WO2020119439A1 - Single-mode optical fiber having low loss and large effective area and preparation method therefor - Google Patents

Abstract

A single-mode optical fiber having low loss and a large effective area, the optical fiber sequentially comprising from the inside-out an inner core layer, an outer core layer, an inner cladding layer, a sunken layer and an outer cladding layer, wherein the inner core layer, the outer core layer, the inner cladding layer and the sunken layer use silicon dioxide as a substrate material and have a dopant added thereto, the inner core layer has a radius of 4-7 μm and a relative refractive index of 0.25%-0.45%; the outer core layer has a radius of 5-9μm and a relative refractive index of Δn2=0.1%-0.3%; the inner cladding radius has a radius of 9.5-15μm and a relative refractive index of -0.02%-0.02%; the sunken layer has a radius of 12-25μm and a relative refractive index of -0.15%-0.55%; and the outer cladding layer is pure silica and has a radius of 60-65μm. Also provided is a method for preparing the single-mode optical fiber having low loss and large effective area. The present optical fiber has good comprehensive properties such as effective area, cut-off wavelength, attenuation, dispersion and bending loss.

Description

Single-mode optical fiber with low loss and large effective area and preparation method thereof

This application requires the application number of the State Intellectual Property Office of China: 201811531094.X Application date: 2018-12-14 Priority of the invention patent application, the content of the priority text is expressly incorporated by reference into this application.

Technical field

The invention relates to a low-loss large-effective-area single-mode optical fiber and a preparation method thereof, which belong to the technical field of optical fiber transmission.

Background technique

Optical fiber communication technology is changing our world at an incredible speed. Optical fiber is used as a medium for transmitting optical signals. Fiber attenuation and effective area are important factors that currently affect optical fiber transmission performance. In the future 400G or higher transmission system, the reduction of fiber attenuation and the increase of effective area will greatly improve the transmission quality of fiber and greatly reduce the construction and maintenance cost of the entire system.

The effective area is used to measure the transmission capacity of optical energy. The large effective area is conducive to the transmission of optical signals and can effectively increase the capacity of optical fiber transmission. At present, the effective area of optical fiber is above 100 μm ^{2. The} large effective area can be changed by changing the fiber core , The refractive index distribution of the cladding, the size of the core and the duty cycle of the cladding, however, increasing the effective area of the fiber, with the increase in loss, thus limiting the expansion of the effective area of the fiber; in addition, increasing the fiber Although the core diameter can obtain a larger effective area, it also causes the cut-off wavelength of the optical fiber to increase rapidly.

Patent No. CN107132614A proposes a large effective area optical fiber, using a simple refractive index stepped cladding structure design, the effective area of the fiber is 105～135μm ² , and the fiber's cable cut-off wavelength is 1407-1437nm, at 1550nm The dispersion at the wavelength is 17-23ps/nm*km, and the loss at the 1550nm wavelength is 0.180-0.184dB/km; however, the fiber has the following problems: the core layer and the depressed layer are closely connected, and the refractive index differs greatly. The cut-off wavelength is too high; the optical power is easy to leak into the sink layer and refract out of the optical fiber, resulting in increased attenuation; there is no isolation layer between the sink layer and the core layer, which easily causes fluorine to diffuse into the core layer.

In addition, the patent number CN104459876B proposes a low-loss large effective area fiber. The fiber is designed with a depressed inner core structure. The effective area of the fiber at the wavelength of 1550nm is 110-147μm ² and the cable cut-off wavelength is 1389. -1522nm, the loss at 1550nm is 0.162-0.181dB/km; however, the refractive index of the inner core layer of the optical fiber is smaller than the refractive index of the outer core layer, which causes the change of the incident angle of the optical power during propagation to increase the loss. Concentrated propagation, and its cable cut-off wavelength is large, in practical applications, too high a cut-off wavelength is difficult to ensure that the optical fiber is cut off in the application band, it can not guarantee that the optical signal is in a single-mode state during transmission.

Summary of the invention

The technical problem to be solved by the invention is to provide a low-loss large-effective-area single-mode optical fiber and a preparation method thereof in order to solve the technical problems of the existing single-mode optical fiber with small effective area, large loss, high cut-off wavelength and the like.

The technical solutions adopted by the present invention to solve its technical problems are:

A low-loss large-effective-area single-mode optical fiber, from inner to outer, inner core layer, outer core layer, inner cladding layer, depressed layer and outer cladding layer, in which: inner core layer, outer core layer, inner cladding layer, depressed layer Silica is used as the base material and dopant is added; the radius of the inner core layer is r ₁ = 4-7 μm, the relative refractive index of the inner core layer is △n ₁ = 0.25% to 0.45%; the radius of the outer core layer is r ₂ = 5～9μm, the relative refractive index of the outer core layer is △n ₂ =0.1%～0.3%; the radius of the inner cladding layer is r ₃ =9.5～15μm, the relative refractive index of the inner cladding layer is △n ₃ =-0.02% ～0.02%; the radius of the depressed layer is r ₄ =12～25μm, the relative refractive index of the depressed layer is △n ₄ =-0.15%～-0.55%; the outer cladding is pure silica, the outer cladding radius r ₅ =60 -65μm.

Preferably, the relative refractive index is: Δn ₁ >Δn ₂ >Δn ₃ >Δn ₄ .

Preferably, the dopants added to the inner core layer and the outer core layer are at least one of GeO ₂ , P ₂ O ₅ -F mixture, and B ₂ O ₃ .

Furthermore, when the dopant is a P ₂ O ₅ -F mixture, the doping contribution Δn _{P of P} is 0.3%-0.6%.

Preferably, the inner cladding layer is a silica glass layer doped with germanium and fluorine, wherein the doping contribution of _Ge Δn _Ge is 0.01%-0.05%.

Preferably, the depressed layer is a fluorine-doped silica glass layer.

Preferably, the effective area of the optical fiber at a wavelength of 1550 nm is 151-162 μm ² .

Preferably, the cut-off wavelength of the fiber-optic cable is equal to or less than 1316 nm.

Preferably, the attenuation of the optical fiber at a wavelength of 1550 nm is equal to or less than 0.15 dB/km.

Preferably, the dispersion of the optical fiber at a wavelength of 1550 nm is equal to or less than 17 ps/nm*km.

Preferably, at the wavelength of 1550 nm, the macrobending loss of R15mm bending radius for 10 turns is equal to or less than 0.02dB, and the R30mm bend radius of 100 turns bending is equal to or less than 0.06dB.

The invention also provides a method for preparing a single-mode optical fiber with a low loss and a large effective area. The preparation method is MCVD+OVD. The preparation steps are as follows:

Use the MCVD process to deposit an inner cladding layer on the inner wall of the fluorine-doped quartz tube as the sinking layer, and then deposit an outer core layer and an inner core layer to obtain a deposition tube;

The deposition tube is melted and shrunk at a high temperature into a solid prefabricated core rod with an inner core layer, an outer core layer, an inner cladding layer and a depressed layer;

An OVD process is used to deposit an outer cladding layer on a prefabricated mandrel, and after sintering, an optical fiber with a low loss and a large effective area is prepared.

In addition, in order to clearly explain the technical solutions of the present invention, the definitions and descriptions of the terms involved in the present invention are as follows:

The relative refractive index Δn _i is defined by the following equation:

Among them, n _i is the absolute refractive index of the fiber at a specific position, and n _c is the absolute refractive index of synthetic pure silica glass.

The doping contribution Δn _{Ge of} P is defined by the following equation:

Where n _P is the dopant P ₂ O ₅ -F mixture of the inner core layer and the outer core layer, the refractive index rise caused by P doping, and n _c is the absolute refractive index of synthetic pure quartz glass.

The doping contribution Δn _{Ge of Ge} is defined by the following equation:

Among them, n _Ge is the refractive index increase caused by Ge doping of the inner cladding glass, and n _c is the absolute refractive index of synthetic pure quartz glass.

The effective area A _{eff of the} optical fiber is defined by the following equation:

Where E is the electric field related to propagation and R is the distance from the axis to the point where the electric field is distributed.

Optical cable cut-off wavelength λ _cc :

The IEC (International Commission) standard 60793-1-44 defines: The cable cut-off wavelength λ _cc is the wavelength at which the optical signal no longer propagates as a single-mode signal after it has propagated through the fiber for 22 meters. During the test, one loop of 14 cm radius and two loops of 4 cm radius are needed to obtain data.

The beneficial effects of the present invention are:

The low-loss large-effective-area single-mode optical fiber provided by the present invention has a core layer divided into an inner core layer and an outer core layer with appropriate relative refractive index differences and radii, and further adding dopants to the inner core layer and the outer core layer , Can increase the effective area and reduce the attenuation coefficient of the optical fiber; the increase in the diameter of the outer core layer can fine-tune the effective area, and can adjust the difference in refractive index, thereby reducing the cutoff wavelength; the design of the inner cladding can prevent the alkali metal from diffusing to the fluorine-doped concentration The higher sink layer forms metal fluoride crystals, which reduces attenuation and prevents the fluorine ions of the sink layer from diffusing into the core layer; the sink layer uses a fluorine-doped design, so that the effective area of the optical fiber at 1550nm wavelength is 151～162μm ² , At the same time, the distribution range of optical power is limited, so that the optical power is concentrated in the core layer of the optical fiber, which is helpful to reduce the attenuation of light and improve the bending resistance of the optical fiber; the outermost cladding is designed with pure silica, which reduces the The proportion of fluorine-doped glass in the optical fiber reduces the manufacturing cost. In short, the comprehensive performance of the optical fiber of the present invention, such as effective area, cut-off wavelength, attenuation, dispersion, bending loss, etc., is good in the application band. The cut-off wavelength of the cable can ensure the single-mode propagation of optical signals in the fiber. This fiber can be used for high speed and large capacity Long-distance transmission and long-distance transmission system without relay station.

BRIEF DESCRIPTION

The present invention is further described below with reference to the drawings and embodiments.

1 is a distribution diagram of the refractive index cross-sectional structure of the single-mode optical fiber of the present invention, the horizontal axis represents the cross-sectional radius of each layer of the optical fiber, and the vertical axis represents the relative refractive index corresponding to each layer.

detailed description

The present invention will now be described in further detail with reference to the drawings.

A low-loss large-effective-area single-mode optical fiber, from inner to outer, inner core layer, outer core layer, inner cladding layer, depressed layer and outer cladding layer, in which: inner core layer, outer core layer, inner cladding layer, depressed layer Silica is used as the base material and dopant is added; the radius of the inner core layer is r ₁ = 4-7 μm, the relative refractive index of the inner core layer is △n ₁ = 0.25% to 0.45%; the radius of the outer core layer is r ₂ = 5～9μm, the relative refractive index of the outer core layer is △n ₂ =0.1%～0.3%; the radius of the inner cladding layer is r ₃ =9.5～15μm, the relative refractive index of the inner cladding layer is △n ₃ =-0.02% ～0.02%; the radius of the depressed layer is r ₄ =12～25μm, the relative refractive index of the depressed layer is △n ₄ =-0.15%～-0.55%, the outer cladding layer is pure silica r ₅ ; The relative refractive index is: Δn ₁ >Δn ₂ >Δn ₃ >Δn ₄ ;

When the dopant added to the inner core layer and the outer core layer is at least one of GeO ₂ , P ₂ O ₅ -F mixture, and B ₂ O ₃ , when the dopant is P ₂ O ₅ -F mixture , The doping contribution Δn _F of P is 0.1%-0.6%, and the reasonable design of the relative refractive index difference and radius of the inner core layer and the outer core layer effectively reduces the refractive index of the fiber core layer and increases the effectiveness of the fiber The area reduces the attenuation coefficient of the optical fiber; the inner cladding is a silica glass layer doped with germanium and fluorine, in which the Ge doping contribution Δn _Ge is 0.01%-0.05%. The purpose is to prevent the fluoride ion diffusion of the alkali metal or the sagging layer of the core layer; the sagging layer closely surrounds the inner cladding, the sagging layer is a fluorine-doped silica glass layer, and its main function is to reduce the macrobending loss of the optical fiber.

The single-mode optical fiber of the present invention is prepared by the MCVD+OVD process, specifically:

First, the mandrel is deposited by MCVD process and the structure of the depressed layer is used. The fluorine-doped quartz tube is used as the deposition reaction tube. The inner cladding is deposited on the inner wall of the deposition reaction tube as the depressed layer to prevent the moisture of the reaction tube from expanding into the core layer. Then deposit the outer core layer and the inner core layer to obtain a deposition tube that meets the requirements of the refractive index distribution; after the deposition is completed, the deposited reaction tube is melted and shrunk into a solid prefabricated core rod. The process of the melting and shrinking stage is as follows: the temperature of the furnace T=22000 ℃, furnace speed VF=15mm/min, pump end pressure is -500Pa; MCVD process has the advantages of flexible operation, precise control of raw material flow and number of layers, and can prepare optical fiber preform with fine refractive index profile.

Secondly, the OVD process is used to deposit an outer cladding layer on the prefabricated mandrel, and after sintering to prepare a low-loss large effective area optical fiber that meets the requirements, the OVD process can improve production efficiency and facilitate large-scale production.

Refer to Table 1 for fiber profile parameters of each embodiment of the present invention, and refer to Table 2 for fiber performance parameters.

Table 1 Fiber profile parameters of various embodiments of the present invention

Table 2 Optical fiber performance parameters of various embodiments of the present invention

It can be seen from Table 2 that the effective area of the single-mode optical fiber of the present invention is 151.3-161.5 μm ² at a wavelength of 1550 nm, the cut-off wavelength for cable formation is 1275-1316 nm, the attenuation at a wavelength of 1550 nm is 0.143-0.153 dB/km, and the wavelength at a wavelength of 1550 nm The dispersion at the location is 15.32-17.31ps/nm*km, the optical fiber at the wavelength of 1550nm, the macro bending loss of R15mm bending radius bending 10 turns is 0.014-0.020dB, the macro bending loss of R30mm bending radius bending 100 turns is 0.0054-0.0060dB It can be seen that the comprehensive performance parameters such as effective area, cut-off wavelength, attenuation, dispersion, and bending loss of the single-mode optical fiber of the present invention are good in the application band.

Taking the above-mentioned ideal embodiment according to the present invention as a revelation, through the above description, the relevant staff can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the contents of the description, and the technical scope must be determined according to the scope of the claims.

Claims (10)

1. A low-loss large-effective-area single-mode optical fiber characterized by an inner core layer, an outer core layer, an inner cladding layer, a sagging layer, and an outer cladding layer from inside to outside, in which: inner core layer, outer core layer, inner cladding layer 3. The sagging layer uses silicon dioxide as the base material and dopants are added; the radius of the inner core layer is r ₁ = 4-7 μm, and the relative refractive index of the inner core layer is △n ₁ = 0.25% to 0.45%; the outer core layer The radius of r ₂ =5～9μm, the relative refractive index of the outer core layer is △n ₂ =0.1%～0.3%; the radius of the inner cladding layer is r ₃ =9.5～15μm, the relative refractive index of the inner cladding layer is △n ₃ =-0.02%～0.02%; the radius of the depressed layer is r ₄ =12～25μm, the relative refractive index of the depressed layer is △n ₄ =-0.15%～-0.55%; the outer cladding is pure silica, the outer cladding radius r ₅ = 60-65 μm.
2. The low-loss large-effective-area single-mode optical fiber according to claim 1, wherein the relative refractive index is: Δn ₁ >Δn ₂ >Δn ₃ >Δn ₄ .
3. The low-loss large-effective-area single-mode optical fiber according to claim 1 or 2, wherein the dopants added to the inner core layer and the outer core layer are GeO ₂ , P ₂ O ₅ -F mixture, B ₂ At least one of O ₃ , when the dopant is a P ₂ O ₅ -F mixture, the doping contribution Δn _{P of P} is 0.3%-0.6%.
4. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1 to 3, wherein the inner cladding is a silica glass layer doped with germanium and fluorine, wherein the doping contribution of _Ge is Δn _Ge It is 0.01%-0.05%.
5. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1 to 4, wherein the depressed layer is a fluorine-doped silica glass layer.
6. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1 to 5, wherein the effective area of the optical fiber at a wavelength of 1550 nm is 151 to 162 μm ² .
7. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1 to 6, wherein the cable cut-off wavelength of the optical fiber is equal to or less than 1316 nm.
8. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1 to 7, wherein the attenuation of the optical fiber at a wavelength of 1550 nm is equal to or less than 0.15 dB/km, and the attenuation of the optical fiber at a wavelength of 1550 nm The dispersion is equal to or less than 17ps/nm*km.
9. The low-loss large-effective-area single-mode optical fiber according to any one of claims 1-7, wherein the macrobending loss of the optical fiber at a wavelength of 1550 nm and a bending radius of R15mm for 10 turns is equal to or less than 0.02dB and R30mm The macro bending loss for a bending radius of 100 turns is equal to or less than 0.06dB.
10. A method for preparing a single-mode optical fiber with a low loss and a large effective area is characterized by adopting the preparation method of MCVD+OVD. The preparation steps are as follows:

    Use the MCVD process to deposit an inner cladding layer on the inner wall of the fluorine-doped quartz tube as the sinking layer, and then deposit an outer core layer and an inner core layer to obtain a deposition tube;

    The deposition tube is melted and shrunk at a high temperature into a solid prefabricated core rod with an inner core layer, an outer core layer, an inner cladding layer and a depressed layer;

    An OVD process is used to deposit an outer cladding layer on a prefabricated mandrel, and after sintering, an optical fiber with a low loss and a large effective area is prepared.

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