Self-adaptive optical fiber Fabry-Perot sensor demodulation device and working method thereof

Abstract

The invention discloses a self-adaptive optical fiber Fabry-Perot sensor demodulation device and a working method thereof. The self-adaptive optical fiber Fabry-Perot sensor demodulation device comprises an adjustable wavelength light source, a photoelectric detector, a low-pass filter, a high-pass fixed gain amplifier, a high-pass continuous variable gain amplifier and a controller. The demodulation device obtains the phase sensitivity of the Fabry-Perot sensor by scanning the adjustable wavelength light source and detecting the interference curve of the Fabry-Perot sensor on the basis of a stable working point method, and enables an output analog signal to have a determined phase sensitivity relationship by adjusting the high-pass continuous variable gain amplifier. The device can automatically adapt to Fabry-Perot sensors with inconsistent parameters, so that the output phase sensitivity or vibration displacement sensitivity coefficient is stable; the device is suitable for low-fineness and high-fineness Fabry-Perot sensors, and has the characteristics of real-time analog signal output and convenience for being integrated as a module.

Description

Technical Field

[0001] The present invention relates to an adaptive fiber optic Fabry - Perot sensor demodulation device and its working method, belonging to the field of fiber optic sensing technology. Background Art

[0002] Due to its characteristics of insulation, small size, light weight, fast response, high sensitivity, etc., fiber optic Fabry - Perot sensors are widely used in the measurement of physical quantities such as acoustic waves and vibrations in the fields of electric power, aviation, ocean, etc. Changes in the length of the Fabry - Perot cavity or the refractive index in the cavity will cause changes in the Fabry - Perot interference phase. By detecting the changes in the Fabry - Perot cavity interference phase, physical quantities to be measured such as vibrations and acoustic waves can be obtained.

[0003] Common phase demodulation methods for Fabry - Perot cavities include white light interference, spectrometer analysis, phase carrier generation, operating point control, etc. Among them, the operating point control method is widely used because of its simple principle structure, fast response, analog signal output, good real - time performance, and easy integration as a module.

[0004] However, due to the high - sensitivity characteristics of Fabry - Perot sensors, slight differences in the cavity length and reflectivity of Fabry - Perot sensors will cause changes in the sensitivity of the sensors themselves. Therefore, the working sensitivities of Fabry - Perot sensors of the same specification are usually inconsistent. In addition, when the same Fabry - Perot sensor is connected to the demodulation device in different scenarios, such as differences in optical path joint alignment and different degrees of fiber bending, it will also cause changes in the sensitivity of the sensor itself. Therefore, when a Fabry - Perot sensor is connected to a demodulation device for signal (phase / displacement) measurement, it is difficult to have a definite proportional relationship between the output voltage amplitude and the input signal amplitude of the sensor. This results in the need for separate calibration of each sensor before the demodulation device is used. This calibration usually requires additional devices to cooperate and is completed through known external excitation. Calibrating with externally built excitation equipment is a time - consuming and complicated task.

[0005] Therefore, those skilled in the art are urgently required to solve the technical problems that existing demodulation devices are difficult to be universal for Fabry - Perot sensors with different parameters, it is difficult to give a stable phase sensitivity using a demodulation method with a stable operating point, and the calibration work is complex. Summary of the Invention

[0006] Objective: In order to overcome the deficiencies in the prior art, the present invention provides an adaptive fiber optic Fabry - Perot sensor demodulation device and its working method, which can automatically measure the interference characteristic curve of the Fabry - Perot sensor, automatically realize the calibration process of the phase sensitivity, and can make the analog output signal have a fixed voltage - phase sensitivity relationship, overcoming the problem of inconsistent sensitivities of Fabry - Perot sensors. It also has the characteristics of real - time analog signal output and is convenient for integration as a module.

[0007] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] In the first aspect, an adaptive fiber optic Fabry-Perot sensor demodulation device includes: a tunable wavelength light source, a photodetector, a low-pass filter, a high-pass fixed-gain amplifier, a high-pass continuously variable gain amplifier, and a controller.

[0009] Among them, the tunable wavelength light source is used to output a light source signal with an adjustable output light wavelength.

[0010] The photodetector is used to convert the reflected light interference signal into an electrical signal.

[0011] The low-pass filter is used to filter out the high-frequency signals to be measured in the electrical signal to obtain a filtered signal.

[0012] The high-pass fixed-gain amplifier is used to amplify the high-frequency ultrasonic waves or high-frequency vibration signals to be measured in the electrical signal to obtain an interferometric signal after gain.

[0013] The high-pass continuously variable gain amplifier is used to change the output gain of the interferometric signal after gain according to the instruction of the controller to obtain an interferometric signal after gain with the final output sensitivity.

[0014] The controller is used to continuously adjust the wavelength of the light source signal within the adjustment range of the tunable wavelength light source, so that the Fabry-Perot sensor outputs an interference curve for testing the Fabry-Perot sensor, calculate the current phase sensitivity of the Fabry-Perot sensor according to the interference curve of the filtered signal; adjust the working wavelength of the light source signal in real time to stabilize the working point and the current phase sensitivity of the Fabry-Perot sensor; adjust the gain ratio of the high-pass continuously variable gain amplifier according to the current phase sensitivity of the Fabry-Perot sensor.

[0015] Optionally, the adjustment range of the tunable wavelength light source is greater than the free spectral range of the Fabry-Perot sensor.

[0016] Optionally, the high-pass fixed-gain amplifier changes the gain amplitude by adjusting the gear.

[0017] In the second aspect, a working method of an adaptive fiber optic Fabry-Perot sensor demodulation device specifically includes:

[0018] Step 1, the controller outputs the working wavelength of this interval point by point according to the adjustment range of the tunable wavelength light source at time intervals.

[0019] Step 2, the tunable wavelength light source outputs a light source signal of the working wavelength of this interval according to the working wavelength of this interval.

[0020] Step 3, the Fabry-Perot sensor outputs a reflected light interference signal corresponding to the light source signal of the working wavelength of this interval according to the light source signal of the working wavelength of this interval.

[0021] Step 4, the photodetector outputs an electrical signal according to the received reflected light interference signal.

[0022] Step 5, the low-pass filter outputs a filtered signal according to the electrical signal and transmits it to the controller.

[0023] Step 6, repeat Steps 1 to 5. The controller obtains the filtered signal sequences corresponding to all working wavelengths; obtains the electrical signal with the largest curve slope in the filtered signal sequences, calculates the working voltage corresponding to the electrical signal with the largest curve slope as the reference voltage value, and takes the maximum value of the curve slope as the phase sensitivity of the current Fabry-Perot sensor.

[0024] Step 7, the controller adjusts the working wavelength of the tunable wavelength light source according to the reference voltage value, so that the output voltage of the filtered signal output by the low-pass filter is equal to the reference voltage value.

[0025] Step 8, obtain the electrical signal of the photodetector at the current moment, input the electrical signal into the high-pass fixed-gain amplifier to obtain the amplified interference signal.

[0026] Step 9, the controller calculates the gain magnification according to the phase sensitivity of the current Fabry-Perot sensor and the reference phase sensitivity, and transmits the gain magnification to the high-pass continuously variable gain amplifier.

[0027] Step 10, the high-pass continuously variable gain amplifier outputs the amplified interference signal with the final output sensitivity according to the amplified interference signal and the gain magnification.

[0028] Optionally, it further includes Step 11, calculating the final output sensitivity according to the gain magnification and the phase sensitivity of the current Fabry-Perot sensor, and calculating the displacement sensitivity of the Fabry-Perot sensor according to the final output sensitivity.

[0029] Optionally, the period of the filtered signal sequence is at least one interference fringe period.

[0030] Optionally, the method for calculating the maximum value of the curve slope is as follows:

[0031] Discretize the filtered signal sequence of one period into M scanning points, and calculate the derivative value of each scanning point respectively. The expression of the derivative value is as follows:

[0032]

[0033] Among them, is the voltage change amount between two adjacent scanning points, is the phase interval between two adjacent scanning points, is the derivative value of the scanning point.

[0034] Take the maximum value of the derivative value as the maximum value of the curve slope.

[0035] Optionally, the expression of the gain magnification is as follows:

[0036]

[0037] Wherein, is the gain magnification, is the reference phase sensitivity, is the phase sensitivity of the current Fabry - Perot sensor.

[0038] Optionally, the expression of the final output sensitivity is as follows:

[0039]

[0040] Wherein, is the final output sensitivity, is the phase sensitivity of the current Fabry - Perot sensor, is the gain magnification.

[0041] Optionally, the expression of the displacement sensitivity is as follows:

[0042]

[0043] Wherein, is the displacement sensitivity, is the final output sensitivity, is the laser operating wavelength of the tunable wavelength light source, is the refractive index of the medium in the Fabry - Perot sensor cavity, is the pi.

[0044] Beneficial effects: An adaptive fiber optic Fabry - Perot sensor demodulation device and its working method provided by the present invention can automatically adapt to Fabry - Perot sensors with inconsistent parameters, making the output phase sensitivity or vibration displacement sensitivity coefficient stable, applicable to low - finesse and high - finesse Fabry - Perot sensors. At the same time, it has the characteristics of real - time analog signal output and is convenient to be integrated as a module.

[0045] Furthermore, based on the stable - operating - point method, the present invention scans the tunable wavelength light source to detect the interference curve of the Fabry - Perot sensor, thereby obtaining the phase sensitivity of the Fabry - Perot sensor.

[0046] Furthermore, by adjusting the high - pass continuously variable gain amplifier, the output analog signal has a definite phase sensitivity relationship.

[0047] Compared with the prior art, the advantages of the present invention are as follows:

[0048] 1. The present invention provides a demodulation device that does not require calibration. After the demodulation device is connected to a sensor, it does not need an external device to apply a known excitation signal for calibration.

[0049] 2. After the demodulation device of the present invention is powered on and started, it can automatically analyze the key structural parameters of the currently connected Fabry-Perot sensor and obtain the sensitivity coefficient, and then start the measurement work.

[0050] 3. For the convenience of modular integration, the demodulation device adjusts the voltage gain of the output signal according to the different sensor sensitivities obtained by automatic analysis to match different sensor sensitivities, so that there is a definite proportional relationship between the measured input signal and the final output amplitude, which is convenient to be integrated into the measurement system as a module. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic structural diagram of an adaptive fiber optic Fabry-Perot sensor demodulation device of the present invention.

[0052] Figure 2 It is a schematic structural diagram of an embodiment of a variable gain amplifier.

[0053] Figure 3 It is a schematic diagram of the scanning spectral curve of a low-finesse Fabry-Perot sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0055] The following further describes the present invention with reference to specific embodiments.

[0056] Embodiment 1:

[0057] This embodiment introduces an adaptive fiber optic Fabry-Perot sensor demodulation device, as Figure 1 shown, including: a tunable wavelength light source, a photodetector, a low-pass filter, a high-pass fixed gain amplifier, a high-pass continuously variable gain amplifier, and a controller.

[0058] Among them, the tunable wavelength light source is used to output a light source signal with an adjustable output light wavelength.

[0059] Further, the adjustment range of the tunable wavelength light source is greater than the fringe period of the Fabry-Perot sensor, that is, the free spectral range of the Fabry-Perot sensor: .

[0060] Among them, is the laser operating wavelength of the tunable wavelength light source, is the refractive index of the medium in the Fabry-Perot sensor cavity (1 for air medium), is the length of the Fabry-Perot sensor cavity.

[0061] Further, the tunable wavelength light source transmits a light source signal to the Fabry-Perot sensor through an optical fiber.

[0062] The photodetector is used to convert the reflected light interference signal output by the Fabry-Perot sensor into an electrical signal.

[0063] The low-pass filter is used to filter out the measured high-frequency signals in the electrical signal to obtain a filtered signal with a stable and smooth interference curve of the electrical signal. This avoids the influence of high-frequency signal fluctuations on the interference curve when testing the electrical signal of the Fabry-Perot sensor.

[0064] The high-pass fixed-gain amplifier is used to amplify the measured high-frequency ultrasonic waves or high-frequency vibration signals in the electrical signal to obtain an interferometric signal after gain. Since the signals such as high-frequency vibration and sound waves measured by the Fabry-Perot sensor may be relatively weak, by using a high-pass fixed-gain amplifier, the sensitivity of the Fabry-Perot sensor can be improved and the test ability of weak signals can be enhanced.

[0065] Further, the high-pass fixed-gain amplifier changes the gain amplitude by adjusting the gear, such as multiple gears of 1 times, 10 times, 100 times, etc. Among them, the high-pass fixed-gain amplifier does not make continuous adjustments and can accept external manual control. Most of the time, its magnification gain is fixed.

[0066] The high-pass continuously variable gain amplifier is used to change the output gain of the interferometric signal after gain according to the instructions of the controller, compensate for the phase sensitivity difference caused by the structural parameters of the Fabry-Perot sensor and the optical path loss parameters, and obtain an interferometric signal after gain with the final output sensitivity.

[0067] Further, the gain ratio of the high-pass continuously variable gain amplifier is continuously adjustable, or the adjustment ratio division is less than the set threshold.

[0068] Further, the gain ratio is a value automatically calculated by the controller according to the interference curve, and the gain ratio of the high-pass continuously variable gain amplifier is controlled to be adjusted.

[0069] The controller is used to continuously adjust the wavelength of the light source signal within the adjustment range of the tunable wavelength light source, so that the Fabry-Perot sensor outputs an interference curve for testing the Fabry-Perot sensor, calculates the current phase sensitivity of the Fabry-Perot sensor according to the interference curve of the filtered signal; adjusts the working wavelength of the light source signal in real time to stabilize the working point and the current phase sensitivity of the Fabry-Perot sensor; adjusts the gain ratio of the high-pass continuously variable gain amplifier according to the current phase sensitivity of the Fabry-Perot sensor.

[0070] Example 2:

[0071] This example introduces a working method of an adaptive fiber optic Fabry-Perot sensor demodulation device, specifically including:

[0072] Step 1, the controller outputs the working wavelength of this interval point by point according to the adjustment range of the tunable wavelength light source at intervals of △ time interval, where the value range of is [1, N], and N represents the total number of adjustment points in the adjustment range.

[0073] Step 2, the tunable wavelength light source outputs a light source signal of the working wavelength of this interval according to the working wavelength of this interval . The light source signal of the working wavelength of this interval

[0074] Step 3, the Fabry-Perot sensor outputs an interference signal of the reflected light corresponding to the light source signal of the working wavelength of this interval according to the light source signal of the working wavelength of this interval . The interference signal of the reflected light corresponding to the light source signal of the working wavelength of this interval

[0075] Step 4, the photodetector outputs an electrical signal according to the received interference signal of the reflected light.

[0076] Step 5, the low-pass filter outputs a filtered signal according to the electrical signal and transmits it to the controller.

[0077] Step 6, repeat Steps 1 to 5, and the controller obtains a sequence of filtered signals corresponding to all working wavelengths; obtain the electrical signal with the largest curve slope in the sequence of filtered signals, and calculate the working voltage corresponding to the electrical signal with the largest curve slope as the reference voltage value Vref, and take the maximum value of the curve slope as the phase sensitivity of the current Fabry-Perot sensor. Among them, the sequence of filtered signals is used as the interference curve of the Fabry-Perot sensor. The electrical signal with the largest curve slope is used as the working point of the interference curve of the Fabry-Perot sensor.

[0078] Step 7, the controller adjusts the working wavelength of the tunable wavelength light source according to the reference voltage value Vref so that the output voltage of the filtered signal output by the low-pass filter is equal to the reference voltage value Vref. In this way, both the working point and the sensitivity of the Fabry-Perot sensor are stabilized.

[0079] Step 8, obtain the electrical signal of the photodetector at the current moment, and input the electrical signal into a high-pass fixed-gain amplifier to obtain an interfered signal after gain.

[0080] Step 9, the controller calculates the gain magnification according to the phase sensitivity of the current Fabry-Perot sensor and the reference phase sensitivity, and transmits the gain magnification to the high-pass continuously variable gain amplifier.

[0081] Step 10: The high-pass continuous variable gain amplifier outputs the gain interferogram signal of the final output sensitivity according to the gain interferogram signal and the gain ratio.

[0082] Further, it also includes Step 11: Calculate the final output sensitivity according to the gain ratio and the phase sensitivity of the current Fabry-Perot sensor, and calculate the displacement sensitivity of the Fabry-Perot sensor according to the final output sensitivity.

[0083] Further, the period of the filtered signal sequence is at least one interference fringe period.

[0084] Further, the method for calculating the maximum value of the curve slope is as follows:

[0085] Discretize the filtered signal sequence of one period into M scanning points, and calculate the derivative value of each scanning point respectively. The expression of the derivative value is as follows:

[0086] (V / rad)

[0087] Where, is the voltage change amount between two adjacent scanning points, is the phase interval between two adjacent scanning points, is the derivative value of the scanning point.

[0088] Take the maximum value of the derivative value as the maximum value of the curve slope.

[0089] Further, the working voltage value of the scanning point corresponding to the maximum value of the derivative value is used as the reference voltage value Vref.

[0090] Further, the expression of the gain ratio is as follows:

[0091]

[0092] Where, is the gain ratio, is the reference phase sensitivity, is the phase sensitivity of the current Fabry-Perot sensor.

[0093] Further, the expression of the final output sensitivity is as follows:

[0094] (V / rad)

[0095] Where, is the final output sensitivity, is the phase sensitivity of the current Fabry-Perot sensor, is the gain magnification factor. It is used to compensate the phase sensitivity of the current Fabry-Perot sensor, so that the final output sensitivity of the Fabry-Perot sensor in the current scenario can be stabilized under the reference phase sensitivity.

[0096] Furthermore, the expression of the displacement sensitivity is as follows:

[0097] (V / nm)

[0098] where, is the displacement sensitivity, is the final output sensitivity, is the laser operating wavelength of the tunable wavelength light source, is the refractive index of the medium in the Fabry-Perot sensor cavity, is the pi.

[0099] Embodiment 3:

[0100] This embodiment introduces a specific embodiment of an adaptive fiber optic Fabry-Perot sensor demodulation device, which specifically includes:

[0101] Tunable wavelength light source, a tunable laser can be selected, including but not limited to semiconductor vertical cavity surface emitting lasers (VCSEL type), and can also be DFB (distributed feedback laser), DBR (distributed Bragg reflector laser), or fiber laser. The output is in the form of a single-mode fiber. It can also be a fiber laser composed of a tunable optical filter, etc.

[0102] The operating wavelength adjustment range of the tunable wavelength light source is 20 - 30 nm, and the wavelength center can be around 1550 nm. The tunable laser can change the output optical wavelength under the control of a varying voltage signal.

[0103] Fabry-Perot sensor, which can be a diaphragm-type EFPI (extrinsic fiber Fabry-Perot) sensor, generating vibrations under the action of sound waves and vibrations. The fiber end face and the sound-sensitive diaphragm form a Fabry-Perot interference cavity. The cavity length varies from 200 to 400 microns, the reflectivity of the front end face is about 4%, and the reflectivity of the rear end face is about 90%.

[0104] Photodetector, which converts the optical signal into a corresponding current signal and then converts it into a voltage signal for output. Its type is InGaAs (indium gallium arsenide) type.

[0105] Low-pass filter, which can be a low-pass filter composed of RC (resistor, capacitor). The cut-off frequency of the low-pass filter can be designed below 10 Hz, which can avoid the influence of the measured high-frequency vibration and can also effectively track the change of the environmental temperature influence.

[0106] The high-pass fixed-gain amplifier is designed to be applicable to a frequency range of test signals from several tens of Hz to several hundreds of kHz. The amplification factors can be 1, 10, 100, etc., and can be set externally through commands via the controller, which serves to select the measurement range and enhance the test sensitivity of weak signals.

[0107] The high-pass continuously variable gain amplifier is automatically adjusted under the action of the controller. The implementation method is as Figure 2 shown. Preferably, it is realized in cooperation with the digital control digital potentiometer model MCP41010 and the operational amplifier LM7332. For the digital potentiometer MCP41010, the intermediate output terminal W forms continuously variable resistances with the two ends A and B of the potentiometer respectively, and adopts a three-wire SPI interface. The controller can change the resistance changes between the intermediate output terminal W and the two ends A and B of the potentiometer through the communication interface. By controlling the data to change the resistance ratio of B - W to A - W, the output gain of the amplifier is changed.

[0108] The controller can use the single-chip microcomputer MSP430F169. This single-chip microcomputer has functions such as analog-to-digital conversion AD acquisition, digital-to-analog DA conversion output, and an SPI communication port, etc. The voltage signal output by DA can be used to control the working wavelength of the tunable wavelength light source. When there is a mismatch in magnitude between the DA voltage of the single-chip microcomputer and the control voltage of the laser, a voltage amplifier can be added for matching adjustment. The single-chip microcomputer AD acquires the output of the low-pass filter to realize the data acquisition of the interference spectral curve. The SPI interface controls the digital potentiometer in the high-pass continuously variable gain amplifier, and adjusts the output gain by changing the resistance ratio between WA - WB.

[0109] Embodiment 4:

[0110] This embodiment introduces the working principle of a working method of an adaptive fiber Fabry-Perot sensor demodulation device, specifically including:

[0111] The demodulation device is connected to the Fabry-Perot sensor through an optical fiber, and the demodulation device is started.

[0112] The controller - single-chip microcomputer MSP430F169 outputs continuously increasing voltage values through DA. These voltage values can be used to control the working wavelength of the tunable wavelength light source to increase (or decrease) at equal time intervals (such as an interval of △ = 0.1 nm). At the same time, each time the working wavelength is changed, the single-chip microcomputer acquires the current voltage value of the output of the low-pass filter through AD. After the scanning is completed, an interference curve regarding the Fabry-Perot sensor is obtained. The number of scanning points can be 100, 200, etc. As Figure 3 shown, for the Fabry-Perot sensor composed of low reflectivity, the low-finesse interference curve is approximately a cosine function curve. For the high-finesse interference curve, it is an Airy function curve.

[0113] After obtaining the interference curve data, there are two functions. One is to obtain the working point position of the Fabry-Perot sensor, and the other is to calculate the current phase sensitivity of the Fabry-Perot sensor. By analyzing the spectral curve, the position with the maximum curve slope is theoretically the working point. Therefore, the voltage value Vref at this position of the curve can be used as the reference point of the working point for real-time tracking. The so-called tracking is to finely adjust the tunable wavelength light source in real time to keep it always at the Vref value. The main purpose is to eliminate the influence of environmental slow variables such as temperature and air pressure on the Fabry-Perot sensor.

[0114] The controller performs differential calculation on the collected interference curve and queries the maximum difference value (for example, it is ). The interference curve value at the point corresponding to the maximum difference value is used as the reference voltage Vref of the working point. The single-chip microcomputer then performs cyclic tracking, monitoring the output of the low-pass filter in real time. When the output is lower or higher than the reference voltage Vref, the working wavelength is increased or decreased to keep the output of the low-pass filter always at the reference voltage Vref state, realizing the real-time tracking stability of the working point.

[0115] When calculating the phase sensitivity according to the interference curve, the number of scanning points included in one period needs to be queried. The period points M are obtained by querying the point interval between two adjacent maximum values or minimum values in the curve. The phase interval of the scanning points can be obtained as . The phase sensitivity of the Fabry-Perot sensor can be obtained as: . This algorithm is applicable to the interference curves of both low-precision and high-precision Fabry-Perot sensors. For the interference curve with low finesse, since it is approximately a cosine curve, the current phase sensitivity can also be obtained according to the amplitude and period of the cosine curve.

[0116] The gain of the high-pass fixed-gain amplifier is used for gear adjustment (×1, ×10, ×100). This value can be set by an external manual instruction and is used as a fixed known quantity. Here, it can be assumed to be set to ×1.

[0117] Due to different optical losses during the process of replacing the probe or installing the same Fabry-Perot sensor. It is different after each installation. Suppose the phase sensitivities k1 of the Fabry sensor during three installations are 0.8 V / rad, 1.0 (V / rad), and 1.5 (V / rad) respectively. Then, k = 1 V / rad can be artificially set as the output reference phase sensitivity of the demodulation device. Then, the controller calculates k1 based on the interference curve and will automatically set the gain of the high-pass continuously variable gain amplifier to: 1 / 0.8, 1, 1 / 1.5 to compensate for the sensitivity differences of the Fabry sensor itself. The specific setting process is to adjust the MCP41010 chip through the SPI interface, and the resistance ratio between W and B to the resistance between W and A is: 1 / 0.8, 1, 1 / 1.5. In this way, even if the probes are different or the connection conditions are different, it can ensure that the phase sensitivity of the device system is 1 V / rad, achieving the purpose of system stability and accurate measurement.

[0118] Stable output sensitivity coefficient: Due to differences in the cavity length and reflectivity of the Fabry sensor, etc., the corresponding relationship between the interference light intensity and the phase of the Fabry sensor directly is different. The current differences in phase sensitivity are very inconvenient for subsequent integrated device applications. The method to stabilize the final output sensitivity of the device is to calculate the current phase sensitivity of the Fabry sensor based on the Fabry interference curve. , for a batch of different probes There is a large dispersion, usually within 10 times. According to its dispersion, a desired reference phase sensitivity is artificially determined. As the fixed output sensitivity of the device, then the gain of the high-pass continuously variable gain amplifier needs to be set to: (V / rad).

[0119] Obviously, when the final output phase sensitivity is stable, according to the current laser wavelength, its output vibration displacement sensitivity (V / nm) is also stable. Achieving stable amplitude measurement.

[0120] Based on the stable operating point method, the present invention scans a tunable wavelength light source to detect the interference curve of the Fabry sensor, thereby obtaining the current phase sensitivity of the Fabry sensor. Further, by adjusting the high-pass continuously variable gain amplifier, the output analog signal has a definite phase sensitivity relationship. The present invention has the characteristics of being able to automatically adapt to Fabry sensors with inconsistent parameters, making the output phase sensitivity or vibration displacement sensitivity coefficient stable; being applicable to low-finesse and high-finesse Fabry sensors, and at the same time, having real-time analog signal output and being convenient to be integrated as a module.

[0121] The above are only the preferred embodiments of the present invention. It should be pointed out that: for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An adaptive fiber Fabry - Perot sensor demodulation device, characterized in that: Comprising: An adjustable wavelength light source, a photodetector, a low-pass filter, a high-pass fixed-gain amplifier, a high-pass continuously variable-gain amplifier, and a controller; Among them, the adjustable wavelength light source is used to output a light source signal with an adjustable output optical wavelength; The photodetector is used to convert the reflected light interference signal into an electrical signal; The low-pass filter is used to filter out the measured high-frequency signal in the electrical signal to obtain a filtered signal; The high-pass fixed-gain amplifier is used to amplify the measured high-frequency ultrasonic wave or high-frequency vibration signal in the electrical signal to obtain an interferometric signal after gain; The high-pass continuously variable-gain amplifier is used to change the output gain of the interferometric signal after gain according to the instruction of the controller to obtain an interferometric signal after gain with the final output sensitivity; The controller is used to continuously adjust the wavelength of the light source signal within the adjustment range of the adjustable wavelength light source, so that the Fabry-Perot sensor outputs an interference curve for testing the Fabry-Perot sensor, and calculates the current phase sensitivity of the Fabry-Perot sensor according to the interference curve of the filtered signal; Real-time adjust the working wavelength of the light source signal to stabilize the working point and the current phase sensitivity of the Fabry-Perot sensor; According to the current phase sensitivity of the Fabry-Perot sensor, adjust the gain ratio of the high-pass continuously variable-gain amplifier.

2. The demodulation device for an adaptive fiber Fabry-Perot sensor according to claim 1, characterized in that: The adjustment range of the adjustable wavelength light source is greater than the free spectral range of the Fabry-Perot sensor.

3. An adaptive fiber optic Fabry-Perot sensor demodulation device according to claim 1, characterized in that: The high-pass fixed-gain amplifier changes the gain amplitude by adjusting the gear.

4. The working method of an adaptive fiber Fabry-Perot sensor demodulation device according to any one of claims 1 to 3, characterized in that: Specifically including: Step 1, the controller outputs the working wavelength of this interval point by point according to the adjustment range of the adjustable wavelength light source at time intervals; Step 2, the adjustable wavelength light source outputs a light source signal of the working wavelength of this interval according to the working wavelength of this interval; Step 3, the Fabry-Perot sensor outputs a reflected light interference signal corresponding to the light source signal of the working wavelength of this interval according to the light source signal of the working wavelength of this interval; Step 4, the photodetector outputs an electrical signal according to the received reflected light interference signal; Step 5, the low-pass filter outputs a filtered signal according to the electrical signal and transmits it to the controller; Step 6, repeat steps 1 to 5, and the controller obtains a sequence of filtered signals corresponding to all working wavelengths; Obtain the electrical signal with the largest curve slope in the filtered signal sequence, and calculate the working voltage corresponding to the electrical signal with the largest curve slope as the reference voltage value, and use the maximum value of the curve slope as the current phase sensitivity of the Fabry-Perot sensor; Step 7, the controller adjusts the working wavelength of the adjustable wavelength light source according to the reference voltage value so that the output voltage of the filtered signal output by the low-pass filter is equal to the reference voltage value; Step 8, obtain the electrical signal of the photodetector at the current moment, and input the electrical signal into the high-pass fixed-gain amplifier to obtain an interferometric signal after gain; Step 9, the controller calculates the gain ratio according to the current phase sensitivity of the Fabry-Perot sensor and the reference phase sensitivity, and transmits the gain ratio to the high-pass continuously variable-gain amplifier; Step 10, the high-pass continuously variable-gain amplifier outputs an interferometric signal after gain with the final output sensitivity according to the interferometric signal after gain and the gain ratio.

5. The working method according to claim 4, characterized in that: It also includes step 11, calculating the final output sensitivity according to the gain ratio and the current phase sensitivity of the Fabry-Perot sensor, and calculating the displacement sensitivity of the Fabry-Perot sensor according to the final output sensitivity.

6. The working method according to claim 4, characterized in that: The period of the filtered signal sequence is at least one interference fringe period.

7. The working method according to claim 4, characterized in that: The method for calculating the maximum value of the curve slope is as follows: Discretize the filtered signal sequence of one period into M scanning points, and calculate the derivative value of each scanning point respectively. The expression of the derivative value is as follows: ； Among them, is the voltage change amount between two adjacent scanning points, is the phase interval between two adjacent scanning points, is the derivative value of the scanning point; Take the maximum value of the derivative value as the maximum value of the curve slope.

8. The working method according to claim 4, characterized in that: The expression of the gain magnification is as follows: ； Among them, is the gain magnification factor, is the reference phase sensitivity, is the phase sensitivity of the current Fabry-Perot sensor.

9. The working method according to claim 5, characterized in that: The expression of the final output sensitivity is as follows: ； wherein, is the final output sensitivity, is the phase sensitivity of the current Fabry-Perot sensor, is the gain magnification factor.

10. The working method according to claim 5, characterized in that: The expression of the displacement sensitivity is as follows: ； Among them, is the displacement sensitivity, is the final output sensitivity, is the laser operating wavelength of the tunable wavelength light source, is the refractive index of the medium in the Fabry-Perot sensor cavity, is the pi.

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