A ring-shaped small-period long-period fiber grating sensor and its preparation method and application

Abstract

The present invention provides a ring-shaped small-period long-period fiber grating sensor and a preparation method and application thereof, which belongs to the field of optical fiber sensing technology. The ring-shaped small-period long-period fiber grating described in the present invention matches the shape of the optical fiber cross section, and 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 observed simultaneously in its transmission spectrum, and the simultaneous measurement of the refractive index and temperature of the surrounding environment can be achieved, and there is no need to observe the reflection peak, which simplifies the multi-parameter sensing test steps of the small-period long-period fiber grating.

Description

Technical Field

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

[0002] Fiber Bragg grating sensors have the advantages of small size, high sensitivity, corrosion resistance, and resistance to electromagnetic interference. They are widely used in aerospace, food safety, biomedicine and other fields. Fiber Bragg grating and long-period fiber grating are the two mainstream fiber grating sensors. The period of fiber Bragg grating is usually less than 1 micron, which can reverse couple the core mode and is mainly used in temperature and strain sensing. The period of long-period fiber grating is generally between tens and hundreds of microns. It can couple the core fundamental mode to the cladding mode, so it can sense the external environment outside the cladding and can be used in fields such as biochemical molecular sensing.

[0003] Currently, there are reports of long-period fiber gratings with a period of tens of microns. The characteristic of this grating is that it has both the Bragg reflection peak and the resonance peak of the cladding mode, so it can realize multi-parameter sensing. However, the current preparation method of long-period fiber gratings with a small period is limited to the horizontal line-by-line writing method. Although this preparation method is simple, its Bragg resonance peak is often too weak to be observed in the transmission spectrum. Therefore, when using it for multi-parameter sensing, it is necessary to obtain its reflection spectrum and transmission spectrum at the same time, which increases the complexity of the detection steps. Summary of the invention

[0004] The purpose of the present invention is to provide a circular ring-shaped 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 the cladding mode resonance peak in the transmission spectrum, simplifying the subsequent multi-parameter sensing signal extraction steps.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a ring-shaped small-period long-period fiber 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.

[0007] The refractive index modulation unit is formed by laser action.

[0008] 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%.

[0009] Preferably, the optical fiber is a single-mode optical fiber; and the laser is a femtosecond laser.

[0010] 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.

[0011] 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:

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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:

[0016] activating the annular small-period long-period fiber grating sensor in an acid solution or an alkaline solution to obtain a hydroxylated optical fiber;

[0017] The hydroxylated optical fiber is mixed with a silane organic substance having a terminal amino group and a mixed solvent to perform amination to obtain an amination optical fiber;

[0018] 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;

[0019] The gold nano-modified optical fiber is mixed with a 11-mercaptoundecanoic acid solution to perform carboxylation to obtain a carboxylated gold nano-modified optical fiber;

[0020] 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.

[0021] Preferably, the silane organic matter 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.

[0022] Preferably, 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 antibodyization temperature is 0-10° C., and the time is 8 hours.

[0023] The present invention provides a ring-shaped small-period long-period fiber grating sensor, which is composed of an optical fiber, wherein the fiber core of the optical fiber has a refractive index modulation unit periodically distributed along the axial direction of the fiber core, and the refractive index modulation unit of each period is composed of a plurality of rings arranged in series, each ring is perpendicular to the fiber core axis, and the ring core of each ring coincides with the center of the fiber core. The ring-shaped small-period long-period fiber grating of the present invention matches the cross-sectional shape of the optical fiber, and the ring can more effectively expand the area of ​​the refractive index modulation region in the cross-sectional area of ​​the optical fiber, so that the ring grating has a large refractive index modulation region in both the axial direction and the longitudinal direction 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 observed simultaneously in its transmission spectrum, and the simultaneous measurement of the refractive index and temperature of the surrounding environment can be realized, and there is no need to observe the reflection peak, which simplifies the multi-parameter sensing test steps of the small-period long-period fiber grating.

[0024] Compared with the prior art, the annular small-period long-period fiber grating sensor provided by the present invention has the following advantages:

[0025] 1) The fiber grating is processed by femtosecond laser to ensure the integrity of the optical fiber. When used in sensors, its robustness and ability to resist interference from harsh external environments are guaranteed;

[0026] 2) Simple processing, high flexibility, high repeatability, and compact structure of the prepared device;

[0027] 3) It can be used for multi-parameter sensing at the same time, such as temperature and biochemical molecule detection.

[0028] 4) Most of the existing gratings are written line by line along the core. In the present invention, the fiber grating is centered on the core and a ring is written along the axial direction of the 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 core, and also has a modulation area in the direction perpendicular to the 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

[0029] Figure 1 A schematic diagram of the structure of the annular small-period long-period fiber grating prepared by the present invention and a schematic diagram of its spectrum coupling;

[0030] Figure 2 It is a schematic diagram of the biological modification process of the circular small-period long-period fiber grating of the present invention;

[0031] Figure 3 is a schematic diagram of a biomolecule testing device of the present invention;

[0032] Figure 4 The temperature sensing result diagram of the annular small-period long-period fiber grating sensor of the present invention; wherein (a) is the curve of the Bragg resonance peak and the cladding mode resonance peak in the transmission spectrum at different temperatures, (b) is the linear relationship curve of the wavelength drift of the Bragg resonance peak and the cladding mode resonance peak with temperature; (c) is the curve of the Bragg resonance peak with temperature; (d) is the curve of the cladding mode resonance peak with temperature;

[0033] Figure 5 The diagram is a refractive index sensing result diagram of the circular ring-shaped small-period long-period fiber 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 change;

[0034] Figure 6 The results of measuring carcinoembryonic antigen (CEA) by the annular small-period long-period fiber grating sensor of the present invention are shown; (a) is a curve showing the change of the cladding mode resonance peak in the transmission spectrum with time when the CEA concentration is 10 ng / mL, and (b) is a local enlarged view of the curve (a); (c) is a curve showing the change 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 the curve (c). DETAILED DESCRIPTION

[0035] like Figure 1 As shown, the present invention provides a ring-shaped small-period long-period fiber grating sensor, which is composed of an optical fiber, wherein the core of the optical fiber has a refractive index modulation unit periodically distributed along the axial direction of the core, and 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.

[0036] The refractive index modulation unit is formed by laser action.

[0037] 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.

[0038] 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%, and more preferably 5%.

[0039] In the present invention, the optical fiber is preferably a single-mode optical fiber; and the laser is preferably a femtosecond laser.

[0040] In the present invention, the diameter of the ring is preferably 1-10 μm, more preferably 6 μm, the number of rings in each refractive index modulation unit is preferably 1-10, more preferably 4, the distance between the rings in each refractive index modulation unit is preferably 0.1-2 μm, more preferably 0.5 μm, the distance between adjacent refractive index modulation units is preferably 10-80 μm, more preferably 30 μm, and the number of the refractive index modulation units is preferably 50-200, more preferably 100.

[0041] 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:

[0042] 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.

[0043] The present invention preferably fixes the optical fiber on a three-dimensional moving platform so that the femtosecond laser can be vertically incident into 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 ring-shaped small-period long-period fiber grating is prepared inside the fiber core according to a specific duty cycle.

[0044] The present invention focuses the laser on the core of the optical fiber, and adjusts the refractive index modulation area and shape by moving the displacement platform. The present invention has no special restrictions on the process of setting the displacement platform parameters, and it is sufficient to ensure that the laser is vertically incident on the inside of the fiber core according to the process well known in the art.

[0045] In the present invention, the conditions of the laser 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.

[0046] 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.

[0047] 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:

[0048] activating the annular small-period long-period fiber grating sensor in an acid solution or an alkaline solution to obtain a hydroxylated optical fiber;

[0049] The hydroxylated optical fiber is mixed with a silane organic substance having a terminal amino group and a mixed solvent to perform amination to obtain an amination optical fiber;

[0050] 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;

[0051] The gold nano-modified optical fiber is mixed with a 11-mercaptoundecanoic acid solution to perform carboxylation to obtain a carboxylated gold nano-modified optical fiber;

[0052] 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.

[0053] 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 the acid solution is used, the activation temperature is preferably 20 to 80°C, and the activation time is preferably 0.5 to 3h.

[0054] In the present invention, the alkaline solution is preferably a sodium hydroxide aqueous solution, and the concentration of the alkaline solution is preferably 0.1-1 M, more preferably 0.2 M. When the alkaline solution is used, the activation temperature is preferably 20-50° C., and the activation time is preferably 1-4 h.

[0055] The present invention preferably treats the annular small-period long-period fiber grating sensor in an oxygen plasma cleaner first, and then immerses it 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.

[0056] The present invention cleans the optical fiber surface by acid solution or alkaline solution and activates the silanol groups on the optical fiber surface.

[0057] After the activation is completed, the residues on the surface of the optical fiber are washed with deionized water and then blown dry with N2.

[0058] In the present invention, the silane organic matter 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 matter 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%.

[0059] The present invention preferably immerses the hydroxylated fiber grating in a mixture of a silane organic compound with a terminal amino group and a mixed solvent; the amination temperature is preferably 20-40° C., more preferably 25° C.; and the time is preferably 8-12 hours.

[0060] After the amination is completed, the product is preferably washed with ethanol and dried with N2.

[0061] In the present invention, the preparation method of the gold nano-dispersion liquid is preferably: sodium citrate aqueous solution (75mL, 2.2mM), tannic acid aqueous solution (0.5μL, 2.5mM) and K2CO3 aqueous solution (0.5mL, 150mM) are mixed with reduced chloroauric acid aqueous solution (0.5mL, 25mM), and reduced at 100°C for 20min to obtain a gold nano-dispersion liquid; the concentration of the gold nano-dispersion liquid is preferably 0.01-0.1M, more preferably 0.02M.

[0062] The present invention preferably immerses the amino fiber grating in a gold nanoparticle dispersion; the loading temperature is preferably room temperature (25°C), the time is preferably 3 to 10 hours, and more preferably 8 hours. The present invention uses a charge attraction method to load gold nanoparticles on the optical fiber.

[0063] After the loading, the present invention preferably rinses the obtained product with deionized water and blows it dry with N2.

[0064] 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 3-8h, more preferably 5h.

[0065] After the carboxylation is completed, the product is preferably washed with anhydrous ethanol and dried with N2.

[0066] In the present invention, the protein antibody in the protein antibody solution preferably includes carcinoembryonic antigen antibody, alpha-fetoprotein antibody or virus 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.

[0067] 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 it in a protein antibody solution for antibodyization. The present invention has no particular limitation on the concentration of the mixed aqueous solution of EDC and NHS, and can be adjusted according to actual needs.

[0068] In the present invention, the temperature of antibodyization is preferably 0-10°C, more preferably 4°C, and the time is preferably 8h.

[0069] After the antibody is formed, the antibody that is not firmly loaded is preferably washed with deionized water and stored at 0-4°C.

[0070] 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.

[0071] 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 detection of immunoglobulins, streptavidin, viruses or bacteria.

[0072] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0073] Example 1

[0074] like Figure 1 As shown, the annular small-period long-period fiber Bragg grating sensor provided in this embodiment consists of 4 annular rings forming a refractive index modulation unit, the diameter of the annular ring is 6μm, the distance between different annular rings in a refractive index modulation unit is 0.5μm, the distance between adjacent refractive index modulation units is 30μm (referring to the distance between the last annular ring of the previous modulation unit and the first annular 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%.

[0075] Preparation method of circular small-period long-period fiber grating sensor:

[0076] 1) Fix the optical fiber on a three-dimensional moving platform so that the axial direction of the optical fiber is perpendicular to the incident direction of the laser beam; in order to offset the influence of the cylindrical shape of the optical fiber on the laser focusing, add refractive index matching oil between the lens and the optical fiber; observe and adjust the position of the optical fiber 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;

[0077] 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;

[0078] Among them, the wavelength of the femtosecond pulse laser is 520nm, the repetition frequency is 200kHz, and the energy is 60nJ.

[0079] Example 2

[0080] like Figure 2 As shown, the fiber biomodification is performed using carcinoembryonic antigen antibody as an example:

[0081] 1) Fiber hydroxylation: The fiber was treated in an oxygen plasma cleaning machine for 3 min, with a radio frequency power supply of 50 W, and the obtained fiber was immersed in a 0.2 M sodium hydroxide solution at 40 ° C for 3.5 h. The residue on the surface of the fiber was washed with deionized water and dried with N2;

[0082] 2) Optical fiber amination: The hydroxylated optical 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, washed with ethanol, and dried with N2.

[0083] 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 nano-dispersion (0.02 M); the amino-modified optical fiber obtained above was immersed in the gold nano-dispersion (10 mL, 0.02 M) at room temperature for 8 h, rinsed with deionized water, and blown dry with N2.

[0084] 4) Carboxylation of gold nanoparticles: The loaded gold optical fiber obtained in 3) above was immersed in 5 mL 0.5 mM 11-mercaptoundecanoic acid (MUA, ethanol solution) at 25° C. for 5 h, washed with anhydrous ethanol, and dried with N2 to obtain a carboxylated gold nanoparticle-modified optical fiber;

[0085] 5) Protein antibody modification: The carboxylated gold nanoparticle-modified optical fiber was treated in a mixed aqueous solution of 10 mL of LEDC (100 mM) and NHS (25 mM) for 10 min, and 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 antibodies were then washed with deionized water and placed in a refrigerator at 0-4°C for use to obtain a fiber optic biochemical sensor.

[0086] Example 3

[0087] Temperature sensing experiment

[0088] The annular small-period long-period fiber grating sensor of Example 1 was fixed in a temperature control box to prevent the fiber from shaking. The temperature control was adjusted. The transmission spectrum was recorded with 30°C as the starting temperature. The spectrum of 40-100°C was gradually recorded in increments of 10°C. The results are as follows: Figure 4 As shown, (a) is the curve of the Bragg resonance peak and the cladding mode resonance peak in the transmission spectrum at different temperatures, (b) is the linear relationship curve of the wavelength drift of the Bragg resonance peak and the cladding mode resonance peak with temperature; (c) is the curve of the Bragg resonance peak with temperature; (d) is the curve of the cladding mode resonance peak with temperature.

[0089] 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 image 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 10.14pm / ℃. At the same time, a similar phenomenon is observed in the local magnified image of the cladding mode resonance peak in (d). The similar temperature sensitivity obtained by fitting in (b) is 10.73pm / ℃.

[0090] Therefore, the Bragg resonance peak in the transmission spectrum of the present invention can be used to monitor the change of ambient temperature to prevent the temperature change from causing experimental interference to the refractive index sensing.

[0091] Example 4

[0092] Refractive index sensing experiment

[0093] like Figure 3 In the refractive index sensing device shown, the light source is connected to a fiber circulator, one output interface of the fiber circulator is connected to the small-period long-period fiber grating sensor described in Example 1, and the other interface of the sensor is connected to the spectrum analyzer; the sensing area of ​​the fiber grating sensor is placed in the detection groove, one end is attached to the track groove of the detection groove, and the other end is straightened under tension. Finally, the two ends of the sensor are fixed to the track groove with ultraviolet glue to prevent any stretching or vibration.

[0094] By adjusting the ratio of glycerol to water to prepare a solution with a refractive index between 1.333 and 1.410 (the refractive indices are 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 carried out on the small-period long-period fiber grating described in Example 1, and the volume of the solution added to the detection tank each time was 1 mL.

[0095] The results are as follows Figure 5As shown in the figure, (a) is the curve of the change of the cladding mode resonance peak in the transmission spectrum 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. It can be seen from the fitting curve of the relationship between the wavelength drift and the refractive index change in (b) that the refractive index sensitivity between 1.40-1.41 reaches 1479nm / RIU.

[0096] Example 5

[0097] Taking the detection of carcinoembryonic antigen (CEA) as an example, the experimental detection device uses Figure 3 The device shown;

[0098] 1) The detection process of CEA was carried out at 25°C. Based on the optical fiber biochemical sensor prepared in Example 2, the sensing area was fixed in the detection tank, 1 mL of PBS solution was added, and the spectrum was waited to stabilize. The position of the resonant wavelength at this time was recorded and used as the baseline spectrum (denoted as PBS-1, λ0).

[0099] 2) Remove the PBS solution in 1) from the detection tank, add 1 mL of PBS solution containing 10 ng / mL CEA, and record the spectrum every 10 minutes. After 60 minutes, the resonance wavelength position is stable, indicating that the antigen and antibody have reached a biochemical equilibrium state. After that, wash the sensing area with deionized water to remove the detection object physically bound to the surface.

[0100] 3) Place the rinsed sensing area in 1 mL of PBS solution until the spectrum reaches a stable state, which is used as the final spectrum (denoted as PBS-2, λ1). The difference between the baseline spectrum and the final spectrum (Δλ=λ1-λ0) is used as the wavelength shift corresponding to each concentration. The results are shown in Figure 6 As shown in (a) and (b), when the CEA concentration is 10 ng / mL, the wavelength of the spectrum red-shifts by 0.32 nm. At the same time, this calculation method effectively avoids the error caused by the volume refractive index in the experimental results. Figure 6 In the figure, PBS-1 and PBS-2 respectively 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 is completed;

[0101] 4) The 1ng / mL CEA test process is the same as above, and the results are as follows Figure 6 As shown in (c), (c) is the variation curve of the cladding mode resonance peak and time in the transmission spectrum when the CEA concentration is 1 ng / mL, and (d) is a local enlarged view of (c);

[0102] Depend on Figure 6As shown in (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), indicating that the sensor can detect 1 ng / mL, which is lower than the normal reference concentration of 5 ng / mL CEA, indicating that the CEA fiber Bragg grating sensor has certain practicality.

[0103] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A ring-shaped small-period long-period fiber grating sensor, characterized in that: The optical fiber is composed of an optical fiber, wherein the core of the optical fiber has a refractive index modulation unit periodically distributed along the axial direction of the core, and each period of the refractive index modulation unit is composed of a plurality of circular rings arranged in series, each circular ring 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; The refractive index modulation unit is periodically distributed along the axial direction of the fiber core according to a specific duty cycle; the specific duty cycle is 1-50%; The optical fiber is centered on the core and a circular ring is engraved along the axial direction of the core; The diameter of the ring is 1-10 μm, the number of rings in each refractive index modulation unit is 1-10, the distance between the rings in each refractive index modulation unit is 0.1-2 μm, the distance between adjacent refractive index modulation units is 10-80 μm, and the number of the refractive index modulation units is 50-200.

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

3. The method for preparing the annular small-period long-period fiber grating sensor according to any one of claims 1 to 2, 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.

4. The preparation method according to claim 3, characterized in that: The conditions of the laser include: a femtosecond pulse laser wavelength of 520 nm, a repetition frequency of 100-200 kHz, and an energy of 10-200 nJ.

5. Application of the annular small-period long-period fiber grating sensor according to any one of claims 1 to 2 or the annular small-period long-period fiber grating sensor prepared by the preparation method according to any one of claims 3 to 4 in optical fiber biochemical sensors or temperature sensors.

6. The use according to claim 5, characterized in that: When the annular small-period long-period fiber grating sensor is used for an optical fiber biochemical sensor, the preparation method of the optical fiber biochemical sensor comprises: 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 substance 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; The gold nano-modified optical fiber is mixed with a 11-mercaptoundecanoic acid solution to perform carboxylation to obtain a carboxylated gold nano-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.

7. The use according to claim 6, characterized in that: The silane organic matter 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.

8. The use according to claim 6, 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 antibodyization temperature is 0-10° C., and the time is 8 hours.

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