CN1800889A - Single mode optical fiber, method of manufacturing the same, and apparatus for manufacturing the same - Google Patents

Single mode optical fiber, method of manufacturing the same, and apparatus for manufacturing the same Download PDF

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CN1800889A
CN1800889A CNA2005101295970A CN200510129597A CN1800889A CN 1800889 A CN1800889 A CN 1800889A CN A2005101295970 A CNA2005101295970 A CN A2005101295970A CN 200510129597 A CN200510129597 A CN 200510129597A CN 1800889 A CN1800889 A CN 1800889A
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spin
density
hydrogen
mode fiber
optical fiber
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CN100357770C (en
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森平英也
久留须一彦
井上喜博
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Furukawa Electric Co Ltd
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Furukawa Electric Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C03B37/02718—Thermal treatment of the fibre during the drawing process, e.g. cooling
    • C03B37/02727—Annealing or re-heating
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/029—Furnaces therefor
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2205/00—Fibre drawing or extruding details
    • C03B2205/56—Annealing or re-heating the drawn fibre prior to coating
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2205/00—Fibre drawing or extruding details
    • C03B2205/60—Optical fibre draw furnaces
    • C03B2205/82—Means for sealing the fibre exit or lower end of the furnace
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2205/00—Fibre drawing or extruding details
    • C03B2205/60—Optical fibre draw furnaces
    • C03B2205/82—Means for sealing the fibre exit or lower end of the furnace
    • C03B2205/83—Means for sealing the fibre exit or lower end of the furnace using gas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57—Improving the yield, e-g- reduction of reject rates

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Glass Compositions (AREA)

Abstract

In a single mode optical fiber formed of a silica-based glass and including a glass part having a central core (11) and a cladding region (12), the density of non bridging oxygen hole center in the glass part is not higher than 1.0 x 10<14> spins/g in terms of the spin density measured by an electron spin resonance method.

Description

The manufacture method of single-mode fiber, single-mode fiber and be used to make the equipment of single-mode fiber
The application number that the application submitted on May 29th, 2002 is 02121746.7, denomination of invention is divided an application for the patent application of " manufacture method of single-mode fiber, single-mode fiber and be used to make the equipment of single-mode fiber ".
Technical field
The present invention relates to a kind of method and apparatus that is used for the silica based single-mode fiber of light transmission and is used to make single-mode fiber.
Background technology
In recent years, carry out fully research, increased the transmission quantity in the light transmission of the optical fiber that use made by silica-based glass.
In order to increase the transmission quantity in the light transmission, the optical fiber of carrying out light transmission must carry out single mode transport under employed wavelength, because if propagate a plurality of patterns in optical fiber, then the group velocity difference in the propagating mode can produce modal dispersion inevitably, thereby reduces the quality of signal waveform.
Thereby ascribe near use has zero-dispersion wavelength 1.3 mum wavelengths single-mode fiber (SMF) to.Because this type optical fiber has zero-dispersion wavelength near 1.3 mum wavelengths, thus might realize that transmission range surpasses 100km and near 1.3 mum wavelengths transmission quantity be the light transmission of hundreds of Mbps.
On the other hand, need to use about 1.55 mum wavelengths to carry out light transmission, because near above-mentioned wavelength, the loss of optical fiber shows as minimum.At this situation, developed near the dispersion shift type single-mode fiber (DSF) that 1.55 mum wavelengths, has zero-dispersion wavelength.This dispersion shift type single-mode fiber makes it to be implemented near the transmission quantity that has several Gbps 1.55 mum wavelengths.And,,, brought increasing rapidly of transmission range so be accompanied by the increase of transmission quantity because this wavelength band is the gain of EDFA band.
And, in recent years,, carried out a large amount of research and development of wavelength-division multiplex (WDM) light transmission in order to increase transmission quantity.About this point, the optical fiber that is applicable to the WDM light transmission has been carried out sufficient research.
Optical fiber for as the WDM light transmission in order to prevent four-wave mixing, requires not exist in the employed wavelength band zero-dispersion wavelength.And in order to realize the WDM optical transmission system, requirement is not created in the wave form distortion of the transmitting optical signal that can not be repaired in relay point and the optical pickup apparatus usually.In order to meet this requirement, the non-linear phenomena that allegedly suppresses optical transmission line and produced and to suppress the accumulation chromatic dispersion be effective.In addition, if in wavelength of optical signal, there is dispersion differences, then cause wave form distortion amount difference for each wavelength.Thereby, must reduce the dispersion slope in the optical transmission line as much as possible.
Developed the dispersion shift type optical fiber (NZDSF) that in employed wavelength band, does not have zero chromatic dispersion that satisfies above-mentioned requirements.Four-wave mixing takes place hardly, and NZDSF's is non-linear enough little in NZDSF.Therefore, NZDSF has obtained promptly adopting and propagating widely.
And, in many situations of WDM optical transmission system, used by polytype optical fiber is combined, be zero optical transmission line for preparing substantially so that make total dispersion value and dispersion slope.The known optical fiber that is used for this purpose comprises, for example dispersion compensating fiber (DCF) and dispersion slope compensated optical fiber (DSCF).
In addition, also study the WDM optical transmission system that uses Raman to amplify in recent years, and in the WDM light transmission, also carried out utilizing near the research of the wavelength region may of wavelength non-1.3 μ m and the 1.55 μ m.
Interior hydrogen molecule of optical fiber and the phenomenon that the fiber transmission attenuation that combining of fault of construction caused increases are one of phenomenons that hinders above-mentioned light transmission.Be known in the art,, cause the increase of loss near 1.24 mum wavelengths, near 1.38 mum wavelengths and at the absorption peak that long wavelength's one side is more produced.
Below this phenomenon will be described.Generally in optical fiber, there is the paramagnetic defective.In these paramagnetic defectives, it is said that non-bridge joint oxygen vacancies center (NBOHC) and peroxy radical (POR) influence transport property, exactly, influence the long-time stability of loss.
Above-mentioned NBOHC is a kind of paramagnetic defective material, make with four oxygen atoms that a silicon atom combines in one have an azygous electronics, this unpaired electron for the not contribution that combines of another atom, shown in Figure 1A.On the other hand, above-mentioned POR is a kind of paramagnetic defective material, make with four oxygen atoms that a silicon atom combines in one with another have unpaired electron to not another oxygen atom combination of contribution that combines of another atom, shown in Figure 1B.
Exactly, if hydrogen is diffused in the optical fiber, then the hydrogen molecule that is spread combines with these paramagnetic defectives, thereby is created in the former sub-portfolio that produces absorption peak in the transmission wavelength band.As a result, increased loss.
Exactly, in the situation of using the Raman amplification system, the short about 100nm of the light that the wavelength ratio of pump light is exaggerated.For example, amplify in Raman system and utilized near so-called " the S-band " the 1500nm beyond the gain wavelength band in the flashlight amplification system of employing Er-doped fiber (EDF), the pumping light wavelength becomes 1,400nm.Because above-mentioned 1, the 400nm wavelength is included in so-called " OH absorption " wavelength region may in the scope between 1385nm and the 1410nm of being in, this has caused the problem that pump light is attenuated in the bigger situation of OH absorption loss, causes obtaining required Raman gain.
In addition, when being diffused into hydrogen molecule in the optical fiber,, will produce trouble if there are a large amount of above-mentioned NBOHC in the zone in mode field diameter (MFD zone).Specifically because the reaction of NBOHC and hydrogen molecule consequently forms the OH base, so OH absorption loss increase simultaneously, thereby greatly reduced the reliability of system.The current this recruitment of in any international standard, all not mentioning OH absorption loss.But, it is said that the desired value of this recruitment is 0.05dB/km in the OH absorption loss.
In U.S. Patent No. 6,131, disclosed an example of optical fiber in 415, wherein consider resistance to hydrogen, be used for suppressing the phenomenon that loss noted earlier increases.Wherein disclose in order to reduce the loss of 1385nm wavelength, reduce pH, thereby might on the whole wavelength coverage of 1200nm to 1600nm, realize light transmission.
And, in U.S. Patent No. 5,838,866 and United States Patent (USP) 6,128,928 in disclosed other example of optical fiber, wherein considered inhibition to hydrogen.It has disclosed, and the germanium that will not increase the amount of refractive index basically adds and the inner cladding zone of the adjacent setting of core, so that improve the inhibiting effect to hydrogen.
But, any one in these US Patent specification all do not mentioned at all, for example, in the optical fiber such as the paramagnetic density of defects of NBOHC or POR, thereby the limit of the paramagnetic density of defects of not knowing in the optical fiber to be allowed etc.
In addition, for example in the open No.2001-114526 of Japanese Patent Laid-Open Publication No.2001-192228 and Jap.P., disclosed and by improving the relevant prior art of technology that method for drawing optical fibers reduces the initial loss of optical fiber or keeps physical strength.
Summary of the invention
One object of the present invention is to provide a kind of anti-hydrogen characteristic fabulous, the optical fiber that long-term reliability is higher.
Another object of the present invention is to provide the optical fiber manufacturing method that a kind of anti-hydrogen characteristic is fabulous, long-term reliability is higher.
Another purpose of the present invention is to provide a kind of device, is used to make the optical fiber that anti-hydrogen characteristic is fabulous, long-term reliability is higher.
According to a first aspect of the invention, a kind of single-mode fiber that is formed by silica-based glass is provided, comprise a glass workpiece of being made up of an intermediate core and a cladding regions, wherein the density as the non-bridge joint oxygen vacancies center in the glass workpiece of the spin density value that is recorded by the electron spin resonance method is not higher than 1.0 * 10 14Spin/gram.
According to a second aspect of the invention, a kind of single-mode fiber that is formed by silica-based glass is provided, comprise that one has the glass workpiece of an intermediate core and a cladding regions, at least a element that wherein will select from the group of being made up of Ge and F adds in the glass workpiece, this glass workpiece has the external diameter of about 125 μ m, and be included in the density at the non-bridge joint oxygen vacancies center in the MFD zone, be lower than the density at the non-bridge joint oxygen vacancies center that is included in the cladding regions that is arranged in the MFD region exterior.
According to a third aspect of the present invention, a kind of single-mode fiber that is formed by silica-based glass is provided, comprise a glass workpiece of forming by an intermediate core and a cladding regions, wherein at least a element that will select from the group of being made up of Ge and F adds in this glass workpiece, this glass workpiece has the external diameter of about 125 μ m, and it is resulting by the deviation of measuring between Rayleigh scattering line and the Raman scattering line, defect line by expression three joint glass ring structures is not higher than 1,200 ℃ with the resulting fictive temperature of ratio that expression four saves the defect line of glass ring structures.
The 4th aspect according to the present invention, a kind of method of making single-mode fiber is provided, this single-mode fiber is formed by silica-based glass, and comprise that one has the glass workpiece of an intermediate core and a cladding regions, wherein at least a element that will select from the group of being made up of Ge and F adds in this glass workpiece, this glass workpiece has the external diameter of about 125 μ m, and this method comprises heating optical fiber preform, so that the melting fiber prefabricated rods; Preform drawing optical fiber from fusion; And with 1,000 to 3,000 ℃/second cooling velocity, the meniscus that is reduced to 5% prefabricated rods diameter from diameter from 90% prefabricated rods diameter partly, the optical fiber that the preform of fusion is cooled to be drawn has the part of 1,200 ℃ of temperature continuously.
In addition, according to a fifth aspect of the present invention, provide a kind of equipment that is used to make optical fiber, comprise that one is used for the heating furnace of heating optical fiber preform, this heating furnace comprises a primary heater; With a mechanism that is used for the preform drawing optical fiber that in heating furnace, melts, wherein will have the length L that satisfies inequality given below 1Following right cylinder be arranged to contact with bottom one side of heating furnace, and cooling optical fibers continuously in following right cylinder, the diameter of the preform of fusing is reduced to the meniscus part of institute's drawing optical fiber of 5% prefabricated rods diameter in the feasible wherein fibre-optical drawing stove from 90% prefabricated rods diameter, have the length that is not less than " A * 5 ", wherein A represents the diameter (mm) of prefabricated rods:
L 1(mm)＞B×B/300
Wherein B represents the draw rate (meter/minute) of optical fiber.
In description subsequently, will provide more purpose of the present invention and advantage, part purpose and advantage obviously can be found out from describe, perhaps may be to understand by the practice of the present invention.By in particular the following device and combination, can realize and obtain objects and advantages of the present invention.
Description of drawings
That adopted and constitute the accompanying drawing of an instructions part, the present invention's most preferred embodiment known today has been described, with the detailed description of general description that provides previously and most preferred embodiment given below, be used to explain principle of the present invention.
Figure 1A, 1B and 1C represent NBOHC respectively, POR and Si (D)-E ' belongs to the paramagnetic defective of optical fiber;
Fig. 2 A represents the example of a plurality of index distribution of single-mode fiber according to an embodiment of the invention to 2D;
Fig. 3 A and 3B represent other example of the index distribution of single-mode fiber according to an embodiment of the invention;
Fig. 4 A, 4B and 4C represent to use the cathode luminescence method, and respectively to sample SM1, near the luminous intensity in the cross section of optic fibre that SM2 and NZ1 measure the 650nm wavelength distributes;
Fig. 5 absorbs the curve that concerns between the recruitment for the measurement result and the 1.38 μ m OH of place of near the NBOHC density expression MFD;
Fig. 6 is exposed to before the hydrogen curve that concerns between cl concn and the 1.38 μ m OH of the place absorption losss in the cladding regions for being illustrated in;
Fig. 7 represents to be exposed to the curve that concerns between the cl concn and OH loss recruitment in the cladding regions that hydrogen causes;
The curve of Fig. 8 for concerning between expression fictive temperature Tf and the 1.38 μ m OH of the place absorption recruitment;
Fig. 9 schematically shows fibre-optical drawing equipment according to another embodiment of the present invention; And
Figure 10 schematically shows the bottom that how to allow gas to flow into fibre-optical drawing equipment shown in Figure 9.
Embodiment
Below a plurality of embodiment that present invention will be described in more detail.
According to the single-mode fiber of first embodiment of the invention, it is characterized in that by being that the density at the non-bridge joint oxygen vacancies center (NBOHC) of unit is not higher than 1.0 * 10 with the spin density that records by the electron spin resonance method 14Spin/gram.The lower limit of spin density is not specially limited, and is typically about 1.0 * 10 11Spin/gram.
If the density of NBOHC has surpassed 1.0 * 10 14Spin/gram in the time of in hydrogen molecule diffusion and injection fibre, has increased near the loss 1.52 mum wavelengths.
In single-mode fiber, require by being that the density of paramagnetic defective Si (D)-E ' in the glass workpiece of unit is not less than 1.0 * 10 with the spin density that records by the electron spin resonance method according to first embodiment of the invention 12Spin/gram.If the density of Si (D)-E ' is not less than 1.0 * 10 12Spin/gram might further prevent near the increase of the loss of 1.38 mum wavelengths.
In the present invention, as mentioned above, the spin density value that records by electron spin resonance (ESR) method limit exist in the optical fiber such as NBOHC or Si (D)-paramagnetic density of defects such as E '.
Above-mentioned Si (D)-E ' two oxygen atoms of expression and the paramagnetic defective material that D atom combines with a silicon atom, and shown in Fig. 1 C, silicon atom have one to not having the unpaired electron contributed with combining of another atom.
In single-mode fiber according to first embodiment of the invention, near in the xsect of the glass workpiece that might measure with the cathode luminescence method 650nm wavelength luminous intensity, has certain distribution, make that intensity is the strongest near the outside of intermediate core and excircle part the annular region, intensity outwards reduces gradually.If define luminous intensity as mentioned above, comprising hydrogen under the effect of interior atomic link, might prevent near the increase of the loss of 1.52 mum wavelengths.
In single-mode fiber, germanium may be added in the intermediate core according to first embodiment of the invention.And, fluorine might be added in the annular region of adjacent glass part intermediate core setting.In addition, might make cl concn in the cladding regions be higher than fluorine concentration in the intermediate core.
The effect that reduces in view of the glass structure defective that can increase fiber transmission attenuation need add intermediate core with germanium, and fluorine is added the annular region that adjacent intermediate core is provided with, and makes fluorine concentration in the cladding regions be higher than cl concn in the intermediate core.
Can be by deuterium be diffused in the glass workpiece, so that reduce the spin density of NBOHC, thereby increase the spin density of peroxy radical, and make foregoing single-mode fiber according to first embodiment of the invention.If deuterium is spread as anti-hydrogen processing, reduce the spin density of NBOHC, increase the spin density of peroxy radical, thereby make it to obtain the aforesaid single-mode fiber that does not have to spread the loss increase that causes owing to hydrogen.
Single-mode fiber according to second embodiment of the invention is characterized in that, the density of the NBOHC that is comprised in the MFD zone of glass workpiece is lower than the density of the NBOHC that is comprised in the cladding regions of outside, MFD zone.By reducing the density of NBOHC in the zone that light passed through as previously mentioned, may improve the anti-hydrogen characteristic of optical fiber.
In single-mode fiber according to second embodiment of the invention, require by with the spin density value that records by the electron spin resonance method being unit, be that the density of the NBOHC that comprised in the zone of 25 μ m is not higher than 1.0 * 10 apart from the glass workpiece radius centered 13Spin/gram.The lower limit of spin density is not specially limited, and is typically about 1.0 * 10 11Spin/gram.
If the density of NBOHC surpasses 1.0 * 10 13Spin/gram is then spread and during injection fibre when hydrogen molecule, has increased near the loss 1.52 mum wavelengths.
In single-mode fiber, require the cl concn in the cladding regions to be not less than 1,000ppm according to second embodiment of the invention.The upper limit of cl concn is not specially limited, and is typically about 10,000ppm.
In single-mode fiber, require by being that the density of the paramagnetic defective Si-E ' that comprised in the glass workpiece of unit is not less than 5 * 10 with the spin density that records by the electron spin resonance method according to second embodiment of the invention 13Spin/gram.The upper limit of spin density is not specially limited, and is typically about 1.0 * 10 15Spin/gram.
If limit the density of the paramagnetic defective Si-E ' that is comprised in cl concn in the cladding regions and the glass workpiece as mentioned above, then before being exposed to hydrogen, might reduce by the OH absorption loss of 1.38 μ m, so that reduce to be exposed to the increase of the OH absorption loss of the 1.38 μ m that hydrogen causes.
In single-mode fiber according to second embodiment of the invention, require the loss after being exposed to 1 atmospheric hydrogen at room temperature to increase, be different from by the increase that is diffused into the loss that hydrogen molecule caused in the glass workpiece, it is not more than 0.1dB/km at 1.38 μ m in the wavelength region may of 1.42 μ m.
Single-mode fiber according to third embodiment of the invention, it is characterized in that by allowing transmission light to incide in the middle section in MFD zone of glass workpiece, and it is resulting by the deviation of measuring between Rayleigh scattering line and the Raman scattering line, the fictive temperature that is obtained with the ratio of the defect line of expression four-membered ring structure by the defect line of representing the three-membered ring structure is not higher than 1,200 ℃.The lower limit of fictive temperature is not specially limited, and is typically about 1,000 ℃.Be set to 1,200 ℃ or lower by fictive temperature, can reduce to be exposed to the recruitment of the OH absorption loss of the 1.38 μ m that hydrogen causes.
In single-mode fiber according to third embodiment of the invention, require the loss after being exposed to 1 atmospheric hydrogen at room temperature to increase, be different from by the increase that is diffused into the loss that hydrogen molecule caused in the glass workpiece, it is not more than 0.05dB/km at 1.38 μ m in the wavelength coverage of 1.42 μ m.
Manufacture method according to the single-mode fiber of fourth embodiment of the invention is characterized in that this method comprises the cooling velocity with 1,000 to 3,000 ℃/second, cools off the step from the meniscus part to the zone between 1,200 ℃ of part of institute's drawing optical fiber continuously.By cooling velocity with previously defined regulation, meniscus part and following various piece are cooled to predetermined temperature continuously, can improve the anti-hydrogen of optical fiber.
In the manufacture method according to the single-mode fiber of fourth embodiment of the invention, requiring preform is the silica-based glass carbon black that obtains by flame hydrolysis process, and under the condition of anaerobic basically with the carbon black sintering.
A kind of device that is used to make single-mode fiber according to fifth embodiment of the invention is characterized in that, with length L 1Satisfying the following right cylinder of relation of the regulation of fibre-optical drawing speed is arranged to contact with bottom one side of heating furnace, and cooling optical fibers continuously in this time right cylinder, make the length of meniscus part of institute's drawing optical fiber prefabricated rods of melting in the fibre-optical drawing stove be not less than " A * 5 ", wherein A represents the diameter (mm) of prefabricated rods.
By adopting above-mentioned specific device structure, may realize being included in cooling step according in the fourth embodiment of the invention method.
At the device that is used for making single-mode fiber,, be used for the optical fiber of pulling out in heating furnace is heated in the right cylinder secondary heater being set down according to fifth embodiment of the invention.Require the length L of secondary heater 2Given inequality below satisfying:
L 2＞B×C/200
Wherein B represents the diameter (mm) of preform, and C represents the draw rate (meter/minute) of optical fiber.
Also require the distance L between the top of the top of primary heater and heating furnace 3Given inequality below satisfying, the distance L between the top of primary heater and the top of heating furnace 4Given inequality below satisfying:
L 3＞B×C/200
L 4＞B×C/200
Wherein B represents the diameter (mm) of preform, and C represents the draw rate (meter/minute) of optical fiber.
By the way, the single-mode fiber among the present invention is illustrated in and comprises above-mentioned SMF, and DSF, the employed wavelength band of NZDSF and DCF can carry out the optical fiber of single mode operation down.
One embodiment of the present of invention are described below with reference to accompanying drawings.
Fig. 2 A to 2D represents a plurality of examples according to the index distribution of the single-mode fiber of first embodiment of the invention.By multiple element is added in the quartz, can obtain required index distribution.Wherein may add Ge, refractive index is increased to the value higher than the refractive index of pure quartz, may add F, reduce refractive index.Incidentally, also may add Ge and F simultaneously, to obtain required index distribution.
In the index distribution shown in Fig. 2 A, the refractive index of the refractive index ratio cladding regions 12 of intermediate core 11 is big.Having optical fiber that specific refractive index distributes comprises by the cladding regions 12 of mixing intermediate core 11 that the Ge quartz constitutes and being formed by pure quartz basically.And the cl concn in the cladding regions 12 is than the cl concn height in the core 11.Or rather, the cl concn in the intermediate core 11 is set to 700 to 1,300ppm, and the cl concn that is arranged in the cladding regions 12 of core 11 outsides is set to 1,500 to 3,000ppm.
In the index distribution shown in Fig. 2 B, the refractive index height of the refractive index ratio cladding regions 23 of intermediate core 21, the refractive index of the refractive index ratio cladding regions 23 of annular region 22 is low.Should be noted that having the optical fiber that specific refractive index distributes comprises the intermediate core 21 that is formed by the quartz that mixes Ge, annular region 22 that forms by the quartz that mixes a small amount of F and the cladding regions 23 that forms by pure quartz basically.Cl concn in annular region 22 and the cladding regions 23 is all than the cl concn height in the intermediate core 21.Exactly, the cl concn in the intermediate core 21 is set to 700 to 1,300ppm, and annular region 22 and the cl concn that is arranged in the cladding regions 23 of intermediate core 21 outsides are set to 1,500 to 3,000ppm.
In the index distribution shown in Fig. 2 C, the refractive index of the intermediate core 31 and second annular region 33 all is higher than the refractive index of cladding regions 34.Have optical fiber that specific refractive index distributes and comprise by mixing the quartzy intermediate core 31 that forms of Ge, by mixing quartzy first annular region 32 that forms of F, by the cladding regions 34 of mixing second annular region 33 that the Ge quartz forms and forming by pure quartz basically.
Fig. 2 C represents that the refractive index of the refractive index ratio cladding regions 34 of first annular region 32 is little.But, definitely do not require the refractive index of refractive index ratio cladding regions 34 of first annular region 32 low.Refractive index that might first annular region 32 is substantially equal to the refractive index of cladding regions 34, as shown in Figure 3A.
In the index distribution shown in Fig. 2 D, between intermediate core 41 and cladding regions 45, insert first annular region, 42, the second annular regions 43 and the 3rd annular region 44.The refractive index of the intermediate core 41 and second annular region 43 all is higher than the refractive index of cladding regions 45, and the refractive index of first annular region 42 and the 3rd annular region 44 all is lower than the refractive index of cladding regions 45.
Fig. 2 D represents that the refractive index of first annular region 42 is lower than the refractive index of cladding regions 45.But, do not require the refractive index of first annular region 42 to be lower than the refractive index of covering 45 utterly.The refractive index of first annular region 42 might be substantially equal to the refractive index of cladding regions 45.
Incidentally, Fig. 2 A that mentions in the above is in 2D, and the external diameter of single-mode fiber is in the scope of 125 μ m ± 3 μ m.And intermediate core 11 and 21 external diameter are 7.5 to 9.5 μ m, and intermediate core 31 and 41 external diameter are 3 to 5 μ m.The external diameter of annular region 22 is that 3 to 6 times of intermediate core 21 external diameters are such big.The external diameter of annular region 32 is that 1.5 times to 3.5 times of core 31 external diameters are such big, and the external diameter of annular region 33 is 1.2 times to 2.5 times such big of external diameter of annular region 32.In addition, the external diameter of annular region 42 is that 1.5 to 3.5 times of intermediate core 41 external diameters are such big, and the external diameter of annular region 43 is that 1.2 to 2.5 times of annular region 42 external diameters are such big.In addition, the external diameter of annular region 44 is 1.02 to 2 times such big of annular region 43 external diameters.
In the single-mode fiber with the index distribution shown in Fig. 2 A to 2D and Fig. 3 A and the 3B, so-called " MFD " generally is in, and for example 4 μ m are in 12 mu m ranges, but according to desired optic fibre characteristic, MFD there are differences.Usually, the scope that light is propagated is generally 2 to 3 times of MFD scope, is in the common optical fiber of about 125 μ m at the diameter of glass workpiece, and thinking influences transport property, and especially the scope of loss is the diameter that is not more than about 50 μ m.
Then,, study the increase of hydrogen loss and the increase of OH loss, and carry out ESR and measure having the example of the single-mode fiber of index distribution shown in Fig. 2 A to 2C.Table 1 is expressed the result.Incidentally, included empty spin density shows that spin density is 10 in the table 1 12Magnitude is not higher than the probe value of ESR signal.
Table 1
Sample number into spectrum Kind Be used for the processing of anti-hydrogen 1.52 the increase of the absorption of μ m 1.38 the increase of the absorption of μ m Si (D)-E ' (spin/gram) NBOHC (spin/gram) FOR (spin/gram)
SM1 SM1D SM2 SM2D SM3 SM4 SM5 SM6 SM7 SM8 NZ1 NZID SMF SMF SMF SMF SMF SMF SMF SMF SMF SMF ZDF NZDSF × ○ × ○ × × × × × × × ○ Increasing not increase does not have Increasing not increase not increase not increase does not have - 1.9E+13 - 1.8E+13 - - - - - - - 2.2E+13 1.1E+14 - 1.2E+14 - 7.9E+13 7.3E+13 5.9E+13 9.2E+13 - - 3.4E+13 - - 4.9E+13 - 2.3E+13 - - - - - - - 2.7E+13
Annotate: blank spin density (spin/gram) shows that spin density is lower than 1.0E+12, therefore can not be detected.
The optical fiber that sample SM1 shown in the table 1 has index distribution shown in Fig. 2 A to the SM6 representative.The optical fiber that sample SM7 and SM8 representative have index distribution shown in Fig. 2 B.In addition, sample NZ1 and NZ2 represent the optical fiber with index distribution shown in Fig. 2 C.
And the processing that is used for anti-hydrogen shown in the table 1 shows, sample is remained on the stipulated time in the deuterium atmosphere, so that deuterium molecule is diffused in the optical fiber.Symbol in these row " zero " shows this sample through being used for the processing of anti-hydrogen, and symbol " * " shows not apply the processing that is used for anti-hydrogen to this sample.
The row that in table 1, also comprise " increase that 1.52 μ m absorb ".The increase from the loss of Si-H key is shown in this tabulation, promptly so-called " increase of hydrogen loss "." increase " that demonstrates in the table 1 shows when sample and at room temperature is exposed to the deuterium atmosphere during stipulated time, identifies the increase that 1.52 μ m absorb, and mark " does not have " to show and do not recognize the increase that 1.52 μ m absorb.
The row that in table 1, also comprise " increase that 1.38 μ m absorb ".The increase from the loss of Si-OH key is shown in this tabulation, promptly so-called " increase of OH loss ".Shown " increase " in the table 1 shows when sample at room temperature to be exposed to the hydrogen atmosphere during stipulated time, identifies the increase that 1.52 μ m absorb, and " not having " of demonstration shows and do not recognize the increase that 1.52 μ m absorb.
The result who measures for the ESR of each sample SMF in the table 1 is as follows.
Exactly, in sample SM1, recognize the increase of hydrogen loss and the increase of OH loss, and the spin density that detects the NBOHC defective is 1 * 10 14Spin/gram reaches 10 14Magnitude.
Handle by in optical fiber, applying the anti-hydrogen identical with sample SM1, and preparation sample SM1D.In sample SM1D, do not recognize the increase of any hydrogen loss and the increase of OH loss basically, and do not detect the ESR signal of NBOHC defective.In addition, the spin density of discovery POR defective is 4.9 * 10 13Spin/gram.In addition, in sample SM1D, detect the signal of the paramagnetic defective " Si (D)-E ' " that is combined with deuterium.
Sample SM2 with have be used for the SM2D that anti-hydrogen handle identical and show the result identical with sample SM1D respectively with sample SM1 with imposing on sample SM2.Exactly, in sample SM2, identify the increase of hydrogen loss and the increase of OH loss, and find that the spin density of NBOHC defective is 1.2 * 10 14Spin/gram.On the other hand, in sample SM2D, do not recognize the increase of any hydrogen loss and the increase of OH loss basically.In addition, the spin density of discovery POR defective is 2.3 * 10 13Spin/gram.In addition, in sample SM2D, detect " Si (D)-E ' ".
In sample SM3 to SM6, identify the increase of OH loss, but do not identify the increase of hydrogen loss.And the spin density of the NBOHC defective of these samples is 10 13Magnitude.In addition, do not detect the signal of expression POR defective.
In sample SM7 and SM8, do not identify the increase of any hydrogen loss and the increase of OH loss, and do not detect the signal of expression NBOHC defective and the signal of expression POR defective.
The result that above-mentioned ESR measures shows, if the spin density of NBOHC defective increases to 10 14Magnitude, can identify the increase of hydrogen loss and the increase of OH loss.
Also show, when the spin density of NBOHC defective is 10 13During magnitude, can identify the increase of OH loss, but, not recognize the increase of hydrogen loss.
In addition, when the spin density of NBOHC defective not when detected, be 10 12Or littler magnitude, can not identify the increase of any hydrogen loss and the increase of OH loss.
Apply the processing that is used for anti-hydrogen by the diffusion that utilizes deuterium molecule, the phenomenon that can improve anti-hydrogen characteristic itself is well known in the art.But, the optical fiber of the special processing that applies from having can detect the signal of expression Si (D)-E ' defective, thereby shows the resistance to hydrogen.
Present measurement result with the NZDSF shown in the description list 1.
Sample NZ1 representative has 75 μ m 2Aeff and the optical fiber that in 1.55 μ m band, has the negative dispersion value of about several ps/nm/km.The spin density of NBOHC defective is 3.4 * 10 13Spin/gram promptly is in 10 13Magnitude, and recognize the increase of OH loss, but do not recognize the increase of hydrogen loss.In addition, find the situation for SMF described above, the anti-hydrogen characteristic of sample NZ1 is identical to SM6 with sample SM3.
In the sample NZ1D that is applied in anti-hydrogen processing, do not detect the ESR signal of expression NBOHC defective, find that the spin density of POR defective is 2.7 * 10 13Spin/gram, the result does not recognize any one in the increase of the increase of hydrogen loss and OH loss.In addition, sample SM1D is such as previously mentioned, detects the signal of the paramagnetic defective material " Si (D)-E ' " that is combined with deuterium.
To describe now and use the cathode luminescence method to measure, near the luminous intensity in the cross section of optic fibre 650nm wavelength distributes.
The cathode luminescence method is a kind of analytical approach, when being used for according to electron beam incident on object, and the ultraviolet light that object is launched, visible light or near infrared light wavelength and intensity, analyzing defect kind and its density or stress.Be known in the art, near the light emission the 650nm wavelength is because NBOHC.By using the NBOHC in the described technical research cross section of optic fibre to distribute, Fig. 4 A expresses the result to 4C.
Fig. 4 A given situation below 4C expresses:
(1) Fig. 4 A represents that the luminous intensity of sample SM1 distributes, and sample SM1 is an example with optical fiber of index distribution shown in Fig. 2 A.
From Fig. 4 A obviously as can be seen, the light from sample SM1 emission has the highest intensity in the boundary member between intermediate core 11 and covering 12 (mode field periphery), and in the outside of intermediate core 11, intensity promptly weakens.And a little less than the periphery of the luminous strength ratio intermediate core 11 of the center of intermediate core 11, luminous intensity further weakens in cladding regions 13.
And in the situation of 7.5 μ m to 9.5 μ m, the point of representing high luminous intensity is in 3 μ m in 4.5 mu m ranges apart from distance (radius) R of fiber optic hub, i.e. 3 μ m＜R＜4.5 μ m at the external diameter of intermediate core 11.On the other hand, at the external diameter of intermediate core 11 in the situation of 7.5 μ m to 9.5 μ m, distance for the some outside of R, show the point of 20% distance for the maximum emission intensity of the point of R, apart from being in 5 μ m to 6 mu m ranges of fiber optic hub apart from r, i.e. 5 μ m＜r＜6 μ m.In other words, if surpassed distance apart from the point of fiber optic hub distance R apart from the distance of fiber optic hub, luminous intensity reduces rapidly.
In the optical fiber of above-mentioned sample SM1, as noted, NBOHC concentrates in the mode field periphery.And,, can measure by ESR and survey NBOHC as obviously as can be seen from table 1.Therefore, for the resistance for hydrogen, optical fiber has stayed further improved space.
(2) Fig. 4 B represents that the luminous intensity of sample SM7 distributes, and this sample is an example with optical fiber of index distribution shown in Fig. 2 B.
From Fig. 4 B obviously as can be seen, the light intensity that sends from sample SM7 distributes, and has maximum intensity in the boundary member (mode field periphery) between annular region 22 and annular region 22 and cladding regions 23, compares with the curve of Fig. 4 A, in annular region 22 outsides, intensity weakens lentamente.And a little less than the luminous intensity of the luminous strength ratio mode field periphery in intermediate core 21 central areas, luminous intensity further weakens in cladding regions 23.
And, for annular region 22 with internal diameter described above and external diameter, the point that the performance county goes out high luminous intensity apart from distance (radius) R of fiber optic hub within 4 μ m to 6 mu m ranges, i.e. 4 μ m＜R＜6 μ m.On the other hand, for annular region 22 with internal diameter described above and external diameter, distance for the some external table of R reveal 20% distance be R point maximum emission intensity point apart from fiber optic hub apart from r within 9 μ m to 15 mu m ranges, i.e. 9 μ m＜r＜15 μ m.In other words, if surpass the distance of the point of distance R apart from fiber optic hub apart from the distance of fiber optic hub, luminous intensity weakens gradually.
In the optical fiber of above-mentioned sample SM7, NBOHC does not concentrate in the mode field periphery as mentioned above.And, from table 1 obviously as can be seen, can not detect NBOHC by the ESR measurement.Therefore, there is not the problem of relevant resistance to hydrogen in optical fiber.
(3) Fig. 4 C represents that the luminous intensity of sample NZ1 distributes, and this sample is an example with optical fiber of index distribution shown in Fig. 2 C.
From Fig. 4 C obviously as can be seen, the light intensity that sends from sample NZ1 is stronger the annular region 32 (zone that has low-refraction in MFD) that adds F, in central area that adds Ge and the annular region 33 (zone that in MFD, has high index of refraction) a little less than.And in the cladding regions 34 that adds F and Ge, luminous intensity is the most weak.Be useful on the sample NZ1D that anti-hydrogen is handled for being applied in, also have identical situation.
Should be noted that in the sample SM1D and SM2D that apply anti-hydrogen processing, recognize the luminous of NBOHC, but do not detect NBOHC by ESR.It should be noted, even, in the cathode luminescence method, can observe the luminous of NBOHC because the processing of anti-hydrogen is not detected in the optical fiber of NBOHC by ESR.
Think that the reason of said circumstances is as follows:
(a) the cathode luminescence method is highly sensitive in the sensitivity of ESR.
(b) have the part of unrelieved stress and the part of glass structure fragility in the cathode luminescence method reaction cross section of optic fibre, and ESR can not survey above-mentioned part.
Incidentally, the measurement result that the luminous intensity of expressing in the 4C at Fig. 4 A that obtains with the cathode luminescence method distributes, only represent that luminous intensity distributes relatively in the cross section of optic fibre, be not provided for the indication of the absolute contrast that luminous intensity distributes in the different fiber.By using the numerical value that measurement result obtained that is obtained by the ESR method, the actual specific of carrying out the NBOHC spin density.
From the measurement result of ESR method with the observations of cathode luminescence method, can obtain following conclusion:
(1) increase of the increase of hydrogen loss and OH loss is contained in the problem of relevant resistance to hydrogen.When what obtain with the ESR method is that the density of the NBOHC of unit surpasses 1.0 * 10 with the spin density 14During spin/gram, produce the increase of hydrogen loss and the increase of OH loss.Therefore, in order to obtain there is not the optical fiber that hydrogen loss increases and the OH loss increases, the spin density of NBOHC is not higher than 1.0 * 10 at least 14Spin/gram.
(2) spin density as NBOHC is not higher than 1.0 * 10 14During spin/gram, may produce the increase of OH loss, but not produce the increase of hydrogen loss.On the other hand, the spin density as NBOHC is not higher than 10 12During spin/gram, do not produce any basically about the increase of hydrogen loss and the increase of OH loss.In other words, the condition of the increase that does not produce hydrogen loss that optical fiber is required and the increase of OH loss is that the spin density that is NBOHC is 10 12Spin/gram or littler magnitude.
(3) in the optical fiber that is applied with anti-hydrogen processing, do not detect NBOHC, but detect POR and Si (D)-E '.But, in this case, do not produce the increase of any hydrogen loss and the increase of OH loss.This does not still wherein produce the required condition of optical fiber of the increase of the increase of hydrogen loss and OH loss.
(4) by the cathode luminescence method, the NBOHC that may observe in the cross section of optic fibre distributes.For example, in the SMF that mixes Ge with index distribution shown in Fig. 2 A, light from the NBOHC generation with about 650nm wavelength, has maximum intensity in the borderline region between intermediate core 11 and cladding regions 12, in intermediate core 11 and cladding regions 12, light intensity reduces gradually with the order of being mentioned.
(5) be mixed with micro-F, thereby obtain among the SMF of the periphery of mixing the Ge core of the index distribution shown in Fig. 2 B for example, the light that sends from NBOHC with about 650nm wavelength, in annular region 22, show maximum intensity, annular region 22 is that the F zone is mixed in intermediate core 21 outsides, light intensity outwards reduces gradually from intermediate core 21, makes in the intermediate core 21 and cladding regions 23 of mixing the Ge part, and intensity is weakened with the order of being mentioned.In other words, compare with the optical fiber with index distribution shown in Fig. 2 A, in described optical fiber, NBOHC concentrates on a place, but is dispersed in mode field periphery and its perimeter.
Index distribution shown in Fig. 2 B is better than in anti-hydrogen characteristic and index distribution shown in Fig. 2 A.
(6) in addition, for example have shown in Fig. 2 C in the single-mode fiber of index distribution, promptly form first annular region 32 of mixing F along the excircle of mixing Ge intermediate core 31, excircle along first annular region 32 further forms second annular region 33 of mixing Ge, the light of being launched with about 650nm wavelength, have high strength in annular region 32, light intensity reduces with the order of being mentioned in annular region 32 and cladding regions 34.Incidentally, the same phenomenon of optical fiber generation that has index distribution shown in Fig. 2 D.
Draw thus, the conclusion that provides above (1) is the condition with single-mode fiber absolute demand of gratifying anti-hydrogen characteristic, and conclusion (2) and (3) have constituted desirable condition.And conclusion (4) to (6) is very important as the condition of the conclusion (1) that provides above being used to support to (3).
Single-mode fiber according to second embodiment of the invention will be described now.
As proposing, allegedly in the reduction of anti-hydrogen characteristic, include the improvement of relevant optical fiber anti-hydrogen characteristic, the fault of construction of glass especially comes from the improvement of the fault of construction of oxygen.In fault of construction, (the non-bridge joint oxygen vacancies center: NBOHC) be the well-known paramagnetic defective that can pass through the detection of ESR method of the fault of construction shown in Figure 1A.
When having NBOHC in the optical fiber, if hydrogen molecule is diffused in the glass to produce the OH base, just reaction given below takes place:
≡Si·O·+·H≡Si-O-H
Near the increase of the wavelength OH absorption loss of 1.38 μ m takes place as a result.
If have a large amount of NBOHC at MFD that light passes through or near it, think that then anti-hydrogen characteristic is lowered.At glass have the state of about 125 μ m external diameters and with HF acid attack optical fiber so that diameter is reduced to the state of about 50 μ m, the present inventor has measured the spin density of the NBOHC that comprises in the various optical fiber with the ESR method.
After corroding, external diameter is set at about 50 μ m, in part because the present inventor wishes to understand the defect state (that is, wish not influenced by clad section data) of optical waveguide part, and in part because in view of keep sample in the ESR measuring process, precision is restricted.
Under room temperature, be exposed to 1 atmospheric pressure hydrogen atmosphere so that hydrogen molecule is diffused into fully in the situation in the optical fiber at sample, the present inventor has also studied the recruitment of the absorption loss that 1.52 μ m or 1.38 to 1.42 μ m hydrogen cause, and the relation between the spin density that is recorded by the ESR method.The optical fiber with index distribution shown in Fig. 2 A has been contained in test in this situation, promptly general single-mode fiber.
The state of the loss that result that table 2 expression ESR measures and hydrogen are caused.
Table 2
Numbering 1.52 μ m absorbs 1.38 the increase that μ m absorbs Spin density (spin/gram)
NBOHC
SM9 Absorb 1.36 1.1E+14
SM9E 2.5E+14
SM10 Absorb 0.82 1.2E+1.4
SM10E 9.6E+13
SM11 No 0.19 6.1E+13
SM11E 7.9E+13
SM12 No 0.08 9.5E+12
SM12E 3.4E+12
SM13 No 0.03 1.2E+12
SM13E ND
In table 2, the sample number of additional letter " E ", for example SM9E represents by corroding the sample that external diameter is reduced to about 50 μ m with HF acid.On the other hand, do not corrode and handle sample before, thereby have the external diameter of about 125 μ m with the sample number representative of letter " E ".And the unit of the increase that 1.38 μ m absorb is " dB/km ".
It is said that it is (=combining Si-O-O) because hydrogen molecule and a peroxy radical that 1.52 μ m absorb.But, it will also be appreciated that other reason.Even now, do not have definite theory yet.In this test, will be exposed to hydrogen loss value before and compare with being exposed to hydrogen loss value afterwards, the sample that will identify absorption peak in wavelength is expressed as " absorption ", and the sample that will not identify absorption peak is expressed as " not having ".
By the hydrogen molecule and the formed OH base of the reaction between the NBOHC that are diffused in the optical fiber, caused 1.38 μ m to absorb, in table 2, will be exposed to before the hydrogen and the loss difference that is exposed to after the hydrogen is expressed as recruitment.Incidentally, the NBOHC spin density of " ND " shown in the table 2 shows, is used for measuring and the spin density of the ESR device under measuring condition is not higher than 1.0 * 10 12The detection limit of spin/gram.
According to preparation sample as described below.
Sample SM9: in another process, on core, form a cladding regions by the preparation of VAD method.Porous body is being sintered in the process of plug, allowing middle 1% the oxygen that exists in the atmosphere, so that force to form glass with superelevation oxygen content.
With the fibre-optical drawing equipment shown in following Fig. 8 that mentions, with 1,000 meter/minute fibre-optical drawing speed, and the maximum temperature of fibre-optical drawing stove is set to 2,050 ℃, and the prefabricated rods of 80mm external diameter is carried out fibre-optical drawing.In this case, the length of slow cool down part is 1,500mm, and the length of meniscus is 350mm.
Sample SM10: use the method identical to prepare this sample with preparing sample SM9.But, fibre-optical drawing speed is set to 500 meters/minute, and the maximum temperature of fibre-optical drawing stove is set to 1,950 ℃.In addition, meniscus length is 350mm.
Sample SM11: use the method identical to prepare this sample with sample SM9.But, in making the transparent step of core porous body, there is not oxygen.
Sample SM12: use the method identical to prepare this sample with sample SM10.But, in making the transparent step of core, there is not oxygen.
Sample SM13: use the method identical to prepare prefabricated rods with sample SM12.Fibre-optical drawing speed is set to 500 meters/minute, and the maximum temperature of fibre-optical drawing stove is set to 1,950 ℃.But, the air-flow in the stove is controlled, so that the length of meniscus is increased to 420mm.
The result of sample manufacture process can be summarized as follows:
(1), produces 1.52 μ m and absorb by being exposed to hydrogen if make core porous body transparent treated under the atmosphere of oxygen comprising.On the other hand, if under oxygen free condition, make core porous mass transparent treated, be exposed to hydrogen and do not produce 1.52 μ m absorption.
Test figure meets the universal of the 1.52 μ m absorption of tending to produce in comprising the glass of a large amount of oxygen.Can reasonably be interpreted as, prepare glass, can prevent that 1.52 μ m from absorbing if do not comprise excess of oxygen.
In the following description, focus on the OH absorption of 1.38 mum wavelengths that do not relate to 1.52 μ m absorption.
(2) Fig. 5 is that expression HF corrodes the curve that the OH that records near NBOHC density of MFD and 1.38 mum wavelengths afterwards absorbs the relation between the recruitment.
In the curve of Fig. 5, diamond indicia is represented from the sample (sample SM9 and SM10) of the glass preparation that comprises excess of oxygen.On the other hand, square marks is represented the prepared sample (sample SM11 is to SM13) of glass for preparing down from oxygen free condition.From the curve of Fig. 5 obviously as can be seen, in NBOHC density and be exposed in the relation between the increase of the loss that hydrogen causes, sample has tangible difference each other.Or rather, under the identical situation of NBOHC density, compare the bigger increase that brings loss from the sample of the glass preparation that comprises excess of oxygen with the sample of the glass preparation of making down by oxygen free condition.Can reasonably be interpreted as, peroxy radical and H-H reaction, thus form the OH base, cause the increase of loss in the situation of the prefabricated rods that comprises excess of oxygen.
Sample SM11 will be described now to SM13.
Be known in the art, the amount of the remaining structure defective in the optical fiber depends on the cooling condition in the fibre-optical drawing step.Usually, if cooling velocity is low, then remains defect level and reduce.Can be interpreted as reasonably that because following given, by changing cooling condition, preparation sample SM11 is to SM13.
Exactly, the fibre-optical drawing speed of sample SM11 is arranged to draw rate height than sample SM12.But, because sample SM11 has identical meniscus length with SM12, make the cooling velocity of sample SM11 be higher than the cooling velocity of sample SM12.Equally, the fibre-optical drawing speed of sample SM12 and SM13 is equal to each other.But, because the meniscus length of sample SM12 is shorter than the meniscus of sample SM13, the cooling velocity of sample SM12 is than the cooling velocity height of sample SM13.
Have been found that at sample SM11 in SM13 given relation below existing:
C3＞C4＞C5，N3＞N4＞N5，α3＞α4＞α5
C3 wherein, C4 and C5 respectively representative sample SM11 to the cooling velocity of SM13, N3, representative sample SM11 is to the NBOHC content of SM13 respectively for N4 and N5, α 3, α 4 and α 5 difference representative sample SM11 are to the recruitment of the 1.38 μ mOH absorption of SM13.
Then, the present inventor has carried out research widely, is attempting by the relation between the recruitment that defines NBOHC defect density and 1.38 μ m OH absorption quantitatively, and is understanding critical conditions, and understanding that fibre-optical drawing equipment limits the condition of critical conditions.
As a result, have been found that condition given below (1) is necessary:
(1) by wherein adding in the single-mode fiber that silica-based glass that Ge and/or F are arranged forms, glass workpiece must comprise intermediate core and clad section at least, glass workpiece has the external diameter of about 125 μ m, and the concentration at non-bridge joint oxygen vacancies center is not less than the concentration at the non-bridge joint oxygen vacancies center in the cladding regions that is arranged on the MFD region exterior in the MFD zone.
Also find, need satisfy condition given below (2):
(2) record with the electron spin resonance method, with the spin density be unit, the density at the non-bridge joint oxygen vacancies center that is comprised in the central area of glass workpiece (radius is the zone of 25 μ m) must not be higher than 1.0 * 10 13Spin/gram.
According to the research that the present inventor carried out, in the optical fiber that satisfies the condition that provides previously, be exposed to the recruitment that 1.38 μ m OH that 1 atmospheric pressure hydrogen caused absorb under the room temperature and be not more than 0.1dB/km.
The present inventor has also carried out a large amount of research to the paramagnetic defective that migration of element and migration of element caused in the glass that diffusion caused of material in the fiber draw process.
Have been found that and require glass preform before fibre-optical drawing, not comprise the OH base.In order to realize particular state, in the manufacture process of synthetic glass carbon black (glass soot), handle porous body with chlorine usually.Thereby, in the lower synthetic quartz base glass of OH base content, comprise a large amount of chlorine usually.Think oxygen in the chlorine displacement glass, thereby form the Si-Cl key.Known in this area, owing to heat or stress, Si-Cl is easy to disconnect in fiber draw process, thereby forms the paramagnetic defective (Si-E ' shown in Fig. 1 C) that is called E ' center.
In order to find out remaining Si-E ' after the fibre-optical drawing, the relation between the cl concn before NBOHC spin density and the fibre-optical drawing in the glass, the present inventor studies.
Form covering on the core prefabricated rods identical, under the condition identical, carry out fibre-optical drawing subsequently with sample SM13 with three kinds of different cl concn values with above-mentioned sample SM13, thus preparation optical fiber.Research is exposed to 1.38 μ m OH before the hydrogen and absorbs and be exposed to the recruitment that OH that hydrogen causes absorbs, and expresses the result in table 3.In the table 3 in the cladding regions unit of cl concn be ppm.
Table 3
Numbering Cl concn in the covering 1.38 the initial absorption of μ m 1.38 the increase that μ m absorbs Spin density (spin/gram) Spin density (spin/gram)
Si-E NBOHC
SM14 200 0.345 0.16 1.2E+13 1.2E+13
SM14E 4.9E+13 4.9E+13
SM15 1000 0.323 0.03 5.8E+13 1.4+12
SM15E 3.0E+13 ND
SM16 3500 0.286 0.03 3.3E+14 1.1E+12
SM16E 3.1E；14 ND
Fig. 6 and 7 curves for test figure given in the expression table 3.
Fig. 6 represents, if the cl concn in the cladding regions is higher, residue has a large amount of Si-E ' in optical fiber, and the OH absorption loss of 1.38 μ m is less before being exposed to hydrogen.On the other hand, it is 3 that Fig. 7 is illustrated in cl concn, and the situation of 500ppm and cl concn are 1, between the situation of 000ppm, does not recognize and is exposed to the significant difference that OH uptake that hydrogen causes increases.In the time of within cl concn is in above-mentioned scope, can confirm obviously that the recruitment that OH absorbs is not subjected to the influence of cl concn.But, should be noted that thinking has increased the amount that is exposed to the increase that OH that hydrogen causes absorbs if cl concn is lower than 200ppm.This can be confirmed by the measurement result of NBOHC.
Or rather, can be interpreted as reasonably that if the cl concn in the minimizing cladding regions, the viscosity of glass increases, thereby reduce the consistance of viscosity and core segment that the result tends to residual defective down after fibre-optical drawing.Can also reasonably be interpreted as, be the mechanism that a kind of chlorine molecule might reduce the possibility that combines with the free radical that is buried.
And, the Si-E ' density in MFD and the cladding regions is compared, found that the Si-E ' density in the MFD is than cladding regions height.This and cl concn are not less than 1, and the result in the 000ppm situation is opposite.
The test figure that provides above confirms, the OH absorption loss of 1.38 μ m will be reduced to 0.35dB/km or littler fully before the hydrogen in order to be exposed to, to be exposed to the recruitment that OH that hydrogen causes absorbs and be reduced to 0.05dB/km or littler fully, the concentration of the chlorine that is comprised in the requirement cladding regions is not less than 1, the density of remaining Si-E ' is not less than 5 * 10 in the 000ppm, optical fiber 13Spin/gram.
Below, the third embodiment of the present invention will be described.
The amount of residual fault of construction greatly depends on the cooling procedure in the fibre-optical drawing step in the optical fiber.When will being drawn into fiber as the glass preform of pseudo-liquid (a pseudo fluid), and when promptly cooling is cured, the state when glass structure keeps losing flowability.Can reasonably be interpreted as the Liquid Structure when glass structure keeps solidifying.Temperature when glass is cured is called as fictive temperature.Known in this area, given relation below between fictive temperature and rayleigh scattering coefficient A, existing:
A＝(8π 3/3)n 5·p 2·kTf·KT
Wherein n represents refractive index; P represents photoelastic constant, and k represents Boltzmann constant, and Tf represents fictive temperature, and KT represents isotherm compression speed (inverse of volume elasticity deformation).
According to " J.C.Mikkelsen; Jr. and F.L.Galeener; Journal ofNon-Crystalline Solids 37 (1980) 71; 84 " and " A.E.Geissberger and F.L.Galeener; Physical review B; Vol.28, Number 6 (1983) "; analyzing in the Raman optical spectrum method of glass structure defective by the deviation of measuring between Rayleigh scattering line and the Raman scattering line; can obtain fictive temperature Tf from the ratio of the defect line (D1 line) of representing three joint glass ring structures and defect line (D2) line of representing four joint glass ring structures.In fact, can be by using light by the transmission of MFD central area, or and to the scattered light of backscatter, record Raman shifts, and obtain fictive temperature Tf.
With the Raman shifts spectrum of specific method measuring samples SM3, so that calculate fictive temperature Tf to SM5.Table 4 is expressed the result.
Table 4
Numbering Tf(℃)
SM11 1245
SM12 1223
SM13 1186
The curve that concerns between the recruitment of Fig. 8 for the OH absorption of expression fictive temperature Tf and 1.38 μ m.
From Fig. 8 obviously as can be seen, if the fictive temperature Tf in the central area of MFD is not higher than 1,200 ℃, the OH that is exposed to the 1.38 μ m that hydrogen causes might be absorbed recruitment and suppress to be 0.05dB/km.
Use description to make the fibre-optical drawing equipment of above-mentioned quartzy SMF below.
As previously described, the present inventor has carried out widely research, attempt to improve among the quartzy SMF anti-hydrogen with the relevant long-term reliability of OH absorption loss of 1.38 μ m.In detail, the present inventor is placed on the optical fiber cooling procedure that is comprised in the fibre-optical drawing step with very big notice.Be known in the art, qualitative, cooling procedure greatly influences remaining fault of construction in the optical fiber.But, can't carry out quantitative test in this respect.
The present inventor has further carried out research widely, the factor that may further improve anti-hydrogen is found in trial, and the heating furnace part of attempting changing in many ways fibre-optical drawing equipment, on the basis of the fibre-optical drawing condition that does not reduce optic fibre characteristic itself, optimize the parameter of these factors.
Found that, in order to improve resistance to hydrogen, importantly cool off the silica-based glass prefabricated rods continuously, with the cooling velocity in 1,000 ℃/second to 3,000 ℃/second scope, from the part that becomes elongated by fusing, be that meniscus partly begins, dropped to till 1,200 ℃ up to the surface temperature of optical fiber.In addition, have been found that the sintering condition of silica-based glass carbon black is also very important.
In traditional method and apparatus, partly do not begin to cool off continuously quartzy P series glass prefabricated rods from meniscus.
The present inventor also finds, if in 300 to 1 of reality, under 500 meters/minute the fibre-optical drawing speed, and in the manufacture process of quartzy SMF, the external diameter of prefabricated rods is that the fibre-optical drawing condition comprises the elongated portion of institute's drawing optical fiber prefabricated rods under 35 to 120mm the condition, it is the meniscus part, have the length that is not less than " A * 5 ", wherein A represents the diameter (mm) of prefabricated rods, might realize required cooling procedure.Meniscus partly is defined as, by melting fiber prefabricated rods in the fibre-optical drawing stove, diameter is reduced to the length in the zone of 5% prefabricated rods diameter from 90% prefabricated rods diameter herein.
Fig. 9 schematically shows the structure of fibre-optical drawing equipment, the feasible fibre-optical drawing condition that might obtain to point out above.In this fibre-optical drawing equipment, glass preform 51 is inserted in the heating furnace 52, carry out the fibre-optical drawing operation.As shown in FIG., the well heater 53 that will be used to heat prefabricated rods 51 is arranged in the heating furnace 52.Parameter 54 expression meniscus parts shown in the figure, (take-up) device is batched in parameter 57 expressions one.
In fibre-optical drawing equipment shown in Figure 9, the following right cylinder 56 that is used for cooling off continuously institute's drawing optical fiber 55 is arranged to touch with the bottom connection of fibre-optical drawing stove 52, as the device of fibre-optical drawing condition given above realizing.Should be noted that the flow velocity with 5 liters/minute, with the gas mixture of Ar and He, the following cylindrical sidewall by shown in Figure 10 is transported to down in the right cylinder.
Device shown in Fig. 9 and 10 makes and might be continuously the zone in the part scope of the meniscus part 54 of prefabricated rods and the optical fiber 55 with specified diameter to be cooled to about 1,200 ℃.
Have been found that by descending the length L of right cylinder 56 1Given relation below (length of optical fiber 55 slow cool downs part) is arranged to satisfy, may realize specific slow cool down condition:
L 1(mm)＞B×B/300
Wherein B represents the draw rate (meter/minute) of optical fiber.
The slow cool down condition is equivalent under 1,000 to 3,000 ℃/second cooling velocity, with the surface temperature of the optical fiber 55 that drawn, from for example 1,700 ℃ of condition that is cooled to 1,200 ℃ continuously.Also find, be arranged to not be formed for gas is introduced the air intake opening in the gap between heating furnace 52 and the well heater by the well heater that will be used to heat institute's drawing optical fiber 55, and by the length L with well heater 2Be arranged to satisfy relation given below, and obtain required slow cool down condition:
L 2(mm)＞C×B/200
Wherein B represents the draw rate (meter/minute) of optical fiber, and C represents the diameter (mm) of preform.
In addition, have been found that if be used for distance L between top one side of top one side of well heater 53 of heating furnace 52 of heating optical fiber preform 51 and heating furnace 52 3, the distance L between bottom one side of well heater 53 and bottom one side of heating furnace 52 4Satisfy relation given below, might increase insulation effect, so that meniscus obtains required shape:
L 3(mm)＞C×B/200
L 4(mm)＞C×B/200
Wherein B represents the draw rate (meter/minute) of optical fiber, and C represents the diameter (mm) of preform.
Describe in detail as top, the invention provides a kind of single-mode fiber,, also can not increase loss even make optical fiber is kept in the atmosphere that comprises hydrogen one for a long time with anti-hydrogen.
Those of ordinary skills will be easy to expect other advantage and modification.Thereby, in the broadest sense, the invention is not restricted to shown here and described specified otherwise and typical example.Therefore, under the condition of the scope that does not depart from the spiritual or general inventive concept that is limited by claims and its equivalent, can carry out multiple modification.

Claims (9)

1. single-mode fiber, this single-mode fiber is formed by silica-based glass and comprises the glass workpiece with intermediate core and cladding regions, it is characterized in that not being higher than 1.0 * 10 as the density at non-bridge joint oxygen vacancies center in the described glass workpiece of the spin density value that is recorded by the electron spin resonance method 14Spin/gram, near and the distribution of the luminous intensity in the wavelength region may 650nm in the xsect of the described glass workpiece of measuring by cathode electronics stimulated luminescence method, make that intensity is the strongest near the outside of described intermediate core and excircle part the annular region, and intensity weakens towards the outside appropriateness of described intermediate core.
2. single-mode fiber according to claim 1 is characterized in that cl concn in the described cladding regions is higher than the cl concn in the intermediate core.
3. single-mode fiber according to claim 1 is characterized in that in described glass workpiece, is that the density of paramagnetic defective Si (the D)-E ' of unit is not less than 1.0 * 10 by the spin density value that records with the electron spin resonance method 12Spin/gram.
4. single-mode fiber according to claim 1, the density that it is characterized in that being included in the non-bridge joint oxygen vacancies center in the MFD zone of described glass workpiece is lower than the density at the non-bridge joint oxygen vacancies center that is included in the described cladding regions that is arranged in the MFD region exterior.
5. single-mode fiber according to claim 1, it is characterized in that by the spin density value that records with the electron spin resonance method be unit, is that the density at the non-bridge joint oxygen vacancies center that comprised in the zone of radius 25 μ m is not higher than 1.0 * 10 at the center of the described glass workpiece of distance 13Spin/gram.
6. single-mode fiber according to claim 1 is characterized in that the cl concn in the described cladding regions is not less than 1000ppm.
7. single-mode fiber according to claim 1 is characterized in that by the spin density value that records with the electron spin resonance method be unit, and the density of the paramagnetic defective Si-E ' that comprises in the described glass workpiece is not less than 5.0 * 10 13Spin/gram.
8. single-mode fiber according to claim 1, it is characterized in that at room temperature, loss increase after being exposed to 1 atmospheric hydrogen is different from the loss that hydrogen molecule caused that is diffused in the glass workpiece to be increased, and it is not more than 0.1dB/km in the wavelength coverage of 1.38 μ m to 1.42 μ m.
9. single-mode fiber according to claim 1, it is characterized in that by measure between Rayleigh scattering line and the Raman scattering line deviation obtained, be not higher than 1200 ℃ by the defect line of expression three joint glass ring structures with the resulting fictive temperatures of ratio that expression four saves the defect line of glass ring structures.
CNB2005101295970A 2001-07-30 2002-05-29 Single mode optical fiber, method of manufacturing the same, and apparatus for manufacturing the same Expired - Fee Related CN100357770C (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104496170A (en) * 2014-12-31 2015-04-08 江苏通鼎光棒有限公司 Optical fiber drawing cooling pipe employing H2 and method
CN106536434A (en) * 2014-06-24 2017-03-22 康宁股份有限公司 Low attenuation fiber with viscosity matched core and inner clad
CN111712979A (en) * 2018-02-16 2020-09-25 古河电气工业株式会社 Optical semiconductor device

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0673895A3 (en) * 1994-03-24 1996-01-03 At & T Corp Glass optical waveguides passivated against hydrogen-induced loss increases.
JP3424711B2 (en) * 1995-11-09 2003-07-07 住友電気工業株式会社 Glass body for optical fiber and optical fiber

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106536434A (en) * 2014-06-24 2017-03-22 康宁股份有限公司 Low attenuation fiber with viscosity matched core and inner clad
CN104496170A (en) * 2014-12-31 2015-04-08 江苏通鼎光棒有限公司 Optical fiber drawing cooling pipe employing H2 and method
CN111712979A (en) * 2018-02-16 2020-09-25 古河电气工业株式会社 Optical semiconductor device
CN111712979B (en) * 2018-02-16 2023-08-22 古河电气工业株式会社 Optical semiconductor device

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