KR100693638B1 - Bending Robust Fiber Optics - Google Patents

Abstract

The present invention relates to an optical fiber with improved bend loss characteristics, which is a single mode optical fiber having a core and a clad, and satisfies an α-profile in which the refractive index of the core region increases toward the center of the core, and the core region of the core. It has a specific refractive index difference Δ ₁ at, and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Moreover, the mode field diameter at 1310 nm wavelength is 8.6 micrometers or less, the zero dispersion wavelength is 1320 nm or more, and the dispersion in 1550 nm wavelength is 17 ps / nm-km or less. Therefore, even in a severe bending environment, it can be laid without deterioration of transmission characteristics.

Optical fiber, bending loss, refractive index profile

Description

Bent Robust Fiber Optics {OPTICAL FIBER INSENSITIVE TO BENDING}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a graph illustrating a stepped refractive index profile of a conventional single mode optical fiber.

2 is a graph illustrating a refractive index profile of a single mode optical fiber according to the present invention.

3A to 3D are graphs showing changes in mode field diameters at 1310 nm wavelengths according to changes in the structural parameters of the optical fiber according to the present invention.

4A to 4D are graphs showing changes in dispersion at 1550 nm wavelength according to changes in four structural parameters of the optical fiber according to the present invention.

5A to 5D are graphs showing the change in bending loss at 1550 nm wavelength according to the change of four structural parameters of the optical fiber according to the present invention.

6A to 6D are graphs showing bending loss at a wavelength of 1550 nm of an optical fiber according to embodiments of the present invention and a comparative example.

7A to 7D are graphs showing bending loss at a wavelength of 1625 nm of the optical fiber according to the embodiments of the present invention and the comparative example.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical fibers, and more particularly to single mode optical fibers with improved bend loss characteristics.

Optical fibers have better transmission loss and bandwidth characteristics than copper wires or polymer optical fibers, but are difficult to handle when housing or laying. In particular, the bending loss is a problem, which means that when the optical fiber is bent, the field of the basic mode is out of the center of the core, and part of the optical power that goes to the core does not proceed along the optical fiber and is lost. When the optical fiber is wound to a certain bending radius, the power is continuously discharged from the wound portion, and when the basic mode of the bent fiber proceeds to the straight fiber again, the shape of the field is inconsistent at the interface, so part of the optical power is lost.

On the other hand, in the FTTH (Fiber To The Home) service, a lot of small bends are generated in the housing and the installation, and the connection parts such as an optical fiber junction box (organizer or tray) with a small bending radius should be installed in close contact with the corners. Conventional general optical fibers are difficult to use because of their high bending loss.

Bending losses are generally known to be smaller for optical fibers with smaller mode field diameters and larger cutoff wavelengths. However, the cutoff wavelength is determined within the range of operation in the single mode at the transmission wavelength, and the cutoff wavelength and the mode field diameter are determined by the standard. For example, the standard ITU-T (International Telecommunications Union-Telecommunication Standardization Sector) sets the cable cutoff wavelength to 1260 nm or less, and the mode field diameter of the 1310 nm wavelength to 8.6 to 9.5 mu m. In addition, in the case of commercial general single mode optical fiber, in addition to the cable cutoff wavelength, the 2m optical cutoff wavelength usually satisfies 1330nm or less. On the other hand, the bending loss presented in the standard ITU-T is less than 0.5 dB at a wavelength of 1625 nm when wound 100 times with a bending radius of 30 mm. In the case of commercial single-mode fiber, the bending loss is limited to less than 0.1dB at 1625nm when wound 100 times with 25mm bending radius, and less than 0.5dB at 1550nm when winding once with 16mm bending radius.

Bending loss is also affected by the refractive index profile. FIG. 1 is a graph illustrating a refractive index profile of a conventional single mode optical fiber, and the conventional single mode optical fiber shows a stepped refractive index profile having a constant refractive index regardless of a radius in the core region 10. The stepped refractive index profile can be represented by the core radius r _core and the specific refractive index difference Δ _core . In the stepped refractive profile, the field is close to Gaussian. On the other hand, in the case of a refractive index profile in which the refractive index increases toward the center of the core, the field changes to a form in which power is limited to the center of the core rather than a Gaussian form. Therefore, in a profile in which the refractive index increases toward the core center, even if the optical fiber is bent, only a relatively small amount of power exits the optical fiber, thereby reducing the bending loss. Japanese Patent Laid-Open Nos. Hei 1-69410, Hei 11-64665 and 2002-318315 disclose an optical fiber using such a refractive index profile. However, these optical fibers disclosed in Japanese Patent Laid-Open do not satisfy satisfactory bending loss characteristics, and do not satisfy all other optical transmission characteristics such as zero-dispersion wavelength, cut-off wavelength, dispersion, and mode field diameter to be considered in optical transmission.

Meanwhile, a wavelength division multiplexing (WDM) transmission system such as a dense wavelength division multiplexing (DWDM) system or a coarse wavelength division multiplexing (CWDM) system to increase transmission capacity uses not only the existing 1550 nm wavelength band but also the 1600 nm wavelength band. When the existing optical fiber optimized for the 1550 nm wavelength is used in the 1600 nm wavelength range, especially the mode field diameter is increased, the bending loss is increased. Therefore, in order to prevent degradation of transmission characteristics of the system due to increased bending loss, it is necessary to develop an optical fiber capable of suppressing bending loss equal to or less than the 1550 nm wavelength band even in the 1600 nm wavelength band.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical fiber with low bending loss in a wide wavelength range.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

The optical fiber according to the present invention for achieving the above object is a single mode optical fiber having a core and a clad, and the refractive index profile and the optical characteristic satisfy the following. That is, in the refractive index profile of the optical fiber according to the present invention, the refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, and has a specific refractive index difference Δ ₁ in the center region of the core. It has a specific refractive index difference Δ ₂ at radius r _core . Moreover, the mode field diameter at 1310 nm wavelength is 8.6 micrometers or less, a zero dispersion wavelength is 1320 nm or more, and dispersion in 1550 nm wavelength satisfies 17 ps / nm-km or less.

Where α has a positive constant value, n _max is the refractive index at the core center, and n _min is the refractive index at the core radius r _core .

The mode field diameter at the 1310 nm wavelength is preferably 5.9 to 8.6 탆, more preferably 6.5 to 8.0 탆, and the zero-dispersion wavelength is preferably 1330 to 1430 nm, more preferably 1340 to 1420 nm, and at 1550 nm. The dispersion is preferably 7 to 16 ps / nm-km.

Meanwhile, according to the present invention, the core radius r _core is 2.46 to 4.84 µm, the specific refractive index difference Δ ₁ in the core center region is 0.4053 to 0.7015%, and the specific refractive index difference Δ ₂ in the core radius r _core is 0.2268 to 0.4705%. Optical fibers of various embodiments in which α are in the range of 1.80 to 6.72 are provided, and the optical characteristics of the optical fiber according to each embodiment are optimized so that bending loss is suppressed to a predetermined range.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, various equivalents that may be substituted for them at the time of the present application It should be understood that there may be water and variations.

2 is a graph illustrating a refractive index profile of a single mode optical fiber according to the present invention.

Referring to FIG. 2, the optical fiber according to the present invention has a profile in which the refractive index changes in the radial direction in the core region 100. Specifically, by having a maximum refractive index n _max at the core center and a minimum refractive index n _min at the core radius r _core , the refractive index increases toward the center. In addition, the refractive index n (x) at an arbitrary position x in the radial direction in the core region 100 exhibits an α-profile satisfying Equation 1 above.

The refractive index of the clad 200 is the same as that of a conventional single mode optical fiber, and is the same as that of the silica tube 300 used as a base material and has a constant value. If the refractive index of the clad (= silica tube refractive index) is n _silica , the specific refractive index difference Δ ₁ , which is the difference between the refractive index at the _core and the clad refractive index, and the specific refractive index difference, which is the difference between the refractive index at the core radius r _core and the clad refractive index. Δ ₂ is obtained from the following equation.

On the other hand, the optical properties of the optical fiber according to the present invention changes as the parameters of Equations 1 and 2, that is, α, Δ ₁ , Δ ₂ , r _core changes. 3A to 5D show changes in bending field at 1550 nm wavelength after winding 10 times with a mode field diameter at 1310 nm wavelength, dispersion at 1550 nm wavelength, and bending radius 25 mm according to the change of these four optical fiber structural parameters. It is a graph shown.

3A to 4D, it can be seen that as Δ ₁ increases, the mode field diameter at 1310 nm and the dispersion at 1550 nm are smaller. Similarly, the larger α, the smaller the mode field diameter at 1310 nm wavelength and the dispersion at 1550 nm wavelength. On the other hand, the larger the core radius r _core , the larger the mode field diameter at 1310 nm wavelength and the dispersion at 1550 nm wavelength. On the other hand, there may be a section in which the mode field diameter and variance have a plurality of values for Δ ₁ and Δ ₂ of the same value (see FIGS. 3A, 3B, and 4B).

5A to 5D, it can be seen that the bending loss at 1550 nm wavelength is almost 0 dB when α, Δ ₁ , Δ ₂ , and r _core have a specific range of values, in particular Δ ₁ is 0.5% or more and α When 2 or more, the bending loss characteristic at 1550 nm wavelength is very good.

Meanwhile, embodiments of the present invention in which the refractive index profile of the core region follows the α-profile and the optical fiber structural parameters α, Δ ₁ , Δ ₂ , and r _core are optimized to have good bending loss characteristics. In addition, optical characteristics and bending loss of the conventional single mode optical fiber following the stepped refractive index profile as shown in FIG. 1 are also shown as comparative examples for comparison. Table 1 below shows the structural parameters and optical characteristics of the optical fiber according to the embodiments and comparative examples of the present invention, Table 2 shows the bending loss characteristics of these optical fibers.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Comparative example Optical fiber structure parameters α 6.26 5.32 4.91 4.09 3.08 2.30 2.38 2.66 - r _core (㎛) 3.06 3.17 3.29 3.48 3.63 3.87 4.05 4.24 4.40 Δ ₁ (%) 0.6015 0.5878 0.5642 0.5478 0.5379 0.5223 0.5053 0.5072 Δ _core = 0.36 Δ ₂ (%) 0.3705 0.3692 0.3614 0.3377 0.3455 0.3298 0.3299 0.3268 Optical properties Mode field diameter @ 1310nm (㎛) 6.67 6.80 6.98 7.18 7.36 7.64 7.85 7.97 9.12 Mode field diameter @ 1550nm (㎛) 7.68 7.80 7.98 8.18 8.35 8.64 8.83 8.89 10.65 Zero Dispersion Wavelength (nm) 1417 1404 1393 1380 1371 1361 1350 1341 1302 Dispersion @ 1550nm (ps / nm-km) 8.0 9.0 9.9 11.1 11.9 13.0 14.0 15.0 17.5 Blocking wavelength (nm) 1214 1237 1254 1287 1316 1356 1407 1479 1387

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Comparative example Bending Loss @ 1550nm (dB) R 30mm, 100 times 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0002 R 20 mm, 100 times 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1617 R 10mm, 10 times 0.1030 0.0969 0.1358 0.1340 0.1341 0.1685 0.1138 0.0304 14.5458 R 5mm, 1 time 2.3348 2.2806 2.7154 2.7343 2.7754 3.1491 2.6522 1.4283 35.2103 Bending Loss @ 1625nm (dB) R 30mm, 100 times 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0026 R 20 mm, 100 times 0.0006 0.0005 0.0007 0.0006 0.0006 0.0007 0.0003 0.0000 1.0128 R 10mm, 10 times 0.6202 0.5644 0.7268 0.6804 0.6511 0.7487 0.5018 0.1470 33.4833 R 5mm, 1 time 5.4740 5.2579 5.9971 5.8811 5.8342 6.3286 5.3058 2.9878 49.0242

As shown in Table 1, in Examples 1 to 8 of the present invention, the mode field diameter at 1310 nm is 6.7-8.0 μm, and the mode field diameter at 1550 nm has a value in the range of 7.7-8.9 μm. In addition, in Examples 1 to 8, the zero-dispersion wavelength is 1341 to 1417 nm, the dispersion at 1550 nm is 8.0 to 15.0 ps / nm-km, and the blocking wavelength is 1214 to 1479 nm. Compared with the conventional single mode optical fiber (comparative example), the mode field diameter was smaller, and the zero-dispersion wavelength shifted to the longer wavelength, resulting in less dispersion at 1550 nm wavelength. On the other hand, the cutoff wavelength has a value larger or smaller than that of the comparative example. The blocking wavelength is a theoretical value, and the 2m blocking wavelength of the actually manufactured optical fiber is generally shorter than 70-80 nm, and the cable blocking wavelength when the cable is manufactured is several tens of nm shorter than the 2m optical fiber blocking wavelength.

In order to evaluate the bending loss of the optical fiber, as shown in Table 2, the value when the bending radius (R) was reduced to 30 mm, 20 mm, 10 mm, and 5 mm, was calculated. When the optical fibers of Examples 1 to 8 were wound 100 times with a bending radius (R) of 30 mm at both wavelengths of 1550 nm and 1625 nm, it can be seen that the loss is almost 0.0dB. On the other hand, under the same conditions, the optical fiber of the comparative example showed almost no bending loss at 1550 nm wavelength but showed about 0.003 dB loss at 1625 nm wavelength. When the bending radius decreases to 20 mm, 10 mm, and 5 mm, the loss difference between the optical fibers of Examples 1 to 8 and the optical fibers of the comparative example increases rapidly. The optical fiber of Examples 1 to 8, when wound 100 times with a bending radius of 20 mm, has almost no loss at 1550 nm wavelength and is less than 0.001 dB at 1625 nm wavelength, while the comparative example is about 0.2 dB at 1550 nm wavelength and 1.0 dB at 1625 nm wavelength. . In addition, the bending loss of the optical fibers of Examples 1 to 8 after winding 10 times at a bending radius of 10 mm was 0.2 dB or less at 1550 nm wavelength and 1.0 dB or less at 1625 nm wavelength, while the comparative example was about 15 dB at 1550 nm wavelength and 35 dB at 1625 nm wavelength. Increase sharply. Further, the optical fiber of Examples 1 to 8 when wound once with a bending radius of 5 mm is 3 dB at 1550 nm wavelength and 7 dB or less at 1625 nm wavelength, whereas the comparative example rapidly increases to 35 dB at 1550 nm wavelength and 50 dB at 1625 nm wavelength.

6A to 7D are graphs illustrating the bending loss as described above. 6A to 6D are graphs showing bending loss at 1550 nm wavelength, and FIGS. 7A to 7D are graphs showing bending loss at 1625 nm wavelength. 6A and 7A are graphs showing the bending losses of Examples 1 to 8 and Comparative Examples, respectively. FIGS. 6B to 6D and 7B to 7D show the optical fibers of Examples 1 to 8 having a bending radius of 20 mm, respectively. The bending loss in the case of 100 windings, 10 windings at 10 mm, and 1 winding at 5 mm is shown on different scales.

It can be seen from FIGS. 6A to 7D that the bending loss of the optical fiber according to the embodiment of the present invention is significantly smaller than that of the optical fiber of the comparative example. In particular, it can be seen that the bending loss of the optical fiber according to the embodiment of the present invention does not show much difference, while the bending loss of the optical fiber of the comparative example decreases rapidly. On the other hand, it can be seen that among the optical fibers of Examples 1 to 8, the optical fiber of Example 8 has the least bending loss at all of the bending radii at both 1550 nm and 1625 nm wavelengths.

On the other hand, the results presented in the above table is a result obtained by simulation using a commercial structural design program, it may be different from the actual measured optical properties of the optical fiber manufactured. In addition, since the refractive index profiles of the conventional optical fiber of FIG. 1 and the optical fiber according to the embodiment of the present invention are fundamentally different, an error may occur when compared with an absolute value. However, the above results suggest a significant effect that the optical fiber of Examples 1 to 8 of the present invention has at least less bending loss than the optical fiber of the comparative example, the bending radius is smaller and the change in bending loss is not large even when the use wavelength band is increased. It must be.

Furthermore, each characteristic value of the optical fibers optimized in Examples 1 to 8 is excellent even within an appropriate error range, for example, ± 0.6 μm for r _core , ± 0.1% for Δ ₁ and Δ ₂ , and ± 0.5 for α. In addition to the optical properties, it is likely to exhibit sufficiently low bending loss characteristics.

Although the preferred embodiments of the present invention have been described as described above, the configuration shown in the embodiments and drawings described herein is only one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention. It should be understood that there may be various equivalents and modifications that can substitute for them at the time of the present application.

In the optical fiber of the present invention, the refractive index profile of the core region satisfies the α-profile, the refractive index difference Δ ₁ in the center region of the _core , and the refractive index difference Δ ₂ in the radius r _core of the _core , thereby resulting in bending loss compared to the conventional art. This is significantly reduced. Particularly, according to the optical fiber of the present invention, even if the bending radius decreases from 30 mm to 20 mm and the use wavelength increases from 1550 nm to 1625 nm, there is almost no difference in bending loss value. It is possible.

Claims (13)

delete delete delete A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.06 ± 0.6 µm and the Δ ₁ is 0.6015 ± 0.1% , Δ ₂ is 0.3705 ± 0.1%, and α is 6.26 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.17 ± 0.6 µm and the Δ ₁ is 0.5878 ± 0.1% , Δ ₂ is 0.3692 ± 0.1%, and α is 5.32 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.29 ± 0.6 µm and the Δ ₁ is 0.5642 ± 0.1%. , Δ ₂ is 0.3614 ± 0.1%, and α is 4.91 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.48 ± 0.6 µm, and the Δ ₁ is 0.5478 ± 0.1%. , Δ ₂ is 0.3377 ± 0.1%, and α is 4.09 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.63 ± 0.6 μm, and the Δ ₁ is 0.5379 ± 0.1%. , Δ ₂ is 0.3455 ± 0.1%, and α is 3.08 ± 0.5.

Where n _{max is} the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 3.87 ± 0.6 µm and the Δ ₁ is 0.5223 ± 0.1% , Δ ₂ is 0.3298 ± 0.1%, and α is 2.30 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 4.05 ± 0.6 µm and the Δ ₁ is 0.5053 ± 0.1%. , Δ ₂ is 0.3299 ± 0.1%, and α is 2.38 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . A single mode optical fiber having a core and a clad, The refractive index n (x) at a specific radial position x in the core of the optical fiber satisfies the following equation, has a specific refractive index difference Δ ₁ at the center of the _core and a specific refractive index difference Δ ₂ at the radius r _core of the _core . Mode field diameter at 1310 nm is 8.6 µm or less, zero dispersion wavelength is 1320 nm or more, dispersion at 1550 nm wavelength is 17 ps / nm-km or less, the r _core is 4.24 ± 0.6 µm and the Δ ₁ is 0.5072 ± 0.1% , Δ ₂ is 0.3268 ± 0.1%, and α is 2.66 ± 0.5.

Where n _max is the refractive index at the core center and n _min is the refractive index at the core radius r _core . The method according to any one of claims 4 to 11, The optical fiber according to claim 1310 nm has a mode field diameter of 5.9 to 8.6 탆, the zero dispersion wavelength of 1330 to 1430 nm, and the dispersion at the 1550 nm wavelength of 7 to 16 ps / nm-km. The method of claim 12, And a mode field diameter of 6.5 to 8.0 µm and a zero dispersion wavelength of 1340 to 1420 nm at the 1310 nm wavelength.

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