CN106772788B - A cut-off wavelength shifted single-mode fiber - Google Patents

Abstract

The invention provides a cut-off wavelength shifted single-mode optical fiber, which comprises a core layer, an inner cladding layer coated sequentially, a depressed cladding layer, a middle cladding layer and an outer cladding layer. The radius R ₁ of the core layer ranges from 5.5 to 8.5 μm, and the refractive index difference Δn ₁ of the core layer relative to the outer cladding layer ranges from 0.1% to 0.3%; the thickness of the inner cladding layer R ₂ - The range of R ₁ is 5-25 μm, the range of the refractive index difference Δn ₂ of the inner cladding relative to the outer cladding is -0.2%-0%; the range of the thickness R ₃ -R ₂ of the depressed cladding is 4.5 to 12 μm, the range of the refractive index difference Δn ₃ of the depressed cladding relative to the outer cladding is -0.45% to -0.25%; the range of the thickness R ₄ -R ₃ of the middle cladding is greater than 10 μm, so The refractive index difference Δn ₄ of the middle cladding layer relative to the outer cladding layer ranges from Δn ₂ to 0%; the radius R ₅ of the outer cladding layer ranges from 60 μm to 65 μm. The optical fiber provided by the invention not only has excellent properties such as low attenuation, large effective area and low bending loss, but also can realize the controllability of the cut-off wavelength of the optical fiber.

Description

A cut-off wavelength shifted single-mode fiber

technical field

The invention relates to the field of optical communication, in particular to a cut-off wavelength shifted single-mode optical fiber.

Background technique

Optical fiber is the basic transmission physical medium of the optical communication network, and the improvement of its transmission system performance can be directly reflected in the improvement of the optical signal-to-noise ratio (OSNR). The loss and nonlinear effects of optical fibers are the key factors that limit the OSNR of high-speed and large-capacity optical fiber communication systems. It has been proved by relevant research that increasing the effective area (A _eff ) of the optical fiber can not only increase the optical power entering the fiber, but also effectively reduce the nonlinear effect. Therefore, increasing the effective area of the fiber and reducing the fiber loss are the main ways to overcome the two restrictive factors of fiber loss and nonlinear effects.

At present, the most commonly used single-mode fiber G.652 in optical communication has a typical attenuation value of 0.19dB/km at a wavelength of 1550nm, and the upper limit of the cut-off wavelength is 1260nm. Limited by the cut-off wavelength, the typical effective area is 83μm ² . The upper limit of the cut-off wavelength of the cut-off wavelength-shifted single-mode fiber (G.654) is 1530 nm, and its effective area is usually larger than 100 μm ² .

For the effective area A _eff of the fiber, the relationship between it and the mode field diameter MFD is shown in formula (1),

In the formula, k is the correction coefficient.

It can be seen from formula (1) that the effective area A _eff of the fiber is proportional to the square of the MFD, so a large effective area means a large mode field diameter. Generally, the mode field diameter can be increased by increasing the outer diameter of the core layer of the fiber or reducing the refractive index difference between the core layer and the inner cladding layer of the fiber.

The main component of communication optical fiber is silica. In the manufacturing process of optical fiber preform, the refractive index of the core layer is generally increased by doping germanium dioxide, and the refractive index of the cladding layer is reduced by doping fluorine. Among them, when the optical fiber has a graded refractive index, the refractive index change can be Expressed by the distribution function n(ρ) of the refractive index along the radius,

In the formula: n ₁ is the refractive index of the axis of the core layer 11, n ₂ is the refractive index of the outer and inner cladding 13 of the core layer 11, α is the refractive index coefficient, and R1 is the radius of the core layer 11. After 40 years of hard work, the manufacturing process of preforms and optical fibers has reached the extreme. In addition to the intrinsic absorption of silicon dioxide, the absorption and scattering of doped germanium dioxide are the main sources of attenuation of communication optical fibers, so reducing the content of germanium dioxide in the core layer is the main direction to reduce the attenuation of optical fibers. In the existing typical G.654 single-mode fiber design, although the refractive index and germanium dioxide content of the core layer are significantly lower than the typical G.652 fiber, the mode field diameter, cut-off wavelength λ _cc and bending loss limit the core Layer germanium dioxide doping amount further decreased.

Contents of the invention

In view of this, it is necessary to provide an optical fiber, which can further reduce the loss of the optical fiber through a reasonable optical fiber structure design, and at the same time meet the requirements of G.654 on parameters such as mode field diameter, cut-off wavelength, and bending loss.

The present invention provides a cut-off wavelength shifted single-mode optical fiber, which includes a core layer with a graded refractive index, an inner cladding layer with a step refractive index, a depressed cladding layer, a middle cladding layer and an outer cladding layer coated sequentially, wherein:

The radius of the core layer is R ₁ , the range of R ₁ is 5.5-8.5 μm, the refractive index of the core layer axis is n ₁ , and the refractive index difference between the core layer axis and the outer cladding is Δ n ₁ , the range of △n ₁ is 0.1%～0.3%;

The radius of the inner cladding is R ₂ , the thickness of the inner cladding is R ₂ -R ₁ , the range of R ₂ -R ₁ is 5-25 μm, the refractive index of the inner cladding is n ₂ , the inner cladding The refractive index difference relative to the outer cladding is Δn ₂ , and the range of Δn ₂ is -0.2% to 0%;

The radius of the depressed cladding is R ₃ , the thickness of the depressed cladding is R ₃ -R ₂ , the range of R ₃ -R ₂ is 4.5-12 μm, and the refractive index of the depressed cladding is n ₃ , so The refractive index difference between the depressed cladding layer and the outer cladding layer is Δn ₃ , and the range of Δn ₃ is -0.45%～-0.25%;

The radius of the middle cladding layer is R ₄ , the thickness of the middle cladding layer is R ₄ -R ₃ , the range of R ₄ -R ₃ is greater than 10 μm, the refractive index of the middle cladding layer is n ₄ , and the The refractive index difference between the middle cladding layer and the outer cladding layer is Δn ₄ , and the range of Δn ₄ is Δn ₂ to 0%;

The radius of the outer cladding is R ₅ , the range of R ₅ is 60-65 μm, and the refractive index of the outer cladding is n _c .

Further, a typical value of the radius R ₅ of the outer cladding is 62.5 μm.

Further, the effective area of the optical fiber at a wavelength of 1550nm is 100-170μm ² ; the dispersion at a wavelength of 1550nm is greater than 18ps/nm/km; the attenuation coefficient at a wavelength of 1550nm is lower than 0.18dB/km; The cut-off wavelength of the optical cable is less than 1530nm.

Further, when the effective area of the optical fiber is ^100-145 μm2, at a wavelength of 1550 nm, the macrobending loss of 30 mm radius-100 turns is less than 0.05 dB, and at a wavelength of 1625 nm, the macrobending loss of 30 mm radius-100 turns is less than 0.1 dB.

Further, when the effective area of the optical fiber is ^145-170 μm2, at a wavelength of 1550 nm, the macrobending loss of 30 mm radius-100 turns is less than 0.15 dB, and at a wavelength of 1625 nm, the macrobending loss of 30 mm radius-100 turns is less than 0.3 dB.

Further, the applicable wavelength range of the optical fiber is 1535-1625 nm.

Further, the optical fiber is a low-loss single-mode optical fiber with shifted cut-off wavelength.

The optical fiber designed by the optical fiber structure provided by the present invention can not only meet the parameters requirements such as the mode field diameter of the G.654 optical fiber, the cut-off wavelength λ _cc of the optical cable and the bending loss, but also has the characteristics of low attenuation, large effective area and low bending loss; At the same time, the controllability of the cut-off wavelength of the fiber can be realized by adjusting the refractive index of the fiber structure (middle cladding layer).

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 shows a schematic cross-sectional view of an optical fiber according to an embodiment of the present invention;

Figure 2 shows a schematic diagram of the structural design of the optical fiber shown in Figure 1;

Fig. 3 shows the refractive index profile of example 1 optical fiber;

Fig. 4 shows the refractive index profile of example 2 optical fiber;

Fig. 5 shows the refractive index profile of example 3 optical fiber;

Fig. 6 shows the refractive index profile of example 4 optical fiber;

Fig. 7 shows the refractive index profile of example 5 optical fiber;

Fig. 8 shows the refractive index profile of example 6 optical fiber;

Fig. 9 shows the refractive index profile of example 7 optical fiber;

Fig. 10 shows the refractive index profile of the fiber of Example 8.

Explanation of main component symbols

optical fiber 10 core layer 11 Inner cladding 13 Depressed cladding 15 Middle cladding 17 Outer cladding 19

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. It can be understood that the drawings are provided for reference and illustration only, and are not intended to limit the present invention. The connection shown in the drawings is only for the convenience of clear description, and does not limit the connection method.

It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or intervening elements may also exist. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

Referring to FIG. 1 and FIG. 2 , this embodiment provides an optical fiber 10 capable of achieving low loss and large effective area. In this embodiment, the optical fiber 10 is a G.654 single-mode optical fiber, and its parameters such as mode field diameter, optical cable cut-off wavelength λ _cc and bending loss conform to the parameter standards of the G.654 optical fiber. The optical fiber 10 includes a core 11 at the center, an inner cladding 13 coated on the outer surface of the core 11, a depressed cladding 15 coated on the outer surface of the inner cladding 13, and a depressed cladding 15 coated on the outer surface of the depressed cladding 15. The middle cladding layer 17 and the outer cladding layer 19 coated on the outer surface of the middle cladding layer 17. As shown in FIG. 1 , the schematic cross-sections of the core layer 11 , the inner cladding layer 13 , the depressed cladding layer 15 , the middle cladding layer 17 and the outer cladding layer 19 are five concentric circles. In this embodiment, the addition of the depressed cladding 15 is beneficial to the optimization of the bending loss of the single-mode optical fiber 10; the outer cladding 19 is generally made of pure silica. In other embodiments of the present invention, the outer cladding layer 19 may also be silicon dioxide lightly doped with other additional materials, such as silicon dioxide lightly doped with fluorine.

The core layer 11 has a radius R ₁ and has a graded refractive index. In addition, the refractive index difference between the axis of the core layer 11 and the outer cladding layer 19 is Δn ₁ , wherein R ₁ ranges from 5.5 to 8.5 μm, and Δn ₁ ranges from 0.1% to 0.3%. The change of the refractive index difference between the core layer 11 and the outer cladding layer 19 can be realized by doping the core layer 11 with germanium dioxide.

The radius of the inner cladding 13 is R ₂ , the refractive index of the inner cladding 13 is n ₂ , and the refractive index difference between the inner cladding 13 and the outer cladding 19 is Δn ₂ , wherein the thickness of the inner cladding 13 is R ₂ −R ₁ The range is 5 to 25 μm, and the range of Δn ₂ is -0.2% to 0%.

The radius of the depressed cladding 15 is R ₃ , the refractive index of the depressed cladding 15 is n ₃ , and the refractive index difference between the depressed cladding 15 and the outer cladding 19 is Δn ₃ , wherein the thickness of the depressed cladding 15 is R ₃ -R ₂ ranges from 4.5 to 12 μm, and Δn ₃ ranges from -0.45% to -0.25%.

The radius of the middle cladding layer 17 is R ₄ , the refractive index of the middle cladding layer 17 is n ₄ , and the refractive index difference between the middle cladding layer 17 and the outer cladding layer 19 is Δn ₄ , wherein the thickness of the middle cladding layer 17 is R ₄ The range of -R ₃ is greater than 10 μm, and the range of Δn ₄ is Δn ₂ to 0%.

The radius of the outer cladding 19 is R ₅ , the refractive index of the outer cladding 19 is n ₅ , and the thickness of the outer cladding 19 is R ₅ -R ₄ , wherein the range of R ₅ is 60-65 μm, and its typical value is 62.5 μm, namely The radius range of the optical fiber 10 is 60-65 μm, and its typical value is 62.5 μm.

Table I below shows examples of structural designs for optical fibers 10 according to the present invention, as well as comparative examples of other designs outside the scope of the present invention. Wherein example 3, example 5, example 7 and example 8 are examples according to structural design of the present invention, and example 1, example 2, example 4 and example 6 are outside the scope of protection of the present invention and are the examples given for comparison .

Table I

Table II below shows the test values of the main properties of the examples and comparative examples shown in Table I. Before the test of the present invention, the optical fibers described in Examples 1 to 8 were all rewound on a disc with a diameter of 420mm under zero tension, and then the optical time domain reflectometer (PK8000-OTDR) was used to test the attenuation of the optical fiber at each wavelength , to eliminate the influence of macrobending on the attenuation test results.

Table II

Please refer to FIG. 3 to FIG. 10 , and analyze the differences and advantages of each example and comparative example in combination with Table I and Table II. Examples 1 to 5 (FIG. 3 to FIG. 7) are examples of optical fibers produced by axial vapor deposition (VAD), or a hybrid method of VAD and modified chemical vapor deposition (MCVD) fluorine-doped silica sleeve. Example 1 has a similar refractive index distribution to the common G.652 fiber ((Δn ₁ + |Δn ₂ |) about 0.35%), which is the simplest fiber design and the most commonly used G.654 fiber design. On the one hand, the effective area is increased by increasing the radius of the core layer 11; on the other hand, the effective area is increased by reducing the refractive index difference between the core layer 11 and the inner cladding layer 13 (Δn ₁ +|Δn ₂ |about 0.29%). Compared with the performance of the G.652 optical fiber, the optical fiber in Example 1 has a lower attenuation coefficient and a large mode field diameter, but due to the limitation of the cut-off wavelength and bending loss of the optical cable, the refractive index difference between the core layer 11 and the inner cladding layer 13 The optimization range and the increase in the effective area are very limited (the nominal value of the mode field diameter is usually less than 12.5μm). If the mode field diameter needs to be further increased, in addition to adjusting the refractive index difference between the core layer 11 and the inner cladding layer 13 and the core layer diameter, a concave structure is also used to control the bending loss of the optical fiber.

Example 2 and Example 1 have the same (Δn ₁ +|Δn ₂ |) (about 0.29%). In order to further reduce the fiber loss, in Example 2, n ₁ is reduced by reducing the doping amount of germanium dioxide in the core layer 11, and n ₂ is reduced at the same time in order to keep the mode field diameter unchanged. The test results show that the attenuation coefficient of the optical fiber in Example 2 is slightly lowered at 1550nm, but the cutoff wavelength of the optical cable is lower (1298nm). Although the thickness of the inner cladding layer 13 is large (about 22 μm), the bending loss is severely deteriorated (at 1550 nm and 1625 nm, the macrobending loss of 30 mm radius-100 turns is as high as 0.27 dB and 0.93 dB, respectively).

Example 3 adds depressed cladding 15 and middle cladding 17 on the basis of example 2, as can be seen from Table II, the bending loss of example 3 optical fiber is significantly reduced (at 1550nm and 1625nm, the macrobend of 30mm radius-100 turns The loss reaches 0.01dB and 0.02dB respectively), and the attenuation coefficient at 1550nm is low, and the cut-off wavelength of the optical cable is also significantly increased (1444nm).

Example 4 has the same n ₂ as Example 2 and Example 3. In order to increase the mode field diameter while further reducing the fiber attenuation, Example 4 has a very low Δn ₁ (0.12%), and its (Δn ₁ + |Δn ₂ |) is about 0.2%. This example adopts the traditional concave structure (i.e. concave cladding 15) to reduce the bending loss, but the data in Table II shows that the concave structure has limited improvement in bending loss for large circles (at 1550nm and 1625nm, the macro of 30mm radius-100 circles The bending losses are up to 0.20dB and 0.39dB respectively); at the same time, due to the reduction of Δn ₁ , the cut-off wavelength of the optical fiber in example 4 is too low (1021nm), and the cut-off wavelength of the optical cable is not easy to adjust and control.

In order to solve the deficiencies in Example 4, Example 5 added middle cladding 17 on the basis of Example 4, as can be seen from Table II, Example 5 can further reduce the bending loss of optical fiber on the basis of lower attenuation (at 1550nm and At 1625nm, the macrobending loss of 30mm radius-100 turns reaches 0.07dB and 0.16dB respectively), and the cut-off wavelength of the optical cable meets the G.654 standard.

Examples 6 to 8 (FIG. 8 to FIG. 10) are examples of making optical fibers by MCVD process and fluorine-doped silica sleeve or pure silica sleeve. Comparing the main performance test values and structural design parameters of the fiber of Example 6 to Example 8, under the premise of further reducing the refractive index n ₁ of the core layer 11 and reducing the attenuation of the fiber, the improvement of the bending loss by only using the depressed cladding 15 is very Limited, the bending loss of the optical fiber can be reduced to the required range only if the design of the middle cladding 17 is added. Example 7 The optical fiber attenuation coefficient at 1550nm is 0.176dB/km, the macrobending loss of 30mm radius-100 turns is 0.02dB; at 1625nm, the fiber attenuation coefficient is 0.192dB/km, the macrobending loss of 30mm radius-100 turns The loss is 0.04dB. Comparing Example 6 with Example 7 and Example 8, the cutoff wavelength λ _cc of the optical cable is changed from 1303nm to 1512nm and 1405nm, that is, the cutoff wavelength of the optical fiber can be changed and controlled by adjusting the refractive index n ₄ of the middle cladding.

The structure design of the core layer 11, the inner cladding layer 13, the depressed cladding layer 15, the middle cladding layer 17 and the outer cladding layer 19 of the optical fiber 10 provided by the present invention has the characteristics of low attenuation, large effective area and low bending loss. At the same time, the parameters of the core layer 11, the inner cladding layer 13, the depressed cladding layer 15, the middle cladding layer 17 and the outer cladding layer 19 can realize the following characteristics: the application wavelength range of the optical fiber 10 is 1535nm to 1625nm; the effective area is 100-170μm at a wavelength of 1550nm ² ; Dispersion greater than 18ps/nm/km at a wavelength of 1550nm; attenuation coefficient lower than 0.18dB/km at a wavelength of 1550nm. The cable cut-off wavelength of the optical fiber 10 is less than 1530nm.

When the effective area of the optical fiber 10 ranges from 100 to 145 μm ² , at a wavelength of 1550nm, the macrobending loss of 30mm radius-100 turns is less than 0.05dB, and at a wavelength of 1625nm, the macrobending loss of 30mm radius-100 turns is less than 0.1dB. When the effective area of the optical fiber 10 ranges from 145 to 170 μm ² , at a wavelength of 1550nm, the macrobending loss of 30mm radius-100 turns is less than 0.15dB, and at a wavelength of 1625nm, the macrobending loss of 30mm radius-100 turns is less than 0.3dB. The optical fiber 10 provided by the present invention fully complies with the requirements of the G.654 standard on mode field diameter, cable cut-off wavelength λ _cc and bending loss, further reduces attenuation and realizes low bending loss and large effective area, and at the same time, the single-mode fiber provided by the present invention The optical fiber 10 can change and control the cut-off wavelength of the optical fiber by adjusting the refractive index n ₄ of the middle cladding 17 .

The optical fiber core rod of the optical fiber 10 provided by the present invention is suitable for various methods such as axial vapor deposition (VAD), external chemical vapor deposition (OVD), plasma chemical vapor deposition (PCVD) and modified chemical vapor deposition (MCVD). A manufacturing process or a hybrid process. In this embodiment, the manufacturing process of the optical fiber core rod can adopt the in-tube deposition method, that is, silicon tetrachloride is used as the raw material of silicon dioxide, germanium tetrachloride is used as the raw material of germanium dioxide, silicon tetrafluoride, six Sulfur fluoride or hexafluoroethane is used as the fluorine-doped raw material, and the depressed cladding 15, the inner cladding 13 and the core layer 11 are sequentially deposited on the inner surface of the fluorine-doped quartz substrate tube, and then the deposited substrate tube is melted and shrunk at high temperature into The core rod, at this time, the fluorine-doped quartz substrate tube or part of the fluorine-doped quartz substrate tube forms the middle cladding layer 17 . If the thickness of the middle cladding layer 17 is less than the design value, it can be realized by adding a fluorine-doped sleeve to the optical fiber core rod. At this time, the optical fiber core rod and the fluorine-doped sleeve are integrated into one by the sleeve shrinkage method . The in-pipe deposition method is suitable for PCVD, MCVD or Furnace Chemical Vapor Deposition (FCVD) manufacturing processes.

In other embodiments of the present invention, other manufacturing processes can also be used to manufacture the optical fiber core rod, such as the hybrid method, that is, the inner core rod of the optical fiber core rod is manufactured by VAD or OVD method first, and the inner core rod includes The core layer 11 and the inner cladding layer 13; combined with PCVD, MCVD or FCVD method, silicon tetrachloride is used as the raw material of silicon dioxide, and silicon tetrafluoride, sulfur hexafluoride or hexafluoroethane are used as raw materials doped with fluorine. A depressed cladding 15 is deposited on the inner surface of the fluorine-doped quartz tube; the inner mandrel and the fluorine-doped quartz tube are synthesized into one body through sleeve melting and shrinkage, and at this time, the fluorine-doped quartz tube or part of the fluorine-doped quartz tube is formed The middle cladding layer 17, if the thickness of the middle cladding layer 17 is less than the design value, can be realized by adding a fluorine-doped sleeve outside the optical fiber core rod. Or other methods that can produce fluorine-doped high-purity quartz to prepare the depressed cladding 15 and the middle cladding 17, such as a fluorine-doped sleeve or utilize OVD powder deposition combined with fluorine-doped sintering to deposit the depressed cladding 15 and the middle cladding 17 outside the inner core rod Middle cladding 17 etc.

The optical fiber core rod of the single-mode optical fiber 10 prepared by the above method is measured and calculated to obtain the required diameter of the core rod and the thickness of the outer cladding 19, and the core rod of the target specification is obtained by extending and straightening through heat treatment, and then passed through the quartz glass The outer cladding layer 19 is formed by tube melting or external deposition and melting, and finally the optical fiber preform rod of the single-mode optical fiber 10 is formed through degassing and other processes. It can be understood that the designed values of Δn ₁ , Δn ₂ , Δn ₃ , Δn ₄ and α need to be accurately realized in the process of manufacturing the optical fiber core rod, so as to ensure that the mode field diameter of the single-mode optical fiber 10 , Cable cut-off wavelength λ _cc and bending loss meet the G.654 standard.

The single-mode optical fiber 10 provided by the present invention can not only meet the parameter requirements such as the mode field diameter of the G.654 optical fiber, the optical cable cut-off wavelength λ _cc and the bending loss, but also has the characteristics of low attenuation, large effective area and low bending loss; The adjustment of the refractive index of the fiber structure realizes the controllability of the cut-off wavelength of the fiber. The low-loss single-mode optical fiber 10 with cut-off wavelength displacement provided by the present invention can be applied to several high-speed long-distance optical transmission systems, including submarine optical fiber communications, such as communication systems between land and islands, islands and islands, and coastal cities; lines need to wear Pass through places with harsh geographical conditions such as deserts, lakes, swamps, forests, etc., and places with complex geographical environments or harsh climates; and dedicated communications along the high-voltage power system.

In the description and claims of this application, the word "comprises/comprises" and the words "has/comprises" and their variants are used to specify the presence of stated features, numerical steps or components, but do not exclude the presence or addition of one or more other features, values, steps, components or combinations thereof.

For clarity, certain features of inventions, which are described in separate embodiments, may be used in combination in a single embodiment. Furthermore, various features of the invention which are described in a single embodiment can also be used separately or in any suitable subcombination.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (6)

1. The utility model provides a cut-off wavelength displacement single mode fiber, its characterized in that, includes the core layer of graded index, the inner cladding of the step index of cladding in proper order, sunken cladding, well cladding and outer cladding, wherein:

The radius of the core layer is R₁，R₁In the range of 5.5 to 8.5 μm, the refractive index of the core layer axis is n₁The refractive index coefficient alpha is 4.4 or 30, and the refractive index difference of the core layer axis relative to the outer cladding layer is delta n₁，△n₁The range of (A) is 0.1% -0.3%;

The radius of the inner cladding is R₂The thickness of the inner cladding is R₂-R₁，R₂-R₁In the range of 5 to 25 μm, the refractive index of the inner cladding is n₂The refractive index difference of the inner cladding relative to the outer cladding is Deltan₂，△n₂The range of (A) is-0.2% -0%;

The radius of the concave cladding is R₃The thickness of the depressed cladding layer is R₃-R₂，R₃-R₂in the range of 4.5 to 12 μm, the refractive index of the depressed cladding being n₃The difference of the refractive index of the depressed cladding layer relative to the outer cladding layer is Deltan₃，△n₃The range of (a) is-0.45 to-0.25 percent;

The radius of the middle cladding is R₄The thickness of the middle cladding layer is R₄-R₃，R₄-R₃In the range of more than 10 μm, the refractive index of the intermediate cladding being n₄The refractive index difference of the middle cladding layer relative to the outer cladding layer is delta n₄，△n₄In the range of Δ n₂～0％；

the outer cladding has a radius R₅，R₅In the range of 60 to 65 μm, the refractive index of the outer cladding being n_c。

2. The cutoff wavelength shifted single mode optical fiber of claim 1 wherein one half of the outer cladding layerdiameter R₅A typical value of (2) is 62.5 μm.

3. The cut-off wavelength shifted single mode optical fiber according to claim 1, wherein the optical fiber has an effective area of 100 to 170 μm at a wavelength of 1550nm²(ii) a The dispersion at a wavelength of 1550nm is greater than 18 ps/nm/km; the attenuation coefficient under the wavelength of 1550nm is lower than 0.18 dB/km; the optical fiber has a cable cutoff wavelength less than 1530 nm.

4. The cut-off wavelength shifted single mode optical fiber according to claim 3, wherein the effective area of the optical fiber is 100 to 145 μm²And meanwhile, under the wavelength of 1550nm, the macrobend loss of 30mm radius-100 circles is less than 0.05dB, and under the wavelength of 1625nm, the macrobend loss of 30mm radius-100 circles is less than 0.1 dB.

5. The cut-off wavelength shifted single mode optical fiber according to claim 3, wherein the effective area of the optical fiber is 145 to 170 μm²and meanwhile, under the wavelength of 1550nm, the macrobend loss of 30mm radius-100 circles is less than 0.15dB, and under the wavelength of 1625nm, the macrobend loss of 30mm radius-100 circles is less than 0.3 dB.

6. The cut-off wavelength shifted single mode optical fiber according to claim 1, wherein the optical fiber has an application wavelength range of 1535 to 1625 nm.