Ring-type small-period long-period fiber grating sensor, and preparation method therefor and application thereof

Abstract

The present invention belongs to the technical field of optical fiber sensing. Provided are a ring-type small-period long-period fiber grating sensor, and a preparation method therefor and the application thereof. A ring-type small-period long-period fiber grating provided in the present invention matches the cross-sectional shape of an optical fiber, and rings can more effectively expand the area of each refractive index modulation region in the cross section of the optical fiber, such that the ring-type grating has large refractive index modulation regions in both the axial direction and longitudinal direction of the optical fiber, and the intensities of a Bragg resonance peak and a cladding mode resonance peak can thus be simultaneously enhanced. Therefore, the Bragg resonance peak and the cladding mode resonance peak can be simultaneously observed in a transmission spectrum of the ring-type grating, such that simultaneous measurement of an ambient refractive index and temperature can be realized, and there is no longer a need to observe a reflection peak, thereby simplifying multi-parameter sensing test steps of the small-period long-period fiber grating.

Description

A circular small-period long-period fiber grating sensor and its preparation method and application Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to a ring-shaped small-period long-period optical fiber grating sensor and a preparation method and application thereof. Background Art

[0002] Fiber Bragg grating (FBG) sensors, with their advantages of small size, high sensitivity, corrosion resistance, and immunity to electromagnetic interference, are widely used in aerospace, food safety, biomedicine, and other fields. Fiber Bragg gratings (FBGs) and long-period fiber gratings (LPFGs) are currently the two most common fiber grating sensors. Fiber Bragg gratings (FBGs), typically with a period less than 1 micron, can reverse-couple the core mode and are primarily used in temperature and strain sensing. Long-period fiber gratings (LPFGs), with a period typically ranging from tens to hundreds of microns, can couple the core fundamental mode to the cladding mode, enabling sensing of the external environment. They are used in fields such as biochemical molecular sensing.

[0003] Currently, there have been reports of long-period fiber gratings (LPFBGs) with periods of tens of microns. These gratings are characterized by having both Bragg reflection peaks and cladding mode resonance peaks, enabling multi-parameter sensing. However, current methods for fabricating these LPFBGs are limited to horizontal line-by-line writing. While this method is simple, its Bragg resonance peaks are often too weak to be observed in the transmission spectrum. Therefore, multi-parameter sensing requires simultaneous acquisition of both the reflection and transmission spectra, increasing the complexity of the detection process.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a circular small-period long-period fiber grating sensor and its preparation method and application. The device has a compact structure, simple preparation, high refractive index sensitivity, and can simultaneously detect the Bragg resonance peak and cladding mode resonance peak in the transmission spectrum, simplifying the subsequent multi-parameter sensing signal extraction steps.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a ring-shaped small-period long-period fiber Bragg grating sensor, which is composed of an optical fiber. The core of the optical fiber has refractive index modulation units periodically distributed along the axial direction of the core. The refractive index modulation units of each period are composed of multiple rings arranged in series, each ring is perpendicular to the core axis, and the core of each ring coincides with the center of the core.

[0008] The refractive index modulation unit is formed by laser action.

[0009] Preferably, the refractive index modulation units are periodically distributed along the axial direction of the fiber core according to a specific duty cycle; the specific duty cycle is 1 to 50%.

[0010] Preferably, the optical fiber is a single-mode optical fiber; and the laser is a femtosecond laser.

[0011] Preferably, the diameter of the ring is 1 to 10 μm, the number of rings in each refractive index modulation unit is 1 to 10, the distance between the rings in each refractive index modulation unit is 0.1 to 2 μm, the distance between adjacent refractive index modulation units is 10 to 80 μm, and the number of the refractive index modulation units is 50 to 200.

[0012] The present invention provides a method for preparing the annular small-period long-period fiber grating sensor described in the above technical solution, comprising the following steps:

[0013] Focus the laser on the core of the optical fiber, set the laser and displacement platform parameters, and vertically inject the laser into the core to form a ring-shaped small-period long-period fiber grating sensor.

[0014] Preferably, the laser conditions include: a femtosecond pulse laser wavelength of 520 nm, a repetition frequency of 100 to 200 kHz, and an energy of 10 to 200 nJ.

[0015] The present invention provides the use of the annular small-period long-period fiber grating sensor described in the above technical solution or the annular small-period long-period fiber grating sensor prepared by the preparation method described in the above technical solution in an optical fiber biochemical sensor or a temperature sensor.

[0016] Preferably, when the annular small-period long-period fiber grating sensor is used in an optical fiber biochemical sensor, the preparation method of the optical fiber biochemical sensor includes:

[0017] activating the annular small-period long-period fiber grating sensor in an acid solution or an alkaline solution to obtain a hydroxylated optical fiber;

[0018] The hydroxylated optical fiber is mixed with a silane organic compound having a terminal amino group and a mixed solvent to perform amination to obtain an amination optical fiber;

[0019] The amino-modified optical fiber is mixed with a gold nanoparticle dispersion to load the optical fiber, thereby obtaining a gold nanoparticle-modified optical fiber;

[0020] mixing the gold nanoparticle-modified optical fiber with a 11-mercaptoundecanoic acid solution and performing carboxylation to obtain a carboxylated gold nanoparticle-modified optical fiber;

[0021] The carboxylated gold nano-modified optical fiber, protein antibody solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are mixed and antibody-formed to obtain an optical fiber biochemical sensor.

[0022] Preferably, the silane organic compound with terminal amino groups includes 3-aminopropyltriethoxysilane; the amination temperature is 20-40°C and the time is 8-12 hours; the loading temperature is room temperature and the time is 3-10 hours; the carboxylation temperature is 20-40°C and the time is 3-8 hours.

[0023] Preferably, the protein antibodies in the protein antibody solution include carcinoembryonic antigen antibodies, alpha-fetoprotein antibodies or viral antibodies, and the concentration of the protein antibody solution is 1-100 μg / mL; the antibodyization temperature is 0-10° C., and the time is 8 hours.

[0024] The present invention provides a ring-shaped small-period long-period fiber Bragg grating (FBG) sensor, which is composed of an optical fiber. The core of the optical fiber has refractive index modulation units periodically distributed along the axial direction of the core. The refractive index modulation units of each period are composed of multiple rings arranged in series, each ring is perpendicular to the core axis, and the ring core of each ring coincides with the center of the core. The ring-shaped small-period long-period fiber Bragg grating (FBG) of the present invention matches the cross-sectional shape of the optical fiber. The ring can more effectively expand the area of ​​the refractive index modulation region in the optical fiber cross-section, so that the ring grating has a large refractive index modulation region in both the axial and longitudinal directions of the optical fiber, thereby simultaneously enhancing the intensity of the Bragg resonance peak and the cladding mode resonance peak. Therefore, the Bragg resonance peak and the cladding mode resonance peak can be simultaneously observed in its transmission spectrum, which can achieve simultaneous measurement of the refractive index and temperature of the surrounding environment, eliminating the need to observe the reflection peak, thereby simplifying the multi-parameter sensing test steps of the small-period long-period fiber Bragg grating.

[0025] Compared with the prior art, the annular small-period long-period fiber grating sensor provided by the present invention has the following advantages:

[0026] 1) The fiber Bragg grating is processed using a femtosecond laser to ensure the integrity of the fiber. When used in sensors, it ensures its robustness and ability to resist interference from harsh external environments.

[0027] 2) Simple processing, high flexibility, high repeatability, and compact device structure;

[0028] 3) It can be used for multi-parameter sensing simultaneously, such as temperature and biochemical molecule detection.

[0029] 4) Most existing gratings are written line by line along the fiber core. In the present invention, the fiber grating is centered on the fiber core and a ring is written along the axial direction of the fiber core. The writing of multiple rings as a period makes the refractive index modulation area larger than that of line-by-line writing. The effect brought by the multi-ring grating written in the present invention is that it has a periodic modulation area with a small period in the axial direction of the fiber core, and also has a modulation area in the direction perpendicular to the fiber core. The combined effect of the two modulation areas in the horizontal and vertical directions makes it possible to simultaneously observe the Bragg resonance peak and the cladding mode resonance peak in the transmission spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of the structure of a circular small-period long-period fiber grating prepared by the present invention and a schematic diagram of its spectral coupling;

[0031] FIG2 is a schematic diagram of the biomodification process of the annular small-period long-period fiber grating of the present invention;

[0032] FIG3 is a schematic diagram of a biomolecule testing device according to the present invention;

[0033] FIG4 is a diagram showing the temperature sensing results of the annular small-period long-period fiber Bragg grating sensor of the present invention; wherein (a) is a curve showing the Bragg resonance peak and the cladding mode resonance peak in the transmission spectrum at different temperatures; (b) is a curve showing the linear relationship between the wavelength shift of the Bragg resonance peak and the cladding mode resonance peak with temperature; (c) is a curve showing the change of the Bragg resonance peak with temperature; and (d) is a curve showing the change of the cladding mode resonance peak with temperature.

[0034] FIG5 is a diagram showing the refractive index sensing results of the annular small-period long-period fiber Bragg grating sensor of the present invention; wherein (a) is a curve showing the change of the cladding mode resonance peak in the transmission spectrum with the external refractive index, and (b) is a curve showing the relationship between the resonance peak wavelength drift and the refractive index;

[0035] Figure 6 shows the results of measuring carcinoembryonic antigen (CEA) using the annular small-period long-period fiber Bragg grating sensor of the present invention; (a) is a curve showing the change of the cladding mode resonance peak in the transmission spectrum versus time when the CEA concentration is 10 ng / mL, and (b) is a partial enlarged view of the curve (a); (c) is a curve showing the change of the cladding mode resonance peak in the transmission spectrum versus time when the CEA concentration is 1 ng / mL, and (d) is a partial enlarged view of the curve (c). DETAILED DESCRIPTION

[0036] As shown in Figure 1, the present invention provides a circular small-period long-period fiber Bragg grating sensor, which is composed of an optical fiber. The core of the optical fiber has a refractive index modulation unit periodically distributed along the axial direction of the core. The refractive index modulation unit of each period is composed of a plurality of circular rings arranged in series, each of which is perpendicular to the core axis, and the core of each circular ring coincides with the center of the core.

[0037] The refractive index modulation unit is formed by laser action.

[0038] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0039] In the present invention, the refractive index modulation units are periodically distributed along the axial direction of the fiber core according to a specific duty cycle; the specific duty cycle is preferably 1 to 50%, more preferably 5%.

[0040] In the present invention, the optical fiber is preferably a single-mode optical fiber; the laser is preferably a femtosecond laser.

[0041] In the present invention, the diameter of the ring is preferably 1 to 10 μm, more preferably 6 μm, the number of rings in each refractive index modulation unit is preferably 1 to 10, more preferably 4, the distance between the rings in each refractive index modulation unit is preferably 0.1 to 2 μm, more preferably 0.5 μm, the distance between adjacent refractive index modulation units is preferably 10 to 80 μm, more preferably 30 μm, and the number of the refractive index modulation units is preferably 50 to 200, more preferably 100.

[0042] The present invention provides a method for preparing the annular small-period long-period fiber grating sensor described in the above technical solution, comprising the following steps:

[0043] Focus the laser on the core of the optical fiber, set the laser and displacement platform parameters, and vertically inject the laser into the core to form a ring-shaped small-period long-period fiber grating sensor.

[0044] The present invention preferably fixes the optical fiber on a three-dimensional movable platform so that the femtosecond laser can be vertically incident on the inside of the fiber core; adjusts the displacement platform so that the laser is focused on the fiber core; after setting the parameters of the femtosecond laser and the displacement platform, a circular small-period long-period fiber grating is prepared inside the fiber core according to a specific duty cycle.

[0045] The present invention focuses laser light onto the fiber core and adjusts the refractive index modulation region and shape through the movement of a displacement platform. The present invention does not specify the process for setting the displacement platform parameters; it suffices to ensure that the laser light is perpendicularly incident on the fiber core, following procedures well known in the art.

[0046] In the present invention, the laser conditions preferably include: a femtosecond pulse laser wavelength of 520 nm, a repetition frequency of 100 to 200 kHz, more preferably 200 kHz, and an energy of 10 to 200 nJ, more preferably 60 nJ.

[0047] The present invention provides the use of the annular small-period long-period fiber grating sensor described in the above technical solution or the annular small-period long-period fiber grating sensor prepared by the preparation method described in the above technical solution in an optical fiber biochemical sensor or a temperature sensor.

[0048] In the present invention, when the annular small-period long-period fiber grating sensor is used in an optical fiber biochemical sensor, the preparation method of the optical fiber biochemical sensor preferably includes:

[0049] activating the annular small-period long-period fiber grating sensor in an acid solution or an alkaline solution to obtain a hydroxylated optical fiber;

[0050] The hydroxylated optical fiber is mixed with a silane organic compound having a terminal amino group and a mixed solvent to perform amination to obtain an amination optical fiber;

[0051] The amino-modified optical fiber is mixed with a gold nanoparticle dispersion to load the optical fiber, thereby obtaining a gold nanoparticle-modified optical fiber;

[0052] mixing the gold nanoparticle-modified optical fiber with a 11-mercaptoundecanoic acid solution and performing carboxylation to obtain a carboxylated gold nanoparticle-modified optical fiber;

[0053] The carboxylated gold nano-modified optical fiber, protein antibody solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are mixed and antibody-formed to obtain an optical fiber biochemical sensor.

[0054] In the present invention, the acid solution is preferably a mixture of concentrated sulfuric acid and 30wt% hydrogen peroxide, and the volume ratio of the concentrated sulfuric acid to 30wt% hydrogen peroxide is preferably 1:1 to 3:1; when an acid solution is used, the activation temperature is preferably 20 to 80°C, and the activation time is preferably 0.5 to 3h.

[0055] In the present invention, the alkaline solution is preferably a sodium hydroxide aqueous solution, and the concentration of the alkaline solution is preferably 0.1 to 1 M, more preferably 0.2 M. When an alkaline solution is used, the activation temperature is preferably 20 to 50° C., and the activation time is preferably 1 to 4 hours.

[0056] In the present invention, the annular small-period long-period fiber grating sensor is preferably treated in an oxygen plasma cleaner and then immersed in an acid solution or an alkaline solution; the treatment time in the oxygen plasma cleaner is preferably 3 minutes, and the RF power supply is preferably 50W.

[0057] The present invention cleans the optical fiber surface through an acid solution or an alkaline solution and activates the silanol groups on the optical fiber surface.

[0058] After the activation is completed, the residue on the surface of the optical fiber is washed with deionized water and then blown dry with N2.

[0059] In the present invention, the silane organic compound with a terminal amino group preferably includes 3-aminopropyltriethoxysilane (APTES); the mixed solvent is preferably water and ethanol, wherein the total volume of the silane organic compound with a terminal amino group and the mixed solvent is 100%, the volume proportion of APTES is preferably 0.5-2%, more preferably 1%, the volume proportion of ethanol is preferably 0.5-2%, more preferably 1%, and the volume proportion of water is preferably 96-99%, more preferably 98%.

[0060] The present invention preferably immerses the hydroxylated fiber Bragg grating in a mixture of a silane organic compound with terminal amino groups and a mixed solvent; the amination temperature is preferably 20-40°C, more preferably 25°C; and the time is preferably 8-12 hours.

[0061] After the amination is completed, the product is preferably washed with ethanol and dried with N2.

[0062] In the present invention, the preparation method of the gold nano-dispersion is preferably: sodium citrate aqueous solution (75 mL, 2.2 mM), tannic acid aqueous solution (0.5 μL, 2.5 mM) and K2CO3 aqueous solution (0.5 mL, 150 mM) are mixed with reduced chloroauric acid aqueous solution (0.5 mL, 25 mM), and reduced at 100°C for 20 minutes to obtain a gold nano-dispersion; the concentration of the gold nano-dispersion is preferably 0.01 to 0.1 M, more preferably 0.02 M.

[0063] The present invention preferably immerses the amino-modified fiber Bragg grating in a gold nanoparticle dispersion; the loading temperature is preferably room temperature (25°C), and the time is preferably 3 to 10 hours, more preferably 8 hours. The present invention utilizes a charge attraction method to load gold nanoparticles onto the optical fiber.

[0064] After the loading, the present invention preferably rinses the obtained product with deionized water and blows it dry with N2.

[0065] In the present invention, the concentration of the 11-mercaptoundecanoic acid solution (MUA, ethanol solution) is preferably 0.1-1 mM, more preferably 0.5 mM; the present invention preferably immerses the gold nano-modified optical fiber in the 11-mercaptoundecanoic acid solution; the carboxylation temperature is preferably 20-40°C, and the time is preferably 3-8 hours, more preferably 5 hours.

[0066] After the carboxylation is completed, the product is preferably washed with anhydrous ethanol and dried with N2.

[0067] In the present invention, the protein antibody in the protein antibody solution preferably includes carcinoembryonic antigen antibody, alpha-fetoprotein antibody or viral antibody; the molar ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) is preferably 1:1 to 5:1, more preferably 4:1; the concentration of the protein antibody solution is preferably 1 to 100 μg / mL, more preferably 10 μg / mL, and the solvent used is preferably PBS phosphate buffer solution, pH = 7.4.

[0068] The present invention preferably treats the carboxylated gold nanoparticle-modified optical fiber in a mixed aqueous solution of EDC and NHS for 10 to 30 minutes, and then immerses the optical fiber in a protein antibody solution for antibodyization. The present invention does not specifically limit the concentration of the mixed aqueous solution of EDC and NHS, and can be adjusted according to actual needs.

[0069] In the present invention, the temperature for antibodyization is preferably 0-10°C, more preferably 4°C, and the time is preferably 8 hours.

[0070] After the antibody is formed, the antibody that is not firmly loaded is preferably washed with deionized water and stored at 0-4°C.

[0071] The present invention loads protein antibodies on gold nanoparticles to complete the antibodyization of optical fibers and endow the optical fibers with specific recognition functions.

[0072] The optical fiber biochemical sensor of the present invention is suitable for all types of molecular detection using protein antibodies as recognition bodies, such as the detection of immunoglobulins, streptavidin, viruses or bacteria.

[0073] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] As shown in FIG1 , the ring-shaped small-period long-period fiber Bragg grating sensor provided in this embodiment consists of four rings forming a refractive index modulation unit. The diameter of the ring is 6 μm, the distance between different rings in a refractive index modulation unit is 0.5 μm, and the distance between adjacent refractive index modulation units is 30 μm (referring to the distance between the last ring of the previous modulation unit and the first ring of the next modulation unit), with a total of 100 refractive index modulation units. The refractive index modulation units are periodically distributed along the axial direction of the fiber core with a duty cycle of 5%.

[0076] Preparation method of circular small-period long-period fiber grating sensor:

[0077] 1) An optical fiber is fixed on a three-dimensional moving platform so that the axis of the optical fiber is perpendicular to the incident direction of the laser beam. To offset the effect of the cylindrical shape of the optical fiber on laser focusing, refractive index matching oil is added between the lens and the optical fiber. The position of the optical fiber is observed and adjusted through a microscope so that the laser beam output by the laser is focused on the center of the optical fiber through a microscope objective lens (numerical aperture 1.4, 63x) and an adjustable aperture.

[0078] 2) After setting the parameters of the femtosecond laser and the displacement platform, a circular small-period long-period fiber grating is prepared inside the fiber core;

[0079] Among them, the wavelength of the femtosecond pulse laser is 520nm, the repetition frequency is 200kHz, and the energy is 60nJ.

[0080] Example 2

[0081] As shown in Figure 2, optical fiber biomodification is performed using carcinoembryonic antigen antibodies as an example:

[0082] 1) Fiber hydroxylation: The fiber was treated in an oxygen plasma cleaner for 3 minutes with a 50W RF power supply. The resulting fiber was then immersed in a 0.2M sodium hydroxide solution at 40°C for 3.5 hours. The residue on the fiber surface was washed with deionized water and dried with nitrogen.

[0083] 2) Fiber amination: The hydroxylated fiber was immersed in a 1% APTES (aminopropyltriethoxysilane) solution (volume ratio APTES: ethanol: water = 1:1:98), amination was performed at room temperature for 12 h, ethanol was washed, and N2 was blown dry.

[0084] 3) Gold nanoparticle loading: Sodium citrate aqueous solution (75 mL, 2.2 mM), tannic acid aqueous solution (0.5 μL, 2.5 mM) and K2CO3 aqueous solution (0.5 mL, 150 mM) were used to reduce chloroauric acid aqueous solution (0.5 mL, 25 mM) in a flask at 100°C for 20 min to obtain a gold nanoparticle dispersion (0.02 M). The amino-treated optical fiber obtained above was immersed in the gold nanoparticle dispersion (10 mL, 0.02 M) at room temperature for 8 h, rinsed with deionized water, and blown dry with N2.

[0085] 4) Carboxylation of gold nanoparticles: The loaded gold optical fiber obtained in 3) above was immersed in 5 mL of 0.5 mM 11-mercaptoundecanoic acid (MUA, ethanol solution) at 25°C for 5 h, washed with anhydrous ethanol, and dried with nitrogen to obtain a carboxylated gold nanoparticle-modified optical fiber;

[0086] 5) Protein antibody modification: The carboxylated gold nanoparticle-modified optical fiber was treated in a mixed aqueous solution of 10 mL of EDC (100 mM) and NHS (25 mM) for 10 min, then immersed in a 10 μg / mL carcinoembryonic antigen (CEA) antibody solution (PBS phosphate buffer solution, pH = 7.4) at 4°C for 8 h. The unloaded antibody was then washed with deionized water and placed in a refrigerator at 0-4°C for use to obtain a fiber optic biochemical sensor.

[0087] Example 3

[0088] Temperature sensing experiment

[0089] The annular small-period long-period fiber Bragg grating sensor of Example 1 was fixed in a temperature-controlled box to prevent the fiber from shaking. The temperature control was adjusted, and the transmission spectrum was recorded with a starting temperature of 30°C. The spectrum from 40°C to 100°C was gradually recorded in increments of 10°C. The results are shown in Figure 4, where (a) is a curve of the Bragg resonance peak and the cladding mode resonance peak in the transmission spectrum at different temperatures, (b) is a curve of the linear relationship between the wavelength drift of the Bragg resonance peak and the cladding mode resonance peak with temperature; (c) is a curve of the Bragg resonance peak with temperature; and (d) is a curve of the cladding mode resonance peak with temperature.

[0090] In the transmission spectrum shown in (a), the sharper one on the left is the Bragg resonance peak, and the one on the right is the cladding mode resonance peak. It can be clearly seen from the local magnified view of the Bragg resonance peak shown in (c) that the Bragg resonance peak gradually redshifts with increasing temperature. The temperature sensitivity obtained by linear fitting in (b) is 10.14 pm / ℃. At the same time, a similar phenomenon is also observed in the local magnified view of the cladding mode resonance peak in (d). The similar temperature sensitivity obtained by fitting in (b) is 10.73 pm / ℃.

[0091] Therefore, the Bragg resonance peak in the transmission spectrum of the present invention can be used to monitor changes in ambient temperature to prevent temperature changes from interfering with the refractive index sensing experiment.

[0092] Example 4

[0093] Refractive index sensing experiment

[0094] As shown in Figure 3, the refractive index sensing device has a light source connected to a fiber circulator. One output port of the fiber circulator is connected to the short-period long-period fiber Bragg grating sensor described in Example 1, and the other port of the sensor is connected to a spectrum analyzer. The sensing area of ​​the fiber Bragg grating sensor is placed in the detection tank, with one end attached to the track groove of the detection tank and the other end stretched under tension. Finally, the two ends of the sensor are fixed to the track groove with UV glue to prevent any stretching or vibration.

[0095] By adjusting the ratio of glycerol to water to prepare solutions with a refractive index between 1.333 and 1.410 (refractive indices were 1.333, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, and 1.41, respectively), a refractive index sensing experiment was performed on the small-period long-period fiber grating described in Example 1. The volume of the solution added to the detection tank each time was 1 mL.

[0096] The results are shown in Figure 5, where (a) is the curve of the cladding mode resonance peak in the transmission spectrum changing with the external refractive index, and (b) is the curve of the relationship between the resonance peak wavelength drift and the refractive index. As shown in (a), with the increase of the refractive index, the wavelength of the transmission spectrum gradually redshifts, while the Bragg resonance peak does not change with the refractive index. From the fitting curve of the relationship between the wavelength drift and the refractive index change in (b), it can be seen that the refractive index sensitivity between 1.40-1.41 reaches 1479nm / RIU.

[0097] Example 5

[0098] Taking the detection of carcinoembryonic antigen (CEA) as an example, the experimental detection device uses the device shown in Figure 3;

[0099] 1) CEA detection was performed at 25°C. The optical fiber biochemical sensor prepared in Example 2 was fixed in the detection tank. 1 mL of PBS solution was added and the spectrum was allowed to stabilize. The position of the resonant wavelength was recorded and used as the baseline spectrum (denoted as PBS-1, λ0).

[0100] 2) Remove the PBS solution from the detection chamber and add 1 mL of PBS solution containing 10 ng / mL CEA. Record spectra every 10 minutes. After 60 minutes, the resonant wavelength position stabilizes, indicating that the antigen-antibody relationship has reached biochemical equilibrium. Rinse the sensing area with deionized water to remove any physically bound analyte.

[0101] 3) The rinsed sensing area was placed in 1 mL of PBS solution, and the spectrum reached a stable state, which was used as the final spectrum (denoted as PBS-2, λ1). The difference between the baseline spectrum and the final spectrum (Δλ = λ1-λ0) was used as the wavelength shift corresponding to each concentration. The results are shown in Figure 6 (a) and (b). When the CEA concentration was 10 ng / mL, the wavelength of the spectrum was red-shifted by 0.32 nm. At the same time, this calculation method effectively avoided the error caused by the volume refractive index in the experimental results. In Figure 6, PBS-1 and PBS-2 represent the spectrum of the sensor in pure PBS solution before the test and the spectrum of the sensor in pure PBS solution after the CEA recognition was completed, respectively;

[0102] 4) The detection process of 1 ng / mL CEA is the same as above. The results are shown in Figure 6(c). (c) is the variation curve of the cladding mode resonance peak in the transmission spectrum with time when the CEA concentration is 1 ng / mL, and (d) is a local enlarged view of (c);

[0103] As shown in Figure 6 (c) and (d), when the CEA concentration is 1 ng / mL, the spectral wavelength shifts by 0.07 nm after the test, which is higher than the wavelength resolution (0.02 nm). This indicates that the sensor can detect 1 ng / mL, which is lower than the normal reference concentration of CEA of 5 ng / mL, indicating that the CEA fiber Bragg grating sensor has certain practicality.

[0104] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A circular small-period long-period fiber Bragg grating sensor, characterized in that: It is composed of an optical fiber, the core of which has refractive index modulation units periodically distributed along the core axis. The refractive index modulation units of each period are composed of multiple circular rings arranged in series, each of which is perpendicular to the core axis, and the core of each circular ring coincides with the center of the core. The refractive index modulation unit is formed by laser action.

2. The annular small-period long-period fiber Bragg grating sensor according to claim 1, characterized in that: The refractive index modulation units are periodically distributed along the axial direction of the fiber core according to a specific duty cycle; the specific duty cycle is 1 to 50%.

3. The annular small-period long-period fiber Bragg grating sensor according to claim 1, characterized in that: The optical fiber is a single-mode optical fiber; the laser is a femtosecond laser.

4. The annular small-period long-period fiber Bragg grating sensor according to claim 1, characterized in that: The diameter of the ring is 1 to 10 μm, the number of rings in each refractive index modulation unit is 1 to 10, the distance between the rings in each refractive index modulation unit is 0.1 to 2 μm, the distance between adjacent refractive index modulation units is 10 to 80 μm, and the number of the refractive index modulation units is 50 to 200.

5. The method for preparing the annular small-period long-period fiber grating sensor according to any one of claims 1 to 4, characterized in that: The following steps are involved: Focus the laser on the core of the optical fiber, set the laser and displacement platform parameters, and vertically inject the laser into the core to form a ring-shaped small-period long-period fiber grating sensor.

6. The preparation method according to claim 5, characterized in that The laser conditions include: a femtosecond pulse laser wavelength of 520 nm, a repetition frequency of 100 to 200 kHz, and an energy of 10 to 200 nJ.

7. Use of the annular small-period long-period fiber Bragg grating sensor according to any one of claims 1 to 4 or the annular small-period long-period fiber Bragg grating sensor prepared by the preparation method according to any one of claims 5 to 6 in an optical fiber biochemical sensor or temperature sensor.

8. The use according to claim 7, characterized in that When the annular small-period long-period fiber grating sensor is used in an optical fiber biochemical sensor, the preparation method of the optical fiber biochemical sensor includes: activating the annular small-period long-period fiber grating sensor in an acid solution or an alkaline solution to obtain a hydroxylated optical fiber; The hydroxylated optical fiber is mixed with a silane organic compound having a terminal amino group and a mixed solvent to perform amination to obtain an amination optical fiber; The amino-modified optical fiber is mixed with a gold nanoparticle dispersion to load the optical fiber, thereby obtaining a gold nanoparticle-modified optical fiber; mixing the gold nanoparticle-modified optical fiber with a 11-mercaptoundecanoic acid solution and performing carboxylation to obtain a carboxylated gold nanoparticle-modified optical fiber; The carboxylated gold nano-modified optical fiber, protein antibody solution, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are mixed and antibody-formed to obtain an optical fiber biochemical sensor.

9. The use according to claim 8, characterized in that The silane organic compound with terminal amino groups includes 3-aminopropyltriethoxysilane; the temperature of the amination is 20-40°C and the time is 8-12 hours; the temperature of the load is room temperature and the time is 3-10 hours; the temperature of the carboxylation is 20-40°C and the time is 3-8 hours.

10. The use according to claim 8, characterized in that The protein antibodies in the protein antibody solution include carcinoembryonic antigen antibodies, alpha-fetoprotein antibodies or virus antibodies, and the concentration of the protein antibody solution is 1-100 μg / mL; the antibody formation temperature is 0-10° C., and the time is 8 hours.

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