Demodulation method and system for improving sensitivity of interferometric sensor
By calculating the free spectral range of the interferometric sensor and the preset target magnification, two envelope intersection points are generated as feature tracking points, which solves the problems of complex structure and high cost of the interferometric sensor system and realizes an efficient and low-cost technical solution.
Patent Information
- Application Number
- CN202511024570.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-10-03
AI Technical Summary
Existing interferometric sensor systems have complex structures and high costs, making it difficult to match high-order harmonic vernier effects. In addition, existing technologies cannot effectively reduce demodulation costs and improve efficiency.
By calculating the free spectral range of the interferometric sensor and the preset target magnification, the intersection of two envelopes is generated as the feature tracking point. The sampling interval value is used for interval sampling and the measured parameters are demodulated, which simplifies the operation steps and reduces the equipment cost.
It achieves efficient and low-cost ultra-high sensitivity amplified measurement, simplifies the operation steps, reduces equipment costs, breaks through the matching problem of high-order harmonic vernier effect, and improves demodulation efficiency.
Smart Images
Figure CN120740647A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of sensor sensitivity demodulation, and in particular to a demodulation method and system for improving the sensitivity of an interferometric sensor. Background Art
[0002] The Vernier effect (VF) is a method for enhancing the measurement sensitivity of interferometric fiber optic sensors based on the interference mechanism. This effect is applicable to interferometer sensitivity enhancement: the spectra of two interferometers are superimposed (spectral terms are added or multiplied) to form a Vernier effect spectrum. The envelope of the Vernier effect spectrum has a sensitivity-amplifying effect compared to the original spectrum. Similar to a vernier caliper, the spectral periods of the two interferometers in a Vernier effect sensor are similar, but not identical. One interferometer provides only a reference spectrum, while the other provides a sensing spectrum. These interferometers are placed in the environment to be measured for sensing. Existing methods for stimulating the Vernier effect primarily utilize a combination of two physically fabricated interferometric sensors (these two interferometric sensors can be identical or different), such as Fabry-Pérot (FP), Mach-Zehnder (MZ), Sagnac, and various other interferometer combinations.
[0003] The need to combine two physical sensors often requires components such as fiber couplers and fiber circulators, resulting in a complex structure and high cost for existing vernier effect sensing systems. Furthermore, the matching process for existing vernier effect sensing systems is difficult and inefficient. The generation of a fiber vernier requires the spectral periods of the two interferometers, namely the FSR (Free Spectrum Range), to be close but equal. Taking a fiber optic FPI sensor as an example, the higher the vernier effect amplification factor, the closer the free spectral ranges of the SFPI (Sensing Fabry-Perot Interferometer) and the RFPI (Reference Fabry-Perot Interferometer) need to be, meaning the closer the effective optical path lengths of the SFPI and RFPI are. However, existing FPI preparation steps and processes, such as knife cutting, fiber extrusion welding, multiple fiber splicing, and high-power laser etching, introduce certain processing errors, causing the optical path matching between the SFPI and RFPI to deviate from the ideal state and the actual sensitivity amplification factor to deviate from the preset value. In recent years, some researchers have proposed replacing the conventional RFPI with a non-fixed structure. This structure typically consists of two single-mode optical fibers placed close together on a displacement platform to form an FPI cavity. The cavity length is typically controlled by a precision displacement platform, which adjusts the optical path length of the non-fixed RFPI to the desired amplification factor. However, this structure is relatively expensive. Furthermore, this approach is not suitable for matching high-order harmonic Vernier effects. Unlike the traditional Vernier effect, the high-order harmonic Vernier effect requires a significant difference in the optical path lengths of the SFPI and RFPI. The greater the difference, the higher the harmonic order of this Vernier effect, resulting in a higher harmonic order amplification sensitivity compared to the traditional Vernier effect. The RFPI cavity in the non-fixed scheme is an air cavity, which has high transmission losses and a maximum cavity length of approximately 350 μm. Above this length, the spectral contrast of the RFPI drops to a very low level, making it difficult to achieve high-order harmonic Vernier effect matching and ultra-high sensitivity amplified measurements. Summary of the Invention
[0004] The purpose of this application is to provide a demodulation method and system for improving the sensitivity of interferometric sensors, which can reduce demodulation costs, improve demodulation efficiency, achieve matching of high-order harmonic vernier effects, and realize ultra-high sensitivity amplified measurement.
[0005] To achieve the above objectives, this application provides the following solutions:
[0006] In a first aspect, the present application provides a demodulation method for improving the sensitivity of an interferometric sensor, the demodulation method for improving the sensitivity of an interferometric sensor specifically comprising the following steps:
[0007] Original spectral data of the interferometric sensor is acquired; the original spectral data includes a plurality of spectral data corresponding to a plurality of data points at a preset original wavelength sampling interval.
[0008] The free spectral range of the interferometric sensor is calculated based on the original spectral data.
[0009] The sampling interval value is calculated according to the free spectral range of the interference sensor and a preset target magnification.
[0010] According to the sampling interval value, each piece of spectral data in the original spectral data is sampled twice to generate a first envelope and a second envelope of the spectral data.
[0011] An intersection point between the first envelope and the second envelope of each piece of spectral data is taken as a characteristic tracking point, and a wavelength value of the characteristic tracking point is determined.
[0012] The wavelength shifts of all the characteristic tracking points are calculated according to the wavelength values of all the characteristic tracking points.
[0013] The parameter to be measured is demodulated according to the wavelength drift of all the characteristic tracking points.
[0014] Optionally, the free spectral range of the interferometric sensor is calculated using the following formula:
[0015] FSR = |λ2-λ1|;
[0016] Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
[0017] Optionally, the sampling interval value is calculated using the following formula:
[0018]
[0019] Where C is the sampling interval value, i is the set high-order harmonic vernier effect order, M is the target magnification, and FSR represents the free spectral range of the interferometric sensor.
[0020] Optionally, in the two interval samplings, the sequence number extracted during the first sampling is The first envelope is generated by fitting the data points; the second sampling is performed with the sequence number The second envelope is generated by fitting the data points; where C is the sampling interval value, x is the original wavelength sampling interval, i is the set order of the high-order harmonic vernier effect, δ is the offset, a=0, 1, 2……, b=0, 1, 2…….
[0021] Optionally, the offset δ satisfies:
[0022]
[0023] Where δ is the offset, C is the sampling interval value, and x is the original wavelength sampling interval.
[0024] Optionally, the interferometric sensor is a Mach-Zehnder interferometer, a Michelson interferometer, a Sagnac interferometer or a Fabry-Perot interferometer.
[0025] In a second aspect, the present application proposes a demodulation system for improving the sensitivity of an interferometric sensor, wherein the demodulation system for improving the sensitivity of an interferometric sensor includes a broadband light source, a circulator, an interferometric sensor, a spectrometer, and a data processing module.
[0026] The input end of the circulator is connected to the output end of the broadband light source, the output end of the circulator is connected to the input end of the interferometric sensor, the echo end of the circulator is connected to the input end of the spectrometer, and the output end of the spectrometer is connected to the data processing module.
[0027] The broadband light source is used to emit detection light to the circulator.
[0028] The circulator is used to realize unidirectional isolated transmission of the optical path.
[0029] The interference sensor is used to receive the detection light and generate an interference spectrum.
[0030] The spectrometer is used to perform discrete sampling on the interference spectrum to obtain original spectrum data; the original spectrum data includes multiple spectrum data corresponding to multiple data points of a preset original wavelength sampling interval.
[0031] The data processing module is used to calculate the free spectral range of the interferometric sensor based on the original spectral data; calculate the sampling interval value based on the free spectral range of the interferometric sensor and the preset target magnification; perform two interval samplings on each spectral data in the original spectral data according to the sampling interval value to generate the first envelope and the second envelope of the spectral data; take the intersection of the first envelope and the second envelope of each spectral data as a feature tracking point, and determine the wavelength value of the feature tracking point; calculate the wavelength drift of all the feature tracking points based on the wavelength values of all the feature tracking points; and demodulate the measured parameter based on the wavelength drift of all the feature tracking points.
[0032] Optionally, the data processing module calculates the free spectral range of the interferometric sensor using the following formula:
[0033] FSR = |λ2-λ1|;
[0034] Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
[0035] Optionally, the data processing module calculates the sampling interval value using the following formula:
[0036]
[0037] Where C is the sampling interval, i is the set high-order harmonic vernier effect order, and M is the target magnification.
[0038] Optionally, the data processing module extracts the sequence number of the first sampling in the two interval samplings. The first envelope is generated by fitting the data points; the second sampling is performed with the sequence number The second envelope is generated by fitting the data points; where C is the sampling interval value, x is the original wavelength sampling interval, i is the set order of the high-order harmonic vernier effect, δ is the offset, a=0, 1, 2……, b=0, 1, 2…….
[0039] According to the specific embodiments provided in this application, this application has the following technical effects:
[0040] The present application provides a demodulation method and system for improving the sensitivity of an interferometric sensor. The method calculates the free spectral range of the interferometric sensor based on the original spectral data, and calculates a sampling interval value based on the free spectral range of the interferometric sensor and a preset target magnification factor. Two interval samples are then taken according to the sampling interval value to generate two envelopes. The intersection of the two envelopes is used as a characteristic tracking point, and its wavelength value is determined. The wavelength drift is calculated, and then the wavelength drift of all characteristic tracking points can be used to conveniently and efficiently demodulate and obtain the measured parameter. By calculating the sampling interval value and performing two interval samples, the present application only needs to perform interval sampling operations on the spectrum of a single interferometric sensor, and can also achieve the high-sensitivity amplification of the high-order Vernier effect, achieve matching of the ultra-high-magnification high-order harmonic Vernier effect, effectively reduce the equipment cost of the Vernier effect sensor, and simplify the operation steps. Compared with traditional Vernier effect sensors, this application only needs to obtain the original spectral data of the interferometric sensor and perform data processing processes such as sampling interval value calculation, two-interval sampling and envelope generation analysis to achieve low-cost, efficient and simple sensitivity demodulation and ultra-high sensitivity amplified measurement without borrowing other physical reference cavities and corresponding connecting optical devices and optical paths, thereby effectively saving demodulation costs, eliminating the step of preparing a physical reference cavity, and improving demodulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0042] Figure 1 A flowchart of a demodulation method for improving the sensitivity of an interferometric sensor provided in one embodiment of the present application is provided.
[0043] Figure 2 This is a connection diagram of a sensor demodulation device provided in one embodiment of the present application.
[0044] Figure 3 Schematic diagram of an FPI temperature sensor provided in one embodiment of the present application.
[0045] Figure 4 This is a diagram of the actual dimensions of the temperature sensor provided in one embodiment of the present application.
[0046] Figure 5 This is an original sampling spectrum provided in an embodiment of the present application.
[0047] Figure 6A schematic diagram of the interval sampling demodulation process provided in one embodiment of the present application.
[0048] Figure 7 A schematic diagram of two envelopes and their characteristic tracking points obtained by interval sampling of spectrum P1 provided in one embodiment of the present application.
[0049] Figure 8 A schematic diagram of temperature drift of an interval sampling spectrum provided in an embodiment of the present application.
[0050] Figure 9 A schematic diagram of temperature sensitivity corresponding to temperature drift of the interval sampling spectrum provided in one embodiment of the present application.
[0051] Figure 10 A schematic diagram of the temperature drift of the original spectrum provided in an embodiment of the present application.
[0052] Figure 11 A schematic diagram of temperature sensitivity corresponding to the temperature drift of the original spectrum provided in an embodiment of the present application. DETAILED DESCRIPTION
[0053] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.
[0054] Explanation of terms:
[0055] Interferometric Fiber Optic Sensor (IFOS): An interferometric sensor that uses multiple beams of light in an optical fiber to generate multiple levels of interference fringes for measurement. Based on the type of interference, it can be mainly divided into: Mach-Zehnder Interferometer (MZI), Michelson Interferometer, Sagnac Interferometer, Fabry-Pérot Interferometer (FPI), etc.
[0056] Fabry-Perot interferometer: An optical interference structure consisting of two parallel glass plates, which can be used for filtering, sensing, etc.
[0057] Traditional Vernier Effect (TVF): The Vernier Effect is a method for enhancing the sensitivity of interferometric sensors based on the interference mechanism. This effect is suitable for interferometer sensitivity enhancement: the spectra of two interferometers are superimposed (spectral terms are added or multiplied) to form a Vernier Effect spectrum. The envelope of the Vernier Effect spectrum has a sensitivity amplification effect compared to the original spectrum, which is the Vernier Effect. The combination of two interferometric structures with similar interference frequencies produces a spectrum with a least common multiple period, which can effectively improve sensitivity.
[0058] High-order harmonic Vernier effect (HVF): Different from the traditional Vernier effect, the high-order harmonic Vernier effect requires that the interference frequencies of the two interference structures are in a multiple relationship, that is, the difference in interference frequencies is relatively large, which can also achieve the effect of sensitivity amplification.
[0059] Sensing FPI (SFPI): The FPI used for the sensing part of a Vernier effect sensor, which is sensitive to the parameter to be measured.
[0060] Reference FPI (RFPI): The FPI used to provide a stable reference spectrum portion in a vernier effect sensor. It is insensitive to the measured parameter or is placed in an environment other than the one being measured.
[0061] FSR (Free Spectrum Range): Free spectrum range, which can also represent the period of periodic spectrum.
[0062] Effective optical path length: Refractive index multiplied by physical length.
[0063] Cross-sensitivity: The sensor is sensitive to multiple parameters at the same time. During the measurement process, multiple parameters act together, making it difficult to distinguish the effects of the parameters.
[0064] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0065] like Figure 1 As shown, this embodiment proposes a demodulation method for improving the sensitivity of an interferometric sensor. This demodulation method for improving the sensitivity of an interferometric sensor is mainly used in the interferometric sensor sensitivity demodulation scenario. By demodulating the sensitivity of the interferometric sensor to determine the parameter to be measured, it is beneficial to complete the sensitivity evaluation, calibration, and sensitivity enhancement of the interferometric sensor. The demodulation method for improving the sensitivity of an interferometric sensor specifically includes the following steps:
[0066] S1: Obtain the raw spectral data of the interferometric sensor.
[0067] In this embodiment, the interferometric sensor is a Mach-Zehnder interferometer, a Michelson interferometer, a Sagnac interferometer, or a Fabry-Perot interferometer. The original spectral data includes a plurality of spectral data corresponding to a plurality of data points at a preset original wavelength sampling interval.
[0068] S2: Calculating the free spectral range of the interferometric sensor according to the original spectral data.
[0069] In this embodiment, the free spectral range of the interferometric sensor is calculated using the following formula:
[0070] FSR=|λ2-λ1| (1).
[0071] Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
[0072] S3: Calculating a sampling interval value according to the free spectral range of the interferometric sensor and a preset target magnification.
[0073] In this embodiment, the sampling interval value is calculated using the following formula:
[0074]
[0075] Where C is the sampling interval value, i is the set high-order harmonic vernier effect order, M is the target magnification, and FSR represents the free spectral range of the interferometric sensor.
[0076] S4: performing two interval samplings on each piece of spectral data in the original spectral data according to the sampling interval value, to generate a first envelope and a second envelope of the spectral data.
[0077] The two interval samplings in this embodiment are specifically as follows:
[0078] When sampling for the first time, the extraction sequence number is The first envelope is generated by fitting the data points.
[0079] When sampling for the second time, the extraction number is The second envelope is generated by fitting the data points.
[0080] Wherein, C is the sampling interval value, x is the original wavelength sampling interval, i is the set high-order harmonic vernier effect order, δ is the offset, a=0, 1, 2..., b=0, 1, 2...
[0081] In this embodiment, the offset δ satisfies the following formula to ensure that the first envelope and the second envelope form an intersection within the spectrum range:
[0082]
[0083] Where δ is the offset, C is the sampling interval value, and x is the original wavelength sampling interval.
[0084] S5: Taking the intersection of the first envelope and the second envelope of each piece of spectral data as a characteristic tracking point, and determining the wavelength value of the characteristic tracking point.
[0085] S6: Calculating the wavelength drift of all the feature tracking points according to the wavelength values of all the feature tracking points.
[0086] S7: Demodulate the parameter to be measured according to the wavelength drift of all the characteristic tracking points.
[0087] Based on the same inventive concept, embodiments of the present application also provide a demodulation system for implementing the aforementioned demodulation method for improving interferometric sensor sensitivity. The solution provided by this demodulation system for improving interferometric sensor sensitivity is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more embodiments of the demodulation system for improving interferometric sensor sensitivity provided below can be found in the aforementioned limitations of the demodulation method for improving interferometric sensor sensitivity, and will not be further elaborated here.
[0088] In an exemplary embodiment, a demodulation system for improving the sensitivity of an interferometric sensor is provided. The system adds a data processing module to a traditional demodulation device. Figure 2 As shown, the system includes a broadband light source, a circulator, an interferometric sensor, a spectrometer and a data processing module.
[0089] The input end of the circulator is connected to the output end of the broadband light source, the output end of the circulator is connected to the input end of the interferometric sensor, the echo end of the circulator is connected to the input end of the spectrometer, and the output end of the spectrometer is connected to the data processing module.
[0090] The broadband light source is used to emit detection light to the circulator.
[0091] The circulator is used to realize unidirectional isolated transmission of the optical path.
[0092] The interference sensor is used to receive the detection light and generate an interference spectrum.
[0093] The spectrometer is used to perform discrete sampling on the interference spectrum to obtain original spectrum data; the original spectrum data includes multiple spectrum data corresponding to multiple data points of a preset original wavelength sampling interval.
[0094] The data processing module is used to calculate the free spectral range of the interferometric sensor based on the original spectral data; calculate the sampling interval value based on the free spectral range of the interferometric sensor and the preset target magnification; perform two interval samplings on each spectral data in the original spectral data according to the sampling interval value to generate the first envelope and the second envelope of the spectral data; take the intersection of the first envelope and the second envelope of each spectral data as a feature tracking point, and determine the wavelength value of the feature tracking point; calculate the wavelength drift of all the feature tracking points based on the wavelength values of all the feature tracking points; and demodulate the measured parameter based on the wavelength drift of all the feature tracking points.
[0095] In this embodiment, the data processing module calculates the free spectral range of the interferometric sensor using the following formula:
[0096] FSR=|λ2-λ1| (4).
[0097] Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
[0098] In this embodiment, the data processing module calculates the sampling interval value using the following formula:
[0099]
[0100] Where C is the sampling interval, i is the set high-order harmonic vernier effect order, and M is the target magnification.
[0101] In this embodiment, the data processing module extracts the sequence number of the first sampling in the two interval samplings. The first envelope is generated by fitting the data points; the second sampling is performed with the sequence number The second envelope is generated by fitting the data points; where C is the sampling interval value, x is the original wavelength sampling interval, i is the set order of the high-order harmonic vernier effect, δ is the offset, a=0, 1, 2……, b=0, 1, 2…….
[0102] In order to make the technical solution of the present application clearer, the implementation process and system structure of the technical solution of the present application are described in detail below in the form of examples.
[0103] In this embodiment, the optical fiber sensor is an interferometric optical fiber sensor, which includes a Mach-Zehnder interferometer, a Michelson interferometer, a Sagnac interferometer, or a Fabry-Perot interferometer. A Fabry-Perot (FPI) temperature sensor is used as an example for illustration. The structure of the FPI temperature sensor is as follows: Figure 3 The actual size and dimensions of the FPI temperature sensor are shown in Figure 4 As shown. Figure 3 As shown, the optical fiber at the end of the optical fiber ceramic ferrule and the right end face of PDMS form an FP interference cavity, M1 is the reflection surface formed by the ceramic ferrule and PDMS, and M2 is the reflection surface formed by PDMS and air. r It can be expressed by the following formula:
[0104]
[0105] Among them, E in is the light intensity incident on the sensor, E r is the reflected light intensity, the reflectivities of M1 and M2 are denoted as R1 and R2 respectively, α1 is the transmission loss, and φ is the phase change of the single-pass light beam after passing through the FP cavity, which can be expressed as φ = 2πnL / λ, where L and n are the length and refractive index of the FP cavity respectively, and λ is the wavelength of light.
[0106] The reflectance spectrum of the sensor is a periodic function, and the free spectral range (FSR) of the spectrum can be expressed as:
[0107]
[0108] Where FSR represents the free spectral range of the spectrum, L and n are the length and refractive index of the FP cavity, respectively, and λ is the wavelength of light.
[0109] In this embodiment, the original wavelength sampling interval of the spectrometer is 0.02 nm.
[0110] In this embodiment, the process of generating high-order harmonic Vernier effect by interval sampling is as follows: Figure 6 As shown. It mainly includes the following steps:
[0111] Step (1): Collect the original spectrum data P. The original wavelength sampling interval of the spectrometer is x (unit: nm) 0.02nm. The number of data points of the complete spectrum within the wavelength range of the sampling interval X (1300-1630nm in this embodiment) is The first set of spectra is denoted as P1, and the nth set of spectra is denoted as Pn.
[0112] Step (2): Calculate the free spectral range (FSR) of the sensor. Figure 5The FSR of the spectrum in is 12.40 nm.
[0113] Step (3): Determine the sampling interval value C. In this embodiment, i=5 is set, and the preset target magnification is M=12. According to (2), C=2.04 nm can be calculated.
[0114] Step (4): Resample the spectrum P1 according to the sampling interval value C to obtain the first envelope E of the spectrum P1 11 . Resample to get the spectrum P1 (where a is 0, 1, 2, ..., a natural number) data points, these data points are fitted to obtain the first envelope E 11 , where the first number in the subscript corresponds to the original spectrum P1, and the second number in the subscript represents the first envelope E 11 .
[0115] In this embodiment, C = 2.04nm, x = 0.02nm. Therefore, this embodiment samples the 1st, 511th, 1021th, ... 1+102×a×5th data and fits to obtain the first envelope, as shown in Figure 7 shown.
[0116] Step (5): Resample the spectrum P1 according to the sampling interval C to obtain the second envelope E of the spectrum P1 12 Here, the sampling starting point is changed, and the spectrum sampling starting point is The data point is the first (where a is 0, 1, 2, ..., a natural number) data points are sampled and these points are fitted to obtain the second envelope E 12 . The additional items For experience value, ensure E 11 、E 12 The two envelopes can form an intersection within the total spectral wavelength range, such as Figure 7 shown.
[0117] In this embodiment, for the 307th, 817th, ..., The data are sampled and fitted to obtain the second envelope E 12 .
[0118] Step (6): Find the intersection of the two fitted envelopes and record it as the feature tracking point S1. Read the wavelength value of the feature tracking point S1 and record it as λ S1 .like Figure 7 As shown, in this embodiment, two envelopes and feature point tracking S1 are obtained.
[0119] Step (7): Repeat the above steps (4) to (6) for the remaining spectra Pn, and obtain two envelopes E for each spectrum. n1 、E n2 And its characteristic tracking point Sn, read the wavelength value λ of the characteristic tracking point Sn Sn .
[0120] Step (8): Demodulate the actual physical quantity according to the wavelength drift of all characteristic tracking points.
[0121] In this embodiment, the wavelength value λ of the characteristic tracking point S1 is S1 As a benchmark, calculate all other λ Sn and λ S1 The wavelength shift Δλ can be obtained by calculating the wavelength arithmetic difference Sn . By the corresponding wavelength drift Δλ Sn The phenotypic relationship of the relevant parameters is used to demodulate the parameters to be measured to obtain a demodulation result.
[0122] In this embodiment, temperature is taken as an example, that is, the parameter to be measured is temperature. Figure 8 The schematic diagram of the temperature drift of the interval sampling spectrum shows that the intersection of the inner envelope has a large range of blue shift (blue shift is also called blue displacement, which refers to the phenomenon that the entire spectrum or a characteristic point in the spectrometer drifts toward the short wavelength direction). The temperature sensitivity reaches 18.42nm / ℃ by tracking the intersection of each group of inner envelopes for temperature calibration, with good linearity and R 2 =0.999, such as Figure 9 shown. Figure 10 is the temperature sensitivity of the original spectrum, and the temperature test results are as follows Figure 11 As shown. It can be seen that as the temperature increases, the spectrum as a whole red shifts. The spectrum peak near the wavelength of 1510nm is selected for tracking. The measurement results are as follows Figure 11 As shown, the sensor's temperature sensitivity is 0.298 nm / °C, which is also the base sensitivity of a single FPI. It can be seen that compared to the original peak tracking and interval sampling demodulation method, the sensitivity is increased by approximately 62 times, which is consistent with the 60x sensitivity magnification preset in this embodiment.
[0123] This embodiment achieves the high-sensitivity amplification of the high-order Vernier effect by simply sampling the spectrum of a single interferometric sensor at intervals. This method effectively reduces the equipment cost of Vernier effect sensors while simplifying the operational steps. The required demodulation device is identical to that of a single interferometric sensor, yet achieves the same Vernier effect sensitivity amplification. Compared to traditional Vernier effect sensors, this application eliminates the need for a physical reference cavity and its corresponding connecting optical components and optical path, significantly reducing costs and eliminating the need to prepare a physical reference cavity.
[0124] The design of the sampling interval value C involved in this embodiment is key to determining the sensitivity magnification in this demodulation method. It can effectively reduce the difficulty of Vernier effect optical path matching, has a high success rate, and accurately controls the magnification. To achieve the ideal magnification, the traditional Vernier effect requires the spectral FSRs of two interferometric sensors to be controlled to be close, which is difficult to achieve through fabrication methods, resulting in a complex preparation process and a low success rate. However, the method of the present application can control the magnification by controlling the sampling interval value C, which is simple to operate, has a high success rate, and accurately controls the magnification.
[0125] This embodiment can achieve the matching of ultra-high-magnification high-order harmonic Vernier effect. The realization of the high-order harmonic Vernier effect requires that the FSR of the reference spectrum is very small, which requires that the effective optical path of the interferometric sensor is very long, thereby reducing the contrast of the reference spectrum, and it is difficult to fit an envelope suitable for demodulation in the superimposed spectrum. Since the method of the present application adopts the method of interval sampling and fitting to manufacture the envelope, there is no need to introduce a physical interferometric sensor, and the amplification effect of the high-order harmonic Vernier effect can also be achieved. Therefore, the present application can break through the limitation of the contrast of the physical reference spectrum and achieve the matching of ultra-high-magnification high-order harmonic Vernier effect.
[0126] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0127] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.
Claims
1. A demodulation method for improving the sensitivity of an interferometric sensor, characterized in that: The demodulation method for improving the sensitivity of the interferometric sensor includes: Acquire original spectral data of the interferometric sensor; the original spectral data includes a plurality of spectral data corresponding to a plurality of data points of a preset original wavelength sampling interval; Calculating the free spectral range of the interferometric sensor based on the original spectral data; Calculating a sampling interval value according to the free spectral range of the interferometric sensor and a preset target magnification; According to the sampling interval value, each piece of spectral data in the original spectral data is sampled twice to generate a first envelope and a second envelope of the spectral data; Taking the intersection of the first envelope and the second envelope of each piece of the spectral data as a characteristic tracking point, and determining the wavelength value of the characteristic tracking point; Calculating wavelength shifts of all the characteristic tracking points based on the wavelength values of all the characteristic tracking points; The parameter to be measured is demodulated according to the wavelength drift of all the characteristic tracking points.
2. The demodulation method for improving the sensitivity of an interferometric sensor according to claim 1, wherein: The free spectral range of the interferometric sensor is calculated using the following formula: FSR = |λ2-λ1|; Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
3. The demodulation method for improving the sensitivity of an interferometric sensor according to claim 1, wherein: The sampling interval value is calculated using the following formula: Where C is the sampling interval value, i is the set high-order harmonic vernier effect order, M is the target magnification, and FSR represents the free spectral range of the interferometric sensor.
4. The demodulation method for improving the sensitivity of an interferometric sensor according to claim 1, wherein: In the two interval samplings, the extraction sequence number for the first sampling is The first envelope is generated by fitting the data points; the second sampling is performed with the sequence number The second envelope is generated by fitting the data points; where C is the sampling interval value, x is the original wavelength sampling interval, i is the set order of the high-order harmonic vernier effect, δ is the offset, a=0, 1, 2……, b=0, 1, 2…….
5. The demodulation method for improving the sensitivity of an interferometric sensor according to claim 4, characterized in that: The offset δ satisfies: Where δ is the offset, C is the sampling interval value, and x is the original wavelength sampling interval.
6. The demodulation method for improving the sensitivity of an interferometric sensor according to claim 1, wherein: The interferometric sensor is a Mach-Zehnder interferometer, a Michelson interferometer, a Sagnac interferometer or a Fabry-Perot interferometer.
7. A demodulation system for improving the sensitivity of an interferometric sensor, characterized in that: The demodulation system for improving the sensitivity of the interferometric sensor includes a broadband light source, a circulator, an interferometric sensor, a spectrometer and a data processing module; The input end of the circulator is connected to the output end of the broadband light source, the output end of the circulator is connected to the input end of the interferometric sensor, the echo end of the circulator is connected to the input end of the spectrometer, and the output end of the spectrometer is connected to the data processing module; The broadband light source is used to emit detection light to the circulator; The circulator is used to realize unidirectional isolated transmission of the optical path; The interference sensor is used to receive the detection light and generate an interference spectrum; The spectrometer is used to discretize the interference spectrum and obtain original spectrum data; The original spectrum data includes a plurality of spectrum data corresponding to a plurality of data points of a preset original wavelength sampling interval; The data processing module is used to calculate the free spectral range of the interferometric sensor based on the original spectral data; calculate the sampling interval value based on the free spectral range of the interferometric sensor and the preset target magnification; perform two interval samplings on each spectral data in the original spectral data according to the sampling interval value to generate the first envelope and the second envelope of the spectral data; take the intersection of the first envelope and the second envelope of each spectral data as a feature tracking point, and determine the wavelength value of the feature tracking point; calculate the wavelength drift of all the feature tracking points based on the wavelength values of all the feature tracking points; and demodulate the measured parameter based on the wavelength drift of all the feature tracking points.
8. The demodulation system for improving the sensitivity of an interferometric sensor according to claim 7, wherein: The data processing module calculates the free spectral range of the interferometric sensor using the following formula: FSR = |λ2-λ1|; Wherein, λ1 and λ2 are the wavelengths of the two valleys of the interferometric sensor spectrum near 1550 nm, and FSR represents the free spectral range of the interferometric sensor.
9. The demodulation system for improving the sensitivity of an interferometric sensor according to claim 7, wherein: The data processing module calculates the sampling interval value using the following formula: Where C is the sampling interval value, i is the set high-order harmonic vernier effect order, M is the target magnification, and FSR represents the free spectral range of the interferometric sensor.
10. The demodulation system for improving the sensitivity of an interferometric sensor according to claim 7, wherein: The data processing module extracts the sequence number when sampling for the first time during the two interval samplings. The first envelope is generated by fitting the data points; the second sampling is performed with the sequence number The second envelope is generated by fitting the data points; where C is the sampling interval value, x is the original wavelength sampling interval, i is the set order of the high-order harmonic vernier effect, δ is the offset, a=0, 1, 2……, b=0, 1, 2…….