A large mode field G657A2 optical fiber compatible with the G652D standard

Abstract

The present invention discloses a G.657A2 optical fiber compatible with the G.652D standard. The glass portion of the optical fiber comprises, from the inside out, a core layer with a step-index refractive index profile, a first cladding layer, and a second cladding layer. The first cladding layer is adjacent to and surrounds the core layer, and the second cladding layer is adjacent to and surrounds the first cladding layer. The core layer has a uniform refractive index, with a refractive index N0 ranging from 1.4610 to 1.4641. The refractive index N1 of the first cladding layer varies between 1.4550 and 1.4570. The difference in refractive index between the second cladding layer and the first cladding layer at their junction is greater than 0.0021. The present invention provides a large-mode-field G657A2 optical fiber compatible with the G652D standard. The first cladding layer adopts a circumferentially varying refractive index structure, which increases the mode field diameter of the optical fiber. This allows the G.657A2 optical fiber to achieve the same mode field diameter parameter level as the G.652D optical fiber, increasing the mode field diameter without sacrificing macrobending performance.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber communication technology, and more specifically relates to a large mode field diameter single-mode optical fiber, in particular a G657A2 optical fiber compatible with the G652D standard. Background Art

[0002] With the widespread adoption of fiber-to-the-x (FTTx) and the acceleration of fiber-optic transformation for the "last mile," coupled with increasing demand for communication capacity, fiber-optic communication systems are placing higher demands on the quality of fiber line installation. The widespread use of single-mode fiber in communication links demands extremely high quality and performance, particularly link compatibility. Specifically, this requires compatibility between G.657 fiber, renowned for its excellent bending performance, and G.652 fiber, renowned for its link transmission stability.

[0003] Mainstream G.652 single-mode fiber achieves zero dispersion at 1310 nm by adjusting the core diameter, cladding diameter, and relative refractive index difference to match the cladding. G.652 fiber minimizes dispersion at 1310 nm, achieving attenuation below 0.35 dB / km, a mode field diameter of approximately 8.6 to 9.5 μm, and a cutoff wavelength of 1100 to 1200 nm. A subcategory, G.652D fiber, optimizes polarization mode dispersion and attenuation at 1383 nm and is currently the mainstream single-mode fiber for communications.

[0004] ITU-T defines G.657 fiber, also known as bend-insensitive single-mode fiber for access networks, as a type of single-mode fiber specifically developed for fiber-to-the-home (FTTH) installations to address the bend sensitivity issues encountered in narrow, curved spaces. The application scenarios for G.657 fiber require excellent added loss at small bend radii, while also achieving a high balance between mechanical reliability and optical performance. G.657 fiber not only offers excellent bend performance but is also compatible with G.652 fiber. Based on bend radius, G.657 fiber is divided into four subcategories: A1, A2, B2, and B3. G.657A1 is fully compatible with G.652D, with a bend radius of up to 10mm. G.657A2 is partially compatible with G.652D, with a bend radius of up to 7.5mm. However, G.657A2, despite its improved bend performance, is not fully compatible with G.652D.

[0005] The typical mode field diameter of mainstream G.657A2 fiber is slightly smaller than that of G.652D. This difference in typical mode field diameter between G.652D and G.657A2 fiber leads to problems such as splice loss, which limits its widespread application in practical engineering. Therefore, it is necessary to develop G.657A2 bend-insensitive single-mode fiber compatible with G.652 to improve the applicability of fiber in FTTx.

[0006] Several methods have been proposed in the prior art to increase the mode field diameter of single-mode optical fibers, typically through precise control of the core refractive index profile. For example, patent CN110488411 describes a large-mode-area single-mode optical fiber with a core refractive index parabolically distributed with an index α ranging from 2.2 to 2.5. This core refractive index design compromises the fiber's bending performance, and it is difficult to achieve a mode field diameter exceeding 8.8 μm at a wavelength of 1310 nm. Consequently, no G.657A2 optical fiber has yet been developed that is highly compatible with the G.652D standard. Summary of the Invention

[0007] In response to the above defects or improvement needs of the existing technology, the refractive index profile of the core layer and the refractive index distribution of the first and second composite claddings are optimized, and the mode field diameter is increased without sacrificing the bending performance, so that an optical fiber with a mode field diameter of more than 8.8μm that meets the requirements of the G.657.A2 standard is achieved. This solves the technical problems in the existing technology that the parabolic core profile has large bending loss and high cost, cannot meet the requirements of the G.657.A2 standard, or has large fusion loss with G.652D optical fiber.

[0008] To achieve the above object, according to one aspect of the present invention, a G.657A2 optical fiber compatible with the G.652D standard is provided, wherein the glass portion of the optical fiber comprises, from the inside out, a core layer having a step-index refractive index profile, a first cladding layer, and a second cladding layer; wherein the first cladding layer is adjacent to and surrounds the core layer, and the second cladding layer is adjacent to and surrounds the first cladding layer;

[0009] The refractive index of the core layer is uniform, and its refractive index N0 is between 1.4610 and 1.4641; the refractive index N1 of the first cladding varies between 1.4550 and 1.4570; and the refractive index difference between the second cladding and the first cladding at the junction is greater than 0.0021.

[0010] Preferably, the G.657A2 optical fiber compatible with the G.652D standard establishes a polar coordinate system with the optical fiber cross section as a plane and the core center of the cross section as the pole, with the polar angle θ and the polar diameter ρ, and ρ=D0 / 2 being the adjacent boundary between the first cladding and the core layer, where D0 is the core diameter;

[0011] On the adjacent boundary line ρ=D0 / 2, the refractive index of the first cladding changes along the circumferential direction, that is: N1=F(θ);

[0012] Moreover, the difference between the maximum and minimum values ​​of N1 on the adjacent boundary ρ=D0 / 2 is no more than 0.0020.

[0013] Preferably, for the G.657A2 optical fiber compatible with the G.652D standard, the distribution of the refractive index N1 of the first cladding is N1=F(ρ,θ). When θ∈(i2π / n,(i+1)2π / n) and ρ=D0 / 2,

[0014] N1=1.4550+A(θ-i2π / n) / (2π / n)

[0015] Wherein, n is a natural number, preferably n is less than or equal to 8, more preferably n is equal to 1, 2, 3, 4, 5 or 6, and even more preferably n is equal to 1 or 2; i is a non-negative integer less than n; A is a constant between 0 and 0.0020;

[0016] Preferably, the distribution of the refractive index N1 of the first cladding of the G.657A2 optical fiber compatible with the G.652D standard is N1=F(ρ,θ), and: when θ∈(0,2π / n) and ρ=D0 / 2, then: N1=1.4550+0.0020nθ / 2π.

[0017] Preferably, the G.657A2 optical fiber compatible with the G.652D standard has a refractive index N1 of the first cladding distributed as N1 = F(ρ, θ), and: when θ∈(0, π) and ρ = D0 / 2, N1 = 1.4550+0.0020θ / π; when θ∈(π, 2π) and ρ = D0 / 2, N1 = 1.4550+0.0020(θ-π) / π.

[0018] Preferably, the G.657A2 optical fiber compatible with the G.652D standard has a refractive index N1 of the first cladding distributed as N1 = F(ρ, θ), and: when θ∈(0, 2π / n) and ρ = D0 / 2, when θ∈(0, π / 2), N1 = 1.4550+0.0018(2θ / π); when θ∈(π / 2, π), N1 = 1.4550+0.0018(θ-π / 2) / (π / 2); when θ∈(π, 3π / 2), N1 = 1.4550+0.0018(θ-π) / (π / 2); when θ∈(3π / 2, 2π), N1 = 1.4550+0.0018(θ-3π / 2) / (π / 2).

[0019] Preferably, the second cladding refractive index N2 of the G.657A2 optical fiber compatible with the G.652D standard is between 1.4515 and 1.4542.

[0020] Preferably, the G.657A2 optical fiber compatible with the G.652D standard has a core layer diameter D0 between 6.6 and 8.0 μm; a first cladding layer diameter D1 between 15 and 30 μm; and a second cladding layer diameter D2 between 30 and 40 μm.

[0021] Preferably, the glass portion of the G.657A2 optical fiber compatible with the G.652D standard further includes a pure silica cladding adjacent to and surrounding the second cladding; the pure silica cladding has a refractive index between 1.4570 and 1.4575 and a diameter of 125±1 μm.

[0022] Preferably, the G.657A2 optical fiber compatible with the G.652D standard has a macrobending loss of less than or equal to 0.04 dB in a 1550 nm window with a radius of 15 mm*10 turns, and a macrobending loss of less than or equal to 0.08 dB in a 1625 nm window; a macrobending loss of less than or equal to 0.06 dB in a 10 mm*1 turn at a 1550 nm window, and a macrobending loss of less than or equal to 0.1 dB in a 1625 nm window; a macrobending loss of less than or equal to 0.2 dB in a 7.5 mm*1 turn at a 1550 nm window, and a macrobending loss of less than or equal to 0.5 dB in a 1625 nm window;

[0023] Preferably, the macro-bending loss of the 1550nm window with a radius of 15mm*10 circles is less than or equal to 0.02dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.05dB; the macro-bending loss of the 1550nm window with a radius of 10mm*1 circle is less than or equal to 0.03dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.06dB; the macro-bending loss of the 1550nm window with a radius of 7.5mm*1 circle is less than or equal to 0.1dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.2dB;

[0024] Its microbending loss at a wavelength of 1700nm is less than or equal to 2dB / km;

[0025] Its splicing loss with G.652D optical fiber is better than 0.05dB;

[0026] Its mode field diameter at 1310nm is 8.8~9.4μm, the zero dispersion wavelength is 1300~1324nm, and the optical cable cutoff wavelength is less than or equal to 1260nm;

[0027] Its attenuation coefficient at a wavelength of 1310nm is less than or equal to 0.33dB / km; the attenuation coefficient of the optical fiber at a wavelength of 1383nm is less than or equal to 0.29dB / km; the attenuation coefficient at a wavelength of 1550nm is less than or equal to 0.18dB / km; and the attenuation coefficient at a wavelength of 1625nm is less than or equal to 0.20dB / km.

[0028] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0029] The present invention provides a large-mode-field G657A2 optical fiber compatible with the G652D standard. Its first cladding utilizes a circumferentially varying refractive index structure, increasing the fiber's mode field diameter. This allows the G.657A2 fiber to achieve the same mode field diameter parameters as the G.652D fiber, without sacrificing macrobending performance. This increases the mode field diameter. When the fiber is fused with a G.652D fiber, the first cladding near the splice point melts and diffuses more easily, resulting in better compatibility with the G.652D fiber's cladding. The closer mode field diameters allow the two fibers to fuse together, resulting in low splice losses comparable to those of a single splice.

[0030] The present invention adopts a core layer step-type refractive index distribution to achieve a large mode field diameter. Compared with the existing large mode field diameter optical fiber with a curved core layer refractive index distribution structure, the manufacturing cost is much lower, which is conducive to large-scale production and market promotion.

[0031] The preferred solution utilizes a composite structure of first and second cladding layers, optimizing macrobending performance. This allows the fiber to maintain a large mode field diameter while meeting the additional loss levels at 15mm, 10mm, and 7.5mm bend radii specified by the G.657.A2 bend-insensitive fiber standard. This fiber combines the mode field diameter and geometric parameters of G.652D fiber with the macrobending performance of G.657.A2 fiber, meeting the diverse requirements of FTTx cabling environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the radial cross-sectional structure of an optical fiber provided by the present invention;

[0033] Figure 2 This is a cross-sectional diagram of the optical fiber refractive index provided by the present invention.

[0034] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a core layer, 2 is a first cladding layer, 3 is a second cladding layer, and 4 is a pure quartz layer. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0036] The following are definitions and explanations of some terms involved in this invention:

[0037] Based on the refractive index variation trend across the cross-section, the layer closest to the center of the fiber core is defined as the fiber core. The portion adjacent to and surrounding the fiber core is defined as the first cladding. Similarly, the portion adjacent to and surrounding the first cladding is defined as the second cladding. The outermost layer of the fiber, essentially pure silica, is defined as the outer cladding. Other claddings are permitted between the second cladding and the outermost layer.

[0038] OVD process: Quartz glass with the required thickness and refractive index profile is prepared by external vapor deposition and sintering process.

[0039] POD process: Use plasma external chemical vapor deposition process to prepare quartz glass with the required thickness and refractive index profile.

[0040] Preform rod: It is a material preform that can be used to prepare optical fiber and whose structure meets the design requirements of optical fiber.

[0041] The refractive index of each layer of the optical fiber is the refractive index measured under 589nm yellow light. The refractive index of pure silica is approximately between 1.4570 and 1.4575, the refractive index of air is approximately 1, and the refractive index of water is approximately 1.33.

[0042] The test method for macrobending additional loss refers to the method specified in IEC60793-1-47.

[0043] The microbending loss test method refers to Method B in IEC-62221.

[0044] The test method for the cut-off wavelength λcc of optical cables refers to the method specified in IEC 60793-1-44.

[0045] The present invention provides a G.657A2 optical fiber compatible with the G.652D standard, comprising, from the inside out, a core layer with a step-index refractive index profile, a first cladding layer, and a second cladding layer. The first cladding layer is adjacent to and surrounds the core layer, and the first cladding layer and the second cladding layer have different compositions and refractive index profiles.

[0046] The refractive index N0 of the core layer is between 1.4610 and 1.4641, and the diameter D0 of the core layer is between 6.6 and 8.0 μm.

[0047] The refractive index N1 of the first cladding varies between 1.4550 and 1.4570, and the diameter D1 of the first cladding is between 15 and 30 μm.

[0048] A polar coordinate system is established with the cross section of the optical fiber as a plane and the center of the core layer of the cross section as the pole, with the polar angle θ and the polar diameter ρ. Then, at the boundary between the core layer and the first cladding of the cross section, ρ = D0 / 2. The refractive index of the first cladding varies along the boundary (circumference) between the core layer and the first cladding of the cross section. The refractive index N1 of the first cladding is a function of θ and ρ, and the difference between the maximum and minimum values ​​of N1 is no more than 0.0020.

[0049] Preferably, the distribution of the refractive index N1 of the first cladding is N1=F(ρ,θ) and ρ=D0 / 2. When θ∈(i2π / n,(i+1)2π / n), we have:

[0050] N1=1.4550+A(θ-i2π / n) / (2π / n)

[0051] Where n is a natural number, preferably less than or equal to 8, more preferably 1, 2, 3, 4, 5, or 6, and even more preferably 1 or 2; i is a non-negative integer less than n; and A is a constant between 0 and 0.0020. This means that the refractive index of the first cladding varies linearly and periodically along the circumferential direction at the core-cladding interface.

[0052] One of the preferred solutions is that the large mode field diameter G.657A2 optical fiber compatible with the G.652D standard has a refractive index N1 of the first cladding distributed as N1 = F(ρ,θ) and ρ = D0 / 2, so: when θ∈(0,2π / n), N1 = 1.4550+0.0020nθ / 2π; that is, n = 1.

[0053] The second preferred solution is that the large mode field diameter G.657A2 optical fiber compatible with the G.652D standard has a refractive index N1 of the first cladding distributed as N1 = F(ρ, θ) and ρ = D0 / 2: when θ∈(0,π), N1 = 1.4550+0.0020θ / π; when θ∈(π, 2π) and ρ = D0 / 2, N1 = 1.4550+0.0020(θ-π) / π; that is, n = 2.

[0054] Preferred solution three, the large mode field diameter G.657A2 optical fiber compatible with the G.652D standard, the distribution of the refractive index N1 of the first cladding is N1 = F(ρ, θ) and ρ = D0 / 2, so: when θ∈(0,π / 2), N1 = 1.4550+0.0018(2θ / π); when θ∈(π / 2,π), N1 = 1.4550+0.0018(θ-π / 2) / (π / 2); when θ∈(π,3π / 2), N1 = 1.4550+0.0018(θ-π) / (π / 2); when θ∈(3π / 2,2π), N1 = 1.4550+0.0018(θ-3π / 2) / (π / 2); that is, n = 4.

[0055] The refractive index N2 of the second cladding is between 1.4515 and 1.4542, and the diameter D2 of the second cladding is between 30 and 40 μm. Preferably, the refractive index difference between the first cladding and the second cladding is greater than 0.0021 to ensure bending performance.

[0056] The G.657A2 optical fiber, compatible with the G.652D standard and with a large mode field diameter, preferably also includes a pure silica cladding adjacent to and surrounding the second cladding. The pure silica cladding has a refractive index N3 between 1.4570 and 1.4575, and a diameter D3 of 125±1 μm. The geometric parameters of the pure silica cladding are defined by international standards and are relevant to connectors. Fluctuations within the standard range do not affect the optical performance of the fiber, but only the stability of the manufacturing process.

[0057] The large mode field diameter G.657A2 optical fiber compatible with the G.652D standard meets the G.657.A2 standard:

[0058] The above-mentioned optical fiber has a macro-bending loss of less than or equal to 0.04 dB in the 1550 nm window with a radius of 15 mm*10 turns, and a macro-bending loss of less than or equal to 0.08 dB in the 1625 nm window; a macro-bending loss of less than or equal to 0.06 dB in the 1550 nm window with a radius of 10 mm*1 turn, and a macro-bending loss of less than or equal to 0.1 dB in the 1625 nm window; a macro-bending loss of less than or equal to 0.2 dB in the 1550 nm window with a radius of 7.5 mm*1 turn, and a macro-bending loss of less than or equal to 0.5 dB in the 1625 nm window.

[0059] Its microbending loss at a wavelength of 1700nm is less than or equal to 2dB / km.

[0060] Preferably, the large mode field diameter G.657A2 optical fiber compatible with the G.652D standard has a 1550nm window macro-bending loss of less than or equal to 0.02dB at a radius of 15mm*10 turns, and a 1625nm window macro-bending loss of less than or equal to 0.05dB; a 1550nm window macro-bending loss of less than or equal to 0.03dB at a radius of 10mm*1 turn, and a 1625nm window macro-bending loss of less than or equal to 0.06dB; a 1550nm window macro-bending loss of less than or equal to 0.1dB at a radius of 7.5mm*1 turn, and a 1625nm window macro-bending loss of less than or equal to 0.2dB.

[0061] To optimize bending loss, conventional G.657A2 fiber core diameters are typically 1-2 μm smaller than those of G.652D fibers. While a smaller core diameter reduces bending loss, this also has the negative effect of reducing the fiber's mode field diameter, leading to increased mode field mismatch and splicing losses compared to G.652 fibers. Compared to core-cladding designs with a uniform refractive index, the present invention utilizes a first cladding with a circumferentially varying refractive index, increasing the range of optical power distribution across the fiber's cross-section and thus the mode field diameter. The fiber designed in this invention meets the mode field diameter requirements of the G.657.A2 standard and is compatible with the G.652D standard.

[0062] Furthermore, the splicing loss between the optical fiber of the present invention and the G.652D optical fiber is better than 0.05dB, reaching the splicing loss level of the mainstream G.652D optical fiber itself, thereby optimizing the loss in the link design to the greatest extent.

[0063] The optical fiber provided by the present invention has a mode field diameter of 8.8 to 9.4 μm at 1310 nm, a zero dispersion wavelength of 1300 to 1324 nm, and an optical cable cutoff wavelength less than or equal to 1260 nm;

[0064] The attenuation coefficient of the optical fiber provided by the present invention at a wavelength of 1310 nm is less than or equal to 0.33 dB / km; the attenuation coefficient of the optical fiber at a wavelength of 1383 nm is less than or equal to 0.29 dB / km; the attenuation coefficient at a wavelength of 1550 nm is less than or equal to 0.18 dB / km; and the attenuation coefficient at a wavelength of 1625 nm is less than or equal to 0.20 dB / km.

[0065] The manufacturing method adopted by the optical fiber of the present invention is to prepare the required optical fiber preform core rod by the OVD process, prepare the first and second claddings by the OVD or POD process, and then outsource the other claddings by the OVD process; the prepared preform rod can be drawn to obtain a large mode field diameter G.657A2 optical fiber compatible with the G.652D standard; the drawing speed is 200 to 3000 m / min, and the optical fiber is coated with a UV-curable polyester coating as a protective layer online during the drawing process.

[0066] The core layer is a quartz glass layer primarily doped with germanium and / or alkali metals, and the first cladding is a quartz glass layer primarily doped with germanium, fluorine, chlorine, and alkali metals. The first cladding is deposited outside the core rod using outside vapor deposition (OVD) or outside plasma deposition (POD). By adjusting the flow rates and ratios of the various raw gas streams, a linear refractive index profile is achieved along the circumferential direction of the first cladding.

[0067] The following are examples:

[0068] Example 1:

[0069] The optical fiber includes the core layer, the first cladding layer, the second cladding layer, the outer cladding layer, and the coating layer from the inside to the outside. The geometric distribution is as follows: Figure 1 As shown, the refractive index distribution is Figure 2 As shown: the core layer is a Ge-doped silica glass layer with a diameter of D0 and a relative refractive index difference of N0; the first cladding has a diameter of D1 and a relative refractive index difference of N1; the second cladding has a diameter of D2 and a relative refractive index difference of N2; the refractive index of the first cladding ρ = D0 / 2, expressed as a function: N1 = 1.4550 + 0.0020 (θ / 2π), and the coordinates are set as follows Figure 1 shown.

[0070] According to the technical solution of the large mode field diameter G.657A2 optical fiber compatible with the G.652D standard, the main parameters of the optical fiber refractive index profile structure of Example 1 are shown in Table 1.1:

[0071] Table 1.1 Refractive index profile parameters of the optical fiber of Example 1

[0072]

[0073]

[0074] The main performance parameters of optical fiber are shown in Table 1.2:

[0075] Table 1.2 Performance parameters of optical fiber in Example 1

[0076]

[0077] Example 2:

[0078] The refractive index profile structure of Example 2 is similar to that of Example 1, except that the refractive index of the first cladding layer ρ=D0 / 2 in Example 2 is expressed as a function:

[0079] When θ∈(i2π / n,(i+1)2π / n), N1=1.4550+0.0019(θ-i2π / n) / (2π / n); n is 2, i is 0 or 1; that is

[0080] When θ∈(0,π),

[0081] When θ∈(π,2π),

[0082] The main parameters of the optical fiber refractive index profile structure of Implementation 2 are shown in Table 2.1:

[0083] Table 2.1 Refractive index profile parameters of the optical fiber of Example 2

[0084] Example <![CDATA[D0]]> <![CDATA[D1]]> <![CDATA[D2]]> <![CDATA[N0]]> <![CDATA[N1(min)]]> <![CDATA[N1(max)]]> <![CDATA[N2]]> 2.1 6.9 18.2 32.1 1.4641 1.4550 1.4569 1.4523 2.2 7.3 25.6 37.5 1.4628 1.4550 1.4569 1.4522 2.3 7.9 28.1 39.6 1.4615 1.4550 1.4569 1.4515

[0085] The main performance parameters of optical fiber are shown in Table 2.2.

[0086] Table 2.2 Performance parameters of optical fiber in Example 2

[0087]

[0088] Example 3:

[0089] The refractive index profile structure of Example 3 is similar to that of Example 1, except that the refractive index of the first cladding layer ρ=D0 / 2 in Example 3 is expressed as a function:

[0090] When θ∈(i2π / n,(i+1)2π / n), N1=1.4550+0.0018(θ-i2π / n) / (2π / n); n is 4, i is 0 or 1, 2, 3; that is

[0091] When θ∈(0,π / 2), N1=1.4550+0.0018(2θ / π);

[0092] When θ∈(π / 2,π), N1=1.4550+0.0018(θ-π / 2) / (π / 2);

[0093] When θ∈(π,3π / 2), N1=1.4550+0.0018(θ-π) / (π / 2);

[0094] When θ∈(3π / 2,2π), N1=1.4550+0.0018(θ-3π / 2) / (π / 2);

[0095] The main parameters of the optical fiber refractive index profile structure of Implementation 3 are shown in Table 3.1:

[0096] Table 3.1 Refractive index profile parameters of the optical fiber of Example 2

[0097] Example <![CDATA[D0]]> <![CDATA[D1]]> <![CDATA[D2]]> <![CDATA[N0]]> <![CDATA[N1(min)]]> <![CDATA[N1(max)]]> <![CDATA[N2]]> 3.1 6.7 19.5 33.2 1.4639 1.4550 1.4568 1.4524 3.2 7.0 22.2 36.5 1.4629 1.4550 1.4568 1.4520 3.3 7.3 24.6 39.3 1.4617 1.4550 1.4568 1.4516

[0098] The main performance parameters of optical fiber are shown in Table 3.2.

[0099] Table 2.2 Performance parameters of optical fiber in Example 2

[0100]

[0101]

[0102] Experiments show that different diameters and refractive index distributions of the first cladding result in significant differences in the mode field diameter of the optical fiber at a specific bending radius. When the difference in the refractive index extremes of the first cladding increases, the macroscopic bending loss at a specific diameter fluctuates significantly, and the oscillation phenomenon at long wavelengths is more obvious than the oscillation phenomenon at short wavelengths at certain diameters.

[0103] After comparing the refractive index structure of the first cladding layer and optimizing its refractive index and diameter in the patented example, bending losses at various bend radii were significantly improved and maintained stable. Macrobending losses at bend radii of 7.5mm, 10mm, and 15mm were reduced by over 50% and remained stable.

[0104] When the difference between the first cladding refractive index extremes is too large, the mode field is significantly disturbed, resulting in unstable macrobending losses. When the difference between the first cladding refractive index extremes is too small, the disturbance to the mode field diameter is minimal, and the fiber's mode field diameter does not significantly increase, leading to incompatible mode field parameters and high splicing losses. When the difference between the first cladding refractive index extremes is around 0.0020, macrobending losses are most stable, and the mode field diameter is also compatible.

[0105] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A G.657A2 optical fiber compatible with the G.652D standard, characterized in that: The glass portion includes, from the inside out, a core layer with a step-type refractive index distribution, a first cladding layer, and a second cladding layer; wherein the first cladding layer is adjacent to and surrounds the core layer, and the second cladding layer is adjacent to and surrounds the first cladding layer; The refractive index of the core layer is uniform, and its refractive index N0 is between 1.4610 and 1.4641; the refractive index N1 of the first cladding varies between 1.4550 and 1.4570; the refractive index difference between the second cladding and the first cladding at the junction is greater than 0.0021; A polar coordinate system is established with the cross section of the optical fiber as a plane and the core center of the cross section as the pole. The polar angle is θ, the polar diameter is ρ, and ρ = D0 / 2 is the adjacent boundary between the first cladding and the core layer, where D0 is the core diameter. On the adjacent boundary line ρ=D0 / 2, the refractive index of the first cladding changes along the circumferential direction, that is: N1=F(θ); Moreover, the difference between the maximum and minimum values ​​of N1 on the adjacent boundary ρ=D0 / 2 is no more than 0.0020.

2. The G.657A2 optical fiber compatible with the G.652D standard according to claim 1, characterized in that The distribution of the refractive index N1 of the first cladding is N1=F(ρ,θ). When θ∈(i2π / n,(i+1)2π / n) and ρ=D0 / 2, we have: N1=1.4550+A(θ-i2π / n) / (2π / n) Where n is a natural number; i is a non-negative integer less than n; A is a constant between 0 and 0.0020.

3. The G.657A2 optical fiber compatible with the G.652D standard according to claim 2, characterized in that The distribution of the refractive index N1 of the first cladding is N1 = F(ρ, θ), and: when θ∈(0, 2π / n) and ρ = D0 / 2, then: N1 = 1.4550+0.0020nθ / 2π.

4. The G.657A2 optical fiber compatible with the G.652D standard according to claim 2, characterized in that The distribution of the refractive index N1 of the first cladding is N1 = F(ρ,θ), and: when θ∈(0,π) and ρ=D0 / 2, N1 = 1.4550+0.0020θ / π; when θ∈(π,2π) and ρ=D0 / 2, N1 = 1.4550+0.0020(θ-π) / π.

5. The G.657A2 optical fiber compatible with the G.652D standard according to claim 2, characterized in that: The distribution of the refractive index N1 of the first cladding is N1 = F(ρ, θ), and: when θ∈(0, 2π / n) and ρ = D0 / 2, when θ∈(0, π / 2), N1 = 1.4550+0.0018(2θ / π); when θ∈(π / 2, π), N1 = 1.4550+0.0018(θ-π / 2) / (π / 2); when θ∈(π, 3π / 2), N1 = 1.4550+0.0018(θ-π) / (π / 2); when θ∈(3π / 2, 2π), N1 = 1.4550+0.0018(θ-3π / 2) / (π / 2).

6. The G.657A2 optical fiber compatible with the G.652D standard according to claim 1, characterized in that The refractive index N2 of the second cladding layer is between 1.4515 and 1.4542.

7. The G.657A2 optical fiber compatible with the G.652D standard according to claim 1, characterized in that The diameter D0 of the core layer is between 6.6 and 8.0 μm; the diameter D1 of the first cladding layer is between 15 and 30 μm; and the diameter D2 of the second cladding layer is between 30 and 40 μm.

8. The G.657A2 optical fiber compatible with the G.652D standard according to claim 1, characterized in that The glass part further comprises a pure silica cladding layer adjacent to and surrounding the second cladding layer; the refractive index of the pure silica cladding layer is between 1.4570 and 1.4575, and the diameter is 125±1 μm.

9. The G.657A2 optical fiber compatible with the G.652D standard according to claim 1, characterized in that The macro-bending loss in the 1550nm window with a radius of 15mm*10 circles is less than or equal to 0.04dB, and the macro-bending loss in the 1625nm window is less than or equal to 0.08dB; the macro-bending loss in the 1550nm window with a radius of 10mm*1 circle is less than or equal to 0.06dB, and the macro-bending loss in the 1625nm window is less than or equal to 0.1dB; the macro-bending loss in the 1550nm window with a radius of 7.5mm*1 circle is less than or equal to 0.2dB, and the macro-bending loss in the 1625nm window is less than or equal to 0.5dB.

10. The G.657A2 optical fiber compatible with the G.652D standard according to claim 9, characterized in that: The macro-bending loss of the 1550nm window with a radius of 15mm*10 circles is less than or equal to 0.02dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.05dB; the macro-bending loss of the 1550nm window with a radius of 10mm*1 circle is less than or equal to 0.03dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.06dB; the macro-bending loss of the 1550nm window with a radius of 7.5mm*1 circle is less than or equal to 0.1dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.2dB; Its microbending loss at a wavelength of 1700nm is less than or equal to 2dB / km; Its splicing loss with G.652D optical fiber is better than 0.05dB; Its mode field diameter at 1310nm is 8.8~9.4μm, the zero dispersion wavelength is 1300~1324nm, and the optical cable cutoff wavelength is less than or equal to 1260nm; Its attenuation coefficient at a wavelength of 1310nm is less than or equal to 0.33dB / km; the attenuation coefficient of the optical fiber at a wavelength of 1383nm is less than or equal to 0.29dB / km; the attenuation coefficient at a wavelength of 1550nm is less than or equal to 0.18dB / km; and the attenuation coefficient at a wavelength of 1625nm is less than or equal to 0.20dB / km.

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