Low-loss single-mode optical fiber

Abstract

A low-loss single-mode optical fiber, which relates to the technical field of communication optical fibers. The low-loss single-mode optical fiber comprises a core layer and a cladding layer surrounding the periphery of the core layer, wherein the core layer comprises an inner core layer (100) and an outer core layer (200), the inner core layer (100) is doped with P and GeO2, and the outer core layer (200) is doped with F, P and GeO2. By means of adjusting the elements doped in the inner core layer (100) and the outer core layer (200), Rayleigh scattering is decreased, thereby achieving the aim of reducing the attenuation coefficient of the optical fiber, such that the optical fiber has lower attenuation loss and better bending resistance.

Description

Low-loss single-mode optical fiber Technical Field

[0001] The present application relates to the technical field of communication optical fibers, and in particular to a low-loss single-mode optical fiber. Background Art

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

[0003] The main component of optical fiber is SiO2. When manufacturing optical fiber preform rods, 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 elements can also 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, when manufacturing the optical fiber preform, the viscosity / thermal expansion coefficient between the core layer and the cladding is inverted, the viscosity / thermal expansion coefficient matching of the optical fiber structure is unbalanced, and a large stress is generated at the interface between the core layer and the cladding, which will lead to increased optical fiber attenuation.

[0005] Summary of the Invention

[0006] In view of the above problems, the embodiments of the present application provide a low-loss single-mode optical fiber to solve the technical problem of high optical fiber attenuation of single-mode optical fibers in related technologies.

[0007] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0008] An embodiment of the present application provides a low-loss single-mode optical fiber, which includes a core layer and a cladding 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.

[0009] In one possible implementation, the inner core layer is doped with GeO2 at a molar concentration of 0.10-1.5% and P element 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 element at a molar concentration of 0.01-0.3% and F element at a molar concentration of 0-1.5%.

[0010] In a possible implementation, the refractive index of the core layer is distributed in a parabolic gradient.

[0011] In a possible implementation, the cladding includes an inner cladding, a first depressed layer, a doping layer, a second depressed layer and an outer cladding, which are stacked in sequence from the center to the periphery; the inner cladding is doped with GeO2 with a molar concentration of 0-0.2%, a P element with a molar concentration of 0.01-0.3% and a F element with a molar concentration of 0.5-1.5%; the first depressed layer is doped with GeO2 with a molar concentration of 0-0.2% and a F element with a molar concentration of 0-2.0%; the doping layer is doped with GeO2 with a molar concentration of 0-0.2% and a F element with a molar concentration of 0-2.0%; and the second depressed layer is doped with GeO2 with a molar concentration of 0-0.2% and a F element with a molar concentration of 0-3.0%.

[0012] In one possible implementation, the relative refractive index difference Δ1 between the inner core layer and the outer cladding is 0.10-0.25%; the relative refractive index difference Δ2 between the outer core layer and the outer cladding 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 depressed layer and the outer cladding is -0.25 to -0.50%; the relative refractive index difference Δ5 between the doping layer and the outer cladding is -0.30 to -0%; and the relative refractive index difference Δ6 between the second depressed layer and the outer cladding is -0.50-0%.

[0013] 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, and the range of R2-R1 is 3.0-5.0 μm; the radius of the inner cladding is R3, and the range of R3-R2 is 2-5 μm; the radius of the first depressed layer is R4, and the range of R4-R3 is 2-8 μm; the radius of the doping layer is R5, and the range of R5-R4 is 5-30 μm; the radius of the second depressed layer is R6, and the range of R6-R5 is 10-22 μm; and the radius R7 of the outer cladding is 60-65 μm.

[0014] In a possible implementation, the application wavelength range of the low-loss single-mode optical fiber is 1310-1550 nm.

[0015] In a possible implementation, the mode field diameter of the low-loss single-mode optical fiber at an application wavelength of 1310 nm is 8.7-9.7 μm; the mode field diameter of the low-loss single-mode optical fiber at an application wavelength of 1550 nm is 9.5-10.5 μm.

[0016] In a possible implementation, the attenuation coefficient of the low-loss single-mode optical fiber at an application wavelength of 1310 nm is ≤0.350 dB / km; the attenuation coefficient of the low-loss single-mode optical fiber at an application wavelength of 1550 nm is ≤0.175 dB / km.

[0017] In a possible implementation, the zero dispersion wavelength range of the low-loss single-mode optical fiber is 1300-1324 nm, and the dispersion slope of the low-loss single-mode optical fiber at the zero dispersion wavelength is ≤0.092 ps / (nm 2 *km); the dispersion coefficient of the low-loss single-mode optical fiber at the application wavelength of 1550nm is ≤18ps / (nm*km).

[0018] The present invention provides a low-loss single-mode optical fiber comprising a core layer and a cladding layer surrounding 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, while the outer core layer is doped with F, P, and GeO2. Through rational fiber structural design and control of core doping elements, Rayleigh scattering is reduced while maintaining the core rod cross-section, thereby lowering the fiber's attenuation coefficient. Furthermore, while maintaining compatibility with the G.652 standard for all fiber performance characteristics, the fiber exhibits lower attenuation loss and improved bending resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] FIG1 is a schematic cross-sectional view of a low-loss single-mode optical fiber provided in an embodiment of the present application;

[0021] FIG2 is a schematic diagram of the cross-sectional structure of a low-loss single-mode optical fiber provided in an embodiment of the present application;

[0022] FIG3 is a schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber according to Example 1 of the present application;

[0023] FIG4 is a schematic diagram showing a comparison of stress distribution of a low-loss single-mode optical fiber according to Example 1 provided in an embodiment of the present application;

[0024] FIG5 is a schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber according to Example 4 of the present application;

[0025] FIG6 is a schematic diagram of the refractive index distribution of a low-loss single-mode optical fiber according to Example 5 of the present application;

[0026] FIG7 is a schematic diagram of the refractive index distribution of the low-loss single-mode optical fiber of Example 6 provided in an embodiment of the present application.

[0027] Reference numerals: 100: inner core layer; 200: outer core layer; 300: inner cladding layer; 400: first depressed layer; 500: doped layer; 600: second depressed layer; 700: outer cladding layer. DETAILED DESCRIPTION

[0028] As explained in the background technology, the single-mode optical fiber in the related technology has the problem of large optical fiber attenuation. After research by technical personnel, it was found that the reason for this problem is that in order to balance the doping amount and the quartz viscosity to achieve lower attenuation, the existing low-loss bend-insensitive single-mode optical fiber profile design generally uses Ge and F elements to co-dope the optical fiber core layer. Since the doping of F element reduces the refractive index of the core layer, more Ge needs to be doped to keep the refractive index of the core layer unchanged. Doping more GE will lead to increased scattering; at the same time, the attenuation, dispersion parameters, mode field diameter, cable wavelength and other parameters of the low-loss cut-off wavelength shifted single-mode optical fiber are also affected by the core layer structure. The existing core layer profile adopts a step-type design, and there is an obvious stress mutation between the core and cladding, resulting in high attenuation. Moreover, when adjusting the core layer profile structure, various parameters also change synchronously, and various indicators are difficult to meet the G.652 standard (the G.652 standard specifies the characteristics and performance of single-mode optical fiber (SMF), including mode distribution, mode distribution constant, maximum attenuation, maximum refractive index change, tensile strength and thermal deformation temperature, etc.); to ensure that various parameters are compatible with the G.652 standard, the depth and width of the ring core recessed layer are designed to have limited values, and the effect of improving the optical fiber's anti-bending performance is limited, making it difficult to meet the G.657 bending loss standard.

[0029] In addition, after the core rod profile is finalized, the existing low-loss cutoff wavelength shifted single-mode optical fiber is directly matched with the pure silica sleeve for drawing. The position of the cutoff wavelength shift is inconvenient to adjust, resulting in a narrow wavelength range for the optical fiber drawn from the preform. In response to the above technical problems, the embodiments of the present application provide a low-loss single-mode optical fiber. Through reasonable optical fiber structure design, core layer doping control, and outer core layer doping control, the optical fiber has lower attenuation loss and better bending resistance under the premise that all optical fiber performance is compatible with the G.652 standard. At the same time, under the premise that the core rod profile structure remains unchanged, the position of the cutoff wavelength shift can be controlled by adjusting the refractive index of the F-doped interlayer tube for matching drawing, so that the drawn optical fiber can be adjusted to different wavelength ranges and further improve the bending performance.

[0030] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] An embodiment of the present application provides a low-loss single-mode optical fiber. Referring to Figures 1 and 2, Figure 1 is a schematic cross-sectional view of the low-loss single-mode optical fiber provided in the embodiment of the present application, and Figure 2 is a schematic cross-sectional view of the low-loss single-mode optical fiber provided in the embodiment of the present 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 depressed layer 400, a doped layer 500, a second depressed layer 600, and an outer cladding layer 700, which are sequentially stacked from the center to the periphery. In the embodiment of the present application, the radius R of the inner core layer 100 is 1 can be 2-6μm, the radius of the outer core layer 200 is R2, and the range of R2-R1 is 3.0-5.0μm; the radius of the inner cladding 300 is R3, and the range of R3-R2 is 2-5μm; the radius of the first depressed layer 400 is R4, and the range of R4-R3 is 2-8μm; the radius of the doping layer 500 is R5, and the range of R5-R4 is 5-30μm; the radius of the second depressed layer 600 is R6, and the range of R6-R5 is 10-22μm; the radius R7 of the outer cladding 700 is 60-65μm, and the radius R7 of the outer cladding 700 can be 62.5μm.

[0032] The refractive index is changed by doping GeO2 and P elements into the inner core layer 100, wherein the inner core layer 100 is doped with GeO2 with a molar concentration of 0.10-1.5% and P with a molar concentration of 0.01-0.3%.

[0033] The refractive index is changed by doping GeO2, P element and F element in the outer core layer 200, 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 greater than 0 and less than 1.5%.

[0034] The refractive index is changed by doping GeO2, P element and F element into the inner cladding 300, wherein the inner cladding 300 is doped with GeO2 with a molar concentration of 0-0.2%, P element with a molar concentration of 0.01-0.3% and F element with a molar concentration of 0.5-1.5%.

[0035] The refractive index is changed by doping GeO 2 and F elements into the first recessed layer 400 , wherein the first recessed layer 400 is doped with GeO 2 with a molar concentration of 0-0.2% and F with a molar concentration of 0-2.0%.

[0036] The refractive index is changed by doping GeO 2 and F elements in the doping layer 500 , wherein the doping layer 500 is doped with GeO 2 with a molar concentration of 0-0.2% and F with a molar concentration of 0-2.0%.

[0037] The refractive index is changed by doping GeO 2 and F elements in the second recessed layer 600 , wherein the second doping layer is doped with GeO 2 with a molar concentration of 0-0.2% and F with a molar concentration of 0-3.0%.

[0038] The refractive index of the core layer presents a parabolic gradient distribution, which can achieve a gradual change in physical properties and doping concentration, eliminate or reduce the interface stress difference between the core and cladding layers, and reduce the 1550 dispersion value to meet the G652 standard requirements while keeping the mode field diameter unchanged.

[0039] It should be noted that the relative refractive index difference Δ1 between the inner core layer 100 and the outer cladding 700 can be maintained between 0.10-0.25%, the relative refractive index difference Δ2 between the outer core layer 200 and the outer cladding 700 can be maintained between 0-0.20%, the relative refractive index difference Δ3 between the inner cladding 300 and the outer cladding 700 can be maintained between -0.10 and -0.30%, the relative refractive index difference Δ4 between the first depressed layer 400 and the outer cladding 700 can be maintained between -0.25 and -0.50%, the relative refractive index difference Δ5 between the doping layer 500 and the outer cladding 700 can be maintained between -0.30 and -0%, and the relative refractive index difference Δ6 between the second depressed layer 600 and the outer cladding 700 can be maintained between -0.50 and 0%.

[0040] The above refractive index can keep the application wavelength range of the single-mode optical fiber between 1310-1550 nm.

[0041] The single-mode fiber has a mode field diameter of 8.7-9.7 μm at an operating wavelength of 1310 nm, preferably 9.2 μm, and an attenuation coefficient of 0.350 dB / km or less. Alternatively, the attenuation coefficient can be 0.290 dB / km. The single-mode fiber has a mode field diameter of 9.5-10.5 μm at an operating wavelength of 1550 nm, preferably 10.5 μm, and an attenuation coefficient of 0.175 dB / km or less. Alternatively, the attenuation coefficient can be 0.165 dB / km or less at an operating wavelength of 1550 nm. All performance indicators are compatible with the G.652 and G.657A2 standards.

[0042] The above refractive index can also keep the zero dispersion wavelength range of single-mode optical fiber between 1300-1324nm; wherein, the dispersion slope of single-mode optical fiber at the zero dispersion wavelength is ≤0.092ps / (nm 2 *km); the dispersion coefficient of single-mode optical fiber at the application wavelength of 1550nm is ≤18ps / (nm*km).

[0043] It should be noted that the molar concentration of the P doping element is less than 0.3% molar concentration. Co-doping with the F element can essentially eliminate the effect of the P absorption peak at 1570nm on the optical fiber's waveguide attenuation between 1530nm and 1625nm. When the molar concentration of the P doping element is less than 0.3% molar concentration, and after deuterium treatment, the hydrogen aging resistance of the P-doped single-mode fiber is essentially the same as that of ordinary single-mode fiber without the P element, meeting the standard requirements.

[0044] The cross-sectional structure is also designed by adjusting the flow ratio of SiO2, GeO2, F, and P during the deposition process. The principle of GeO2 doping is to minimize its doping level to reduce Rayleigh scattering losses caused by GeO2 doping. Because trace P doping in the core replaces the F doping effect on core viscosity, omitting F from the core layer, while maintaining the refractive index difference between the core and cladding, can further reduce the amount of GeO2 doped in the core, thereby reducing Rayleigh scattering.

[0045] The low-loss single-mode optical fiber of the present invention comprises a core layer and a cladding layer surrounding the core layer. The core layer comprises an inner core layer 100 and an outer core layer 200. The cladding layer comprises an inner cladding layer 300, a first depressed layer 400, a doping layer 500, a second depressed layer 600, and an outer cladding layer 700, stacked sequentially from the center to the 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 depressed layer 400 is doped with GeO2 and F, the doping layer 500 is doped with GeO2 and F, and the second depressed layer 600 is doped with GeO2 and F. Through reasonable optical fiber structural design and core layer doping control, Rayleigh scattering is reduced by adjusting the doping elements in the inner and outer core layers while maintaining the core rod cross-sectional structure, thereby achieving the purpose of reducing the optical fiber attenuation coefficient.

[0046] At the same time, the position of the cutoff wavelength migration is controlled by adjusting the refractive index of the F-doped interlayer tube used to match the drawing, so that the drawn optical fiber can be adjusted to different wavelength ranges. On the premise that all optical fiber performance is compatible with the G.652 standard, the optical fiber has lower attenuation loss and better anti-bending properties.

[0047] It should be noted that the low-loss single-mode optical fiber provided in the embodiment of the present application is provided with a doping layer 500 and a second depressed layer 600 near the outer cladding 700. On the one hand, it can effectively reduce the refractive index of the core layer and reduce the Rayleigh scattering loss caused by GeO2 doping under the premise of preventing optical power leakage; on the other hand, while ensuring that the refractive index of the core rod remains unchanged, the refractive index of the second depressed layer 600 is adjusted to achieve adjustable cutoff wavelength migration position. The optical fiber can be adjusted for use within a wide wavelength range of 1260 to 1625 nm (O+S+L band), reducing the difficulty of the manufacturing process of the differentiated design of the optical fiber preform.

[0048] At the same time, in addition to controlling the position of the cutoff wavelength migration, the cutoff wavelength of the low-loss single-mode optical fiber in the embodiment of the present application can be adjusted according to the application band to obtain the optimal bending performance, provided that other main properties (MFD, dispersion performance) match G652.

[0049] For example: when the O band is used, the cable cut-off wavelength is ≤1260nm; when the C+L band is used, the cable cut-off wavelength is ≤1530nm; when the S+C+L band is used, the cut-off wavelength is ≤1420nm.

[0050] It should also be noted that the inner core layer 100 and the outer core layer 200 of the low-loss single-mode optical fiber provided in the embodiment of the present application replace the effect of F element doping on viscosity regulation by trace doping of P element, which effectively reduces the GE doping amount in the core layer while keeping the refractive index of the core layer unchanged, thereby reducing Rayleigh scattering.

[0051] Furthermore, the low-loss single-mode optical fiber provided in the embodiment of the present 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 interface stress difference between the core and cladding, and reduce the 1550 dispersion value while maintaining the mode field diameter unchanged to meet the G652 standard requirements.

[0052] In the embodiment of the present application, the outer cladding 700 is made of pure silicon dioxide without being doped with other elements.

[0053] In the embodiment of the present application, the outer core layer 200 is a silica glass layer doped with GeO2, P element and F element.

[0054] In the embodiment of the present application, the low-loss single-mode optical fiber is suitable for various manufacturing processes or hybrid processes such as MCVD and PCVD.

[0055] In the embodiment of the present application, the optical cable cutoff wavelength migration position of the low-loss single-mode optical fiber is adjustable (≤1530 nm).

[0056] It should be noted that for single-mode optical fiber at an application wavelength of 1550nm, the macro-bending loss of 15mm radius-10 turns is ≤0.03dB; the macro-bending loss of 10mm radius-1 turn is ≤0.1dB; and the macro-bending loss of 7.5mm radius-1 turn is ≤0.5dB.

[0057] The low-loss single-mode optical fiber of the present application is described in detail below through Examples 1 to 6.

[0058] The prefabricated core rod is prepared by using an improved in-tube chemical vapor deposition method (MCVD) or a plasma chemical vapor deposition method (PCVD) process, wherein the doping layer 500 can be composed of a quartz substrate tube doped with F elements. The F-doped quartz tube is used as the deposition substrate tube, SiCl4 and O2 are the raw materials of SiO2, SiF4, SF6, C2F6 or CF4 are used as the raw materials for doping with F elements, GECl4 is used as the raw material for doping with GE elements, and POCl3 is used as the raw material for doping with P elements.

[0059] Using a reciprocating oxyhydrogen torch or plasma as a heat source, by controlling the concentration of each doping element in the tube, a recessed layer, inner cladding layer, outer core layer and inner core layer are deposited in sequence on the inner surface of the F-doped base tube; then the deposited tube is melted and shrunk to a suitable inner diameter at high temperature. Before the inner diameter is shrunk, SF6 or C2F6 and O2 are introduced to etch away impurities adhering to the inner diameter surface under the heating of the oxyhydrogen torch or graphite furnace, and finally melted and shrunk at high temperature to form a solid core rod.

[0060] An F-doped quartz sleeve is used as the second depressed layer 600 and a pure quartz sleeve is used as the outer cladding 700 for matching and drawing, and an optical fiber is obtained by high-temperature drawing.

[0061] The optical fiber cross-sectional structure includes an inner core layer 100, an outer core layer 200, an inner cladding layer 300, a first depressed layer 400, a doping layer 500, a second depressed layer 600 and an outer cladding layer 700. The radius of the inner core layer 100 is R1, and the relative refractive index difference is Δ1; the radius of the outer core layer 200 is R2, and the relative refractive index difference is Δ2; the radius of the inner cladding layer 300 is R3, and the relative refractive index difference is Δ3; the radius of the first depressed layer 400 is R4, and the relative refractive index difference is Δ4; the radius of the doping layer 500 is R5, and the relative refractive index difference is Δ5; the radius of the second depressed layer 600 is R6, and the relative refractive index difference is Δ6; the outer cladding layer 700 is pure silica, and its radius R7 is 62.5 μm, and the relative refractive index difference is 0%.

[0062] Table 1 Parameters of optical fibers with different structural designs

[0063] Table 2 Doping element concentration distribution of optical fibers with different structural designs

[0064] Table 3 Test performance of optical fibers with different structural parameters

[0065] The testing standard for MFD (mode field diameter): "GBT-15972.45-2008 Fiber test method specification Part 45: Measurement test methods and test procedures for transmission characteristics and optical characteristics Mode field diameter".

[0066] Cable cut-off wavelength detection standard: "GBT-15972.44-2008 Fiber optic test method specification Part 44: Transmission characteristics and optical characteristics measurement test methods and test procedures cut-off wavelength".

[0067] Attenuation coefficient test standard: "GBT-15972.40-2008 Fiber optic test method specification Part 40: Measurement test methods and test procedures for transmission characteristics and optical characteristics attenuation".

[0068] Macrobending loss detection standard: "GBT-15972.47-2008 Fiber Test Method Specification Part 47: Measurement Test Methods and Test Procedures for Transmission Characteristics and Optical Characteristics Macrobending Loss".

[0069] Dispersion detection standard: "GBT-15972.42-2008 Fiber test method specification Part 42: Transmission characteristics and optical characteristics measurement test methods and test procedures Wavelength dispersion".

[0070] The hydrogen aging resistance of the optical fibers obtained in Examples 1 to 6 was tested. The test methods are shown in Table 4, and the test results are shown in Table 5.

[0071] Table 4 Hydrogen resistance aging detection method

[0072] Table 5 Hydrogen aging resistance test

[0073] For Example 1:

[0074] The radius R1 of the inner core layer 100 is 2.5 μm, and Δ1 is 0.14%; the thickness R2-R1 of the outer core layer 200 is 3.8 μm, and Δ2 is 0%; the thickness R3-R2 of the inner cladding 300 is 2.5 μm, and Δ3 is -0.22%; the thickness R4-R3 of the first depressed layer 400 is 4.8 μm, and Δ4 is ​​-0.34%; the thickness R5-R4 of the doping layer 500 is 7.9 μm, and the relative refractive index difference Δ5 is -0.22%; the thickness R6-R5 of the second depressed layer 600 is 20 μm, and the relative refractive index difference Δ6 is -0.28%; the outer cladding is pure silica, and the radius R7 is 62.5 μm.

[0075] The mode field diameter of the drawn fiber is 9.2 μm at 1310 nm and 10.5 μm at 1550 nm. The cable cutoff wavelength is 1240 nm. The attenuation 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 zero dispersion wavelength slope is 0.087 ps / (nm). 2 *km), the dispersion value at 1550nm is 16.6ps / (nm*km), and all optical fiber performances comply with the G652 standard.

[0076] The refractive index profile of the optical fiber obtained in Example 1 was tested using an optical fiber refractive index profile tester (scanning laser using a standard wavelength of 632 nm), and the refractive index profile diagram thereof was obtained as shown in FIG3 .

[0077] The stress distribution of the optical fiber obtained in Example 1 was tested using an optical fiber stress tester. Under the same cross-sectional design, the inner / outer core layers were prepared by only F-doping and not P-doping. The comparison of the stress distribution diagrams of the two optical fibers is shown in Figure 4.

[0078] It can be seen that, compared to P-doped core fibers, with the same cross-sectional design, F-doped fibers require more GE doping in the core to maintain the core refractive index difference. This not only increases Rayleigh scattering but also leads to a more pronounced stress mutation between the core and the depression layer. P-doping the core is more effective than F-doping in reducing the stress mismatch between the core and the depression layer.

[0079] For Example 2:

[0080] On the basis of Example 1, the refractive index Δ1 is reduced from 0.14% to 0.12%, and the other structural parameters are basically the same as those of Example 1. After the core refractive index of the designed optical fiber is reduced, the zero dispersion wavelength is shifted to 1318nm, and the zero dispersion wavelength slope is 0.087ps / (nm 2 *km), the dispersion value at 1550nm is 16.4ps / (nm*km), the attenuation at 1550nm increases significantly by 0.180dB / km, the attenuation at 1310nm decreases slightly by 0.285dB / km, the cable cutoff wavelength decreases to 1120nm, and the bending losses of R15*10@1550nm, R10*1@1550nm, and R7.5*1@1550nm increase significantly, indicating that optical signals leak at long wavelengths.

[0081] For optical fiber designs with smaller mode field diameters, reducing the core-cladding refractive index difference will result in a smaller cutoff wavelength of the fundamental mode and leakage of long-wavelength light. It is necessary to widen or deepen the depressed layer or maintain a sufficiently large core-cladding refractive index difference.

[0082] Example 3:

[0083] Compared with Example 1, the refractive index parameters corresponding to each structural layer of the optical fiber in Example 3 remain basically unchanged. Since the inner core layer adopts Ge / F / P co-doping, the Ge doping amount in the core layer increases while the refractive index of the core layer remains unchanged, and the resulting Rayleigh scattering loss also increases. The 1310nm attenuation and 1550nm attenuation of the designed optical fiber increase to 0.297dB / km and 0.169dB / km, respectively, and other parameters remain basically unchanged.

[0084] Example 4:

[0085] Compared with the first embodiment, the core layer is changed to a stepped design while the core layer diameter and height remain unchanged. The core layer half-height width increases compared with the first embodiment. In addition, due to the sudden increase in stress of the core cladding, the bending loss is reduced, but 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 *km), the 1550nm dispersion value is 18.9ps / (nm*km), and the fiber dispersion index exceeds the G652 standard.

[0086] As shown in Figure 5, under the condition of the same core refractive index difference and ensuring that the mode field diameter remains unchanged, the core step design has obvious deficiencies in attenuation and dispersion control compared with the core parabolic gradient design.

[0087] Embodiment 5:

[0088] Referring to Figure 6 and the table, compared to Example 1, Example 5 does not have the second recessed layer 600. To prevent optical power leakage, the core layer refractive index is increased by 0.19%, and the core layer Ge doping content is increased. The attenuation @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 *km), the 1550nm dispersion value is 17.9ps / (nm*km), and the fiber dispersion index is close to the upper limit of the G652 standard.

[0089] Example 6:

[0090] Referring to FIG. 7 and the table, compared to Example 1, Example 6 does not include the second depressed layer 600. To prevent optical power leakage and ensure low bending loss, the width and depth of the first depressed layer 400 are increased to 7.4 μm and -0.42%, respectively. The cable wavelength is increased to 1335 nm, exceeding the upper limit of the G652 standard, while the mode field diameter is reduced to 8.8 μm, close to the lower limit of the standard. The dispersion parameters do not change significantly.

[0091] In summary, the low-loss single-mode optical fiber of the embodiment of the present 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 300, a first depressed layer 400, a doping layer 500, a second depressed layer 600, and an outer cladding 700, which are stacked sequentially from the center to the 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 300 is doped with GeO2, P, and F, the first depressed layer 400 is doped with GeO2 and F, the doping layer 500 is doped with GeO2 and F, and the second depressed layer 600 is doped with GeO2 and F. Through reasonable optical fiber structural design and core layer doping control, Rayleigh scattering is reduced by adjusting the doping elements in the inner and outer core layers while maintaining the core rod cross-sectional structure, thereby achieving the purpose of reducing the optical fiber attenuation coefficient.

[0092] The cutoff wavelength migration position is also controlled by adjusting the refractive index of the F-doped interlayer tube used to match the drawing, so that the drawn optical fiber can be adjusted to different wavelength ranges. On the premise that all optical fiber performance is compatible with the G.652 standard, the optical fiber has lower attenuation loss and better anti-bending properties.

[0093] Furthermore, the low-loss single-mode optical fiber provided in the embodiment of the present application adopts a parabolic gradient design, which can, on the one hand, achieve a gradual change in physical properties and doping concentration, eliminate or reduce the interface stress difference between the core and cladding, and on the other hand, effectively reduce the zero dispersion wavelength slope and 1550 dispersion value of the optical fiber while keeping the mode field diameter unchanged, thereby reducing dispersion compensation when used as a long-distance trunk transmission optical fiber.

[0094] At the same time, the low-loss single-mode optical fiber provided in the embodiment of the present application is provided with a second depressed layer 600 near the outer cladding 700, which can effectively reduce the refractive index of the core layer and reduce the Rayleigh scattering loss caused by GeO2 doping while preventing optical power leakage, thereby ensuring low attenuation loss of the optical fiber.

[0095] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0096] It should be noted that references in this specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not.

[0097] Generally speaking, terms should be understood, at least in part, based on the context in which they are used. For example, as used herein, the term "one or more" can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense, depending at least in part on the context. Similarly, terms such as "a," "an," or "the" can also be understood to convey either singular or plural usage, depending at least in part on the context.

[0098] It should be readily understood that “on,” “above,” and “over” in this disclosure should be interpreted in the broadest manner, such that “on” means not only “directly on something,” but also includes “on something” with intervening features or layers therebetween, and “above” or “over” includes not only the meaning of “above” or “over,” but also includes “above” or “over” with no intervening features or layers therebetween (i.e., directly on something).

[0099] Additionally, spatially relative terms, such as "below," "beneath," "beneath," "above," and the like, may be used herein for ease of description 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 in addition to the orientation depicted in the figures. The device may be in other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A low-loss single-mode optical fiber, characterized in that: It comprises a core layer and a cladding layer surrounding the core layer, wherein the core layer comprises an inner core layer and an outer core layer, wherein the inner core layer is doped with P and GeO2, and the outer core layer is doped with F, P and GeO2.

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

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

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

5. The low-loss single-mode optical fiber according to claim 4, characterized in that: The relative refractive index difference Δ1 between the inner core layer and the outer cladding layer is 0.10 to 0.25%; The relative refractive index difference Δ2 between the outer core layer and the outer cladding layer is 0 to 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 depressed layer and the outer cladding layer is -0.25 to -0.50%; The relative refractive index difference Δ5 between the doping layer and the outer cladding layer is -0.30 to 0%; A relative refractive index difference Δ6 between the second depressed layer and the outer cladding layer is in a range of -0.50 to 0%.

6. The low-loss single-mode optical fiber according to claim 4, characterized in that: The radius R1 of the inner core layer is 2 to 6 μm; The radius of the outer core layer is R2, and the range of R2 minus R1 is 3 to 5 μm; The radius of the inner cladding is R3, and the range of R3 minus R2 is 2 to 5 μm; The radius of the first concave layer is R4, and the range of R4 minus R3 is 2 to 8 μm; The radius of the doping layer is R5, and the range of R5 minus R4 is 5 to 30 μm; The radius of the second concave layer is R6, and the range of R6 minus R5 is 10 to 22 μm; The radius R7 of the outer cladding is 60 to 65 μm.

7. The low-loss single-mode optical fiber according to claim 1, characterized in that: The application wavelength range of the low-loss single-mode optical fiber is 1310-1550nm.

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

9. The low-loss single-mode optical fiber according to claim 7, characterized in that: The attenuation coefficient of the low-loss single-mode optical fiber at the application wavelength of 1310 nm is ≤0.350 dB / km; The attenuation coefficient of the low-loss single-mode optical fiber at an application wavelength of 1550 nm is ≤0.175 dB / km.

10. The low-loss single-mode optical fiber according to claim 7, characterized in that: The zero dispersion wavelength range of the low-loss single-mode optical fiber is 1300-1324 nm, and the dispersion slope of the low-loss single-mode optical fiber at the zero dispersion wavelength is ≤0.092 ps / (nm 2 *km); The dispersion coefficient of the low-loss single-mode optical fiber at an application wavelength of 1550 nm is ≤18 ps / (nm*km).

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