appended claims. It should be understood that the features described in connection with one embodiment can be used in conjunction with other embodiments described herein. It should be understood that the features described in connection with one embodiment can be used in conjunction with other embodiments described herein.

Claims

1. A FP demodulation system based on piezoelectric ceramic dynamic scanning, characterized in that, The system comprises an upper computer (1), a signal generator (2), a piezoelectric ceramic driver (3), a broadband light source (4), a fiber optic circulator (6), a first collimating lens (7), a first plane mirror (8), a piezoelectric ceramic vibrator (9), a second plane mirror (10), a second collimating lens (11), a photodetector (12) and a data acquisition card (13); An interference cavity is formed between the first plane mirror (8) and the second plane mirror (10), and the first plane mirror (8) is fixed on the piezoelectric ceramic vibrator (9); The driving signal output by the signal generator (2) controls the piezoelectric ceramic vibrator (9) to stretch and contract in the horizontal direction through the piezoelectric ceramic driver (3), so as to change the displacement of the interference cavity, wherein the driving signal and the displacement have a mapping relationship. The broadband light output by the broadband light source (4) is incident on the to-be-measured FP pressure sensor (5) through the fiber optic circulator (6), is reflected by the to-be-measured FP pressure sensor (5), is incident on the first collimating lens (7) through the fiber optic circulator (6), is collimated by the first collimating lens (7), and then passes through the first plane mirror (8), the second plane mirror (10) and the second collimating lens (11) in sequence, and is incident on the photodetector (12) to generate a detection signal after photoelectric conversion, and the detection signal is sent to the upper computer (1) through the data acquisition card (13); the upper computer (1) also collects the driving signal output by the signal generator (2) through the data acquisition card (13); The upper computer (1) calculates the detection signal according to the driving signal and the mapping relationship between the driving signal and the displacement, and obtains the change amount of the FP cavity of the to-be-measured FP pressure sensor (5).

2. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, characterized in that, The implementation of the upper computer (1) calculating the change amount of the FP cavity of the to-be-measured FP pressure sensor (5) according to the driving signal and the mapping relationship between the driving signal and the displacement is as follows: After the upper computer (1) aligns the received detection signal and driving signal, a voltage sequence corresponding to the detection signal and a pressure sequence corresponding to the driving signal are obtained; According to the mapping relationship between the driving signal and the displacement, a displacement sequence corresponding to the pressure sequence is obtained; The displacement sequence is taken as the abscissa and the voltage sequence is taken as the ordinate to construct a correlation curve between the voltage and the displacement; The maximum voltage value in the correlation curve is found, and the displacement corresponding to the maximum voltage value is taken as the change amount of the FP cavity of the to-be-measured FP pressure sensor (5).

3. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, characterized in that, The bandwidth range of the broadband light source (4) is C band or C+L band.

4. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, characterized in that, The incident light surface and the exit light surface of the first plane mirror (8) are parallel, and the incident light surface is coated with an anti-reflection film of C band or C+L band, and the exit light surface is not coated.

5. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 4, characterized in that, The thickness of the first plane mirror (8) ranges from 300 microns to 500 microns.

6. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, wherein, The piezoelectric ceramic vibrator (9) is made of PZT material, and the vibration frequency ranges from 1 Hz to 10 kHz.

7. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, wherein, The incident light surface and the exit light surface of the second plane mirror (10) are parallel, and the incident light surface is coated with an anti-reflection film of C band or C+L band, and the exit light surface is not coated.

8. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 7, characterized in that, The thickness of the second plane mirror (10) ranges from 300 microns to 500 microns.

9. The piezoelectric ceramic dynamic scanning based FP demodulation system according to claim 1, characterized in that, The distance between the first mirror (8) and the second mirror (10) is in the range of 50 microns to 200 microns.

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