High-sensitivity measurement method based on single interferometer and vernier effect

Abstract

The invention provides a high-sensitivity measurement method based on a single interferometer and a vernier effect, and belongs to the field of optical signal processing, and the method comprises the steps: determining a central wavelength according to the spectrum of a sensing interferometer; turning over the spectrum of the sensing interferometer along a horizontal axis of the wavelength direction of the spectrum of the sensing interferometer by taking the central wavelength as a center to obtain a spectrum of a reference interferometer; performing signal processing on the sensing interferometer spectrum and the reference interferometer spectrum to obtain an output spectrum; extracting a vernier envelope of the output spectrum, and obtaining a free spectrum range of the vernier envelope according to the vernier envelope; and obtaining a sensitivity amplification factor based on the vernier effect according to the free spectral range enveloped by the vernier and the free spectral range of the sensing interferometer. According to the method disclosed by the invention, high-sensitivity measurement can be completed only by using a single interferometer, two interferometers with similar free spectral ranges do not need to be prepared by an accurate and complex manufacturing technology any more, the cost of the whole detection scheme is saved, and the method has great practicability.

Description

Technical Field

[0001] The invention belongs to the field of optical signal processing, and in particular relates to a high-sensitivity measurement method based on a single interferometer and a vernier effect. Background Art

[0002] In recent years, optical measurement methods based on the vernier effect have been widely used in sensor detection in various industries due to their advantages of enhanced sensitivity. Traditional vernier effect measurement methods usually include two optical interferometers, which can be called sensing interferometers and reference interferometers. When the two interferometers meet the vernier effect conditions, that is, the free spectral range (FSR) of the reference interferometer is close to the FSR of the sensing interferometer, the two interferometers are connected in series or in parallel, and the corresponding vernier envelope can be extracted according to their output spectra. Compared with detecting a single sensing interferometer, the sensitivity can be significantly improved by detecting the response of the vernier envelope to the measured value.

[0003] Although the traditional vernier effect measurement method can significantly enhance the sensitivity, the degree of sensitivity enhancement is closely related to the proximity of the FSR of the sensing interferometer and the FSR of the reference interferometer. However, in order to accurately control and manufacture a reference interferometer with a small FSR difference with the sensing interferometer, it is usually necessary to use technologies such as femtosecond laser processing, which not only complicates the preparation process of the reference interferometer, but also increases the production cost. In addition, during the entire process of sensing measurement, it is necessary to ensure that only the sensing interferometer is disturbed by the measured value, and the reference interferometer should always remain stable, otherwise the generated vernier envelope will produce a random response to the measured value, which will seriously affect the accuracy of the measurement result. However, it is very difficult to design such a detection structure that keeps the reference interferometer stable at all times. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present application proposes a high-sensitivity measurement method based on a single interferometer and a vernier effect, which can significantly improve the measurement sensitivity by using only one optical interferometer.

[0005] The high-sensitivity measurement method based on a single interferometer and a vernier effect comprises:

[0006] Obtaining a sensor interferometer spectrum through a sensor interferometer, and determining a central wavelength according to the sensor interferometer spectrum;

[0007] Taking the central wavelength as the center, the sensor interferometer spectrum is flipped along the horizontal axis of the wavelength direction of the sensor interferometer spectrum to obtain a reference interferometer spectrum;

[0008] Performing signal processing on the sensor interferometer spectrum and the reference interferometer spectrum to obtain an output spectrum;

[0009] Extracting a vernier envelope of the output spectrum, and obtaining a free spectral range of the vernier envelope according to the vernier envelope;

[0010] According to the free spectral range of the vernier envelope and the free spectral range of the sensor interferometer, a sensitivity amplification factor based on the vernier effect is obtained.

[0011] Determining the central wavelength according to the sensor interferometer spectrum includes:

[0012] Extracting the maximum value of the spectral wavelength range and the minimum value of the spectral wavelength range in the sensor interferometer spectrum;

[0013] The average value of the maximum value of the spectral wavelength range and the minimum value of the spectral wavelength range is taken as the central wavelength.

[0014] The central wavelength is calculated as follows:

[0015]

[0016] Among them, λ 0 is the central wavelength, λ max is the maximum value of the spectral wavelength range, λ min is the minimum value of the spectral wavelength range.

[0017] The free spectral range of the cursor envelope is calculated as follows:

[0018]

[0019] Among them, FSR e is the free spectral range of the cursor envelope, φ S is the optical path difference, λ 0 is the central wavelength, λ e1 is the wavelength corresponding to the adjacent peak or valley value on one side of the central wavelength, λ e2 is the center wavelength λ 0 The wavelength corresponding to the adjacent peak or valley on the other side.

[0020] The sensitivity amplification factor based on the vernier effect is calculated as follows:

[0021]

[0022] Where M is the sensitivity magnification factor based on the vernier effect, FSR e is the free spectral range of the cursor envelope, FSR s is the free spectral range of the sensing interferometer, λ 0 is the central wavelength, λ e1 is the wavelength corresponding to the adjacent peak or valley value on one side of the central wavelength, λ e2 is the center wavelength λ 0The wavelength corresponding to the adjacent peak or valley on the other side.

[0023] The high-sensitivity measurement method based on a single interferometer and a vernier effect further includes:

[0024] The output light intensity of the output spectrum is the superposition of the spectral intensity of the sensing interferometer and the spectral intensity of the reference interferometer.

[0025] The output light intensity is calculated as follows:

[0026]

[0027] Among them, I sum is the intensity of the output spectrum, I s is the spectral intensity of the sensor interferometer, I r is the spectral intensity of the reference interferometer spectrum, λ 0 is the central wavelength, φ S is the optical path difference, and λ is the wavelength corresponding to the intensity of the output spectrum.

[0028] Beneficial effects:

[0029] The present application proposes a high-sensitivity measurement method based on a single interferometer and a vernier effect. It does not require the use of precision machining or other means to actually produce a reference interferometer whose FSR matches the FSR of the sensing interferometer. Instead, the sensing interferometer spectrum is flipped and transformed to construct a reference interferometer spectrum with a FSR similar to the sensing interferometer spectrum. This eliminates the need for precise and complex manufacturing technology to prepare two interferometers with similar free spectral ranges, saves the cost of the entire detection solution, and has great practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of a high-sensitivity measurement method based on a single interferometer and a vernier effect according to an embodiment of the present application;

[0031] Figure 2 A simulation curve diagram of the sensor interferometer spectrum of an embodiment of the present application;

[0032] Figure 3 A simulation curve diagram of a reference interferometer spectrum of an embodiment of the present application;

[0033] Figure 4 A simulation curve diagram of the output spectrum of the embodiment of the present application;

[0034] Figure 5 The low-frequency component of the output spectrum and the cursor envelope simulation curve of the embodiment of the present application. DETAILED DESCRIPTION

[0035] The specific implementation of the present application is further described in detail below in conjunction with the drawings and examples.

[0036] In the field of optical signal processing, a single interferometer is used to detect physical quantities, and this measurement method has limited sensitivity. Usually, two interferometers with similar FSRs can be prepared and combined to generate a vernier effect and significantly improve sensitivity. In contrast, the measurement method based on a single interferometer and a vernier effect proposed in this application can generate a vernier effect to achieve high-sensitivity measurement by detecting physical quantities using only one interferometer.

[0037] Example:

[0038] This embodiment proposes a high-sensitivity measurement method based on a single interferometer and a vernier effect, which is applicable to: Fabry-Perot interferometer, Michelson interferometer, Mach-Zehnder interferometer, and Sagnac interferometer, and is also applicable to interferometers such as dual-mode fiber interferometers and few-mode fiber interferometers. The following takes the sensor interferometer of the Fabry-Perot structure as an example to illustrate the implementation steps included in the high-sensitivity measurement method proposed in this embodiment, but the process of this application can be applied to sensor interferometers of all structures and the case where the sensor interferometer and the reference interferometer spectral intensity are multiplied, such as Figure 1 As shown, including:

[0039] Step S1: obtaining a sensor interferometer spectrum through a sensor interferometer, and determining a central wavelength according to the sensor interferometer spectrum, including:

[0040] Step S1.1: extracting the maximum value of the spectral wavelength range and the minimum value of the spectral wavelength range in the sensor interferometer spectrum;

[0041] Step S1.2: taking the average value of the maximum value of the spectral wavelength range and the average value of the minimum value of the spectral wavelength range as the central wavelength.

[0042] In this embodiment, a sensor interferometer spectrum is first obtained by a sensor interferometer, and the middle value of the wavelength range of the entire sensor interferometer spectrum is taken as the central wavelength λ 0 , which is related to the maximum value λ of the spectral wavelength range max and the minimum value λ min The following relations are satisfied:

[0043]

[0044] Among them, λ 0 is the central wavelength, λmax is the maximum value of the spectral wavelength range, λ min is the minimum value of the spectral wavelength range.

[0045] Step S2: taking the central wavelength as the center, flipping the sensor interferometer spectrum along the horizontal axis of the wavelength direction of the sensor interferometer spectrum to obtain a reference interferometer spectrum;

[0046] In this embodiment, the sensor interferometer spectrum is 0 The reference interferometer spectrum is obtained by flipping along the wavelength axis.

[0047] Step S3: performing signal processing on the sensor interferometer spectrum and the reference interferometer spectrum to obtain an output spectrum;

[0048] According to the reference interferometer spectrum obtained in step S2, add or multiply it with the sensor interferometer spectrum obtained in step S1 to obtain the output spectrum. Then extract the vernier envelope of the output spectrum, and use it according to λ 0 The wavelength λ corresponding to the adjacent peak or valley e1 and λ e2 , get the free spectral range FSR of the cursor envelope e , which can be expressed as:

[0049]

[0050] Among them, FSR e is the free spectral range of the cursor envelope, φ S is the optical path difference, λ 0 is the central wavelength, λ e1 and λ e2 Represent the central wavelength λ 0 The wavelengths corresponding to two adjacent peaks or valleys on either side.

[0051] Step S4: extracting the vernier envelope of the output spectrum, and obtaining the free spectrum range of the vernier envelope according to the vernier envelope;

[0052] Step S5: Obtaining a sensitivity amplification factor based on the vernier effect according to the free spectral range of the vernier envelope and the free spectral range of the sensor interferometer.

[0053] In this embodiment, the sensitivity magnification factor M of the vernier effect sensor can be obtained by FSR e Calculation, the calculation formula is as follows:

[0054]

[0055] Where M is the sensitivity magnification factor based on the vernier effect, FSR e is the free spectral range of the cursor envelope, FSRs is the free spectral range of the sensing interferometer, λ 0 is the central wavelength, λ e1 and λ e2 Represent the central wavelength λ 0 The wavelengths corresponding to the two adjacent peaks or valleys on both sides. e1 ,λ e2 With λ 0 The closer you are to the object, the larger M becomes, and the more obvious the sensitivity improvement effect becomes.

[0056] The high-sensitivity measurement method based on a single interferometer and a vernier effect further includes:

[0057] The intensity of the output spectrum is the sum or product of the spectrum intensity of the sensing interferometer and the spectrum intensity of the reference interferometer.

[0058] In this embodiment, the spectral intensity I of the sensor interferometer is usually s and its free spectral range FSR s Can be expressed as:

[0059]

[0060] Among them, λ 1 and λ 2 Represent the central wavelength λ 0 The wavelengths corresponding to the two adjacent peaks or valleys on both sides are converted into the sensor interferometer spectrum in λ 0 The reference interferometer spectrum is obtained by flipping along the wavelength axis, and its intensity I r The expression is as follows:

[0061]

[0062] Therefore, the output light intensity I of the output spectrum of the sensor interferometer and the reference interferometer is sum It can be expressed as:

[0063]

[0064] Among them, I sum is the output light intensity, I s is the spectral intensity of the sensor interferometer, I r is the spectral intensity of the reference interferometer spectrum, λ 0 is the center wavelength, and λ is the wavelength corresponding to the output light intensity.

[0065] Among them, the corresponding I sum The simulation curve of wavelength λ is shown in the attached figure. Figure 5 As shown, Represents the low-frequency component of the output spectrum, then the low-frequency component λ e1 and λe2 The following relations are satisfied:

[0066]

[0067] At the same time, the cursor envelope curve can be obtained by fitting the extreme value of the output spectrum simulation curve, as shown in the attached figure. Figure 5 As shown. Therefore, λ e1 and λ e2 The difference is the free spectral range (FSR) of the cursor envelope. e , which can be expressed as:

[0068] FSR e =|λ e1 -λ e2 | (9)

[0069] Combining equations (8) and (9), we can derive equation (2).

[0070] Taking numerical simulation as an example, the corresponding simulation parameters are set as follows: the refractive index n of the sensor interferometer and the cavity length L of the sensor interferometer s 1 and 800 μm respectively, and the wavelength range of the spectrum is 1400 nm to 1600 nm. According to calculation formula (4), the spectral intensity I of the sensor interferometer can be calculated: s The corresponding simulation curve is shown in the attached Figure 2 According to step S1, the central wavelength λ can be calculated. 0 is 1500nm; then determine the spectral intensity I of the reference interferometer according to formula (6): r , the sensor interferometer spectrum is centered at 1500nm, and the reference interferometer spectrum can be obtained by flipping along the wavelength horizontal axis. The simulation curve is shown in the attached figure. Figure 3 As shown; and then according to the calculation formula (7), the output light intensity I of the output spectrum can be calculated sum The simulation curve is shown in the attached Figure 4 As shown, the free spectral range FSR of the output spectral cursor envelope is calculated according to step S3. e Finally, according to step S5, the M value can be calculated to be 19, thereby increasing the measurement sensitivity by 19 times.

[0071] The present embodiment proposes a high-sensitivity measurement method based on a single interferometer and a vernier effect. High-sensitivity measurements can be completed using only a single interferometer. By flipping and transforming the sensor interferometer spectrum, a reference interferometer spectrum with a FSR similar to that of the sensor interferometer spectrum is constructed. This eliminates the need for precise and complex manufacturing technology to prepare two interferometers with similar free spectral ranges, saves the cost of the entire detection solution, and has great practicality.

[0072] The various embodiments in the present application are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0073] The protection scope of the present application is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present disclosure without departing from the scope and spirit of the present disclosure. If these changes and modifications fall within the scope of the claims of the present disclosure and their equivalents, the intention of the present disclosure also includes these changes and modifications.

Claims

1. A high-sensitivity measurement method based on a single interferometer and a vernier effect, characterized in that: include: Obtaining a sensor interferometer spectrum through a sensor interferometer, and determining a central wavelength according to the sensor interferometer spectrum; Taking the central wavelength as the center, the sensor interferometer spectrum is flipped along the horizontal axis of the wavelength direction of the sensor interferometer spectrum to obtain a reference interferometer spectrum; Performing signal processing on the sensor interferometer spectrum and the reference interferometer spectrum to obtain an output spectrum; Extracting a vernier envelope of the output spectrum, and obtaining a free spectral range of the vernier envelope according to the vernier envelope; According to the free spectral range of the vernier envelope and the free spectral range of the sensor interferometer, a sensitivity amplification factor based on the vernier effect is obtained.

2. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 1, characterized in that: Determining the central wavelength according to the sensor interferometer spectrum includes: Extracting the maximum value of the spectral wavelength range and the minimum value of the spectral wavelength range in the sensor interferometer spectrum; The average value of the maximum value of the spectral wavelength range and the minimum value of the spectral wavelength range is taken as the central wavelength.

3. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 2, characterized in that: The central wavelength is calculated as follows: Among them, λ0 is the central wavelength, λ max is the maximum value of the spectral wavelength range, λ min is the minimum value of the spectral wavelength range.

4. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 1, characterized in that: The free spectral range of the cursor envelope is calculated as follows: Among them, FSR e is the free spectral range of the cursor envelope, φ S is the optical path difference, λ0 is the central wavelength, λ e1 is the wavelength corresponding to the adjacent peak or valley value on one side of the central wavelength, λ e2 It is the wavelength corresponding to the adjacent peak or valley on the other side of the central wavelength λ0.

5. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 1, characterized in that: The sensitivity amplification factor based on the vernier effect is calculated as follows: Where M is the sensitivity magnification factor based on the vernier effect, FSR e is the free spectral range of the cursor envelope, FSR s is the free spectral range of the sensor interferometer, λ0 is the central wavelength, λ e1 is the wavelength corresponding to the adjacent peak or valley value on one side of the central wavelength, λ e2 It is the wavelength corresponding to the adjacent peak or valley on the other side of the central wavelength λ0.

6. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 1, characterized in that: The high-sensitivity measurement method based on a single interferometer and a vernier effect further includes: The intensity of the output spectrum is the superposition of the spectral intensity of the sensing interferometer and the spectral intensity of the reference interferometer.

7. The high-sensitivity measurement method based on a single interferometer and a vernier effect according to claim 6, characterized in that: The intensity of the output spectrum is calculated as follows: Among them, I sum is the intensity of the output spectrum, I s is the spectral intensity of the sensor interferometer, I r is the spectral intensity of the reference interferometer spectrum, λ0 is the central wavelength, φ s is the optical path difference, and λ is the wavelength corresponding to the intensity of the output spectrum.

Images