阅读说明：本技术 一种材料填充型中空光纤光栅及其制备方法 (Material filling type hollow fiber grating and preparation method thereof ) 是由 田凤军 刘光宇 姚晨宇 韩忠瑞 卢艺鹏 李立 张建中 于 2021-07-05 设计创作，主要内容包括：本发明提供一种材料填充型中空光纤光栅及其制备方法,该毛细管光纤光栅包括光纤环形包层、空气孔包层、光纤纤芯。空气孔包层与光纤纤芯距离小于3微米或直接接触。该光纤光栅的制备方法为：功能材料利用加压注射的方式对光纤空气孔包层进行填充。通过调节注射泵的推进速度、推进次数及间隔时间,功能材料在空气孔包层中周期性填充,从而使折射率呈周期性变化。最后对毛细管光纤进行熔融拉锥,将微流体通道封堵,实现毛细管光纤空气孔包层的长周期光栅阵列。本发明中所设计的材料填充型中空光纤光栅,具有低插入损耗、光纤纤芯无物理损伤、结构简单等优点,实现对不同波长光波的反射,可应用于光纤传感、生物医疗等多个领域。(The invention provides a material filling type hollow fiber grating and a preparation method thereof. The air hole cladding is less than 3 microns away from the fiber core or in direct contact with the fiber core. The preparation method of the fiber grating comprises the following steps: the functional material fills the optical fiber air hole cladding by means of pressurized injection. By adjusting the propelling speed, the propelling times and the interval time of the injection pump, the functional material is periodically filled in the air hole cladding, so that the refractive index is periodically changed. And finally, performing fusion tapering on the capillary optical fiber to plug the microfluidic channel, thereby realizing the long-period grating array of the capillary optical fiber air hole cladding. The material filling type hollow fiber grating designed by the invention has the advantages of low insertion loss, no physical damage to the fiber core of the optical fiber, simple structure and the like, realizes reflection of light waves with different wavelengths, and can be applied to a plurality of fields of optical fiber sensing, biological medical treatment and the like.)

1. A material filling type hollow fiber grating is characterized by comprising an optical fiber annular cladding (1), an air hole cladding (4) and an optical fiber core (3). The air hole cladding (4) is positioned in the center of the optical fiber annular cladding (1), the grating is positioned on the inner wall of the optical fiber annular cladding (1), the refractive index is periodically distributed along the length direction of the optical fiber, and the distance between the grating and the fiber core of the optical fiber is less than 3 microns or the grating is in direct contact with the fiber core of the optical fiber to form weak coupling.

2. The material-filled hollow fiber grating according to claim 1, wherein the optical fiber comprises an annular cladding, an air hole cladding and a core, and the core is disposed in the annular cladding or suspended from the inner wall of the annular cladding.

3. The material-filled hollow fiber grating according to claim 1, wherein the air holes of the capillary fiber are single, double or multiple holes.

4. A method for preparing a material-filled hollow fiber grating according to claim 1, comprising the steps of:

the method comprises the following steps: the capillary was heated and snapped off to form a tapered tip, approximately 2 microns in diameter. Aligning the capillary filled with the liquid functional material to the air hole cladding of the capillary optical fiber to be etched, and pressurizing the injector to fill the liquid functional material in the central air hole (4) of the capillary optical fiber;

step two: performing fusion tapering on one end of a capillary optical fiber to be engraved and written, and preparing a semi-closed cavity at one end of the optical fiber;

step three: fixing the semi-closed cavity prepared in the last step in an optical fiber fusion splicer, fixing an injector on an injection pump, and periodically filling the liquid functional material into an air hole cladding of the semi-closed cavity by adjusting the propelling speed, propelling times and interval time of the injector pump, so that the refractive index is periodically changed. The filling condition of the liquid functional material can be monitored in real time by monitoring a display screen of the welding machine;

step four: and finally, performing fusion tapering on the other ends of the two ends of the capillary optical fiber after the writing by using a fusion heating method, and plugging the microfluidic channel to realize the long-period grating array of the air hole cladding of the capillary optical fiber. The grating array is weakly coupled with the fiber core of the optical fiber, and the distance is less than 3 microns or is in direct contact with the fiber core of the optical fiber.

5. The method as claimed in claim 4, wherein the functional material is oil drop or other liquid functional material.

6. The method as claimed in claim 4, wherein the functional material is biological cells, and the periodic arrangement of the functional material forms a grating.

7. The method as claimed in claim 4, wherein the grating is formed in an air hole cladding of the capillary fiber.

8. The method as claimed in claim 4, wherein the functional material and the size of the bubbles are 50 μm.

9. The method as claimed in claim 4, wherein the grating array period is determined by the periodic distribution of the injected functional material.

10. The method as claimed in claim 4, wherein the functional material is filled by capillary siphon method.

Technical Field

The invention belongs to the technical field of fiber bragg gratings, and particularly relates to a material filling type hollow fiber bragg grating and a preparation method thereof.

Background

In recent years, rapid development of fiber gratings has attracted the attention of scientists. The principle of the fiber grating is that the photosensitivity of an optical material is utilized, so that the refractive index of the optical fiber is periodically modulated, and a one-dimensional periodic structure is formed. On the premise of meeting the phase matching, the fiber grating enables the resonant wavelength modes to be coupled to achieve wavelength selection. Fiber gratings can be classified into two types according to their period: fiber Bragg Gratings (FBGs) and Long Period Fiber Gratings (LPFGs). The period of the fiber Bragg grating is usually hundreds of nanometers, coupling occurs between a forward transmission mode and a reverse transmission mode in a fiber core, input light with specific wavelength can be reflected, and the fiber Bragg grating is a reflection-type grating which can be used as a narrow band-pass filter; the long-period fiber grating generally takes tens of microns to hundreds of microns as a period, coupling occurs between a core guided mode and a cladding mode of homodromous transmission in the optical fiber, and the long-period fiber grating is a transmission type grating and can be used as a transmission band-stop filter.

In recent years, fiber grating sensors have been rapidly developed because of their advantages such as small size, high measurement accuracy, and the ability to perform multi-parameter measurements. For example, CN109682402A, "a fiber bragg grating sensor", is characterized in that a plurality of through holes are formed on the fiber core of an optical fiber at intervals, and sensing materials are filled in the through holes in a one-to-one correspondence manner, because each sensing material is used for reflecting light waves in different and mutually independent wavelength ranges, and the wavelength of the reflected light waves changes with the change of the measured parameters; the wavelength of the intercepted light wave is reflected through the spectrometer, namely the numerical value of the measured parameter can be correspondingly obtained, and the sensing and the measurement of multiple parameters are realized. The method is not beneficial to large-area popularization because the fiber core of the optical fiber is damaged, the mechanical strength and the service life of the optical fiber are reduced, and the manufacturing process is complex. Compared with the invention, the invention effectively avoids the difficulty of punching on the optical fiber, and has the advantages of no physical damage to the fiber core, long service life, high mechanical strength and the like.

Disclosure of Invention

The invention provides a fiber grating with the advantages of low insertion loss, no physical damage to the fiber core of the fiber, long service life, high mechanical strength and the like, and a preparation method for easily realizing multi-period fiber grating and maskless writing of the fiber grating. And different functional materials or biological cells are injected to change the refractive index of the cladding, reflection of light waves with different wavelengths is realized, and the material filling type hollow fiber grating and the preparation method thereof can be applied to the fields of biological cell propagation condition detection, fiber sensing and the like.

In order to achieve the above object, the present invention provides a material-filled hollow capillary optical fiber:

a material filling type hollow fiber grating comprises a fiber annular cladding (1), an air hole cladding (4) and a fiber core (3). The air hole cladding (4) is positioned in the center of the optical fiber annular cladding (1), the grating is positioned on the inner wall of the optical fiber annular cladding (1), the refractive index is periodically distributed along the length direction of the optical fiber, and the distance between the grating and the fiber core of the optical fiber is less than 3 microns or the grating is in direct contact with the fiber core of the optical fiber to form weak coupling.

In the above scheme, the optical fiber includes an annular cladding, an air hole cladding and a fiber core, and the fiber core is located in the annular cladding or suspended on the inner wall of the annular cladding.

In the above scheme, the capillary optical fiber air hole may be a single hole, a double hole or a plurality of holes.

The invention relates to a preparation method of a material filling type hollow fiber grating, which comprises the following steps:

the method comprises the following steps: the capillary was heated and snapped off to form a tapered tip, approximately 2 microns in diameter. Aligning the capillary filled with the liquid functional material to the air hole cladding of the capillary optical fiber to be etched, and pressurizing the injector to fill the liquid functional material in the central air hole (4) of the capillary optical fiber;

step two: performing fusion tapering on one end of a capillary optical fiber to be engraved and written, and preparing a semi-closed cavity at one end of the optical fiber;

step three: fixing the semi-closed cavity prepared in the last step in an optical fiber fusion splicer, fixing an injector on an injection pump, and periodically filling the liquid functional material into an air hole cladding of the semi-closed cavity by adjusting the propelling speed, propelling times and interval time of the injector pump, so that the refractive index is periodically changed. The filling condition of the liquid functional material can be monitored in real time by monitoring a display screen of the welding machine;

step four: and finally, performing fusion tapering on the other ends of the two ends of the capillary optical fiber after the writing by using a fusion heating method, and plugging the microfluidic channel to realize the long-period grating array of the air hole cladding of the capillary optical fiber. The grating array is weakly coupled with the fiber core of the optical fiber, and the distance is less than 3 microns or is in direct contact with the fiber core of the optical fiber.

In the scheme, the used functional material is oil drops or other liquid functional materials.

In the above scheme, the functional material filled in the optical fiber can be biological cells, and the optical fiber is periodically arranged to form a grating.

In the above scheme, the grating is formed in the air hole cladding of the capillary fiber.

In the above scheme, the functional material used and the bubble size were 50 microns.

In the scheme, the period of the grating array depends on the periodic distribution of the injected functional material.

In the above scheme, a capillary siphon method can be selected for filling the functional material.

The invention has the following advantages: in the fiber grating sensor manufactured by the prior art, the grating array is inscribed in the fiber core of the optical fiber, so that the fiber grating sensor is not easy to package and has larger loss. The capillary fiber grating designed in the invention plugs the grating in the cladding in a pressurized injection mode, has the advantages of low insertion loss, no physical damage to the fiber core of the fiber, simple structure and the like, is easy to realize multi-period fiber grating and maskless writing of the fiber grating, and can be applied to a plurality of fields of fiber sensing, biomedical treatment and the like.

Drawings

FIG. 1 is a schematic diagram of a material-filled hollow fiber grating according to the present invention.

Fig. 2(a) is a schematic cross-sectional view of a material-filled hollow fiber grating according to the present invention.

Fig. 2(b) is a schematic cross-sectional view of a dual-core material filled hollow fiber grating according to the present invention.

Fig. 2(c) is a schematic cross-sectional view of a suspended core material filled hollow fiber grating according to the present invention.

FIG. 3 is a diagram showing the simulated reflection spectrum of a single-core capillary fiber grating with the wavelength of 1550nm and the grating period of 534 nm.

FIG. 1 is a capillary fiber annular cladding; 2 is a functional material; 3 is the fiber core; 4 is an air hole cladding.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

the invention prepares the grating in the air hole cladding of the capillary fiber by the material filling mode, the fiber core is weakly coupled with the grating, and the distance is less than 3 microns or is directly contacted, thereby realizing the modulation of the optical path. The formation of the cladding grating is to use an injector to perform pressure injection on the functional material, and the functional material is periodically filled in the air hole cladding by adjusting the propelling speed and the interval time of the injection pump, so that the refractive index is periodically changed. And finally, plugging the microfluidic channel by using a thermal processing mode of arc discharge melting tapered, so as to realize the grating array of the capillary optical fiber air hole cladding. The invention has the advantages of low insertion loss, no physical damage to the fiber core of the optical fiber, simple structure and the like, is easy to realize multi-period fiber grating and maskless writing of the fiber grating, can change the refractive index of a cladding by injecting different liquid materials, realizes reflection of light waves with different wavelengths, and can be applied to a plurality of fields of optical fiber sensing, communication and the like.

The functional material used may be oil droplets or other liquid functional material.

The number of air holes of the capillary optical fiber can be expanded to be double holes and multiple holes.

Example 1:

as shown in fig. 1, a schematic diagram of a material-filled hollow fiber grating according to the present invention includes four layers: the optical fiber comprises an optical fiber annular cladding, an air hole cladding, an optical fiber grating and an optical fiber core. The preparation method comprises the following steps:

step 1.1: the capillary was heated and snapped off to form a tapered tip, approximately 2 microns in diameter. Aligning the capillary tube filled with the liquid functional material with an air hole cladding of the capillary optical fiber to be etched, and pressurizing the injector to fill the liquid functional material in a central air hole of the capillary optical fiber;

step 1.2: performing fusion tapering on one end of a capillary optical fiber to be engraved and written, and preparing a semi-closed cavity at one end of the optical fiber;

step 1.3: fixing the semi-closed cavity prepared in the last step in an optical fiber fusion splicer, fixing an injector on an injection pump, and periodically filling the liquid functional material into an air hole cladding of the semi-closed cavity by adjusting the propelling speed, propelling times and interval time of the injector pump, so that the refractive index is periodically changed. The filling condition of the liquid functional material can be monitored in real time by monitoring a display screen of the welding machine;

step 1.4: and finally, performing fusion tapering on the other ends of the two ends of the capillary optical fiber after the writing by using a fusion heating method, and plugging the microfluidic channel to realize the long-period grating array of the air hole cladding of the capillary optical fiber. The grating array is weakly coupled with the fiber core of the optical fiber, and the distance is less than 3 microns or is in direct contact with the fiber core of the optical fiber.

Example 2:

as shown in fig. 2(b), the schematic diagram of the preparation of the dual-hole material filled hollow fiber grating designed by the present invention is that the air holes are symmetrically distributed on both sides of the fiber core, and each air hole is responsible for one grating array, and the specific preparation scheme is as follows:

step 2.1: the capillary was heated and snapped off to form a tapered tip, approximately 2 microns in diameter. Aligning the capillary tube filled with the liquid functional material with the air hole cladding of the capillary optical fiber to be etched, pressurizing the injector to fill the liquid functional material in the central air hole (4) of the capillary optical fiber

Step 2.2: performing fusion tapering on one end of a capillary optical fiber to be engraved and written, and preparing a semi-closed cavity at one end of the optical fiber;

step 2.3: fixing the semi-closed cavity prepared in the last step in an optical fiber fusion splicer, fixing an injector on an injection pump, and periodically filling the liquid functional material into an air hole cladding of the semi-closed cavity by adjusting the propelling speed, propelling times and interval time of the injector pump, so that the refractive index is periodically changed. Repeating the above process to fill the liquid functional material into the second air hole cladding. The filling condition of the liquid functional material can be monitored in real time by monitoring a display screen of the welding machine;

step 2.4: and finally, performing fusion tapering on the other ends of the two ends of the capillary optical fiber after the writing by using a fusion heating method, and plugging the microfluidic channel to realize the double-period grating array of the air hole cladding of the capillary optical fiber. The grating array is weakly coupled with the fiber core of the optical fiber, and the distance is less than 3 microns or is in direct contact with the fiber core of the optical fiber.

The invention provides a material filling type hollow fiber grating and a preparation method thereof, belonging to the technical field of fiber gratings. The capillary fiber grating comprises a fiber annular cladding, an air hole cladding and a fiber core. The air hole cladding is less than 3 microns away from the fiber core or in direct contact with the fiber core. The preparation method of the fiber grating comprises the following steps: the functional material fills the optical fiber air hole cladding by means of pressurized injection. By adjusting the propelling speed, the propelling times and the interval time of the injection pump, the functional material is periodically filled in the air hole cladding, so that the refractive index is periodically changed. And finally, performing fusion tapering on the capillary optical fiber to plug the microfluidic channel, thereby realizing the long-period grating array of the capillary optical fiber air hole cladding. The material filling type hollow fiber grating designed by the invention has the advantages of low insertion loss, no physical damage to the fiber core of the fiber, simple structure and the like, is easy to realize multi-period fiber grating and maskless writing of the fiber grating, can change the refractive index of a cladding by injecting different functional materials, realizes reflection of light waves with different wavelengths, and can be applied to a plurality of fields of fiber sensing, biomedical treatment and the like.