A device and method for measuring the size and structural parameters of a hollow core optical fiber

Abstract

The application relates to the technical field of optical fibers, and discloses a device and a method for measuring the size structure parameters of a hollow-core optical fiber, which comprise a light source emitting end (11), an optical circulator (12), an optical spectrometer (13) and a rotary displacement table (14). The light source emitting end (11) is connected with a first port (1) of the optical circulator (12), a second port (2) of the optical circulator (12) is aligned with the side of a hollow-core optical fiber (15) to be measured, which has been stripped of a coating layer, the hollow-core optical fiber (15) to be measured is arranged in the rotary displacement table (14), a third port (3) of the optical circulator (12) is connected with the optical spectrometer (13), the hollow-core optical fiber (15) to be measured is a band gap hollow-core optical fiber or an N-layer nested anti-resonant hollow-core optical fiber, wherein N is a positive integer, the detection device is simple in composition, the detection method is convenient to operate, simple to calculate and good in measurement accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fibers, and more particularly to a device and method for measuring the size and structure parameters of a hollow-core optical fiber. BACKGROUND

[0002] In recent years, due to the unique transmission mechanism and excellent performance of hollow-core optical fibers, especially anti-resonant hollow-core optical fibers, which can significantly reduce the loss and nonlinear effects of optical fibers by transmitting optical signals in the cavity, the application scenarios of hollow-core optical fibers have rapidly expanded.

[0003] In the manufacturing process of hollow-core optical fibers, the performance of the optical fibers is highly dependent on the size of the microstructure parameters, and the precision requirement of the drawing process is extremely strict. In the traditional method, the optical fiber production needs to be interrupted during the drawing process, and the microstructure parameters inside the optical fiber are measured by observing the cross section through a microscope. This method is time-consuming and inefficient, and seriously affects the production efficiency and yield of the optical fiber.

[0004] The prior art proposes a method for solving the size and structure parameters of a hollow-core optical fiber by irradiating different positions of the hollow-core optical fiber and collecting multiple scattered light beams formed after passing through the hollow-core optical fiber in different paths. This method requires accurate measurement of the incident angle and the exit angle, and calculates the size and structure parameters based on the incident angle and the exit angle. The operation and calculation process is complex, and due to the measurement error of the incident angle and the exit angle, the size and structure parameters obtained by the final solution have certain errors. SUMMARY

[0005] To overcome the defects of the prior art, such as angle measurement error and complex operation and calculation, the present application provides a device for measuring the size and structure parameters of a hollow-core optical fiber without angle measurement and with simple operation and calculation.

[0006] To solve the above technical problems, the technical solution of the present application is as follows:

[0007] A device for measuring the size and structure parameters of a hollow-core optical fiber, comprising a light source emitting end, an optical circulator, an optical spectrometer and a rotary displacement stage.

[0008] The light source emitting end is connected to the first port of the optical circulator, the second port of the optical circulator is aligned with the side of the hollow-core optical fiber to be measured with the coating layer removed, the hollow-core optical fiber to be measured with the coating layer removed is placed in the rotary displacement stage, and the third port of the optical circulator is connected to the optical spectrometer.

[0009] The hollow-core optical fiber to be measured is a bandgap hollow-core optical fiber or a layer-nested anti-resonant hollow-core optical fiber, wherein, is a positive integer.

[0010] The application further provides a measurement method of the measurement device for the size structure parameters of the hollow optical fiber.

[0011] The light source emits a light beam, the light beam is transmitted from the first port of the optical circulator to the second port of the optical circulator, the to-be-measured hollow optical fiber is rotated by the rotary displacement table, the light beam emitted from the second port of the optical circulator is normally incident on the side surface of the to-be-measured hollow optical fiber with the coating layer removed, the side surface of the to-be-measured hollow optical fiber reflects the reflected light, and the reflected light is received by the optical spectrum analyzer after being transmitted from the second port of the optical circulator to the third port of the optical circulator.

[0012] The optical spectrum analyzer is used to obtain the interference spectrum of the reflected light.

[0013] The time-domain spectrum of the interference spectrum is obtained by Fourier transform, the resonance peak peak value analysis is performed on the time-domain spectrum, the correspondence between the size structure parameters of the to-be-measured hollow optical fiber and the resonance peaks of the time-domain spectrum is determined based on the resonance peak peak value analysis result, and the size structure parameters of the to-be-measured hollow optical fiber are calculated based on the correspondence and the time information of the resonance peaks.

[0014] The size structure parameters of the to-be-measured hollow optical fiber are calculated based on the correspondence and the time information of the resonance peaks.

[0015] Compared with the prior art, the technical scheme of the application has the following beneficial effects:

[0016] The measurement device uses the optical circulator to make the light beam emitted from the light source emitting end input from the first port of the optical circulator and output from the second port to irradiate on the to-be-measured hollow optical fiber, and the reflected light can return along the second port of the optical circulator and be directly input to the optical spectrum analyzer through the third port of the optical circulator, compared with the method of indirectly inputting the reflected light to the optical spectrum analyzer, the intermediate loss and noise can be reduced, the measurement accuracy is improved, the detection device is simple in composition, the detection method is convenient in operation, simple in calculation and has good measurement accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The measurement device for measuring the size structure parameters of the hollow optical fiber is used to measure the nested anti-resonant hollow optical fiber. The schematic diagram of the nested anti-resonant hollow optical fiber is shown in FIG. 1.

[0018] Figure 2 The schematic diagram of the measurement device for measuring the size structure parameters of the hollow optical fiber is used to measure the bandgap hollow optical fiber.

[0019] Figure 3 The flowchart of the measurement method of the measurement device for the size structure parameters of the hollow optical fiber is shown in FIG. 2.

[0020] Figure 4A structural schematic diagram of the five-ring double-layer nested anti-resonant hollow core fiber proposed in Embodiment 3;

[0021] Figure 5 A principle diagram of interference of different propagation paths of reflected light when measuring the five-ring double-layer nested anti-resonant hollow core fiber proposed in Embodiment 3;

[0022] Figure 6 A four-reflected-beam interference spectrum diagram proposed in Embodiment 3;

[0023] Figure 7 A four-reflected-beam interference time-domain spectrum diagram proposed in Embodiment 3. DETAILED DESCRIPTION

[0024] The accompanying drawings are only for illustrative purposes and should not be construed as limiting the patent;

[0025] In order to better illustrate the embodiments, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual size of the product;

[0026] It is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0027] The technical solutions of the present application will be further described below in combination with the drawings and embodiments.

[0028] Embodiment 1

[0029] The present embodiment proposes a device for measuring the size and structural parameters of an anti-resonant hollow core fiber, Figure 1 The present embodiment proposes a device for measuring the size and structural parameters of an anti-resonant hollow core fiber, A structural schematic diagram of the five-ring double-layer nested anti-resonant hollow core fiber proposed in Embodiment 3; Figure 2 A structural schematic diagram of the five-ring double-layer nested anti-resonant hollow core fiber proposed in Embodiment 3; Figure 1 And Figure 2 The specific shape of the rotary displacement table 14 is omitted in the drawings, and only the rotation direction is drawn.

[0030] As Figure 1 shown, the device for measuring the size and structural parameters of an anti-resonant hollow core fiber of the present embodiment includes a light source emitting end 11, an optical circulator 12, an optical spectrum analyzer 13 and a rotary displacement table 14;

[0031] The light source emitting end 11 is connected to the first port 1 of the optical circulator 12, the second port 2 of the optical circulator 12 is aligned with the side surface of the anti-resonant hollow core fiber 15 whose coating layer has been stripped, the anti-resonant hollow core fiber 15 whose coating layer has been stripped is placed in the rotary displacement table 14, and the third port 3 of the optical circulator 12 is connected to the optical spectrum analyzer 13;

[0032] The to-be-measured hollow core fiber 15 is a bandgap hollow core fiber or Layer nested anti-resonant hollow core fiber, wherein, is a positive integer.

[0033] In the specific implementation process, the measuring device uses an optical circulator to make the light beam emitted from the light source emission end input from the first port of the optical circulator and output from the second port to irradiate on the to-be-measured hollow core fiber, and the reflected light can return along the second port of the optical circulator and directly input to the spectrometer through the third port of the optical circulator, compared with the method of indirectly inputting the reflected light to the spectrometer, the intermediate loss and noise can be reduced, so that the measurement accuracy is improved, and the detection device has simple composition, the detection method has convenient operation, simple calculation and good measurement accuracy.

[0034] As an exemplary illustration, the wide spectrum light source selected by the present application is an ASE wide spectrum light source.

[0035] As an exemplary illustration, the purpose of using the optical circulator 12 is to directly input the received reflected light interference spectrum to the spectrometer, the optical circulator 12 can be replaced by other single devices that can achieve the purpose, and the optical circulator 12 can also be replaced by combining multiple devices.

[0036] In an optional embodiment, the second port 2 of the optical circulator 12 is connected with a single-mode jumper wire, and the side of the to-be-measured hollow core fiber 15 with the coating layer removed is aligned.

[0037] As an exemplary illustration, the purpose of using the single-mode jumper wire is to more completely and non-destructively collect the interference spectrum reflected back by the to-be-measured fiber irradiated from the side of the light source.

[0038] In an optional embodiment, the light source emission end 11 is connected with the first port 1 of the optical circulator 12 through a fiber joint.

[0039] In an optional embodiment, the light source emitted by the light source emission end 11 is a wide spectrum light source.

[0040] As an exemplary illustration, it is necessary to use a wide spectrum light source, and the accuracy of the measurement needs to consider the free spectral range (FSR) of the FP cavity during the measurement, and the calculation formula is as follows:

[0041]

[0042] Wherein is the speed of light, is the refractive index of the medium in the cavity, The length of the FP cavity. In the measurement, it should be ensured that one FSR can cover multiple interference periods, and enough interference fringes can be captured. A wide spectrum light source can ensure that one FSR can cover multiple interference periods, so that the derivation of the cavity length is more stable and accurate.

[0043] Embodiment 2

[0044] The embodiment proposes a measurement method of the measurement device of the size and structure parameters of the hollow core fiber described in embodiment 1, Figure 3 The flowchart of the measurement method of the measurement device of the size and structure parameters of the hollow core fiber proposed in the embodiment is shown in the figure;

[0045] The measurement method of the measurement device of the size and structure parameters of the hollow core fiber includes the following steps:

[0046] S1: Let the light source emitting end 11 emit a light beam, the light beam is transmitted to the second port 2 of the optical circulator 12 through the first port 1 of the optical circulator 12, and the rotating displacement table 14 is used to rotate the hollow core fiber to be measured 15, so that the light beam emitted from the second port 2 of the optical circulator 12 is normally incident on the side surface of the hollow core fiber to be measured 15 which has been stripped of the coating layer. The side surface of the hollow core fiber to be measured 15 reflects the reflected light, and the reflected light is transmitted to the third port 3 of the optical circulator 12 through the second port 2 of the optical circulator 12, and then received by the optical spectrum analyzer 13;

[0047] S2: Obtain the interference spectrum of the reflected light by using the optical spectrum analyzer 13;

[0048] S3: Fourier transform the interference spectrum to obtain the time domain spectrum of the interference spectrum, and perform resonance peak peak value analysis on the time domain spectrum, and determine the correspondence between the size and structure parameters of the hollow core fiber to be measured 15 and each resonance peak of the time domain spectrum based on the resonance peak peak value analysis result;

[0049] S4: Based on the correspondence and the time information of the resonance peak, the size and structure parameters of the hollow core fiber to be measured 15 are calculated.

[0050] In an optional embodiment, the step of performing resonance peak peak value analysis on the time domain spectrum, and determining the correspondence between the size and structure parameters of the hollow core fiber to be measured 15 and each resonance peak of the time domain spectrum based on the resonance peak peak value analysis result includes:

[0051] Based on the structure of the hollow core fiber to be measured 15, the total number of light beams of the reflected light is determined The expression of the total number of light beams includes:

[0052]

[0053] In the formula, For integers greater than or equal to 0, when When, it indicates that the hollow fiber 15 under test is a bandgap hollow fiber; when When it is a positive integer, This indicates that the hollow fiber under test is 15. Nested anti-resonant hollow fiber;

[0054] Based on the total number of beams Determine the total number of resonance peaks in the time-domain spectrum. Total number of resonance peaks The expressions include:

[0055]

[0056] Let the first of the reflected light be... Beam and the first The absolute value of the optical path difference between beams is ,in, and , The total number equals ;

[0057] When the hollow fiber under test 15 is a bandgap hollow fiber ,in, This indicates the thickness of the first layer of the hollow-core optical fiber 15 from the outside in, i.e., the cladding thickness. express The refractive index of the corresponding structure;

[0058] When the hollow fiber to be tested is 15 Nested anti-resonant hollow fiber, and hour, include , and ,in, , , , The diameter of the second layer structure from the outside to the inside of the hollow fiber 15 under test is indicated, which is the diameter of the first layer of nested tubes. express The refractive index of the corresponding nested tube;

[0059] When the hollow fiber to be tested is 15 Nested anti-resonant hollow fiber, and At that time, if ,but ,like ,but ,in, This indicates the number of the hollow fiber 15 under test from the outside in. The difference between the diameters of the layer structures The difference between the diameters of the layer structures The difference between the diameters of the layer structures The refractive index of the corresponding nested tube The refractive index of the corresponding nested tube

[0060] According to the structure of the to-be-measured hollow optical fiber 15 In descending order of numerical values In descending order of numerical values

[0061] Resonance peak peak value analysis is performed on the time domain spectrum to obtain The peak values of the resonance peaks, and In descending order of numerical values The resonance peak with the largest peak value corresponds to the numerical value with the largest value The resonance peak with the largest peak value corresponds to the numerical value with the largest value Wherein, is a positive integer and .

[0062] As an example, due to different optical path differences resulting in interference components, and The time domain spectrum obtained after Fourier transform of the interference components corresponds to resonance peaks, so that the target result can be calculated according to the correspondence between the resonance peaks and the optical path difference , that is, the correspondence between the resonance peaks and the size and structure parameters of the to-be-measured hollow optical fiber 15.

[0063] In an optional embodiment, the expression of the size and structure parameters of the to-be-measured hollow optical fiber 15 includes:

[0064]

[0065]

[0066] In the formula, The time coordinate value of the corresponding resonance peak The time coordinate value of the corresponding resonance peak The time coordinate value of the corresponding resonance peak The time coordinate value of the corresponding resonance peak

[0067] In an optional embodiment, before performing resonance peak peak value analysis on the time domain spectrum, an interference model of the beam light is constructed, and the expression of the interference model of the beam light includes: The expression of the interference model of the beam light

[0068]

[0069]

[0070] In the formula, , , , and Consider it as 0. The reflectivity of the outer wall of the cladding of the optical fiber under test is given. The transmission loss is the outer wall of the cladding of the optical fiber under test. The reflectivity is the surface area at the contact between the inner wall of the cladding and the nested tube structure. This refers to the transmission loss at the interface between the inner wall of the cladding and the nested tube structure. For the first The reflectivity of nested tubes ( ), For the first The reflectivity of nested tubes ( ), For the first Transmission loss of nested tubes ( ), For beam With beam of light The absolute value of the optical path difference between them. To generate a beam The reflectivity of the corresponding layer To generate a beam The reflectivity of the corresponding layer For cross loss, For beam The corresponding refractive index of the waveguide structure, For beam The corresponding refractive index of the waveguide structure, For beam Geometric length of propagation For beam Geometric length of propagation The wavelength of light;

[0071] Based on the above Beam interference model The relationship between the interference intensity and wavelength is obtained by solving the problem. The theoretical interference spectrum with the interference intensity as the vertical axis and the wavelength as the horizontal axis is plotted. The theoretical interference spectrum is subjected to Fourier transform to obtain the theoretical time-domain spectrum. The interference spectrum obtained by spectrometer (13) is subjected to Fourier transform to obtain the time-domain spectrum. The time-domain spectrum is calibrated using the theoretical time-domain spectrum to obtain the calibrated time-domain spectrum.

[0072] When performing resonance peak-to-peak analysis on the time-domain spectrum, the resonance peak-to-peak analysis is performed based on the calibrated time-domain spectrum.

[0073] As an example, because the Beam interference model The independent variables include wavelength Therefore, the interference model of the beam light is used to calculate the interference model of the beam light As an example, assuming that the original light source intensity is 1, the interference model of the beam light has a value of wavelength corresponding to the interference intensity, and the interference intensity changes with the wavelength by substituting the value of wavelength in the expression of the interference model of the beam light .

[0074] As an example, according to the structure of the anti-resonant hollow core fiber, each nested tube is a silicon-air interface, and the air layer in the middle forms an FP cavity structure. When the light beam is normally incident, the reflected light meets the four conditions for interference. For an anti-resonant hollow core fiber with a structure of layer nested tube, the interference spectrum of the reflected light can be derived from the interference model of the beam light.

[0075] As an example, including reflectivity and transmission loss in the formula not only quantifies the effect of each reflection and transmission loss on the overall reflection spectrum, but also is consistent with actual measurement. Moreover, when calculating the structure parameters, the shape and intensity of the interference spectrum are directly affected by the reflectivity and transmission loss, which determine the amplitude and phase of the reflected light interference spectrum and the clarity and contrast of the frequency spectrum, thereby affecting the accuracy and accuracy of the time coordinate value obtained by Fourier transforming the interference fringes, and higher spectral contrast improves the accuracy of peak analysis.

[0076] In an optional embodiment, the expression of the cross-loss term includes:

[0077]

[0078] In the formula, the is the cavity loss.

[0079] In an optional embodiment, when the to-be-measured hollow core fiber 15 is an layer nested anti-resonant hollow core fiber, the steps of the detection method are performed to obtain the cladding thickness of the layer nested anti-resonant hollow core fiber and the size structure parameters of the corresponding nested tube at the irradiation position of the layer nested anti-resonant hollow core fiber;

[0080] The to-be-measured hollow core fiber 15 is rotated by a preset angle by the rotary displacement table 14, and the steps of the measurement method are repeated to obtain the size structure parameters of the corresponding nested tube at the irradiation position of the The size structure parameters of the nested tube at the irradiated position of the layer-nested anti-resonant hollow core fiber, and the preset angle is based on The total ring number of the nested tube of the layer-nested anti-resonant hollow core fiber is set;

[0081] The step of rotating the to-be-measured hollow core fiber 15 by a preset angle through the rotary displacement table 14 is repeated, and the step of the measurement method is repeatedly executed until the to-be-measured hollow core fiber 15 has been rotated for one revolution, and the repetition is stopped, and the The size structure parameters of the cladding and all the nested tubes of the layer-nested anti-resonant hollow core fiber.

[0082] As an exemplary illustration, after each rotation of the to-be-measured hollow core fiber 15 by a preset angle, the following can be measured simultaneously: The cladding thickness at the irradiated position of the layer-nested anti-resonant hollow core fiber, and the cladding thickness obtained through multiple measurements is averaged subsequently, which can eliminate the error of single measurement, so as to obtain a more accurate cladding thickness measurement result.

[0083] It can be understood that the detection method of the embodiment is based on the detection device of the above-mentioned embodiment 1, and the optional items of the above-mentioned embodiment 1 are also applicable to the embodiment, and therefore will not be repeatedly described here.

[0084] Embodiment 3

[0085] The embodiment is based on the measurement device of the size structure parameters of the hollow core fiber proposed in the embodiment 1 and the measurement method of the measurement device of the size structure parameters of the hollow core fiber proposed in the embodiment 2, and proposes a specific implementation example.

[0086] The basic principle of the double-layer nested anti-resonant hollow core fiber is based on the reflection and interference effect of light. The light wave is reflected between different nested layers of the hollow core fiber multiple times, forming a series of interference effects, and finally causing the light of a specific wavelength to be reflected back to the core region instead of entering the cladding. Therefore, each nested tube can be regarded as a FP cavity structure formed by the silicon-air interface and the intermediate air layer. The present application measures the size structure parameters of the hollow core fiber based on the principle of the FP cavity.

[0087] Figure 4 The structure diagram of the five-ring double-layer nested anti-resonant hollow core fiber proposed in the embodiment.

[0088] Taking the measurement of a five-ring double-layer nested tube anti-resonant hollow core fiber as an example, the present patent provides a specific implementation example of measuring the size structure parameters of the five-ring double-layer nested tube anti-resonant hollow core fiber based on the FP cavity multi-beam interference model. The structure of the to-be-measured fiber is as follows: Figure 4The structure parameters to be measured of the fiber are confirmed by cutting the anti-resonance hollow core fiber to be measured and observing the end face before measurement, and the three structure size parameters tested in the embodiment are the cladding thickness, the first layer nested tube diameter, the difference between the second layer nested tube and the first layer nested tube diameter, and the cladding thickness , , is the cladding thickness, the first layer nested tube diameter, the difference between the second layer nested tube and the first layer nested tube diameter, and the cladding thickness is , the first layer nested tube diameter is , the difference between the second layer nested tube and the first layer nested tube diameter is . The experimental device for measuring the size structure parameters of the five-ring double-nested anti-resonance hollow core fiber based on the FP cavity multi-beam interference model is shown in Figure 1 .

[0089] First, a wide-spectrum light source is used at the emission end of the light source, the wavelength range of the light source is , and the output power is connected to port 1 (the first port) of the optical circulator through a fiber joint.

[0090] The single-mode jumper is connected to port 2 (the second port) of the optical circulator to output the light beam of the light source, and the anti-resonance hollow core fiber to be measured with the coating layer removed is fixed through the rotary displacement table, and the single-mode fiber is adjusted to be aligned with the center of the fiber to be measured from the side.

[0091] Port 3 (the third port) of the optical circulator is connected to the spectrometer to collect the reflected light interference spectrum, and the fiber to be measured is rotated, and when the incident light beam is at the center horizontal line of the nested tube, that is, the normal incidence, the principle diagram of the interference of the different propagation paths of the reflected light when the five-ring double-nested anti-resonance hollow core fiber is measured is shown in Figure 5 , Figure 5 , wherein , , are the cladding thickness, the first layer nested tube diameter, the difference between the second layer nested tube and the first layer nested tube diameter, and the cladding thickness, which are the three structure size parameters tested in the embodiment. Based on the interference model of the beam light , the multi-beam reflected light beam interference spectrum is simulated, wherein the of the five-ring double-nested anti-resonance hollow core fiber is obtained, and the four-beam interference simulation spectrum (theoretical interference spectrum) is obtained , Figure 6 is the four-reflected light beam interference spectrum diagram proposed in the embodiment, and the simulation result is shown in Figure 6 .

[0092] Performing a Fourier transform on the interference spectrum yields the time-domain information of the interference spectrum. Figure 7 The simulation results are as follows: (This refers to the time-domain spectrum of the four-reflection beam interference proposed in this embodiment.) Figure 7 As shown, a Fourier transform is performed on the interference spectrum to obtain its time-domain information. Figure 6 The simulation results are as follows: (This refers to the time-domain spectrum of the four-reflection beam interference proposed in this embodiment.) Figure 6 As shown, the actual time-domain spectrum is obtained by Fourier transforming the interference spectrum obtained using spectrometer 13. The actual time-domain spectrum is then calibrated using the simulated time-domain spectrum interferometric time-domain spectrum to obtain the calibrated time-domain spectrum. Peak value analysis is performed on the six resonance peaks of the calibrated time-domain spectrum to extract the correspondence between each resonance peak and the size and structural parameters of the hollow fiber 15 under test.

[0093] By analyzing the multi-beam interference model based on the FP cavity and the corresponding relationship, multiple dimensional parameters of the optical fiber under test are obtained, enabling online monitoring of various structural parameters of the anti-resonant hollow optical fiber.

[0094] Since the different optical path differences during four-beam interference produce six interference components, then, , , , , , Because this embodiment uses a five-ring double-layer nested tube anti-resonant hollow fiber... The value range is 1.44-1.46. It is easy to know In the interference spectrum, the six interference components correspond to six resonance peaks. By performing a wavelength-frequency-time delay transformation on the horizontal axis, the Fourier transform result is obtained on the time axis, as shown below. Figure 7 As shown; therefore Figure 7 The optical path differences corresponding to the six resonance peaks from left to right are as follows: , , , , , We can obtain the optical path difference corresponding to each resonance peak, and thus we have:

[0095]

[0096]

[0097]

[0098] Among them, refractive index The value is 1.44-1.46; the calculated cladding thickness is... for .

[0099] refractive index is 1; the first layer of nested tube diameter is calculated is .

[0100] refractive index is 1; the difference between the second layer of nested tube and the first layer of nested tube diameter is calculated is .

[0101] In the production of hollow core fiber, the error of the size parameters of the hollow core fiber made by the drawing process and the size parameters of the hollow core fiber that is finally desired to be drawn is within a certain range, even the value of the of the multi-layer nested anti-resonant hollow core fiber is large, and the values are not equal, in the peak analysis process, the value of is equal to the value of the target plus or minus a preset error value, forming the estimated value range of the current measured , and other structural parameters are the same, in the peak analysis process, the estimated value range of each structural parameter is calculated, and the corresponding relationship between the resonance peak and the optical path difference can also be obtained.

[0102] It should be noted that the embodiment provides a measurement example of measuring the size and structural parameters of the five-ring double-layer nested tube anti-resonant hollow core fiber based on the FP cavity multi-beam interference model, but because the FP cavity multi-beam interference model is used to measure the structure of each single-ring nested tube, and the structure parameters of each ring of the anti-resonant hollow core fiber can be monitored online by rotating the rotary displacement table for one revolution, therefore, the patent does not limit the number of nested tube rings of the anti-resonant hollow core fiber structure to be measured.

[0103] The same or similar reference signs correspond to the same or similar components;

[0104] The terms used to describe the positional relationship in the drawings are only used for illustrative description, and cannot be understood as a limitation on the patent;

[0105] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not a limitation on the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A measurement method of a measurement device for measuring a size structure parameter of a hollow core optical fiber, characterized by, The device for measuring the size structure parameters of the hollow core fiber comprises a light source emitting end (11), an optical circulator (12), a spectrometer (13) and a rotary displacement table (14); The light source emitting end (11) is connected with a first port (1) of the optical circulator (12), a second port (2) of the optical circulator (12) is aligned with the side of the hollow core fiber (15) to be measured with the coating layer stripped, the hollow core fiber (15) to be measured with the coating layer stripped is placed in the rotary displacement table (14), and a third port (3) of the optical circulator (12) is connected with the spectrometer (13); The to-be-tested hollow core optical fiber (15) is a bandgap hollow core optical fiber or Layer nested anti-resonant hollow core optical fiber, wherein, is a positive integer; The light source emitted by the light source emitting end (11) is a wide-spectrum light source. The measuring method comprises the following steps: The light source emitting end (11) emits a light beam, the light beam is transmitted to the second port (2) of the optical circulator (12) through the first port (1) of the optical circulator (12), the hollow core fiber (15) to be measured is rotated through the rotary displacement table (14), so that the light beam emitted from the second port (2) of the optical circulator (12) is normally incident on the side of the hollow core fiber (15) to be measured with the coating layer stripped, the side of the hollow core fiber (15) to be measured reflects reflected light, and the reflected light is received by the spectrometer (13) after being transmitted to the third port (3) of the optical circulator (12) through the second port (2) of the optical circulator (12); The interference spectrum of the reflected light is obtained by using the spectrometer (13); The time-domain spectrum of the interference spectrum is obtained by performing Fourier transform on the interference spectrum, resonance peak value analysis is performed on the time-domain spectrum, the correspondence between the size structure parameters of the hollow core fiber (15) to be measured and each resonance peak of the time-domain spectrum is determined based on the resonance peak value analysis result; Based on the correspondence and the time information of the resonance peak, the size structure parameters of the hollow core fiber (15) to be measured are calculated; The step of determining the correspondence between the size structure parameters of the hollow core fiber (15) to be measured and each resonance peak of the time-domain spectrum based on the resonance peak value analysis result comprises: determining a total number of beams of the reflected light based on a structure of the hollow core optical fiber (15) to be measured , expression of the total number of beams includes: In the formula, is an integer greater than or equal to 0, when represents that the to-be-tested hollow core optical fiber (15) is a bandgap hollow core optical fiber; when is a positive integer, represents that the to-be-tested hollow core optical fiber (15) is a layer nested anti-resonance hollow core optical fiber; based on the total number of light beams determining a total number of resonance peaks of the time-domain spectrum , the total number of resonance peaks the expression of which comprises: the absolute value of the optical path difference between the first beam of light and the second beam of light is wherein and , the total number of ; When the to-be-tested hollow core optical fiber (15) is a bandgap hollow core optical fiber, wherein, represents the thickness of the first layer structure of the to-be-tested hollow core optical fiber (15) counted from outside to inside, i.e. the thickness of the cladding, represents the refractive index of the corresponding structure; When the hollow core optical fiber (15) to be measured is layer nested anti-resonant hollow core optical fiber, and , including , and wherein, , , , represents the diameter of the second layer structure of the hollow core optical fiber (15) to be measured from outside to inside, that is, the diameter of the first layer nested tube; represents the refractive index of the corresponding nested tube; When the to-be-tested hollow core optical fiber (15) is a layer-nested anti-resonant hollow core optical fiber, and if , then , if , then , wherein, Dn represents the difference between the diameter of the nth layer structure and the diameter of the (n+1)th layer structure of the to-be-tested hollow core optical fiber (15) counted from the outside to the inside; Dn represents the difference between the diameter of the nth layer structure and the diameter of the (n+1)th layer structure of the to-be-tested hollow core optical fiber (15) counted from the outside to the inside; Dn represents the difference between the diameter of the nth layer structure and the diameter of the (n+1)th layer structure of the to-be-tested hollow core optical fiber (15) counted from the outside to the inside; Dn represents the difference between the diameter of the nth layer structure and the diameter of the (n+1)th layer structure of the to-be-tested hollow core optical fiber (15) counted from the outside to the inside; Dn represents the difference between the diameter of the nth layer structure and the diameter According to the structure of the to-be-tested hollow optical fiber (15) In descending order of numerical values; Performing resonance peak peak value analysis on the time domain spectrum, obtaining peak values of resonance peaks, sorting the peak values in descending order according to the values, and the resonance peak corresponding to the peak value of the first largest is the resonance peak corresponding to the peak value of the first largest, wherein is a positive integer and ;​​ The expression of the size structure parameters of the hollow core fiber (15) to be measured comprises: In the formula, denotes the time coordinate value of the corresponding resonance peak, denotes the time coordinate value of the corresponding resonance peak.

2. The measurement method of the device for measuring the size structure parameters of the hollow core optical fiber according to claim 1, characterized in that, The second port (2) of the optical circulator (12) is connected with the side of the hollow core fiber (15) to be measured with the coating layer stripped after being connected with a single-mode jumper.

3. The measurement method of the hollow-core fiber size structure parameter measurement apparatus according to claim 1, characterized by, The light source emitting end (11) is connected with the first port (1) of the optical circulator (12) through a fiber joint.

4. The measurement method of the hollow-core fiber size structure parameter measuring apparatus according to any one of claims 1 to 3, characterized by, Before performing a resonance peak analysis on the time domain spectrum, a interference model of the beam light, the interference model of the beam light expression includes: In the formula, , , , and Consider it as 0. The reflectivity of the outer wall of the cladding of the optical fiber under test is given. The transmission loss is the outer wall of the cladding of the optical fiber under test. The reflectivity is the surface area at the contact between the inner wall of the cladding and the nested tube structure. This refers to the transmission loss at the interface between the inner wall of the cladding and the nested tube structure. For the first The reflectivity of nested tubes , For the first The reflectivity of nested tubes , For the first Transmission loss of nested tubes , For beam With beam of light The absolute value of the optical path difference between them. To generate a beam The reflectivity of the corresponding layer To generate a beam The reflectivity of the corresponding layer For cross loss, For beam The corresponding refractive index of the waveguide structure, For beam The corresponding refractive index of the waveguide structure, For beam Geometric length of propagation For beam The geometric length of the propagation The wavelength of light; based on the Interference model of beam The wavelength change relationship of the obtained interference intensity is solved, the theoretical interference spectrum with the longitudinal coordinate as the interference intensity and the transverse coordinate as the wavelength is drawn, the theoretical time domain spectrum is obtained by Fourier transforming the theoretical interference spectrum, the time domain spectrum is obtained by Fourier transforming the interference spectrum obtained by the spectrometer (13), the time domain spectrum is calibrated by using the theoretical time domain spectrum, and the calibrated time domain spectrum is obtained; When the resonance peak value analysis is performed on the time-domain spectrum, the resonance peak value analysis is performed based on the calibrated time-domain spectrum.

5. The measurement method of the hollow-core fiber size structure parameter measurement apparatus according to claim 4, characterized by, The cross-loss term The expression of the cross-loss term includes: In the formula, For the cavity loss.

6. The measurement method of the hollow-core fiber size structure parameter measuring apparatus according to any one of claims 1 to 3, characterized by, When the air-core optical fiber (15) to be measured is a layer-nested anti-resonant hollow-core optical fiber The steps of the measurement method are performed to obtain the cladding thickness and the size structure parameters of the corresponding nested tube at the irradiated position of the layer-nested anti-resonant hollow-core optical fiber The steps of the measurement method are performed to obtain the cladding thickness and the size structure parameters of the corresponding nested tube at the irradiated position of the layer-nested anti-resonant hollow-core optical fiber The steps of the measurement method are performed to obtain the cladding thickness and the size structure parameters of the corresponding nested tube at the irradiated position of the layer-nested anti-resonant hollow-core optical fiber The measurement method is repeated to obtain the measurement result of the air-core optical fiber (15) after rotating a preset angle The size structure parameters of the nested tube at the irradiated position of the layer-nested anti-resonant hollow-core optical fiber, and the preset angle is based on The total ring number of the nested tube of the layer-nested anti-resonant hollow-core optical fiber is set; The step of rotating the to-be-tested hollow core optical fiber (15) by a preset angle through the rotary displacement table (14) is repeated, and the step of the measurement method is repeatedly executed until the to-be-tested hollow core optical fiber (15) has been rotated for one circle, and the repetition is stopped, to obtain The size structure parameters of the cladding of the layer-nested anti-resonant hollow core optical fiber and all nested tubes.

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