Fiber grating string

Abstract

The utility model provides a fiber bragg grating string, which comprises a fiber core, a cladding coaxially wrapped on the outer wall of the fiber core and a coating layer coaxially wrapped on the outer wall of the cladding, grating inscribing areas are distributed on the fiber core, fiber bragg gratings are inscribed on the grating inscribing areas, a first protective sleeve is coaxially wrapped on the outer wall of the coating layer, and a second protective sleeve is coaxially wrapped on the outer wall of the first protective sleeve. Empty grooves are formed in the positions, located in the grating inscribing area of the fiber core, of the first protection sleeve and the coating layer, the empty grooves are sleeved with second protection sleeves, the two ends of the second protection sleeves make contact with the portions, on the two sides of the empty grooves, of the first protection sleeves, and the outer walls of the second protection sleeves are flush with the outer walls of the first protection sleeves. And a filling bonding layer for bonding the cladding layer, the coating layer, the first protective sleeve and the second protective sleeve into a whole is injected into the empty slot. A traditional coating layer is replaced by the filling bonding layer and the second protective sleeve at the fiber bragg grating, so that the mechanical strength and the anti-fatigue performance of the fiber bragg grating string are improved, and the manufacturing cost is low.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of fiber grating sensor, especially to a fiber grating string. BACKGROUND

[0002] The fiber grating sensor is a kind of sensor based on the principle of fiber grating, it obtains vibration signal by measuring the light intensity variation of fiber grating, to detect the change of temperature, strain, pressure and other physical quantities, with high precision, high sensitivity, strong anti-interference ability and other characteristics.However, in engineering application, the fiber grating sensor generally has the problem of insufficient mechanical strength, especially the fiber grating string is relatively fragile, and is easily damaged in actual working environment.Therefore, it is necessary to improve its mechanical strength and impact resistance, and to make it into a fiber cable with excellent mechanical properties.The coating material and the manufacturing method of the fiber grating string have a great influence on its mechanical strength.The common coating materials of the fiber grating string include acrylate (ordinary optical fiber) and polyamide.The performance of the two materials is significantly different: the mechanical strength of the fiber with acrylate coating is low, and the tensile wavelength range is about 10nm;the fiber with polyamide coating has high mechanical strength, and the tensile wavelength range is about 30nm, but the manufacturing cost is higher.

[0003] There are three common methods for manufacturing fiber grating at present:(1) post-processing writing method: firstly, the existing coating layer of the optical fiber is removed, then the grating is written, and finally the protective coating is re-coated, but this method is only suitable for existing standard optical fiber, and the production efficiency is low, and the tensile wavelength range of the ordinary acrylate coated fiber grating string is only 1nm;(2) online writing method: the grating is directly written during the optical fiber drawing process, and then coated, the tensile wavelength range of the ordinary acrylate coated fiber grating string manufactured by this method is improved to 10nm, and the production efficiency is high, but it needs special production line support, so it is not universal;(3) femtosecond direct writing method: the existing optical fiber is directly written by femtosecond laser, and then coated, this method has high cost and the technology is not yet mature, in addition, the tensile strength of the optical fiber treated by this method is insufficient. SUMMARY

[0004] The utility model provides a kind of fiber grating string, the fiber grating string replaces traditional coating layer with filling adhesive layer and second protective sleeve at fiber grating, forms enhanced protective layer, improves the mechanical strength and fatigue resistance of fiber grating string, and the manufacturing cost is low.

[0005] To solve the above technical problems, the technical scheme of the utility model is as follows:

[0006] An optical fiber grating string comprises a fiber core, a cladding coaxially wrapped outside the fiber core, and a coating layer coaxially wrapped outside the cladding, wherein the fiber core is provided with a grating writing area, the grating writing area is written with an optical fiber grating, the coating layer is coaxially wrapped with a first protective sleeve outside the coating layer, the first protective sleeve and the coating layer are both provided with a hollow slot at the grating writing area of the fiber core, the hollow slot is sleeved with a second protective sleeve, two ends of the second protective sleeve are in contact with the first protective sleeve on both sides of the hollow slot, the outer wall of the second protective sleeve is flush with the outer wall of the first protective sleeve, and the hollow slot is filled with a filling adhesive layer for bonding the cladding, the coating layer, the first protective sleeve and the second protective layer into one body.

[0007] The coating layer is made of acrylate or polyamide.

[0008] The length of the hollow slot is greater than the length of the corresponding grating writing area.

[0009] The thickness of the second protective sleeve is less than the thickness of the first protective sleeve.

[0010] The outer wall of the second protective sleeve is coaxially wrapped with a metal sleeve.

[0011] The length of the metal sleeve is greater than the length of the corresponding second protective sleeve.

[0012] Compared with the prior art, the optical fiber grating string of the utility model has the advantages that (1) the optical fiber grating string of the utility model replaces the traditional coating layer with a filling adhesive layer and a second protective sleeve at the optical fiber grating, forms an enhanced protective layer, the tensile wavelength range of the optical fiber grating string can be more than 30 nm, the mechanical strength and fatigue resistance of the optical fiber grating string are improved, and the optical fiber grating string is particularly suitable for online real-time monitoring of static or dynamic strain.

[0013] (2) The metal sleeve coaxially wrapped outside the second protective sleeve effectively isolates the influence of external stress on the measurement accuracy of the optical fiber grating.

[0014] (3) The first protective sleeve wrapped outside the optical fiber coating layer of the optical fiber grating further protects the optical fiber grating string and ensures that the finally prepared optical fiber grating string has a uniform outer diameter.

[0015] (4) The outer diameter of the optical fiber grating string of the utility model is 1.4 mm, which can be directly pasted on the surface of the measured object during installation, thereby realizing a simple and fast installation process.

[0016] (5) The optical fiber grating string of the utility model has simple structure and mature manufacturing process, does not need to completely strip the coating layer, can realize efficient mass production, can effectively reduce the manufacturing cost of the optical fiber grating string, and ensures an economic and efficient production process. Attached Figure Description

[0017] Figure 1 A cross-sectional view of the fiber Bragg grating string along its length provided by this utility model;

[0018] Figure 2 A cross-sectional view of the fiber Bragg grating string at the fiber Bragg grating inscription location provided by this utility model;

[0019] Figure 3 This is a schematic diagram of the structure of the fiber optic grating string wrapped with a metal sleeve in this utility model;

[0020] In the figure, 1-fiber core, 2-fiber grating, 3-cladding, 4-coating layer, 5-first protective sleeve, 6-second protective sleeve, 7-filler adhesive layer, 8-metal sleeve. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] The fiber grating string structure provided in this embodiment is as follows: Figure 1 and Figure 2 As shown, the fiber grating string includes a fiber core 1, a cladding 3 coaxially wrapped around the outer wall of the fiber core, and a coating layer 4 coaxially wrapped around the outer wall of the cladding. Grating writing areas are distributed on the fiber core, and fiber gratings 2 are written on the grating writing areas.

[0023] In this embodiment, a first protective sleeve 5 is coaxially wrapped on the outer wall of the coating layer. Both the first protective sleeve and the coating layer have slots at the grating writing area of ​​the fiber core. A second protective sleeve 6 is loosely fitted on the slot. The two ends of the second protective sleeve are in contact with the first protective sleeves on both sides of the slot, and the outer wall of the second protective sleeve is flush with the outer wall of the first protective sleeve. A filling adhesive layer 7 is injected into the slot to bond the cladding layer, the coating layer, the first protective sleeve and the second protective layer together.

[0024] Preferably, the coating layer is made of acrylate or polyamide. In this embodiment, an acrylate coating layer is used.

[0025] Preferably, the length of the slot is greater than the length of the corresponding grating writing area, ensuring that the filling adhesive layer and the first protective sleeve set in the slot can effectively protect the fiber grating, thereby ensuring the reliability and stability of the fiber grating.

[0026] Preferably, the thickness of the second protective sleeve is less than the thickness of the first protective sleeve, so that the two sides of the filling adhesive layer are bonded to the first protective sleeve.

[0027] The filling adhesive layer in the embodiment is made of glue, preferably high-performance glue with good mechanical properties, radiation resistance, high insulation and non-combustible properties. The filling adhesive layer is prepared by glue injection process, and the thickness is 0.5 mm. Since the glue injection process is quite mature and can realize efficient mass production, the manufacturing cost of the fiber grating string is effectively reduced, and the economic and efficient production process is ensured.

[0028] Preferably, the outer wall of the second protective sleeve is coaxially wrapped with a metal sleeve 8, and the length of the metal sleeve is greater than the length of the corresponding second protective sleeve, so as to effectively isolate external stress and avoid the influence of external stress on the sensor made of the fiber grating string in temperature monitoring, and realize the function conversion from the strain sensor to the temperature sensor.

[0029] The manufacturing method of the fiber grating string provided in the embodiment is as follows:

[0030] (1) Take a common optical fiber (including a core, a cladding and a coating layer), remove the coating layer on the optical fiber segment where the fiber grating needs to be written (i.e. form a hollow groove), so as to expose a segment of bare optical fiber (including a core and a cladding), i.e. expose the grating writing area. Specifically, the length of the hollow groove is greater than the length of the corresponding grating writing area.

[0031] (2) Use femtosecond laser technology or an excimer laser to accurately write different wavelength fiber Bragg gratings on the bare optical fiber, for example, the wavelength range of all fiber gratings is 1528-1568 nm, and the wavelength interval of adjacent fiber gratings is 1 nm, so as to construct a wavelength division multiplexing fiber Bragg grating array;

[0032] (3) After writing the fiber grating, a second protective sleeve is sleeved on the grating writing area, and high-performance glue is injected into the gap between the second protective sleeve and the bare optical fiber to form a filling adhesive layer after solidification; so as to form a firm sheath outside the grating writing area, and ensure the stability and reliability of the fiber grating;

[0033] (4) A first protective sleeve is wrapped outside the fiber coating layer where no fiber grating is written by using a heat-shrinkable sleeve combined with a hot melting process, and the first protective sleeve is connected with the second protective sleeve by the filling adhesive layer to form an integral whole, and the outer wall of the second protective sleeve is flush with the outer wall of the first protective sleeve, so as to ensure that the finally obtained fiber grating string has a uniform outer diameter, i.e. 1.4 mm.

[0034] The tensile wavelength range of the fiber grating string with the acrylate coating layer prepared in the embodiment can exceed 30 nm, which significantly improves the mechanical strength and reliability, and also maintains a relatively low cost.

Claims

1. A fiber grating string comprising a fiber core, a cladding coaxially wrapped on an outer wall of the fiber core, and a coating layer coaxially wrapped on an outer wall of the cladding, wherein a grating inscription region is arranged on the fiber core, and a fiber grating is inscribed on the grating inscription region, characterized in that: The outer wall of the coating layer is coaxially covered by a first protective sleeve, and the first protective sleeve and the coating layer are both provided with a hollow slot at the grating writing area of the fiber core, the hollow slot is coaxially covered by a second protective sleeve, the two ends of the second protective sleeve are in contact with the first protective sleeve on both sides of the hollow slot, the outer wall of the second protective sleeve is flush with the outer wall of the first protective sleeve, and the hollow slot is filled with a filling adhesive layer for bonding the cladding layer, the coating layer, the first protective sleeve and the second protective layer into one body. ​ 2. The fiber grating string of claim 1, wherein: The coating layer is made of acrylate or polyamide.

3. The fiber grating string of claim 1, wherein: The length of the hollow slot is greater than the length of the corresponding grating writing area.

4. The fiber grating string of claim 1, wherein: The thickness of the second protective sleeve is less than the thickness of the first protective sleeve.

5. The fiber grating string of claim 1, wherein: The outer wall of the second protective sleeve is coaxially covered by a metal sleeve.

6. The fiber grating string of claim 5, wherein: The length of the metal sleeve is greater than the length of the corresponding second protective sleeve.

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