Double-channel side hole fiber grating sensing device
Technical Field
The invention belongs to the field of optical fiber sensing, and particularly relates to a double-channel side hole optical fiber grating sensing device.
Background
With the continuous progress of society, the related problems of food and drug safety, environmental protection and the like are gradually paid attention to by people, and the food, the drug and the water quality need to be analyzed quickly and accurately. For the fields of biological detection and drug synthesis, the lab-on-a-chip based on the microfluidic technology has a wide application, and the optical fiber is conveniently combined with the lab-on-a-chip as a device on the micrometer scale. The fiber grating is an important passive device in the field of fiber communication, and compared with other sensors, the fiber grating device has the advantages of immune electromagnetic interference, long-term stability and compact structure. Therefore, the fiber grating has wide application prospect when being applied to a lab-on-a-chip.
The fiber gratings commonly applied to the microfluidic chip are generally two types, one type is the traditional fiber grating, the fiber end face for manufacturing the fiber grating is not porous and is a standard single-mode fiber, the outer diameter is 125 μm, and the core diameter is 4-8 μm. The literature, "Optical fiber biological sensor integrated microfluidic chip for ultra-sensitive detection, biological Optical Express,2016,7(5): 2067-2077", reports a microfluidic chip based on single-mode fiber grating, in which the microfluidic channel is mainly on the microfluidic chip, and the sensing channel is only one, so that the detection rate of the microfluidic chip is generally slow. Another type is a microstructured Fiber grating, which has holes in its end faces for the passage of fluids, document "Fiber-Based Channels reflective Index Available for Microfluidic Chip,2017,29 (23): 2087-2090 reports an internal micro-flow fiber grating, which realizes the sensing of internal and external channels, and if the fiber grating is used in a micro-flow chip, the detection rate is theoretically doubled. However, the liquid injection structure of the microstructure optical fiber in the article is not stable enough, the welding spot is fragile, and the sensor is easy to damage in practical application.
Disclosure of Invention
The invention aims to provide a double-channel side-hole fiber grating sensing device with a stable structure, which realizes multi-channel micro-flow sensing of side-hole fiber liquid injection in an optical fiber through special processing and packaging of a side-hole fiber and a single-mode fiber.
The purpose of the invention is realized as follows:
a double-channel side hole fiber grating sensing device comprises a single-mode fiber 1 subjected to oblique grinding, a first side hole fiber 2 subjected to oblique grinding, a second side hole fiber 3, a first liquid injection pump 4-1, a second liquid injection pump 4-2, a first liquid injection micro-tube 5-1, a second liquid injection micro-tube 5-2, a first capillary tube 6-1, a second capillary tube 6-2, a first packaging adhesive 7-1 and a second packaging adhesive 7-2, wherein the first side hole fiber 2 subjected to oblique grinding is provided with double holes which are respectively a first hole 2-1 and a second hole 2-2, and the second side hole fiber 3 is provided with double holes which are respectively a third hole 3-1 and a fourth hole 3-2; the obliquely ground end face of the single-mode optical fiber 1 subjected to oblique grinding treatment is a first end face 1-1, and the obliquely ground end face of the first side hole optical fiber 2 subjected to oblique grinding treatment is a second end face 2-3; the second side hole optical fiber 3 is also provided with a first grating structure 3-3 and a second grating structure 3-4, a first end face 1-1 and the left end of the first side hole optical fiber 2 which is processed by oblique grinding are welded together by an optical fiber fusion welding machine, the second end face 2-3 and the left end of the second side hole optical fiber 3 are welded together, a first capillary 6-1 is used for packaging a first liquid injection micro-tube 5-1, the first end face 1-1 and the left end welding part of the first side hole optical fiber 2 which is processed by oblique grinding together, and the two ends are sealed by a first packaging adhesive 7-1, a second capillary 6-2 is used for packaging the welding part of the second liquid injection micro-tube 5-2, the second end face 2-3 and the left end of the second side hole optical fiber 3 together, the two ends are sealed by a second packaging adhesive 7-2, a first liquid injection pump 4-1 injects liquid into the first capillary 6-1 through the first micro-tube 5-1, and the second liquid injection pump 4-2 injects liquid into the second capillary 6-2 through the second liquid injection micro-tube 5-2, the first liquid enters the fourth hole 3-2 of the second side hole optical fiber 3 through the first hole 2-1 of the first side hole optical fiber 2 subjected to oblique grinding treatment, and the second liquid enters the third hole 3-1 through the second side hole optical fiber 3.
The inclined grinding depth of the first end surface 1-1 is not more than 58.5 mu m.
The inclined grinding depth of the second end face 2-3 is not more than 58.5 mu m.
The sizes of the two holes of the first side hole optical fiber 2 and the second side hole optical fiber 3 which are processed by the inclined grinding are not more than 40 μm.
The first liquid injection micro-tube 5-1 and the second liquid injection micro-tube 5-2 are hollow optical fibers or thin capillaries.
The outer diameter of the hollow optical fiber is 125 micrometers, the inner diameter of the hollow optical fiber is 60 micrometers, and the outer diameter of the fine capillary is not more than 125 micrometers.
The first capillary 6-1 and the second capillary 6-2 are glass capillaries, and the inner diameters of the capillaries are larger than 250 μm.
The refractive index of the first liquid is different from that of the second liquid.
The first packaging adhesive 7-1 and the second packaging adhesive 7-2 are AB adhesives.
The first grating structure 3-3 and the second grating structure 3-4 are written in different radial angles of the optical fiber, so that the third hole 3-1 and the fourth hole 3-2 have different response coefficients to the grating region, the periods of the first grating structure 3-3 and the second grating structure 3-4 are different and have a difference of 20-80nm, the refractive index response parameters of the first grating structure 3-3 and the second grating structure 3-4 are obtained through testing, and a sensing matrix K of the sensor, namely the sensing matrix K of the sensor is obtained
By reading the variation of the resonance wavelength in the grating spectrumAAnd Δ λBTo obtain a change Deltan of the refractive index in the third hole 3-1 and the fourth hole 3-21And Δ n2。
The invention has the beneficial effects that:
the invention realizes the functions of single-hole liquid injection and double-hole liquid injection, namely, the microfluidic chip based on the structure realizes two working modes of simplex and duplex, and under the duplex working mode, the working efficiency of the microfluidic chip is two times of that of the simplex theoretically.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a block diagram of a sensing system;
FIG. 3 is a schematic diagram of a connection between a single mode optical fiber that has been skew-polished and a first side-hole optical fiber that has been skew-polished;
FIG. 4 is a schematic diagram of a connection of a first side-hole fiber and a second side-hole fiber that have been processed by beveling;
FIG. 5 is a schematic end view of a single mode optical fiber;
FIG. 6 is a schematic end view of a second hole-side fiber;
FIG. 7 is a transmission spectrum of a second edge-hole fiber grating;
FIG. 8 is a plot of the refractive index response of channel A in a second edge-holey fiber;
FIG. 9 is a graph showing the refractive index profile of channel B in a second edge-holey fiber.
The specific implementation mode is as follows:
the invention is further described below with reference to the accompanying drawings.
Example 1 a complete set of test devices is shown in figure 2: the device comprises a light source 8, a side hole optical fiber liquid injection integral device 9 and a detector 10.
The light source 8 is selected by the working wavelength of the fiber grating and is an ASE light source or a supercontinuum light source or a frequency stabilization light source.
As shown in fig. 1-8, a dual-channel side-hole fiber grating sensing device includes a single-mode fiber 1 subjected to oblique milling, a first side-hole fiber 2 subjected to oblique milling, a second side-hole fiber 3, a first liquid injection pump 4-1, a second liquid injection pump 4-2, a first liquid injection micro-tube 5-1, a second liquid injection micro-tube 5-2, a first capillary tube 6-1, a second capillary tube 6-2, a first encapsulation adhesive 7-1, and a second encapsulation adhesive 7-2, wherein the first side-hole fiber 2 subjected to oblique milling has double holes, which are a first hole 2-1 and a second hole 2-2, respectively, and the second side-hole fiber 3 has double holes, which are a third hole 3-1 and a fourth hole 3-2, respectively; the obliquely ground end face of the single-mode optical fiber 1 subjected to oblique grinding treatment is a first end face 1-1, and the obliquely ground end face of the first side hole optical fiber 2 subjected to oblique grinding treatment is a second end face 2-3; the second side hole optical fiber 3 is also provided with a first grating structure 3-3 and a second grating structure 3-4, a first end face 1-1 and the left end of the first side hole optical fiber 2 which is processed by oblique grinding are welded together by an optical fiber fusion welding machine, a second end face 2-3 and the left end of the second side hole optical fiber 3 are welded together, a first capillary 6-1 is used for packaging a first liquid injection micro-tube 5-1, a first end face 1-1 and the left end welding part of the first side hole optical fiber 2 which is processed by oblique grinding together, and the two ends are sealed by a first packaging adhesive 7-1, a second capillary 6-2 is used for packaging the welding part of the second liquid injection micro-tube 5-2, a second end face 2-3 and the left end of the second side hole optical fiber 3 together, the two ends are sealed by a second packaging adhesive 7-2, a first liquid injection pump 4-1 injects liquid into the first capillary 6-1 through the first micro-tube 5-1, the second liquid injection pump 4-2 injects liquid into the second capillary 6-2 through the second liquid injection micro-tube 5-2, the first liquid enters the fourth hole 3-2 of the second side hole optical fiber 3 through the first hole 2-1 of the first side hole optical fiber 2 which is processed by oblique grinding, the channel is called as a channel A, the second liquid enters the third hole 3-1 through the second side hole optical fiber 3, and the channel is called as a channel B, so that the simultaneous sensing of different liquids is realized in one optical fiber.
The inclined grinding depth of the first end surface 1-1 is not more than 58.5 mu m.
The inclined grinding depth of the second end face 2-3 is not more than 58.5 mu m.
The sizes of the two holes of the first side hole optical fiber 2 and the second side hole optical fiber 3 which are processed by the inclined grinding are not more than 40 μm.
The first liquid injection micro-tube 5-1 and the second liquid injection micro-tube 5-2 are hollow optical fibers or thin capillaries.
The outer diameter of the hollow optical fiber is 125 micrometers, the inner diameter of the hollow optical fiber is 60 micrometers, and the outer diameter of the fine capillary is not more than 125 micrometers.
The first capillary 6-1 and the second capillary 6-2 are glass capillaries, and the inner diameters of the capillaries are larger than 250 μm.
The refractive index of the first liquid is different from that of the second liquid.
The first packaging adhesive 7-1 and the second packaging adhesive 7-2 are AB adhesives.
The first grating structure 3-3 and the second grating structure 3-4 are written in different radial angles of the optical fiber, so that the third hole 3-1 and the fourth hole 3-2 have different response coefficients to a grating region, the periods of the first grating structure 3-3 and the second grating structure 3-4 are different and have a difference of 20-80nm, the refractive index response parameters of the first grating structure 3-3 and the second grating structure 3-4 are obtained through testing, and a sensing matrix K of the sensor is obtained, namely the sensing matrix K is
By reading the variation of the resonance wavelength in the grating spectrumAAnd Δ λBWe know the change of refractive index Δ n in the third hole 3-1 and the fourth hole 3-21And Δ n2。
Fig. 7 is a transmission spectrum of a microfluidic fiber grating sensor, in which two resonant "valleys" are respectively from a first grating structure 3-3 and a second grating structure 3-4, and the long-period fiber grating is modulated in its axial periodic refractive index, so that light energy is scattered and absorbed in the cladding when passing through the device, thereby causing "valleys" corresponding to different resonant wavelengths in the spectrum. The phase matching formula of the resonance wavelength is as follows:
wherein λ is the resonance wavelength of the light,
is the refractive index of the core and is,
and lambda is the period of the fiber grating. Refractive index of cladding when air passage of optical fiber passes through different liquid
A change occurs, causing a change in the resonant wavelength lambda.
Fig. 8 is a graph of the refractive index response of the first grating structure 3-3 and the grating structure 3-4 in channel a, which results in a different refractive index response of the two gratings in channel a due to the different writing angles of the first grating structure 3-3 and the second grating structure 3-4 in the fiber. The refractive index response of the first grating structure 3-3 in channel a is 80nm/RIU and the refractive index response of the second grating structure 3-4 is 150.93 nm/RIU.
Fig. 9 shows the refractive index response of the first grating structure 3-3 and the second grating structure 3-4 in channel B, where the refractive index response of the first grating structure 3-3 is 160nm/RIU and the refractive index response of the second grating structure 3-4 is 87.14 nm/RIU.
It should be noted that other non-illustrated embodiments and structural descriptions given herein are well-known in the art, and those skilled in the art can find relevant documents according to the names or descriptions of the present invention, and therefore will not further describe the present invention. The technical means disclosed in the present embodiment is not limited to the technical means disclosed in the above embodiments, and includes any combination of the above technical features.