Optical fiber

Abstract

This optical fiber comprises a core that contains germanium, and a cladding that surrounds the core. The zero-dispersion wavelength of the optical fiber is 1307-1317 nm. The standard deviation of the zero-dispersion wavelength is 1.6 nm or less.

Description

fiber optic

[0001] This disclosure relates to optical fibers. This application claims priority under Japanese application No. 2024-232402, 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 from 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 and a cladding surrounding the core, wherein the zero-dispersion wavelength is 1307 nm or more and 1317 nm or less, and the standard deviation of the zero-dispersion wavelength is 1.6 nm or less.

[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. Figure 3 is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km using the optical fiber of the first comparative example. Figure 4 is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km using the optical fiber of the first embodiment. Figure 5 is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km using the optical fiber of the second comparative example. Figure 6 is a graph showing the dispersion value assuming a transmission of 400 Gbit / s × 2 km using the optical fiber of the second embodiment.

[0007] In the CWDM system, increasing the communication speed can lead to signal distortion at both ends of the four wavelength range due to the chromatic dispersion characteristics of the optical fiber used in the transmission line, resulting in reception problems. 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 from 1271 nm to 1331 nm is amplified not only by the wide wavelength range but also by manufacturing variations in the optical fiber.

[0008] The main cause of such manufacturing variations is the variation in Δn, which is the difference in refractive index between the core and the cladding. When Δn varies, the cable cutoff wavelength may not satisfy the ITU-T standard. Therefore, the core diameter is adjusted according to the variation in Δn so that the cable cutoff wavelength is a predetermined value. This adjustment increases the variation in the zero-dispersion wavelength. Conversely, if the core diameter is adjusted according to the variation in Δn so that the zero-dispersion wavelength is a predetermined value, the amount of discarded optical fibers whose cable cutoff wavelength does not satisfy the ITU-T standard increases. Thus, manufacturing costs increase.

[0009] This disclosure aims to provide an optical fiber with low manufacturing variability in zero-dispersion wavelength and the ability to reduce manufacturing costs.

[0010] According to this disclosure, it is possible to provide optical fibers with small manufacturing variations in zero-dispersion wavelength, thereby reducing manufacturing costs.

[0011] 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 and a cladding surrounding the core, wherein the zero-dispersion wavelength is 1307 nm or more and 1317 nm or less, and the standard deviation of the zero-dispersion wavelength is 1.6 nm or less. In the above optical fiber, since the standard deviation of the zero-dispersion wavelength is 1.6 nm or less, the manufacturing variation of the zero-dispersion wavelength is small. The cable cutoff wavelength of the ITU-T standard is measured using an optical fiber with a length of 22 m. Actual optical communication between data centers is carried out over distances of 500 m to 10 km. Generally, the longer the length of the optical fiber, the shorter the cable cutoff wavelength becomes, so if used over distances of 500 m to 10 km, an optical fiber that does not satisfy the ITU-T standard may operate as a single-mode optical fiber. This reduces the amount of discarded optical fibers that do not satisfy the ITU-T standard and reduces manufacturing costs.

[0012] (2) In (1) above, the standard deviation of the 22m cable cutoff wavelength may be 10 nm or more. In this case, the standard deviation of the zero-dispersion wavelength can be lowered.

[0013] (3) In (1) or (2) above, the cutoff wavelength of the 500m cable may be 1260nm or less. In this case, the 500m optical fiber can be operated as single-mode.

[0014] (4) In any of (1) to (3) above, the mode field diameter at a wavelength of 1310 nm may be 8.8 μm or more and 9.4 μm or less. In this case, the mode field diameter at a wavelength of 1310 nm conforms to ITU-T standard G. 652. D. Therefore, connection loss can be reduced.

[0015] (5) In any of (1) to (4) 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 is low, so the transmission loss can be reduced.

[0016] (6) In any of (1) to (5) above, the zero-dispersion wavelength is 1311 nm or more and 1313 nm or less, the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, and the zero-dispersion slope is 0.092 ps / nm ２ It may be less than / km. In this case, since the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, the manufacturing variation of the zero-dispersion wavelength is even smaller.

[0017] (7) An optical fiber according to a second aspect of the present disclosure is an optical fiber comprising a germanium-containing core and a cladding surrounding the core, wherein the zero-dispersion wavelength is 1296 nm or more and 1306 nm or less, and the standard deviation of the zero-dispersion wavelength is 1.6 nm or less. In the above optical fiber, since the standard deviation of the zero-dispersion wavelength is 1.6 nm or less, the manufacturing variation of the zero-dispersion wavelength is small. The cable cutoff wavelength of the ITU-T standard is measured using an optical fiber with a length of 22 m. Actual optical communication between data centers is carried out over distances of 500 m to 10 km. Generally, the longer the length of the optical fiber, the shorter the cable cutoff wavelength, so if used over distances of 500 m to 10 km, an optical fiber that does not satisfy the ITU-T standard may operate as a single-mode optical fiber. This reduces the amount of discarded optical fibers that do not satisfy the ITU-T standard and reduces manufacturing costs.

[0018] (8) In (7) above, the zero-dispersion wavelength is 1300 nm or more and 1302 nm or less, the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, and the zero-dispersion slope is 0.092 ps / nm ２ It may be less than / km. In this case, since the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, the manufacturing variation of the zero-dispersion wavelength is even smaller.

[0019] (9) In any of (1) to (8) above, the dispersion value for all light with wavelengths of 1271 nm to 1331 nm in a length of 2 km may be between -10 ps / nm and 0 ps / nm. In this case, for example, even if the communication speed is increased from 200 Gbit / Lane to 400 Gbit / Lane, the signal at both ends of the wavelength range is less likely to be distorted. Therefore, the power required for signal processing in the receiving unit can be reduced.

[0020] (10) In any of (1) to (8) above, the dispersion value for all light with wavelengths of 1271 nm to 1331 nm in a length of 10 km may be -15 ps / nm to 5 ps / nm. In this case, for example, even if the communication speed is increased from 200 Gbit / Lane to 400 Gbit / Lane, the signal at both ends of the wavelength range is less likely to be distorted. Therefore, the power required for signal processing in the receiving unit can be reduced.

[0021] [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.

[0022] As described above, if the core diameter is adjusted according to the variation in Δn, which is the refractive index difference between the core and cladding, so that the zero-dispersion wavelength becomes a predetermined value, the amount of discarded optical fibers whose cable cutoff wavelength (hereinafter referred to as λcc) does not satisfy the ITU-T standard will increase. The method for measuring the λcc of an optical fiber is defined by IEC standards, etc. Generally, the λcc of an optical fiber is measured by bending a 22m sample. Actual optical communication between data centers is carried out over distances of 500m to 10km. Generally, the longer the length of the optical fiber, the shorter the λcc becomes. Therefore, in this embodiment, instead of the λcc of 22m, standard values ​​for λcc of 500m, 2km, or 10km, which are closer to the actual usage environment, are set, and it is guaranteed that even if the λcc of 22m does not satisfy the ITU-T standard, there will be no problem in actual use.

[0023] In actual shipping conditions, optical fibers are typically shipped in lengths of around 50 km wound on a spool. Therefore, it is necessary to guarantee that any 500 m section of this 50 km optical fiber will reliably operate in single mode during actual use. Various methods can be considered to achieve this guarantee. One example is described below.

[0024] Step 1: Evaluate the correlation between the λcc of 22m and the λcc of 500m. Step 2: Predict the λcc of 22m of the optical fiber after drawing based on the inspection results of the refractive index distribution of the optical fiber matrix before drawing. Step 3: Take 22m samples from both ends of an actual 50km optical fiber wound on a bobbin, and measure the λcc of 22m. Step 4: For the λcc of 22m, calculate the difference between the predicted value from Step 2 and the measured value from Step 3, and calculate a correction value that makes the predicted value match the measured value. Use this correction value to obtain the predicted value of λcc of 500m in the longitudinal direction of the optical fiber. Step 5: If the total length of each bobbin conforms to the standard at 500m based on the predicted value in the longitudinal direction obtained in Step 4, the optical fiber in that bobbin is considered good quality.

[0025] Another example of the above guarantee method is as follows: Step 1: Evaluate the correlation between the λcc of 22m and the λcc of 500m. Step 2: Take 22m samples from both ends of a 50km optical fiber actually wound on a bobbin, for example, and measure the λcc of the 22m. Step 3: Using the correlation obtained in Step 1 and the measured value of the λcc of 22m obtained in Step 2, calculate the predicted value of the λcc of 500m at both ends of the bobbin. Step 4: If the predicted value of the λcc of 500m at both ends of the bobbin obtained in Step 3 conforms to the standard at both ends, the optical fiber in that bobbin is considered good quality.

[0026] 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.

[0027] 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. Because the glass fiber 13 has such a four-layer structure including the trench 122, the optical fiber 10 is more effective at confining light within the core 11. As a result, bending loss can be reduced.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 surface of the outer cladding 123 and is in contact with the outer surface of the outer cladding 123. The secondary resin layer 15 covers the outer surface of the primary resin layer 14 and is in contact with the outer surface of the primary resin layer 14. The outer diameter of the primary resin layer 14 is, for example, 150 μm to 200 μm. The outer diameter of the secondary resin layer 15 is, for example, 165 μm to 250 μm. This makes it possible to maintain sufficient strength with a diameter the same as or smaller than commonly used optical fibers. This also makes it possible to reduce microbend loss.

[0034] FIG. 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. 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

[0035] n0 is the refractive index of pure silica glass. n1 is the refractive index of the core 11. n'1 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 continuously decreases 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 times to 0.8 times the thickness of the inner cladding 121, that is, in the range of the radius 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 evaluation of the relative refractive index difference is performed, for example, using a refractive index distribution measuring device (IFA - 100 manufactured by Interfiber Analysis) with a measurement interval of 0.2 μm or less.

[0036] The refractive index of the core 11 is higher than the refractive index of the inner cladding 121 and the refractive index of the outer cladding 123 (n1 > n2 and n1 > n4). The refractive index of the trench 122 is lower than the refractive index of the inner cladding 121 and the refractive index of the outer cladding 123 (n3 < n2 and n3 < n4).

[0037] In the optical fiber 10, for example, the following relationships hold. 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 As an example, Δ1 - Δ2 is 0.36%. As an example, Δ1 is 0.33%. As an example, Δ2 is -0.03%. As an example, Δ3 is -0.30%. As an example, Δ4 is 0.00%. As an example, r2 / r1 is 2.6. As an example, r3 - r2 is 5.0 μm. As an example, 2r1 is 9.0 μm. As an example, 2r2 is 23.4 μm. As an example, 2r3 is 33.4 μm. As an example, 2r4 is 125.0 μm. In these cases, by r2 / r1 ≥ 2.2, the zero-dispersion wavelength can be made 1296 nm or more. In these cases, by r2 / r1 ≤ 3.6, the zero-dispersion wavelength can be made 1306 nm or less.

[0038] In the optical fiber 10, the following relationships may also 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.

[0039] The λcc of optical fiber 10 over 22m is longer than 1260nm. That is, the λcc of optical fiber 10 does not conform to ITU-T standards G. 652. D and G. 657. A2. The λcc of optical fiber 10 over 500m is 1260nm or less. Even if the λcc of optical fiber 10 over 22m is outside the standard, if the optical fiber 10 is used to a length of 500m or more, higher-order modes (LP11) will not be transmitted. Therefore, optical fiber 10 operates as a single-mode optical fiber. The λcc of optical fiber 10 over 500m is, for example, 1240nm. The λcc of optical fiber 10 over 2km is 1238nm. The λcc of optical fiber 10 over 10km is 1237nm. The λcc values ​​for 500m, 2km, and 10km are calculated, for example, by collecting λcc statistical data for the same optical fiber at lengths of 22m, 500m, 2km, and 10km, and then analyzing the relationships between these data and the measured λcc value for 22m.

[0040] The standard deviation of the λcc of a 22m length of optical fiber 10 is 10 nm or greater. This standard deviation is calculated, for example, from inspection data over 10,000 km of optical fiber 10. As an example, optical fiber 10 is wound onto small bobbins every 50 km, and 22m is cut and sampled from the end (top opening) of each bobbin, and the λcc is measured. This allows for the inspection of the λcc of 22m lengths of optical fiber 10 every 50 km. The standard deviation is then calculated from the λcc data collected from the inspection data over 10,000 km of optical fiber 10.

[0041] For example, the zero-dispersion wavelength of optical fiber 10 is between 1307 nm and 1317 nm. In this case, the standard deviation of the zero-dispersion wavelength of optical fiber 10 is 1.6 nm or less. The zero-dispersion wavelength of optical fiber 10 may also be between 1311 nm and 1313 nm. In this case, the standard deviation of the zero-dispersion wavelength of optical fiber 10 is 1.0 nm or less. In this case, the zero-dispersion slope of optical fiber 10 is 0.092 ps / nm. ２ It is less than / km. The zero-dispersion slope is the dispersion slope at the zero-dispersion wavelength. The zero-dispersion slope of optical fiber 10 is 0.090 ps / nm ２ It may be less than or equal to / km, and 0.088 ps / nm ２ It may be less than / km.

[0042] As another example, the zero-dispersion wavelength of optical fiber 10 is between 1296 nm and 1306 nm. In this case, the standard deviation of the zero-dispersion wavelength of optical fiber 10 is 1.6 nm or less. The zero-dispersion wavelength of optical fiber 10 may also be between 1300 nm and 1302 nm. In this case, the standard deviation of the zero-dispersion wavelength of optical fiber 10 is 1.0 nm or less. In this case, the zero-dispersion slope of optical fiber 10 is 0.092 ps / nm. ２ It is less than / km. The zero-dispersion slope of optical fiber 10 is 0.090 ps / nm ２ It may be less than or equal to / km, and 0.088 ps / nm ２ It may be less than / km.

[0043] In optical fiber 10, the mode field diameter (hereinafter referred to as MFD) for light with a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less, conforming to 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 8.8 μm or more and 9.4 μm or less. The MFD is defined by the Petermann-II equation.

[0044] The bending loss of optical fiber 10 with respect to 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 0.1 dB / turn or less. The bending loss of optical fiber 10 with respect to all light with wavelengths between 1271 nm and 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 0.1 dB / turn or less. Here, all light with wavelengths between 1271 nm and 1331 nm means light in the entire wavelength range between 1271 nm and 1331 nm.

[0045] 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. －４The 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.

[0046] 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. In optical fiber 10, the dispersion value for all light with wavelengths between 1271 nm and 1331 nm over a length of 10 km is between -15 ps / nm and 5 ps / nm.

[0047] 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.

[0048] Figure 3 is a graph showing the dispersion value assuming a 400 Gbit / s × 2 km transmission using an optical fiber in the first comparative example. Figure 4 is a graph showing the dispersion value assuming a 400 Gbit / s × 2 km transmission using an optical fiber in the first embodiment. 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. In the 400G-FR4 standard, four wavelength bands are used, with 1271 nm, 1291 nm, 1311 nm, and 1331 nm as the center wavelengths, 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.

[0049] In the optical fiber of the first comparative example shown in Figure 3, and the optical fiber of the first embodiment shown in Figure 4, the center of the zero-dispersion wavelength is 1312 nm. As shown in Figures 3 and 4, in the optical fiber of the first comparative example and the first embodiment, the center of the zero-dispersion wavelength is 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 optical fiber of the first 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 fiber. In contrast, in the optical fiber of the first embodiment shown in Figure 4, the difference between the upper and lower limits of the zero-dispersion wavelength is small. Therefore, the difference between the maximum and minimum values ​​of dispersion can be narrowed.

[0050] Figure 5 is a graph showing the dispersion values ​​assuming a 400 Gbit / s × 2 km transmission using the optical fiber of the second comparative example. Figure 6 is a graph showing the dispersion values ​​assuming a 400 Gbit / s × 2 km transmission using the optical fiber of the second embodiment. In both the optical fiber of the second comparative example shown in Figure 5 and the optical fiber of the second embodiment shown in Figure 6, the center of the zero-dispersion wavelength is 1312 nm. In the optical fiber of the second comparative example shown in Figure 5, the difference between the upper and lower limits of the zero-dispersion wavelength compliant with ITU-T standard G. 657. A2 is large. Therefore, the difference between the maximum and minimum dispersion values ​​is amplified not only by the wide wavelength range but also by manufacturing variations in the optical fiber. In contrast, in the optical fiber of the second embodiment shown in Figure 6, the difference between the upper and lower limits of the zero-dispersion wavelength is small. Therefore, the difference between the maximum and minimum dispersion values ​​can be narrowed.

[0051] Table 1 summarizes the availability of communication at a distance of 2 km, broken down by communication speed and variance. Table 2 summarizes the availability of communication at a distance of 10 km, broken down by communication speed and variance.

[0052]

[0053] As shown in Table 1, for a length of 2 km, if the variance is between -10 ps / nm and 0 ps / nm, both low-speed communication below 400 Gbit / Lane and high-speed communication above 400 Gbit / Lane can be handled with low power consumption. For a length of 2 km, if the variance is less than -10 ps / nm or greater than 0 ps / nm, low-speed communication is possible, but high-speed communication is not.

[0054] As shown in Table 2, for a length of 10 km, if the dispersion value is between -15 ps / nm and 5 ps / nm, both low-speed and high-speed communication can be handled with low power consumption. For a length of 10 km, if the dispersion value is less than -15 ps / nm or greater than 5 ps / nm, low-speed communication is possible, but high-speed communication is not.

[0055] 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. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. 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.

[0056] 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 and a cladding surrounding the core, wherein the zero-dispersion wavelength is 1307 nm or more and 1317 nm or less, and the standard deviation of the zero-dispersion wavelength is 1.6 nm or less.

2. The optical fiber according to claim 1, wherein the standard deviation of the cable cutoff wavelength for 22 m is 10 nm or more.

3. The optical fiber according to claim 1 or claim 2, wherein the cable cutoff wavelength for 500 m is 1260 nm or less.

4. The optical fiber according to any one of claims 1 to 3, wherein the mode field diameter at a wavelength of 1310 nm is 8.8 μm or more and 9.4 μm or less.

5. The optical fiber according to any one of claims 1 to 4, 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.

6. The zero-dispersion wavelength is between 1311 nm and 1313 nm, the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, and the zero-dispersion slope is 0.092 ps / nm. ２ An optical fiber according to any one of claims 1 to 5, wherein the length is less than or equal to / km.

7. An optical fiber comprising a germanium-containing core and a cladding surrounding the core, wherein the zero-dispersion wavelength is 1296 nm or more and 1306 nm or less, and the standard deviation of the zero-dispersion wavelength is 1.6 nm or less.

8. The zero-dispersion wavelength is between 1300 nm and 1302 nm, the standard deviation of the zero-dispersion wavelength is 1.0 nm or less, and the zero-dispersion slope is 0.092 ps / nm. ２ The optical fiber according to claim 7, wherein the length is less than or equal to / km.

9. The optical fiber according to any one of claims 1 to 8, wherein the dispersion value for all light with wavelengths between 1271 nm and 1331 nm at a length of 2 km is between -10 ps / nm and 0 ps / nm.

10. The optical fiber according to any one of claims 1 to 8, wherein the dispersion value for all light with wavelengths between 1271 nm and 1331 nm at a length of 10 km is between -15 ps / nm and 5 ps / nm.

Images