A low-attenuation non-zero dispersion shift single-mode optical fiber and its applications

Abstract

This invention relates to a low-attenuation non-zero dispersion-shifted single-mode optical fiber and its applications. The fiber comprises a first core layer, a second core layer, and a third core layer, a recessed cladding, an auxiliary cladding, and a first outer cladding. The first core layer has a radius R1 of 0.8–1.3 μm and a relative refractive index difference Δ1 of -0.01%–0.05%. The second core layer has a radius R2 of 1.5–1.8 μm and a relative refractive index difference Δ2 of -0.12%–0.15%. The third core layer has a radius R3 of 2.0–2.5 μm and a relative refractive index difference Δ3 of -0.34%–0.30%. The recessed cladding has a radius R4 of 5–6.5 μm and a relative refractive index difference Δ4 of -0.51%–0.57%. The fiber core layer of this invention has a three-core structure, which reduces interlayer stress during fiber drawing. Combined with the near-zero relative refractive index difference of the core layers, it reduces core layer distortion and lowers fiber attenuation.

Description

Technical Field

[0001] This invention belongs to the field of optical communication technology, specifically relating to a low-attenuation non-zero dispersion-shifted single-mode optical fiber and its applications. Background Technology

[0002] With the rapid development of 5G construction globally, optical communication networks are evolving towards longer distances, higher capacity, and higher speeds. As communication networks move towards next-generation systems, fiber optic infrastructure with large transmission capacity is the foundation of these next-generation networks. Optical communication, characterized by its large transmission capacity, long transmission distance, and high transmission speed, is widely used in long-haul trunk lines, metropolitan area networks (MANs), and access networks. Optical fiber meeting ITU-T G.655 standards is commonly referred to as non-zero dispersion-shifted fiber. Its core design focuses on optimizing dense wavelength division multiplexing (DWDM) systems. G.655 fiber is an excellent choice for high-capacity, long-distance MAN core or regional aggregation links, especially in DWDM deployment scenarios. Simultaneously, it has wide applications in submarine cable systems and MAN core layers.

[0003] The attenuation coefficient of optical fiber is one of its most important performance indicators, largely determining the relay distance in optical fiber communication. In long-distance optical fiber transmission, the smaller the attenuation coefficient, the farther the optical signal can be transmitted, thus reducing the operating cost of optical communication. Therefore, reducing optical power loss and mitigating the impact of optical fiber nonlinear effects have become the development direction of optical fiber communication.

[0004] The main component of optical fiber is high-purity SiO2. The optical fiber is drawn from an optical fiber preform. The internal structure of the optical fiber preform is divided into a core layer and a cladding layer. The core layer has a higher refractive index, while the cladding layer has a lower refractive index. Light mainly propagates in the optical fiber core layer. Germanium is usually added to the core layer to increase the glass refractive index, while fluorine is usually added to the cladding layer to reduce the refractive index, thereby obtaining a suitable refractive index difference and achieving the required optical communication performance.

[0005] Currently, non-zero dispersion-shifted single-mode fiber is widely used in communication networks. However, patent applications for this type of fiber rarely mention fiber attenuation. The attenuation of mainstream non-zero dispersion-shifted single-mode fiber at 1550 is generally 0.190-0.210 dB / km, which is relatively high.

[0006] Patent CN1068434C remains the design basis for mainstream G.655 optical fiber. This product has a high attenuation value, with ATT1550 at 0.195-0.21 dB / km.

[0007] Patent CN119758515A uses a gradient core layer to increase the mode field diameter and reduce attenuation to 0.180-0.185 dB / km, but the attenuation of this product is not low enough and does not reach within 0.180 dB / km.

[0008] Therefore, it is necessary to design a low-attenuation, non-zero dispersion-shifted single-mode fiber. Summary of the Invention

[0009] The following are definitions and explanations of some terms used in this invention:

[0010] Starting from the fiber core axis, the layer closest to the axis is defined as the core layer based on the change in refractive index, and the second outer cladding layer of the fiber, namely the pure silicon dioxide layer, is defined as the fiber.

[0011] The relative refractive index difference Δi between the layers of an optical fiber is defined by the following equation.

[0012] △i =(n i -n c )*100% / n c

[0013] in The refractive index of the specified layer, and is the refractive index of pure silicon dioxide.

[0014] The relative refractive index contribution of Ge doping in the fiber core Defined by the following equation,

[0015] ;

[0016] in Assuming the Ge dopant in the fiber core, how much does it cause a change in the refractive index of silica glass when incorporated into pure silica without other dopants? This represents the refractive index of the first outer cladding layer, i.e., the refractive index of pure silicon dioxide. The relative refractive index contribution of fluorine doping has the same meaning. The ratio of the mass of phosphorus doped to the mass of the glass is the proportion of phosphorus, denoted as np (in wt%).

[0017] The technical problem to be solved by the present invention is to propose a low-loss non-zero dispersion shift single-mode optical fiber and its application, which addresses the shortcomings of the existing technology.

[0018] The technical solution adopted in this invention is as follows:

[0019] A low-attenuation, non-zero dispersion-shifted single-mode optical fiber includes a core layer and a cladding layer surrounding the core layer. The core layer, from the inside out, consists of a first core layer, a second core layer, and a third core layer. The cladding layer, from the inside out, consists of a recessed cladding layer, an auxiliary cladding layer, and a first outer cladding layer. The second outer cladding layer is a pure silica glass layer. The radius R1 of the first core layer is 0.8~1.3 μm, and the relative refractive index difference Δ1 is -0.01%~0.05%. The radius R2 of the second core layer is 1.5~1.8 μm, and the relative refractive index difference Δ2 is -0.12%~0.15%. The radius R3 of the third core layer is 2.0~2.5 μm, and the relative refractive index difference Δ3 is -0.34%. The radius of the sunken cladding layer R4 is 5~6.5μm, and the relative refractive index difference Δ4 is ​​-0.51%~-0.57%. The radius of the auxiliary cladding layer R5 is 9~11μm, and the relative refractive index difference Δ5 is -0.30%~-0.36%. The radius of the first outer cladding layer R6 is 15~18μm, and Δ6 is -0.42%~-0.50%. The second outer cladding layer is a pure silica glass layer.

[0020] According to the above technical solution, the radius ratio R3:R2:R1 of the third core layer, the second core layer, and the first core layer is 2.7-3.2:1.9-2.3:1.

[0021] According to the above technical solution, the relative refractive index difference Δ1 of the first core layer is -0.01~0.05%, and the relative refractive index contribution of fluorine doping in the first core layer is -0.03~-0.05wt%.

[0022] According to the above technical solution, the relative refractive index difference Δ2 of the second core layer is -0.12% to 0.15%, and the relative refractive index contribution of germanium doping in the second core layer is 0.02-0.06wt%.

[0023] According to the above technical solution, the relative refractive index difference Δ3 of the third core layer is -0.34% to -0.30%, and the relative refractive index contribution of germanium doping in the third core layer is 0.03-0.08wt%.

[0024] According to the above technical solution, the sunken cladding, auxiliary cladding, and first outer cladding are all pure fluorine-doped layers and do not contain germanium.

[0025] According to the above technical solution, the second outer cladding layer is a pure silicon dioxide glass layer, Δ7≈0, r7=62.5μm.

[0026] According to the above technical solution, the first core layer contains phosphorus doping, and the corresponding optical fiber preform is prepared by PCVD process. The phosphorus doping is introduced by the carrier gas during the PCVD deposition of the core layer. The three core layers are doped with different concentrations of phosphorus: the phosphorus doping concentration of the first core layer is 0.05-0.1%, the phosphorus doping concentration of the second core layer is 0.01-0.05%, and the phosphorus doping concentration of the third core layer is 0.005%-0.01%.

[0027] According to the above technical solution, the first core layer, the second core layer and the third core layer adopt gradient phosphorus doping, with the first core layer having the highest phosphorus doping concentration, and the phosphorus doping concentration of the second core layer and the third core layer decreasing sequentially.

[0028] According to the above technical solution, the cable cutoff wavelength of the optical fiber is equal to or less than 1450nm.

[0029] According to the above technical solution, the dispersion of the optical fiber at a wavelength of 1550nm is equal to or less than 6.0 ps / nm*km and equal to or greater than 2.0 ps / nm*km, and the dispersion slope of the optical fiber at a wavelength of 1550nm is less than 0.084ps / nm2*km.

[0030] According to the above technical solution, the attenuation of the optical fiber at a wavelength of 1550nm is equal to or less than 0.180dB / km; under preferred conditions, it is equal to or less than 0.178dB / km.

[0031] According to the above technical solution, the attenuation of the optical fiber at a wavelength of 1625nm is equal to or less than 0.2dB / km; under preferred conditions, it is equal to or less than 0.195dB / km.

[0032] An application of a low-attenuation, non-zero dispersion-shifted single-mode optical fiber, which is used in laser, communication, or sensing fields.

[0033] The beneficial effects of the present invention are:

[0034] 1. The fiber core has a three-layer structure, which reduces the interlayer stress during fiber drawing and brings the relative refractive index difference of the core layer close to 0. This reduces core layer distortion, lowers the Rayleigh scattering coefficient of the fiber, and thus reduces fiber attenuation.

[0035] 2. The optical fiber adopts a design with a recessed cladding and an auxiliary cladding to ensure that the optical fiber has a suitable cutoff wavelength for cabling.

[0036] 3. The relative refractive index difference decreases stepwise from the inside to the outside from the core layer to the inner cladding, reducing abrupt changes and facilitating a reasonable viscosity transition at the interface, reducing fiber stress, improving fiber performance, and reducing attenuation.

[0037] 4. The addition of phosphorus doping to the core layer can soften the silica glass network, thereby optimizing the core layer viscosity. With the help of a well-designed core-cladding structure, the Rayleigh scattering coefficient of the optical fiber can be reduced, and attenuation can be further reduced.

[0038] 5. The gradient phosphorus doping of the first, second, and third core layers is designed to reduce interlayer stress compared to phosphorus doping with the same concentration, while ensuring the highest phosphorus doping concentration in the innermost first core layer. This reduces Rayleigh scattering and attenuation in the first core layer where optical power is most concentrated. Therefore, the gradient phosphorus doping design is beneficial for reducing fiber attenuation. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a cross-sectional structural diagram of the refractive index of the first embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] like Figure 1As shown, this embodiment provides a low-attenuation non-zero dispersion-shifted single-mode optical fiber, comprising a core layer and a cladding layer surrounding the core layer. The core layer, from the inside out, consists of a first core layer, a second core layer, and a third core layer. The cladding layer, from the inside out, consists of a recessed cladding layer, an auxiliary cladding layer, and a first outer cladding layer. The second outer cladding layer is a pure silica glass layer. The radius R1 of the first core layer is 0.8~1.3μm, and the relative refractive index difference Δ1 is -0.01%~0.05%. The radius R2 of the second core layer is 1.5~1.8μm, and the relative refractive index difference Δ2 is -0.12%~0.15%. The radius R3 of the third core layer is 2.0~2.5μm, and the relative refractive index difference Δ3 is -0.34%. The recessed cladding radius R4 is 5~6.5μm, and the relative refractive index difference Δ4 is ​​-0.51%~-0.57%. The auxiliary cladding radius R5 is 9~11μm, and the relative refractive index difference Δ5 is -0.30%~-0.36%. The first outer cladding radius R6 is 15~18μm, and Δ6 is -0.42%~-0.50%. The second outer cladding is a pure silica glass layer, and Δ7 is 0. The fiber core of this invention has a three-core structure, which reduces interlayer stress during fiber drawing. Combined with the near-zero relative refractive index difference of the core layers, core layer distortion and fiber attenuation can be reduced.

[0043] The radius ratio R3:R2:R1 of the third core layer, the second core layer, and the first core layer is 2.7-3.2:1.9-2.3:1. Preferably, R3:R2:R1 ≈ 3:2:1.

[0044] The relative refractive index difference Δ1 of the first core layer is between -0.01 and 0.05%, and the relative refractive index contribution of fluorine doping in the first core layer is between -0.03 and -0.05%; preferably between -0.035% and 0.045%.

[0045] The relative refractive index difference Δ2 of the second core layer is -0.12% to 0.15%, and the relative refractive index contribution of germanium doping in the second core layer is 0.02-0.06wt%; preferably 0.03-0.05wt%.

[0046] The relative refractive index difference Δ3 of the third core layer is -0.34% to -0.30%, and the relative refractive index contribution of germanium doping in the third core layer is 0.03-0.08wt%; preferably 0.04-0.07wt%.

[0047] The sunken cladding, auxiliary cladding, and first outer cladding are all pure fluorine-doped layers and do not contain germanium.

[0048] The second outer cladding layer is a pure silica glass layer, Δ7≈0, r7=62.5μm.

[0049] The first core layer contains phosphorus doping, and the corresponding optical fiber preform is prepared using the PCVD process. The phosphorus doping is introduced by the carrier gas during the PCVD deposition of the core layer. The three core layers are doped with different concentrations of phosphorus: the first core layer has a phosphorus doping concentration of 0.05-0.1%, the second core layer has a phosphorus doping concentration of 0.01-0.05%, and the third core layer has a phosphorus doping concentration of 0.005%-0.01%. Phosphorus doping can appropriately increase the delta value of the core layer and effectively reduce optical fiber attenuation.

[0050] Since optical transmission primarily occurs in the core layer, phosphorus doping softens the silica glass network, reducing Rayleigh scattering and thus lowering fiber attenuation. The first, second, and third core layers employ gradient phosphorus doping, with the highest concentration in the first layer, decreasing sequentially in the second and third. For example, the first core layer might have np = 0.05 wt%, the second np = 0.03 wt%, and the third np = 0.008 wt%. This gradient phosphorus doping reduces interlayer stress compared to equal concentrations of phosphorus doping, while ensuring the highest phosphorus doping concentration in the innermost first core layer. In this core layer where optical power is most concentrated, Rayleigh scattering and attenuation are reduced. Therefore, gradient phosphorus doping is beneficial for reducing fiber attenuation.

[0051] This embodiment also provides an application of a low-attenuation non-zero dispersion-shifted single-mode fiber, which is used in laser, communication, or sensing fields.

[0052] Tables 1 and 2 describe the parameters of specific embodiments 1 to 11. As can be seen from Tables 1 and 2, the cabling cutoff wavelength of the optical fiber is equal to or less than 1450 nm. The dispersion of the optical fiber at a wavelength of 1550 nm is equal to or less than 6.0 ps / nm*km and equal to or greater than 2.0 ps / nm*km. The dispersion slope of the optical fiber at a wavelength of 1550 nm is less than 0.084 ps / nm²*km, preferably 0.075 ps / nm²*km. The attenuation of the optical fiber at a wavelength of 1550 nm is equal to or less than 0.180 dB / km; under preferred conditions, it is equal to or less than 0.178 dB / km. The attenuation of the optical fiber at a wavelength of 1625 nm is equal to or less than 0.2 dB / km; under preferred conditions, it is equal to or less than 0.195 dB / km.

[0053] Table 1

[0054]

[0055] Table 2

[0056]

[0057] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A low-attenuation, non-zero dispersion-shifted single-mode optical fiber, comprising a core and a cladding surrounding the core, characterized in that: The core layers, from the inside out, are a first core layer, a second core layer, and a third core layer; the cladding layers, from the inside out, are a recessed cladding layer, an auxiliary cladding layer, a first outer cladding layer, and a second outer cladding layer. The radius R1 of the first core layer is 0.8~1.3μm, and the relative refractive index difference Δ1 is -0.01%~0.05%; the radius R2 of the second core layer is 1.5~1.8μm, and the relative refractive index difference Δ2 is -0.12%~0.15%; the radius R3 of the third core layer is 2.0~2.5μm, and the relative refractive index difference Δ3 is -0.34%~-0.30%; the radius R4 of the recessed cladding layer is 5~6.5μm, and the relative refractive index difference Δ4 is ​​-0.51%~-0.57%; the radius R5 of the auxiliary cladding layer is 9~11μm, and the relative refractive index difference Δ5 is -0.30%. The first cladding layer has a radius R6 of 15-18 μm and a Δ6 of -0.42% to -0.50%. The second cladding layer is a pure silica glass layer. The first core layer contains phosphorus doping. The corresponding optical fiber preform is prepared by PCVD process. The phosphorus doping is introduced by the carrier gas during the PCVD deposition of the core layer. The three core layers are doped with different concentrations of phosphorus: the phosphorus doping concentration of the first core layer is 0.05-0.1 wt%, the phosphorus doping concentration of the second core layer is 0.01-0.05 wt%, and the phosphorus doping concentration of the third core layer is 0.005%-0.01 wt%.

2. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1, characterized in that: The radius ratio R3:R2:R1 of the third core layer, the second core layer, and the first core layer is 2.7-3.2:1.9-2.3:

1.

3. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The relative refractive index difference Δ1 of the first core layer is between -0.01 and 0.05%, and the relative refractive index contribution of fluorine doping in the first core layer is between -0.03 and -0.05%.

4. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The relative refractive index difference Δ2 of the second core layer is -0.12% to 0.15%, and the relative refractive index contribution of germanium doping in the second core layer is 0.02-0.06%.

5. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The relative refractive index difference Δ3 of the third core layer is -0.34% to -0.30%, and the relative refractive index contribution of germanium doping in the third core layer is 0.03-0.08%.

6. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The sunken cladding, auxiliary cladding, and first outer cladding are all pure fluorine-doped layers.

7. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The second outer cladding layer is a pure silica glass layer, Δ7≈0, R7=62.5μm.

8. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1, characterized in that: The first, second, and third core layers are graded phosphorus doping, with the highest phosphorus concentration in the first core layer and decreasing phosphorus concentration in the second and third core layers respectively.

9. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The cable cutoff wavelength of the optical fiber is equal to or less than 1450nm.

10. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The optical fiber has a dispersion at a wavelength of 1550 nm that is equal to or less than 6.0 ps / nm*km and equal to or greater than 2.0 ps / nm*km, and the dispersion slope at a wavelength of 1550 nm is less than 0.084 ps / nm. 2 *km.

11. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The optical fiber has an attenuation of 0.180 dB / km at a wavelength of 1550 nm.

12. The low-attenuation non-zero dispersion-shifted single-mode optical fiber according to claim 1 or 2, characterized in that: The optical fiber has an attenuation of 0.2 dB / km at a wavelength of 1625 nm.

13. An application of a low-attenuation non-zero dispersion-shifted single-mode optical fiber as described in any one of claims 1 to 12, characterized in that: The optical fiber is used in laser, communication, or sensing fields.

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