Transmission optical fiber and laser

Abstract

The invention discloses a transmission optical fiber and a laser, and belongs to the technical field of optical fibers. The transmission optical fiber comprises a fiber core and a wrapping layer wrapping the fiber core, the wrapping layer comprises a first isolation layer, a first transmission layer, a second isolation layer and an outer side layer which are sequentially arranged from inside to outside, and the fiber core and the first transmission layer can transmit laser; the refractive index of the fiber core is n1, the refractive indexes of the first isolation layer and the second isolation layer are n2, the refractive index of the first transmission layer is n3, n1 is larger than n2 and smaller than n3, the thick plate cutting and welding application scene can be matched, and the operation effect is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to a transmission optical fiber and a laser. Background Art

[0002] Ultra-high power fiber lasers are widely used in the field of material processing. Figure 1 As shown in the solid line, the existing ultra-high power laser outputs a Gaussian distribution or a flat-top distribution-like laser beam 100' with uniform energy control, which can meet normal cutting and other applications. However, in the thick plate cutting and welding application scenarios in heavy industry and other fields, the laser of the above spot has too concentrated energy distribution and a short Rayleigh length, that is, the Gaussian distribution laser beam 100' has a thin waist in the middle of the length direction, and the diameter of the spot changes significantly in the length direction. In the thick plate cutting application, it is easy to have problems such as the cross section of the plate to be cut 200 is not smooth enough, slag is hanging on the bottom, and the cross section 210' is too large in taper; in the thick plate welding application, it is easy to have welding slag splashing, poor weld appearance, and insufficient penetration. Summary of the invention

[0003] The object of the present invention is to provide a transmission optical fiber and a laser that can match the above-mentioned thick plate cutting and welding application scenarios and improve the operation effect.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] A transmission optical fiber comprises a core and a cladding covering the core, wherein the cladding comprises a first isolation layer, a first transmission layer, a second isolation layer and an outer layer arranged in sequence from the inside to the outside, and the core and the first transmission layer are both capable of transmitting lasers; the refractive index of the core is n1, the refractive index of the first isolation layer and the second isolation layer are both n2, and the refractive index of the first transmission layer is n3, wherein n2<n1<n3.

[0006] In some possible implementations, the refractive index of the first transmission layer is greater than the refractive index of the fiber core, and the difference in refractive index between the fiber core and the first transmission layer is in the range of 0.01-0.06.

[0007] In some possible implementations, the numerical aperture of the fiber core is in the range of 0.05-0.21; and / or the numerical aperture of the first transmission layer is in the range of 0.06-0.22.

[0008] In some possible implementations, the cladding further includes a second transmission layer and a third isolation layer which are sequentially arranged between the second isolation layer and the outer layer from the inside to the outside.

[0009] In some possible implementations, the refractive index of the third isolation layer is equal to the refractive index of the first isolation layer; and / or the refractive index of the second transmission layer is equal to the refractive index of the fiber core.

[0010] In some possible implementations, the cladding further includes M intermediate transmission layers and M intermediate isolation layers that are alternately arranged between the third isolation layer and the outer layer from the inside to the outside, where M is an integer greater than or equal to 1.

[0011] In some possible embodiments, the refractive index of the M intermediate isolation layers is equal to the refractive index of the first isolation layer; when M is an odd number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the first transmission layer; when M is an even number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the second transmission layer.

[0012] In some possible embodiments, the diameter of the fiber core is 14 μm-100 μm; and / or the thickness of the first isolation layer and the second isolation layer is in the range of 5 μm-20 μm; and / or the thickness of the first transmission layer and the outer layer is in the range of 20 μm-100 μm.

[0013] A laser comprises the transmission optical fiber as described in any one of the above items.

[0014] In some possible implementations, the laser further includes a cladding light stripper for filtering out cladding light transmitted from an outer layer.

[0015] Beneficial effects of the present invention:

[0016] The present invention provides a transmission optical fiber and laser, which add a first transmission layer on the outside of the fiber core, and the fiber core and the first transmission layer form beam spots respectively, thereby forming a double-ring spot. Since the refractive index of the first transmission layer is greater than the refractive index of the optical fiber, the energy density of the double-ring spot is more uniform, that is, the energy distribution of the ultra-high power spot is controlled, and the formed laser beam improves the thin waist, increases the Rayleigh length, and reduces the taper. The ideal state is taper-free cutting, which is beneficial to improving the cutting or welding effect of thick plate materials, especially the taper and quality of the cross-section of the cut plate are greatly improved. In actual welding, it can better suppress welding spatter and achieve the effect of beautiful welds. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a laser beam with Gaussian distribution (solid line) in the prior art and a laser beam (dashed line) provided in an embodiment of the present invention cutting a plate to be cut;

[0018] Figure 2is a schematic diagram of the refractive index distribution of a transmission optical fiber provided in one embodiment of the present invention;

[0019] Figure 3 is a schematic cross-sectional view of a transmission optical fiber provided in one embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of the refractive index distribution of a transmission optical fiber provided in another embodiment of the present invention;

[0021] Figure 5 It is a schematic cross-sectional view of a transmission optical fiber provided in another embodiment of the present invention.

[0022] In the figure:

[0023] 100', laser beam; 210', cross section; 100, laser beam; 200, plate to be cut; 210, cross section;

[0024] 1. Fiber core; 2. Cladding; 21. First isolation layer; 22. First transmission layer; 23. Second isolation layer; 24. Outer layer; 25. Third isolation layer; 26. Second transmission layer. DETAILED DESCRIPTION

[0025] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0028] like Figure 1 The dotted line part Figure 2 and Figure 3 As shown, this embodiment provides a transmission optical fiber, including a core 1 and a cladding 2 coated on the core 1, the cladding 2 includes a first isolation layer 21, a first transmission layer 22, a second isolation layer 23 and an outer layer 24 arranged in sequence from the inside to the outside, that is, the cladding 2 is provided with four layers. The core 1 and the first transmission layer can both transmit lasers, and can output light beams in the core 1 and the first transmission layer 22 respectively; the refractive index of the core 1 is n1, the refractive index of the first isolation layer 21 and the second isolation layer 23 are both n2, and the refractive index of the first transmission layer 22 is n3, wherein n2<n1<n3.

[0029] By adding the first transmission layer 22 to the outside of the core 1, the core 1 and the first transmission layer 22 form beam spots respectively, thereby forming a double-ring spot. Since the refractive index of the first transmission layer 22 is greater than the refractive index of the core 1, the energy density of the double-ring spot is more uniform, that is, the energy distribution of the ultra-high power spot is controlled, and the formed laser beam 100 improves the thin waist situation and increases the Rayleigh length. When applied to thick plate cutting, the taper of the cut section 210 is reduced. The ideal state is taper-free cutting, which is conducive to improving the cutting or welding effect of thick plate materials, especially the taper and quality of the section 210 after cutting the plate 200 to be cut. In actual welding, it can better suppress welding spatter and achieve the effect of beautiful welds.

[0030] Optionally, the difference in refractive index between the core 1 and the first transmission layer 22 is in the range of 0.01-0.06, and the refractive index of the first transmission layer 22 is slightly greater than the refractive index of the core 1. Too large or too small a difference in refractive index will affect the uniformity of the light spot. Exemplarily, the difference between the two can be 0.01, 0.02, 0.03, 0.04, 0.05 or 0.06, etc.

[0031] The numerical aperture size relationship is the same as the refractive index size relationship, that is, the numerical aperture of the first transmission layer 22 is slightly larger than the numerical aperture of the core 1. Optionally, the numerical aperture of the core 1 is in the range of 0.05-0.21; and / or, the numerical aperture of the first transmission layer 22 is in the range of 0.06-0.22. Optionally, the numerical aperture of the core 1 is in the range of 0.05-0.10, 0.10-0.15 or 0.15-0.21, etc., and optionally, the numerical aperture of the first transmission layer 22 is in the range of 0.06-0.10, 0.10-0.15 or 0.15-0.22, etc., and optionally, the numerical aperture of the core 1 is in the range of 0.05-0.10, and the numerical aperture of the first transmission layer 22 is in the range of 0.10-0.15. Alternatively, the numerical aperture of the core 1 is in the range of 0.10-0.15, and the numerical aperture of the first transmission layer 22 is in the range of 0.15-0.22. Optionally, the numerical aperture of the core 1 is 0.05, 0.10, 0.15, 0.20, and the numerical aperture of the first transmission layer 22 is 0.06, 0.11, 0.16, 0.21, respectively. Taking the numerical aperture of the core 1 as 0.15 as an example, the numerical aperture of the core 1 determines the critical angle of total reflection of the laser in the core 1. The numerical aperture of the core 1 is NA, that is, NA=0.15, and the critical angle of total reflection of the laser is θc, where θc=arcsin(NA). If the divergence angle of the laser exceeds the critical angle of total reflection θc, that is, the divergence angle of the laser exceeds arcsin0.15, the laser will leak into the adjacent isolation layer and then leak into the transmission layer. If the numerical aperture of the core 1 and the numerical aperture of the first transmission layer 22 are too large or too small, the laser will not leak into the transmission layer or leak too much into the transmission layer, and both cannot meet the requirements.

[0032] The diameter of the fiber core 1 is 14μm-100μm, the thickness of the first isolation layer 21 and the second isolation layer 23 is in the range of 5μm-20μm, and the thickness of the first transmission layer 22 and the outer layer 24 is in the range of 20μm-100μm. The first isolation layer 21 or the second isolation layer 23 with a thickness of 5μm-20μm cannot bind the laser, and the laser coupled into the first transmission layer 22 and the outer layer 24 with a thickness of 20μm-100μm can be transmitted normally. Therefore, the laser will pass through the first isolation layer 21 and enter the first transmission layer 22 for normal transmission, and can also be transmitted through the second isolation layer 23 and enter the outer layer 24, but will be filtered out by the cladding light stripper.

[0033] A coating layer is provided on the outside of the outer layer 24, and the refractive index of the coating layer is lower than the refractive index of the core 1. On the one hand, the cladding 2 is protected from the influence of the external environment, and is made of materials such as polyimide, acrylate, silicone rubber, etc., which have good weather resistance, wear resistance and insulation, and can prevent the transmission optical fiber from mechanical damage, chemical corrosion, moisture erosion, etc. On the other hand, the use of a low-refractive-index coating layer can ensure total internal reflection at the boundary between the core 1 and the cladding 2, ensure that the light is confined in the cladding 2 and the core 1, and prevent the optical signal from leaking to the outside of the transmission optical fiber, thereby achieving efficient and stable transmission.

[0034] The laser also includes a cladding light stripper for filtering out the cladding light transmitted by the outer layer 24. The laser outputs a double-ring light spot through the fiber core 1 and the first transmission layer 22, making the output of the laser more stable and pure.

[0035] In the second embodiment, if Figure 4 and Figure 5 As shown, the cladding 2 also includes a second transmission layer 26 and a third isolation layer 25 which are sequentially arranged between the second isolation layer 23 and the outer layer 24 from the inside to the outside. The core 1, the first transmission cladding 22 and the second transmission cladding 26 of the transmission optical fiber can all transmit lasers, that is, the cladding 2 is provided with six layers. By adding the second transmission layer 26, that is, increasing the number of transmission layers, the laser beam 100 is controlled to be output through more transmission layers, and the energy density of the annular light spot is further made more uniform, the Rayleigh length is further increased, and the taper of the cut section 210 is reduced. After the cladding light of the outer layer 24 is stripped using a cladding light stripper, the laser outputs a three-ring light spot through the core 1, the first transmission layer 22 and the second transmission layer 26.

[0036] Furthermore, the refractive index of the third isolation layer 25 is equal to the refractive index of the first isolation layer 21; and / or the refractive index of the second transmission layer 26 is equal to the refractive index of the fiber core 1, which further improves the uniformity of the energy density of the annular light spot.

[0037] In the third embodiment, the cladding 2 further includes M intermediate transmission layers and M intermediate isolation layers arranged alternately from the inside to the outside between the third isolation layer 25 and the outer layer 24, wherein M is an integer greater than or equal to 1; the refractive index of the M intermediate isolation layers is equal to the refractive index of the first isolation layer 21; when M is an odd number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the first transmission layer 22, and when M is an even number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the second transmission layer 26. The laser can be transmitted in the core 1 and the cladding 2 of the transmission optical fiber, that is, the cladding 2 is provided with more than eight layers, and the transmission layer is provided with more than four layers. When a cladding light stripper is used, the laser outputs a four-ring light spot or a multi-ring light spot through the core 1, the first transmission layer 22 and the outer layer 24, the second transmission layer 26, and M-1 intermediate transmission layers. Optionally, M is 1, 2, 3, 4, 5 or 6, etc., without limitation.

[0038] In the transmission optical fiber, since in addition to the core 1, the first transmission layer 22, the outer layer 24, the second transmission layer 26 and the Mth intermediate transmission layer all have the function of transmitting signals, compared with ordinary optical fibers in which only the core 1 has the function of transmitting signals, the transmission optical fiber in this embodiment has increased its ability to withstand lasers, and the laser can generate an output light beam of 80kW-160kW, achieving ultra-high power spot output.

[0039] This embodiment also provides a laser, including an optical module, an output coupler, a cladding light stripper and the above-mentioned transmission optical fiber. Among them, the optical module is such as a pump source, the pump source generates an optical signal, which is transmitted through the transmission optical fiber, and then the light beam is coupled through the output coupler, and then the laser in the outer layer 24 is stripped by the cladding light stripper to prevent the cladding from transmitting a large numerical aperture laser that affects the reliability and application effect of the laser, and finally outputs a laser beam 100 for cutting or welding. The above-mentioned transmission optical fiber realizes the output of double-ring light spots, triple-ring light spots or multi-ring light spots, etc. On the one hand, it realizes the control of the energy distribution of ultra-high-power light spots, and the formed laser beam 100 improves the thin waist situation, increases the Rayleigh length, and reduces the taper, which is beneficial to improve the cutting or welding effect of thick plate materials. On the other hand, the transmission optical fiber increases the tolerance of the laser, and the laser can generate an output beam of 80kW-160kW, realizing ultra-high-power light spot output.

[0040] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A transmission optical fiber, characterized in that: The invention comprises a fiber core (1) and a cladding (2) covering the fiber core (1), wherein the cladding (2) comprises a first isolation layer (21), a first transmission layer (22), a second isolation layer (23) and an outer layer (24) arranged in sequence from the inside to the outside, and the fiber core (1) and the first transmission layer (22) are both capable of transmitting laser light; the refractive index of the fiber core (1) is n1, the refractive index of the first isolation layer (21) and the second isolation layer (23) are both n2, and the refractive index of the first transmission layer (22) is n3, wherein n2<n1<n3.

2. The transmission optical fiber according to claim 1, characterized in that: The refractive index of the first transmission layer (22) is greater than the refractive index of the fiber core (1), and the difference in refractive index between the fiber core (1) and the first transmission layer (22) is in the range of 0.01-0.

06.

3. The transmission optical fiber according to claim 2, characterized in that: The numerical aperture of the fiber core (1) is in the range of 0.05-0.21; and / or the numerical aperture of the first transmission layer (22) is in the range of 0.06-0.

22.

4. The transmission optical fiber according to claim 1, characterized in that: The cladding (2) further comprises a second transmission layer (26) and a third isolation layer (25) which are arranged between the second isolation layer (23) and the outer layer (24) in sequence from the inside to the outside.

5. The transmission optical fiber according to claim 4, characterized in that: The refractive index of the third isolation layer (25) is equal to the refractive index of the first isolation layer (21); and / or the refractive index of the second transmission layer (26) is equal to the refractive index of the fiber core (1).

6. The transmission optical fiber according to claim 4, characterized in that: The cladding (2) further comprises M intermediate transmission layers and M intermediate isolation layers which are alternately arranged between the third isolation layer (25) and the outer layer (24) from the inside to the outside, wherein M is an integer greater than or equal to 1.

7. The transmission optical fiber according to claim 6, characterized in that: The refractive indexes of the M intermediate isolation layers are all equal to the refractive index of the first isolation layer (21); when M is an odd number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the first transmission layer (22); when M is an even number, the refractive index of the Mth intermediate transmission layer is equal to the refractive index of the second transmission layer (26).

8. The transmission optical fiber according to any one of claims 1 to 7, characterized in that: The diameter of the fiber core (1) is 14 μm-100 μm; and / or the thickness of the first isolation layer (21) and the second isolation layer (23) is in the range of 5 μm-20 μm; and / or the thickness of the first transmission layer (22) and the outer layer (24) is in the range of 20 μm-100 μm.

9. A laser, characterized in that: Comprising the transmission optical fiber according to any one of claims 1-8.

10. The laser according to claim 9, characterized in that The laser also includes a cladding light stripper for filtering out the cladding light transmitted by the outer layer (24).

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