Hollow-core anti-resonance active optical fiber

Abstract

The utility model relates to a hollow-core anti-resonance active optical fiber. The hollow-core anti-resonance active optical fiber comprises a cladding region and a fiber core region, the cladding area sequentially comprises an outer cladding, a first anti-resonance layer and a second anti-resonance layer from outside to inside; wherein the first anti-resonance layer comprises a plurality of first anti-resonance tubes which are rotationally and symmetrically distributed, second anti-resonance tubes are nested in the first anti-resonance tubes, and the inner wall surfaces of the first anti-resonance tubes and the outer wall surfaces of the second anti-resonance tubes are tangent to a first point; the second anti-resonance layer comprises a plurality of doped anti-resonance tubes which are rotationally and symmetrically distributed, and the doped anti-resonance tubes and the first anti-resonance tubes are tangent and arranged in a staggered manner; the second anti-resonance layer is closer to the center of the active optical fiber relative to the first anti-resonance layer, and an irregular region surrounded by the boundaries of the first anti-resonance layer and the second anti-resonance layer is a fiber core region. The problem that the application of the hollow-core anti-resonance optical fiber in long-distance transmission is limited due to the fact that the hollow-core anti-resonance optical fiber cannot carry out light amplification while transmitting light like a traditional rare earth doped optical fiber can be solved.

Description

Technical Field

[0001] The present application relates to the field of optical fiber technology, and in particular to a hollow-core anti-resonant active optical fiber. Background Art

[0002] As the mainstream transmission medium of the current optical fiber communication system, optical fiber is widely used in various long and short distance transmission scenarios due to its advantages such as low cost, large capacity and high security. With the deepening of research and the increase in demand, the core of the fiber has begun to be doped with activated ions such as rare earth elements, and the fiber is pumped to emit light, so that the passive fiber is "activated" and becomes a doped active fiber. Generally, one or more rare earth elements, such as neodymium (Nd), ytterbium (Yb), erbium (Er), thulium (Tm), etc., are doped into the active optical fiber to generate new light waves or amplify optical signals.

[0003] Compared with solid core optical fiber, hollow core optical fiber mainly binds energy in the air core, reduces the use of quartz material, and fundamentally solves the intrinsic problem of quartz material. According to the light guiding mechanism and fiber structure of optical fiber, hollow core optical fiber can be roughly divided into hollow core bandgap photonic crystal fiber (PBG-PCF) and hollow core anti-resonant fiber (NANF, anti-resonant node l ess fiber). Among them, hollow core bandgap photonic crystal fiber mainly uses the photonic bandgap effect to guide light, which determines the narrow bandwidth of this type of optical fiber and the scattering of the core surface mode. The hollow core anti-resonant fiber guides light in the form of leakage mode. When the lateral propagation constant of light in the core does not resonate with the quartz tube ring, it is a window that can guide light.

[0004] In recent years, hollow-core antiresonant optical fiber has rapidly become a hot topic in international research due to its advantages such as wider transmission spectrum, higher laser threshold damage and lower transmission loss.

[0005] However, hollow-core antiresonant fibers cannot amplify light while transmitting it like traditional rare-earth-doped fibers, which limits the application of hollow-core antiresonant fibers in future long-distance transmission. Summary of the invention

[0006] The embodiment of the present application provides a hollow-core anti-resonant active optical fiber to solve the problem in the related art that the hollow-core anti-resonant optical fiber cannot amplify light while transmitting light like the traditional rare-earth-doped optical fiber, which limits the application of the hollow-core anti-resonant optical fiber in long-distance transmission.

[0007] The embodiment of the present application provides a hollow core anti-resonant active optical fiber, wherein the active optical fiber includes a cladding region and a core region;

[0008] The cladding region includes, from outside to inside, an outer cladding, a first anti-resonance layer and a second anti-resonance layer;

[0009] The first anti-resonance layer comprises a plurality of first anti-resonance tubes distributed in rotational symmetry, and a second anti-resonance tube is nested in the first anti-resonance tube, and the inner wall surface of the first anti-resonance tube is tangent to the outer wall surface of the second anti-resonance tube at a first point; the second anti-resonance layer comprises a plurality of doped anti-resonance tubes distributed in rotational symmetry, and the doped anti-resonance tubes are tangent to the first anti-resonance tubes and are arranged in a staggered manner;

[0010] The second anti-resonance layer is closer to the center of the active optical fiber than the first anti-resonance layer, and the irregular region surrounded by the boundary between the first anti-resonance layer and the second anti-resonance layer is the core region.

[0011] In some embodiments, the doped anti-resonance tube is a rare-earth doped capillary.

[0012] In some embodiments, the rare earth includes one or more of neodymium Nd, ytterbium Yb, erbium Er and thulium Tm.

[0013] In some embodiments, the center of the outer cladding, the center of the first anti-resonance tube, the center of the second anti-resonance tube, and the first point are located on the same straight line.

[0014] In some embodiments, the outer wall surface of the first anti-resonance tube is tangent to the inner wall surface of the outer cladding at a second point, and the center of the first anti-resonance tube, the first point and the second point are located on the same straight line.

[0015] In some embodiments, the outer cladding, the first anti-resonance tube, the second anti-resonance tube and the doped anti-resonance tube are all circular tube structures.

[0016] In some embodiments, the wall thickness of the outer cladding is greater than 40 μm.

[0017] In some embodiments, the number of the first anti-resonance tubes is 4-10.

[0018] In some embodiments, in the core region, a diameter D of a virtual circle circumscribed with all doped anti-resonance tubes is 8-100 μm.

[0019] In some embodiments, the core region is filled with air;

[0020] The wall thickness of the first anti-resonance tube is t 1 , the refractive index is n 1 , the wall thickness of the second anti-resonance tube is t 2 , the refractive index is n 2 , the wall thickness of the doped anti-resonance tube is t 3 , the refractive index is n 3 , t 1 ,t 2 and t 3All satisfy the following relationship:

[0021]

[0022] Where i = 1, 2, 3, λ is the wavelength of the light transmitted in the optical fiber, N is a positive integer, n i is the refractive index of the first anti-resonance tube, the second anti-resonance tube or the doped anti-resonance tube, n 0 is the refractive index of air in the core region.

[0023] The beneficial effects of the technical solution provided by this application include:

[0024] Compared with leaving a part of the anti-resonance tube for doping and the rest undoped, the present application directly uses a fully doped doped anti-resonance tube to form a second anti-resonance layer. This method of doping is simple, easy to implement, and convenient for large-scale production. Through this externally active doped anti-resonance tube, coupling with the transmission hollow-core optical fiber can be achieved, reducing coupling losses. Moreover, compared with partially doped anti-resonance tubes, the present application increases the contact area between the signal light and the doping element of the fully doped doped anti-resonance tube, and the gain effect is better.

[0025] The present application adopts an optical fiber structure design in which the fundamental mode mode field distribution is precisely matched with the doping area distribution. The anti-resonance tube with the spatial distribution of the fundamental mode mode field adopts a rare-earth-doped anti-resonance tube, thereby regulating the gain amplification characteristics of the fundamental mode, while suppressing the gain of the high-order mode, increasing the loss of the high-order mode, achieving effective amplification of the fundamental mode, solving the gain amplification problem of the hollow-core optical fiber, and realizing long-distance transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic diagram of a hollow core anti-resonant active optical fiber provided in one embodiment of the present application;

[0028] Figure 2 A schematic diagram of a hollow-core anti-resonant active optical fiber provided in another embodiment of the present application.

[0029] In the figure: 1. outer cladding; 2. first anti-resonance tube; 3. second anti-resonance tube; 4. doped anti-resonance tube. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] See also Figure 1 and Figure 2 As shown, an embodiment of the present application provides a hollow-core anti-resonant active optical fiber, the active optical fiber comprising a cladding region and a core region; the cladding region comprises an outer cladding 1, a first anti-resonant layer and a second anti-resonant layer in sequence from outside to inside along the radial direction of the optical fiber.

[0032] Among them, the first anti-resonance layer includes a plurality of first anti-resonance tubes 2 that are rotationally symmetrically distributed, and a second anti-resonance tube 3 is nested in the first anti-resonance tube 2, the inner diameter of the second anti-resonance tube 3 is smaller than the inner diameter of the first anti-resonance tube 2, and the inner wall surface of the first anti-resonance tube 2 is tangent to the outer wall surface of the second anti-resonance tube 3 at a first point; the second anti-resonance layer includes a plurality of doped anti-resonance tubes 4 that are rotationally symmetrically distributed, the doped anti-resonance tubes 4 are tangent to the first anti-resonance tubes 2 and are arranged in a staggered manner, so that one doped anti-resonance tube 4 is provided between any two adjacent first anti-resonance tubes 2; it can be understood that the fixed point of rotational symmetry of the first anti-resonance tube 2 and the fixed point of rotational symmetry of the doped anti-resonance tube 4 are both the center of the outer cladding 1. It can be understood that the first anti-resonance tubes 2 are evenly distributed at equal intervals along the circumference of the outer cladding 1.

[0033] The second anti-resonance layer is closer to the center of the active optical fiber than the first anti-resonance layer, and the irregular region surrounded by the boundary between the first anti-resonance layer and the second anti-resonance layer is the core region.

[0034] Compared with leaving a part of the anti-resonance tube for doping and the rest undoped, the present application directly uses a fully doped doped anti-resonance tube to form a second anti-resonance layer. This method of doping is simple, easy to implement, and convenient for large-scale production. Through this externally active doped anti-resonance tube, coupling with the transmission hollow-core optical fiber can be achieved, reducing coupling losses. Moreover, compared with partially doped anti-resonance tubes, the present application increases the contact area between the signal light and the doping element of the fully doped doped anti-resonance tube, and the gain effect is better, which can reach 0.2dB / m.

[0035] The present application adopts an optical fiber structure design in which the fundamental mode mode field distribution is precisely matched with the doping area distribution. The anti-resonance tube with the spatial distribution of the fundamental mode mode field adopts a rare-earth-doped anti-resonance tube, thereby regulating the gain amplification characteristics of the fundamental mode, while suppressing the gain of the high-order mode, increasing the loss of the high-order mode, achieving effective amplification of the fundamental mode, solving the gain amplification problem of the hollow-core optical fiber, and realizing long-distance transmission.

[0036] It can be understood that, generally, the diameter of the doped anti-resonance tube 4 is smaller than the diameter of the first anti-resonance tube 2 .

[0037] It is understandable that the doped anti-resonance tube 4 uses a rare earth doped capillary, and the rare earth doped capillary can be directly made by oneself, or purchased as a finished product, or prepared according to existing relevant public information.

[0038] The rare earth includes one or more of neodymium Nd, ytterbium Yb, erbium Er and thulium Tm. The specific rare earth or rare earths to be used can be determined according to actual performance requirements.

[0039] It can be understood that the outer cladding 1, the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 can all adopt a circular tube structure, such as a capillary tube.

[0040] See also Figure 1 As shown, the center of the outer cladding 1 , the center of the first anti-resonance tube 2 , the center of the second anti-resonance tube 3 , and the first point are located on the same straight line.

[0041] See also Figure 1 As shown, the outer wall surface of the first anti-resonance tube 2 is tangent to the inner wall surface of the outer cladding 1 at the second point, and the center of the first anti-resonance tube 2, the first point and the second point are located on the same straight line.

[0042] Preferably, the wall thickness of the outer cladding layer 1 is greater than 40 μm.

[0043] Preferably, the number of the first anti-resonance tubes 2 is 4-10.

[0044] See also Figure 1 As shown, in the core region, the diameter D of the virtual circle circumscribed with all the doped anti-resonance tubes 4 is 8-100 μm, preferably, D is 20-100 μm.

[0045] It is understandable that the core region may be filled with air, the outer cladding 1 may be filled with air, the first anti-resonance tube 2 may be filled with air, and the second anti-resonance tube 3 may be filled with air.

[0046] The wall thickness of the first anti-resonance tube 2 is t 1 , the refractive index is n 1, the wall thickness of the second anti-resonance tube 3 is t 2 , the refractive index is n 2 The wall thickness of the doped anti-resonance tube 4 is t 3 , the refractive index is n 3 , t 1 ,t 2 and t 3 The value range of is [0.1μm, 4μm], and all satisfy the following relationship:

[0047]

[0048] Where i = 1, 2, 3, λ is the wavelength of the light transmitted in the optical fiber, N is a positive integer, n i is the refractive index of the first anti-resonance tube 2, the second anti-resonance tube 3 or the doped anti-resonance tube 4, n 0 is the refractive index of air in the core region.

[0049] It can be understood that when i=1, in the above formula, t i t 1 , that is, the wall thickness of the first anti-resonance tube 2, n i n 1 , that is, the refractive index of the first anti-resonance tube 2.

[0050] When i=2, in the above formula, t i t 2 , that is, the wall thickness of the second anti-resonance tube 3, n i n 2 , that is, the refractive index of the second anti-resonance tube 3 .

[0051] When i=3, in the above formula, t i t 3 , that is, the wall thickness of the doped anti-resonance tube 4, n i n 3 , that is, the refractive index of the doped antiresonance tube 4.

[0052] It can be understood that N is a positive integer, that is, N=1, 2, 3, . . .

[0053] When i=1, 2 or 3, the value of N may be different, and the specific value of N may be assigned according to factors such as the actual required performance of the optical fiber.

[0054] Example 1

[0055] The hollow-core anti-resonance active optical fiber provided in this embodiment has 5 nested groups formed by the first anti-resonance tube 2 and the second anti-resonance tube 3, and the outer cladding 1, the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 are all made of SiO 2glass, the other gas parts are all air, the doping element is erbium, and the thickness of the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 is 2um.

[0056] See also Figure 1 As shown, the outer cladding 1 of the hollow-core anti-resonance active optical fiber adopts a circular capillary tube, which has 5 nested groups inside, including a first anti-resonance tube 2 and a nested second anti-resonance tube 3. The nested groups are evenly spaced; the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 and the core area are all air; the outer cladding 1 has a coating layer outside the tube.

[0057] The inner wall surface of the first anti-resonance tube 2 is tangent to the outer wall surface of the second anti-resonance tube 3 at a first point, the outer wall surface of the first anti-resonance tube 2 is tangent to the inner wall surface of the outer cladding 1 at a second point, and the center of the outer cladding 1, the center of the first anti-resonance tube 2, the center of the second anti-resonance tube 3, the first point and the second point are located on the same straight line.

[0058] The doped anti-resonance tube 4 is a capillary tube doped with erbium ions, which can realize internal fundamental mode light amplification and is suitable for use as a repeater for long-distance transmission.

[0059] This example is a hollow core anti-resonant active fiber that achieves amplification in the C band, with a core diameter of 70μm. The loss of the hollow core anti-resonant active fiber in the communication area is 0.06dB / Km, and the absorption loss at 980nm is 4dB / km. The gain in the C band is 0.25dB / m.

[0060] Example 2

[0061] The hollow-core anti-resonance active optical fiber provided in this embodiment has 6 nested groups formed by the first anti-resonance tube 2 and the second anti-resonance tube 3, and the outer cladding 1, the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 are all made of SiO 2 glass, the other gas parts are all air, the doping element is thulium, and the thickness of the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 is 2um.

[0062] See also Figure 2 As shown, the outer cladding 1 of the hollow-core anti-resonance active optical fiber adopts a circular capillary tube, which has 6 nested groups inside, including a first anti-resonance tube 2 and a nested second anti-resonance tube 3. The nested groups are evenly spaced; the first anti-resonance tube 2, the second anti-resonance tube 3 and the doped anti-resonance tube 4 and the core area are all air; the outer cladding 1 has a coating layer outside the tube.

[0063] The inner wall surface of the first anti-resonance tube 2 is tangent to the outer wall surface of the second anti-resonance tube 3 at a first point, the outer wall surface of the first anti-resonance tube 2 is tangent to the inner wall surface of the outer cladding 1 at a second point, and the center of the outer cladding 1, the center of the first anti-resonance tube 2, the center of the second anti-resonance tube 3, the first point and the second point are located on the same straight line.

[0064] The doped anti-resonance tube 4 is a capillary doped with thulium ions, and the wavelength range in the S band is: 1460nm-1530nm1, the loss is 0.06dB / Km, the absorption coefficient at 790nm is 2.80dB / m, and the gain is>0.21dB / m.

[0065] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0066] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0067] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A hollow core anti-resonant active optical fiber, characterized in that: The active optical fiber includes a cladding region and a core region; The cladding region includes, from the outside to the inside, an outer cladding (1), a first anti-resonance layer and a second anti-resonance layer; The first anti-resonance layer comprises a plurality of first anti-resonance tubes (2) distributed in a rotationally symmetrical manner, and a second anti-resonance tube (3) is nested in the first anti-resonance tube (2), and an inner wall surface of the first anti-resonance tube (2) is tangent to an outer wall surface of the second anti-resonance tube (3) at a first point; the second anti-resonance layer comprises a plurality of doped anti-resonance tubes (4) distributed in a rotationally symmetrical manner, and the doped anti-resonance tubes (4) are tangent to the first anti-resonance tube (2) and are arranged in a staggered manner; The second anti-resonance layer is closer to the center of the active optical fiber than the first anti-resonance layer, and the irregular region surrounded by the boundary between the first anti-resonance layer and the second anti-resonance layer is the core region.

2. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The doped anti-resonance tube (4) is a rare earth doped capillary tube.

3. The hollow core anti-resonant active optical fiber according to claim 2, characterized in that: The rare earth is neodymium Nd, ytterbium Yb, erbium Er or thulium Tm.

4. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The center of the outer cladding (1), the center of the first anti-resonance tube (2), the center of the second anti-resonance tube (3) and the first point are located on the same straight line.

5. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The outer wall surface of the first anti-resonance tube (2) is tangent to the inner wall surface of the outer cladding (1) at a second point, and the center of the first anti-resonance tube (2), the first point and the second point are located on the same straight line.

6. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The outer cladding (1), the first anti-resonance tube (2), the second anti-resonance tube (3) and the doped anti-resonance tube (4) are all circular tube structures.

7. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The wall thickness of the outer cladding (1) is greater than 40 μm.

8. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The number of the first anti-resonance tubes (2) is 4-10.

9. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: In the core region, a diameter D of a virtual circle circumscribed with all doped anti-resonance tubes (4) is 8-100 μm.

10. The hollow core anti-resonant active optical fiber according to claim 1, characterized in that: The fiber core region is filled with air; The wall thickness of the first anti-resonance tube (2) is t1, and the refractive index is n1; the wall thickness of the second anti-resonance tube (3) is t2, and the refractive index is n2; the wall thickness of the doped anti-resonance tube (4) is t3, and the refractive index is n3; t1, t2 and t3 all satisfy the following relationship: Where i = 1, 2, 3, λ is the wavelength of the light transmitted in the optical fiber, N is a positive integer, n i is the refractive index of the first anti-resonance tube (2), the second anti-resonance tube (3) or the doped anti-resonance tube (4), and n0 is the refractive index of the air in the core region.

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