阅读说明：本技术 一种低色散单模光纤 (Low-dispersion single-mode optical fiber ) 是由 张磊 王瑞春 张睿 吴超 邓兰 周红燕 沈磊 罗杰 于 2019-10-29 设计创作，主要内容包括：本发明涉及一种低色散单模光纤,包括有纤芯层和包层,其特征在于芯层相对折射率差Δ1为0.30％～0.65％,半径R1为2.5μm～4.5μm,包层由内至外分为三个包层分层和一个外包层,包覆芯层的为第一包层分层,第一包层分层相对折射率差Δ2为-0.70％～-0.30％,半径R2为4.5μm～7.0μm,第二包层分层包覆第一包层分层,第二包层分层相对折射率差Δ3为-0.20％～0.25％,半径R3为7.0μm～12.0μm,第三包层分层包覆第二包层分层,第三包层分层相对折射率差Δ4为-0.60％～0.00％,半径R4为10.0μm～20.0μm；外包层包覆第三包层分层,外包层为纯二氧化硅玻璃层。该光纤光缆截止波长小于1260nm,在1260nm～1460nm波段整体色散较低,且衰减性能良好。特别地适用于1260nm～1460nm波段的WDM传输系统。(The invention relates to a low dispersion single mode fiber, which comprises a fiber core layer and a cladding, and is characterized in that the relative refractive index difference delta 1 of the core layer is 0.30-0.65%, the radius R1 is 2.5-4.5 mu m, the cladding is divided into three cladding layers and one cladding layer from inside to outside, the cladding core layer is a first cladding layer, the relative refractive index difference delta 2 of the first cladding layer is-0.70% -0.30%, the radius R2 is 4.5-7.0 mu m, a second cladding layer covers the first cladding layer, the relative refractive index difference delta 3 of the second cladding layer is-0.20-0.25%, the radius R3 is 7.0-12.0 mu m, a third cladding layer covers the second cladding layer, the relative refractive index difference delta 4 of the third cladding layer is-0.60-0.00%, and the radius R4 is 10.0-20.0 mu m; the outer cladding layer is used for cladding the third cladding layer and is a pure silica glass layer. The cut-off wavelength of the optical fiber cable is less than 1260nm, the integral dispersion at the waveband of 1260 nm-1460 nm is lower, and the attenuation performance is good. Especially suitable for 1260 nm-1460 nm wave band WDM transmission system.)

1. A low dispersion single mode fiber comprises a core layer and a cladding, and is characterized in that the relative refractive index difference delta 1 of the core layer is 0.30-0.65%, the radius R1 is 2.5-4.5 μm, the cladding is divided into three cladding layers and one cladding layer from inside to outside, the cladding core layer is a first cladding layer, the relative refractive index difference delta 2 of the first cladding layer is-0.70% -0.30%, the radius R2 is 4.5-7.0 μm, a second cladding layer covers the first cladding layer, the relative refractive index difference delta 3 of the second cladding layer is-0.20-0.25%, the radius R3 is 7.0-12.0 μm, a third cladding layer covers the second cladding layer, the relative refractive index difference delta 4 of the third cladding layer is-0.60-0.00%, and the radius R4 is 10.0-20.0 μm; and the outer cladding layer wraps the third cladding layer and is a pure silica glass layer.

2. The low dispersion, single mode optical fiber of claim 1 wherein said core is provided with a depressed center inner core, said inner core having a relative refractive index difference Δ 0 of from 0.10% to 0.55% and a radius R0 of from 1.0 μm to 2.5 μm.

3. The low dispersion, single mode optical fiber of claim 1 or 2, wherein said fiber has a cable cutoff less than 1260 nm.

4. The low dispersion, single mode optical fiber of claim 1 or 2, wherein said fiber has a dispersion coefficient of 0.0ps/nm/km to-18 ps/nm/km at a wavelength of 1260 nm.

5. A low dispersion, single mode optical fiber according to claim 1 or 2, wherein said fiber has an abbe number less than or equal to 3.5ps/nm/km at a wavelength of 1380 nm.

6. The low dispersion, single mode optical fiber of claim 1 or 2, wherein said fiber has a Abbe number of less than or equal to 10.0ps/nm/km at a wavelength of 1460 nm.

7. The low dispersion single mode fiber of claim 1 or 2, wherein said fiber exhibits an attenuation of less than or equal to 0.80dB/km in the 1260nm to 1460nm band.

8. A low dispersion, single mode optical fiber according to claim 1 or 2, wherein said fiber is bent 100 turns at a diameter of 60mm and has a bending loss at 1625nm of less than 0.1 dB.

9. The low dispersion, single mode optical fiber of claim 1 or 2, wherein said fiber is bent 10 turns at a diameter of 30mm, and the bending loss at a wavelength of 1550nm and 1625nm is less than 0.25dB and 1dB, respectively, and said fiber is bent 1 turn at a diameter of 20mm, and the bending loss at a wavelength of 1550nm and 1625nm is less than 0.75dB and 1.5dB, respectively.

10. Use of an optical fiber according to any of claims 1-9 as a low dispersion single mode fiber in a communication system, characterized in that said fiber is used in a 1260nm to 1460nm wavelength WDM transmission system.

Technical Field

The present invention relates to a single mode fiber for use in fiber optic communication systems, and more particularly to a dispersion adjusted low dispersion single mode fiber. The single mode fiber has lower dispersion in a larger wavelength range, can solve the problem of system transmission performance caused by dispersion, and is particularly suitable for 1260 nm-1460 nm wave band WDM transmission systems.

Background

In an optical fiber communication system, accumulation of chromatic dispersion existing in a single-mode optical fiber in a transmission process can deform signal pulses, so that chromatic dispersion cost is increased, and an error rate is increased. Also, dispersion is a factor limiting the transmission distance. In order to correct the influence of Dispersion on transmission performance, when conventional optical fiber is used for transmission, a Post-Dispersion Compensation (PDC) module can be placed at a receiving end to restore a waveform. However, the addition of the dispersion compensation module increases the complexity of the system, requires a special placement space, and increases the workload of laying and maintenance. In order to reduce the influence of dispersion on the transmission performance, simplify the dispersion compensation design of a system, reduce the overall cost of the system, prolong the transmission distance of the system, and develop a novel dispersion optimized single-mode optical fiber with smaller dispersion value in a wide band range. At present, most of the commercially available patents of the dispersion shifted single mode fiber, the non-zero dispersion shifted single mode fiber and the existing dispersion flat fiber focus on the dispersion optimization of 1530nm to 1565nm, and do not focus on the 1260nm to 1460nm wave band.

Chinese patent CN200610117423.7 describes a full-wave non-zero dispersion flat single-mode optical fiber, which is composed of a central core layer, two annular cladding layers, and an outer cladding layer. Although the optical fiber gives a dispersion value in a 1300 nm-1625 nm wave band range, no cutoff wavelength value is mentioned, the difference between the refractive index of the core layer and the first annular layered layer and the core diameter are large, the cutoff wavelength of the optical fiber is expected to be high, and high-order modes exist in the 1300 nm-1625 nm wave band range of the whole wave band of the optical fiber through calculation, so that the optical fiber cannot be applied to a single-mode optical fiber transmission system. The patent only gives the dispersion and effective area parameters and does not give the attenuation characteristics of the fiber. Meanwhile, the refractive index difference of the second annular layered layer of the optical fiber is high, and the outer layer of the annular layered layer is not provided with a sunken layered layer, so that the effective area and the bending performance are difficult to balance, and the bending performance is reduced while the effective area is increased.

Chinese patent CN1664635A describes a positive dispersion flat single mode fiber, a triple-clad fiber with alpha distribution, the structural parameters of the fiber can achieve the dispersion flat in the 1460 nm-1625 nm band, but the patent does not mention the characteristic parameters of the fiber in the 1260 nm-1460 nm band, nor gives the attenuation characteristic of the fiber. The upper limit of the cut-off wavelength is higher in the embodiment, and the single-mode transmission of the optical fiber in the 1260 nm-1460 nm full wave band can not be ensured. Chinese patent CN100510811C describes a low-zero-dispersion non-zero-dispersion shifted fiber, which also has an alpha-distributed optical fiber with a triple-clad structure, in which the relative refractive index of the first annular region is greater than equal zero, which results in a smaller refractive index difference of the core cladding, and the outer layer of the annular cladding is not provided with a depressed cladding to limit the leakage of the optical fiber signal. The patent optimizes the dispersion of 1525 nm-1625 nm band, and the absolute value of the dispersion of 1310nm band is very large.

In summary, most dispersion optimized fibers currently have cable cutoff wavelengths greater than 1260nm, and transmission and dispersion optimization in the C + L (1530nm to 1625nm) band is of primary concern, so only the fiber characteristics in this band are given, and the O + E (1260nm to 1460nm) band is of no concern. The common single-mode G.652.D optical fiber has larger dispersion slope in the 1260 nm-1460 nm wave band and larger dispersion of long wavelength, so that the sensitivity of the system is poor, the dispersion power cost is higher, and the longer the transmission distance is, the more serious the influence on the system is. The method has great significance for improving the transmission performance of the single-mode optical fiber in a 1260 nm-1460 nm waveband WDM system, reducing the dispersion power cost and the overall cost of the system and developing a novel dispersion optimized single-mode optical fiber. The dispersion of a single-mode fiber is composed of material dispersion and waveguide dispersion, the material dispersion is caused by nonlinear change of refractive index with wavelength, and is only related to the composition of the material, and the addition of some doping impurities can be slightly modified, but the adjustable range of the material dispersion is smaller as long as silica is used as the raw material of the fiber. The waveguide dispersion is an important component of the optical fiber dispersion, depends on a waveguide structure, and can be adjusted through reasonable design of a refraction rate profile, so that the total optical fiber dispersion can be flexibly adjusted to meet the requirements of practical application.

Disclosure of Invention

For convenience of introduction to the present disclosure, some terms are defined:

performing: the glass rod or the combined body of the designed optical fiber can be directly drawn according to the design requirement of the optical fiber by the radial refractive index distribution consisting of the core layer and the cladding;

core rod: a solid glass preform comprising a core layer and a partial cladding layer;

diameter: the distance between the outer boundary of the layer and the center point;

refractive index profile: the relationship between the refractive index of the glass of an optical fiber or an optical fiber preform (including a core rod) and the diameter thereof;

relative refractive index difference Δ:

ni corresponds to the refractive index of the respective part of the fiber, n₀Is the refractive index of the outer cladding pure silica glass;

OVD deposition process: preparation of SiO with desired thickness by external vapor deposition₂Glass;

VAD deposition process: preparation of SiO with desired thickness by axial vapor deposition₂Glass;

APCVD deposition process: by means of high-frequency plasmaThe flame shrinks natural or synthetic quartz powder into SiO with required thickness₂Glass;

the PCVD deposition process comprises the following steps: preparing SiO with required thickness by microwave plasma chemical vapor deposition process₂Glass;

MPCVD deposition process: preparation of SiO with required thickness by improved plasma chemical vapor deposition process₂Glass;

total dispersion of single mode fiber: the algebraic sum of the material dispersion and the waveguide dispersion of the fiber; the intermodal dispersion of the single-mode optical fiber is zero; material dispersion is only related to the material composition, while waveguide dispersion depends on the core radius, refractive index difference, and shape of the refractive index profile;

the macrobend additional loss test method refers to the method specified in IEC 60793-1-47.

The technical problem to be solved by the present invention is to provide a low dispersion single mode fiber for overcoming the defects of the prior art, wherein the cut-off wavelength of the fiber optic cable is less than 1260nm, the integral dispersion at the 1260 nm-1460 nm band is low, and the attenuation performance is good.

The technical scheme adopted by the invention for solving the problems is as follows: the fiber comprises a fiber core layer and a cladding layer, and is characterized in that the relative refractive index difference delta 1 of the core layer is 0.30-0.65%, the radius R1 is 2.5-4.5 μm, the cladding layer is divided into three cladding layers and one cladding layer from inside to outside, the cladding core layer is a first cladding layer, the relative refractive index difference delta 2 of the first cladding layer is-0.70% -0.30%, the radius R2 is 4.5-7.0 μm, the second cladding layer covers the first cladding layer, the relative refractive index difference delta 3 of the second cladding layer is-0.20-0.25%, the radius R3 is 7.0-12.0 μm, the third cladding layer covers the second cladding layer, the relative refractive index difference delta 4 of the third cladding layer is-0.60-0.00%, and the radius R4 is 10.0-20.0 μm; and the outer cladding layer wraps the third cladding layer and is a pure silica glass layer.

According to the scheme, the core layer is provided with the inner core layer with the concave middle part, the relative refractive index difference delta 0 of the inner core layer is 0.10% -0.55%, and the radius R0 is 1.0-2.5 microns.

According to the scheme, the optical fiber has the cable cut-off wavelength smaller than 1260 nm.

According to the scheme, the dispersion coefficient of the optical fiber at the wavelength of 1260nm is 0.0ps/nm/km to-18 ps/nm/km.

According to the scheme, the dispersion coefficient of the optical fiber at the wavelength of 1380nm is less than or equal to 3.5 ps/nm/km.

According to the scheme, the dispersion coefficient of the optical fiber at the wavelength of 1460nm is less than or equal to 10.0 ps/nm/km.

According to the scheme, the attenuation of the optical fiber in a 1260 nm-1460 nm wave band is less than or equal to 0.80dB/km, and preferably, the attenuation of the optical fiber is less than or equal to 0.60 dB/km.

According to the scheme, the optical fiber is bent for 100 circles under the diameter of 60mm, and the bending loss of the optical fiber at the wavelength of 1625nm is less than 0.1 dB; preferably, the optical fiber is bent for 10 circles under the diameter of 30mm, the bending loss of the optical fiber under the wavelength of 1550nm and 1625nm is respectively less than 0.25dB and 1dB, the optical fiber is bent for 1 circle under the diameter of 20mm, and the bending loss of the optical fiber under the wavelength of 1550nm and 1625nm is respectively less than 0.75dB and 1.5 dB.

According to the scheme, the optical fiber is applied to a communication system as a low-dispersion single-mode optical fiber, and is characterized in that the optical fiber is used for a 1260 nm-1460 nm waveband WDM transmission system.

The invention has the beneficial effects that: 1) by adjusting the refractive index profile of the optical fiber, the low first cladding layered refractive index, the reasonable first cladding layered radius and the reasonable second cladding layered refractive index are set, so that the waveguide dispersion value of the optical fiber is reduced, the total dispersion (the sum of waveband dispersion and material dispersion) of the optical fiber is reduced, and particularly, a single-mode optical fiber with low 1260 nm-1460 nm waveband dispersion is obtained, the dispersion coefficient is lower than that of the conventional G.652.D, but is higher than that of a non-zero dispersion displacement single-mode optical fiber, the dispersion power compensation cost can be obviously reduced, the requirement on the optical module is reduced, the overall cost of the system is saved, and the transmission application requirement of the system with high performance and low cost is met; 2) through reasonable arrangement of the refractive index and radius of the core layer and the refractive index of the second cladding layer, the cut-off wavelength of the optical fiber is smaller than 1260nm, the integral attenuation of the optical fiber in a 1260 nm-1460 nm wave band is good, and the transmission requirement of a long-distance system can be met; 3) the sunken cladding structure is arranged in the outer cladding, so that the leakage of optical signals in a bending state can be limited, the bending loss is reduced, and the reliability of the optical fiber under the complex use condition is improved; 4) the design of the section of the three-cladding layered refractive index of the optical fiber meets various performances, so that the manufacturing process is simple, the manufacturing cost of the optical fiber is low, and the optical fiber can be produced and applied in a large scale.

Drawings

FIG. 1 is a schematic cross-sectional view of the refractive index of a first embodiment of an optical fiber of the present invention;

FIG. 2 is a schematic representation of a refractive index profile of a second embodiment of an optical fiber of the present invention;

FIG. 3 is a graph showing the dispersion curve of the fiber of the present invention in the 1260 nm-1460 nm band, compared with a conventional G.652.D fiber and a non-zero dispersion shifted single mode fiber.

Detailed Description

The present invention will be further supplemented and explained with reference to the following detailed examples.

In a first embodiment of the present invention, as shown in fig. 1, an optical fiber includes a core layer and a cladding layer, wherein the core layer has a relative refractive index difference Δ 1 and a radius R1, the cladding layer is divided into three cladding layers and an outer cladding layer from inside to outside, the core layer is a first cladding layer, the first cladding layer has a relative refractive index difference Δ 2 and a radius R2, the second cladding layer covers the first cladding layer, the second cladding layer has a relative refractive index difference Δ 3 and a radius R3, the third cladding layer covers the second cladding layer, the third cladding layer has a relative refractive index difference Δ 4 and a radius R4; and the outer cladding layer wraps the third cladding layer and is a pure silica glass layer.

The design parameters of the refractive index profile structure of the optical fiber are given in table 1, and the optical fiber performance achieved under the structural parameters are given in table 2.

TABLE 1

TABLE 2

A second embodiment of the invention is shown in figure 2 and differs from the first embodiment in that the core is provided with a depressed central inner core layer having a relative refractive index difference Δ 0 and a radius R0. The other structure is the same as that of the first embodiment. By arranging a structure of an intermediate depressed layer in the core layer of the optical fiber, the internal energy distribution of the optical fiber is changed from a typical Gaussian distribution to a non-Gaussian distribution, and the mode field diameter of the optical fiber can be increased properly under the condition of ensuring that the cut-off wavelength is less than 1260 nm.

The design parameters of the refractive index profile structure of the optical fiber are given in table 3, and the optical fiber performance achieved under the structure parameters are given in table 4.

TABLE 3

Index (I)	Example 1	Example 2	Example 3	Example 4	Example 5
						Depressed core layer delamination radius R0/um	1.0	1.5	2.5	1.0	1.1
Depressed core layer relative refractive index Δ 0	0.55％	0.35％	0.20％	0.15％	0.10％
						Outer core layer lamination radius R1/um	2.7	3.3	4.5	3.0	3.1
Relative refractive index of outer core layer delamination Δ 1	0.65％	0.45％	0.30％	0.52％	0.54％
						First cladding layer radius R2/um	4.7	5.5	7.0	6.0	5.6
Relative refractive index of the first cladding layer Delta 2	-0.60％	-0.70％	-0.30％	-0.55％	-0.42％
						The lamination radius of the second cladding layer is R3/um	7.0	12.0	9.0	10.5	10.0
Relative refractive index of the second cladding layer Delta 3	-0.20％	0.00％	0.25％	0.08％	0.14％
						Third cladding layer radius R4/um	10.0	20.0	18.0	12.5	14.0
Relative refractive index delta 4 of third cladding layer	-0.40％	-0.60％	0	-0.10％	-0.10％

TABLE 4