Hollow-core optical fiber and optical cable

Abstract

The invention relates to a hollow-core optical fiber and an optical cable. The hollow-core optical fiber comprises a cladding region and a fiber core region, the cladding region comprises an outer cladding and an anti-resonance layer which are sequentially arranged from outside to inside; the fiber core region comprises a region surrounded by the boundaries of the anti-resonance layer and the outer cladding layer; wherein the anti-resonance layer comprises a plurality of nesting units which are rotationally and symmetrically distributed, each nesting unit comprises a first nesting ring and a second nesting ring nested in the first nesting ring, the first nesting ring is connected to the inner wall of the outer cladding at a first arc length, and the second nesting ring is connected to the inner wall of the outer cladding at a second arc length. And the second nesting ring is connected to the inner wall of the first nesting ring at a second arc length at a position where the first nesting ring is connected to the inner wall of the outer cladding. According to the invention, the problem that the nested ring structure of the hollow-core optical fiber is poor in stability and is easily affected by external stress to deform in the prior art can be solved.

Description

Technical Field

[0001] The present application relates to the field of optical communication technology, and in particular to a hollow core optical fiber and an optical cable. Background Art

[0002] The one-dimensional planar antiresonant reflective optical waveguide (ARROW) theoretical model allows light to be transmitted in a core medium with a lower refractive index. This is very different from the theory of traditional optical fiber based on the high refractive index of the core and the low refractive index of the cladding, which constitutes a total reflection mechanism to transmit light in the high refractive index core. When light is transmitted in the air core of a hollow-core optical fiber, the speed is nearly 30% faster than that in the high refractive index core of a quartz optical fiber. Therefore, the hollow-core optical fiber communication system has an advantage of 30% lower latency than the traditional quartz optical fiber communication system. This huge advantage has attracted people's attention. In addition, since the hollow-core optical fiber also has low nonlinearity, low dispersion characteristics, and can maintain the original transmission characteristics in an irradiated environment, it has significant advantages in many aspects such as long-distance and large-capacity transmission, ultrafast lasers, data centers, and space communications. Since it was proposed more than 30 years ago, it has been a hot topic of research.

[0003] Since the Kagome structure hollow-core fiber was proposed, the attenuation of hollow-core fiber has been decreasing, but its attenuation has been difficult to break through the level of less than 0.150dB / km. In recent years, some researchers have developed a core structure with negative curvature to obtain lower losses, and then developed a nested tube structure HC-ARF. In 2022, some researchers reported a double-nested antiresonant hollow-core fiber. The loss of this fiber in the C-band is comparable to that of commercial solid-core fiber (0.174dB / km). Hollow-core fibers for short-wavelength transmission from 200nm to 800nm ​​and hollow-core fibers for mid-infrared band transmission with a wide range of uses are also still being promoted.

[0004] However, in the actual research process, people found that hollow-core optical fibers are very susceptible to external stress, resulting in increased attenuation. This is because the existing structure is extremely dependent on the maintenance of the nested ring shape, that is, the nested rings theoretically use tangent point contact to maintain the shape, and in order to achieve a better shape, the thickness of each nested ring is in the micron range. This tiny structure combined with the tangent point contact leads to poor stability of the nested rings, which are very susceptible to deformation due to external influences. When the nested rings are deformed by stress, the fitting circle located in the center and tangent to each nested ring will be deformed and no longer a regular shape, which will cause the effective mode field area of ​​the light to change, causing a sharp increase in attenuation. Therefore, on the one hand, it is necessary to design a new structure to resist the adverse effects of this deformation, and on the other hand, it is necessary to develop the product form of optical fiber cables for the final application of optical fiber to better protect the optical fiber from external interference. Therefore, the existing optical fiber structure needs to be more robust to adapt to the influence of optical fiber performance degradation caused by the large control fluctuation range brought by the actual manufacturing process. Summary of the invention

[0005] The embodiments of the present application provide a hollow-core optical fiber and an optical cable to solve the problem in the related art that the nested ring structure of the hollow-core optical fiber has poor stability and is easily deformed by external stress.

[0006] In a first aspect, a hollow core optical fiber is provided, wherein the hollow core optical fiber comprises a cladding region and a core region;

[0007] The cladding region includes an outer cladding layer and an anti-resonance layer arranged in sequence from outside to inside;

[0008] The core region includes a region surrounded by the boundary between the anti-resonance layer and the outer cladding;

[0009] The anti-resonance layer includes a plurality of rotationally symmetrically distributed nested units, wherein the nested units include a first nested ring and a second nested ring nested in the first nested ring, the first nested ring is connected to the inner wall of the outer cladding with a first arc length, and the second nested ring is connected to the inner wall of the first nested ring at a position where the first nested ring is connected to the inner wall of the outer cladding with a second arc length.

[0010] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1, and the value range of θ1 / π is 6% to 16%;

[0011] And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring is θ2, and the value range of θ2 / π is 8% to 24%;

[0012] and / or, a ratio k1 of an outer radius R2 of the second nested ring to an inner radius r1 of the first nested ring is in a range of 0.45 to 0.6;

[0013] And / or, the value range of the ratio k2 of the wall thickness t2 of the second nested ring to the wall thickness t1 of the first nested ring is as follows:

[0014]

[0015] Wherein, N is the number of the first nested rings, and n is the refractive index of the material used for the hollow core optical fiber.

[0016] In some embodiments, the anti-resonance layer further includes an auxiliary resonant ring disposed between two adjacent nested units, and an outer wall of the auxiliary resonant ring is tangent to an inner wall of the outer cladding layer.

[0017] In some embodiments, the nested unit further comprises a third nested ring nested in the second nested ring, the third nested ring being connected to the inner wall of the second nested ring at a position where the second nested ring is connected to the inner wall of the first nested ring with a third arc length.

[0018] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1, and the value range of θ1 / π is 6% to 16%;

[0019] And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring is θ2, and the value range of θ2 / π is 8% to 20%;

[0020] And / or, the central angle formed by the third arc length and the center point P3 of the third nested ring is θ3, and the value range of θ3 / π is 6% to 15%;

[0021] and / or, a ratio k1 of an outer radius R2 of the second nested ring to an inner radius r1 of the first nested ring is in a range of 0.7 to 0.9;

[0022] And / or, the wall thickness t2 of the second nested ring is in the range of 0.3um to 1.0um;

[0023] and / or, a ratio of an outer radius R3 of the third nested ring to an inner radius r1 of the first nested ring is in a range of 0.2 to 0.4;

[0024] And / or, the wall thickness t3 of the third nested ring is in the range of 0.2um to 0.5um.

[0025] In some embodiments, the anti-resonance layer further includes an auxiliary resonant ring disposed between two adjacent nested units, and an outer wall of the auxiliary resonant ring is tangent to an inner wall of the outer cladding layer.

[0026] In some embodiments, the ratio of the outer radius R6 of the auxiliary resonant ring to the inner radius r1 of the first nested ring is in the range of 0 to 0.4 and is not 0;

[0027] And / or, the wall thickness t6 of the auxiliary resonant ring has a value range of 0.2um to 0.5um.

[0028] In some embodiments, the core region includes an effective core, and the effective core is a circular region formed by virtual circles that are simultaneously circumscribed to each of the first nested rings;

[0029] When the transmission wavelength λ of light is 1200nm~1600nm, the radius r0 of the effective core satisfies:

[0030] r0=k0×(r-2×R1);

[0031] Wherein, r is the inner radius of the outer cladding, R1 is the outer radius of the first nested ring, and k0 is the transmission coefficient, and the value range is as follows:

[0032]

[0033] θ1 is the central angle formed by the first arc length and the center point P1 of the first nested ring;

[0034] When the transmission wavelength λ of light is 2um to 11um, the radius r0 of the effective core is in the range of 25um to 250um;

[0035] When the transmission wavelength λ of light is 200nm-1100nm, the radius r0 of the effective core has a value range of 5um-200um.

[0036] In some embodiments, there is a spacing x between two adjacent first nested rings, and x>0.

[0037] In some embodiments, the wall thickness of the first nested ring is t1=R1-r1, R1 is the outer radius of the first nested ring, and r1 is the inner radius of the first nested ring;

[0038] When the wall thickness t1 of the first nested ring is less than 1 μm, the value range of the spacing x is: X to 2X;

[0039] in,

[0040] When the wall thickness t1 of the first nested ring is ≥1 μm, the value range of the spacing x is: Y to 2Y;

[0041] in,

[0042] r is the inner radius of the outer cladding, N is the number of the first nested rings, and n is the refractive index of the material used for the hollow core optical fiber.

[0043] In some embodiments, the central angle formed by the first arc length and the center point P1 of the first nested ring is θ1;

[0044] When θ1 / π≤8%, the value range of the wall thickness t1 of the first nested ring is:

[0045]

[0046] When θ1 / π>8%, the value range of the wall thickness t1 of the first nested ring is: 0.2λ~0.8λ, λ is the transmission wavelength of light.

[0047] In some embodiments, the hollow core optical fiber is made of quartz, the outer cladding is coated with a resin protective layer, a sleeve layer is disposed outside the resin protective layer, and a sheath layer is disposed outside the sleeve layer.

[0048] In some embodiments, the resin protective layer includes an inner layer and an outer layer, the modulus of the inner layer is 0.1 MPa to 1.2 MPa, and the modulus of the outer layer is greater than 500 MPa.

[0049] In some embodiments, the material of the sleeve layer includes polyurethane TPU, polyester PBT, polyethylene PE, polypropylene PP, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

[0050] In some embodiments, an auxiliary reinforcement piece is further provided between the sleeve layer and the jacket layer.

[0051] In some embodiments, the auxiliary reinforcement comprises aramid yarn and / or glass yarn.

[0052] In some embodiments, the hollow core optical fiber is made of polymer material or glass.

[0053] In some embodiments, the polymer material includes polystyrene PS, polymethacrylate PMMA, polycarbonate PC, polyester PBT, polyethylene PE, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

[0054] In some embodiments, the glass includes chalcogenide glass or fluoride glass.

[0055] In a second aspect, an optical cable is provided, comprising any hollow core optical fiber as described above.

[0056] The beneficial effects of the technical solution provided by this application include:

[0057] The hollow-core optical fiber provided in the present application, the various nested rings contained in the nested units, do not adopt the existing tangent point contact method, but are connected in a certain arc length manner, and are connected to the outer cladding in a certain arc length manner. The arc length connection increases the contact surface, ensures the stability between the nested rings and between the nested rings and the outer cladding, and even if affected by external stress, due to the high stability between the nested rings and between the nested rings and the outer cladding, the fitting circle located in the center and tangent to each nested ring is not easy to deform, thereby improving its ability to maintain a regular shape and avoiding a sharp increase in attenuation due to changes in the effective mode field area of ​​​​the light. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] 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.

[0059] Figure 1 A cross-sectional view of a hollow-core optical fiber provided in an embodiment of the present application (N=5);

[0060] Figure 2 A cross-sectional view of a hollow-core optical fiber provided in an embodiment of the present application (N=6);

[0061] Figure 3 A cross-sectional view of a hollow-core optical fiber provided in an embodiment of the present application (N=4);

[0062] Figure 4 A schematic diagram of a hollow core optical fiber provided in an embodiment of the present application;

[0063] Figure 5 Attenuation curve of the hollow-core optical fiber provided in the embodiment of the present application near 1550nm.

[0064] In the figure: 1. outer cladding; 2. anti-resonance layer; 21. first nested ring; 22. second nested ring; 23. third nested ring; 24. auxiliary resonant ring; 3. effective core; 4. resin protective layer; 5. casing layer; 6. sheath layer. DETAILED DESCRIPTION

[0065] 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.

[0066] See also Figure 1 , Figure 2 and Figure 3 As shown, an embodiment of the present application provides a hollow-core optical fiber, the hollow-core optical fiber comprising a cladding region and a core region; the cladding region comprises an outer cladding 1 and an antiresonance layer 2 arranged in sequence from outside to inside; the core region comprises a region surrounded by the boundary between the antiresonance layer 2 and the outer cladding 1; wherein the antiresonance layer 2 comprises a plurality of rotationally symmetrically distributed nested units, the nested units comprising a first nested ring 21 and a second nested ring 22 nested in the first nested ring 21, the first nested ring 21 is connected to the inner wall of the outer cladding 1 with a first arc length, the second nested ring 22 is connected to the inner wall of the first nested ring 21 with a second arc length at a position where the first nested ring 21 is connected to the inner wall of the outer cladding 1, it can be understood that, in the region surrounded by the boundary between the antiresonance layer 2 and the outer cladding 1, there is a virtual circle, the virtual circle is simultaneously circumscribed to each of the first nested rings 21, so that the region where the virtual circle is located forms the effective core 3 of the core region.

[0067] The hollow-core optical fiber provided in the present application, the various nested rings contained in the nested units, do not adopt the existing tangent point contact method, but are connected in a certain arc length manner, and are connected to the outer cladding in a certain arc length manner. The arc length connection increases the contact surface, ensures the stability between the nested rings and between the nested rings and the outer cladding, and even if affected by external stress, due to the high stability between the nested rings and between the nested rings and the outer cladding, the fitting circle located in the center and tangent to each nested ring is not easy to deform, thereby improving its ability to maintain a regular shape and avoiding a sharp increase in attenuation due to changes in the effective mode field area of ​​​​the light.

[0068] For ease of understanding, this application is uniformly stipulated as follows:

[0069] The effective core 3 and the outer cladding 1 share the same center, the center is denoted as point P0, and the radius of the effective core 3 is r0. The inner radius of the outer cladding 1 is r, and the outer radius of the outer cladding 1 is R.

[0070] The number of nested units included in the anti-resonance layer 2 is the same as the number of first nested rings 21 . Specifically, the number of first nested rings 21 is denoted as N, and N may be 3, generally 4 and 5, and may also be 6 or more.

[0071] The center of the first nested ring 21 is point P1, the inner radius is r1, the outer radius is R1, the wall thickness is t1, and t1=R1-r1. The central angle formed by the first arc length and the center point P1 is θ1.

[0072] The center of the second nested ring 22 is point P2, the inner radius is r2, the outer radius is R2, the wall thickness is t2, and t2=R2-r2. The central angle formed by the second arc length and the center point P2 is θ2.

[0073] The center of the third nested ring 23 is point P3, the inner radius is r3, the outer radius is R3, the wall thickness is t3, and t3=R3-r3. The central angle formed by the third arc length and the center point P3 is θ3.

[0074] The inner radius of the auxiliary resonant ring 24 is r6, the outer radius is R6, the wall thickness is t6, and t6=R6-r6.

[0075] In order to minimize the attenuation of light waves transmitted in the effective core 3 of the hollow-core optical fiber, the first nested rings 21 are distributed at equal intervals, so that the first nested rings 21 are arranged in an equilateral polygon with point P0 as the center.

[0076] On the basis of the first nested ring 21 and the second nested ring 22 of the present application, nested rings can be further arranged inside the second nested ring 22. Specifically, the nested unit also includes a third nested ring 23, and the third nested ring 23 is nested inside the second nested ring 22. The third nested ring 23 is connected to the inner wall of the second nested ring 22 at the position where the second nested ring 22 is connected to the inner wall of the first nested ring 21 with a third arc length.

[0077] It can be understood that when the nested unit only includes the first nested ring 21 and the second nested ring 22 , the center point P0 of the outer envelope 1 is collinear with the center point P1 of the first nested ring 21 and the center point P2 of the second nested ring 22 .

[0078] When the nested unit includes the first nested ring 21 , the second nested ring 22 and the third nested ring 23 , the center point P0 of the outer envelope 1 is collinear with the center point P1 of the first nested ring 21 , the center point P2 of the second nested ring 22 and the center point P3 of the third nested ring 23 .

[0079] In order to better form anti-resonance and reduce attenuation in the effective core 3 , the anti-resonance layer 2 further includes an auxiliary resonant ring 24 disposed between two adjacent nested units, and the outer wall of the auxiliary resonant ring 24 is tangent to the inner wall of the outer cladding 1 .

[0080] When the nested unit consists of only the first nested ring 21 and the second nested ring 22, the central angle formed by the first arc length and the center point P1 of the first nested ring 21 is θ1, and the value range of θ1 / π is 6% to 16%; the central angle formed by the second arc length and the center point P2 of the second nested ring 22 is θ2, and the value range of θ2 / π is 8% to 24%; the ratio k1 of the outer radius R2 of the second nested ring 22 to the inner radius r1 of the first nested ring 21 is in the range of 0.45 to 0.6; the ratio k2 of the wall thickness t2 of the second nested ring 22 to the wall thickness t1 of the first nested ring 21 is as follows:

[0081]

[0082] Wherein, N is the number of the first nested rings 21, and n is the refractive index of the material used for the hollow core optical fiber.

[0083] It can be understood that the refractive index of the material used for the hollow-core optical fiber is also the refractive index of the hollow-core optical fiber, and the material used for the hollow-core optical fiber can be quartz, or it can be glass or polymer material, among which glass is usually a mixture, and quartz is pure silicon dioxide. If the hollow-core optical fiber uses quartz, the refractive index is the refractive index of quartz, and if the hollow-core optical fiber uses polymer material, the refractive index is the refractive index of the polymer material.

[0084] It is understandable that the structures included in the hollow core optical fiber, namely the outer cladding, the anti-resonance layer, etc., are generally made of the same material.

[0085] When the nested unit only has the first nested ring 21 and the second nested ring 22, if an auxiliary resonant ring 24 is also provided, the ratio of the outer radius R6 of the auxiliary resonant ring 24 to the inner radius r1 of the first nested ring 21 is in the range of 0 to 0.4, and is not 0; the wall thickness t6 of the auxiliary resonant ring 24 is in the range of 0.2um to 0.5um.

[0086] When the nested unit has only the first nested ring 21 and the second nested ring 22, the number of the first nested rings 21 can be 5 or 6, etc., and if there are auxiliary resonant rings 24, the number of the auxiliary resonant rings 24 is 5 or 6, etc.

[0087] When the nested unit includes a first nested ring 21, a second nested ring 22 and a third nested ring 23, the central angle formed by the first arc length and the center point P1 of the first nested ring 21 is θ1, and the value range of θ1 / π is 6% to 16%; the central angle formed by the second arc length and the center point P2 of the second nested ring 22 is θ2, and the value range of θ2 / π is 8% to 20%; the central angle formed by the third arc length and the center point P3 of the third nested ring 23 is θ3, and the value of θ3 / π is The range is 6% to 15%; the ratio k1 of the outer radius R2 of the second nested ring 22 to the inner radius r1 of the first nested ring 21 is in the range of 0.7 to 0.9; the wall thickness t2 of the second nested ring 22 is in the range of 0.3um to 1.0um; the ratio of the outer radius R3 of the third nested ring 23 to the inner radius r1 of the first nested ring 21 is in the range of 0.2 to 0.4; the wall thickness t3 of the third nested ring 23 is in the range of 0.2um to 0.5um.

[0088] When the nested unit includes a first nested ring 21, a second nested ring 22 and a third nested ring 23, if an auxiliary resonant ring 24 is also provided, the ratio of the outer radius R6 of the auxiliary resonant ring 24 to the inner radius r1 of the first nested ring 21 is in the range of 0 to 0.4, and is not 0; the wall thickness t6 of the auxiliary resonant ring 24 is in the range of 0.2um to 0.5um.

[0089] When the nested unit includes a first nested ring 21, a second nested ring 22 and a third nested ring 23, the number of the first nested rings 21 can be 4, 5 or 6, etc., and if there are auxiliary resonant rings 24, the number of the auxiliary resonant rings 24 is 4, 5 or 6, etc.

[0090] The core region includes an effective core 3 , and the effective core 3 is a circular region formed by virtual circles that are simultaneously circumscribed to each of the first nested rings 21 .

[0091] When the transmission wavelength λ of light is 1200nm-1600nm, the radius r0 of the effective core 3 satisfies: r0=k0×r-2×R1.

[0092] Wherein, r is the inner radius of the outer cladding 1, R1 is the outer radius of the first nested ring 21, and k0 is the transmission coefficient, and the value range is as follows:

[0093]

[0094] Wherein, θ1 is the central angle formed by the first arc length and the center point P1 of the first nested ring 21 .

[0095] It is understandable that, because hollow-core optical fibers have certain losses, in order to express the influence of such losses on the size of the effective core 3, a transmission coefficient k0 is introduced, and the value of the coefficient is limited in combination with θ1.

[0096] When the nested unit only has the first nested ring 21 and the second nested ring 22, when the transmission wavelength λ of the light is 1200nm-1600nm, the corresponding minimum attenuation is about 0.045dB / km, and the dispersion range is 1.0ps / (nm·km)-5.0ps / (nm·km).

[0097] When the nested unit includes the first nested ring 21, the second nested ring 22 and the third nested ring 23, when the transmission wavelength λ of light is 1200nm~1600nm, the corresponding minimum attenuation is about 0.030dB / km, and the dispersion range is 3.0ps / (nm·km)~5.0ps / (nm·km).

[0098] When the nested unit only has the first nested ring 21 and the second nested ring 22, or when the nested unit includes the first nested ring 21, the second nested ring 22 and the third nested ring 23, when the transmission wavelength λ of the light is 2um~11um, the radius r0 of the effective fiber core 3 ranges from 25um to 250um; the average attenuation is less than 3dB / km, and the minimum attenuation is approximately less than 0.3dB / km.

[0099] When the nested unit has only the first nested ring 21 and the second nested ring 22, or when the nested unit includes the first nested ring 21, the second nested ring 22 and the third nested ring 23, when the transmission wavelength λ of the light is 200nm~1100nm, the radius r0 of the effective fiber core 3 ranges from 5um to 200um, the average attenuation is less than 5dB / km, and the minimum attenuation is approximately less than 0.5dB / km.

[0100] To form an antiresonant hollow core optical fiber with a gap node type, there is a spacing x between two adjacent first nested rings 21, and x>0.

[0101] When the wall thickness t1 of the first nested ring 21 is less than 1 μm, the value range of the spacing x is: X to 2X;

[0102] in,

[0103] When the wall thickness t1 of the first nested ring 21 is ≥1 μm, the value range of the spacing x is: Y to 2Y;

[0104] in,

[0105] r is the inner radius of the outer cladding 1, N is the number of the first nested rings 21, and n is the refractive index of the material used for the hollow core optical fiber.

[0106] The wall thickness t1 of the first nested ring 21 is determined according to the size of the central angle θ1 formed by the first arc length and the center point P1 of the first nested ring 21 .

[0107] When θ1 / π≤8%, the value range of the wall thickness t1 of the first nested ring 21 is:

[0108]

[0109] When θ1 / π>8%, the value range of the wall thickness t1 of the first nested ring 21 is: 0.2λ~0.8λ, λ is the transmission wavelength of light.

[0110] The transmission wavelength λ can usually be 1.0um, 1.5um, 3.0um, 6.0um, 10.0um, etc.; the first nested ring 21, the second nested ring 22, the third nested ring 23, the auxiliary resonant ring 24 and the area between the first nested ring 21 and the outer cladding 1 are filled with dry gas, and the water vapor content is below ppm or even ppb.

[0111] In the present application, the hollow core optical fiber can be made of quartz, which needs to be coated and then made into an optical cable through a low stress optical cable process.

[0112] The hollow core optical fiber may also be made of polymer material or glass and can be directly used as an optical cable.

[0113] For example, see Figure 4 As shown, the material of the hollow core optical fiber is quartz, the outer cladding 1 is coated with a resin protective layer 4, the outer side of the resin protective layer 4 is provided with a sleeve layer 5, and the outer side of the sleeve layer 5 is provided with a sheath layer 6.

[0114] The resin protective layer 4 includes an inner layer and an outer layer, the modulus of the inner layer is 0.1 MPa to 1.2 MPa, and the modulus of the outer layer is greater than 500 MPa.

[0115] The material of the sleeve layer 5 includes polyurethane TPU, polyester PBT, polyethylene PE, polypropylene PP, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

[0116] Furthermore, an auxiliary reinforcement member is provided between the casing layer 5 and the sheath layer 6.

[0117] The auxiliary reinforcement comprises aramid yarn and / or glass yarn.

[0118] For another example, as an example, the material of the hollow core optical fiber is a polymer material or glass.

[0119] The polymer material includes polystyrene PS, polymethacrylic resin PMMA, polycarbonate PC, polyester PBT, polyethylene PE, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

[0120] The glass includes chalcogenide glass or fluoride glass.

[0121] See also Figure 5 As shown, it is the attenuation curve of the hollow-core optical fiber near 1550nm. It can be seen that the attenuation is basically below 0.5d / km, which means that the hollow-core optical fiber provided in the present application has a low attenuation characteristic due to its stable structure.

[0122] The following is a further detailed description of the present application with reference to some embodiments with reference to the accompanying drawings:

[0123] Implementation 1:

[0124] When there are only the first nested ring and the second nested ring, and the material constituting the optical fiber is quartz material, there are the following embodiments as shown in Table 1:

[0125] Table 1

[0126]

[0127]

[0128] The final form of the optical fiber cable product is a single-core hollow-core optical fiber cable, which is composed of a hollow-core optical fiber, a resin protective layer outside the hollow-core optical fiber, a sleeve layer, and finally a sheath layer. The material of the resin protective layer is an ultraviolet light-cured resin, preferably a polyacrylic resin, and a double-layer coating is adopted. The resin protective layer is divided into an inner layer and an outer layer, and the modulus of the inner layer is between 0.1MPa-1.2MPa, and the modulus of the outer layer is greater than 500MPa; a low-stress optical cable cabling process is adopted for protection, and then a sleeve layer made of polymer material is extruded outside the coated optical fiber. Because the diameter of the optical fiber is larger than that of the conventional solid-core single-mode optical fiber, in order to reduce the stress in the loose sleeve process of the optical fiber and the microbending loss caused by the excess length, the sleeve layer is preferably a polymer extrusion material with a modulus lower than 2000MPa, and the sleeve layer material is modified polypropylene, and the outer diameter of the sleeve is 2.0mm and the inner diameter is 1.3mm. The outer surface of the casing layer is a sheath layer, preferably polyethylene, and the final outer diameter of the optical cable is 3.0 mm and the wall thickness is 0.4 mm. When the optical cable needs to withstand a large tensile force, an auxiliary reinforcement member can also be placed between the casing layer and the sheath layer, preferably a non-metallic yarn, such as aramid yarn or glass fiber yarn.

[0129] It can be seen from the above 10 embodiments that the present application has redesigned the structure of the hollow-core optical fiber. For the hollow-core optical fiber made of quartz material, even if the nested unit has only two nested rings, the attenuation can be as low as 0.041dB / km and the dispersion can be as low as 1.0ps / (nm·km).

[0130] Implementation 2:

[0131] When there are only the first nested ring and the second nested ring, and the material constituting the optical fiber is directly made of a polymer material or glass, there are the following embodiments as shown in Table 2:

[0132] Table 2

[0133]

[0134] The optical fiber made in this way can be used directly. The polymer materials that can be selected to compose the optical fiber include polystyrene PS, polymethacrylate resin PMMA, polycarbonate PC, and hard materials such as PBT, PE, ETFE, PEEK can also be selected to make hollow-core optical fibers, etc. The glass that can be selected includes chalcogenide glass, fluoride glass, etc.

[0135] It can be seen from the above 8 embodiments that the present application has redesigned the structure of the hollow-core optical fiber. For the hollow-core optical fiber made of polymer materials or glass, even if the nested unit has only two nested rings, the attenuation can be as low as 0.041dB / km and the dispersion can be as low as 1.0ps / (nm·km).

[0136] Implementation 3:

[0137] When there are a first nested ring, a second nested ring and a third nested ring, and the material constituting the optical fiber is made directly of a polymer material or glass, there are the following embodiments as shown in Table 3:

[0138] Table 3

[0139]

[0140]

[0141] The optical fiber made in this way can be used directly. The polymer materials that can be selected to compose the optical fiber include polystyrene PS, polymethacrylate resin PMMA, polycarbonate PC, and hard materials such as PBT, PE, ETFE, PEEK can also be selected to make hollow-core optical fibers, etc. The glass that can be selected includes chalcogenide glass, fluoride glass, etc.

[0142] It can be seen from the above 8 embodiments that the present application redesigns the structure of the hollow-core optical fiber for hollow-core optical fibers made of polymer materials or glass. The nested unit includes three nested rings, and the attenuation can be as low as 0.021 dB / km and the dispersion can be as low as 3.0 ps / (nm·km).

[0143] Implementation 4:

[0144] When there are a first nested ring, a second nested ring and a third nested ring, and the material constituting the optical fiber is a quartz material, there are the following embodiments shown in Table 4:

[0145] Table 4

[0146]

[0147]

[0148] The hollow-core optical fiber cable is composed of a hollow-core optical fiber, a resin protective layer outside the hollow-core optical fiber, a sleeve layer after that, and a sheath layer at the end. The material of the resin protective layer is an ultraviolet curing resin, preferably a polyacrylic resin, and a double-layer coating is adopted. The resin protective layer is divided into an inner layer and an outer layer, the modulus of the inner layer is between 0.1MPa-1.2MPa, and the modulus of the outer layer is greater than 500MPa; a low-stress optical cable cabling process is adopted for protection, and then a sleeve layer of a polymer material is extruded outside the coated optical fiber. Because the diameter of the optical fiber is larger than that of the conventional solid-core single-mode optical fiber, in order to reduce the stress in the loose sleeve process of the optical fiber and the microbending loss caused by the excess length, the sleeve layer is preferably a polymer extrusion material with a modulus lower than 2000MPa, and the sleeve layer material is modified polypropylene, the outer diameter of the sleeve is 2.0mm, and the inner diameter is 1.3mm. The outer side of the sleeve layer is a sheath layer, preferably polyethylene, and the final outer diameter of the optical cable is 3.0mm and the wall thickness is 0.4mm. When the optical cable needs to withstand a large tensile force, an auxiliary reinforcement member may also be placed between the sleeve layer and the sheath layer, preferably a non-metallic yarn such as aramid yarn or glass fiber yarn.

[0149] It can be seen from the above 8 embodiments that the present application has redesigned the structure of the hollow-core optical fiber. For the hollow-core optical fiber made of quartz material, the nested unit includes three nested rings, the attenuation can be as low as 0.016 dB / km, and the dispersion can be as low as 3.0 ps / (nm·km).

[0150] 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.

[0151] 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.

[0152] 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 optical fiber, characterized in that: The hollow core optical fiber comprises a cladding region and a core region; The cladding region comprises an outer cladding (1) and an anti-resonance layer (2) arranged in sequence from the outside to the inside; The core region includes a region surrounded by the boundary of the anti-resonance layer (2) and the outer cladding layer (1); The anti-resonance layer (2) comprises a plurality of rotationally symmetrically distributed nested units, the nested units comprising a first nested ring (21) and a second nested ring (22) nested in the first nested ring (21), the first nested ring (21) being connected to the inner wall of the outer cladding (1) with a first arc length, and the second nested ring (22) being connected to the inner wall of the first nested ring (21) with a second arc length at a position where the first nested ring (21) is connected to the inner wall of the outer cladding (1).

2. The hollow core optical fiber according to claim 1, wherein: The central angle formed by the first arc length and the center point P1 of the first nested ring (21) is θ1, and the value range of θ1 / π is 6% to 16%; And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring (22) is θ2, and the value range of θ2 / π is 8% to 24%; and / or, a ratio k1 of an outer radius R2 of the second nested ring (22) to an inner radius r1 of the first nested ring (21) is in the range of 0.45 to 0.6; And / or, the value range of the ratio k2 of the wall thickness t2 of the second nested ring (22) to the wall thickness t1 of the first nested ring (21) is as follows: Wherein, N is the number of the first nested rings (21), and n is the refractive index of the material used for the hollow core optical fiber.

3. The hollow core optical fiber according to claim 1, wherein: The anti-resonance layer (2) further comprises an auxiliary resonant ring (24) arranged between two adjacent nested units, and the outer wall of the auxiliary resonant ring (24) is tangent to the inner wall of the outer cladding layer (1).

4. The hollow core optical fiber according to claim 1, wherein: The nested unit also includes a third nested ring (23), which is nested in the second nested ring (22). The third nested ring (23) is connected to the inner wall of the second nested ring (22) at a position where the second nested ring (22) is connected to the inner wall of the first nested ring (21) with a third arc length.

5. The hollow core optical fiber according to claim 4, characterized in that: The central angle formed by the first arc length and the center point P1 of the first nested ring (21) is θ1, and the value range of θ1 / π is 6% to 16%; And / or, the central angle formed by the second arc length and the center point P2 of the second nested ring (22) is θ2, and the value range of θ2 / π is 8% to 20%; And / or, the central angle formed by the third arc length and the center point P3 of the third nested ring (23) is θ3, and the value range of θ3 / π is 6% to 15%; and / or, a ratio k1 of an outer radius R2 of the second nested ring (22) to an inner radius r1 of the first nested ring (21) is in the range of 0.7 to 0.9; And / or, the wall thickness t2 of the second nested ring (22) has a value ranging from 0.3um to 1.0um; and / or, a ratio of an outer radius R3 of the third nested ring (23) to an inner radius r1 of the first nested ring (21) is in a range of 0.2 to 0.4; And / or, the wall thickness t3 of the third nested ring (23) has a value ranging from 0.2um to 0.5um.

6. The hollow core optical fiber according to claim 4, characterized in that: The anti-resonance layer (2) further comprises an auxiliary resonant ring (24) arranged between two adjacent nested units, and the outer wall of the auxiliary resonant ring (24) is tangent to the inner wall of the outer cladding layer (1).

7. The hollow core optical fiber according to claim 3 or 6, characterized in that: The ratio of the outer radius R6 of the auxiliary resonant ring (24) to the inner radius r1 of the first nested ring (21) is in the range of 0 to 0.4 and is not 0; And / or, the wall thickness t6 of the auxiliary resonant ring (24) has a value ranging from 0.2 um to 0.5 um.

8. The hollow core optical fiber according to any one of claims 1 to 6, characterized in that: The core region comprises an effective core (3), and the effective core (3) is a circular region formed by virtual circles that are simultaneously circumscribed to each of the first nested rings (21); When the transmission wavelength λ of light is 1200nm to 1600nm, the radius r0 of the effective core (3) satisfies: r0=k0×(r-2×R1); Wherein, r is the inner radius of the outer cladding (1), R1 is the outer radius of the first nested ring (21), and k0 is the transmission coefficient, and its value range is as follows: θ1 is the central angle formed by the first arc length and the center point P1 of the first nested ring (21); When the transmission wavelength λ of light is 2um to 11um, the radius r0 of the effective core (3) is in the range of 25um to 250um; When the transmission wavelength λ of light is 200nm-1100nm, the radius r0 of the effective fiber core (3) has a value range of 5um-200um.

9. The hollow core optical fiber according to claim 1, wherein: There is a distance x between two adjacent first nested rings (21), and x>0.

10. The hollow core optical fiber according to claim 9, characterized in that: The wall thickness of the first nested ring (21) is t1=R1-r1, R1 is the outer radius of the first nested ring (21), and r1 is the inner radius of the first nested ring (21); When the wall thickness t1 of the first nested ring (21) is less than 1 μm, the value range of the spacing x is: X to 2X; in, When the wall thickness t1 of the first nested ring (21) is ≥1 μm, the value range of the spacing x is: Y to 2Y; in, r is the inner radius of the outer cladding (1), N is the number of the first nested rings (21), and n is the refractive index of the material used for the hollow core optical fiber.

11. The hollow core optical fiber according to claim 10, characterized in that: The central angle formed by the first arc length and the center point P1 of the first nested ring (21) is θ1; When θ1 / π≤8%, the value range of the wall thickness t1 of the first nested ring (21) is: When θ1 / π>8%, the value range of the wall thickness t1 of the first nested ring (21) is: 0.2λ~0.8λ, λ is the transmission wavelength of light.

12. The hollow core optical fiber according to claim 1, wherein: The hollow-core optical fiber is made of quartz, the outer cladding (1) is coated with a resin protective layer (4), a sleeve layer (5) is arranged outside the resin protective layer (4), and a sheath layer (6) is arranged outside the sleeve layer (5).

13. The hollow core optical fiber according to claim 12, wherein: The resin protective layer (4) comprises an inner layer and an outer layer, the modulus of the inner layer is 0.1 MPa to 1.2 MPa, and the modulus of the outer layer is greater than 500 MPa.

14. The hollow core optical fiber according to claim 12, wherein: The material of the sleeve layer (5) includes polyurethane TPU, polyester PBT, polyethylene PE, polypropylene PP, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

15. The hollow core optical fiber according to claim 12, wherein: An auxiliary reinforcement piece is also provided between the sleeve layer (5) and the sheath layer (6).

16. The hollow core optical fiber according to claim 15, characterized in that: The auxiliary reinforcement comprises aramid yarn and / or glass yarn.

17. The hollow core optical fiber according to claim 1, wherein: The hollow core optical fiber is made of polymer material or glass.

18. The hollow core optical fiber according to claim 17, wherein: The polymer material includes polystyrene PS, polymethacrylic resin PMMA, polycarbonate PC, polyester PBT, polyethylene PE, ethylene-tetrafluoroethylene ETFE or polyetheretherketone PEEK.

19. The hollow core optical fiber according to claim 17, wherein: The glass includes chalcogenide glass or fluoride glass.

20. An optical cable, characterized in that: It comprises the hollow core optical fiber as described in any one of claims 1-19.

Images