Interferometer sensing measurement method based on special reference spectrum vernier effect

Abstract

The invention relates to an interferometer sensing measurement method based on a special reference spectrum vernier effect, which comprises the following steps: S101, according to a spectrum measurement range and an interferometer cavity length change range caused by a measured physical quantity, establishing a relational expression that a free spectral range (FSR) of a virtual reference interferometer spectrum changes along with wavelength; s102, obtaining a spectral curve of the reference interferometer; s103, superposing the actually measured spectrum curve of the sensing interferometer and the spectrum curve of the reference interferometer, and obtaining a total spectrum curve of which the envelope appears the characteristic wavelength based on a vernier effect; and S104, monitoring the change of the characteristic wavelength along with the measured physical quantity, and completing the measurement according to the calibrated relationship between the characteristic wavelength and the measured physical quantity. According to the invention, only one optical interferometer is needed, a special reference spectrum is constructed according to the measured physical quantity and the measurement range of the spectrum, and the unique recognizable characteristic wavelength can be obtained based on the vernier effect, so that the ambiguity resolution and high-sensitivity measurement of the physical quantity are realized.

Description

Technical Field

[0001] This invention relates to the field of optical signal processing, and in particular to an interferometer sensing and measurement method based on a special reference spectrum vernier effect. Background Technology

[0002] Fiber optic sensors based on conventional interferometer principles (Fabry-Perot interferometer (FPI), Michelson interferometer (MI), and Mach-Zehnder interferometer (MZI), etc.) generally exhibit periodic comb-like filtering characteristics in their interference spectra under two-beam or multi-beam interference mechanisms. These sensors will show periodic interference peaks / valleys with similar appearances within their operating wavelength range. In large-scale measurement scenarios, when the wavelength shift of the monitored peak or valley exceeds one period, wavelength identification can easily become difficult.

[0003] To address the difficulty of tracking peak / valley wavelengths in interferometer spectra, previous studies have proposed various solutions. For example, in our early work, we proposed a special mode interferometer with a unique and identifiable characteristic wavelength (CWL) in its interference spectrum. Its core principle is to use specially designed fiber parameters to make the group velocities of the two transmitted interference modes equal or the group optical path difference zero at a specific wavelength, forming a unique and identifiable characteristic wavelength in the envelope of the transmission spectrum, which is convenient for monitoring and continuous wavelength tracking. However, this scheme requires specially designed fiber parameters to present CWL in the transmission spectrum, which limits its practical application (C. Lu, J. Su, X. Dong*, T. Sun, and KTVGrattan, “Simultaneous Measurement of Strain and Temperature with a Few-ModeFibre-based Sensor” [J], Journal of Lightwave Technology, vol. 36, no. 13,pp. 2796-2802, Jul. 1,2018.). Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and propose an interferometer sensing measurement method based on the vernier effect of a special reference spectrum. A special reference spectrum is determined within the spectral measurement range of the optical interferometer and superimposed on the output spectrum of the optical interferometer. Based on the vernier effect, a uniquely identifiable interference peak / valley point appears in the upper envelope of the superimposed spectrum. By monitoring the change of the wavelength corresponding to the interference peak / valley point in the envelope with the measured physical quantity, highly sensitive and ambiguity-resistant interferometric measurement of the measured physical quantity is achieved under large-scale variations.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An interferometer sensing measurement method based on a special reference spectral vernier effect includes:

[0007] S101, based on the spectral measurement range and the range of interferometer cavity length variation caused by the measured physical quantity, establish the relationship between the free spectral range of the virtual reference interferometer and the wavelength, as follows:

[0008] Based on the cavity length of the optical interferometer and the effective refractive index of the cavity medium, a first relationship is established between the free spectral range within the spectral measurement range and the wavelengths corresponding to the interference peaks / valleys.

[0009] Based on the first relationship, the minimum cavity length L is calculated respectively. min and the shortest wavelength λ for arbitrarily monitoring interference peaks / valleys min The corresponding first free spectral range FSR1 under the condition, and at the maximum cavity length L max and the longest wavelength λ for arbitrarily monitoring interference peaks / valleys max The corresponding second free spectral range FSR2 under the given conditions;

[0010] With (λ) min (FSR1) and (λ) max Using FSR2 as the coordinate point, a second relationship describing the change of the free spectral range with wavelength in a special reference spectrum is obtained by fitting, which serves as the relationship of the free spectral range with wavelength of a virtual reference interferometer.

[0011] S102, based on the relationship between the free spectral range of the virtual reference interferometer and the wavelength, a special reference spectral intensity distribution is constructed;

[0012] S103, superimpose the measured spectral intensity of the optical interferometer with the spectral intensity of a special reference to obtain the superimposed total spectral intensity, and extract the spectral intensity of the upper envelope of the superimposed total spectral intensity;

[0013] S104, acquire and monitor the change of characteristic wavelength with the measured physical quantity, and complete the measurement by means of the calibrated characteristic wavelength and the measured physical quantity, as follows:

[0014] Based on the vernier effect, a unique wavelength point with a significant intensity change is obtained on the spectral intensity of the upper envelope, and the wavelength of this wavelength point is taken as the characteristic wavelength.

[0015] Real-time monitoring of changes in the characteristic wavelength enables the measurement of physical quantities that correspond to the cavity length and effective refractive index.

[0016] Preferably, the first relation is expressed as follows:

[0017] ;

[0018] in, The free spectral range is represented within the spectral measurement range; λ1 and λ2 represent the wavelengths corresponding to two adjacent interference peaks / valleys, respectively; L S represents the cavity length of the optical interferometer; n represents the effective refractive index of the cavity medium.

[0019] Preferably, the second relation is expressed as follows:

[0020] ;

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] in, This indicates the free spectral range within a specific reference spectrum.

[0026] Preferably, the specific reference spectral intensity is represented as follows:

[0027] ;

[0028] in, Indicates the intensity of a specific reference spectrum.

[0029] Preferably, the total superimposed spectral intensity is expressed as follows:

[0030] ;

[0031] in, Indicates the total superimposed spectral intensity; This represents the measured intensity of the sensor spectrum.

[0032] Preferably, the spectral intensity of the upper envelope is expressed as follows:

[0033] ;

[0034] in, This represents the spectral intensity of the upper envelope.

[0035] Preferably, based on the spectral intensity of the upper envelope, the wavelength of a unique wavelength point with a significant intensity change is obtained as the characteristic wavelength, including:

[0036] Retrieve from the first relation With the free spectral range in the second relation When they are equal, the wavelength of the wavelength point appearing in the spectral intensity of the upper envelope is taken as the characteristic wavelength, as follows:

[0037] ;

[0038] in, Indicates the characteristic wavelength.

[0039] Preferably, based on the spectral intensity of the upper envelope, the wavelength of a unique wavelength point with a significant intensity change is obtained as the characteristic wavelength, including:

[0040] On the spectral intensity of the upper envelope, identify the wavelength point that satisfies the spectral intensity of both upper envelopes with the largest free spectral range and the free spectral range of both upper envelopes decreases away from the upper envelopes, and take the wavelength of the wavelength point as the characteristic wavelength.

[0041] The spectral intensity of the upper envelope is mirror-symmetric about the characteristic wavelength; within the spectral intensity of the upper envelope, the wavelengths λ corresponding to the first interference peak / valley on either side of the characteristic wavelength are identified. E1 and λ E2 The characteristic wavelength is represented as follows:

[0042] ;

[0043] in, Indicates the characteristic wavelength.

[0044] Preferably, after measuring the physical quantity that corresponds to the cavity length and effective refractive index, the method further includes: measuring the sensitivity when the change in the physical quantity causes a change in the wavelength of the characteristic wavelength, expressed as follows:

[0045] ;

[0046] in, The sensitivity that indicates the change in wavelength of a characteristic wavelength caused by a change in a physical quantity; The sensitivity amplification factor representing the vernier effect; This indicates the wavelength sensitivity of the optical interferometer. It represents the physical quantity that is measured.

[0047] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention can solve the problem of wavelength identification of periodic spectrum in large-scale measurement: by constructing a special reference spectrum that satisfies a specific mathematical relationship and superimposing it with the sensing spectrum output by the optical interferometer, the characteristic wavelength with unique identification formed on the upper envelope of the superimposed total spectrum can be obtained, thereby establishing a one-to-one correspondence between the input physical quantity and the change in characteristic wavelength, effectively solving the problem of wavelength identification difficulty of periodic spectrum in large-scale measurement.

[0049] (2) The present invention can enhance measurement sensitivity: by means of the vernier effect mechanism, the measurement sensitivity is enhanced;

[0050] (3) The present invention has wide applicability: it is applicable to various optical interferometers, does not require special optical fiber structure, and can extract characteristic wavelengths and complete measurement functions through digital signal post-processing, and can flexibly adapt to different measurement scenarios. Attached Figure Description

[0051] Figure 1 This is a flowchart of an interferometer sensing measurement method based on a special reference spectrum vernier effect according to an embodiment of the present invention;

[0052] Figure 2 The FSR of the optical interferometer in this embodiment of the invention with cavity lengths of 300 μm and 340 μm are shown. S FSR of the -λ1 curve and special reference spectrum R -λ1 curve simulation diagram;

[0053] Figure 3 The above is a simulation diagram of the intensity of the sensing spectrum and the special reference spectrum in an embodiment of the present invention.

[0054] Figure 4 This is a simulation diagram of the total spectral intensity of the superimposed sensor spectrum and special reference spectrum in an embodiment of the present invention. Detailed Implementation

[0055] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0056] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0057] The interferometer sensing measurement method based on the vernier effect of a special reference spectrum proposed in the embodiment uses an optical interferometer and a digital virtual special reference spectrum. The optical interferometer can be a conventional interferometer such as a Michelson interferometer (MI), a Mach-Zehnder interferometer (MZI), or a Fabry-Perot interferometer (FPI).

[0058] like Figure 1 As shown in the figure, this embodiment presents an interferometer sensing measurement method based on the special reference spectrum vernier effect, which includes the following steps.

[0059] S101. Based on the spectral measurement range and the range of interferometer cavity length variation caused by the measured physical quantity, establish the relationship between the free spectral range of the virtual reference interferometer and the wavelength.

[0060] S1011, based on the cavity length of the optical interferometer and the effective refractive index of the cavity medium, establishes the first relationship between the free spectral range within the spectral measurement range and the wavelengths corresponding to the interference peaks / valleys.

[0061] Specifically, the free spectral range (FSR) of an interferometer is defined as the wavelength interval between adjacent interference peaks or valleys within the spectral measurement range. Let λ1 and λ2 represent the wavelengths corresponding to two adjacent interference peaks or valleys, respectively. The first equation for the free spectral range (FSR) within the spectral measurement range of an optical interferometer is as follows: ;

[0062] Among them, L S represents the cavity length of the optical interferometer; n represents the effective refractive index of the cavity medium.

[0063] In addition, the optical path length of the optical interferometer As shown below:

[0064] ;

[0065] Where m represents the interference order.

[0066] S1012, Based on the first relationship, calculate the minimum cavity length L respectively.min and the shortest wavelength λ for arbitrarily monitoring interference peaks / valleys min The corresponding first free spectral range FSR1 under the condition, and at the maximum cavity length L max and the longest wavelength λ for arbitrarily monitoring interference peaks / valleys max The corresponding second free spectral range FSR2 under the given conditions.

[0067] Specifically, the dynamic variation range of the cavity length of the optical interferometer is set to L. min To L max , will L min and L max Substituting into formula (1) yields the FSR of both. S - curve.

[0068] Utilizing the FSR of both S - The curve yields a cavity length of L. min Below, with a wavelength of λ min The corresponding FSR value is The cavity length is L. max Below, with a wavelength of λ max The corresponding FSR value is . and They are represented as follows:

[0069] ;

[0070] .

[0071] S1013, with (λ) min (FSR1) and (λ) max Using FSR2 as the coordinate point, a second relationship is obtained by fitting to describe the change of the free spectral range with wavelength in a special reference spectrum, which serves as the relationship of the free spectral range with wavelength for a virtual reference interferometer.

[0072] Specifically, the obtained data forms two coordinate points (λ). min (FSR1) and (λ) max FSR2), by using two coordinate points to construct a linear function expression, the FSR of the special reference spectrum can be obtained. R The expression for the -λ1 curve, and its calculation formula, is as follows:

[0073] ;

[0074] Let k1 and k2 be represented as:

[0075] ;

[0076] ;

[0077] Then the special reference spectrum FSR R The expression for the -λ1 curve (the second relation) is:

[0078] .

[0079] S102, based on the relationship between the free spectral range of the virtual reference interferometer and the wavelength, a special reference spectral intensity distribution is constructed.

[0080] Specifically, let the intensity of a special reference spectrum represent I. R It is a cosine function, initial phase Then the instantaneous angular frequency ω(λ1) and phase φ(λ1) of the cosine function satisfy:

[0081] ;

[0082] ;

[0083] Due to the special reference spectrum FSR R If it is always greater than zero, then the intensity of the special reference spectrum represents I. R It can be represented as:

[0084] .

[0085] S103, superimpose the measured spectral intensity of the optical interferometer with the special reference spectral intensity to obtain the superimposed total spectral intensity, and extract the spectral intensity of the upper envelope of the superimposed total spectral intensity.

[0086] Specifically, the measured spectral intensity I of the optical interferometer S As shown below:

[0087] ;

[0088] Superimposed total spectral intensity I SUM It is expressed as follows:

[0089] ;

[0090] The spectral intensity of the upper envelope in the superimposed total spectrum is expressed as follows:

[0091] ;

[0092] Among them, the special reference spectrum is a static spectrum, which is superimposed on the sensing spectrum in real time during the superposition process.

[0093] S104 acquires and monitors the change of characteristic wavelength with the measured physical quantity, and completes the measurement by using the relationship between the calibrated characteristic wavelength and the measured physical quantity.

[0094] S1041, based on the vernier effect, a unique wavelength point with a significant intensity change is obtained on the spectral intensity of the upper envelope, and the wavelength of this wavelength point is taken as the characteristic wavelength.

[0095] Specifically, when the spectrum of the optical interferometer and a special reference spectrum are within a certain wavelength range of the operating wavelength... The free spectral range is equal at each location (FSR). S =FSR R When the superimposed total spectrum is superimposed, a unique and easily identifiable wavelength point will appear in the upper envelope, namely the characteristic wavelength (CWL). This characteristic wavelength is unique within a given wavelength range, and its location can be calculated by the following formula:

[0096] ;

[0097] In addition to the direct calculations mentioned above, actual measurements can also be performed without relying on these calculations, by real-time processing and superimposing the total spectral intensity. And extract its envelope I envelope This is achieved by selecting a wavelength that matches the appearance characteristics of the characteristic wavelength. The characteristics of the characteristic wavelength are specifically twofold: first, the free spectral range (FSR) of the upper envelope on both sides of the characteristic wavelength is the largest, and the FSR decreases as it moves away from the characteristic wavelength; second, the upper envelope is mirror-symmetrical about the characteristic wavelength axis. envelope In the middle, the wavelengths of the first interference peak or valley on the left and right sides of the characteristic wavelength are λ. E1 and λ E2 In practical measurement scenarios, the characteristic wavelength can be expressed as:

[0098] .

[0099] S1042, monitors the change of the characteristic wavelength in real time to measure the physical quantity that corresponds to the cavity length and effective refractive index.

[0100] In this step, the relationship between the characteristic wavelength and the physical quantity X to be measured will be established, and the physical quantity and sensitivity will be measured.

[0101] The cavity length L of the optical interferometer S The effective refractive index n of the cavity medium changes with variations in external physical quantities X (such as strain ε, temperature T, displacement d, etc.). If the change in cavity length is ΔL... S Let Δn be the change in the effective refractive index of the medium inside the cavity, and ΔX be the change in the physical quantity. Then, their relationship can be expressed as follows:

[0102] ;

[0103] Specifically, the function G is composed of specific physical quantities X and ΔL. S The conversion relationship between n and n is determined. In actual measurement, this can be achieved through pre-calibration or calculation based on known physical quantity relationships. The specific implementation can be set according to the actual application; this embodiment does not impose any limitations.

[0104] Furthermore, the external physical quantity X will cause the cavity length L of the optical interferometer to change. S When the effective refractive index n of the cavity medium changes, the wavelength changes. Therefore, differentiating equation (2) with respect to the physical quantity X, the wavelength sensitivity of the optical interferometer can be expressed as:

[0105] ;

[0106] During actual measurement, changes in the external physical quantity X lead to changes in the cavity length L of the optical interferometer. S Or when the effective refractive index n of the medium inside the cavity changes, according to formula (2), the changed optical path It can be represented as:

[0107] ;

[0108] Correspondingly, the characteristic wavelength also changes accordingly, and the changed characteristic wavelength is denoted as . The formula is shown below:

[0109] ;

[0110] Correspondingly, the wavelength of the sensing spectrum The relative wavelength change is equal to the sum of the relative change in the effective refractive index n of the cavity medium and the relative change in the cavity length, which can be expressed as:

[0111] ;

[0112] When optical path When changes occur, according to formula (21), the wavelength change of the optical interferometer (i.e., the total drift of the monitoring peak / valley wavelength in the spectrum of a single optical interferometer) Δλ1 can be expressed as:

[0113] ;

[0114] The wavelength change can be obtained from the characteristic wavelengths before and after the change in formulas (15) and (20). , means as follows:

[0115] ;

[0116] According to formulas (22) and (23), the wavelength change of the characteristic wavelength is... The ratio of the wavelength change Δλ1 of the optical interferometer to the sensitivity amplification factor M of the vernier effect can be obtained, as follows:

[0117] ;

[0118] The value of M depends on two factors: the measurement range and the wavelength monitoring range of the spectrum. When the measurement range is constant, a larger wavelength monitoring range results in a larger M value. Conversely, a larger measurement range results in a smaller M value.

[0119] According to formulas (18) and (24), the sensitivity when the wavelength change of the characteristic wavelength caused by the physical quantity X changes can be obtained, as follows:

[0120] ;

[0121] In summary, this embodiment presents an interferometer sensing measurement method based on the vernier effect of a special reference spectrum. This method requires only a physical optical interferometer (sensing interferometer) to simultaneously achieve both unique wavelength identification and improved measurement sensitivity. Specifically, by superimposing a specially designed reference spectrum with the sensing spectrum output by the sensing interferometer, a characteristic wavelength (CWL) with unique appearance characteristics appears in the envelope of the superimposed total spectrum. This enables rapid and accurate wavelength identification and tracking, thereby achieving unambiguous measurement. Furthermore, the vernier effect enhances measurement sensitivity.

[0122] The following will use the Fabry-Perot interferometer as an example, combined with numerical simulation, to illustrate the following. The corresponding simulation parameters are set as follows: the effective refractive index n of the cavity medium of the optical interferometer is set to 1, and the wavelength monitoring range of the spectrum is 1450nm to 1650nm.

[0123] First, the cavity length of the optical interferometer was varied within a range of 300 μm to 340 μm to obtain the corresponding FSR. S -λ1 simulation curves and special reference spectra FSR R The -λ1 curve is shown in Figure 2. The light intensity I of the special reference spectrum is then obtained. R The formula is expressed, and the specific simulation curve is as follows: Figure 3 As shown by the black curve in the image.

[0124] Among them, special reference spectrum FSR R The -λ1 curve is represented as:

[0125] ;

[0126] Intensity expression of special reference spectrum I R Represented as:

[0127] ;

[0128] Furthermore, according to the calculation formula (11), assuming the cavity length of the sensing cavity is 320 μm, the simulation diagram of the corresponding sensing spectrum is obtained as follows. Figure 3 As shown by the red curve in the image.

[0129] Given a sensing cavity length of 320 μm, the expression for the light intensity of the sensing spectrum is... Represented as:

[0130] ;

[0131] According to formulas (13), (27) and (28), the total output superimposed spectrum I can be obtained. SUM The corresponding simulation curves are attached. Figure 4 As shown, the black curve represents the superimposed total spectrum, and the red curve represents the upper envelope.

[0132] Finally, according to formula (16), the characteristic wavelength (CWL) can be calculated to be 1550 nm. The corresponding simulation diagram is shown in Figure 4. According to formula (18), the sensitivity of the optical interferometer to wavelength change caused by cavity length change is 4.83. According to formula (24), the corresponding sensitivity amplification factor M is calculated to be 1.04. According to formula (25), the sensitivity of the characteristic wavelength change caused by the cavity length change of the optical interferometer is calculated to be 5. .

[0133] The above embodiments illustrate the basic principles and implementation methods of the present invention, aiming to help understand the core concept and key steps of the invention. It should be understood that these embodiments are merely examples and do not limit the scope of application of the present invention. Those skilled in the art, based on their understanding of the concept of the present invention, can make various equivalent improvements to specific steps, parameter configurations, or system structures. These improvements also fall within the protection scope of the present invention, as defined in the appended claims.

Claims

1. An interferometer sensing measurement method based on the vernier effect of a special reference spectrum, characterized in that, Includes the following steps: S101, based on the spectral measurement range and the range of interferometer cavity length variation caused by the measured physical quantity, establish the relationship between the free spectral range of the virtual reference interferometer and the wavelength, as follows: Based on the cavity length of the optical interferometer and the effective refractive index of the cavity medium, a first relationship is established between the free spectral range within the spectral measurement range and the wavelengths corresponding to the interference peaks / valleys. Based on the first relationship, the minimum cavity length L is calculated respectively. min and the shortest wavelength λ for arbitrarily monitoring interference peaks / valleys min The corresponding first free spectral range FSR1 under the condition, and at the maximum cavity length L max and the longest wavelength λ for arbitrarily monitoring interference peaks / valleys max The corresponding second free spectral range FSR2 under the given conditions; With (λ) min (FSR1) and (λ) max Using FSR2 as the coordinate point, a second relationship describing the change of the free spectral range with wavelength in a special reference spectrum is obtained by fitting, which serves as the relationship of the free spectral range with wavelength for a virtual reference interferometer. S102, based on the relationship between the free spectral range of the virtual reference interferometer and the wavelength, a special reference spectral intensity distribution is constructed; S103, superimpose the measured spectral intensity of the optical interferometer with the spectral intensity of a special reference to obtain the superimposed total spectral intensity, and extract the spectral intensity of the upper envelope of the superimposed total spectral intensity; S104, acquire and monitor the change of characteristic wavelength with the measured physical quantity, and complete the measurement by means of the calibrated characteristic wavelength and the measured physical quantity, as follows: Based on the vernier effect, a unique wavelength point with a significant intensity change is obtained on the spectral intensity of the upper envelope, and the wavelength of this wavelength point is taken as the characteristic wavelength. Real-time monitoring of changes in the characteristic wavelength enables the measurement of physical quantities that correspond to the cavity length and effective refractive index.

2. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 1, characterized in that, The first relation is expressed as follows: ； in, The free spectral range is represented within the spectral measurement range; λ1 and λ2 represent the wavelengths corresponding to two adjacent interference peaks / valleys, respectively; L S represents the cavity length of the optical interferometer; n represents the effective refractive index of the cavity medium.

3. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 2, characterized in that, The second relation is expressed as follows: ； ； ； ； ； in, This indicates the free spectral range within a specific reference spectrum.

4. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 3, characterized in that, The specific reference spectral intensity is represented as follows: ； in, Indicates the intensity of a specific reference spectrum.

5. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 4, characterized in that, The total superimposed spectral intensity is expressed as follows: ； in, Indicates the total superimposed spectral intensity; This represents the measured intensity of the sensor spectrum.

6. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 5, characterized in that, The spectral intensity of the upper envelope is expressed as follows: ； in, This represents the spectral intensity of the upper envelope.

7. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 6, characterized in that, Based on the spectral intensity of the upper envelope, the wavelength of the unique wavelength point with a significant intensity change is obtained as the characteristic wavelength, including: Retrieve from the first relation With the free spectral range in the second relation When they are equal, the wavelength of the wavelength point appearing in the spectral intensity of the upper envelope is taken as the characteristic wavelength, as follows: ； in, Indicates the characteristic wavelength.

8. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 6, characterized in that, Based on the spectral intensity of the upper envelope, the wavelength of the unique wavelength point with a significant intensity change is obtained as the characteristic wavelength, including: On the spectral intensity of the upper envelope, identify the wavelength point that satisfies the spectral intensity of both upper envelopes with the largest free spectral range and the free spectral range of both upper envelopes decreases away from the upper envelopes, and take the wavelength of the wavelength point as the characteristic wavelength. The spectral intensity of the upper envelope is mirror-symmetric about the characteristic wavelength; within the spectral intensity of the upper envelope, the wavelengths λ corresponding to the first interference peak / valley on either side of the characteristic wavelength are identified. E1 and λ E2 The characteristic wavelength is represented as follows: ； in, Indicates the characteristic wavelength.

9. The interferometer sensing and measurement method based on the vernier effect of a special reference spectrum according to claim 2, characterized in that, After measuring the physical quantities that correspond to the cavity length and effective refractive index, the method further includes: measuring the sensitivity when changes in the physical quantities cause changes in the wavelength of the characteristic wavelength, as expressed below: ； in, The sensitivity that indicates the change in wavelength of a characteristic wavelength caused by a change in a physical quantity; The sensitivity amplification factor representing the vernier effect; This indicates the wavelength sensitivity of the optical interferometer. It represents the physical quantity being measured.

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