Low-loss single-mode optical fiber

Abstract

The application provides a low-loss single-mode optical fiber, relates to the technical field of communication optical fibers, and aims to solve the technical problem of large attenuation of a single-mode optical fiber.The low-loss single-mode optical fiber comprises a core layer and a cladding layer surrounding the periphery of the core layer, the core layer comprises an inner core layer and an outer core layer, the inner core layer is doped with P and GeO2, and the outer core layer is doped with F, P and GeO2.By adjusting the doped elements in the inner core layer and the outer core layer, Rayleigh scattering is reduced, so that the attenuation coefficient of the optical fiber is reduced, and under the premise of compatibility of international standards of various performances of the optical fiber, the optical fiber has lower attenuation loss and better bending resistance.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication technology, and in particular to a low-loss single-mode optical fiber. Background Technology

[0002] Optical fiber is the transmission medium for optical fiber communication networks. The lower the fiber attenuation, the less optical power loss will be in the entire link, and a longer relay-free transmission distance can be achieved during transmission, which can effectively reduce the cost of network and system construction.

[0003] The main component of optical fiber is SiO2. When manufacturing optical fiber preforms, GeO2 is added to increase the refractive index of the core layer, which is the main source of reducing optical fiber attenuation. At the same time, F element can be added to the cladding to reduce the refractive index of the cladding, ensuring the refractive index difference between the core layer and the cladding, and further reducing optical fiber attenuation.

[0004] However, in the above technical solution, the viscosity / thermal expansion coefficient between the core layer and the cladding layer is reversed during the manufacturing of the optical fiber preform, resulting in an imbalance in the viscosity / thermal expansion coefficient of the optical fiber structure. This leads to significant stress at the interface between the core layer and the cladding layer, which in turn increases optical fiber attenuation. Summary of the Invention

[0005] In view of the above problems, this application provides a low-loss single-mode optical fiber to solve the technical problem of high fiber attenuation in single-mode optical fibers in related technologies.

[0006] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0007] This application provides a low-loss single-mode optical fiber, which includes a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer and an outer core layer. The inner core layer is doped with P and GeO2, and the outer core layer is doped with F, P, and GeO2.

[0008] In one possible implementation, the inner core layer is doped with 0.10-1.5% GeO2 and 0.01-0.3% P; the outer core layer is doped with 0.10-1.5% GeO2, 0.01-0.3% P, and 0-1.5% F.

[0009] In one possible implementation, the refractive index of the core layer has a parabolic gradient distribution.

[0010] In one possible implementation, the cladding layer comprises an inner cladding layer, a first recessed layer, a doped layer, a second recessed layer, and an outer cladding layer, stacked sequentially from the center to the periphery; the inner cladding layer is doped with 0-0.2% GeO2, 0.01-0.3% P, and 0.5-1.5% F; the first recessed layer is doped with 0-0.2% GeO2 and 0-2.0% F; the doped layer is doped with 0-0.2% GeO2 and 0-2.0% F; and the second recessed layer is doped with 0-0.2% GeO2 and 0-3.0% F.

[0011] In one possible implementation, the relative refractive index difference Δ1 between the inner core layer and the outer cladding layer is 0.10-0.25%; the relative refractive index difference Δ2 between the outer core layer and the outer cladding layer is 0-0.20%; the relative refractive index difference Δ3 between the inner cladding layer and the outer cladding layer is -0.10 to -0.30%; the relative refractive index difference Δ4 between the first recessed layer and the outer cladding layer is -0.25 to -0.50%; the relative refractive index difference Δ5 between the doped layer and the outer cladding layer is -0.30 to -0%; and the relative refractive index difference Δ6 between the second recessed layer and the outer cladding layer is -0.50-0%.

[0012] In one possible implementation, the radius R1 of the inner core layer is 2-6 μm; the radius of the outer core layer is R2, with R2-R1 ranging from 3.0-5.0 μm; the radius of the inner cladding layer is R3, with R3-R2 ranging from 2-5 μm; the radius of the first recessed layer is R4, with R4-R3 ranging from 2-8 μm; the radius of the doped layer is R5, with R5-R4 ranging from 5-30 μm; the radius of the second recessed layer is R6, with R6-R5 ranging from 10-22 μm; and the radius R7 of the outer cladding layer is 60-65 μm.

[0013] In one possible implementation, the low-loss single-mode fiber is used in the wavelength range of 1310-1550 nm.

[0014] In one possible implementation, the low-loss single-mode fiber has a mode field diameter of 8.7-9.7 μm at an application wavelength of 1310 nm; and the low-loss single-mode fiber has a mode field diameter of 9.5-10.5 μm at an application wavelength of 1550 nm.

[0015] In one possible implementation, the low-loss single-mode fiber has an attenuation coefficient ≤0.350dB / km at an application wavelength of 1310nm; and an attenuation coefficient ≤0.175dB / km at an application wavelength of 1550nm.

[0016] In one possible implementation, the low-loss single-mode fiber has a zero-dispersion wavelength range of 1300-1324 nm, and the dispersion slope of the low-loss single-mode fiber at the zero-dispersion wavelength is ≤0.092 ps / (nm). 2 The low-loss single-mode fiber has a dispersion coefficient of ≤18ps / (nm*km) at the application wavelength of 1550nm.

[0017] This application provides a low-loss single-mode optical fiber, comprising a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer and an outer core layer. The inner core layer is doped with P and GeO2, while the outer core layer is doped with F, P, and GeO2. Through reasonable fiber structure design and control of core layer doping elements, Rayleigh scattering is reduced while maintaining the core rod cross-sectional structure, thereby achieving the goal of reducing the fiber attenuation coefficient. Furthermore, while ensuring that all fiber performance is compatible with the G.652 standard, the fiber exhibits lower attenuation loss and superior bending resistance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the cross-section of a low-loss single-mode optical fiber provided for an embodiment of this application;

[0020] Figure 2 A schematic cross-sectional view of the low-loss single-mode optical fiber provided in the embodiments of this application;

[0021] Figure 3 A schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber provided in Embodiment 1 of this application;

[0022] Figure 4 A comparative schematic diagram of stress distribution in a low-loss single-mode optical fiber according to Embodiment 1 provided in this application.

[0023] Figure 5 A schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber provided for the implementation of this application in Embodiment 4;

[0024] Figure 6 A schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber provided in Embodiment 5 of this application;

[0025] Figure 7 A schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber provided in Embodiment Six of this application.

[0026] Figure label:

[0027] 100: Inner core layer;

[0028] 200: Outer core layer;

[0029] 300: Inner cladding;

[0030] 400: First recessed layer;

[0031] 500: Doped layer;

[0032] 600: Second recessed layer;

[0033] 700: Outer layer. Detailed Implementation

[0034] As described in the background section, single-mode fibers in related technologies suffer from high fiber attenuation. Research by engineers has revealed that this problem arises because existing low-loss, bend-insensitive single-mode fiber profiles are designed to balance doping levels and silica viscosity to achieve lower attenuation. The fiber core typically uses co-doped Ge and F elements. Since F doping reduces the core refractive index, more Ge is needed to maintain the core refractive index. However, more Ge doping leads to increased scattering. Simultaneously, the attenuation, dispersion parameters, mode field diameter, and cable wavelength of low-loss cutoff wavelength-shifted single-mode fibers are also affected by the core structure. Existing core profiles employ a step-type design, resulting in significant stress abrupt changes between the core and cladding, leading to high attenuation. Furthermore, when adjusting the core cross-sectional structure, all parameters change synchronously, making it difficult for various indicators to meet the G.652 standard (the G.652 standard specifies the characteristics and performance of single-mode fiber (SMF), including mode distribution, mode distribution constant, maximum attenuation, maximum refractive index change, tensile strength, and heat distortion temperature). To ensure that all parameters are compatible with the G.652 standard, the depth and width design values ​​of the ring core recess are limited, resulting in limited improvement in the fiber's bending resistance and making it difficult to meet the G.657 bending loss standard.

[0035] Furthermore, existing low-loss cutoff wavelength shifting single-mode fibers, after the core rod profile is finalized, are directly drawn into pure silicon ferrules, making it difficult to adjust the cutoff wavelength shift position. This results in a narrow applicable wavelength range for preform-drawn fibers. To address these technical issues, this application provides a low-loss single-mode fiber. Through reasonable fiber structure design, core layer doping control, and outer core layer doping control, the fiber exhibits lower attenuation loss and superior bending resistance while maintaining compatibility with the G.652 standard. Simultaneously, without changing the core rod profile structure, the cutoff wavelength shift position can be controlled by adjusting the refractive index of the F-doped interlayer tube used for drawing, allowing the drawn fiber to be adjusted to different wavelength ranges and further improving bending performance.

[0036] To make the above-mentioned objectives, features, and advantages of the embodiments of this application more apparent and understandable, 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 a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] This application provides a low-loss single-mode optical fiber, as referenced. Figure 1 and Figure 2 , Figure 1 A schematic diagram of the cross-section of a low-loss single-mode optical fiber provided in an embodiment of this application. Figure 2 This is a schematic cross-sectional view of a low-loss single-mode optical fiber provided in an embodiment of this application. The low-loss single-mode optical fiber includes a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer 100 and an outer core layer 200. The cladding layer includes an inner cladding layer 300, a first recessed layer 400, a doped layer 500, a second recessed layer 600, and an outer cladding layer 700, stacked sequentially from the center to the outer periphery. In this embodiment, the radius R1 of the inner core layer 100 can be 2-6 μm, and the radius of the outer core layer 200 is R2. The distance between R2 and R1... The radius of the inner cladding layer 300 is 3.0-5.0 μm; the radius of the inner cladding layer 300 is R3, and the range of R3-R2 is 2-5 μm; the radius of the first recessed layer 400 is R4, and the range of R4-R3 is 2-8 μm; the radius of the doped layer 500 is R5, and the range of R5-R4 is 5-30 μm; the radius of the second recessed layer 600 is R6, and the range of R6-R5 is 10-22 μm; the radius of the outer cladding layer 700 is R7, which is 60-65 μm, and the radius of the outer cladding layer 700 R7 can be 62.5 μm.

[0038] The refractive index is changed by doping the inner core layer 100 with GeO2 and P elements, wherein the inner core layer 100 is doped with GeO2 with a molar concentration of 0.10-1.5% and P elements with a molar concentration of 0.01-0.3%.

[0039] The refractive index is changed by doping the outer core layer 200 with GeO2, P element and F element, wherein the outer core layer 200 is doped with GeO2 with a molar concentration of 0.10-1.5%, P element with a molar concentration of 0.01-0.3% and F element with a molar concentration of 0-1.5%.

[0040] The refractive index is changed by doping the inner cladding 300 with GeO2, P and F elements, wherein the inner cladding 300 is doped with GeO2 at a molar concentration of 0-0.2%, P at a molar concentration of 0.01-0.3%, and F at a molar concentration of 0.5-1.5%.

[0041] The refractive index is changed by doping GeO2 and F elements in the first recessed layer 400, wherein the first recessed layer 400 is doped with GeO2 with a molar concentration of 0-0.2% and F elements with a molar concentration of 0-2.0%.

[0042] The refractive index is changed by doping GeO2 and F elements in the doped layer 500, wherein the doped layer 500 is doped with GeO2 with a molar concentration of 0-0.2% and F elements with a molar concentration of 0-2.0%.

[0043] The refractive index is changed by doping GeO2 and F elements in the second recessed layer 600, wherein the second doped layer is doped with GeO2 with a molar concentration of 0-0.2% and F elements with a molar concentration of 0-3.0%.

[0044] This results in a parabolic gradient distribution of the refractive index of the core layer, enabling a gradual change in physical properties and doping concentration. It also eliminates or reduces the interfacial stress difference between the core and cladding layers, and reduces the dispersion value by 1550 while keeping the mode field diameter constant to meet the requirements of the G652 standard.

[0045] It should be noted that the relative refractive index difference Δ1 between the inner core layer 100 and the outer cladding layer 700 can also be maintained between 0.10 and 0.25%, the relative refractive index difference Δ2 between the outer core layer 200 and the outer cladding layer 700 can be maintained between 0 and 0.20%, the relative refractive index difference Δ3 between the inner cladding layer 300 and the outer cladding layer 700 can be maintained between -0.10 and -0.30%, the relative refractive index difference Δ4 between the first recessed layer 400 and the outer cladding layer 700 can be maintained between -0.25 and -0.50%, the relative refractive index difference Δ5 between the doped layer 500 and the outer cladding layer 700 can be maintained between -0.30 and -0%, and the relative refractive index difference Δ6 between the second recessed layer 600 and the outer cladding layer 700 can be maintained between -0.50 and 0%.

[0046] The aforementioned refractive index allows the application wavelength range of single-mode optical fiber to remain between 1310-1550 nm.

[0047] Specifically, for single-mode fiber used at a wavelength of 1310 nm, the mode field diameter is 8.7-9.7 μm, preferably 9.2 μm, and the attenuation coefficient is ≤0.350 dB / km; the attenuation coefficient can also be 0.290 dB / km. For single-mode fiber used at a wavelength of 1550 nm, the mode field diameter is 9.5-10.5 μm, preferably 10.5 μm, and the attenuation coefficient is ≤0.175 dB / km; the attenuation coefficient can also be ≤0.165 dB / km. All performance indicators are compatible with G.652 and G.657A2 standards.

[0048] The aforementioned refractive index also allows the zero-dispersion wavelength range of single-mode fiber to be maintained between 1300-1324 nm; specifically, at the zero-dispersion wavelength, the dispersion slope of the single-mode fiber is ≤0.092 ps / (nm). 2 *km); the dispersion coefficient of single-mode fiber at the application wavelength of 1550nm is ≤18ps / (nm*km).

[0049] It should be noted that the molar concentration of phosphorus (P) doping is below 0.3%, and co-doping with fluorine (F) can essentially eliminate the influence of the P absorption peak at 1570 nm on the attenuation of the fiber waveguide from 1530 to 1625 nm. When the molar concentration of P doping is below 0.3%, and the P-doped single-mode fiber is treated with deuterium, the hydrogen aging resistance of the single-mode fiber is basically the same as that of ordinary single-mode fiber without P doping, meeting the standard requirements.

[0050] Simultaneously, the profile structure design was achieved by adjusting the flow ratios of SiO2, GeO2, F, and P elements during the deposition process. The principle for GeO2 doping was to minimize its doping amount to reduce Rayleigh scattering loss caused by GeO2 doping. Since trace amounts of P doping in the core layer replaced the effect of F doping on core layer viscosity adjustment, without changing the refractive index difference between the core and cladding layers, the amount of GeO2 doped in the core layer could be further reduced by not doping F, thereby reducing Rayleigh scattering.

[0051] The low-loss single-mode fiber of this application includes a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer 100 and an outer core layer 200. The cladding layer includes an inner cladding layer 300, a first recessed layer 400, a doped layer 500, a second recessed layer 600, and an outer cladding layer 700, stacked sequentially from the center to the outer periphery. The inner core layer 100 is doped with P and GeO2, the outer core layer 200 is doped with F, P, and GeO2, the inner cladding layer 300 is doped with GeO2, P, and F, the first recessed layer 400 is doped with GeO2 and F, the doped layer 500 is doped with GeO2 and F, and the second recessed layer 600 is doped with GeO2 and F. Through reasonable fiber structure design and core layer doping control, while keeping the core cross-sectional structure unchanged, Rayleigh scattering is reduced by adjusting the elements doped in the inner and outer core layers, thereby achieving the purpose of reducing the fiber attenuation coefficient.

[0052] Meanwhile, by adjusting the refractive index of the F-doped interlayer tube used for matching fiber drawing, the position of the cutoff wavelength shift is controlled, allowing the drawn fiber to be adjusted to different wavelength ranges. Under the premise that the fiber performance is compatible with the G.652 standard, the fiber has lower attenuation loss and better bending resistance.

[0053] It should be noted that the low-loss single-mode fiber provided in this application has a doped layer 500 and a second recessed layer 600 near the outer cladding 700. On the one hand, it can effectively reduce the refractive index of the core layer and reduce Rayleigh scattering loss caused by GeO2 doping while preventing optical power leakage. On the other hand, while ensuring that the refractive index of the core rod remains unchanged, the cutoff wavelength shift position can be adjusted by adjusting the refractive index of the second recessed layer 600. The fiber can be used in a wide wavelength range of 1260-1625nm (O+S+L band), which reduces the manufacturing process difficulty of the differentiated design of the fiber preform.

[0054] In addition to controlling the position of the cutoff wavelength shift, the cutoff wavelength of the low-loss single-mode fiber in this embodiment can be adjusted according to the application band to obtain optimal bending performance, provided that other major properties (MFD, dispersion performance) match G652.

[0055] For example, when used in the O-band, the cable cutoff wavelength is ≤1260nm; when used in the C+L band, the cable cutoff wavelength is ≤1530nm; and when used in the S+C+L band, the cutoff wavelength is ≤1420nm.

[0056] It should also be noted that the inner core layer 100 and outer core layer 200 of the low-loss single-mode fiber provided in this application replace the effect of F element doping on viscosity adjustment with trace amount of P element doping. While keeping the core layer refractive index unchanged, the amount of GE doping in the core layer is effectively reduced, thereby reducing Rayleigh scattering.

[0057] Furthermore, the low-loss single-mode fiber provided in this application has a core layer with a parabolic gradient design, which can achieve a gradual change in physical properties and doping concentration, eliminate or reduce the interfacial stress difference between the core and cladding layers, and reduce the 1550 dispersion value to meet the requirements of the G652 standard while keeping the mode field diameter unchanged.

[0058] In this embodiment, the outer cladding layer 700 is made of pure silicon dioxide and is not doped with other elements.

[0059] In this embodiment, the outer core layer 200 is a silicon dioxide glass layer doped with GeO2, P and F elements.

[0060] In this embodiment of the application, the low-loss single-mode optical fiber is suitable for various manufacturing processes or hybrid processes such as MCVD and PCVD.

[0061] In this embodiment of the application, the cutoff wavelength shift position of the low-loss single-mode optical fiber is adjustable (≤1530nm).

[0062] It should be noted that when using single-mode fiber at a wavelength of 1550nm, the macrobending loss of 15mm radius - 10 turns is ≤0.03dB; the macrobending loss of 10mm radius - 1 turn is ≤0.1dB; and the macrobending loss of 7.5mm radius - 1 turn is ≤0.5dB.

[0063] The low-loss single-mode optical fiber of this application will be described in detail below through Examples 1 to 6.

[0064] Pre-formed mandrels are prepared using an improved in-tube chemical vapor deposition (MCVD) or plasma chemical vapor deposition (PCVD) process. The doped layer 500 can be composed of an fluorine-doped quartz tube as the deposition substrate. SiCl4 and O2 are used as raw materials for SiO2, SiF4, SF6, C2F6 or CF4 are used as raw materials for fluorine doping, GECl4 is used as raw material for GE doping, and POCl3 is used as raw material for phosphorus doping.

[0065] Using a reciprocating hydrogen-oxygen torch or plasma as a heat source, and by controlling the concentration of each dopant element inside the tube, a recessed layer, an inner cladding layer, an outer core layer, and an inner core layer are sequentially deposited on the inner surface of the fluorine-doped tube. Then, the deposition tube is melted down to a suitable inner diameter at high temperature. Before the inner diameter is completely closed, SF6 or C2F6 and O2 are introduced and the impurities adhering to the inner diameter surface are etched away under the heating of a hydrogen-oxygen torch or a graphite furnace. Finally, the tube is melted down at high temperature to form a solid core rod.

[0066] An optical fiber is obtained by matching and drawing an F-doped quartz sleeving as the second recessed layer 600 and a pure quartz sleeving as the outer cladding layer 700, and then drawing the fiber at high temperature.

[0067] The optical fiber cross-sectional structure includes an inner core layer 100, an outer core layer 200, an inner cladding layer 300, a first recessed layer 400, a doped layer 500, a second recessed layer 600, and an outer cladding layer 700. The inner core layer 100 has a radius of R1 and a relative refractive index difference of Δ1; the outer core layer 200 has a radius of R2 and a relative refractive index difference of Δ2; the inner cladding layer 300 has a radius of R3 and a relative refractive index difference of Δ3; the first recessed layer 400 has a radius of R4 and a relative refractive index difference of Δ4; the doped layer 500 has a radius of R5 and a relative refractive index difference of Δ5; the second recessed layer 600 has a radius of R6 and a relative refractive index difference of Δ5; and the outer cladding layer 700 is pure silicon dioxide with a radius R7 of 62.5 μm and a relative refractive index difference of 0%.

[0068] Table 1 Fiber parameters for different structural designs

[0069]

[0070] Table 2. Distribution of dopant element concentration in optical fibers with different structural designs

[0071]

[0072] Table 3 Test performance of optical fibers with different structural parameters

[0073]

[0074] The testing standard for MFD (mode field diameter) is: "GBT-15972.45-2008 Fiber Optic Test Method Specification Part 45: Measurement and Test Methods and Procedures for Transmission Characteristics and Optical Characteristics - Mode Field Diameter".

[0075] Cable cutoff wavelength testing standard: GBT-15972.44-2008 Fiber Optic Test Method Specification Part 44: Measurement, Test Methods and Test Procedures for Transmission Characteristics and Optical Characteristics - Cutoff Wavelength.

[0076] Attenuation coefficient testing standard: "GBT-15972.40-2008 Fiber Optic Test Method Specification Part 40: Measurement and Test Methods and Procedures for Transmission Characteristics and Optical Characteristics (Attenuation)".

[0077] Macrobending loss testing standard: "GBT-15972.47-2008 Fiber Optic Test Method Specification Part 47: Measurement and Test Methods and Procedures for Transmission Characteristics and Optical Characteristics Macrobending Loss".

[0078] Dispersion testing standard: GB / T-15972.42-2008 Fiber Optic Test Method Specification Part 42: Measurement, Test Methods and Procedures for Transmission Characteristics and Optical Characteristics (Wavelength Dispersion).

[0079] The hydrogen aging resistance of the optical fibers obtained in Examples 1 to 6 was tested. The testing methods are shown in Table 4, and the test results are shown in Table 5.

[0080] Table 4. Methods for detecting hydrogen aging resistance

[0081] Benchmark Method 1 kPa (0.01 atm) +23℃±5℃ Approximately (4-6) days Alternative methods 1 kPa (0.01 atm) +65℃±2℃ More than 16 hours

[0082] Table 5 Hydrogen aging resistance test

[0083]

[0084] For Example 1:

[0085] The inner core layer 100 has a radius R1 of 2.5 μm and a Δ1 of 0.14%; the outer core layer 200 has a thickness R2-R1 of 3.8 μm and a Δ2 of 0%; the inner cladding layer 300 has a thickness R3-R2 of 2.5 μm and a Δ3 of -0.22%; the first recessed layer 400 has a thickness R4-R3 of 4.8 μm and a Δ4 of -0.34%; the doped layer 500 has a thickness R5-R4 of 7.9 μm and a relative refractive index difference Δ5 of -0.22%; the second recessed layer 600 has a thickness R6-R5 of 20 μm and a relative refractive index difference Δ5 of -0.28%; and the outer cladding layer is pure silicon dioxide with a radius R7 of 62.5 μm.

[0086] The drawn optical fiber has a mode field diameter of 9.2 μm at 1310 nm and a mode field diameter of 10.5 μm at 1550 nm. The cutoff wavelength is 1240 nm, and the attenuations at 1310 nm and 1550 nm are 0.288 dB / km and 0.163 dB / km, respectively. The zero-dispersion wavelength is 1314 nm, and the slope at the zero-dispersion wavelength is 0.087 ps / (nm). 2 The optical fiber has a dispersion value of 16.6 ps / (nm*km) at 1550nm and meets the G652 standard in all aspects.

[0087] The refractive index distribution of the optical fiber obtained in Example 1 was tested using an optical fiber refractive index profiler (scanning laser using a standard wavelength of 632 nm), and its refractive index distribution diagram is shown below. Figure 3 As shown.

[0088] The stress distribution of the optical fiber obtained in Example 1 was tested using an optical fiber stress tester. Additionally, under the same cross-sectional design, the inner and outer core layers were prepared using a method of only F doping and no P doping. The stress distribution diagrams of the two types of optical fibers were compared as follows: Figure 4 As shown.

[0089] It can be seen that, under the same cross-sectional design, compared to P-doped fiber, F-doped fiber requires more GE doping in the core layer to ensure the refractive index difference. Besides increasing Rayleigh scattering, this also leads to a more pronounced stress abrupt change between the core and the subsided layer. P-doping in the core layer is more effective than F-doping in reducing the stress mismatch between the core and the subsided layer.

[0090] For Example 2:

[0091] Based on Example 1, the refractive index Δ1 is reduced from 0.14% to 0.12%, while other structural parameters remain essentially the same as in Example 1. After reducing the core refractive index, this designed fiber achieves a zero-dispersion wavelength shift to 1318 nm, with a zero-dispersion wavelength slope of 0.087 ps / (nm). 2 The dispersion value at 1550nm is 16.4ps / (nm*km), the attenuation at 1550nm is 0.180dB / km which increases significantly, the attenuation at 1310nm is 0.285dB / km which decreases slightly, the cable cutoff wavelength decreases to 1120nm, and the bending loss of R15*10@1550nm, R10*1@1550nm, and R7.5*1@1550nm increases significantly, indicating that there is leakage of optical signal at long wavelengths.

[0092] For fiber designs with small mode field diameters, reducing the core-cladding refractive index difference will result in a smaller cutoff wavelength for the fundamental mode, leading to long-wavelength transmission leakage. It is necessary to widen or deepen the recessed layer or maintain a sufficiently large core-cladding refractive index difference.

[0093] Example 3:

[0094] Compared to Example 1, the refractive index parameters of each structural layer of the optical fiber in Example 3 remain basically unchanged. Because the inner core layer adopts Ge / F / P co-doping, the amount of Ge doping in the core layer increases compared to the previous example, while the refractive index of the core layer remains unchanged. This results in an increase in Rayleigh scattering loss. The attenuation at 1310nm and 1550nm of this designed optical fiber increases to 0.297dB / km and 0.169dB / km, respectively. Other parameters remain basically unchanged.

[0095] Example 4:

[0096] Compared to Example 1, while keeping the core diameter and height unchanged, the core layer is now designed with a stepped profile, increasing the half-width at half-maximum (WHM) compared to Example 1. Furthermore, due to the intensified stress abrupt change in the core cladding, although bending loss is reduced, the attenuation at 1310nm and 1550nm increases to 0.304dB / km and 0.178dB / km, respectively. The cable wavelength increases to 1340nm, the zero-dispersion wavelength shifts to 1298nm, and the zero-dispersion wavelength slope is 0.093ps / (nm). 2 The dispersion value at 1550nm is 18.9ps / (nm*km), exceeding the G652 standard.

[0097] like Figure 5 As shown, under the same core layer refractive index difference and to ensure that the mode field diameter remains unchanged, the core layer step design has obvious shortcomings in terms of attenuation and dispersion control compared to the core layer parabolic gradient design.

[0098] Example 5:

[0099] refer to Figure 6 According to the table content, compared with Example 1, Example 5 does not have the second recessed layer 600 design. To prevent optical power leakage, the refractive index of the core layer is increased by 0.19%, and the Ge doping content of the core layer is increased. The attenuation at @1550nm increases to 0.172dB / km, and the cable wavelength does not change significantly. The zero-dispersion wavelength shifts to 1308nm, and the zero-dispersion wavelength slope is 0.090ps / (nm). 2 The dispersion value at 1550nm is 17.9ps / (nm*km), which is close to the upper limit of the G652 standard.

[0100] Example 6:

[0101] refer to Figure 7 According to the table content, compared with Example 1, Example 6 does not have the design of the second recessed layer 600. In order to prevent optical power leakage and ensure low bending loss, the width and depth of the first recessed layer 400 are increased to 7.4μm and -0.42% respectively. The cable wavelength is increased to 1335nm, which exceeds the upper limit of the G652 standard. In addition, the mode field diameter is reduced to 8.8μm, which is close to the lower limit of the standard. The dispersion parameters do not change significantly.

[0102] In summary, the low-loss single-mode fiber of this application includes a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer 100 and an outer core layer 200. The cladding layer includes an inner cladding layer 300, a first recessed layer 400, a doped layer 500, a second recessed layer 600, and an outer cladding layer 700, stacked sequentially from the center to the outer periphery. The inner core layer 100 is doped with P and GeO2, the outer core layer 200 is doped with F, P, and GeO2, the inner cladding layer 300 is doped with GeO2, P, and F, the first recessed layer 400 is doped with GeO2 and F, the doped layer 500 is doped with GeO2 and F, and the second recessed layer 600 is doped with GeO2 and F. Through reasonable fiber structure design and core layer doping control, while keeping the core cross-sectional structure unchanged, Rayleigh scattering is reduced by adjusting the elements doped in the inner and outer core layers, thereby achieving the purpose of reducing the fiber attenuation coefficient.

[0103] Furthermore, by adjusting the refractive index of the F-doped interlayer tube used for matching fiber drawing, the position of the cutoff wavelength shift can be controlled, allowing the drawn optical fiber to be adjusted to different wavelength ranges. Under the premise that the various performance characteristics of the optical fiber are compatible with the G.652 standard, the optical fiber has lower attenuation loss and better bending resistance.

[0104] Furthermore, the low-loss single-mode fiber provided in this application adopts a parabolic gradient design, which on the one hand can achieve a gradual change in physical properties and doping concentration, eliminating or reducing the interfacial stress difference between the core and cladding layers; on the other hand, while keeping the mode field diameter unchanged, it effectively reduces the zero-dispersion wavelength slope and 1550 dispersion value of the fiber, thus reducing dispersion compensation when used as a long-distance trunk transmission fiber.

[0105] Meanwhile, the low-loss single-mode fiber provided in this application has a second recessed layer 600 near the outer cladding 700. On the one hand, it can effectively reduce the refractive index of the core layer and reduce Rayleigh scattering loss caused by GeO2 doping while preventing optical power leakage. On the other hand, it avoids the refractive index of the first recessed layer 400 near the core layer being too deep and too wide, which would cause the mode field diameter to decrease and the cable wavelength to exceed the standard. This ensures that the fiber has qualified dispersion parameters, mode field diameter, low attenuation and excellent bending resistance.

[0106] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0107] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0108] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0109] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0110] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A low-loss single-mode optical fiber, characterized in that, It includes a core layer and a cladding layer surrounding the core layer. The core layer includes an inner core layer and an outer core layer. The inner core layer is doped with P and GeO2, and the outer core layer is doped with F, P, and GeO2. The cladding layer comprises an inner cladding layer, a first recessed layer, a doped layer, a second recessed layer, and an outer cladding layer, which are stacked sequentially from the center to the outer periphery; the inner cladding layer is doped with GeO2 at a molar concentration of 0-0.2%, P at a molar concentration of 0.01-0.3%, and F at a molar concentration of 0.5-1.5%. The first recessed layer is doped with GeO2 at a molar concentration of 0-0.2% and F at a molar concentration of 0-2.0%; The doped layer is doped with GeO2 at a molar concentration of 0-0.2% and F element at a molar concentration of 0-2.0%; The second recessed layer is doped with GeO2 at a molar concentration of 0-0.2% and F at a molar concentration of 0-3.0%.

2. The low-loss single-mode optical fiber according to claim 1, characterized in that, The inner core layer is doped with GeO2 at a molar concentration of 0.10-1.5% and P at a molar concentration of 0.01-0.3%. The outer core layer is doped with GeO2 at a molar concentration of 0.10-1.5%, P at a molar concentration of 0.01-0.3%, and F at a molar concentration of 0-1.5%.

3. The low-loss single-mode optical fiber according to claim 1, characterized in that, The refractive index of the core layer exhibits a parabolic gradient distribution.

4. The low-loss single-mode optical fiber according to claim 1, characterized in that, The relative refractive index difference Δ1 between the inner core layer and the outer cladding layer is 0.10-0.25%; The relative refractive index difference Δ2 between the outer core layer and the outer cladding layer is 0-0.20%; The relative refractive index difference Δ3 between the inner cladding and the outer cladding is -0.10 to -0.30%; The relative refractive index difference Δ4 between the first recessed layer and the outer cladding layer is -0.25 to -0.50%. The relative refractive index difference Δ5 between the doped layer and the outer cladding layer is -0.30 to -0%. The relative refractive index difference Δ6 between the second recessed layer and the outer cladding layer is -0.50 to 0%.

5. The low-loss single-mode optical fiber according to claim 1, characterized in that, The radius R1 of the inner core layer is 2-6µm; The radius of the outer core layer is R2, and the range of R2-R1 is 3.0-5.0µm; The radius of the inner cladding is R3, and the range of R3-R2 is 2-5µm; The radius of the first recessed layer is R4, and the range of R4-R3 is 2-8µm; The radius of the doped layer is R5, and the range of R5-R4 is 5-30µm; The radius of the second recessed layer is R6, and the range of R6-R5 is 10-22µm; The radius R7 of the outer cladding layer is 60-65µm.

6. The low-loss single-mode optical fiber according to claim 1, characterized in that, The low-loss single-mode fiber has an application wavelength range of 1310-1550nm.

7. The low-loss single-mode optical fiber according to claim 6, characterized in that, The low-loss single-mode fiber has a mode field diameter of 8.7-9.7µm at the application wavelength of 1310nm; The low-loss single-mode fiber has a mode field diameter of 9.5-10.5µm at the application wavelength of 1550nm.

8. The low-loss single-mode optical fiber according to claim 6, characterized in that, The low-loss single-mode fiber has an attenuation coefficient of ≤0.350dB / km at the application wavelength of 1310nm; The low-loss single-mode fiber has an attenuation coefficient of ≤0.175dB / km at the application wavelength of 1550nm.

9. The low-loss single-mode optical fiber according to claim 1, characterized in that, The low-loss single-mode fiber has a zero-dispersion wavelength range of 1300-1324 nm, and the dispersion slope of the low-loss single-mode fiber at the zero-dispersion wavelength is ≤0.092 ps / ( ); The low-loss single-mode fiber has a dispersion coefficient ≤18 ps / ( ) at the application wavelength of 1550 nm. ).

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