CN1514262A

CN1514262A - Dispersion compensating transmission optical fiber matched with orthochromatic dispersion and ortho chromatic dispersion slope unimodel optical fiber and use

Info

Publication number: CN1514262A
Application number: CNA031283217A
Authority: CN
Inventors: 韩庆荣; 张树强; 罗杰
Original assignee: Yangtze Optical Fibre and Cable Co Ltd
Current assignee: Sichuan Lefei Photoelectric Technology Co ltd; Yangtze Optical Fibre and Cable Co Ltd
Priority date: 2003-07-15
Filing date: 2003-07-15
Publication date: 2004-07-21
Anticipated expiration: 2023-07-15
Also published as: CN1252498C

Abstract

The waveguide structure of single-mode optical fibre comprises layered fibre core and layered clad. The fibre core is set with two core layers in different refractive indexed and layered clad consists of five layered clads. The codeposition of fluorine and germanium is applied by utilizing PCVD process to replace independent deposition of fluorine or germanium in deposition process for fibre core and clad so optical, mechanical and environmental performance of optical fibre is very much improved. The single-mode optical fibre produced in the present invention can be used in transmission of DWDM system.

Description

Dispersion compensation transmission optical fiber matched with positive dispersion and positive dispersion slope single-mode optical fiber and use thereof

Technical Field

The invention relates to a negative dispersion single-mode optical waveguide fiber designed for a high-capacity and high-speed transmission system and application of the fiber, in particular to a single-mode fiber which has certain negative dispersion and negative dispersion slope at 1450-1675nm, has low attenuation, low Polarization Mode Dispersion (PMD), large effective area, low melting joint loss, excellent bending resistance and environmental property.

Background

With the development of erbium-doped fiber amplifiers and wavelength division multiplexing technology in the mid-90 s of the 20 th century, fiber communication has entered an unprecedented high-speed development stage. With the development of wavelength division multiplexing, it is found that the nonlinear effects between wavelengths, such as four-wave mixing, self-phase modulation, cross-phase modulation, etc., have an influence on the system, which limits the expansion of the system capacity, and in order to suppress the nonlinear influence in a Dense Wavelength Division Multiplexing (DWDM) system, a proper amount of dispersion value is required in the transmission band; meanwhile, when the transmission rate exceeds 2.5Gbit/s, and with the practical use of the optical fiber amplifier, dispersion-substituted attenuation becomes a major limiting factor for long-distance transmission, and it is desired that the cumulative dispersion over the entire optical fiber transmission channel be as small as possible. Thus, dispersion compensation is indispensable in DWDM systems over long distances, large capacities and high transmission rates, e.g., 10G/s, 40G/s. At present, the most widely used method is realized by adding a module composed of Dispersion Compensation Fiber (DCF) on the fiber link, for DCF, in order to obtain large negative dispersion, the refractive index of the fiber core is required to be very high and the geometric dimension is required to be very small, so that the germanium content in the core of DCF is relatively large, and the characteristics of DCF such as attenuation, PMD and nonlinear effect are relatively poor. Furthermore, another disadvantage of using the DCF method is that DCF increases the attenuation, system cost, PMD, and non-linear effects of the system without increasing the length of the system.

Patent CN1351267A/US 2002/0076186a1 discloses an optical fiber for compensating dispersion in-line in an optical fiber with positive dispersion, but its negative dispersion at 1550nm is only-12 ps/(nm.km) to-4 ps/(nm.km), which cannot fully compensate the commonly used G652 optical fiber (the dispersion at 1550nm is more than 16ps/(nm.km)), and in addition, the smaller absolute value of the dispersion makes it occupy a larger proportion of the link, and its smaller effective area and larger PMD tend to have adverse effects on transmission.

In the patent US 2002/0176678a1, a reverse dispersion optical fiber and a related link with good optical performance are described, but as a dispersion compensation optical fiber used in a cable, a cabling is required to be used in combination with a conventional positive dispersion single mode optical fiber, and thus, in addition to good optical characteristics, particularly, excellent environmental characteristics and good fusion performance are required, which are closely related to the material structure design of the optical fiber, and are not mentioned in the above patent.

Defining:

-refractive index difference Δ and refractive index contribution

Defined by the following equation, the relative refractive index difference Δ% [ (n)₁-n_c)/n_c]×100％

Wherein n is₁Is the core refractive index, n_cFor cladding index, it is referred to in this application as the reference index. For non-stepped (e.g., parabolic) structures, the maximum value of Δ% is characterized.

Refractive index contribution value: is represented by the formula, wherein n₁Is a silica glass containing a certain dopant, n_cIn order to undoped the refractive index of a pure silica glass, Δ% is referred to as the contribution of the dopant, F and GeO₂Respectively by Δ_F% and. DELTA._GeO2% of the total weight of the composition.

-refractive index profile

Refers to the relationship between the refractive index difference, Δ%, or refractive index, and its radius over a selected portion of the core.

Dispersion and Link Dispersion

The dispersion is defined as the algebraic sum of the optical fiber waveguide dispersion and the material dispersion, and in the field of optical fiber communication, the dispersion is called the dispersion of an optical fiber and has the unit of ps/nm/km;

the total dispersion of the link is the length weighted average of the dispersion of all the optical fibers in the link, and the dispersion and the length of the transmission optical fiber are respectively set as D_T、L_TThe dispersion and length of the dispersion compensating fiber are respectively D_C、L_CThen the link dispersion is: d ═ D (D)_T*L_T+D_C*L_C)/(L_T+L_C)。

——DCF

Is an abbreviation of Dispersion Compensation Fiber (Dispersion Compensation Fiber).

——DCTF

Is an abbreviation of Dispersion Compensation transmission fiber (Dispersion Compensation fiber), which plays a role of Dispersion Compensation in a transmission system and is a part of a transmission link, increasing the transmission length.

——RDS

Is an abbreviation for Relative Dispersion Slope (Relative Dispersion Slope), which in the present invention refers to the ratio of Dispersion Slope to Dispersion at 1550nm, i.e.:

RDS＝S₁₅₅₀/D₁₅₅₀RDS may be used to measure the ratio of the dispersion slope of a dispersion compensating fiber to a compensating transmission fiber.

——DSCR

Is an abbreviation for Dispersion Slope Compensation ratio (Dispersion Slope Compensation ratio), and is an index for measuring the Compensation ability of a Dispersion Compensation fiber for a given transmission fiber Slope, and is defined as follows:

DSCR＝(RDS_C/RDS_T)*100％

——DWDM

is an abbreviation for Dense wavelength division multiplexing (Dense wavelength division multiplexing).

Bending resistance of optical fibers

The bend resistance of an optical fiber refers to the additional attenuation under the specified test conditions. The standard test conditions included 100 turns on a 60mm diameter mandrel and 1 turn on a 32mm diameter mandrel. Additional attenuation in bending was measured under each test condition.

Loss of weld joint

Fusion splice loss is the average of the bi-directional OTDR test valueswhen two fibers are fused together. The fusion splice losses referred to herein all refer to the average of the two-way OTDR test values at 1550 nm.

Hydrogen loss of optical fiber

The hydrogen loss of the optical fiber is a phenomenon that attenuation increases at certain characteristic wavelengths due to the reaction of defects in the optical fiber with hydrogen when the optical fiber is in an environment containing hydrogen, and is an important index of the environmental characteristics of the optical fiber. The hydrogen loss test is to test the additional attenuation characteristics of the optical fiber product under a hydrogen atmosphere. The test method used in the present invention is to test the additional attenuation of the fiber at 1530nm, with reference to ANSI/TIA/EIA-492 CAAB-2000.

Disclosure of Invention

The invention aims to overcome the defects of DCF (direct current to fiber) and provide a dispersion compensation transmission single-mode fiber (DCTF) which is suitable for a high-speed and large-capacity transmission system and is used for compensating a positive dispersion transmission single-mode fiber in a line. In addition, the optical fiber emphasizes the design of the optical fiber waveguide structure, and strengthens the design of material composition and structure. For DCTF, through the optimization design of section refractive index and reasonable material composition and structure design, the optical fiber with low attenuation, low PMD and low nonlinear coefficient can be obtained, and the optical fiber is matched with a transmission optical fiber with positive dispersion and positive dispersion slope for use, so that the dispersion compensation effect can be achieved, and the transmission length of the system is increased.

For the waveguide structure design ofthe optical fiber, the technical scheme of the invention is as follows: designing a single mode waveguide structure having a segmented Core with two Core segments of different refractive index profiles and a segmented cladding comprising five cladding segments, said first Core segment Core1 of the Core having a refractive index difference Δ Core 1% in the range of 0.85% to 1.30% and a diameter Φ Core1 in the range of 3.2 μm to 4.2 μm; the second Core segment refractive index difference Δ Core 2% ranges from 0.50% to 1.30%, and the diameter Φ Core2 ranges from 3.5 μm to 5.8 μm; a first cladding layer Clad1 having a refractive index difference Δ Clad 1% in the range of-0.50% to-0.30% and a diameter Φ Clad1 in the range of 7.5 μm to 12.5 μm; the relative refractive index difference Δ Clad 2% of the second cladding layer segment Clad2 ranged from 0.15% to 0.35%, and the diameter Φ Clad2 ranged from 11.0 μm to 18.0 μm; the relative refractive index difference Δ Clad 3% of the third cladding layer Clad3 ranged from about-0.2% to 0%, and the diameter Φ Clad3 ranged from 18.0 μm to 25.0 μm; the fourth cladding layer and the fifth cladding layer are pure silica glass having a refractive index equal to the refractive index of pure silica glass.

The material composition and structure design of the optical fiber follow the concept of a functional gradient material, in order to realize the designed refractive index distribution, the core rod is made of doped quartz glass, the proper formula is set, the radial direction of the cross section of the core rod has continuous composition and structure gradient change, the property of the material is gradually changed, no obvious interface exists in the prefabricated rod, the viscosity of each layer is matched, and simultaneously, the thermal stress is relaxed, so that the optical fiber can not have residual thermal stress and generate broken bonds in the subsequent process of optical fiber manufacturing, the attenuation of the optical fiber is reduced, the characteristics of PMD, warpage, fusion welding and the like are optimized, and the hydrogen loss resistance of the optical fiber is improved. The structural design of the multiple core layers and the multiple cladding layers enables the material design and the design of the waveguide structure to be harmoniously unified. The composition of the material is shown in table 1.

TABLE 1

Position of	Core1	Core2	Clad1	Clad2	Clad3	Clad4	Clad5
Position of	Core1	Core2	Clad1	Clad2	Clad3	Clad4	Clad5	Composition of	SiO₂-GeO₂-F		SiO₂-F	SiO₂-GeO₂-F		SiO₂

In the material composition, Core1, 2 and Clad1-4 are obtained by a low-temperature plasma chemical vapor deposition method, namely a PCVD (plasma chemical vapor deposition) process, and a trace amount of Cl is introduced in the reaction process. The Cl content is related to the proportion of oxygen and silicon germanium materials, the temperature of the holding furnace and the high-frequency power; clad5 is prepared by OVD process, wherein trace Cl is adopted in the sintering process₂Etc. are introduced as dehydrating agents. Cl also reduces the viscosity of the silica glass, which in turn reduces the draw temperature, and is beneficial in reducing the attenuation of the fiber. This is described in detail in patent US005740297/CN1087432C and is not considered to be part of the present invention.

In terms of material composition, it is not a mere matter to choose a single one for obtaining the designed waveguide structureDoping of one, but fully utilizing the advantages of the PCVD process, and adopting the codeposition of fluorine and germanium. Introduction of GeO₂The introduction of fluorine for increasing the refractive index can reduce the water peak in addition to the refractive index, because the raw material introduced into the quartz tube is changed into plasma in which a hydrogen-containing substance (e.g., H) is introduced under the high frequency action₂O、CH₄、SiHCl₃Etc.) to become hydrogen ions as follows:

freon (e.g. C) in plasma atmosphere₂F₆) Hydrogen can be removed by the following reaction to reduce the water peak:

therefore, the germanium and fluorine doping can optimize the attenuation of the optical fiber. Secondly, because the germanium is doped to increase the thermal expansion coefficient of the glass, the co-deposition of fluorine and germanium is adopted to ensure that F and Ge are distributed in a gradient way on the section of the optical fiber, so that no obvious interface exists in the optical fiber, the thermal stress can not be remained in the optical fiber in the drawing process, the internal stress in the optical fiber is the inherent reason of generating PMD in the single-mode optical fiber, and the residual thermal stress in the optical fiber can also increase the light scattering, thereby increasing the attenuation of the optical fiber.

The viscosity of the layers is brought as close as possible, i.e. matched, to each other by adjusting the doping between the layers. This is also a feature of the present invention. For fluorine F and germanium dioxide GeO doping₂The viscosity versus temperature of the quartz glass of (1) is as follows:

logη＝K₀+K_FΔ_F+K_GeO2Δ_GeO2K₀＝log[η_SiO2(T)](1)

\log (η_{Si O_{2}}) = - 2.49 + \frac{15004}{(T - 253)}

in the formula (1), η represents the viscosity, Δ, of the doped silica glass_F、Δ_GeO2Respectively fluorine F and twoGermanium oxide GeO₂Relative difference of the resulting refractive index change, K_F、K_GeO2Positive and negative constants, respectively, T is temperature deg.C η_SiO2Is the viscosity of pure quartz glass.

It is known from equation (1) that fluorine and germanium both reduce the viscosity of silica glass, which, if a single doping is used, necessarily results in a large change, even a sudden change, in the refractive index of the optical fiber in the region where the change in refractive index of the optical fiber is large, and furthermore, due to the difference in material composition, the layers will have different physical properties, such as expansion coefficient, heat capacity and softening temperature of the glass, which in the subsequent drawing process will result in residual stress in the optical fiber due to the difference in heating and cooling rates, from the definition of viscosity it is not difficult to understand that the viscosity of the glass has a large influence on the drawing tension, in particular when the viscosity of the "layers" within the optical fiber is largely mismatched and mutually, glass defects will be generated during drawing, such as breaking bonds, which not only increases the attenuation of the optical fiber, but also worsens the environmental properties of the optical fiber, such as the viscosity of the optical fiber when the viscosity of the "layers" do not match "and, which in relation to each other" do not match "each other, when the optical fiber" does not match "the viscosity, which, is calculated as the absorption of the optical fiber, the graph shows that the absorption of the optical fiber is not only the hydrogen absorption of the optical fiber, but also shows that the optical fiber, the absorption of the optical fiber, is reduced from log 0.20 km, i.8, which is calculated as the absorption of the optical fiber, the absorption of the optical fiber, the optical loss, which is not only the optical loss, which is less than the optical loss, which is calculated from the absorption of the optical loss, which is less than the optical loss, which is greater than the absorption of the optical fiber, indicated by.

By adjusting fluorine F and germanium dioxide GeO doping₂The relative content of the optical fiber enables the viscosities of all layers to be matched with each other while the designed waveguide structure is obtained, reduces the drawing tension, and reduces the residual stress and broken bonds caused by the drawing process, thereby achieving the purpose of optimizing various properties of the optical fiber. In the center of the fiber, the refractive index is highest and therefore the germanium doping is greatest, and in order to reduce the water peak to optimize the attenuation, a certain amount of fluorine doping is required and thus the viscosity is low, and for this purpose, the viscosity of the fiber is gradually increased from the inside to the outside by adjusting the doping. In addition, the doping amount is properly increased, and the characteristic that fluorine is easy to diffuse is utilized, so that a more reasonable gradient is further formed in the fiber drawing process, and although the refractive index profile of the fiber is slightly changed, if the refractive index profile of each layered step function in the original design is changed into the angular smooth step function profile, the transmission characteristic of the fiber is notinfluenced.

Through viscosity matching, broken bonds generated in the drawing process can be reduced, so that the hydrogen loss resistance of the optical fiber is improved, the warping characteristic of the optical fiber can be optimized, the distortion of a waveguide in the welding process can be reduced, and the loss of a fusion splice of the optical fiber is reduced.

In the optical fiber, the Cl content is negligible, and when the F doping is determined, the corresponding GeO2 doping amount is determined while the waveguide structure is determined (Δ GeO 2% ═ Δ%>- Δ F%), and in the present invention, the F doping amount of the optical fiber is shown in table 2 (in terms of the contribution of F).

TABLE 2

Position of	Core1	Core2	Clad1	Clad2	Clad3	Clad4	Clad5
Position of	Core1	Core2	Clad1	Clad2	Clad3	Clad4	Clad5	Δ_F％	-0.05 ±0.01	-0.06 ±0.01	-0.40 ±0.10	-0.130 ±0.05	-0.135 ±0.05	0	0

According to the scheme, the optical fiber has the following transmission characteristics:

a dispersion at 1530nm to 1675nm of less than-20 ps/nm/km, preferably less than-30 ps/nm/km; the RDS of the optical fiber is 0.0030-0.0045/nm;

attenuation at 1550nm is less than 0.25dB/km, preferably less than 0.22 dB/km;

the cut-off wavelength in the optical cable is less than or equal to 1450nm, and the cut-off wavelength of the optical fiber is greater than or equal to 1200nm and less than or equal to 1700 nm;

the mode field diameter MFD is greater than or equal to 5.60 μm, and the effective area is not less than 22 μm²Preferably greater than or equal to 30 μm²；

PMD of the optical fiber is less than or equal to 0.08ps/km^1/2Preferably less than or equal to 0.05ps/km^1/2；

In the test of 100 turns of phi 60mm mandrel winding, the additional attenuation caused by bending is less than 0.05dB at 1550nm and 1625nm, and the test result of 1 turn of phi 32mm mandrel winding is less than 0.5 dB;

when the optical fiber is welded, the average welding head loss is less than 0.08 dB;

the hydrogen loss of the optical fiber is less than 0.01 dB/km.

Meanwhile, the invention also provides a dispersion management link section consisting of the dispersion compensation transmission fiber and the positive dispersion and positive dispersion slope single-mode fiber, which can be used for the transmission of a DWDM system.

The invention applies the low-temperature plasma chemical vapor deposition method, namely PCVD process, combines material composition and structural design, designs a section which can be stably produced and is easy to control, and the manufactured optical fiber has certain negative dispersion and negative dispersion slope at 1450-.

Drawings

FIG. 1 is a schematic graph of relative refractive index difference Δ% versus diameter, corresponding to example 1.

Fig. 2 is a schematic graph of another relative refractive index difference, Δ%, versus diameter, in accordance with the present invention, corresponding to example 2.

Fig. 3 is a graphical representation of hydrogen loss test results.

Fig. 4 is a graphical representation of hydrogen loss test results.

Fig. 5 is a schematic diagram of a dispersion management link segment.

Fig. 6 is a schematic diagram of a dispersion management link segment.

Fig. 7 shows the dispersion characteristics of examples 1, 2, 4 and 4.

FIG. 8 is a schematic diagram of a transition optical fiber preform fabrication.

FIG. 9 is a schematic view of the viscosity profile of a cross section of an optical fiber.

Detailed Description

According to the refractive index profiles of the waveguide shown in fig. 1 and 2, the refractive index values of the ith layer of the core layer are represented by Δ Corei (i ═ 1, 2) and the diameter of the ith layer of the core layer is represented by Φ Corei (i ═ 1, 2); Δ clai (i ═ 1, 2, 3, 4) represents the relative refractive index value of the ith cladding layer, and Φ clai (i ═ 1, 2, 3, 4, 5) represents the diameter of the ith cladding layer. Wherein the fourth and fifth cladding layers are pure silica glass layers.

Examples 1 to 2:

table 3 lists a set of refractive index profiles according to FIG. 1, and the main properties of the resulting fibers are shown in Table 5.

TABLE 3

	ΔCore1 ％	ΔCore2 ％	ΔClad1 ％	ΔClad2 ％	ΔClad3 ％	ΦCore1	ΦCore2	ΦClad1	ΦClad2	ΦClad3
	ΔCore1 ％	ΔCore2 ％	ΔClad1 ％	ΔClad2 ％	ΔClad3 ％	ΦCore1	ΦCore2	ΦClad1	ΦClad2	ΦClad3	1	1.25	0.60	-0.38	0.33	-0.020	3.85	4.60	10.5	16.6	22
2	0.84	0.58	-0.43	0.24	-0.015	3.42	3.86	8.76	12.81	19	1	1.25	0.60	-0.38	0.33	-0.020	3.85	4.60	10.5	16.6	22

Examples 3 to 4:

table 4 lists the second set of refractive index profiles in FIG. 2, and the fiber results are shown in Table 5.

TABLE 4

	ΔCore1 ％	ΔCore2 ％	ΔClad1 ％	ΔClad2 ％	ΔClad3 ％	Φ Core1	Φ Core2	Φ Clad1	Φ Clad2	Φ Clad3
	ΔCore1 ％	ΔCore2 ％	ΔClad1 ％	ΔClad2 ％	ΔClad3 ％	Φ Core1	Φ Core2	Φ Clad1	Φ Clad2	Φ Clad3	3	0.98	0.98	-0.36	0.30	-0.005	3.60	4.80	10.6	16.7	25
4	0.95	0.95	-0.36	0.29	-0.020	3.65	4.65	10.5	16.5	25	3	0.98	0.98	-0.36	0.30	-0.005	3.60	4.80	10.6	16.7	25

The main optical parameters of the 4 embodiments are shown in table 5, and the dispersion characteristics are shown in fig. 7.

TABLE 5

	Optical parameter of 1550nm					Cut-off wavelength (nm)	Macrobend Φ60mm	Macrobend Φ32mm
	Optical parameter of 1550nm								Dispersion (dispers) (ps/nm/km)	Slope of dispersion (ps/nm²/km)	RDS (1/nm)	MFD (μm)	Attenuation of (dB/km)
	1	-42.1	-0.1286	0.00305	5.67				Dispersion (dispers) (ps/nm/km)	Slope of dispersion (ps/nm²/km)	RDS (1/nm)	MFD (μm)	Attenuation of (dB/km)	0.247	1571	0.030dB	0.070dB
2	1	-42.1	-0.1286	0.00305	5.67	-28.7	-0.0861	0.00300	5.61	0.228	1465	0.032dB	0.025dB	0.247	1571	0.030dB	0.070dB
2	3	-21.0	-0.0913	0.00435	5.84	-28.7	-0.0861	0.00300	5.61	0.228	1465	0.032dB	0.025dB	0.232	1486	0.007dB	0.020dB
4	3	-21.0	-0.0913	0.00435	5.84	-31.3	-0.1112	0.00355	5.75	0.241	1532	0.019dB	0.023dB	0.232	1486	0.007dB	0.020dB

For the optical fibers of the above embodiments, the hydrogen loss of the measured optical fibers is less than 0.01dB/km after viscosity matching is ensured by adjusting doping. By analyzing the components of the cross section of the optical fiber, and combining the cross-sectional refractive index test and the calculation of the formula (1), the viscosity distribution trend on the cross section of the optical fiber is shown in fig. 9.

For the optical fiber of the embodiment, the optical fiber is welded by using the Ericsson FSU975, when the optical fiber is welded by itself, more than 100 welding heads are tested, and the results show that the energy consumption of the welding heads is controlled to be below 0.08 dB; when the fusion splicer is fused with a G.652 optical fiber, the loss of the fusion splicer is about 0.6dB, and is preferably less than 0.3 dB.

The doping amount, the self-fusion test result and the hydrogen loss test result more than 10 times for the optical fibers of the above examples are shown in table 6.

TABLE 6

	Contribution of F					Average itself Fusion loss (dB)	Loss of hydrogen (dB/km)
	Contribution of F							Core1	Core2	Clad1	Clad2	Clad3
	1	-0.050	-0.080	-0.34	-0.125			Core1	Core2	Clad1	Clad2	Clad3	-0.135	0.059	0.007
2	1	-0.050	-0.080	-0.34	-0.125	-0.065	-0.075	-0.43	-0.135	-0.140	0.065	0.005	-0.135	0.059	0.007
2	3	-0.055	-0.06→-0.20	-0.36	-0.130	-0.065	-0.075	-0.43	-0.135	-0.140	0.065	0.005	-0.135	0.045	0.003

4

-0.060

-0.07→-0.20

-0.36

-0.130

-0.135

0.048

0.001

In addition, the PCVD technological parameters are adjusted and HF acid corrosion is combined to prepare a G.652 core rod with the diameter of 20 +/-0.05 mm and the optical fiber core rod of the invention, the G.652 core rod and the optical fiber core rod are cut into small units with the length of 3-8cm, the cross section is polished, then the G.652 core rod and the optical fiber core rod are cleaned, dried, crossed and placed in a high-purity quartz glass tube with the inner diameter of 20.5 +/-0.1 mm and the wall thickness of 2.5mm, the bottom end is fixed and placed in a high-purity quartz glass²The optical fiber is drawn into an optical fiber in a drawing furnace as shown in fig. 8, the position of a joint is determined by OTDR, and the optical fiber containing the joint is screened out, so that the optical fiber is a transition optical fiber. The transition optical fiber obtained by this method has no fluctuation of the fiber diameter at the joint, and the average joint loss at 1550nm is less than 0.24dB, preferably less than or equal to 0.14 dB.

Meanwhile, the invention also provides a dispersion management link section consisting of the dispersion compensation transmission fiber and the positive dispersion and positive dispersion slope single-mode fiber, which can be used for the transmission of a DWDM system. The scheme comprises the following two steps:

the first scheme is as follows: without adopting the transition optical fiber or optical cable, due to the difference of mode field diameter MFD and refractive index distribution, when the optical fiber is respectively welded with the positive dispersion single-mode optical fiber, the loss of the welding head is large, such as the average loss of the welding head at 1550nm is as high as0.60dB when the optical fiber is welded with the conventional single-mode optical fiber G.652. Although the splice loss is high, it is acceptable because the splice occurs only twice within one amplifier pitch. As shown in fig. 5: line 1 is a positive dispersion and positive dispersion slope single mode fiber or cable, and line 2 is the dispersion compensating transmission single mode fiber or cable described above.

Scheme II: the use of transition optical fibres or cables has the advantage of greatly reducing splice losses. The preparation of the transition optical fiber is that the dispersion compensation single-mode optical fiber prefabricated rod unit and the positive dispersion single-mode optical fiber prefabricated rod unit with the same diameter are butted in a core-to-core mode, and then drawing is carried out, the optical fiber containing the joint is the transition optical fiber, and the transition optical fiber has the remarkable characteristic that the joint loss at the joint is reduced to be below 0.3dB, and the total welding loss can be reduced by 0.2dB compared with the scheme I by adding two welding joint losses of the optical fibers at two ends which are welded with each other; meanwhile, the tensile strength of the joint of the optical fiber is higher than that of the optical fiber which is welded by adopting a welding method, so that the transition optical fiber not only can be used as a bridge fiber during welding, but also can be cabled to form a part of a transmission link. As shown in fig. 6: the line 1 is a single mode fiber or optical cable with positive dispersion and dispersion slope, the line 2 is a transition fiber or optical cable, and the line 3 is the dispersion compensation transmission single mode fiber or optical cable.

The invention is not limited to the embodiment, and all the optical fibers with positive dispersion and positive dispersion slope can be used as the dispersion compensation transmission single-mode optical fiber and the dispersion management link formed by the optical fiber as long as the Dispersion Slope Compensation Ratio (DSCR) meets the requirements of system design.

Claims

1. A dispersion compensating transmission fiber, the waveguide structure of which has a layered core and a layered cladding, the core is provided with two core layers with different refractive index profiles, the layered cladding comprises five cladding layers, characterized in that the refractive index difference Delta Corel% of the first core layer Corel of the core is in the range of 0.85% to 1.30%, and the diameter phi Corel is in the range of 3.2 μm to 4.2 μm; the second Core segment refractive index difference Δ Core 2% ranges from 0.50% to 1.30%, and the diameter Φ Core2 ranges from 3.5 μm to 5.8 μm; a first cladding layer Clad1 having a refractive index difference Δ Clad 1% in the range of-0.50% to-0.30% and a diameter Φ Clad1 in the range of 7.5 μm to 12.5 μm; the relative refractive index difference Δ Clad 2% of the second cladding layer Clad2 ranges from 0.15% to 0.35%, and the diameter Φ Clad2 ranges from 11.0 μm to 18.0 μm; the relative refractive index difference Δ Clad 3% of the third cladding layer Clad3 ranged from-0.2% to 0%, and the diameter Φ Clad.3 ranged from 18.0 μm to 25.0 μm; the fourth cladding layer and the fifth cladding layer are pure silica glass having a refractive index equal to the refractive index of pure silica glass.

2. The dispersion compensating transmission fiber of claim 1 wherein said Core first Core segment Core1, second Core segment Core2, second cladding segment Clad2, and third cladding segment Clad3 comprise SiO2-GeO₂F, the composition of the first cladding layer Clad1 is SiO₂F, the composition of the fourth cladding layer Clad4 and the fifth cladding layer Clad5 is SiO₂。

3. The dispersion compensating transmission fiber of claim 2 wherein said Core first Core segment Core1 has a% Δ F of-0.05 ± 0.01, said Core second Core segment Core2 has a% Δ F of-0.06 ± 0.01, said first cladding segment Clad1 has a% Δ F of-0.40 ± 0.10, said second cladding segment Clad2 has a% Δ F of-0.130 ± 0.05, and said third cladding segment Clad3 has a% Δ F of-0.135 ± 0.05.

4. A dispersion compensating transmission fiber according to any one of claims 2 to 3, wherein the viscosity between the layers in the fiber is matched such that there is no abrupt change in viscosity over the cross-section of the fiber from the inside to the outside with a gradual increase in viscosity or as close as possible.

5. Dispersion compensating transmission fiber according to claim 4, characterized in that said fiber has a dispersion at 1530nm to 1675nm of less than-20 ps/nm/km, preferably less than-30 ps/nm/km; the RDS of the fiber is 0.0030-0.0045/nm; attenuation at 1550nm is less than 0.25dB/km, preferably less than 0.22 dB/km; the mode field diameter MFD is greater than or equal to 5.60 μm, and the effective area is not less than 22 μm²Preferably greater than or equal to 30 μm²(ii) a PMD of the optical fiber is less than or equal to 0.08ps/km^1/2Preferably less than or equal to 0.05ps/km^1/2(ii) a In the test of 100 turns of phi 60mm mandrel winding, the additional attenuation caused by bending is less than 0.05dB at 1550nm and 1625nm, and the test result of 1 turn of phi 32mm mandrel winding is less than 0.5 dB; the cut-off wavelength in the optical cable is less than or equal to 1450 nm; when the optical fiber is welded, the average welding head loss is less than 0.08dB; the hydrogen loss of the optical fiber is less than 0.01 dB/km.

6. Use of a dispersion compensating transmission fiber according to claim 5, wherein the dispersion compensating transmission fiber is used in a link with a fiber having a positive dispersion and a positive dispersion slope for transmission in a DWDM system.