阅读说明：本技术 一种色散优化弯曲不敏感光纤 (Dispersion optimization bending insensitive optical fiber ) 是由 雷汉林 王瑞春 顾立新 朱继红 刘善沛 黄利伟 曹蓓蓓 吴俊� 于 2021-10-14 设计创作，主要内容包括：本发明公开了一种色散优化弯曲不敏感光纤,其在芯层和下陷包层之间,设有过渡下陷包层,所述过渡下陷包层的相对折射率差由内而外从0%连续变化至下陷包层的交界点的相对折射率差。本发明采用双下陷包层对波导色散和宏弯性能进行平衡优化,保证光纤的弯曲性能不受影响的前提下降低其色散系数；其中处于芯层和下陷包层之间的过渡下陷包层,其折射率连续变化,来降低波导结构中芯层与包层的折射率差异带来的波导色散,限定过渡下陷包层的折射率分布和宽度,优化了色散系数,避免了凸起包层带来的在小弯曲半径下的弯曲损耗过大的问题。(The invention discloses a dispersion optimized bend insensitive fiber, which is provided with a transitional depressed cladding between a core layer and a depressed cladding, wherein the relative refractive index difference of the transitional depressed cladding is continuously changed from 0 percent from inside to outside to the relative refractive index difference of a junction point of the depressed cladding. The invention adopts double sunken claddings to carry out balanced optimization on waveguide dispersion and macrobending performance, and the dispersion coefficient is reduced on the premise of ensuring that the bending performance of the optical fiber is not influenced; the refractive index of the transitional depressed cladding layer between the core layer and the depressed cladding layer is continuously changed, so that the waveguide dispersion caused by the refractive index difference between the core layer and the cladding layer in the waveguide structure is reduced, the refractive index distribution and the width of the transitional depressed cladding layer are limited, the dispersion coefficient is optimized, and the problem of overlarge bending loss under a small bending radius caused by a raised cladding layer is solved.)

1. A dispersion optimized bend insensitive optical fiber is characterized by comprising a core layer and a depressed cladding layer, wherein a transitional depressed cladding layer is arranged between the core layer and the depressed cladding layer, and the relative refractive index difference of the transitional depressed cladding layer is continuously changed from 0% from inside to outside to the relative refractive index difference of a junction point of the depressed cladding layer.

2. The dispersion optimized bend insensitive optical fiber of claim 1, wherein the phases of said depressed transition cladding layerFor refractive index difference change curve ofA sub-parabolic profile.

3. The dispersion optimized bend insensitive optical fiber of claim 2, wherein the relative refractive index difference profile of said depressed transition cladding is expressed as:

whereinFor the transition of a certain point in the sunken cladding to the boundary distance of the cladding,is the relative refractive index difference at that point,in order to obtain the distribution index,the refractive index of the core layer is relative to pure silica i.e. its relative refractive index difference,in order to lower the refractive index of the cladding relative to pure silica i.e. its relative refractive index difference,the cladding width is depressed for transition.

4. The dispersion optimized bend insensitive optical fiber of claim 2, wherein said depressed transition cladding widthRadius of core layer ₁Ratio of (A to B) ₂/ ₁The value is between 1.2 and 2.0.

5. The dispersion optimized bend insensitive optical fiber of claim 1, wherein said depressed cladding layer has a fluorine-doped volumeAnd transition depressed cladding fluorine-doped volumeRatio of (A to B)The value is between 5 and 20; said transitional depressed cladding doped with fluorine volumeAnd fluorine-doped volume of depressed claddingThe calculation method of (c) is as follows:

in order to transition the depressed cladding layer into a fluorine-doped volume,in order to lower the fluorine-doped volume of the cladding,the width of the cladding layer which is in transition depression,is the depressed cladding width.

6. The dispersion optimized bend insensitive optical fiber of claim 1, wherein said depressed transition cladding widthAnd depressed cladding widthThe following conditions are satisfied:the value is between 1.3 and 1.9.

7. The dispersion optimized bend insensitive optical fiber of claim 1, wherein said depressed transition cladding width4.5 to 8.0 μm.

8. The dispersion-optimized bend of claim 1Sensitive optical fiber, characterized in that said depressed cladding maximum relative refractive indexThe refractive index depression is preferably linear, arc or semicircular, and ranges from-0.55% to-0.20%.

9. The dispersion optimized bend insensitive optical fiber of claim 1, wherein the core layer has a radius3.0 to 4.0 μm, and the relative refractive index difference thereof0.30% -0.40%.

10. The dispersion optimized bend insensitive optical fiber of claim 1, wherein the glass portion of the optical fiber comprises, in order from inside to outside, a core layer, a depressed transition cladding layer, a depressed cladding layer, and the remainder being a layer of pure silica glass.

11. The dispersion optimized bend insensitive optical fiber of claim 10, wherein G657a2 standard is satisfied; the core layer of radius ₁3.0 to 4.0 μm, and the relative refractive index difference thereof0.30% -0.40%; said depressed transition cladding having a width4.5 to 8.0 μm, and the relative refractive index difference thereofSatisfy the requirement ofParabolic distribution, distribution indexBetween 2 and 4; width of said depressed cladding5.0 to 9.0 μm, and the relative refractive index difference thereofIs-0.35 to-0.20 percent; or meets the G657B3 standard, the core layer, the radius of the core layer ₁3.2 to 3.8 μm, and the relative refractive index difference0.35% -0.40%; said depressed transition cladding having a width4.5 to 7.0 μm, and the relative refractive index difference thereofSatisfy the requirement ofParabolic distribution, distribution indexBetween 2 and 5; said depressed cladding layer having a width5.0 to 8.0 μm, and the relative refractive index difference thereofThe content is-0.55 to-0.40 percent.

Technical Field

The invention belongs to the field of optical fiber communication, and particularly relates to a dispersion optimized bend insensitive optical fiber.

Background

Dispersion is an important transmission characteristic of optical fibers. Dispersion is a physical effect that produces different time delays due to different frequencies or mode components of the light wave traveling at different speeds. With the continuous increase of the transmission distance of the optical fiber, the broadening of the optical pulse caused by the dispersion causes the mutual overlapping of the front pulse and the rear pulse, which causes the intersymbol interference of the digital signal and increases the error rate. The dispersion mainly existing in the single-mode fiber is material dispersion and waveguide dispersion, and the material dispersion is a dispersion characteristic caused by signal pulse broadening caused by the change of the group refractive index of the material along with the wavelength. Waveguide dispersion is dispersion caused by different group velocities due to different phase constants and different group velocities of one guided wave mode in an optical fiber at different frequencies. The dispersion of the optical fiber not only affects the transmission capacity of the optical fiber, but also limits the product value of the bandwidth and the distance of the optical fiber, and also limits the relay distance of the optical fiber communication system. The larger the dispersion, the smaller the product of bandwidth and distance in the fiber, and at a certain transmission distance, the smaller the bandwidth, and the size of the bandwidth determines the size of the transmission information capacity.

The G657 optical fiber is widely applied to high-density wiring networks due to the excellent bending insensitivity of the G657 optical fiber, and the improvement of the dispersion performance of the G657A2 bending insensitivity single-mode optical fiber has important significance for meeting the requirements of high-speed, large-capacity and long-distance transmission of an optical fiber communication system.

The bend-insensitive optical fiber generally has a depressed cladding, and the bend-insensitive single-mode optical fiber patent documents CN110780379B, CN110749953A, CN103257397B and CN102200610B which optimize the dispersion performance of the bend-insensitive optical fiber adopt the depressed cladding and also arrange a convex cladding, but from example data, the design of the convex cladding of the dispersion-optimized single-mode optical fiber is difficult to meet the bending loss requirements of g.657.a2 and g.657.b3 under a small bending radius.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a dispersion optimized bend insensitive optical fiber, which aims to optimize the dispersion performance of the optical fiber while meeting the bend insensitive performance requirement of a single mode fiber through a transitional sunken cladding with gradually changed refractive index, thereby solving the technical problem that the existing dispersion optimized single mode fiber has a convex cladding and is difficult to meet the bend loss performance requirement under the condition of small bend radius change.

To achieve the above objects, according to one aspect of the present invention, there is provided a dispersion optimized bend insensitive optical fiber comprising a core layer and a depressed cladding layer, between which a transitional depressed cladding layer is disposed, the relative refractive index difference of which continuously varies from 0% from inside to outside to the relative refractive index difference of the boundary point of the depressed cladding layer.

Preferably, the dispersion-optimized bend-insensitive optical fiber has a depressed-transition cladding with a profile of relative refractive index differenceA sub-parabolic profile.

Preferably, the dispersion-optimized bend-insensitive optical fiber has a relative refractive index difference change curve of the transition depressed cladding expressed as:

whereinFor the transition of a certain point in the sunken cladding to the boundary distance of the cladding,is the relative refractive index difference at that point,is a distribution index, preferably between 0.25 and 5, more preferably between 2 and 4.25In the middle of the furnace, the gas-liquid separation chamber,the refractive index of the core layer is relative to pure silica i.e. its relative refractive index difference,to lower the refractive index of the cladding relative to pure silica,the cladding width is depressed for transition.

Preferably, the dispersion optimized bend insensitive fiber has a depressed transition cladding widthRadius of core layer ₁Ratio of (A to B)The value is between 1.2 and 2.0.

Preferably, the dispersion optimized bend insensitive optical fiber has a fluorine doped volume of its depressed claddingAnd transition depressed cladding fluorine-doped volumeRatio of (A to B)The value is between 5 and 20; said transitional depressed cladding doped with fluorine volumeAnd fluorine-doped volume of depressed claddingIs calculated byThe formula is as follows:

in order to transition the depressed cladding layer into a fluorine-doped volume,in order to lower the fluorine-doped volume of the cladding,the width of the cladding layer which is in transition depression,is the depressed cladding width.

Preferably, the dispersion optimized bend insensitive fiber has a depressed transition cladding widthAnd depressed cladding widthThe following conditions are satisfied:the value is between 1.3 and 1.9.

Preferably, the dispersion optimized bend insensitive fiber has a depressed transition cladding width4.5 to 8.0 μm.

Preferably, the dispersion optimized bend insensitive fiber has a depressed cladding maximum relative refractive indexThe refractive index depression is preferably linear, arc or semicircular, and ranges from-0.55% to-0.20%.

Preferably, the dispersion optimized bend insensitive optical fiber has a core radius ₁3.0 to 4.0 μm, and the relative refractive index difference thereof0.30% -0.40%.

Preferably, the optical fiber glass part of the dispersion-optimized bend-insensitive optical fiber sequentially comprises a core layer, a transitional depressed cladding layer and a depressed cladding layer from inside to outside, and the rest is a pure silica glass layer.

Preferably, the dispersion optimized bend insensitive fiber meets the G657a2 standard; the core layer of radius ₁3.0 to 4.0 μm, and the relative refractive index difference thereof0.30% -0.40%; said depressed transition cladding having a width4.5 to 8.0 μm, and the relative refractive index difference thereofSatisfy the requirement ofParabolic distribution, distribution indexBetween 2 and 4; said depressed cladding layer having a width5.0 to 9.0 μm, and the relative refractive index difference thereofIs-0.35 to-0.20 percent; or

Meets the G657B3 standard, the core layer, the radius of the core layer ₁3.2 to 3.8 μm, and the relative refractive index difference0.35% -0.40%; said depressed transition cladding having a width4.5 to 7.0 μm, and the relative refractive index difference thereofSatisfy the requirement ofParabolic distribution, distribution indexBetween 2 and 5; said depressed cladding layer having a width5.0 to 8.0 μm, and the relative refractive index difference thereofThe content is-0.55 to-0.40 percent.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

the invention adopts double sunken claddings to carry out balanced optimization on waveguide dispersion and macrobending performance, and the dispersion coefficient is reduced on the premise of ensuring that the bending performance of the optical fiber is not influenced; the refractive index of the transitional depressed cladding between the core layer and the depressed cladding is continuously changed, and the transitional depressed cladding with the refractive index complying with alpha-order distribution is preferably adopted to reduce waveguide dispersion caused by the refractive index difference between the core layer and the cladding in the waveguide structure, limit the refractive index distribution and the width of the transitional depressed cladding, optimize the dispersion coefficient and avoid the problem of overlarge bending loss under small bending radius caused by a raised cladding.

In the preferable scheme, the sunken cladding layer is adopted, and the fluorine-doped volume ratio of the transitional sunken cladding layer and the final sunken cladding layer is optimized to realize friendly combination of low dispersion coefficient and excellent bending property, so that the bending loss requirements of G.657.A2 and G.657.B3 under a small bending radius are met. The optical fiber of the preferred scheme of the invention conforms to the standards of G.657.A2 and G.657.B3, simultaneously keeps good macrobend loss and lower dispersion coefficient, has simple preparation process, is suitable for large-scale production, and can meet the requirements of high-speed, large-capacity and long-distance transmission of an optical fiber communication system.

Drawings

FIG. 1 is a schematic cross-sectional view of a dispersion-optimized bend insensitive optical fiber with a linearly depressed cladding according to an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a dispersion optimized bend insensitive optical fiber with an arcuately depressed cladding according to an embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a dispersion optimized bend insensitive optical fiber with a semi-circular depressed cladding according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The following are definitions and descriptions of some terms involved in the present invention:

the OVD process comprises the following steps: the quartz glass with the required thickness and the required refractive index profile is prepared by an external vapor deposition and sintering process.

The PCVD process comprises the following steps: and preparing the quartz glass with the required thickness and the required refractive index profile by using a plasma chemical vapor deposition process.

VAD process: the quartz glass with the required thickness and the required refractive index profile is prepared by axial vapor deposition and sintering processes.

And (3) a melting and shrinking process: and carrying out high-temperature fusion shrinkage by using a doped quartz glass rod and a doped quartz liner tube to obtain quartz glass with the required thickness and the required refractive index profile.

Performing: the optical fiber is a material prefabricated member which is distributed by a core layer and a cladding layer and can be drawn according to the design requirement of the optical fiber.

The relative refractive index Δ ni of each layer of the optical fiber is defined by the following equation, Δ ni =Where ni is the refractive index of the glass at each location of the fiber and nc is the refractive index of the outer cladding, i.e., the refractive index of pure silica.

The optical fiber glass part sequentially comprises a core layer, a transitional sunken cladding layer and a sunken cladding layer from inside to outside, and the rest is a pure silica glass layer; the transition depressed cladding is arranged between the core layer and the depressed cladding, and the relative refractive index difference of the transition depressed cladding continuously changes from 0% from inside to outside, preferably continuously and monotonically changes to the relative refractive index difference of a boundary point of the depressed cladding.

The radius r1 of the core layer is 3.0-4.0 mu m, the relative refractive index difference delta n1 is 0.32-0.39%, the core layer is a Ge-doped silica glass layer, and the contribution delta n1 of the relative refractive index of germanium in the core layer is 0.32-0.39%.

The relative refractive index difference change curve of the transitional depressed cladding isA sub-parabolic distribution; preferably can be expressed as:

whereinFor the transition of a certain point in the sunken cladding to the boundary distance of the cladding,a distribution index of between 0.25 and 5, preferably between 1.0 and 4.5, more preferably between 2 and 4.25,the refractive index of the core layer is relative to pure silica i.e. its relative refractive index difference,for the refractive index of the final depressed cladding relative to pure silica i.e. its relative refractive index difference,the cladding width is depressed for transition. Maximum relative refractive index difference of transition depressed claddingThe cladding width is-0.15% -0.04%, and the transitional sinking cladding width4.5 to 8.0 μm.

Maximum relative refractive index difference of the depressed claddingThe refractive index of the region is kept to be continuously changed to form a recess, and the recess can be linear, arc or semicircular. Width of sunken cladding5.0 to 10.0 μm.

Said transition depressed cladding widthRadius of core layerRatio of (A to B)The value is between 1.2 and 2.0. Said transition depressed cladding widthAnd depressed cladding widthThe following conditions are satisfied:the value is between 1.3 and 1.9.

Fluorine-doped volume of said depressed claddingAnd transition depressed cladding fluorine-doped volumeRatio of (A to B)The value is between 5 and 20; said transitional depressed cladding doped with fluorine volumeAnd fluorine-doped volume of depressed claddingThe calculation method of (c) is as follows:

in order to transition the depressed cladding layer into a fluorine-doped volume,the depressed cladding is doped with fluorine volume.

The single-mode fiber dispersion is 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. Fiber dispersion optimizes common raised claddings, however, the presence of raised claddings seriously affects the macrobending performance of the fiber. The invention cancels a convex cladding, adopts the design of a double-sunken cladding of a transitional sunken cladding and a sunken cladding to balance and optimize the waveguide dispersion and macrobending performance, adopts an alpha-time distribution transitional sunken cladding to reduce the waveguide dispersion caused by the refractive index difference between a core layer and the cladding in a waveguide structure, and limits the refractive index distribution and the width of the transitional sunken cladding, so that the dispersion coefficient is obviously improved under the action of the transitional sunken cladding under the condition of the increase of the dispersion coefficient caused by the overlarge refractive index difference between the core layer and the sunken cladding.

The manufacturing method adopted by the optical fiber is that PCVD/VAD + sleeve liner tube fusion shrinkage + OVD technology is used for preparing the needed optical fiber preform, VAD technology or PCVD technology is used for preparing a core rod corresponding to an optical fiber core layer and an F-doped transitional sunken cladding layer, a doped quartz liner tube is used for preparing the corresponding needed F-doped sunken cladding layer, and the core rod and the F-doped liner tube are fused into a solid rod at high temperature to carry out OVD technology outer cladding treatment; the preform prepared by the OVD can be drawn by matching with a coater to obtain the dispersion-optimized bent insensitive single-mode fiber.

The following are examples:

in the examples:

the test method of the cut-off wavelength lambda cc of the optical cable refers to the method specified in IEC 60793-1-44;

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

the microbending loss test method refers to the method B in IEC-62221;

examples 1-1 to 10G 657A2 Standard optical fiber

The geometrical dimensions and refractive index parameters of the G657A2 standard fiber are shown in the following table;

the relative refractive index difference profile of the depressed transition cladding can be expressed as:

whereinFor the transition of a certain point in the sunken cladding to the boundary distance of the cladding,in order to obtain the distribution index,the refractive index of the core layer is relative to pure silica i.e. its relative refractive index difference,in order to lower the refractive index of the cladding relative to pure silica i.e. its relative refractive index difference,the cladding width is depressed for transition.

Through tests, the attenuation of the G657A2 standard optical fiber provided by the embodiments 1-10 at the wavelength of 1310nm is less than or equal to 0.330 dB/km; attenuation at a wavelength of 1383nm is not more than 0.284 dB/km; attenuation at the wavelength of 1550nm is less than or equal to 0.190 dB/km; attenuation at a wavelength of 1625nm is less than or equal to 0.210 dB/km;

the diameter of a mode field at 1310nm is 8.4-9.0 mu m, and the cut-off wavelength of the optical cable is less than or equal to 1260 nm;

the zero dispersion wavelength of the optical fiber is 1300-1324 nm, and the dispersion slope of the optical fiber at the zero dispersion wavelength is equal to or less than 0.087ps/nm²·km；

Its Abbe number at a wavelength of 1550nm is equal to or less than 17 ps/nm/km.

Its Abbe number at a wavelength of 1625nm is equal to or less than 21.2 ps/nm/km.

The macro-bending loss of the 1550nm window at the R15mm-10 circles is less than or equal to 0.03dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.1 dB; the macrobending loss of a 1550nm window at R10mm-1 turn is less than or equal to 0.06 dB, and the macrobending loss of a 1625nm window is less than or equal to 0.1 dB; and the macrobending loss of a 1550nm window at R7.5mm-1 circle is less than or equal to 0.2db, and the macrobending loss of a 1625nm window is less than or equal to 0.5 db.

The microbending loss of the optical fiber at the wavelength of 1700nm is less than or equal to 1 dB/km.

The specific test results are shown in the following table:

examples 2-1 to 10G 657B3 Standard optical fiber

The geometrical dimensions and refractive index parameters of the G657B3 standard fiber are shown in the following table;

the refractive index profile of the depressed transition cladding can be expressed as:

whereinFor the transition of a certain point in the sunken cladding to the boundary distance of the cladding,in order to obtain the distribution index,is the refractive index of the core layer relative to pure silica,to lower the refractive index of the cladding relative to pure silica,the cladding width is depressed for transition.

Through tests, the attenuation of the G657B3 standard optical fiber provided by the embodiments 2-1-10 at the wavelength of 1310nm is less than or equal to 0.330 dB/km; attenuation at a wavelength of 1383nm is not more than 0.284 dB/km; attenuation at the wavelength of 1550nm is less than or equal to 0.190 dB/km; attenuation at a wavelength of 1625nm is less than or equal to 0.210 dB/km;

the diameter of the mode field at 1310nm is more than or equal to 8.4 mu m, and the cut-off wavelength of the optical cable is less than or equal to 1260 nm;

the zero dispersion wavelength of the optical fiber is 1300-1324 nm, and the dispersion slope of the optical fiber at the zero dispersion wavelength is equal to or less than 0.088ps/nm²·km；

Its Abbe number at a wavelength of 1550nm is equal to or less than 17 ps/nm/km.

Its Abbe number at a wavelength of 1625nm is equal to or less than 21.4 ps/nm/km.

The macro-bending loss of the 1550nm window at the R10mm-1 turn is less than or equal to 0.03dB, and the macro-bending loss of the 1625nm window is less than or equal to 0.1 dB; the macrobending loss of a 1550nm window at R7.5mm-1 circle is less than or equal to 0.08 dB, and the macrobending loss of a 1625nm window is less than or equal to 0.25 dB; the macrobending loss of the 1550nm window in an R5.0mm-1 circle is less than or equal to 0.1db, and the macrobending loss of the 1625nm window is less than or equal to 0.3 db.

The specific test results are shown in the following table:

in the above embodiment: the depressed cladding is a linear optical fiber, and the typical refractive index profile is shown in fig. 1, in this embodiment, only the depressed cladding with uniform refractive index is taken as an example; the depressed cladding is an arc-shaped fiber with a typical refractive index profile as shown in FIG. 2; the lower cladding is semi-circular with a typical refractive index profile as shown in figure 3.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.