Low-additional-loss large-effective-area single-mode optical fiber and preparation method thereof

Abstract

The invention discloses a low-additional-loss large-effective-area single-mode optical fiber and a preparation method thereof.The preparation method comprises the following steps that (1) inert protective gas is introduced into a fiber drawing furnace, meanwhile, an optical fiber preform is subjected to melting and wire drawing through the fiber drawing furnace, a bare optical fiber is obtained, and the flow direction of the inert protective gas is the same as the wire drawing movement direction of the optical fiber preform; (2) the bare optical fiber is pulled out of a lower furnace opening of the fiber drawing furnace and then annealed by a three-section annealing furnace to eliminate residual stress of the optical fiber; (3) coating and curing the bare optical fiber to obtain a finished optical fiber with a coating; and (4) treating the finished optical fiber in a deuterium gas environment for more than 24 hours. The single-mode optical fiber comprises a core layer, a cladding, an inner coating and an outer coating from inside to outside. The single-mode optical fiber prepared by the preparation method has an extremely low additional loss value in a micro-bending state and a cabling process, the attenuation coefficient stability of the optical fiber in cabling, application and other processes can be improved, and the additional loss of the optical fiber is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communication transmission, and particularly relates to a single-mode optical fiber with low additional loss and large effective area and a preparation method thereof. Background Art

[0002] With the rapid construction of 5G infrastructure and the vigorous development of marine communications, long-distance transmission and submarine communication transmission have become the mainstream transmission methods in the current communications industry. Compared with the factory state, the optical fiber is subjected to a series of factors such as bending caused by the excess length of the optical fiber in the large-core optical cable for long-distance transmission, compression between optical fibers, or the constant exposure of the optical cable to ocean currents and water pressure in submarine communications. The pressure, bending, water vapor and other factors in the application will bring the risk of increased attenuation coefficient. With the increase in the optical fiber attenuation coefficient caused by additional loss, the transmission distance is greatly limited, bringing various risks such as increased engineering costs and reduced relay point strength. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a single-mode optical fiber with a large effective area and low additional loss and a preparation method thereof; the preparation method can improve the stability of the attenuation coefficient of the optical fiber during cabling, application, etc., and reduce the additional loss of the optical fiber.

[0004] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0005] A method for preparing a single-mode optical fiber with low additional loss and large effective area comprises the following steps:

[0006] (1) Inert protective gas is introduced into the drawing furnace, and the optical fiber preform is melted and drawn through the drawing furnace to obtain a bare optical fiber, wherein the inert protective gas flows in the same direction as the drawing direction of the optical fiber preform;

[0007] (2) After being drawn out from the lower furnace of the drawing furnace, the bare optical fiber is annealed in a three-stage annealing furnace to eliminate the residual stress of the optical fiber and prevent the glass from cooling suddenly to form micro cracks on the surface of the bare optical fiber;

[0008] (3) coating and curing the bare optical fiber to obtain a finished optical fiber with a coating;

[0009] (4) The finished optical fiber is placed in a deuterium gas environment for more than 24 hours to allow the D2 ions to occupy the empty spaces in the glass chemical bonds in the optical fiber, thereby reducing the additional losses caused by water vapor and other H ions.

[0010] Furthermore, in step (2), the distance between the first section annealing furnace and the lower opening of the wire drawing furnace is 10 cm to 15 cm, the temperature setting range of the three sections annealing furnace is 600 to 1800° C. The relationship between the temperature of the three sections annealing furnace and the wire drawing speed can be referred to the formula:

[0011] T1=V / (1.3~1.8)*D1 / 125-(L1-15)*120*0.13;

[0012] T2=V / (1.27~1.74)*D1 / 125;

[0013] T3 = V (1.23 ~ 1.68) * D1 / 125;

[0014] Where, T1 is the temperature of the first annealing furnace; V is the fiber drawing speed, D1 is the fiber outer diameter, T2 is the temperature of the second annealing furnace, T3 is the temperature of the third annealing furnace; L1 is the distance between the first annealing furnace and the lower mouth of the drawing furnace.

[0015] Furthermore, in step (3), after coating and curing treatment, two layers of coating are formed, namely an inner coating and an outer coating; after coating the inner coating, the diameter of the optical fiber is 180 to 205 microns; after coating the outer coating, the diameter of the optical fiber is 235 to 260 microns; the ratio of the thickness of the inner coating to the thickness of the outer coating is 1.2 to 1.4.

[0016] Furthermore, in step (3), the coating material is selected from epoxy acrylic resin as a prepolymer, and the coating coating also contains one or more of a photosensitizer, a tackifier, an inhibitor, and a leveling agent.

[0017] Furthermore, the resin modulus of the inner coating layer is 0.2 to 2.0 MPa, and the resin modulus of the outer coating layer is 400 to 1500 MPa.

[0018] Furthermore, in step (4), the deuterium concentration in the deuterium environment is 1.5% to 3%, the deuterium pressure is 40 to 50 KPa, and the deuterium temperature is 30° C. to 40° C.

[0019] Furthermore, in step (4), the deuterium concentration is inversely proportional to the optical fiber drawing speed.

[0020] Furthermore, the deuterium concentration and deuterium treatment temperature can refer to the formula:

[0021] C=(7.668-0.001224*V-0.0333*T)*9 / t;

[0022] Wherein, C is the deuterium concentration; V is the fiber drawing speed (800-2500 m / min), T is the deuterium treatment temperature (25-50°C), and t is the deuterium treatment time.

[0023] The present invention further provides a single-mode optical fiber with low additional loss and large effective area, which is prepared by the above preparation method; the single-mode optical fiber comprises a core layer, a cladding layer, an inner coating layer and an outer coating layer from the inside to the outside.

[0024] Beneficial effects of the present invention:

[0025] The present invention sets a three-step gradual annealing process, clearly defines the temperature of each annealing furnace and the optical fiber drawing speed, and can fully release the stress of the optical fiber at different drawing speeds to reduce the additional attenuation of the optical fiber caused by the internal lattice residual stress in subsequent applications.

[0026] The present invention achieves the protective effect of the coating on the optical fiber by setting the ratio of the inner coating thickness to the outer coating thickness of the optical fiber, and defines the resin modulus of the inner coating and the outer coating. The inner coating uses a low-modulus resin to resist the additional attenuation of the optical fiber caused by factors such as bending and lateral pressure. Compared with the inner coating, the outer coating uses a higher-modulus resin to resist the additional attenuation of the optical fiber caused by factors such as stretching and friction.

[0027] The present invention defines environmental conditions such as temperature and pressure when the optical fiber is treated with deuterium gas, as well as the usage ratio of deuterium gas at different drawing speeds, so that the optical fiber can be fully treated in the deuterium gas environment, so that D2 ions occupy the spaces in the glass chemical bonds in the optical fiber, and the additional losses caused by water vapor and H ions are reduced during the application of the optical fiber.

[0028] Compared with the additional loss values ​​of different processes in the cabling process of conventional optical fibers of the same type, the additional loss of the present invention is less than or equal to 0.003dB / km, which is much smaller than the conventional optical fibers of the same type. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of a single-mode optical fiber with low additional loss and large effective area according to the present invention.

[0030] Figure 2 The figure shows the comparison of the additional loss of the low additional loss, large effective area single-mode optical fiber of the present invention and the conventional optical fiber during the cabling process.

[0031] Figure 3 The low excess loss large effective area single mode optical fiber of the present invention is compared with the hydrogen aging excess loss of conventional optical fiber. DETAILED DESCRIPTION

[0032] The technical solutions in the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The present invention provides a method for preparing a single-mode optical fiber with low additional loss and large effective area, comprising the following steps:

[0034] (1) Inert protective gas is introduced into the drawing furnace, and the optical fiber preform is melted and drawn through the drawing furnace to obtain a bare optical fiber, wherein the inert protective gas flows in the same direction as the drawing direction of the optical fiber preform;

[0035] (2) After being drawn out from the lower furnace of the drawing furnace, the bare optical fiber is annealed in a three-section annealing furnace to eliminate the residual stress of the optical fiber and prevent the glass from being suddenly cooled to form micro cracks on the surface of the bare optical fiber; the distance between the first section annealing furnace and the lower furnace of the drawing furnace is 10 cm to 15 cm, and the temperature setting range of the three-section annealing furnace is 600 to 1800 °C. The relationship between the temperature of the three-section annealing furnace and the drawing speed can be referred to the formula:

[0036] T1=V / (1.3~1.8)*D1 / 125-(L1-15)*120*0.13;

[0037] T2=V / (1.27~1.74)*D1 / 125;

[0038] T3 = V (1.23 ~ 1.68) * D1 / 125;

[0039] Where, T1 is the temperature of the first annealing furnace; V is the fiber drawing speed, D1 is the outer diameter of the fiber, T2 is the temperature of the second annealing furnace, T3 is the temperature of the third annealing furnace; L1 is the distance between the first annealing furnace and the lower opening of the drawing furnace;

[0040] (3) The bare optical fiber is subjected to coating and curing treatment to obtain a finished optical fiber with a coating; after the coating and curing treatment, two coating layers are formed, namely an inner coating layer and an outer coating layer; after the inner coating layer is coated, the diameter of the optical fiber is 180 to 205 microns; after the outer coating layer is coated, the diameter of the optical fiber is 235 to 260 microns; the ratio of the thickness of the inner coating layer to the thickness of the outer coating layer is 1.2 to 1.4; the coating material is selected from epoxy acrylic resin as a prepolymer, and the coating coating also contains one or more of a photosensitizer, a tackifier, an inhibitor, and a leveling agent; the resin modulus of the inner coating layer is 0.2 to 2.0 MPa, and the resin modulus of the outer coating layer is 400 to 1500 MPa.

[0041] (4) The finished optical fiber is placed in a deuterium gas environment for more than 24 hours, so that the D2 ions occupy the empty spaces in the glass chemical bonds in the optical fiber, reducing the additional losses caused by water vapor and other H ions; wherein the deuterium concentration in the deuterium gas environment is 1.5% to 3%, and the deuterium concentration is inversely proportional to the optical fiber drawing speed; the deuterium concentration, temperature, and optical fiber drawing speed can refer to the formula C = (7.668-0.001224*V-0.0333*T)*9 / t, wherein C is the deuterium concentration; V is the optical fiber drawing speed (800 to 2500 m / min), T is the deuterium treatment temperature, and t is the deuterium treatment time. The deuterium pressure in the deuterium gas environment is 40 to 50 Kpa, and the deuterium temperature is 30°C to 40°C. The deuterium gas environment is provided by a deuterium gas tank or a deuterium gas box storing deuterium gas.

[0042] The present invention further provides a single-mode optical fiber with low additional loss and large effective area obtained by the above-mentioned preparation method. Figure 1 As shown, the single-mode optical fiber includes a core layer 1, a cladding layer 2, an inner coating layer 3 and an outer coating layer 4 from the inside to the outside.

[0043] Example

[0044] This embodiment provides a method for preparing a single-mode optical fiber with low additional loss and large effective area, comprising the following steps:

[0045] (1) Inert protective gas is introduced into the drawing furnace, and the optical fiber preform is melted and drawn through the drawing furnace to obtain a bare optical fiber, wherein the inert protective gas flows in the same direction as the drawing direction of the optical fiber preform; the drawing speed of this step is 2200 mpm;

[0046] (2) After being drawn out from the lower furnace of the drawing furnace, the bare optical fiber is annealed in a three-stage annealing furnace to eliminate the residual stress of the optical fiber. The relationship between the temperature of the three-stage annealing furnace and the drawing speed can be referred to the formula:

[0047] T1=V / (1.3~1.8)*D1 / 125-(L1-15)*120*0.13

[0048] T2=V / (1.27~1.74)*D1 / 125

[0049] T3=V(1.23~1.68)*D1 / 125

[0050] Where, T1 is the temperature of the first annealing furnace; V is the fiber drawing speed, D1 is the outer diameter of the fiber, T2 is the temperature of the second annealing furnace, T3 is the temperature of the third annealing furnace; L1 is the distance between the first annealing furnace and the lower opening of the drawing furnace;

[0051] (3) coating and curing the bare optical fiber to obtain a finished optical fiber with a coating; after the coating and curing treatment, two coating layers are formed, namely, an inner coating layer and an outer coating layer; after the inner coating layer is coated, the diameter of the optical fiber is 190 microns; after the outer coating layer is coated, the diameter of the optical fiber is 245 microns; the ratio of the thickness of the inner coating layer to the thickness of the outer coating layer is 1.25; the coating material is selected from epoxy acrylic resin as a prepolymer; the resin modulus of the inner coating layer is 2.0 MPa, and the resin modulus of the outer coating layer is 400-1500 MPa;

[0052] (4) The finished optical fiber is placed in a deuterium gas box for treatment for 48 hours; the deuterium concentration in the deuterium gas environment is 1.8%, and the deuterium concentration is inversely proportional to the drawing speed; the deuterium pressure in the deuterium gas environment is 45 Kpa, and the deuterium temperature is 30°C.

[0053] The single-mode optical fiber of this embodiment is cabled with a conventional optical fiber, and the additional loss of each cabling process is compared. Figure 2 As shown, compared with the additional loss values ​​of different processes in the cabling process of conventional optical fibers of the same type, the additional loss of the present invention is less than or equal to 0.003dB / km, which is much smaller than the conventional optical fibers of the same type.

[0054] The additional loss of the single-mode optical fiber of this embodiment and the conventional optical fiber after hydrogen aging is compared. Figure 3 The single-mode optical fiber of the present invention has good low additional loss performance in a hydrogen atmosphere. By comparing the additional attenuation after aging in a 1% concentration hydrogen environment, the additional loss of the single-mode optical fiber of the present invention is much smaller than that of similar products.

[0055] The single-mode optical fiber of the present invention uses a fixed diameter cylinder method to test the additional loss of 1550nm wavelength microbend to be less than or equal to 0.02dB / km. When used in LW optical cables, the additional loss of 1550nm wavelength using a 12-core / tube process is less than or equal to 0.001dB / km, the additional loss of 24-48 cores / tube is less than or equal to 0.003dB / km, and the additional loss of 1550nm wavelength is less than or equal to 0.004dB / km for more than 48 cores / tube. The effective area at 1550nm wavelength is 90-150um^2, and it has good attenuation stability, which is very suitable for long-distance, large-capacity transmission optical cables and optical cables with multiple cores.

[0056] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a single-mode optical fiber with low additional loss and large effective area, characterized in that: The steps include: (1) Inert protective gas is introduced into the drawing furnace, and the optical fiber preform is melted and drawn through the drawing furnace to obtain a bare optical fiber, wherein the inert protective gas flows in the same direction as the drawing direction of the optical fiber preform; (2) After the bare optical fiber is drawn out from the lower furnace of the drawing furnace, it is annealed in a three-section annealing furnace to eliminate the residual stress of the optical fiber; (3) coating and curing the bare optical fiber to obtain a finished optical fiber with a coating; (4) The finished optical fiber is placed in a deuterium gas environment for treatment for more than 24 hours.

2. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: In step (2), the distance between the first section annealing furnace and the lower opening of the wire drawing furnace is 10 cm to 15 cm, and the temperature setting range of the three sections annealing furnace is 600 to 1800° C. The relationship between the temperature of the three sections annealing furnace and the wire drawing speed can be referred to the formula: T1=V / (1.3~1.8)*D1 / 125-(L1-15)*120*0.13; T2=V / (1.27~1.74)*D1 / 125; T3 = V (1.23 ~ 1.68) * D1 / 125; Where, T1 is the temperature of the first annealing furnace; V is the fiber drawing speed, D1 is the fiber outer diameter, T2 is the temperature of the second annealing furnace, T3 is the temperature of the third annealing furnace; L1 is the distance between the first annealing furnace and the lower mouth of the drawing furnace.

3. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: In step (3), after coating and curing treatment, two layers of coating are formed, namely, an inner coating and an outer coating; after coating the inner coating, the diameter of the optical fiber is 180 to 205 microns; after coating the outer coating, the diameter of the optical fiber is 235 to 260 microns; the ratio of the thickness of the inner coating to the thickness of the outer coating is 1.2 to 1.

4.

4. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: In step (3), the coating material is selected from epoxy acrylic resin as a prepolymer, and the coating paint also contains one or more of a photosensitizer, a tackifier, an inhibitor, and a leveling agent.

5. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: The resin modulus of the inner coating is 0.2 to 2.0 MPa, and the resin modulus of the outer coating is 400 to 1500 MPa.

6. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: In step (4), the deuterium gas concentration in the deuterium gas environment is 1.5% to 3%, the deuterium gas pressure is 40 to 50 KPa, and the deuterium gas temperature is 30° C. to 40° C.

7. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 1, characterized in that: In step (4), the deuterium concentration is inversely proportional to the optical fiber drawing speed.

8. The method for preparing a single-mode optical fiber with low additional loss and large effective area according to claim 7, characterized in that: Deuterium concentration and deuterium treatment temperature can refer to the formula: C=(7.668-0.001224*V-0.0333*T)*9 / t; Wherein, C is the deuterium concentration; V is the fiber drawing speed (800-2500 m / min), T is the deuterium treatment temperature, and t is the deuterium treatment time.

9. A single-mode optical fiber with low additional loss and large effective area, characterized in that: It is made by the preparation method described in any one of claims 1 to 8; the single-mode optical fiber comprises a core layer, a cladding layer, an inner coating layer and an outer coating layer from the inside to the outside.

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