An adaptive fiber-optic fabry-perot sensor demodulation device and a working method thereof

Abstract

The application discloses a self-adaptive fiber-optic F-P sensor demodulation device and a working method thereof, a tunable 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 is based on a stable working point method, scans the tunable wavelength light source, detects an interference curve of the F-P sensor, thereby obtaining a phase sensitivity of the F-P sensor, and adjusts the high-pass continuous variable gain amplifier, so that the output analog signal has a determined phase sensitivity relationship. The application has the characteristics that the F-P sensor with inconsistent parameters can be automatically adapted, the output phase sensitivity or vibration displacement sensitivity coefficient is stable, the application is suitable for low-precision and high-precision F-P sensors, has real-time analog signal output, and is convenient for being integrated as a module.

Description

Technical Field

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

[0002] Fiber optic Fabry-Perot sensors are widely used in the measurement of physical quantities such as sound waves and vibrations in fields such as power, aviation, and marine engineering due to their insulation, small size, light weight, fast response, and high sensitivity. Changes in the length of the Fabry-Perot cavity or the refractive index within the cavity will cause changes in the Fabry-Perot interference phase. By detecting these changes in the interference phase, the measured physical quantities such as vibrations and sound waves can be obtained.

[0003] Common phase demodulation methods for Fabry-Perot cavities include white light interferometry, spectrometer analysis, phase carrier generation, and operating point control. Among these, the operating point control method is widely used due to its advantages such as simple principle and structure, fast response, analog signal output, good real-time performance, and ease of modular integration.

[0004] However, due to the high sensitivity of Fabry-Perot sensors, even slight differences in cavity length and reflectivity can lead to variations in sensitivity. Therefore, Fabry-Perot sensors of the same specifications often have inconsistent operating sensitivities. Furthermore, the sensitivity of the same Fabry-Perot sensor can also vary depending on the context in which it is connected to the demodulation device, such as differences in optical connector alignment or fiber optic bending. Consequently, when a Fabry-Perot sensor is used for signal (phase / displacement) measurement in a demodulation device, the output voltage amplitude is unlikely to have a definite proportional relationship with the sensor's input signal amplitude. This necessitates individual calibration of the demodulation device before using each sensor. Such calibration typically requires additional equipment and is performed using a known external excitation. Building an external excitation device for calibration is a time-consuming and complex process.

[0005] Therefore, those skilled in the art urgently need to solve the technical problems of existing demodulation devices being difficult to be universal for Fabry-Perot sensors with different parameters, the difficulty of providing stable phase sensitivity using demodulation methods with stable operating points, and the complexity of calibration work. Summary of the Invention

[0006] Objective: To overcome the shortcomings of existing technologies, this invention provides an adaptive fiber optic Fabry-Perot sensor demodulation device and its operating method. It can automatically measure the interference characteristic curve of the Fabry-Perot sensor, automatically perform the phase sensitivity calibration process, and ensure that the analog output signal has a fixed voltage-phase sensitivity relationship, overcoming the problem of inconsistent Fabry-Perot sensor sensitivity. It also features real-time analog signal output, facilitating 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 a 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 wavelength.

[0010] A photodetector is used to convert reflected light interference signals into electrical signals.

[0011] A low-pass filter is used to filter out the high-frequency signal being measured in an electrical signal, resulting in a filtered signal.

[0012] A high-pass fixed-gain amplifier is used to amplify the measured high-frequency ultrasonic wave or high-frequency vibration signal in an electrical signal to obtain the interference signal after gain.

[0013] A Qualcomm continuously variable gain amplifier is used to change the output gain of the post-gain interference signal according to the controller's instructions, so as to obtain the post-gain interference signal with the final output sensitivity.

[0014] The controller is used to continuously adjust the wavelength of the light source signal within the adjustable wavelength range of the light source, so that the Fabry-Perot sensor outputs the interference curve of the Fabry-Perot sensor, calculates the current phase sensitivity of the Fabry-Perot sensor based on 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 current phase sensitivity of the Fabry-Perot sensor, and adjusts the gain of the high-pass continuously variable gain amplifier based on the current phase sensitivity of the Fabry-Perot sensor.

[0015] Optionally, the adjustable wavelength light source has an adjustment range greater than the free spectrum range of the Fabry sensor.

[0016] Optionally, the gain amplitude of the Qualcomm fixed gain amplifier can be changed by adjusting the range.

[0017] Secondly, a method for operating an adaptive fiber optic Fabry-Perot sensor demodulation device specifically includes:

[0018] Step 1: The controller outputs the working wavelength of the current interval point by point according to the adjustment range of the adjustable wavelength light source at time intervals.

[0019] Step 2: The adjustable wavelength light source outputs a light source signal of the working wavelength of the current interval according to the working wavelength of the current interval.

[0020] Step 3: The Fabry sensor outputs the reflected light interference signal corresponding to the light source signal of the working wavelength of the current interval, based on the light source signal of the current interval.

[0021] Step 4: The photodetector outputs an electrical signal based on the received reflected light interference signal.

[0022] Step 5: The low-pass filter outputs a filtered signal based on the electrical signal and transmits it to the controller.

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

[0024] 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.

[0025] Step 8: Obtain the electrical signal of the photodetector at the current moment, input the electrical signal into a high-pass fixed-gain amplifier, and obtain the gain-adjusted interference signal.

[0026] Step 9: The controller calculates the gain ratio based on the current phase sensitivity of the Fabry sensor and the reference phase sensitivity, and transmits the gain ratio to the Qualcomm continuously variable gain amplifier.

[0027] Step 10: The Qualcomm continuously variable gain amplifier outputs the post-gain interference signal with the final output sensitivity based on the post-gain interference signal and the gain ratio.

[0028] Optionally, it also includes step 11, calculating the final output sensitivity based on the gain ratio and the current phase sensitivity of the Fabry sensor, and calculating the displacement sensitivity of the Fabry sensor based on 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 slope of the curve is as follows:

[0031] The filtered signal sequence of one period is discretized into M scan points, and the derivative value of each scan point is calculated. The expression for the derivative value is as follows:

[0032]

[0033] in, This represents the voltage change between two adjacent scan points. The phase interval between two adjacent scan points. This is the derivative value of the scan point.

[0034] The maximum value of the derivative is taken as the maximum slope of the curve.

[0035] Optionally, the expression for the gain ratio is as follows:

[0036]

[0037] in, This is the gain ratio. For reference phase sensitivity, This represents the phase sensitivity of the current Fabry-Perot sensor.

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

[0039]

[0040] in, For the final output sensitivity, The phase sensitivity of the current Fabry-Perot sensor, This represents the gain ratio.

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

[0042]

[0043] in, For displacement sensitivity, For the final output sensitivity, The operating wavelength of a laser is a tunable wavelength light source. The refractive index of the medium inside the Fabry-Perot sensor cavity. Pi is the mathematical constant of a circle.

[0044] Beneficial effects: The present invention provides an adaptive fiber optic Fabry-Perot sensor demodulation device and its working method. The present invention can automatically adapt to Fabry-Perot sensors with inconsistent parameters, so as to stabilize the output phase sensitivity or vibration displacement sensitivity coefficient. It is suitable for both low-precision and high-precision Fabry-Perot sensors. At the same time, it has the feature of real-time analog signal output, which makes it easy to be integrated as a module.

[0045] Furthermore, based on the stable operating point method, this invention obtains the phase sensitivity of the Fabry-Perot sensor by scanning an adjustable wavelength light source and detecting the interference curve of the Fabry-Perot sensor.

[0046] Furthermore, by adjusting the high-pass continuously variable gain amplifier, the output analog signal can be made to have a defined phase sensitivity relationship.

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

[0048] 1. This invention proposes a calibration-free demodulation device. After the demodulation device is connected to the sensor, it does not require external equipment to apply a known excitation signal for calibration.

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

[0050] 3. To facilitate modular integration, the demodulation device matches different sensor sensitivities by adjusting the voltage gain of the output signal based on the automatically analyzed sensor sensitivities, so that the measured input signal and the final output amplitude have a definite proportional relationship, making it easy to integrate as a module into the measurement system. Attached Figure Description

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

[0052] Figure 2 This is a schematic diagram of one embodiment of a variable gain amplifier.

[0053] Figure 3 This is a schematic diagram of the scanning spectrum curve of a low-precision Fabry-Perot sensor. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0055] The present invention will be further described below with reference to specific embodiments.

[0056] Example 1:

[0057] This embodiment describes an adaptive fiber optic Fabry-Perot sensor demodulation device, such as... Figure 1 As shown, it 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.

[0058] The adjustable wavelength light source is used to output a light source signal with an adjustable output wavelength.

[0059] Furthermore, the adjustable wavelength light source has an adjustment range greater than the fringe period of the Fabry-Perot sensor, i.e., the free spectral range of the Fabry-Perot sensor. .

[0060] in, The operating wavelength of a laser is a tunable wavelength light source. Let be the refractive index of the medium inside the Fabry-Perot sensor cavity (1 for air). This is the length of the Fabry sensor cavity.

[0061] Furthermore, the tunable wavelength light source transmits the light source signal to the Fabry sensor via an optical fiber.

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

[0063] The low-pass filter is used to filter out the high-frequency signal being measured in the electrical signal, resulting in a filtered signal with a stable and smooth electrical signal interference curve. This avoids the interference curve being affected by high-frequency signal fluctuations 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 wave or high-frequency vibration signal in the electrical signal to obtain the amplified interference signal. Since the high-frequency vibration and sound wave signals tested by the Fabry-Perot sensor may be relatively weak, using a high-pass fixed-gain amplifier can improve the sensitivity of the Fabry-Perot sensor and enhance its ability to test weak signals.

[0065] Furthermore, the Qualcomm fixed gain amplifier can change the gain amplitude by adjusting the level, such as 1x, 10x, 100x, etc. The Qualcomm fixed gain amplifier does not make continuous adjustments and can be controlled by external human intervention. Most of the time, its gain is fixed.

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

[0067] Furthermore, the gain of the high-pass continuously variable gain amplifier is continuously adjustable, or the adjustment increment is less than a set threshold.

[0068] Furthermore, the gain ratio is a value automatically calculated by the controller based on the interference curve, and the gain ratio of the high-pass continuously variable gain amplifier is adjusted accordingly.

[0069] 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 sensor outputs the interference curve of the Fabry sensor, calculates the current phase sensitivity of the Fabry sensor based on 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 current phase sensitivity of the Fabry sensor, and adjusts the gain of the high-pass continuously variable gain amplifier based on the current phase sensitivity of the Fabry sensor.

[0070] Example 2:

[0071] This embodiment describes the operation method of an adaptive fiber optic Fabry-Perot sensor demodulation device, specifically including:

[0072] Step 1, the controller uses △ The time interval is used to output the working wavelength of the current interval point by point according to the adjustment range of the adjustable wavelength light source. ,in, The value range is [1, N], where N represents the total number of adjustment points within the adjustment range.

[0073] Step 2, the adjustable wavelength light source operates according to the wavelength of this interval. Output the working wavelength of this interval The light source signal.

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

[0075] Step 4: The photodetector outputs an electrical signal based on the received reflected light interference signal.

[0076] Step 5: The low-pass filter outputs a filtered signal based on the electrical signal and transmits it to the controller.

[0077] Step 6: Repeat steps 1 to 5. The controller obtains the filtered signal sequences corresponding to all operating wavelengths; it acquires the electrical signal with the largest curve slope in the filtered signal sequence and calculates the operating voltage corresponding to the electrical signal with the largest curve slope as the reference voltage value Vref, and uses the maximum curve slope as the current phase sensitivity of the Fabry-Perot sensor. The filtered signal sequence serves as the interference curve of the Fabry-Perot sensor. The electrical signal with the largest curve slope is taken as the operating point of the Fabry-Perot sensor's interference curve.

[0078] Step 7: The controller adjusts the operating wavelength of the tunable wavelength light source according to the reference voltage value Vref, so that the output voltage of the filtered signal from the low-pass filter is equal to the reference voltage value Vref. This stabilizes the operating point and sensitivity of the Fabry-Perot sensor.

[0079] Step 8: Obtain the electrical signal of the photodetector at the current moment, input the electrical signal into a high-pass fixed-gain amplifier, and obtain the gain-adjusted interference signal.

[0080] Step 9: The controller calculates the gain ratio based on the current phase sensitivity of the Fabry sensor and the reference phase sensitivity, and transmits the gain ratio to the Qualcomm continuously variable gain amplifier.

[0081] Step 10: The Qualcomm continuously variable gain amplifier outputs the post-gain interference signal with the final output sensitivity based on the post-gain interference signal and the gain ratio.

[0082] Furthermore, it also includes step 11, calculating the final output sensitivity based on the gain ratio and the current phase sensitivity of the Fabry sensor, and calculating the displacement sensitivity of the Fabry sensor based on the final output sensitivity.

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

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

[0085] The filtered signal sequence of one period is discretized into M scan points, and the derivative value of each scan point is calculated. The expression for the derivative value is as follows:

[0086] (V / rad)

[0087] in, This represents the voltage change between two adjacent scan points. The phase interval between two adjacent scan points. This is the derivative value of the scan point.

[0088] The maximum value of the derivative is taken as the maximum slope of the curve.

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

[0090] Furthermore, the expression for the gain ratio is as follows:

[0091]

[0092] in, This is the gain ratio. For reference phase sensitivity, This represents the phase sensitivity of the current Fabry-Perot sensor.

[0093] Furthermore, the expression for the final output sensitivity is as follows:

[0094] (V / rad)

[0095] in, For the final output sensitivity, The phase sensitivity of the current Fabry-Perot sensor, This is the gain factor. It is used to compensate for the current phase sensitivity of the Fabry-Perot sensor, so that the final output sensitivity of the Fabry-Perot sensor in the current scene can be stabilized at the reference phase sensitivity.

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

[0097] (V / nm)

[0098] in, For displacement sensitivity, For the final output sensitivity, The operating wavelength of a laser is a tunable wavelength light source. The refractive index of the medium inside the Fabry-Perot sensor cavity. Pi is the mathematical constant of a circle.

[0099] Example 3:

[0100] This embodiment describes a specific implementation of an adaptive fiber optic Fabry-Perot sensor demodulation device, specifically including:

[0101] The tunable wavelength light source can be a tunable laser, including but not limited to semiconductor vertical-cavity surface-emitting lasers (VCSELs), as well as DFB (distributed feedback lasers), DBR (distributed Bragg reflector lasers), or fiber lasers. The output is in single-mode fiber form. Fiber lasers constructed with tunable optical filters can also be used.

[0102] The operating wavelength of a tunable light source can be adjusted within a range of 20-30 nm, with the center wavelength potentially around 1550 nm. A tunable laser can change its output wavelength under the control of a varying voltage signal.

[0103] A Fabry-Perot sensor, which can be a diaphragm-type EFPI (intrinsic fiber Fabry-Perot) sensor, vibrates under the influence of sound waves and vibrations. The fiber end face and the acoustically sensitive diaphragm constitute the Fabry-Perot interferometer cavity. The cavity length varies from 200 to 400 micrometers, with a front end reflectivity of about 4% and a rear end reflectivity of about 90%.

[0104] A photodetector converts light signals into corresponding current signals, and then into voltage signals for output. It is of the InGaAs (Indium Gallium Arsenide) type.

[0105] A low-pass filter can be an RC (resistor and capacitor) low-pass filter. The cutoff frequency of a low-pass filter can be designed below 10Hz, which can avoid the influence of the high-frequency vibration being measured and can also effectively track changes in ambient temperature.

[0106] The high-pass fixed-gain amplifier is designed to be suitable for test signals ranging from tens of Hz to hundreds of kHz. The amplification factor can be 1, 10, 100, etc., and can be set externally via commands and controller. It serves to select the measurement range and enhance the testing sensitivity of weak signals.

[0107] The high-pass continuously variable gain amplifier automatically adjusts under the control of the controller. Its implementation is as follows: Figure 2 As shown, a digital potentiometer, model MCP41010, and an operational amplifier, LM7332, are preferably used in conjunction. The MCP41010 digital potentiometer has its intermediate output terminal W connected to its terminals A and B, forming continuously variable resistances, and utilizes a three-wire SPI interface. The controller, through the communication interface, can change the resistance between the intermediate output terminal W and the potentiometer terminals A and B. By controlling the data and changing the ratio of the resistances BW and AW, the output gain of the amplifier is altered.

[0108] The controller can use the MSP430F169 microcontroller. This microcontroller has analog-to-digital (A / D) conversion and digital-to-analog (DA) conversion output functions, as well as an SPI communication port. The voltage signal output by the DA converter can be used to control the operating wavelength of the tunable wavelength light source. When there is a mismatch between the microcontroller's DA voltage and the laser control voltage, a voltage amplifier can be added for matching and adjustment. The microcontroller's A / D converter acquires the output of the low-pass filter to realize the data acquisition of the interference spectrum curve. The SPI interface controls the digital potentiometer in the high-pass continuously variable gain amplifier. The output gain is adjusted by changing the resistance ratio between WA and WB.

[0109] Example 4:

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

[0111] The demodulation device is connected to the Fabry sensor via optical fiber, and the demodulation device is started.

[0112] The controller, an MSP430F169 microcontroller, outputs continuously increasing voltage values ​​via a DA converter. These voltage values ​​can be used to control an adjustable wavelength light source at equal time intervals (e.g., Δ). The operating wavelength is changed incrementally (or incrementally) at intervals of 0.1 nm. Simultaneously, each time the operating wavelength is changed, the microcontroller acquires the current voltage value from the low-pass filter via an AD converter. After the scan is complete, an interference curve is obtained for the Fabry-Perot sensor. The number of scan points can be 100, 200, etc. Figure 3 As shown, for a Fabry-Perot sensor with low reflectivity, the low-resolution interferometric curve approximates a cosine function curve. For a high-resolution interferometric curve, it is an Airy function curve.

[0113] Obtaining the interference curve data serves two purposes: first, it allows us to determine the operating point of the Fabry-Perot sensor; second, it enables us to calculate the sensor's current phase sensitivity. Analyzing the spectral curve, the point with the steepest slope is theoretically the operating point. Therefore, the voltage value Vref at this point can be used as a reference point for real-time tracking. Tracking involves real-time fine-tuning of the tunable wavelength light source to maintain it at the Vref value. The primary purpose is to eliminate the influence of slowly changing environmental variables such as temperature and air pressure on the Fabry-Perot sensor.

[0114] The controller performs differential calculations on the acquired interference curves and queries the maximum value of the differential (e.g., ). The interference curve value at the point corresponding to the maximum differential value is used as the reference voltage Vref for the operating point. The microcontroller 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 operating wavelength is increased or decreased to keep the output of the low-pass filter at the reference voltage Vref, thus achieving real-time tracking and stability of the operating point.

[0115] When calculating phase sensitivity from an interference curve, it is necessary to look up the number of scan points within one period. The number of period points M is obtained by looking up the interval between two adjacent maximum or minimum values ​​in the curve. The phase interval of the scan points can then be calculated as follows: The phase sensitivity of the Fabry-Perot sensor can be obtained as follows: This algorithm is applicable to both low-precision and high-precision Fabry-Perot sensor interferometric curves. For low-precision interferometric curves, since they are approximately cosine curves, the current phase sensitivity can also be obtained from the amplitude and period of the cosine curve.

[0116] The gain of the Qualcomm fixed-gain amplifier is adjustable in increments (×1, ×10, ×100). This value can be set by external human command, and as a fixed known value, it can be assumed to be set to ×1 here.

[0117] The light loss can vary when changing the probe or installing the same Fabry-Perot sensor. Each installation is different. Assume the phase sensitivity k1 of the Fabry-Perot sensor installed three times is 0.8V / rad, 1.0V / rad, and 1.5V / rad respectively. Then, k=1V / rad can be manually set as the output reference phase sensitivity of the demodulation device. The controller calculates k1 based on the interference curve and then automatically sets 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-Perot sensor itself. Specifically, this setting is done by adjusting the MCP41010 chip via the SPI interface, with the resistance ratio between WB and WA being 1 / 0.8, 1, 1 / 1.5. This ensures that even with different probes or different connection conditions, the phase sensitivity of the device system is maintained at 1V / rad, achieving system stability and accurate measurement.

[0118] Stabilizing Output Sensitivity Coefficient: Due to differences in cavity length and reflectivity, the correspondence between the intensity and phase of the interference light directly transmitted by a Fabry-Perot sensor varies. This variation in current phase sensitivity is highly inconvenient for subsequent integrated device applications. The method for stabilizing the final output sensitivity of the device is to calculate the current phase sensitivity of the Fabry-Perot sensor based on the Fabry-Perot interference curve. For a batch of different probes There is significant dispersion, typically within 10 times. Based on this dispersion, a desired reference phase sensitivity is artificially determined. As a fixed output sensitivity for the device, the gain of the high-pass continuously variable gain amplifier needs to be set to: (V / rad).

[0119] Clearly, with the final output phase sensitivity stable, the output vibration displacement sensitivity (V / nm) is also stable based on the current laser wavelength, thus achieving stable amplitude measurement.

[0120] This invention, based on the stable operating point method, obtains the phase sensitivity of the Fabry-Perot sensor by scanning an adjustable wavelength light source and detecting the interference curve of the sensor. Further, by adjusting a high-pass continuously variable gain amplifier, the output analog signal achieves a definite phase sensitivity relationship. This invention automatically adapts to Fabry-Perot sensors with inconsistent parameters, stabilizing the output phase sensitivity or vibration displacement sensitivity coefficient. It is suitable for both low- and high-precision Fabry-Perot sensors and features real-time analog signal output, facilitating integration as a module.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adaptive fiber optic Fabry-Perot sensor demodulation device, characterized in that: include: Tunable wavelength light source, photodetector, low-pass filter, high-pass fixed gain amplifier, high-pass continuously variable gain amplifier and controller; Among them, the tunable wavelength light source is used to output a light source signal with an adjustable output light wavelength; A photodetector is used to convert reflected light interference signals into electrical signals. A low-pass filter is used to filter out the high-frequency signal being measured in an electrical signal, resulting in a filtered signal. A high-pass fixed-gain amplifier is used to amplify the measured high-frequency ultrasonic wave or high-frequency vibration signal in an electrical signal to obtain the interference signal after gain. A high-pass continuously variable gain amplifier is used to change the output gain of the post-gain interference signal according to the controller's instructions, so as to obtain the post-gain interference signal with the final output sensitivity. The controller is used to continuously adjust the wavelength of the light source signal within the adjustable wavelength range of the light source, so that the Fabry-Perot sensor outputs the interference curve of the Fabry-Perot sensor, calculates the current phase sensitivity of the Fabry-Perot sensor based on 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 current phase sensitivity of the Fabry-Perot sensor, and adjusts the gain of the high-pass continuously variable gain amplifier based on the current phase sensitivity of the Fabry-Perot sensor.

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

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

4. The operating method of the adaptive fiber optic Fabry-Perot sensor demodulation device according to any one of claims 1 to 3, characterized in that: Specifically, it includes: Step 1: The controller outputs the working wavelength of the current 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 the current interval according to the working wavelength of the current interval; Step 3: The Fabry-Perot sensor outputs the reflected light interference signal corresponding to the light source signal of the working wavelength of the current interval, based on the light source signal of the current interval. Step 4: The photodetector outputs an electrical signal based on the received reflected light interference signal; Step 5: The low-pass filter outputs a filtered signal based on the electrical signal and transmits it to the controller; Step 6: Repeat steps 1 to 5. The controller obtains the filtered signal sequence corresponding to all working wavelengths; obtains the electrical signal with the largest curve slope in the filtered signal sequence, calculates the working voltage corresponding to the electrical signal with the largest curve slope as the reference voltage value, and uses the maximum curve slope value as the phase sensitivity of the current 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, input the electrical signal into a high-pass fixed-gain amplifier, and obtain the gain-adjusted interference signal; Step 9: The controller calculates the gain ratio based on the current phase sensitivity of the Fabry-Perot sensor and the reference phase sensitivity, and transmits the gain ratio to the Qualcomm continuously variable gain amplifier. Step 10: The Qualcomm continuously variable gain amplifier outputs the post-gain interference signal with the final output sensitivity based on the post-gain interference signal 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 based on the gain ratio and the current phase sensitivity of the Fabry sensor, and calculating the displacement sensitivity of the Fabry sensor based on 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 slope of the curve is as follows: The filtered signal sequence of one period is discretized into M scan points, and the derivative value of each scan point is calculated. The expression for the derivative value is as follows: ； in, This represents the voltage change between two adjacent scan points. The phase interval between two adjacent scan points. The derivative value of the scan point; The maximum value of the derivative is taken as the maximum slope of the curve.

8. The working method according to claim 4, characterized in that: The expression for the gain ratio is as follows: ； in, This is the gain ratio. For reference phase sensitivity, This represents the phase sensitivity of the current Fabry-Perot sensor.

9. The working method according to claim 5, characterized in that: The expression for the final output sensitivity is as follows: ； in, For the final output sensitivity, The phase sensitivity of the current Fabry-Perot sensor, This represents the gain ratio.

10. The working method according to claim 5, characterized in that: The expression for the displacement sensitivity is as follows: ； in, For displacement sensitivity, For the final output sensitivity, The operating wavelength of a laser is a tunable wavelength light source. The refractive index of the medium inside the Fabry-Perot sensor cavity. Pi is the mathematical constant of a circle.

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