Optical fiber

Abstract

This optical fiber comprises a core, an inner cladding, a trench, and an outer cladding. When the relative refractive index difference of the core is ∆1, the relative refractive index difference of the inner cladding is ∆2, the relative refractive index difference of the trench is ∆3, the relative refractive index difference of the outer cladding is ∆4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, the following relationships are established.　2.2 ≤ r2 / r1 ≤ 3.6; 3μm ≤ r3 － r2 ≤ 12μm; 0.25% ≤ ∆1 － ∆2 ≤ 0.50%; − 0.70% ≤ ∆3 ≤ − 0.10%; A zero-dispersion wavelength is 1296-1306 nm. A zero-dispersion slope is 0.088 ps / nm2 / km or less. A 500-meter cable cutoff wavelength is 1260 nm or less. A bending loss for light with a wavelength of 1310 nm when the optical fiber is wound around a mandrel having a diameter of 15 mm is 0.5 dB or less per turn.

Description

fiber optic

[0001] This disclosure relates to optical fibers. This application claims priority under Japanese application No. 2024-232397, filed on 27 December 2024, and incorporates all the provisions contained herein.

[0002] For optical communication between data centers, for example, the CWDM (Coarse Wavelength Division Multiplexing) method is employed, which transmits light of four different wavelengths within the wavelength range of 1271 nm to 1331 nm.

[0003] Patent Document 1 describes a single-mode optical fiber used between data centers. When this optical fiber is wound around a 15 mm diameter mandrel, the bending loss for light at a wavelength of 1310 nm is less than 1.00 dB / turn. The zero-dispersion wavelength of this optical fiber is wide, ranging from 1300 nm to 1324 nm.

[0004] U.S. Patent Application Publication No. 2024 / 0255694

[0005] The optical fiber of this disclosure comprises a germanium-containing core, an inner cladding surrounding the core, a trench surrounding the inner cladding, and an outer cladding surrounding the trench, wherein the relative refractive index difference of the core is Δ1, the relative refractive index difference of the inner cladding is Δ2, the relative refractive index difference of the trench is Δ3, the relative refractive index difference of the outer cladding is Δ4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, then the following relationships hold: 2.2 ≤ r2 / r1 ≤ 3.6 3 μm ≤ r3 - r2 ≤ 12 μm 0.25% ≤ Δ1 - Δ2 ≤ 0.50% -0.70% ≤ Δ3 ≤ -0.10% The zero-dispersion wavelength is 1296 nm or more and 1306 nm or less, and the zero-dispersion slope is 0.088 ps / nm ２ The bending loss is less than or equal to 0.5 dB / turn, the cable cutoff wavelength for 500 m is less than or equal to 1260 nm, and the bending loss for light at a wavelength of 1310 nm when wound around a mandrel with a diameter of 15 mm is less than or equal to 0.5 dB / turn.

[0006] Figure 1 shows a cross-section perpendicular to the axial direction of an optical fiber according to one embodiment. Figure 2 shows the refractive index distribution in the radial direction of a glass fiber. This is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km. This is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km. Figure 5 is a table summarizing the structural parameters and optical properties of the optical fiber. Figure 6 shows the frequency distribution of the dispersion value during transmission over 2 km.

[0007] In the CWDM system, increasing the communication speed leads to a problem where signals at both ends of the four wavelength range are distorted due to the chromatic dispersion characteristics of the optical fiber used in the transmission line, resulting in poor reception. In many cases, optical fibers conforming to ITU-T standards G. 652.D or G. 657.A2 are used in the transmission line. Since the optical fiber only needs to satisfy these standards, the difference between the maximum and minimum dispersion values ​​in the wavelength range of 1271 nm to 1331 nm is amplified not only by the wide wavelength range but also by manufacturing variations in the optical fiber. Optical fibers specifically designed for high-speed communication between data centers are desired.

[0008] This disclosure aims to provide optical fibers that enable high-speed communication between data centers.

[0009] According to this disclosure, it is possible to provide optical fibers that enable high-speed communication between data centers.

[0010] Embodiments of the present disclosure will now be described. (1) An optical fiber according to a first aspect of the present disclosure is an optical fiber comprising a germanium-containing core, an inner cladding surrounding the core, a trench surrounding the inner cladding, and an outer cladding surrounding the trench, wherein the relative refractive index difference of the core is Δ1, the relative refractive index difference of the inner cladding is Δ2, the relative refractive index difference of the trench is Δ3, the relative refractive index difference of the outer cladding is Δ4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, then the following relationships hold: 2.2 ≤ r2 / r1 ≤ 3.6 3 μm ≤ r3 - r2 ≤ 12 μm 0.25% ≤ Δ1 - Δ2 ≤ 0.50% -0.70% ≤ Δ3 ≤ -0.10% The zero-dispersion wavelength is 1296 nm or more and 1306 nm or less, and the zero-dispersion slope is 0.088 ps / nm ２ The density is less than / km, the cable cutoff wavelength for 500m is 1260nm or less, and the bending loss for light at a wavelength of 1310nm when wound around a mandrel with a diameter of 15mm is 0.5dB / turn or less. For the above optical fiber, the zero-dispersion slope is 0.088 ps / nm. ２ Because the wavelength is less than / km, the difference between the maximum and minimum values ​​of dispersion in the CWDM wavelength range can be reduced. This reduces signal distortion at both ends of the four wavelengths. Therefore, high-speed communication becomes possible. Since the cable cutoff wavelength for 500m is 1260nm or less, the optical fiber can function as a single-mode optical fiber in optical communication between data centers with a length of 500m or more. For these reasons, high-speed communication between data centers is possible. In the wavelength band mainly used, the loss when bent can be reduced.

[0011] (2) In (1) above, the mode field diameter at a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less, the transmission loss at a wavelength of 1310 nm is 0.40 dB / km or less, the transmission loss at a wavelength of 1383 nm is 0.40 dB / km or less, the bending loss for light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 60 mm is 0.1 dB / 100 turns or less, and the bending loss for light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 100 mm is 1.0 × 10 －４ The dB / turn may be less than or equal to the cable cutoff wavelength. In this case, parameters other than the cable cutoff wavelength conform to the ITU-T standard G. 652. D. Therefore, it functions as a general-purpose single-mode optical fiber.

[0012] (3) In (1) or (2) above, the bending loss for all light wavelengths between 1271 nm and 1331 nm when wound around a mandrel with a diameter of 15 mm may be 0.5 dB / turn or less. In this case, the bending loss is low across the entire wavelength range of the CWDM method.

[0013] (4) In any of (1) to (3) above, the bending loss for light with a wavelength of 1310 nm when wound around a mandrel with a diameter of 15 mm may be 0.1 dB / turn or less. In this case, the bending loss can be further reduced.

[0014] (5) In any of (1) to (4) above, the core may further contain chlorine, and the respective contents of germanium and chlorine in the core may be 100 ppm or more. In this case, the addition of germanium increases the refractive index difference between the core and the cladding. The addition of chlorine reduces the number of OH groups. These factors further reduce transmission loss.

[0015] (6) In any of (1) to (5) above, the transmission loss at a wavelength of 1310 nm may be 0.32 dB / km or less. In this case, high-speed communication with low transmission loss is possible.

[0016] (7) In any of (1) to (6) above, the mode field diameter at a wavelength of 1310 nm may be 8.8 μm or more and 9.6 μm or less. In this case, connection loss can be reduced.

[0017] (8) An optical fiber according to a second aspect of the present disclosure is an optical fiber comprising a germanium-containing core, an inner cladding surrounding the core, a trench surrounding the inner cladding, and an outer cladding surrounding the trench, wherein the relative refractive index difference of the core is Δ1, the relative refractive index difference of the inner cladding is Δ2, the relative refractive index difference of the trench is Δ3, the relative refractive index difference of the outer cladding is Δ4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, then the following relationships hold: 2.2 ≤ r2 / r1 ≤ 3.0 5 μm ≤ r3 - r2 ≤ 9 μm 0.30% ≤ Δ1 - Δ2 ≤ 0.40% -0.10% ≤ Δ2 ≤ -0.03% -0.40% ≤ Δ3 ≤ -0.15% The cutoff wavelength of the 500m cable is 1260nm or less, and the bending loss for light at a wavelength of 1310nm when wound around a 15mm diameter mandrel is 0.5dB / turn or less. In the above optical fiber, -0.10% ≤ Δ2 ≤ -0.03%, resulting in a zero dispersion slope of 0.088 ps / nm. ２ Since the wavelength can be reduced to less than / km, the difference between the maximum and minimum values ​​of dispersion in the CWDM wavelength range can be reduced. This reduces signal distortion at both ends of the four wavelengths. Therefore, high-speed communication becomes possible. Since the cutoff wavelength of a 500m cable is 1260nm or less, the optical fiber can function as a single-mode optical fiber in optical communication between data centers with a length of 500m or more. For these reasons, high-speed communication between data centers is possible. In the wavelength band mainly used, the loss when the cable is bent can be reduced.

[0018] (9) In any of (1) to (8) above, the cable cutoff wavelength for 22m may be longer than 1260nm. In this case, the optical fiber does not operate in single mode at 22m and is normally discarded. Using such an optical fiber can reduce waste and lower manufacturing costs.

[0019] [Details of Embodiments of the Disclosure] Specific examples of optical fibers of the Disclosure are described below with reference to the drawings. The Disclosure is not limited to these examples, and is intended to include all changes within the meaning and scope of the claims, as indicated by the claims. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0020] Figure 1 shows a cross-section perpendicular to the axial direction of an optical fiber 10 according to one embodiment. As shown in Figure 1, the optical fiber 10 comprises a glass fiber 13 and a resin coating layer 16. The optical fiber 10 is a so-called optical fiber core.

[0021] The glass fiber 13 comprises a core 11 and a cladding 12. The cladding 12 surrounds the core 11. The cladding 12 comprises an inner cladding 121, a trench 122, and an outer cladding 123. The inner cladding 121 surrounds the core 11 and is in contact with the outer surface of the core 11. The trench 122 surrounds the inner cladding 121 and is in contact with the outer surface of the inner cladding 121. The outer cladding 123 surrounds the trench 122 and is in contact with the outer surface of the trench 122. By having such a four-layer structure including the trench 122, the optical fiber 10 has a high effect in confining light within the core 11. As a result, bending loss can be reduced.

[0022] The radius of the core 11 is the distance from the central axis of the optical fiber 10 to the outer surface of the core 11. The radius of the inner cladding 121 is the distance from the central axis of the optical fiber 10 to the outer surface of the inner cladding 121. The radius of the trench 122 is the distance from the central axis of the optical fiber 10 to the outer surface of the trench 122. The radius of the outer cladding 123 is the distance from the central axis of the optical fiber 10 to the outer surface of the outer cladding 123. The radius of the outer cladding 123 is also the radius of the glass fiber 13 and the radius of the cladding 12.

[0023] Let the radii of the core 11, inner cladding 121, trench 122, and outer cladding 123 be r1, r2, r3, and r4, respectively. The outer diameter of the core 11 (2r1) is, for example, 7.8 μm or more and 9.0 μm or less. The outer diameter of the inner cladding 121 (2r2) is, for example, 18.4 μm or more and 25.2 μm or less. The outer diameter of the trench 122 (2r3) is, for example, 28.8 μm or more and 39.2 μm or less. The outer diameter of the outer cladding 123 (2r4) is, for example, 124 μm or more and 126 μm or less. In this specification, the "outer diameter" of an element is, for example, the average value of the outer diameter of that element at multiple positions in the axial direction of the optical fiber.

[0024] The glass fiber 13 is made of quartz glass. The core 11 is made of quartz glass with added germanium (Ge). In other words, the core 11 contains germanium. The addition of germanium increases the refractive index of the core 11, thus increasing the refractive index difference between the core 11 and the cladding 12. As a result, transmission loss can be reduced.

[0025] The core 11 may be formed from quartz glass co-doped with germanium and chlorine (Cl). That is, the core 11 may contain germanium and chlorine. The respective contents of germanium and chlorine in the core 11 are, for example, 100 ppm or more. By adding chlorine, the number of OH groups is reduced, so the optical fiber 10 can be made into a low-OH fiber with a low OH group content. This further reduces transmission loss.

[0026] The inner cladding 121 is made of quartz glass to which chlorine has been added; that is, the inner cladding 121 contains chlorine. The trenches 122 are made of quartz glass to which fluorine (F) has been added; that is, the trenches 122 contain fluorine. The outer cladding 123 is made of pure quartz glass that is substantially free of impurities.

[0027] The resin coating layer 16 surrounds the glass fiber 13. The resin coating layer 16 includes a primary resin layer 14 and a secondary resin layer 15. The primary resin layer 14 covers the outer peripheral surface of the outer cladding 123 and is in contact with the outer peripheral surface of the outer cladding 123. The secondary resin layer 15 covers the outer peripheral surface of the primary resin layer 14 and is in contact with the outer peripheral surface of the primary resin layer 14. The outer diameter of the primary resin layer 14 is, for example, 150 μm or more and 200 μm or less. The outer diameter of the secondary resin layer 15 is, for example, 165 μm or more and 250 μm or less.

[0028] Figure 2 is a diagram showing the refractive index distribution in the radial direction of the glass fiber 13. In FIG. 2, the range E1 corresponds to the core 11, the range E2 corresponds to the inner cladding 121, the range E3 corresponds to the trench 122, and the range E4 corresponds to the outer cladding 123, respectively. The vertical axis represents the relative refractive index difference, and the horizontal axis represents the radial position. As shown in FIG. 2, in the glass fiber 13, let the relative refractive index differences of the core 11, the inner cladding 121, the trench 122, and the outer cladding 123 with respect to the refractive index of pure silica glass be Δ1, Δ2, Δ3, and Δ4, respectively. The relative refractive index differences Δ1, Δ2, Δ3, and Δ4 are defined by the following mathematical formulas. Δ1(%) = (((n1 ２ - n0 ２ ) / (2 × n1 ２ )) × 100 Δ2(%) = (((n2 ２ - n0 ２ ) / (2 × n2 ２ )) × 100 Δ3(%) = (((n3 ２ - n0 ２ ) / (2 × n3 ２ )) × 100 Δ4(%) = (((n4 ２ - n0 ２ ) / (2 × n4 ２ )) × 100

[0029] n0 is the refractive index of the pure quartz glass. n1 is the refractive index of the core 11. n1 is, for example, the maximum refractive index of the core 11. n2 is the refractive index of the inner cladding 121. In the inner cladding 121, the refractive index decreases continuously as it moves away from the core 11 and approaches the trench 122. Therefore, n2 is, for example, the average refractive index in the range from 0.6 to 0.8 times the thickness of the inner cladding 121, i.e., the range of radii from r1 + 0.6 × (r2 - r1) to r1 + 0.8 × (r2 - r1). n3 is the refractive index of the trench 122. n3 is, for example, the minimum refractive index of the trench 122. n4 is the refractive index of the outer cladding 123. n4 is, for example, the average refractive index of the outer cladding 123. The relative refractive index difference is evaluated, for example, using a refractive index distribution measuring device (IFA-100 manufactured by Interfiber Analysis Co., Ltd.) with a measurement interval of 0.2 μm or less.

[0030] The refractive index of core 11 is higher than that of inner cladding 121 and outer cladding 123 (n1 > n2 and n1 > n4). The refractive index of trench 122 is lower than that of inner cladding 121 and outer cladding 123 (n3 < n2 and n3 < n4).

[0031] For example, the following relationships hold true for optical fiber 10: 0.25% ≤ Δ1 - Δ2 ≤ 0.50% -0.10% ≤ Δ2 ≤ 0.00% -0.70% ≤ Δ3 ≤ -0.10% 2.2 ≤ r2 / r1 ≤ 3.6 3 μm ≤ r3 - r2 ≤ 12 μm For example, Δ1 - Δ2 is 0.36%. For example, Δ1 is 0.33%. For example, Δ2 is -0.03%. For example, Δ3 is -0.30%. For example, Δ4 is ​​0.00%. For example, r2 / r1 is 2.6. For example, r3 - r2 is 5.0 μm. For example, 2r1 is 9.0 μm. For example, 2r2 is 23.4 μm. For example, 2r3 is 33.4 μm. For example, 2r4 is 125.0 μm. In these cases, r2 / r1 ≥ 2.2 allows the zero-dispersion wavelength to be 1296 nm or greater. In these cases, r2 / r1 ≤ 3.6 allows the zero-dispersion wavelength to be 1306 nm or less.

[0032] In the optical fiber 10, the following relationships may hold. 0.30% ≤ Δ1 - Δ2 ≤ 0.40% -0.10% ≤ Δ2 ≤ -0.03% -0.40% ≤ Δ3 ≤ -0.15% 2.6 ≤ r2 / r1 ≤ 3.0 5 μm ≤ r3 - r2 ≤ 9 μm As an example, Δ1 - Δ2 is 0.36%. As an example, Δ1 is 0.31%. As an example, Δ2 is -0.05%. As an example, Δ3 is -0.25%. As an example, Δ4 is 0.00%. As an example, r2 / r1 is 2.8. As an example, r3 - r2 is 7.0 μm. As an example, 2r1 is 9.0 μm. As an example, 2r2 is 25.2 μm. As an example, 2r3 is 39.2 μm. As an example, 2r4 is 125.0 μm.

[0033] The λcc of the 22 m of the optical fiber 10 is longer than 1260 nm. That is, the λcc of the optical fiber 10 does not conform to ITU-T standards G.652.D and G.657.A2. The λcc of the 500 m of the optical fiber 10 is 1260 nm or less. Even if the λcc of the 22 m of the optical fiber 10 is out of specification, if the optical fiber 10 is actually used for 500 m or more, the higher-order mode (LP11) will not be transmitted. Therefore, the optical fiber 10 operates as a single mode. The λcc of the 500 m of the optical fiber 10 is, for example, 1240 nm. The λcc of the 2 km of the optical fiber 10 is 1238 nm. The λcc of 500 m and 2 km is calculated, for example, by collecting the λcc statistical data of the same optical fiber of 22 m, 500 m, and 2 km, and these relationships and the measured value of the λcc of 22 m.

[0034] The standard deviation of the λcc of the 22 m of the optical fiber 10 is 10 nm or more. This standard deviation is calculated, for example, from the inspection data of 10,000 km of the optical fiber 10. As an example, the optical fiber 10 is wound around a small bobbin every 50 km, 22 m is cut and collected from the end (upper mouth) of the optical fiber 10 of each bobbin, and the λcc is measured. Thereby, the λcc of the 22 m of the optical fiber 10 can be inspected every 50 km. The standard deviation is calculated from the λcc data collected from the inspection data of 10,000 km of the optical fiber 10.

[0035] As an example, the zero-dispersion wavelength of the optical fiber 10 is 1307 nm or more and 1317 nm or less. In this case, the standard deviation of the zero-dispersion wavelength of the optical fiber 10 is 1.6 nm or less. The zero-dispersion wavelength of the optical fiber 10 may be 1311 nm or more and 1313 nm or less. In this case, the standard deviation of the zero-dispersion wavelength of the optical fiber 10 is 1.0 nm or less. In this case, the zero-dispersion slope of the optical fiber 10 is 0.088 ps / nm ２ / km or less. The zero-dispersion slope is the dispersion slope at the zero-dispersion wavelength.

[0036] As another example, the zero-dispersion wavelength of the optical fiber 10 is 1296 nm or more and 1306 nm or less. In this case, the standard deviation of the zero-dispersion wavelength of the optical fiber 10 is 1.6 nm or less. The zero-dispersion wavelength of the optical fiber 10 may be 1300 nm or more and 1302 nm or less. In this case, the standard deviation of the zero-dispersion wavelength of the optical fiber 10 is 1.0 nm or less. In this case, the zero-dispersion slope of the optical fiber 10 is 0.088 ps / nm ２ / km or less.

[0037] In the optical fiber 10, the mode field diameter (hereinafter, MFD) for light with a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less, and complies with ITU-T standard G.652.D. The MFD for light with a wavelength of 1310 nm may be 8.8 μm or more and 9.6 μm or less, or may be 8.8 μm or more and 9.4 μm or less. The MFD is defined by Petermann-II.

[0038] The bending loss for light with a wavelength of 1310 nm when the optical fiber 10 is wound around a mandrel with a diameter of 15 mm may be 0.5 dB / turn or less, or may be 0.1 dB / turn or less. The bending loss for all light with wavelengths from 1271 nm to 1331 nm when the optical fiber 10 is wound around a mandrel with a diameter of 15 mm may be 0.5 dB / turn or less, or may be 0.1 dB / turn or less. Here, all light with wavelengths from 1271 nm to 1331 nm means light in the full wavelength range from 1271 nm to 1331 nm.

[0039] The bending loss of optical fiber 10 with respect to light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 60 mm is 0.1 dB / 100 turns or less, conforming to ITU-T standard G. 652. D. The bending loss of optical fiber 10 with respect to light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 100 mm is 1.0 × 10⁻⁶. －４ The value is less than dB / turn. This ensures that the ground mode (LP01) optical signal is reliably confined to the core 11. The bending loss for light at a wavelength of 1625 nm when the optical fiber 10 is wound around a mandrel with a diameter of 100 mm can be determined, for example, by extrapolating from the bending diameter dependence of the bending loss when the bending diameter (diameter of the mandrel) is changed from 20 mm to 60 mm.

[0040] In optical fiber 10, the dispersion value for all light with wavelengths between 1271 nm and 1331 nm over a length of 2 km is between -10 ps / nm and 0 ps / nm. Here, the dispersion value refers to the value of wavelength dispersion.

[0041] In optical fiber 10, the transmission loss at a wavelength of 1310 nm is 0.40 dB / km or less, and may be 0.32 dB / km or less. The transmission loss at a wavelength of 1383 nm is 0.40 dB / km or less. There is an absorption peak of OH groups at a wavelength of 1383 nm. The low transmission loss of optical fiber 10 at a wavelength of 1383 nm indicates that optical fiber 10 is a low-OH fiber. The transmission losses of optical fiber 10 at wavelengths of 1310 nm and 1383 nm conform to ITU-T standard G. 652. D, respectively.

[0042] Figure 3 is a graph showing the dispersion value assuming a 400 Gbit / s × 2 km transmission over optical fiber for sample 1-1. Figure 4 is a graph showing the dispersion value assuming a 400 Gbit / s × 2 km transmission over optical fiber for sample 1-2. In Figures 3 and 4, the horizontal axis represents wavelength [nm], and the vertical axis represents dispersion value [ps / nm / km]. Figures 3 and 4 show a wavelength range of 1264.5 nm to 1337.5 nm as the communication wavelength band for the 400G-FR4 standard. The 400G-FR4 standard uses four wavelength bands with center wavelengths of 1271 nm, 1291 nm, 1311 nm, and 1331 nm, and within ±2.5 nm of the center wavelength. Therefore, the lower limit of the communication wavelength band for the 400G-FR4 standard is 1264.5 nm, and the upper limit is 1337.5 nm.

[0043] As shown in Figures 3 and 4, the optical fibers of Sample 1-1 and Sample 1-2 both have a zero-dispersion wavelength center of 1312 nm. Figure 3 shows the upper and lower limits of the zero-dispersion wavelength according to ITU-T standard G. 657. A2. Thus, in the comparative example, the difference between the upper and lower limits of the zero-dispersion wavelength according to ITU-T standard G. 657. A2 is large. Therefore, the difference between the maximum and minimum values ​​of dispersion is amplified not only by the wide wavelength range but also by manufacturing variations in the optical fibers. In contrast, the optical fiber of Sample 1-2 shown in Figure 4 has a small difference between the upper and lower limits of the zero-dispersion wavelength. Therefore, the difference between the maximum and minimum values ​​of dispersion can be narrowed. As a result, signal distortion can be reduced.

[0044] Figure 5 is a table summarizing the structural parameters and optical properties of optical fibers. The table shows the structural parameters and the optical properties obtained by simulation based on those structural parameters for optical fibers of samples 1, 2, 3, 4, and 5. Samples 1 to 3 are examples. Samples 4 and 5 are comparative examples and have a typical structure compliant with the ITU-T standard. In the comparative example optical fibers, the λcc at 22m is 1260nm or less. In contrast, in samples 1 and 3, the λcc at 22m exceeds 1260nm and does not comply with the ITU-T standard.

[0045] The chromatic dispersion value for light at a wavelength of 1310 nm at 2 km is within the range of -10 ps / nm to 0 ps / nm for optical fibers samples 1 to 3, but outside this range for optical fibers samples 4 and 5. Therefore, in optical fibers samples 4 and 5, power consumption due to signal processing in the light receiving section increases during high-speed communication. For this reason, the relative refractive index difference Δ2 of the inner cladding may be set to 0.00% or less. If -0.10% ≤ Δ2 ≤ -0.03%, it is easier to keep the chromatic dispersion value for light at a wavelength of 1310 nm at 2 km within the range of -10 ps / nm to 0 ps / nm. The zero-dispersion wavelength is within the range of 1296 nm to 1306 nm for optical fibers samples 1 to 3, but outside this range for optical fibers samples 4 and 5. For optical fibers samples 1 to 3, the zero-dispersion wavelength is between 1296 nm and 1306 nm, and the zero-dispersion slope is 0.088 ps / nm. ２ Since it is less than / km, the wavelength dispersion value for light with a wavelength of 1310 nm at 2 km falls within the range of -10 ps / nm to 0 ps / nm.

[0046] A fiber optic cable for Sample 11 was manufactured using the structure of the fiber optic cable for Sample 1 as the design value, and its wavelength dispersion value was measured. A fiber optic cable for Sample 41 was manufactured using the structure of the fiber optic cable for Sample 4 as the design value, and its wavelength dispersion value was measured.

[0047] Figure 6 shows the frequency distribution (histogram) of dispersion values ​​during transmission over 2 km. The wavelength range is from 1271 nm to 1331 nm. The number of samples for both Sample 11 and Sample 41 is 200 (N=200). For the optical fibers of Sample 11, it was confirmed that the chromatic dispersion value was within the range of -10 ps / nm to 0 ps / nm. For all optical fibers of Sample 41, it was confirmed that the chromatic dispersion value was less than -10 ps / nm.

[0048] While embodiments and modifications have been described above, this disclosure is not necessarily limited to the embodiments and modifications described herein, and various modifications are possible without departing from the spirit thereof. The embodiments and modifications described above may be combined as appropriate. Although optical communication between data centers has been described above as an example, the applications of the optical fibers in this disclosure are not limited to optical communication between data centers. It should be understood that at least one configuration or feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways. The scope of the present invention is indicated by the claims, not in the sense described above, and all modifications are intended to be included in the sense and scope equivalent to the claims.

[0049] 10...Optical fiber 11...Core 12...Cladding 13...Glass fiber 14...Primary resin layer 15...Secondary resin layer 16...Resin coating layer 121...Inner cladding 122...Trench 123...Outer cladding E1, E2, E3, E4...Range r1, r2, r3, r4...Radius Δ1, Δ2, Δ3, Δ4...Difference in refractive index

Claims

1. An optical fiber comprising: a germanium-containing core; an inner cladding surrounding the core; a trench surrounding the inner cladding; and an outer cladding surrounding the trench, wherein the relative refractive index difference of the core is Δ1, the relative refractive index difference of the inner cladding is Δ2, the relative refractive index difference of the trench is Δ3, the relative refractive index difference of the outer cladding is Δ4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, then the following relationships hold: 2.2 ≤ r2 / r1 ≤ 3.6 3 μm ≤ r3 - r2 ≤ 12 μm 0.25% ≤ Δ1 - Δ2 ≤ 0.50% -0.70% ≤ Δ3 ≤ -0.10% The zero-dispersion wavelength is 1296 nm or more and 1306 nm or less, and the zero-dispersion slope is 0.088 ps / nm ２ An optical fiber having a length of less than / km, a cable cutoff wavelength of 1260 nm or less for 500 m of cable, and a bending loss of 0.5 dB / turn or less for light at a wavelength of 1310 nm when wound around a mandrel with a diameter of 15 mm.

2. The mode field diameter at a wavelength of 1310 nm is between 8.2 μm and 9.6 μm, the transmission loss at a wavelength of 1310 nm is 0.40 dB / km or less, the transmission loss at a wavelength of 1383 nm is 0.40 dB / km or less, the bending loss for light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 60 mm is 0.1 dB / 100 turns or less, and the bending loss for light at a wavelength of 1625 nm when wound around a mandrel with a diameter of 100 mm is 1.0 × 10⁻⁶ －４ The optical fiber according to claim 1, wherein the dB / turn is less than or equal to dB.

3. The optical fiber according to claim 1 or claim 2, wherein the bending loss for all light wavelengths between 1271 nm and 1331 nm when wound around a mandrel with a diameter of 15 mm is 0.5 dB / turn or less.

4. The optical fiber according to any one of claims 1 to 3, wherein the bending loss for light with a wavelength of 1310 nm when wound around a mandrel with a diameter of 15 mm is 0.1 dB / turn or less.

5. The optical fiber according to any one of claims 1 to 4, wherein the core further contains chlorine, and the respective contents of germanium and chlorine in the core are 100 ppm or more.

6. The optical fiber according to any one of claims 1 to 5, wherein the transmission loss at a wavelength of 1310 nm is 0.32 dB / km or less.

7. The optical fiber according to any one of claims 1 to 6, wherein the mode field diameter at a wavelength of 1310 nm is 8.8 μm or more and 9.6 μm or less.

8. An optical fiber comprising: a germanium-containing core; an inner cladding surrounding the core; a trench surrounding the inner cladding; and an outer cladding surrounding the trench, wherein the relative refractive index difference of the core is Δ1, the relative refractive index difference of the inner cladding is Δ2, the relative refractive index difference of the trench is Δ3, the relative refractive index difference of the outer cladding is Δ4, the outer diameter of the core is 2r1, the outer diameter of the inner cladding is 2r2, the outer diameter of the trench is 2r3, and the outer diameter of the outer cladding is 2r4, then the following relationships hold: 2.2 ≤ r2 / r1 ≤ 3.0 5 μm ≤ r3 - r2 ≤ 9 μm 0.30% ≤ Δ1 - Δ2 ≤ 0.40% -0.10% ≤ Δ2 ≤ -0.03% -0.40% ≤ Δ3 ≤ -0.15% The cutoff wavelength of a 500 m cable is 1260 nm or less, An optical fiber with a bending loss of 0.5 dB / turn or less for light at a wavelength of 1310 nm when wound around a mandrel with a diameter of 15 mm.

9. The optical fiber according to any one of claims 1 to 8, wherein the 22 m cable cutoff wavelength is longer than 1260 nm.

Images