A high-element doped optical fiber with stable attenuation and its preparation method

Abstract

This invention discloses a highly element-doped optical fiber with stable attenuation, comprising a core rod, a recessed cladding, and an outer cladding. The core rod is manufactured by sintering, degassing, and stretching a deposited loose body prepared by vapor deposition. The deposited loose body comprises, from the inside out, a core layer, a soft layer, a core-cladding bonding layer, a first cladding layer, and a second cladding layer. The thickness of the core-cladding bonding layer is 0–3 mm, the thickness of the soft layer is 0–2 mm, and the density distribution of each layer of the deposited loose body satisfies the following condition: ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max This represents the maximum deposition density of the loose deposit. This invention reduces bond breakage defects during subsequent deformation by controlling the density distribution and thickness of the deposited loose deposit, thereby reducing fiber attenuation after deuterium treatment.

Description

Technical Field

[0001] This invention relates to the field of optical fiber technology, specifically to a highly element-doped optical fiber with stable attenuation and its preparation method. Background Technology

[0002] In certain special optical fibers, such as those highly doped with a certain element, a phenomenon often occurs during attenuation testing after fiber drawing: the attenuation at the 1310nm, 1383nm, and 1550nm bands is normal for the large-diameter fiber, but after deuterium treatment, the attenuation at the short wavelengths of 1310nm and 1383nm increases significantly for the small-diameter fiber, while the attenuation at the long wavelength of 1550nm remains essentially unchanged. This phenomenon may be caused by defects (non-bridging oxygen hollow defects (NBOHC), E' center defects, peroxide free radicals, etc.) arising from the breakage of the peroxide bonds (-OO-) or chemical bonds (Ge-O-Ge, Si-O-Si, Si-O-Ge) in the fiber preform during preform shrinkage, stretching, and fiber drawing. During deuterium treatment, if the defect concentration reaches a certain level, deuterium molecules will form relatively strong bonds with the defects, leaving some deuterium molecules inside the fiber and causing increased attenuation at short wavelengths.

[0003] Highly doped optical fiber products, such as G657.A2 optical fiber, are prone to forming weak chemical bonds due to the large amount of specific element doping. This increases the probability of bond breakage and defects, leading to increased attenuation. Similarly, some products with complex manufacturing processes undergo repeated stretching during production, which can also damage chemical bonds and cause the aforementioned phenomena.

[0004] Traditional methods to improve the increased attenuation of optical fibers after deuterium treatment mainly focus on reducing the peroxide bonds in the fiber preform core layer. Since peroxide groups are prone to breakage and forming defects, it is necessary to carefully control the sintering atmosphere and the amount of helium, oxygen, and chlorine. This method has been verified to be effective, but a balance point needs to be reached. Otherwise, the three types of defects—non-bridged oxygen hollow defects (NBOHC), E' center defects, and peroxide free radicals—may interact and still affect fiber attenuation. On the other hand, the main approach is to control the drawing speed, cooling method, and drawing tension. However, reducing the drawing speed and increasing the annealing furnace will affect fiber production capacity and drawing costs, which has certain drawbacks.

[0005] Chinese patent CN108751750A provides a method for stabilizing optical fiber attenuation. This method involves adding a nitrogen heating process after deuterium treatment of the optical fiber. Heating the deuterium-treated fiber effectively releases excess deuterium molecules, thus stabilizing attenuation. While this method removes most of the additional attenuation, a small amount (approximately 0.003 dB / km @ 1310 nm) remains due to the strong bond between deuterium and defects. This residual attenuation can negatively impact fiber performance. Furthermore, the nitrogen heat treatment process prolongs the fiber product turnover cycle, increases the difficulty of on-site management, and raises costs. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a highly element-doped optical fiber with stable attenuation and its fabrication method. The present invention reduces the attenuation of the optical fiber after deuterium treatment by monitoring and adjusting the density distribution and thickness of the deposited loose bulk material in the core rod, thereby reducing bond breakage defects during subsequent deformation.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0008] This invention provides a highly element-doped optical fiber with stable attenuation, comprising a core rod, a recessed cladding, and an outer cladding. The core rod is manufactured by sintering, degassing, and stretching a deposited loose body prepared by vapor deposition. The deposited loose body comprises, from the inside out, a core layer, a soft layer, a core-cladding bonding layer, a first cladding layer, and a second cladding layer. The thickness of the core-cladding bonding layer is 0–3 mm, and the thickness of the soft layer is 0–2 mm. The density distribution of each layer of the deposited loose body satisfies the following condition: the densities of the core layer, the core-cladding bonding layer, the first cladding layer, and the second cladding layer are respectively expressed as ρ. 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max This represents the maximum sedimentary density of the loose sedimentary body.

[0009] Furthermore, the overall density of the deposited loose mass is 0.200–0.400 g / cm³. 3 .

[0010] Furthermore, the deposited loose body is deposited using axial vapor deposition or external vapor deposition processes.

[0011] Furthermore, the sunken cladding is formed by shrinking using a sleeve method.

[0012] Furthermore, the outer cladding layer is deposited using an OVD deposition process.

[0013] Furthermore, the core rod comprises a core layer and an inner cladding layer according to the refractive index distribution, wherein the inner cladding layer is made of a soft layer of deposited loose material, a core-cladding bonding layer, cladding layer one, and cladding layer two.

[0014] Furthermore, the core layer is germanium-doped or germanium-chlorine co-doped with a refractive index of 0.0040 to 0.0060, the inner cladding layer is fluorine-doped with a refractive index of -0.0004 to -0.0020, the sunken cladding layer is fluorine-doped with a refractive index between -0.0060 and -0.0030, and the outer cladding layer is a pure silicon layer with a refractive index of 0 to 0.0004.

[0015] Furthermore, the core-to-core ratio of the core rod is 2.2 to 3.0, the core-to-core ratio of the sunken cladding layer to the core layer is 3.8 to 5.5, and the core-to-core ratio of the outer cladding layer to the core layer is 14 to 20.

[0016] Furthermore, after deuterium treatment, the attenuation increase of this highly element-doped optical fiber with stable attenuation is less than 0.02 dB / km in the 1310 nm and 1383 nm bands, while the attenuation in the 1550 nm band remains unchanged.

[0017] Another aspect of the present invention provides a method for preparing a highly element-doped optical fiber with stable attenuation, comprising the following steps:

[0018] (1) A loose sedimentary body is prepared using vapor deposition. During the deposition process, the amount of fuel gas is controlled to ensure that the density distribution of each layer of the formed loose sedimentary body meets the following conditions: the densities of the core layer, core-cladding layer, cladding layer one, and cladding layer two are expressed as ρ 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max The maximum sedimentary density of the loose sedimentary body;

[0019] (2) The deposited loose material is processed into a core rod by sintering, degassing and stretching processes;

[0020] (3) A recessed cladding is prepared on the outside of the core rod, an outer cladding is prepared on the outside of the recessed cladding, and then the optical fiber preform is sintered.

[0021] (4) The fiber preform obtained in step (3) is drawn into a high element doped fiber with stable attenuation.

[0022] The beneficial effects of this invention are:

[0023] This invention controls the density distribution of the deposited loose material by monitoring and adjusting the core rod to satisfy the following condition: ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 By controlling the thickness of the deposited loose body and reducing the generation of bond breakage defects during subsequent deformation, the fiber attenuation after deuterium treatment can be reduced.

[0024] This invention also optimizes stress distribution and achieves viscosity matching by controlling the refractive index profile distribution of each layer, forming a certain refractive index gradient between the sunken cladding and the inner and outer cladding, thereby reducing the stress on the core layer during the drawing process, reducing core layer defects, and achieving the goal of reducing deuterium decay.

[0025] After deuterium treatment, the attenuation increase of this highly element-doped optical fiber with stable attenuation is less than 0.02 dB / km in the 1310 nm and 1383 nm bands, while the attenuation in the 1550 nm band remains unchanged. Attached Figure Description

[0026] Figure 1 This is a density curve of the deposited loose material according to an embodiment of the present invention.

[0027] Figure 2 This is a density curve of a comparative sedimentary loose body. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a highly element-doped optical fiber with stable attenuation, comprising a core rod, a recessed cladding, and an outer cladding. The core rod is manufactured by sintering, degassing, and stretching a deposited loose body produced by vapor deposition. The deposited loose body comprises, from the inside out, a core layer, a soft layer, a core-cladding bonding layer, a first cladding layer, and a second cladding layer. The thickness of the core-cladding bonding layer is 0–3 mm, the thickness of the soft layer is 0–2 mm, and the thicknesses of the remaining core layers and cladding layers vary depending on the product and the core-cladding ratio. The density distribution of each layer of the deposited loose body satisfies the following condition: the densities of the core layer, the core-cladding bonding layer, the first cladding layer, and the second cladding layer are expressed as ρ. 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max This represents the maximum sedimentary density of the loose sedimentary body.

[0030] The overall density of the sedimentary loose mass is 0.200–0.400 g / cm³. 3 .

[0031] The deposited loose body is deposited using axial vapor deposition or external vapor deposition processes.

[0032] The sunken cladding is preferably formed by sleeve melting and shrinking; the outer cladding is preferably formed by OVD deposition process.

[0033] The core rod comprises a core layer and an inner cladding layer according to the refractive index distribution, wherein the inner cladding layer is made of a soft layer of deposited loose material, a core-cladding layer, cladding layer one, and cladding layer two.

[0034] The core layer is germanium-doped or germanium-chlorine co-doped with a refractive index of 0.0040 to 0.0060; the inner cladding layer is fluorine-doped with a refractive index of -0.0004 to -0.0020; the sunken cladding layer is fluorine-doped with a refractive index between -0.0060 and -0.0030; and the outer cladding layer is a pure silicon layer with a refractive index of 0 to 0.0004.

[0035] The core-to-core ratio of the core rod is 2.2 to 3.0, the core-to-core ratio of the sunken cladding layer to the core layer is 3.8 to 6.0, and the core-to-core ratio of the outer cladding layer to the core layer is 14 to 20.

[0036] After being treated with deuterium, the attenuation increase of this highly doped optical fiber in the 1310nm and 1383nm bands is less than 0.02dB / km, while the attenuation in the 1550nm band remains unchanged.

[0037] Another aspect of the present invention provides a method for preparing a highly element-doped optical fiber with stable attenuation, comprising the following steps:

[0038] (1) A deposited loose body is prepared using a vapor phase deposition process. Specifically, the deposited loose body is obtained by gradually depositing "powder" layer by layer through a flame hydrolysis reaction of gaseous halides (SiCl4, GeCl4, etc.) carried in an oxyhydrogen flame or a methane flame. During the deposition process, the amount of fuel gas is controlled so that the density distribution of each layer of the formed deposited loose body meets the following conditions: the densities of the core layer, the core-cladding layer, the first cladding layer, and the second cladding layer are expressed as ρ 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max This represents the maximum sedimentary density in the loose sedimentary mass.

[0039] (2) The deposited loose material is processed into a core rod by sintering, degassing and stretching processes;

[0040] (3) A cladding layer is prepared on the outside of the core rod, and an outer cladding layer is prepared on the outside of the cladding layer. Then, the fiber preform is formed by sintering. The cladding layer is preferably formed by the sleeve method, that is, the core rod is fitted with a sleeve and then shrunk. The outer cladding layer is preferably formed by the OVD deposition process.

[0041] (4) The fiber preform obtained in step (3) is drawn into a high element doped fiber with stable attenuation.

[0042] Example

[0043] A loose deposited mass was prepared using VAD (Axial Vapor Deposition), followed by sintering, degassing, and stretching to form a core rod. A fused-in cladding layer was deposited using the RIC (Rack-In-Cylinder) method, and then deposited using OVD (Optical Vapor Deposition). The deposited cladding was then sintered to form an optical fiber preform, which was subsequently drawn into an optical fiber. The loose deposited mass comprises, from the inside out, a core layer, a soft layer, a core-cladding bonding layer, cladding layer one, and cladding layer two. The core rod consists of a core layer and an inner cladding layer according to their refractive index distribution. During the deposition process, the density distribution of each layer is controlled by adjusting the amount of fuel gas (H2 or CH4). Figure 1 As shown, the density curve is obtained through industrial computed tomography (CT) technology, or through continuous measurement and calculation of the weight of the loose material obtained by a weighing sensor and the diameter of the loose material fed back by a laser diameter gauge.

[0044] The relevant parameters of the optical fiber in this embodiment are as follows: the core refractive index is 0.0055, the inner cladding refractive index is -0.0003, the depressed cladding refractive index is -0.0048, and the outer cladding refractive index is 0.0003; the core-to-core ratio (the ratio of the diameter of the core to the inner cladding) is 2.47, the ratio of the depressed cladding to the core is 5.18, and the ratio of the outer cladding to the core is 17.9.

[0045] Density distribution of the deposited loose material of the mandrel is shown in the figure. Figure 1 The core-encapsulation bonding layer has a thickness of 0.78 mm, and the soft layer has a thickness of 0.59 mm.

[0046] The optical fiber in this embodiment was fabricated using a drawing process with assisted annealing at a speed of 2000 m / min. The attenuation of the optical fiber was tested using PK8000. The attenuation in the 1310 nm, 1383 nm, and 1550 nm bands before and after deuterium treatment is shown in Table 1 below. The attenuation was relatively stable before and after deuterium treatment, with little change.

[0047] Table 1. Attenuation data before and after deuterium gas treatment in the examples.

[0048]

[0049] Comparative Example

[0050] A loose deposited mass was prepared using VAD (Axial Vapor Deposition), followed by sintering, degassing, and stretching to form a core rod. A fused-in cladding layer was deposited using the RIC (Rack-In-Cylinder) method, and then deposited using OVD (Optical Vapor Deposition). The deposited cladding was then sintered to form an optical fiber preform, which was subsequently drawn into an optical fiber. The loose deposited mass comprises, from the inside out, a core layer, a soft layer, a core-cladding bonding layer, cladding layer one, and cladding layer two. The core rod consists of a core layer and an inner cladding layer according to their refractive index distribution. During the deposition process, the density distribution of each layer is controlled by adjusting the amount of fuel gas (H2 or CH4). Figure 2 As shown.

[0051] The relevant parameters of the optical fiber in this comparative example are as follows: core refractive index is 0.0053, inner cladding refractive index is -0.0004, depressed cladding refractive index is -0.0049, and outer cladding refractive index is 0.0003; core-to-core ratio (diameter ratio of core to inner cladding) is 2.50, the ratio of depressed cladding to core is 4.19, and the ratio of outer cladding to core is 18.1.

[0052] Density distribution of the deposited loose material of the mandrel is shown in the figure. Figure 2 The core-packing bonding layer has a thickness of 4.05 mm, and the soft layer has a thickness of 1.55 mm.

[0053] The optical fiber used in this comparative example was fabricated using a drawing process with assisted annealing at a speed of 2000 m / min. The fiber attenuation was tested using a PK8000. The attenuation at the 1310 nm, 1383 nm, and 1550 nm bands before and after deuterium treatment is shown in Table 2. After deuterium treatment, the attenuation at the 1310 nm and 1383 nm bands increased significantly, while the attenuation at 1550 nm did not change significantly. The increased thickness of the core-cladding layer is attributed to the increased attenuation of the fiber after deuterium treatment.

[0054] Table 2 Comparative data on attenuation before and after deuterium gas treatment

[0055]

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A highly element-doped optical fiber with stable attenuation, characterized in that, The material includes a core rod, a recessed cladding layer, and an outer cladding layer. The core rod is manufactured using a vapor deposition process followed by sintering, degassing, and stretching. The deposited loose body comprises, from the inside out, a core layer, a soft layer, a core-cladding layer, a first cladding layer, and a second cladding layer. The core-cladding layer has a thickness of 0–3 mm, and the soft layer has a thickness of 0–2 mm. The density distribution of each layer of the deposited loose body satisfies the following condition: the densities of the core layer, the core-cladding layer, the first cladding layer, and the second cladding layer are expressed as ρ. 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max This represents the maximum sedimentary density of the loose sedimentary body.

2. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, The overall density of the sedimentary loose mass is 0.200–0.400 g / cm³. 3 .

3. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, The deposited loose body is deposited using axial vapor deposition or external vapor deposition processes.

4. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, The sunken cladding is formed by shrinking using a sleeve method.

5. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, The outer cladding layer is deposited using an OVD deposition process.

6. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, The core rod comprises a core layer and an inner cladding layer according to the refractive index distribution, wherein the inner cladding layer is made of a soft layer of deposited loose material, a core-cladding layer, cladding layer one, and cladding layer two.

7. The attenuation-stable highly element-doped optical fiber according to claim 6, characterized in that, The core layer is germanium-doped or germanium-chlorine co-doped with a refractive index of 0.0040 to 0.0060; the inner cladding layer is fluorine-doped with a refractive index of -0.0004 to -0.0020; the sunken cladding layer is fluorine-doped with a refractive index between -0.0060 and -0.0030; and the outer cladding layer is a pure silicon layer with a refractive index of 0 to 0.0004.

8. The attenuation-stable highly element-doped optical fiber according to claim 6, characterized in that, The core-to-core ratio of the core rod is 2.2 to 3.0, the core-to-core ratio of the sunken cladding layer to the core layer is 3.8 to 5.5, and the core-to-core ratio of the outer cladding layer to the core layer is 14 to 20.

9. The attenuation-stable highly element-doped optical fiber according to claim 1, characterized in that, After deuterium treatment, the attenuation increase of this highly element-doped optical fiber with stable attenuation is less than 0.02 dB / km in the 1310 nm and 1383 nm bands, while the attenuation in the 1550 nm band remains unchanged.

10. A method for fabricating a highly element-doped optical fiber with stable attenuation, characterized in that, Includes the following steps: (1) A loose sedimentary body is prepared using vapor deposition. During the deposition process, the amount of fuel gas is controlled to ensure that the density distribution of each layer of the formed loose sedimentary body meets the following conditions: the densities of the core layer, core-cladding layer, cladding layer one, and cladding layer two are expressed as ρ 芯层 ρ 芯包结合层 ρ 包层一 ρ 包层二 , ρ 芯层 <ρ 包层一 , ρ 芯层 ≥ρ 包层二 , ρ max -ρ 芯包结合层 <ρ max -ρ 包层一 , where ρ max The maximum sedimentary density of the loose sedimentary body; (2) The deposited loose material is processed into a core rod by sintering, degassing and stretching processes; (3) A recessed cladding is prepared on the outside of the core rod, an outer cladding is prepared on the outside of the recessed cladding, and then the optical fiber preform is sintered. (4) The fiber preform obtained in step (3) is drawn into a high element doped fiber with stable attenuation.

Images