WO2019085693A1

WO2019085693A1 - Preparation of ultra-low loss optical fiber preform and optical fiber by means of axial vapor deposition

Info

Publication number: WO2019085693A1
Application number: PCT/CN2018/107462
Authority: WO
Inventors: 劳雪刚; 王友兵
Original assignee: 江苏亨通光导新材料有限公司; 江苏亨通光电股份有限公司
Priority date: 2017-11-01
Filing date: 2018-09-26
Publication date: 2019-05-09
Also published as: RU2718453C1; CN107721149A

Abstract

Disclosed is an ultra-low loss optical fiber, wherein by adding an alkali metal element during a VAD deposition process, the viscosity of a core layer is lowered, and same is more matched with an inner cladding layer and an outer cladding layer; furthermore, the internal stress is lowered, thereby producing an ultra-low loss optical fiber with a low transmission attenuation. A method for preparing the ultra-low loss optical fiber is based on a traditional VAD deposition process, wherein a small amount of alkali metal is doped during the deposition process; furthermore, the doping amount is small, and the gas flow rate is small, such that the normal deposition process is not excessively affected, and the doping is completed during the deposition process without prolonging the production cycle; therefore, the stable production can be ensured, the production process is not complicated, and same can be used for large-scale production.

Description

Preparation of super-loss optical fiber preforms and optical fibers by axial vapor deposition

[0001] The present invention relates to the field of optical fiber communication technologies, and in particular, to an ultra-low loss optical fiber preform and an optical fiber prepared by an axial vapor deposition method.

Background technique

[0002] With the continuous development of long-distance optical fiber transmission, especially Internet technology and technologies such as 4G and passive optical networks, the requirements for reducing fiber loss are becoming higher and higher. At present, ultra-low loss fiber core rods are mostly made of pure silicon core rods containing a small amount of alkali metal. Chinese patents CN103472529A and CN102654602A both provide a pure silicon core solution for the preparation of low-loss optical fibers, the use of a core layer is not terrible Ge, the inner cladding is deep and the fluorine is bad, and the outer cladding is normally terrible, which involves the preparation of a deep fluorine inner cladding, deep fluorine The process is difficult, the radial refractive index uniformity is poor, the process is prepared by the tube method, and the size of the light bar is limited by the basic quartz tube, which is difficult to achieve mass production.

[0003] Existing low-loss optical fiber mandrel alkali metal miscellaneous processes mostly use extra-tube heating, such as CN103502164A and CN102730977A. However, this method is slow in production, so it is inefficient and costly after industrialization.

technical problem

Problem solution

Technical solution

In view of the above-discussed deficiencies in the prior art, it is an object of the present invention to provide an axial vapor deposition process for the preparation of ultra low loss optical fiber preforms and optical fibers.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An ultra-low loss optical fiber comprising a core layer, an inner cladding layer and an outer cladding layer which are sequentially coated, wherein the core layer is a pure silicon rod which is a miscellaneous alkali metal ion, and the alkali metal ion in the core layer is cumbersome The concentration is from 200 ppm to 500 ppm, the inner cladding is a fluorocarbon quartz sleeve, and the outer cladding is an OVD synthetic outer cladding; the relative refractive index difference between the core layer and the inner cladding is Δ1 «0.4%-0.6%, The relative refractive index difference Δ between the inner cladding and the outer cladding 2«-0.3%--0.4%.

[0007] Further, the inner wall of the tube of the fluorocarbon quartz sleeve is deposited by a gas phase reaction to form a layer of fluorosilicate, which is formed layer by layer until the refractive index conforms to the relative refractive index difference between the core layer and the inner cladding.

[0008] Further, the inner cladding has a terrible fluorine concentration of 500 ppm to 800 ppm.

[0009] Further, the core layer has a diameter of 7 μm to 8 μm, and a sum of diameters of the outer cladding layer and the inner cladding layer is 124.5 μm to 125.5 μm.

[0010] Further, the ratio of the material viscosity of the core layer and the inner cladding layer at a high temperature of 1000 ° C is in the range of 1-1.4.

[0011] Further, the ultra-low loss fiber has an attenuation value at a wavelength of 1550 nm ≤ 0.158 (3⁄4/10^ an attenuation value at a wavelength of 1383 η m ≤ 0.28 (3⁄4/10^)

[0012] Further, the cutoff wavelength of the ultra low loss fiber after cable formation is ≤14901^1, and the mode field diameter at the wavelength of 1550 nm is ≤12.5^^1.

[0013] A method for preparing an ultra low loss optical fiber, comprising the steps of:

[0014] Step one, depositing and dissolving the alkali metal by axial vapor deposition to obtain a loose body;

[0015] Step two, the loose body is taken out to the sintering furnace for dehydration and sintering, and the alkali metal ions are diffused in the core layer during the sintering process, thereby obtaining a miscellaneous and uniform core rod;

[0016] Step 3, matching the fluorocarbon quartz sleeve as an inner cladding on the outside of the mandrel, and melting and extending to obtain an extended core rod;

[0017] Step four, after the outer core is extended to increase the outer layer, the preform is made;

[0018] Step 5, the preform is subjected to a wire drawing process.

[0019] Further, the step 1 specifically includes the following steps:

[0020] Sl, the alkali metal salt is placed in the heating cabinet below the deposition tank, the heating cabinet starts to heat, and the vapor pressure is higher than O. lkpa, the average heating rate is 10 ° C / min, until the internal temperature exceeds 900 ° C, forming Alkali metal vapor, oxygen enters the heating cabinet from the side inlet of the heating cabinet, and is mixed with the formed alkali metal vapor to form a mixed gas, and then enters the gas outlet pipe from the side outlet of the heating cabinet;

[0021] S2, the deposition tank is operated according to a normal deposition process to form a loose body;

[0022] S3, when the first burner in the deposition tank starts to spray the raw material gas including silicon tetrachloride, oxygen, and hydrogen, the alkali metal vapor valve is opened to adjust the gas outlet speed of the mixed gas in the second burner, wherein the first burner The injection points of the second burner are aligned with the central axis of the loose body, and the alkali metal can enter the entire loose body section as the loose body remains rotated.

[0023] S4, starting the normal deposition process, closing the alkali metal vapor valve near completion.

[0024] A deposition apparatus according to the above method for preparing an ultra-low loss optical fiber, comprising a deposition tank, wherein a heating cabinet for placing an alkali metal salt is disposed under the deposition tank, and one side of the heating cabinet is provided The air inlet has an air outlet on the other side, and the gas outlet is provided with an alkali metal steam valve; the same side of the deposition tank is respectively provided with a first burner for spraying the material gas at the same height and is used for a second burner that sprays the mixed gas, and the air outlet communicates with the second torch through an air outlet duct.

Advantageous effects of the invention

Beneficial effect

[0025] The outstanding effect of the present invention is: an ultra-low loss optical fiber of the present invention, by adding an alkali metal element during the VAD deposition process, the core layer viscosity is lowered, and the inner cladding layer and the outer cladding layer are more matched, and The stress is reduced to produce an ultra low loss fiber with low transmission attenuation. The optical parameters of the ultra-low loss fiber of the present invention, such as mode field diameter, cutoff wavelength and fiber attenuation, conform to the ITU-T G.654 standard, and the bending performance is higher than G.654.

standard. The preparation method of the ultra-low loss optical fiber of the invention is based on the traditional VAD deposition process, and a small amount of alkali metal is mixed during the deposition process, and the impurity amount is small, the gas flow rate is small, and the normal deposition process is not excessively affected. It is complicated to be deposited at the same time, and does not prolong the production cycle. Therefore, it can ensure stable production, and the production process is not complicated, and can be used for large-scale production. The invention can optimize the fiber attenuation to the ultra-low loss standard, and can reduce the relay station in the high-speed transmission with long distance and low attenuation, reduce the cost and improve the transmission quality.

Brief description of the drawing

DRAWINGS

1 is a schematic plan view of a radial plane of an ultra low loss fiber according to Embodiment 1-3 of the present invention;

2 is a schematic structural view of a deposition apparatus according to Embodiment 1 of the present invention;

3 is a cross-sectional view showing a depositional apparatus according to Embodiment 1 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION BEST MODE FOR CARRYING OUT THE INVENTION

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. example.

Embodiment 1

[0031] As shown in FIG. 1 , an ultra-low loss optical fiber of the embodiment includes a core layer 1 , an inner cladding layer 2 and an outer cladding layer 3 which are sequentially coated, and the core layer 1 is a pure silicon rod with a miscellaneous alkali metal ion. The concentration of the alkali metal ion in the core layer 1 is 200 ppm, the inner cladding layer 2 is the fluorocarbon quartz sleeve, and the outer cladding layer 3 is the OVD synthetic outer cladding layer; the relative refractive index difference between the core layer 1 and the inner cladding layer 2 is Δ1 «0.4% The relative refractive index difference between the inner cladding 2 and the outer cladding 3 is Δ2 «-0.3%.

[0032] The inner wall of the tube of the fluorocarbon quartz sleeve is deposited by a gas phase reaction to form a fluorosilicate layer, which is formed layer by layer until the refractive index conforms to the relative refractive index difference between the core layer 1 and the inner cladding 2.

[0033] The inner cladding 2 has a terrible fluorine concentration of 500 ppm.

The diameter of the core layer 1 is 7 μm, and the sum of the diameters of the outer cladding layer 3 and the inner cladding layer 2 is 124.5 μm.

[0035] The material viscosities of the core layer 1 and the inner cladding layer 2 have a ratio of 1 at a high temperature of 1000 °C.

[0036] A method for preparing an ultra low loss fiber, comprising the steps of:

[0037] Step one, depositing and dissolving the alkali metal by axial vapor deposition to obtain a loose body;

[0038] Step two, the loose body is taken out to the sintering furnace for dehydration and sintering, and the alkali metal ions are diffused in the core layer during the sintering process, thereby obtaining a miscellaneous and uniform core rod;

[0039] Step 3, matching the fluorocarbon quartz sleeve as an inner cladding on the outside of the mandrel, and melting and extending to obtain an extended core rod;

[0040] Step 4, after the outer core is extended to increase the outer layer, the preform is made;

[0041] Step 5: The preform is subjected to a wire drawing process.

[0042] Step one specifically includes the following steps:

[0043] Sl, the alkali metal salt is placed in the heating cabinet below the deposition tank, the heating cabinet starts to heat, and the vapor pressure is higher than O.lkpa, and the average heating rate is 10 ° C/min until the internal temperature exceeds 900 ° C. Alkali metal vapor, oxygen enters the heating cabinet from the side inlet of the heating cabinet, and is mixed with the formed alkali metal vapor to form a mixed gas, and then enters the gas outlet pipe from the side outlet of the heating cabinet;

[0044] S2, the deposition tank is operated according to a normal deposition process until the pile ball forms a loose body; [0045] S3, when the first burner in the deposition tank starts to inject a raw material gas including silicon tetrachloride, oxygen, and hydrogen, opening an alkali metal vapor valve to adjust an outlet speed of the mixed gas in the second burner, wherein the first burner The injection points of the second burner are aligned with the central axis of the loose body, and the alkali metal can enter the entire loose body section as the loose body remains rotated.

[0046] S4, starting the normal deposition process, closing the alkali metal vapor valve near completion.

[0047] As shown in FIG. 2-3, a deposition apparatus according to the above-described ultra-low loss optical fiber preparation method includes a deposition tank 21, and a heating cabinet 22 for placing an alkali metal salt is disposed under the deposition tank 21. The heating cabinet 22 is provided with an air inlet 23 on one side and an air outlet 24 on the other side, and an alkali metal vapor valve (not shown) is disposed on the air outlet 24; the same side of the deposition tank 21 is respectively disposed at The first burner 25 for injecting the material gas at the same height and the second burner 26 for injecting the mixed gas, the injection points of the first burner 25 and the second burner 26 are aligned with the central axis of the loose body 27, and the air outlet 24 passes The outlet duct 28 is in communication with the second burner 26 .

[0048] The optical parameters of the optical fiber produced in this embodiment are verified by OTDR and other related instruments, including refractive index profile, 1550 nm attenuation, 1383 nm attenuation, cutoff wavelength, mode field diameter, macrobend loss, and the like. The attenuation value of the ultra-low loss fiber at the wavelength of 1550 nm is ≤0.158 (3⁄4/10^ the attenuation value at the wavelength of 1383 nm ≤0.2 8db/km. The cutoff wavelength after ultra-low loss fiber cable is ≤1490nm, the mode at the wavelength of 1550nm Field straight ≤ 12.5μιη.

Example 2

[0050] As shown in FIG. 1 , an ultra-low loss optical fiber of the embodiment includes a core layer 1 , an inner cladding layer 2 and an outer cladding layer 3 which are sequentially coated, and the core layer 1 is a pure silicon rod with a miscellaneous alkali metal ion. The concentration of the alkali metal ion in the core layer 1 is 500 ppm, the inner cladding layer 2 is the fluorocarbon quartz sleeve, and the outer cladding layer 3 is the OVD synthetic outer cladding layer; the relative refractive index difference between the core layer 1 and the inner cladding layer 2 is Δ1 «0.6% The relative refractive index difference between the inner cladding 2 and the outer cladding 3 is Δ2 «-0.4%.

[0051] The inner wall of the tube of the fluorocarbon quartz sleeve is deposited by a gas phase reaction to form a fluorosilicate layer, which is formed layer by layer until the refractive index conforms to the relative refractive index difference between the core layer 1 and the inner cladding 2.

[0052] The inner layer 2 has a terrible fluorine concentration of 800 ppm.

The diameter of the core layer 1 is 8 μm, and the sum of the diameters of the outer cladding layer 3 and the inner cladding layer 2 is 125.5 μm.

The material viscosities of the core layer 1 and the inner cladding layer 2 have a ratio in the range of high temperature 1000 ° C of 1.4.

Example 3

[0056] As shown in FIG. 1, an ultra-low loss optical fiber of the embodiment includes a core layer 1 which is sequentially coated, and an inner cladding layer 2 And the outer layer 3, the core layer 1 is a pure silicon rod with a miscellaneous alkali metal ion, the concentration of the alkali metal ion in the core layer 1 is 400 ppm, the inner cladding layer 2 is a swarovski quartz sleeve, and the outer cladding layer 3 is an OVD synthesis outsourcing. Layer; The relative refractive index difference between the core layer 1 and the inner cladding layer 2 is Δ1 «0.5%, and the relative refractive index difference between the inner cladding layer 2 and the outer cladding layer 3 is Δ2 «-0.4%.

[0057] The inner wall of the tube of the fluorocarbon quartz sleeve is deposited by a gas phase reaction to form a fluorosilicate layer, which is formed layer by layer until the refractive index conforms to the relative refractive index difference between the core layer 1 and the inner cladding 2.

[0058] The inner layer 2 has a terrible fluorine concentration of 600 ppm.

The diameter of the core layer 1 is 7 μm, and the sum of the diameters of the outer cladding layer 3 and the inner cladding layer 2 is 125 μm.

[0060] The material viscosities of the core layer 1 and the inner cladding layer 2 have a ratio in the range of high temperature 1000 ° C of 1.2.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, and any person skilled in the art within the technical scope disclosed by the present invention, according to the present invention Equivalent replacements or modifications of the technical solutions and their inventive concepts are intended to be included within the scope of the present invention.

Claims

Claim

An ultra-low loss optical fiber, comprising: a core layer, an inner cladding layer and an outer cladding layer which are sequentially coated, wherein the core layer is a pure silicon rod with a miscellaneous alkali metal ion, and the alkali metal in the core layer is cumbersome The ion concentration is from 200 ppm to 500 ppm, the inner cladding is a fluorocarbon quartz sleeve, and the outer cladding is an OVD synthetic outer cladding; the relative refractive index difference between the core layer and the inner cladding is Δ1 « 0.4% - 0.6%, The relative refractive index difference between the inner cladding and the outer cladding is Δ2«-0.3%--0.4%.

The ultra-low loss optical fiber according to claim 1, wherein: the inner wall of the tube of the fluorocarbon quartz sleeve is deposited by a gas phase reaction to form a fluorosilicate layer, which is formed layer by layer until the refractive index conforms to the core layer and the The relative refractive index difference of the inner cladding is described.

An ultra low loss optical fiber according to claim 1, wherein: said inner cladding has a terrific fluorine concentration of from 500 ppm to 800 ppm.

An ultra low loss optical fiber according to claim 1, wherein: said core layer has a diameter of 7 μm to 8 μm, and a sum of diameters of said outer cladding layer and said inner cladding layer is 124.5 μm to 12 5.5 μm.

An ultra low loss optical fiber according to claim 1, wherein a ratio of a material viscosity of said core layer to said inner cladding at a high temperature of 1000 ° C is in the range of 1-1.4.

An ultra low loss optical fiber according to claim 1, wherein: said ultra low loss fiber has an attenuation value of ≤ 0.158 db/km at a wavelength of 1550 nm and a fading value of ≤ 0.28 db/km at a wavelength of 1383 nm.

The ultra-low loss optical fiber according to claim 1, wherein: the cut-off wavelength of the ultra-low loss fiber after cable-forming is ≤ 1490 nm, and the mode field diameter at a wavelength of 1550 nm is ≤ 12. 5 μη.

A method for preparing an ultra-low loss optical fiber, comprising the following steps: Step 1: depositing and dissolving an alkali metal by an axial vapor deposition method to obtain a loose body; Step 2, taking out the loose body to a sintering furnace for dehydration sintering, sintering During the process, alkali metal ions diffuse in the core layer, thereby obtaining a miscellaneous and uniform core rod;

Step 3, matching the fluorocarbon quartz sleeve as an inner cladding on the outside of the mandrel, melting and extending To extend the mandrel;

Step four, forming a preform after adding an outer layer on the outside of the extended mandrel;

In step five, the preform is subjected to wire drawing.

[Claim 9] The method for preparing an ultra-low loss optical fiber according to claim 8, wherein the step 1 specifically includes the following steps:

Sl, the alkali metal salt is placed in the heating cabinet below the deposition tank, and the heating cabinet starts to heat, maintaining the vapor pressure higher than 0.1 kPa, and the average heating rate is 10 ° C/min until the internal temperature exceeds 900 ° C to form alkali metal vapor. Oxygen enters the heating cabinet from the side inlet of the heating cabinet, and mixes with the formed alkali metal vapor to form a mixed gas, and then enters the outlet pipe from the side outlet of the heating cabinet; S2, the sedimentation tank runs in a normal deposition process to form a loose body;

S3, when the first burner in the deposition tank starts to spray the raw material gas including silicon tetrachloride, oxygen, and hydrogen, the alkali metal vapor valve is opened to adjust the gas outlet speed of the mixed gas in the second burner, wherein the first burner and the second burner The spray point of the burner is aligned with the central axis of the loose body, and the alkali metal can enter the entire loose body section as the loose body remains rotated.

At S4, the normal deposition process begins and the alkali metal vapor valve is closed near completion.

[Claim 10] The deposition apparatus of the ultra low loss optical fiber manufacturing method according to claim 9, comprising: a deposition tank, and a heating cabinet for placing an alkali metal salt under the deposition tank The heating cabinet is provided with an air inlet on one side and an air outlet on the other side, and an alkali metal steam valve is arranged on the air outlet; the same side of the deposition tank is respectively provided at the same height. a first torch for injecting a material gas and a second torch for jetting a mixed gas, the gas outlet being in communication with the second torch through an air outlet duct.