CN1842499A - Optical fiber containing an alkali metal oxide and methods and apparatus for manufacturing same - Google Patents

Abstract

Disclosed is an optical fiber having a core with an alkali metal oxide dopant in an peak amount greater than about 0.002 wt. % and less than about 0.1 wt. %. The alkali metal oxide concentration varies with a radius of the optical fiber. By appropriately selecting the concentration of alkali metal oxide dopant in the core and the cladding, a low loss optical fiber may be obtained. Also disclosed are several methods of making the optical fiber including the steps of forming an alkali metal oxide-doped rod, and adding additional glass to form a draw perform. Preferably, the draw preform has a final outer dimension (d2), wherein an outer dimension (d1) of the rod is less than or equal to 0.06 times the final outer dimension (d2). In a preferred embodiment, the alkali metal oxide-doped rod is inserted into the centerline hole of a preform to form an assembly.

Description

The optical fiber of alkali metal containing oxide compound and make the method and apparatus of this optical fiber

The cross reference of related application

The application requires to enjoy U.S. Provisional Application No.60/498901 that submitted on August 29th, 2003 and the U.S. Provisional Application No.60/528 that submitted on December 10th, 2003 under 35U.S.C. § 119 (e), 639 right of priority, described application is combined in this by reference.

Invention field

The present invention relates to mix alkalimetal oxide optical fiber and make the method and apparatus of this optical fiber.

Background technology

The major limitation that optical fiber is subjected to is decay.For example fiber loss set between the fiber amplifier qualification apart from aspect play an important role.This point is for long distance and extra long distance network particularly important, and for example, use down on the sea, and this amplifier has taken sizable system cost, and is a principal element that influences system reliability.Therefore, be commercial close attention to decay being reduced to possible minimum level.

Summary of the invention

Broad aspect of the present invention includes the optical fiber of core and covering, and this core comprises and is selected from following alkalimetal oxide: K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂O, and their mixture, the peak concentration of alkalimetal oxide are greater than about 0.001 weight % but less than about 1 weight %; This covering comprises its peak concentration less than the peak concentration of fibre core but greater than the alkalimetal oxide of about 0.0005 weight %; The concentration of alkalimetal oxide changes with fiber radius in the optical fiber.Alkali metal oxide dopant concentration should be accompanyed or follow the radius increase of fiber optic hub line and be reduced.The alkalimetal oxide adulterating method that adopts this paper to disclose, the optical fiber of making have decay at 1310nm less than about 0.30dB/km, at 1550nm less than about 0.18dB/km; More fortunately 1550nm is less than about 0.17dB/km, better at 1550nm less than about 0.16dB/km.

Preferably, the core of optical fiber and covering all contain alkali metal oxide dopant.The cladding glass of optical fiber can comprise fluorine (F).Optical fiber has at least one core ring section (core segment); In some preferred implementation, optical fiber comprises a plurality of core ring sections.The concentration of alkalimetal oxide on the radius that equals the optical fiber mode fields radius should be at least about 0.001 weight %.

The present invention proposes a kind of optical fiber with core of alkali metal containing oxide compound, and described alkalimetal oxide is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂O, and their mixture, described core contains the OH less than 20ppb.

According to embodiment of the present invention on the other hand, propose a kind of optical fiber with core and covering, this core comprises and is selected from Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide are greater than about 0.001 weight % but less than about 1 weight %; This covering comprises its peak concentration less than the peak concentration of core but greater than the alkalimetal oxide of about 0.0005 weight %; The concentration of alkalimetal oxide changes with fiber radius in the optical fiber.

According to embodiment of the present invention on the other hand, propose a kind of optical fiber with core and covering, this core comprises its peak concentration greater than about 0.001 weight % but less than the Rb of about 1 weight % ₂O; This covering comprises its peak concentration less than the peak concentration of core but greater than the Rb of about 0.0005 weight % ₂O; The concentration of alkalimetal oxide changes with fiber radius in the optical fiber.

Another big aspect according to the present invention provides a kind of optical fiber that comprises core, and this core comprises GeO ₂Be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture; Specific refractory power to optical fiber is selected, and is provided at the total dispersion (dispersion) of about 1550nm greater than about 1ps/mn/km, at 1550nm less than about 0.10ps/nm ²The chromatic dispersion gradient of/km (dispersion slope).Preferably, optical fiber at the total dispersion of 1550nm greater than about 6ps/nm/km.Preferably, optical fiber in the decay of 1550nm less than about 0.18dB/km; Better at 1550nm less than about 0.17dB/km.Preferably, with 10m/s wire drawing at least (draw) speed drawing optical fiber.

According to another aspect of the present invention, the optical fiber that this paper discloses comprises: the silicon dioxide base core and surround core and with the silicon dioxide base covering of its direct neighbor, this core comprises first doping agent that is selected from germanium oxide (germania), fluorine and their mixture, and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration are 20-1000ppm; Wherein, in the decay of 1550nm less than 0.185dB/km, better less than 0.18dB/km, better less than 0.17dB/km.In some preferred implementation, be less than or equal to 0.167dB/km in the decay of 1550nm.In preferred embodiment, the alkali metal oxide concentration in the core descends with fiber radius.Preferably, in the core peak concentration of alkalimetal oxide greater than about 0.002 weight % but less than about 0.07 weight %.In preferred embodiment, the alkali metal oxide concentration on the radius that equals the optical fiber mode fields radius is at least about 0.0001 weight %.In some embodiments, described core comprises GeO ₂, in other embodiment, core does not contain GeO ₂In some embodiments, described core comprises a core ring section.In other embodiments, core comprises a plurality of core ring sections.In some preferred implementation, covering comprises F, especially at core oxygen-free germanium in some embodiments.In a preferred embodiment, in the core peak volume of alkalimetal oxide greater than about 0.002 weight % but less than about 0.05 weight %.In different embodiments, optical fiber outer gland sealing coating; In specific implementations, first doping agent is a germanium oxide, and promptly optical fiber is the doping germanium oxide, and optical fiber also comprises the outer gland sealing coating.In some preferred implementation, optical fiber is single mode fibre, for example at 1550nm monotype (single-moded); In other preferred implementation, optical fiber is multimode fibre, better is the fiber with graded index distribution (profile).Some preferred implementation is the optical fiber of non-zero dispersion shift, and its chromatic dispersion is 1-6ps/nm-km at 1550nm, and the chromatic dispersion of other embodiment is 6-15ps/nm-km at 1550nm.

According to a further aspect of the invention, the optical fiber in this announcement comprises: the covering of core and this core of coating, described core comprises GeO ₂Be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture wherein, is selected the index distribution of optical fiber, being provided at the total dispersion of 1550nm greater than about 1ps/nm/km, and at zero-dispersion wavelength less than about 0.10ps/nm ²The chromatic dispersion gradient of/km.In a preferred embodiment, at the total dispersion of 1550nm greater than about 6ps/nm ²/ km.Preferably, in the decay of 1550nm less than about 0.18dB/km, better less than about 0.17dB/km.

Another broad aspect of the present invention comprises at the optical fiber of this announcement: core and surround core and with the covering of its direct neighbor, described core comprises and is selected from Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration are greater than about 0.001 weight % but less than about 1 weight %.

Another broad aspect of the present invention comprises at the optical fiber of this announcement: core and surround core and with the covering of its direct neighbor, described core comprises Rb ₂O, its peak concentration are greater than about 0.001 weight % but less than about 1 weight %.

Another broad aspect of the present invention comprises at the optical fiber of this announcement: the silicon dioxide base core and surround core and with the silicon dioxide base covering of its direct neighbor, described core comprises first doping agent that is selected from germanium oxide, fluorine and their mixture, and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration is 20-1000ppm; One relative refractive index peak is arranged, Δ in the index distribution of described core _MAX, bigger by 0.2% than covering.Preferably, optical fiber less than 0.185dB/km, better less than 0.18dB/km, preferably is less than or equal to 0.17dB/km in the decay of 1550nm.In some preferred implementation, be less than or equal to 0.167dB/km in the decay of 1550nm.In some preferred implementation, fiber is a multimode fibre, and core comprises at least 70 weight %SiO ₂In other preferred implementation, core comprises at least 80 weight %SiO ₂In other embodiments, core comprises at least 90 weight %SiO ₂Preferably, optical fiber is single mode fibre, and core comprises at least 90 weight %SiO ₂Preferably, core also comprises the chlorine of peak concentration less than 3000ppm.Preferably, the peak concentration of alkalimetal oxide is less than 700ppm.Preferably, the mean concns of alkalimetal oxide is less than 350ppm.In some preferred implementation, the peak concentration of alkalimetal oxide is less than 500ppm, and promptly the peak concentration of alkalimetal oxide is 20-500ppm.In a preferred embodiment, alkalimetal oxide is K ₂O.In first group of preferred implementation, first doping agent is a germanium oxide, and the peak concentration of alkalimetal oxide is 30-300ppm, is preferably 30-150ppm.Core better also comprises the chlorine of peak concentration less than 3000ppm.Preferably, the maximum cl concn of core is less than 0.2 weight %.In some preferred implementation, covering comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration is less than 100ppm.In second group of preferred implementation, first doping agent is a fluorine, and the peak concentration of alkalimetal oxide is 200-500ppm, is 100-300ppm in some preferred implementation.Preferably, the fluorine concentration of core is greater than 0.02 weight %, more preferably core in the fluorine concentration of medullary ray greater than 0.02 weight %.Preferably, the fluorine concentration of core is greater than 0.15 weight %.The maximum fluorine concentration of preferred core is 0.5-1.5 weight %.In second group of particularly preferred embodiment, core is substantially free of germanium oxide, preferably oxygen-free germanium.Preferably, the minimum fluorine concentration of covering is at least 1.0 weight %.In a preferred embodiment, alkalimetal oxide is K ₂O.In some embodiments, core also comprises the chlorine of its peak concentration less than 500ppm.Preferably, covering comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration is less than 100ppm.

And disclose a kind of fibre-optical preform, this prefabricated component has the centre portions of mainly being made up of solid glass, the outer layer segment coating of the involved glass soot of this centre portions, and centre portions contains and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture.Preferably, alkalimetal oxide is selected from K ₂O and Rb ₂O.Preferably, centre portions also contains GeO ₂Outer layer segment should comprise GeO ₂Centre portions should contain the OH less than 20ppb.

Another broad aspect of the present invention discloses a kind of method of making optical fiber, and this method comprises: form to comprise and be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂First glass stick of the alkalimetal oxide of O and their mixture inserts this first glass stick in the centre hole of fibre-optical preform, forms compound prefabricated subassembly.In a preferred implementation, glass stick comprises GeO ₂Preferably, fibre-optical preform comprises GeO ₂At the each point of fibre-optical preform manufacturing processed, described fibre-optical preform should comprise the glass soot.

Another broad aspect of the present invention relates to the method for making optical fiber, and this method comprises: provide to comprise to be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The fibre-optical preform of the alkalimetal oxide of O and their mixture, this fibre-optical preform is drawn into optical fiber, drawing speed and tensile stress (draw tension) are selected to control the concentration of alkalimetal oxide in the optical fiber, and this concentration is with change in radius.

Another big aspect of the present invention provides the method for making optical fiber, and this method may further comprise the steps: provide to comprise to be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The fibre-optical preform of the alkalimetal oxide of O and their mixture, the thermal treatment fibre-optical preform regular hour under effectively obtaining in the fibre-optical preform with the temperature of the predetermined alkali metal oxide concentration of change in radius.Preferably, this method comprises that the thermal treatment fibre-optical preform was at least about 6 hours.Preferably, at least 1000 ℃ fibre-optical preform is heat-treated.Preferably, the cladding glass of fibre-optical preform comprises F.

Another big aspect according to the present invention provides the method for making optical fiber, and this method may further comprise the steps: provide outside dimension (d1) also with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The adulterated glasswork of the alkalimetal oxide of O and their mixture; In this glasswork, add another kind of glass, formation has the last fixed wire drawing prefabricated component of last outside dimension (d2), wherein outside dimension (d1) is less than or equal to 0.06 times of last outside dimension (d2), thereby alkalimetal oxide is concentrated near the center of last fixed wire drawing prefabricated component.

Another big aspect according to the present invention, the method of making optical fiber is provided, this method may further comprise the steps: will contain the silicon-dioxide soot and be deposited on the live spindle, formation contains the pipe of silicon-dioxide soot, at first contain the pipe of silicon-dioxide soot, contain the pipe of silicon-dioxide soot, the pipe of fixed this silicon-dioxide soot with dry this of fluoro-gas then with dry this of chlorine-containing gas, form Glass tubing, with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms; This Glass tubing of burning shrinkage (collapsing) or intermediate, the rod of formation alkali doped, and the interpolation another kind contains silica glass on the rod of alkali doped.

Another big aspect according to the present invention, the method of making optical fiber is provided, this method may further comprise the steps: will contain the silicon-dioxide soot and be deposited on the live spindle, formation contains the pipe of silicon-dioxide soot, at first contain the pipe of silicon-dioxide soot, contain the pipe of silicon-dioxide soot, the pipe of fixed this silicon-dioxide soot with dry this of fluoro-gas then with dry this of chlorine-containing gas, form Glass tubing, with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms; This Glass tubing of burning shrinkage or intermediate, form the rod of alkali doped, the rod of alkali doped is inserted the pipe that contains the silicon-dioxide soot, formation is by containing alkali doped clavate plug that becomes and the pipe that contains the silicon-dioxide soot, on this plug, add the silicon-dioxide of doped with fluorine, the silicon-dioxide of fixed doped with fluorine forms last wire drawing prefabricated component.

In addition, another big aspect according to the present invention, the method of making optical fiber is provided, this method may further comprise the steps: the silicon-dioxide soot of doped germanium is deposited on the pipe that forms the silicon-dioxide soot of doped germanium on the live spindle, pipe with the silicon-dioxide soot of dry this doped germanium of chlorine-containing gas, contain the pipe of silicon-dioxide soot with dry this of fluoro-gas again, the pipe of the silicon-dioxide soot of fixed doped germanium forms Glass tubing, with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms; Form the rod of alkali doped by this Glass tubing or intermediate, rod inserted the pipe that contains the silicon-dioxide soot, this pipe that contains the silicon-dioxide soot comprise doped germanium the silicon-dioxide soot annular inner portion and do not have the outer ring portion of the soot of doping silicon dioxide substantially.

Another big aspect according to the present invention, the method of making optical fiber is provided, this method may further comprise the steps: will contain the silicon-dioxide soot and be deposited on the live spindle and to form the pipe that contains the silicon-dioxide soot, contain the pipe of silicon-dioxide soot with dry this of chlorine-containing gas, contain the pipe of silicon-dioxide soot with dry this of fluoro-gas then, the pipe of fixed this silicon-dioxide soot forms Glass tubing, with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms, and forms the goods of alkali doped, and wherein alkalimetal oxide mixes with about 20-1000ppm amount.

Another big aspect according to the present invention provides a kind of diffusing, doping equipment, and this equipment comprises a frame, is placed to the Glass tubing of this frame rotation relatively, is connected to the dopant source of Glass tubing, and the induction heater of close Glass tubing installation.

Describe other features and advantages of the present invention below in detail, by these explanations, these feature and advantage to those skilled in the art, part is conspicuous, perhaps, comprise that following detailed description, claims and accompanying drawing enforcement the present invention recognize these feature and advantage by by described herein.

The general introduction and the following detailed that should be understood that the front provide embodiments of the present invention, aim to provide summary or the framework of understanding desired character of the present invention and characteristic.Accompanying drawing provides further understanding of the invention, accompanying drawing can in conjunction with and constitute the part of this specification sheets.Description of drawings the embodiments of the present invention, and be used for illustrating principle of the present invention and operation with specification sheets.Wherein suitable, identical feature is with identical numeral number.

The accompanying drawing summary

Shown in Figure 1 is the part with Refractive Index Profile o of the step-refraction index (step index) with the alkali metal oxide concentration of change in radius.

Shown in Figure 2 is the Refractive Index Profile o that a plurality of core retainer plates are arranged, and the alkali metal oxide concentration with change in radius in this distribution and the fiber compares.

Shown in Figure 3 is another Refractive Index Profile o that a plurality of core retainer plates are arranged, and the alkali metal oxide concentration with change in radius in this distribution and the fiber compares.

Shown in Figure 4 is that the Refractive Index Profile o part of specific refractory power less than the step-refraction index of the clad region of pure silicon dioxide specific refractory power arranged, and the alkali metal oxide concentration with change in radius in this distribution part and the fiber compares.

Shown in Figure 5 is mixed F and K ₂The figure of the scattering loss of the silica glass rod of O shows F and K ₂O concentration with crosscut should rod variable in distance.

Fig. 6 is the figure of concentration among Fig. 5, comprises representative function [K] * [F] ³Curve.

Shown in Figure 7ly be two kinds and contain different alkali metal oxide dopant Cs ₂O and Rb ₂O, and contain the glass plug of F, and a kind of contains K ₂The scatter diagram of the glass plug of O.

Shown in Figure 8 is to the Cs among Fig. 7 ₂O, Rb ₂The figure of the concentration of O and F.

The K that the section radius with fibre-optical preform that is two kinds of different method of diffusion of explanation produce shown in Figure 9 changes ₂The figure of O concentration.

Shown in Figure 10 is K on the transverse section of a part of three optical fiber after stretching with predetermined tension and drawing speed ₂The O concentration map.

Shown in Figure 11 is the method for making the optical fiber of the alkalimetal oxide that mixed according to the present invention.

Figure 12 illustrates with alkalimetal oxide Glass tubing is carried out adulterated method.

Figure 13 illustrates glass stick is carried out the tensile process.

Figure 14 illustrates the method for fibre-optical preform being carried out alkali metal oxide-doped by the glass stick of alkali metal oxide-doped is inserted the centre hole of porous soot fibre-optical preform.

Shown in Figure 15 is K on the glass diameter of mandrel ₂O and GeO ₂Concentration distribution.

Shown in Figure 16 is the method for deposition glass soot.

Figure 17 is to the present invention K that mixes ₂The glass stick of O, K ₂O concentration is with the figure of change in radius.

Figure 18 is the Na that spreads on silica glass rod of the present invention transverse section ₂O concentration is with the figure of change in radius.

Figure 19 illustrates K on the transverse section of fibre-optical preform made in accordance with the present invention ₂The figure of the concentration of O, F and Cl.

Shown in Figure 20 is to having doping K ₂The K of the single-mode fiber of the core of O and the covering of doped F ₂The concentration of O and F.

Shown in Figure 21 is to having doped with Ge O ₂The K of single-mode fiber of fibre core ₂O, F and GeO ₂Concentration.

Shown in Figure 22 is Rb in the plug of fibre-optical preform ₂O and F concentration.

Shown in Figure 23 is Cs in the plug of fibre-optical preform ₂The concentration of O and F.

The concentration distribution of the optical fiber that the inventive method that Figure 24 explanation discloses according to this paper is made and relative refractive index are with the variation of radius.

Shown in Figure 25 is schema according to a kind of preferred method of the manufacturing optical fiber of one aspect of the invention.

Shown in Figure 26 is schema according to the another kind of preferred method of the manufacturing optical fiber of one aspect of the invention.

Be according to the mixed distribution of relative refractive index of alkali-metal fiber of the present invention shown in Figure 27 and 28.

Figure 29 is according to the isometric view of the lathe of one aspect of the invention (isometric view), illustrates an induction heating source.

Figure 30 is the sectional view in the induction heating source of Figure 29.

Figure 31 is the refractive index profile according to the doping germanium oxide optical fiber of one aspect of the invention.

Figure 32 is the weight % of each doping agent and the graph of a relation of fiber radius.

Figure 33 is K in each fiber embodiment ₂The graph of a relation of O weight % and fiber radius.

Figure 34 is according to the refractive index profile of the another kind of optical fiber of one aspect of the invention.

Figure 35 is according to the weight % of each doping agent of the another kind of optical fiber of the present invention and the graph of a relation of fiber radius.

Detailed Description Of The Invention

The present invention relates to a kind of low loss optical fiber and manufacture method thereof. More specifically, the present invention relates to be doped with the optical fiber of alkali metal oxide and make this optical fiber and the method for relevant prefabricated component. Following term used herein has to give a definition:

-mode field diameter is the tolerance to the luminous power of traversing the single-mode fiber end face, can be expressed as:

2ω ₀＝(λ/π)[2∫I(Φ)sinΦcosΦdΦ]/∫I(Φ)sinΦcosΦdΦ] ^1/2  (1)

In the formula, 2 ω₀Mode field diameter (so ω₀Spot size), λ is the average light wavelength, Φ is the angle for the radiation diagram center, should carry out from 0 ° to 90 ° integration. Mode field diameter can be measured according to for example method of inspection ANSI/TIA/EIA-455-191-A-2001.

-effective area is

                 A _Effectively＝2π(∫E ²rdr) ²/(∫E ⁴rdr)              (2)

In the formula, range of integration is 0 to ∞, the electric field that E is relevant with the light of propagation.

-relative index of refraction, Δ is by equation DELTA_i＝(n _i ²-n _c ²)/2n _i ²Definition, n in the formula_iThe largest refractive index of index distribution section i, n_cUsually to get the refractive index with reference to the district of making the covering minimum refractive index. Relative index of refraction represents with % usually, represents with term % Δ herein, and unless otherwise noted, the % Δ represents the refractive index with respect to the maximum of the core of covering minimum refractive index.

-term index distribution or abbreviation index distribution are in selected fiber section, normally the % Δ on the core and the relation between radius.

-term α distribution refers to the index distribution according to the core of following formula,

                     n(r)＝n ₀(1-[r/a] ^α)                       (3)

In the formula, r is the radius of core, and a is the terminal point in this distribution, and at the first point of this distribution, r elects 0, n as₀Be be concerned about that the largest refractive index in the core district of (interest), α are indexes of this core distribution map shape of definition. Other common core refractive index profile shape comprises step-refraction index, trapezoidal refractive index and sphering step-refraction index, and sphering wherein is because of the diffusion of adulterant in the vertiginous zone of refractive index.

-core refers to generally have with respect to covering in the optical fiber part of the refractive index of increase, and the luminous power of emission is mainly propagated by this core. Core can be comprised of one or more axle sleeves. The refractive index of each core ring section can greater than, be equal to or less than the refractive index of pure silicon dioxide.

-covering or covering axle sleeve (segment) refer to coat the fiber section in core zone, be defined as the absolute magnitude of relative index of refraction less than 0.03%, and until the maximum radius of the silica base section of optical fiber namely until the maximum radius of covering still keeps the situation less than 0.03%. At radius R_CoreThe place, core finishes and covering begins, at radius_CoveringThe place, covering finishes, at this R_Covering＞R _Core。

-" ppm " unless otherwise specifically indicated, refers to parts per million by weight, and " ppm by weight " is will be converted into ppm with the measured value that % by weight represents by multiply by 10,000 factor.

Preferably, the core of optical fiber and covering all contain alkali metal oxide dopant. Alkali metal oxide is K, Na, Li, Cs or Rb preferably, or the oxide of their mixture; Better, alkali metal oxide is K₂O、 Rb ₂O、Cs ₂O or their mixture; Preferably alkali metal oxide is K₂O or Rb₂O. Peak concentration with alkali metal oxide in the consistent single-mode fiber of the peak power of mould field of basic and propagates light is useful, and therefore by preferably. Preferably, the alkali metal oxide concentration in the fiber cores has a peak value. Alkali metal oxide concentration changes rapidly on fiber radius. Preferably, the concentration of alkali metal oxide generally reduces with the radius increase that the fiber optic hub line begins along at least one part of fiber radius. Preferably, alkali metal oxide concentration has the shape near Gauss (Gaussian) as the variable of radius.

Preferably, the peak concentration of the alkali metal oxide in the fiber cores is greater than about 0.001 % by weight but less than about 1 % by weight; Better greater than about 0.001 % by weight but less than 0.4 % by weight; More preferably greater than about 0.001 % by weight but less than about 0.15 % by weight; Be more preferably 0.005 % by weight-0.15 % by weight. Alkali metal oxide peak volume in the fibre cladding should be less than the peak volume of alkali metal oxide in the core. Preferably, in the covering peak volume of alkali metal oxide greater than about 0.0005 % by weight; Better greater than about 0.001 % by weight. In some embodiment, the alkali metal oxide that single-mode fiber comprises is at least about 0.0001 % by weight in the concentration of the radius that equals spot size; Better be about 0.0001 % by weight-0.0005 % by weight. To multimode fibre, should be at least about 0.001 % by weight in core-covering alkali metal oxide amount at the interface of optical fiber; Better be about 0.001 % by weight-0.005 % by weight. Core or covering, or core and covering can comprise a kind of alkali metal oxide dopant and one or more glass-modified adulterant, for example GeO₂Or F. In a preferred embodiment, multimode fibre comprises a core that has graded index to distribute.

Shown in Figure 1 is to have for example index distribution of the single-mode fiber of an independent core ring section to distribute 10, and the alkali metal oxide concentration of giving an example distribution 12 (alkali metal oxide concentration is the function of radius), can reach this CONCENTRATION DISTRIBUTION by putting into practice the present invention. This optical fiber comprises core ring section 14 and the covering axle sleeve 16 at a center. Preferably, alkali metal oxide concentration is with change in radius. Preferably, the concentration of alkali metal oxide generally reduces with the radius increase that the fiber optic hub line begins along at least one part of fiber radius. Preferably, has shape near Gauss as the alkali metal oxide concentration of function of radius. The core ring section 14 of optical fiber can have step shape shown in Figure 1, maybe can have sphering, α or triangular shaped.

Shown in Figure 2 is that the index distribution of giving an example of the chemistry with a plurality of core ring sections (a kind of cored structure of cutting apart) is distributed 18, also draw the alkali metal oxide concentration of this multiple shaft sleeves core fibre as the distribution 20 of radius variable, can obtain this optical fiber by putting into practice the present invention. Preferably, the concentration of alkali metal oxide generally reduces with the radius increase that the fiber optic hub line begins along at least one part of fiber radius. Preferably, has shape near Gauss as the alkali metal oxide concentration of function of radius. This index distribution distribution 18 should comprise the core ring section 22 at a center, the core ring section 24 of first ring, and the core ring section 26 of the second ring. Fig. 2 also illustrates covering axle sleeve 28. Yet, should understand and the invention is not restricted to index distribution shown in Figure 2 and distribute. The refractive index of core ring section can equal, greater than the refractive index of pure silicon dioxide, or the refractive index of this axle sleeve can be less than the refractive index of pure silicon dioxide. As shown in the figure, the refractive index of the first ring axle sleeve 24 shown in Fig. 2 is lowered to the refractive index (pure silicon dioxide represents with 0% Δ) less than pure silicon dioxide. The refractive index of the first ring core ring section 24 can be chosen the refractive index greater than pure silicon dioxide wantonly, and such as dotted line 30 expressions, or the refractive index of first ring axle sleeve 24 equals the refractive index of pure silicon dioxide. The second annulate shaft cover 26 shown in Figure 2 shows that relative index of refraction is greater than the refractive index of pure silicon dioxide. The refractive index of the second annulate shaft cover 26 can be chosen the refractive index less than pure silicon dioxide wantonly, such as dotted line 32 expressions. Perhaps, can omit the second annulate shaft cover 26. Although the fiber cores of drawing in Fig. 2 has three axle sleeves, fiber cores of the present invention can have an arbitrarily axle sleeve. A core ring section can have step-refraction index distribution, the distribution of α index distribution, triangular refractive index distribution distribution, the distribution of sphering index distribution or their combination. It shall yet further be noted that the impact minimum of the alkali metal oxide refractive index of the concentration range that discloses at this paper, can make alkali metal oxide in the diffusion that distributes across whole core index distribution, can not be distributed with slightly impact to existing index distribution. This provides great mobility for manufacture process, because alkali metal oxide can be applied to whole optical fiber when needing, needn't too pay close attention to because the variation of refractive index and variation that optical fiber property is caused.

Shown in Figure 3 is the index distribution 34 that another kind is had the single-mode fiber of the core of cutting apart. Index distribution shown in Figure 3 distributes and comprises that one has α or sphering index distribution center of distribution core ring section 36, and comprises the first ring core ring section 38 and covering axle sleeve 40. The refractive index of the core ring section 38 of first ring can equal the refractive index of pure silicon dioxide, or the optional refractive index greater than pure silicon dioxide of the refractive index of the first ring core ring section 38, shown in dotted line 42. The index distribution distribution 34 optional second ring core ring sections 44 that comprise. Having sphering in the second ring core ring section 44 shown in Figure 3 distributes. However, it should be understood that it also can is other shape, for example, square, triangle or α shape. Fig. 3 also illustrates the CONCENTRATION DISTRIBUTION 45 as the alkali metal oxide of function of radius, can reach by putting into practice the present invention. Preferably, the concentration of alkali metal oxide generally reduces alkali metal oxide concentration with the radius increase that the fiber optic hub line begins along at least one part of fiber radius. Preferably, has shape near Gauss as the alkali metal oxide concentration of function of radius.

Shown in Figure 4 is to by the adulterant with suitable reduction refractive index cladding glass being mixed, and the index distribution that the refractive index that reduces cladding glass forms the optical fiber of step-refraction index distributes 46. Suitable reduction refractive index adulterant for example is F. The optical fiber of Fig. 4 comprises a core ring section 48 and covering axle sleeve 50. The peak value refractive index of core ring section 48 can greater than, be less than or equal to the refractive index of pure silicon dioxide. The refractive index of covering axle sleeve 50 is less than the refractive index of pure silicon dioxide, certainly also less than the refractive index of core. As shown in Figure 4, be that alkali metal oxide concentration for example distributes 52, can be by putting into practice acquisition of the present invention. Preferably, the concentration of alkali metal oxide generally reduces alkali metal oxide concentration with the radius increase that the fiber optic hub line begins along at least one part of fiber radius. Preferably, has shape near Gauss as the alkali metal oxide concentration of function of radius.

Although provide the general Gaussian distribution to some alkali metal oxides in the optical fiber of giving an example in Fig. 1-4, alkali metal oxide concentration also can be other radial variations. For example, alkali metal oxide dopant can be with the radius linear change, or in a step-wise fashion changes.

The inventor has been found that the scattering loss in the silica glass of concentration crossover of alkali metal oxide and F doping and alkali metal oxide and F follows [A] * [F]³Relational expression, wherein [A] represents alkali metal oxide concentration (% by weight), [F] represents the concentration (% by weight) of fluorine F. That is, can adopt relational expression [A] * [F]³Predict the zone that scattering increases or descends. Fig. 5 is illustrated in respectively the K on the part of silica glass rod diameter₂O and F concentration (54,56). Fig. 5 also is illustrated in the light scattering 58 of measuring on the part of this glass bar diameter. The scattering peak 60,62 of the scattering loss that clearly visible expression is large. Fig. 6 also is illustrated in the K that Fig. 5 draws₂The concentration 54,56 of O and F. That show in Fig. 6 is relational expression [K] * [F]³, wherein [K] represents potassium oxide (K₂O) concentration. [K] * [F]³By curve 64 expressions. Comparison diagram 5 and Fig. 6 as can be known, relational expression [A] * [F] among the scattering peak of Fig. 5 60,62 and Fig. 6³The peak 66,68 of expression is consistent. The overlapping zone consistent with propagates light during the scattering that produces in alkali metal oxide and the overlapping zone of F increases optical fiber, for example particularly thorny in the spot size of optical fiber.

The inventor also finds, F and Cs ₂O or Rb ₂The crossover of O combination uses and does not produce and K ₂The same scattering that O and F combination are produced increases.Fig. 7 is illustrated in three kinds of scatterings on the fibre-optical mandrel radius.To plug, we refer to glass stick, and it comprises the glass core that at least a portion is used for optical fiber, and optical fiber can draw from the prefabricated component that contains this glass stick.Plug can also comprise the part of the covering that is used for optical fiber.First plug F and Rb ₂O mixes.To containing Rb ₂The scattering of the plug of O can be by curve 70 expressions.Second plug F and Cs ₂O mixes.To containing Cs ₂The scattering of the plug of O can be by curve 72 expressions.The 3rd plug is only used K ₂O mixes.Contain K ₂The scattering of the plug of O can be by curve 74 expressions.As shown in the figure, comprise Cs ₂O or Rb ₂The levels of scatter of the plug of O is equivalent to and only contains K ₂The scattering that the plug of O shows.Fig. 8 represents to comprise the Rb of first and second plugs ₂O (75), Cs ₂The concentration of O (76) and F (being respectively 77,78).Value shown on Fig. 7 scattering axle is according to the scattering normalization method of pure silicon dioxide.

According to an embodiment of the invention, the zero-dispersion wavelength λ of single-mode fiber ₀Between more about 1280nm-1340nm, zero-dispersion slop S ₀, less than about 0.07ps/nm ²/ km and at the total dispersion of 1550nm, better between about 15ps/nm/km-20ps/nm/km greater than about 15ps/nm/km.Preferably, optical fiber has the cutoff wavelength less than about 1300nm.Preferably, optical fiber at the useful area of 1550nm greater than about 80 μ m ²The core diameter of optical fiber better greater than about 3 μ m, better is about 3-5 μ m, greater than about 9 μ m, better is about 10-11 μ m in the mode field diameter of 1550nm.By comprising alkalimetal oxide, optical fiber can be made into decay at 1310nm less than about 0.30dB/km according to the present invention, and the decay of 1550nm is less than about 0.18dB/km; Better at 1550nm less than about 0.17dB/km, be preferably in 1550nm less than about 0.16dB/km.

In another embodiment, the more about 1330nm-1600nm scope of the zero-dispersion wavelength λ 0 of single-mode fiber better is about 1330nm-1450nm.Core or covering, or core and covering other available other glass-modified doping agent, for example GeO ₂Or F mixes.The optical fiber of present embodiment has a chromatic dispersion slope S at zero-dispersion wavelength ₀, this slope is better less than about 0.07ps/nm ²/ km better is about 0.035ps/nm ²/ km-0.07ps/nm ²/ km, and at the total dispersion of 1550nm greater than about 6ps/nm/km, better be about 6ps/nm/km-15ps/nm/km.Preferably, the cutoff wavelength of optical fiber is less than about 1400nm; Better less than about 1300nm.Preferably, optical fiber is about 45-75 μ m at the useful area of 1550nm ²The alkalimetal oxide adulterating method that adopts this paper to disclose, the optical fiber of making according to this embodiment in the decay of 1310nm less than about 0.30dB/km, at 1550nm less than about 0.18dB/km; Better, less than about 0.17dB/km, be preferably in 1550nm at 1550nm less than about 0.16dB/km.

In the another embodiment of the invention, the zero-dispersion wavelength of single-mode fiber better is about 1350nm-1450nm, and zero-dispersion slop is less than about 0.10ps/nm ²/ km better is about 0.035ps/nm ²/ km-0.10ps/nm/km; Total dispersion at 1550nm is about 1ps/nm/km-6ps/nm/km.The cutoff wavelength of this optical fiber is better less than about 1400nm, better less than about 1300nm.Preferably, optical fiber is about 45-75 μ m at the useful area of 1550nm ²The alkalimetal oxide adulterating method that adopts this paper to disclose, the decay of the optical fiber of making according to this embodiment at 1310nm less than about 0.30dB/km, at 1550nm less than about 0.18dB/km; At 1550nm better less than about 0.17dB/km; Better less than about 0.16dB/km.

In another embodiment, the core of optical fiber comprises alkalimetal oxide, and its covering comprises alkalimetal oxide and F.Preferably, alkalimetal oxide is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂O and their mixture; Better, alkalimetal oxide is selected from K ₂O, Rb ₂O, Cs ₂O and their mixture; Preferably alkalimetal oxide is K ₂O or Rb ₂O.The peak volume of alkalimetal oxide should be greater than about 0.001 weight % but less than about 0.4 weight % in the fiber cores; Better greater than 0.001 weight % but less than about 0.15 weight %; Preferably be about 0.005 weight %-0.15 weight %.

As known to those skilled in the art, the ability of making prefabricated component and forming the relative quantity of control alkalimetal oxide in prefabricated component in the process of optical fiber subsequently to optical fiber in distribution and its propagation characteristic of last alkalimetal oxide very important.Can be before the prefabricated component wire drawing be become optical fiber, according to preset time and temperature operation table prefabricated component is heat-treated and to reach above-mentioned control.Some situation requires alkalimetal oxide is retained in the core of optical fiber and limits alkalimetal oxide to be diffused into covering.This can following method reach, and promptly by the fiber cores prefabricated component that be substantially free of chlorine of formation with the adulterated cladding glass coating of F-, and before this prefabricated component wire drawing is become optical fiber it is heat-treated.For example, have been found that when in 1000-1600 ℃ temperature range, heat-treating K ₂O is at the about soon 10-100 of the diffusion of diffusion ratio in pure silicon dioxide times of fixed F-doped silica glass.Therefore, heat-treat and advantageously to make K having the fiber cores that contains the F covering ₂The O rapid diffusion is by cladding glass, but its concentration is very low for alkali metal oxide concentration in the core of fibre-optical preform.Therefore, can reach the low scattering in the core of the optical fiber that is drawn by this prefabricated component, avoid high scattering simultaneously, this high scattering may be followed quantitatively similarly F and K ₂The concentration of O and F and K ₂The O colocated is at optical fiber the same area.Preferably, prefabricated component is at least about the thermal treatment 6 hours at least of 1000 ℃ temperature; Better, prefabricated component thermal treatment under at least about 1400 ℃ temperature; Preferably prefabricated component thermal treatment under at least about 1600 ℃ temperature.Better, to prefabricated component thermal treatment at least 30 hours.Preferably, the fibre-optical preform covering comprises F.After the thermal treatment, can adopt conventional drawing process, with the fibre-optical preform drawing optic fibre.

Also advantageously controlled the diffusion of the alkalimetal oxide in the drawing process.Have been found that by changing drawing condition according to predetermined way the concentration distribution that alkali metal oxide dopant can be on request is dispersed in the whole prefabricated component.Preferably, alkali metal oxide dopant is to spread with the relative linear relationship of radius.Heat treating method and drawing process before the above-mentioned wire drawing are compared, be shown in Fig. 9.Fig. 9 carries out 6 hours K after the thermal treatment at 1500 ℃ to fibre-optical preform before showing wire drawing ₂O is concentration radially, by curve 80 expressions, and K in the fibre-optical preform after 2000 ℃ of wire drawings ₂O concentration, curve 82 expressions.The initial K of estimation also is shown ₂The O concentration distribution, by curve 84 expressions, and initial F concentration, by curve 86 expressions.Core-covering interface is by dotted line 88 expressions.Clearly illustrate as figure, though heat treated K before the wire drawing ₂O concentration distribution 80 is presented at core-covering interface 88 bigger loss, but the K that drawing process produces ₂The O concentration distribution shows more near linear distribution.Preferably, alkali metal oxide concentration descends with radius.Because the diffusion part of alkali metal oxide dopant depends on the temperature of doped-glass, and in the time that glass keeps this temperature, these factors play a significant role to the diffusion of alkalimetal oxide in the control drawing process.Fibre-optical preform (with the optical fiber that is drawn by this prefabricated component) present temperature and time in drawing process can be controlled by changing drawing speed, wire drawing (stove) temperature and optical fiber tension force.For example, improve the residence time of specific part in fiber drawing furnace that drawing speed can reduce fibre-optical preform, therefore can shorten the distance that alkali metal oxide dopant spreads on the optical fiber transverse section that fibre-optical preform promptly draws.This can make less alkalimetal oxide be diffused into covering, therefore, the alkalimetal oxide of high density is arranged in fiber cores.On the contrary, reduce drawing speed and increased the residence time, therefore, the covering that further is diffused into optical fiber owing to alkalimetal oxide causes alkali metal oxide concentration decline in the fiber cores.Can improve the velocity of diffusion of alkalimetal oxide with the same manner rising fiber drawing furnace temperature, reduce alkali metal oxide concentration.As a result, can use drawing speed and furnace temperature effectively to control the distribution of alkalimetal oxide in the optical fiber that spreads and make.Figure 10 shows and improves the drawing condition that alkali metal oxide concentration adopted on the fibre diameter.Figure 10 be illustrated in by on the part of three fibre diameters that draw after the same fibre-optical preform wire drawing as the K of function of position ₂O concentration (90,92 and 94).The optical fiber of representing with reference numbers 90 is to carry out wire drawing with 15m/s and 200g tension force.The optical fiber of representing with reference numbers 92 is to carry out wire drawing with 15m/s and 90g tension force, and the optical fiber of representing with reference numbers 94 is to carry out wire drawing with 9m/s and 90g tension force.To K shown in Figure 10 ₂The relatively demonstration drawing speed that O concentration 90,92,94 is carried out drops to 9m/s from 15m/s, by curve 92 and 94 expressions, causes K respectively ₂The O peak concentration descends.More significantly, tensile stress is increased to 200g from 90g, as comparison curves 92 and 94 and curve 90 shown in, it is about 30% to show in the fiber cores that the peak volume of alkalimetal oxide increases, as curve 90 expressions.It is believed that K ₂O radially outward is diffused into the covering of optical fiber from the fiber optic hub district.Though can not directly confirm K the covering from Figure 10 ₂O concentration increases, but we believe that the raising to measurement sensitivity and the scanning of the mensuration on the full diameter of optical fiber subsequently will show that such concentration increases.

Shown in Figure 11 is first method 102 according to embodiment of the present invention, makes the optical fiber of alkali doped by the alkalimetal oxide precursor that to be diffused into suitable silica glass goods be optical fiber.The first step 104 of display packing 102 in Figure 11 and 12, and describe with reference to these figure.Preferably, will be applicable to that at first the silica glass tube 106 of making optical fiber is installed in the chuck of lathe 101 (as the lathe or the conventional lathe through the glass that improved chemical vapour deposition (MCVD) forms of processed glass).Method is forming the preferred toroidal memory (reservoir) 108 that is used for accepting alkali metal source compound 110 near pipe 106 1 ends below adopting, promptly operate in and forge two ring neck shapes deformation 112 on pipe 106 the tube wall, perhaps this storer is welded on this pipe by flame.Also can adopt the storer of other type.Preferably, two ring neck shapes deformation 112 2cm that is separated from each other.Pipe 106 can also comprise the independent doping agent or the doping agent of combination.This doping agent can comprise, for example F, Al ₂O ₃, CaO, GeO ₂, P or other improve the doping agent of specific refractory power.Specifically be that pipe can comprise uses GeO ₂Adulterated SiO ₂, for example form the part of core of the single-mode fiber of step-refraction index.Before alkalimetal oxide is diffused into this pipe, add additional silica glass at the internal surface of Glass tubing 106 by chemical vapour deposition.Additional glass also comprises above-mentioned doping agent like this.But, for preventing the basic metal crystallization, require pipe 106 and be deposited on this any other glass of managing 106 inwalls not chloride basically.To not chloride substantially, we refer to that cl content is enough low, can avoid because the light loss that the alkali metal chloride crystallization causes.For this purpose, require cl content better less than about 500 ppm by weight; Better less than about 100 ppm by weight; Preferably less than about 50 ppm by weight.In addition, silica glass tube 106 and any other glass of being deposited on this Glass tubing should not contain " water " substantially.To " water ", we refer to hydroxyl OH.Water has an absorption peak at 1383nm or about 1383nm, and this absorption peak may extend into the operation wavelength district of optical fiber.This peak produces deleterious effect to optical fiber attenuation.Therefore, require to reduce this absorption peak, be also referred to as the water peak by the OH content that reduces glass as far as possible.Preferably, Glass tubing 106 contains the OH less than about 100 weight ppb; Better less than about 20 weight ppb.For guaranteeing that the initial glass goods are substantially free of water before the diffusion alkali metal oxide dopant, in making the silica glass tube process, adopt chlorine desiccating method commonly used.But, should be with using the minimum of reducing to of chlorine, to reduce the cl concn of glass.In porous soot glasswork situation, after the chlorine drying, should adopt goods are exposed to fluorine-containing atmosphere (fluorine purging) as CF ₄Or SiF ₄, or carry out drying in their combination, or replace the chlorine drying with above-mentioned fluorine gas atmosphere drying.Be exposed to fluorine-containing atmosphere (fluorine purging) under about 1100 ℃ temperature being lower than, to avoid the high-load fluorine that in glass, mixes.Require the fluorine of doping low levels, i.e. 0.1-0.4 weight % fluorine for example.Preferably, become the water-content of glass of core of optical fiber less than about 100 weight ppb, better less than about 20 weight ppb.

Again referring to Figure 12, in case make silica glass tube 106, comprise the deposition of any additional glass after, alkali metal source compound 110 is imported in the pipe 106 of storer 108, and with heating source 114 heating, formation steam when swivel pipe 106.Oxygen or carrier gas be by the import 116 of rotary seal 118 inflow pipes 106, heats managing 106 parts 120 in the downstream in alkalimetal oxide source 110, is diffused into the internal surface 122 of pipe 106 to promote alkalimetal oxide.Preferably, do not insert any prefabricated component parts such as another glass stick etc. in the pipe 106.Pipe 106 parts 120 in 110 downstreams, alkalimetal oxide source should be heated to is enough to promote basic metal to be diffused into surface 122 rapidly, and prevents to make the opaque temperature of glass.Preferably, be heated above 1500 ℃ with 124 pairs of pipes of heating source, 106 parts 120 in 110 downstreams, alkalimetal oxide source; Better be about 1500-2000 ℃.Preferably, heating source 124 is across the length of the part 120 of pipe 106.Alkalimetal oxide source 112 should comprise the element that is selected from K, Na, Li, Cs and Rb.Preferably, alkalimetal oxide source 110 is bromide, iodide or fluorochemical.Best, alkalimetal oxide source 110 is KBr, KI or KNO ₃Alkalimetal oxide (as, K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂O, and their mixture) better be diffused into the degree of depth of about 100-500 μ m from managing 106 internal diffusion surface 122, carry out the Glass tubing that burning shrinkage forms alkali metal oxide-doped before to managing 106.Particularly, the alkali metal oxide dopant concentration (weight %) that spreads in the preferred pipe is in radial variations.Preferably, glasswork (as managing 106) is mixed, shown in the enlarged view of Figure 12, make in the concentration of half part 107 of inside the highlyest, the concentration of half part 109 externally is lower.Be defined in the division points between half outside the interior half-sum, and be positioned at half place (by dotted line 111 expressions) by the radius thickness of pipe 106.For example, diffusion should make the alkali-metal-doped agent outside the peak concentration in half part 109 less than 50% of the peak concentration (weight %) of interior half part 107.

After the diffusion process, adopt ordinary method known in the art (or drying means as herein described) to managing 106 further heating, promote the part burning shrinkage of pipe 106, with the internal surface area that can loss after reducing alkalimetal oxide and passing through and the thickness of the layer that alkalimetal oxide has been spread in increase.In case after finishing the diffusing, doping step or managing 106 any part burning shrinkage, can choose wantonly with the etching reagent that is fit to remove silica glass the diffusing surface 122 of pipe is carried out etching, be etched to the undesirable impurity degree of depth that is enough to remove the diffusing surface 122 that may diffuse through pipe 106.For example the HF aqueous solution can be used as etching reagent, better, can use fluoride gas, for example CF ₄, SF ₆, NF ₃, C ₂F ₆, or their mixture.The amount of removing from internal surface 122 depends on the treatment condition of diffusion and any part burning shrinkage process, and preferred etching condition can be enough to remove glass from surperficial 122 to the degree of depth at least about 5% of total diffusion depth of alkalimetal oxide.Shown in the step 126 of method 102, in case finish etching, further heat with 124 pairs of silica glass tubes 106 of heating source, with the pipe 106 of burning shrinkage in 110 downstreams, alkalimetal oxide source, and the solid glass rod 132 of formation alkali metal oxide-doped.According to ordinary method known in the art,, come burning shrinkage pipe 106 as heating with suitable heating source (as blowtorch).Then, cut out the solid glass rod 132 of alkali doped from the glass part of alkali metal containing source compound storer 108.Preferably, the solid glass of alkali metal oxide-doped rod carries out etching with suitable etching reagent, removes the some or all hydrated glasses that form by blowtorch in burning shrinkage pipe 106 processes.If use heating source to carry out burning shrinkage, for example, induction heater or resistance heater, plasma torch, or the dry heat source of using hydrogen-containing fuel not such as CO then do not need to carry out etching.It is believed that in doping and/or burning shrinkage step and adopt the dry heat source can make the outside rewetting profit minimum of pipe, that is, OH (water) diffuses into pipe from the outside minimum, therefore can further reduce optical fiber attenuation.The dry heat source is can be with the heating source of OH (water) inlet tube of any perceived amount.

For example, shown in Figure 29 is the diffusing, doping machine tool 501 that is used for alkali-metal-doped, and wherein, the heating source 524 that is used at diffusion and burning shrinkage process heating tube 506 is induction heaters of installing near pipe (better being to surround pipe).Glass tubing 506 is installed (more fortunately in the chuck 517) with respect to frame 502, and rotates in frame.Carrier gas is (as O ₂) better from the supply of source (not shown) and by import 116 and rotatable sealing 118 inflow pipes 506.The alkali metal source compound of carrier gas in container 508 (as, KBr, KI or KNO ₃) on flow through, this container by interconnecting tube or be connected by welding to the pipe 506.With heating source 514, for example resistance heater or induction heater or blowtorch while heating container and alkali metal source compound (better to 800-1000 ℃) so for example can make alkali metal vapour be entrained in the carrier gas, thereby form alkali-metal-doped agent gas.With induction heater 524 heating glass pipes 506, this glass is exposed to dopant gas simultaneously, makes the alkali-metal-doped agent be diffused into Glass tubing 506.At diffusing step, well heater 524 vertically moving around along rod 506 by suitable motor and driving mechanism (not shown).In case finish the basic metal diffusing step, further apply enough heats (as mentioned above) by heating source 524, come this Glass tubing 506 of burning shrinkage, form the glass stick of alkali doped.

Induction heating source 524 (as shown in figure 30) comprises annular graphite susceptor (susceptor) 515 of having surrounded Glass tubing 506 (shown in prune top) and the coil 513 that surrounds this inductor block.Coil 513 is electrically connected with tank circuit 518.Induction heater 524 is installed in tank circuit 518, and this circuit moves on slide block, makes heating source 524 across the surface at pipe 506.When induced power being supplied with this tank circuit, the coil 513 in the well heater 524 obtains voltage, and causes eddy current in inductor block 515, thereby heats this inductor block (and so heating tube 506).Inductor block is supported by end pieces 520 and separates with pipe.Glass tubing 509 is more fortunately around the inductor block 515, as electrical insulator and to the physical support of this subassembly, makes inductor block can be immersed in inert gas (as by arrow " I " expression).Particularly, inductor block 515 has surrounded and has managed 506 first intervals 511 that also form between pipe and the inductor block.Equally, glass sock 509 has surrounded inductor block 515, and forms the interval of second between this cover and the inductor block 516.Rare gas element such as argon gas flow out by passage 519 from the source (not shown), this passage with 511 be connected at interval with 516, the encirclement inductor block is provided and prevents the rare gas element of its oxidation.516 better be filled with the porous graphite felt at interval.

Will be appreciated that, the rod 132 of the alkali doped of burning shrinkage better comprises the alkali metal oxide concentration of (being similar to pipe 106) radial variations, and the alkali-metal-doped agent that makes this rod have peak-peak concentration (weight %) corresponding to the part of interior half part 107, have than low peak concentration corresponding to the part of outer half part 109.The peak concentration of best alkali-metal-doped agent is at the center (shown in Figure 17 and 18) of rod, and the concentration at half place of radius is less than 50% of peak concentration; Better less than 25%.Best, there is not any tangible alkali metal oxide dopant at the radius outermost layer 171 (Figure 17,18) of rod.Preferably, the thickness of this outermost layer 171 of having avoided the alkali-metal-doped agent is more than or equal to 1.0mm, and thickness is greater than 25% of excellent outside radius preferably.Find, if on rod, exist the layer of alkali-free metal dopant to reduce when having chlorine in the processing in the back crystalline tendency on excellent interface.

According to the optional step 128 of method 102, in further procedure of processing, the rod 132 of alkali doped is being heated and is being drawn into the less glass stick 144 of diameter less than the glass stick of original alkali doped in the fiber drawing furnace 136 again.This drawing process is shown in Figure 13.On the glass stick 132 of the alkali doped that above-mentioned burning shrinkage step forms, fix a glass handle 130, the glass stick 132 of alkali doped is installed in the reinforced support 134 that moves that is arranged in above the conventional fiber drawing furnace again 136 downwards.The glass stick 138 of protection usefulness that is fixed on glass stick 132 bottoms of alkali doped can carry out tractive with the traction apparatus 140 that motor drives, and with proper speed the glass stick 132 of alkali doped is carried out wire drawing.Have been found that 15-23cm/min is suitable speed, can control this speed significantly according to the diameter that transmitter 142 is measured.The outside diameter (dl) of the small diameter glass rod 144 that this drawing process forms is preferably 3-10mm; Better less than 6mm.If the diameter of the rod 132 that burning shrinkage step 126 forms is within the scope that requires, the rod 132 that forms in the burning shrinkage step 126 can be used as glass stick 144.The K of small diameter glass rod 144 ₂The O peak concentration should be required K in the fiber cores of optical fiber when carrying out wire drawing ₂About 5-10 of O peak concentration times, to remedy the obvious migration of alkali-metal-doped agent in the drawing optical fibers process.For example, if require K in the fiber cores ₂The O peak concentration is 0.4 weight %, the then K of small diameter glass rod 144 ₂The O peak concentration should preferably about 2-4 weight %.Particularly, the rod of the very minor diameter of alkali doped has superiority, because the transition metal impurity that exists in the rod can be concentrated on like this near the fiber optic hub line, and centerline negative impact minimum.It should be understood that the peak concentration in the optical fiber can be littler 100 times than the peak concentration of small diameter glass rod owing to add big quantity of material in adulterated covering.Shown in the step 146 of method 102, in a single day form small diameter glass rod 144 according to the method, form subassembly by the centre hole that for example glass stick 144 is inserted fibre-optical preforms 150, can further coat glass stick 144.Preferably, as shown in figure 14, fibre-optical preform 150 is porous and comprises the glass soot.Among Figure 14, the alkali doped glass stick 144 of minor diameter is inserted the centerline hole of sintered glass soot core body prefabricated components 150, shown in arrow 152, form compound prefabricated subassembly 155.Can adopt ordinary method to make sintered glass core prefabricated component 150.For example, porous soot core prefabricated component 150 can adopt outside CVD (Chemical Vapor Deposition) method manufacturing, is about to soot and deposits on the target rod.From porous glass preform, remove this target rod, stay the centre hole 148 of the medullary ray extension of vertically passing through prefabricated component 150.Porous core prefabricated component 150 can comprise one or more doping agents that improves specific refractory power, as germanium oxide (GeO ₂).Porous optical fiber prefabricated component 150 can only contain a core glass soot, or the porous optical fiber prefabricated component can comprise core glass soot 149 and cladding glass soot 143, wherein, the dividing line between core body and the cladding glass soot, considerable change illustrates with dotted line 141 in promptly forming with respect to covering mensuration.In other words, move inward from the prefabricated component outside, the beginning of physics core is represented in first considerable change of component.

Figure 15 is the example of an employing with reference to the fibre-optical preform of method 102 manufacturings of Figure 12 description.Concrete, the pipe of the silicon-dioxide soot of doping germanium oxide can adopt the manufacturing of conventional OVD method,, the silicon-dioxide soot that contains of doping germanium oxide is deposited on a live spindle that is, forms the pipe of the silicon-dioxide soot of doping germanium oxide.Remove axle, the pipe with the silicon-dioxide soot of doping germanium oxide is exposed in the atmosphere containing chlorine then, comes dry this soot pipe.The pipe of dried soot better carries out fluorine and purges (by being exposed in the atmosphere that contains F), removes the chlorine of major part (better being nearly all), (as following detailed description with reference to Figure 25).Fixed then this soot pipe forms the silica containing Glass tubing of vitrifying of doping germanium oxide, contains preferably greater than 4 weight %GeO ₂Randomly, Glass tubing is stretched again, become the more intermediate pipe of minor diameter.In step 104, use alkalimetal oxide then (as K ₂O) to comprising silicon-dioxide and germanium oxide (GeO ₂) Glass tubing (containing the intermediate pipe) mix, and carry out burning shrinkage in step 126, form the larger-diameter solid silica glass plug that is doped with basic metal and germanium oxide.This larger-diameter solid glass plug can be in optional step 128 again wire drawing become the glass plug 144 of minor diameter, its diameter is above-mentioned preferred diameter (d1).Then, the minor diameter glass plug 144 that comprises doping germanium oxide and alkali-metal silicon-dioxide further coats, promptly shown in the step 146 of Figure 11,, form the composite fiber prefabricated component by should rod inserting the centre hole of sintered glass soot fibre-optical preform 150.Porous soot fibre-optical preform 150 better also is included in the doping germanium oxide (GeO on the annular inner portion 149 of soot prefabricated component 150 of the outer layer segment of representing core ₂) the silicon-dioxide soot and the silicon-dioxide soot (better unadulterated basically silicon-dioxide soot) of the germanium oxide that on the outer ring portion 143 of the soot prefabricated component 150 of representing clad section, do not mix.It is dry and be cemented on the small diameter glass rod that this composite fiber prefabricated component 145 carries out suitable chlorine in step 164, forms fixed fibre-optical preform (being elaborated with reference to Figure 25).Before fixed, adopt optional fluorine to purge, remove the residual chlorine in the soot prefabricated component 150.Preferably by making prefabricated component 150 be in the fluoro-gas of about 1000-1150 ℃ temperature (as SiF ₄Or CF ₄Gas) middle about 90-150 minute, carry out fluorine and purge.The chlorine that exists in removing (purging out) soot prefabricated component basically, fluorine purges and can also be 0.1-0.4 weight % at interior layer segment a spot of fluorine that mixes slightly.To fixed we refer to heat the sintered glass soot to making glass soot cohesion, thereby form the temperature of the glass of solid transparent.The further wire drawing again of core prefabricated component rod of alkali doped forms the second glass plug goods 144, shown in step 166.It should be understood that the glass stick goods 144 after the doping comprise the diameter d that has corresponding to fiber cores _CoreFirst part 145, this part comprises the alkali-metal-doped agent of high density, and has the encirclement part 147 (referring to the enlarged view of Figure 14) corresponding to the d1 of the diameter of the interior layer segment of covering.Preferably, d _CoreBe less than or equal to 0.5 times of dl, some part of covering is included in the excellent goods.The second leg 144 is coated by silica containing glass again, and the final wire drawing prefabricated component of fixed formation.Best, adopt OVD or the rod method (being about to rod inserts in the silica containing glass soot pipe) in soot to coat, and carry out fixed, but can also comprise rod is inserted in the glass sock, form final fixed wire drawing prefabricated component with final outside dimension diameter (d2).Preferably, the outside dimension of glasswork rod 144 (d1) is less than or equal to 0.06 times of final outside dimension (d2) of final fixed wire drawing prefabricated component (better, be less than or equal to 0.03 times of final outside dimension (d2)), thus alkali-metal-doped agent (alkalimetal oxide) is concentrated near the center of prefabricated component.

Adopt electron microprobe(EMP) that the fixed fiber cores prefabricated component of making is measured.Curve 153,155 among Figure 15 is illustrated in the GeO on the fixed prefabricated component diameter ₂And K ₂The example of O concentration.Dotted line 157 and 159 marks the border between small diameter glass rod and the fixed soot.Final wire drawing prefabricated component carry out fixed after, then in step 170, adopt conventional wire-drawing frame and method or apparatus and method as herein described, be drawn into the optical fiber (for example, referring to Fig. 1) of alkali doped and germanium oxide from this consolidated combination part.

According to the described another kind of method of reference Figure 16, the glass stick 144 of minor diameter alkali doped can be used as initial rod, and is known as those skilled in the art, adopts the OVD method, and the additional sintered glass soot of deposition 162 forms subassembly 160 as coating layer on this rod.Figure 16 illustrates typical outside vapour deposition process.As shown in figure 16, a glass handle 154 is installed on the glass stick 144 of the minor diameter alkali doped of making according to the method described above, this handle becomes an integral part of the prefabricated component of making.Handle 154 provides the method for supporting of the silica glass prefabricated component that in the procedure of processing of back sedimentation is formed.The glass stick 144 that will have fixed handle 154 is installed on the lathe, and with respect to burner 156 rotation and translations, this burner can be those that for example disclose in the United States Patent (USP) 4,165,223 to glass stick in lathe.Fuel gas and oxygen or air are from source of the gas (not shown) supplied burner 156.This mixture burns produces from the flame of burner 156 emissions.The oxidation in flame of the mixture of silica precursor gas-steam, formation contain silicon-dioxide soot stream 158, are directed to glass stick 144.Appropriate device to burner 156 delivering gas-steam mixture known in the art; Can be to the reference of this device explanation referring to United States Patent (USP) 3,826,560,4,148,621 and 4,173,305.Burner 156 generally operating under the condition like this, promptly provides rational high sedimentation velocity and efficient, makes the soot that forms on the burner face minimum simultaneously.Like this under the condition, from the size in the flow velocity of burner aperture effluent air and reactant and these holes and position and their axial orientation accumulative soot stream 144 is flowed from burner 156 towards glass stick.Mode formed below compound soot prefabricated component 160 adopted, and promptly by glass stick is crossed burner 156 more than 144 time, made the formation multilayer contain the silicon-dioxide soot, to form soot coating 162.By move forward and backward burner 156 or the combined translational motion by burner 156 and glass stick 144 along rotary glass rod 144, also can reach this translational movement.Soot coating 162 forms at least one part of the core glass of compound prefabricated component 160, and this prefabricated component should comprise pure basically silicon-dioxide.Preferably, the density of soot coating better is about 0.35g/cc-0.5g/cc greater than 0.35g/cc.Then, compound prefabricated component 160 is exposed to and carries out drying in the chlorine-containing gas, in the step 164 of method 102, and at the stove internal heating, fixed this compound prefabricated component 160, the fixed fiber cores prefabricated component of formation transparent solid glass.

Can be according to United States Patent (USP) 4,165,223, or compound prefabricated component is carried out drying and consolidation step with reference to the described method of Figure 25, form the fiber cores prefabricated component.In consolidation step, compound prefabricated component should carry out fluorine and purge, and the unwanted chlorine that provides at initial drying step is provided.This purge step comprises in the exposure fluoro-gas, but has only added small amount of fluorine (for example 0.1-0.4 weight %) in this gas.In the process of the above-mentioned step 162 that is similar to method 102, this transparent glass core prefabricated component is carried out wire drawing more then, form second plug, promptly comprise glass stick by at least a portion of its fiber cores that is drawn into.Second plug also comprises at least a portion of cladding glass.Shown in the step 168 of method 102, second plug can also further be processed by adding additional glass, or for example deposit the glass soot by cover envelope or electroless plating simultaneously by chemical vapour deposition, or by other method known in the art, reach with Glass tubing (pipe of Glass tubing or soot) cover envelope, form the fibre-optical preform of finishing that is drawn into optical fiber easily.Additional glass comprises core glass, cladding glass or the two.In addition, additional glass can meet the requirements of thickness by several other deposition steps, wherein, after each step, with the soot drying, doped with fluorine, fixed and be drawn into the more rod of minor diameter again.Mainly form (can comprise small amount of fluorine) situation at core by the alkali-metal silicon-dioxide that mixed, additional glass is by the interior radially part (can comprise small amount of fluorine) of not carrying out doped silica basically with by sinking to doping (flood doping) (referring to US 4,629,485) fully the outer radial of doped with fluorine part (corresponding to the covering of optical fiber) is formed.Better fully mix, the relative refractive index Δ % between core and covering for example reaches greater than 0.2%, is 0.30-0.40% better.Especially, to each other step, moat shape (moat) silicon-dioxide (corresponding to the additional glass of fibre cladding) joins in the second leg by deposition, and such moat shape is silica-doped fluorine.Moat shape soot at first carries out drying with chlorine-containing gas, is exposed to fluoro-gas (as, SiF at 1225 ℃ then ₄Or CF ₄) middle 60-120 minute, then, fluoro-gas exists down more fortunately, with the speed of 7-10mm/min, is undertaken fixed by hot-zone (1450-1500 ℃) downwards.This prefabricated component wire drawing again forms the third leg, and can repeat these steps once more, that is, deposition, drying, doped with fluorine and fixed is up to the final prefabricated component that obtains suitable diameter.Preferably, the weight % of the fluorine in each layer in succession of additional glass in covering (additional glass) is approximately identical, or better, is slightly less than the weight % in (approximately little 0.1-0.5 weight %) outermost covering, and stress is reduced to minimum.After making the fibre-optical preform of finishing of step 168, the drawing optical fibers prefabricated component of finishing is drawn into the optical fiber of alkali metal oxide-doped, shown in the step 170 of method 102.As herein described each time again after the drawing step, rod be exposed to carry out D in the deuterium atmosphere ₂Handle.At GB 2,149,392 and US 4,515,612 and US 4,504,297 in the deuterium processing has been described.

Embodiment 302 according to the another kind of method of the flow chart description of reference Figure 25 forms doping germanium oxide and alkali-metal step-refraction index single-mode fiber.This method 302 more fortunately step 301 comprise at first form the doping germanium oxide contain silica glass soot pipe.The pipe of soot better adopts the OVD method to form, and the silicon-dioxide soot that contains by a certain amount of Germania-doped agent of will mixing is deposited on the live spindle, on optical fiber, meet the requirements of specific refractory power (as, be 0.3-0.4% to step index optical fiber).Remove this axle then and form tubular soot pipe.Then, the pipe of soot carries out drying by following mode in drying step 303, at first with prefabricated component in helium-atmosphere, 1000 ℃ of preheatings 60 minutes.Next, in stove, the pipe of the silicon-dioxide soot of doping germanium oxide is exposed to chloride (as, Cl ₂) in the atmosphere 1000-1150 ℃ about 60-120 minute down.Best, this atmosphere comprises the combination of helium and chlorine-containing gas, and wherein the volumetric flow rate of chlorine-containing gas is less than the volumetric flow rate of helium; Preferably, the volumetric flow rate of chlorine-containing gas is less than 10% of the volumetric flow rate of helium; Better less than 2% (for example, the chlorine-containing gas of the helium of 20SLPM and 0.2SLPM).After chlorine drying step 303, the pipe of exsiccant soot better also carries out fluorine purge step 304, in this step, in the stove with 1000-1150 ℃ of exsiccant Guan Zaiyue, is in fluorine-containing atmosphere and (better comprises CF ₄Or SiF ₄) about 90-150 minute, further dry this prefabricated component.Best, fluorine-containing atmosphere comprises fluoro-gas and rare gas element such as helium.The volumetric flow rate of fluoro-gas is less than the volumetric flow rate of helium; Better the fluoro-gas flow is less than 10% of helium volumetric flow rate; Better less than 5% (for example, 20SLPM helium and 0.4SLPM fluoro-gas).Be lower than this fluorine purge of carrying out step 304 under the consolidation temperature, having only small amount of fluorine (about 0.1-0.4 weight %) to be introduced into and to be doped to the silicon dioxide tube of doping germanium oxide in this processing.Carrying out that fluorine purges is if residual chlorine dose minimum in the soot prefabricated component.

Then, dry and carried out pipe that fluorine purges in step 307, by being in that the hot-zone temperature is arranged is 1450-1500 ℃ and for example containing in the stove of the inert atmosphere of helium (, the soot prefabricated component being moved down), carry out fixed with about 7mm/min speed.The silica glass tube of the doping germanium oxide that this step produces then according to the front referring to the described method of Figure 12, carry out alkali-metal-doped in step 304.Before mixing like this, can also choose wantonly this Glass tubing is placed stretching furnace again, draw and form the more intermediate of the alkali doped pipe of minor diameter.

After the alkali doped, supply with enough heats by heating source, burning shrinkage Glass tubing or intermediate on lathe form the glasswork rod that comprises the silicon-dioxide that is doped with alkalimetal oxide and germanium oxide.Randomly, in wire-drawing frame again, in the step between step 326 and 329, as mentioned above should rod again wire drawing become the more rod of minor diameter.Next, contain on the rod that silica glass adds alkali doped to additional.For example, in step 326, the rod of minor diameter alkali doped and germanium oxide can be inserted among soot prefabricated component 150 (Figure 14), this prefabricated component better has the annular inner portion 149 (corresponding to the outermost layer part of core) of the silicon-dioxide soot of doping germanium oxide and the outer layer segment 143 (corresponding to covering) that better is made of pure substantially (unadulterated) silicon-dioxide soot.The pipe subassembly of this rod in soot carried out the dry and optional fluorine of chlorine purge, and according to the top described same way as of soot pipe to doped with oxygen germanium, the final fixed wire drawing prefabricated component subassembly of fixed formation.At last, draw the single-mode fiber of alkali doped and germanium oxide by this fixed wire drawing prefabricated component; Its representational index distribution is shown in Figure 27.In the optical fiber 310 of alkali doped, core 312 mainly is made up of germanium oxide, fluorine and alkali-metal-doped agent, and covering 316 mainly by unadulterated silicon-dioxide or slightly the silicon-dioxide of doped with fluorine form.Maximum relative refractive index Δ (Δ to the example of the optical fiber 310 made _Maximum) being about 0.43%, the outside radius of core 312 is about 5.3 μ m.

In first group of preferred fiber embodiment, the optical fiber that this paper discloses comprise core and surround core and with the covering of its direct neighbor, wherein, this core has fully non-negative with respect to covering, better is that positive relative refractive index distributes.Preferably, this core comprises germanium oxide.

Some preferred implementation in first group of preferred implementation, core is made up of an independent core ring section, it is central core ring section, surround the covering that also directly is close on this central core ring section, shown in Fig. 1 and 27, and the variation of these illustrative distributions, as have step, sphering, α or a leg-of-mutton distribution, as discussed above, wherein, it is positive refractive index that central core ring section has with respect to pure silicon dioxide ₁(r).Can see that as Figure 27 the relative refractive index of optical fiber can comprise a diffusion afterbody that extends to covering, the absolute value of relative refractive index is less than 0.03%.Other preferred implementation in first group of preferred implementation, core comprises a plurality of core ring sections, as central core ring section with directly be enclosed in the core ring section of first on central core ring section ring, and the covering that directly coats the first ring core ring section, wherein, it is non-negative that central core ring section has with respect to covering, better is positive relative refractive index Δ ₁% (r), wherein the pure silicon dioxide of core ring section of first ring has non-negatively with respect to covering, better is positive relative refractive index Δ 2% (r).

First group preferred embodiment in, core comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide are 20-300ppm, better 20-200ppm.Maximum alkali metal oxide concentration is better less than 50ppm, better less than 10ppm, preferably less than 5ppm in the covering.Each is self-contained greater than 90 weight %SiO for core and covering ₂, better more than or equal to 95 weight %SiO ₂One or more methods manufacturing optical fiber that disclose according to this paper may make small amount of fluorine remain in the core, for example purge prefabricated component with fluorine before introducing alkalimetal oxide, or the result of the part of prefabricated component.Core better comprises less than 0.2 weight % fluorine, and is better less than 0.1 weight % fluorine, in some preferred implementation, not fluorine-containing.Core better comprises the chlorine less than 3000ppm, better less than 2000ppm chlorine, and in some preferred implementation, owing to the result that one or more methods that disclose according to this paper are made, comprises the chlorine of 500-2000ppm.

First group in some preferred implementation, core comprises germanium oxide and a kind of K of being selected from ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 20-300ppm, is preferably 20-200ppm, is preferably 30-150ppm; In different preferred implementations, core also comprises＞0.2% peak value relative refractive index, Δ _Maximum, in other preferred implementation, core also is included as the peak value relative refractive index of 0.2-0.5%, Δ _Maximum, in other preferred implementations, core also is included as the peak value relative refractive index of 0.3-0.45%, Δ _Maximum

In other preferred implementation of first group, the optical fiber that this paper discloses comprises independent core ring section, i.e. a central core ring section, directly be coated on the covering on this central core ring section, wherein, it is positive refractive index 1 (r) that core has relative pure silicon dioxide, and core comprises germanium oxide and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 20-300ppm, is preferably 20-200ppm, is preferably 30-150ppm; Described core also is included as the peak value relative refractive index of 0.2-0.5%, Δ _Maximum, being preferably 0.25-0.45%, maximum alkali metal oxide concentration is better less than 50ppm, better less than 10ppm, preferably less than 5ppm in the covering.This optical fiber comprises greater than 90 weight %SiO ₂, better more than or equal to 95 weight %SiO ₂Core comprises better less than 0.2 weight % fluorine, and better less than 0.1 weight % fluorine, in some preferred implementation, core is not fluorine-containing.Core comprises better chlorine less than 3000ppm, better less than 2000ppm chlorine, in some preferred implementation, comprises the chlorine of 500-2000ppm.

In first group other embodiment, the optical fiber that this paper discloses comprises an independent core ring section, promptly central core ring section and surround core and with the covering of its direct neighbor, wherein, core comprises germanium oxide and K ₂O, K ₂The peak concentration of O is 20-300ppm, is preferably 20-200ppm, more preferably 30-150ppm; Core also is included as the peak value relative refractive index of 0.2-0.5%, Δ _Maximum, be preferably 0.25-0.45%, maximum K in the covering ₂O concentration is better less than 10ppm, better less than 5ppm.This optical fiber comprises greater than 90 weight %SiO ₂, better more than or equal to 95 weight %SiO ₂Core comprises better fluorine less than 0.2 weight %, and better less than 0.1 weight % fluorine, in some preferred implementation, core is not fluorine-containing.Better less than the chlorine of 3000ppm, better less than the chlorine of 2000ppm, in some preferred implementation, core comprises the chlorine of 500-2000ppm to core.

According to another kind of preferred method embodiment of the present invention, make the optical fiber of the covering of a kind of silica core with alkali doped and doped with fluorine.As shown in figure 26, method 402 is included in step 401 and forms the pipe of mainly being made up of the silicon-dioxide soot.Unique difference of the described pipe of step 301 of this pipe and Figure 25 is that this pipe better is pure substantially (unadulterated) silicon-dioxide soot, but also may comprise the fluorine that brings when purging except that dechlorination by fluorine on a small quantity.Chlorine drying, fluorine purge, fixed, alkali-metal-doped and burning shrinkage step 403,405,407,404 identical with the described method of Figure 25 with 426, except the rod that forms behind the burning shrinkage is the silicon-dioxide that an alkali doped and fluorine purge the Trace Fluoride (about 0.1-0.4 weight %) of generation.Can choose wantonly to this rod carry out etching and/or again wire drawing be the rod of the alkali doped of minor diameter more.

In step 429, then rod is inserted the pipe (better also carrying out fluorine purges) that contains the silicon-dioxide soot, form the subassembly of rod in soot, the better corresponding remainder that constitutes the silica core of optical fiber of soot pipe wherein.Particularly, the pipe of soot comprises and substantially to the same treatment that rod carried out and the fluorine of basic identical amount; Described rod and pipe comprise that separately fluorine purges the fluorine of the little weight % that produces.The subassembly of this rod in soot carried out drying, better carry out fluorine again and purge, and fixed according to the described same way as of step 331 is carried out in step 431, form fixed subassembly.This fixed subassembly then more fortunately step 466 again wire drawing become the more plug of minor diameter (being called bar sometimes), diameter is about 15mm.Then the silicon-dioxide soot that coats is added on the core bar, for example by OVD, in step 468, on this soot deposition core bar.Then this soot is carried out drying, sink to doped with fluorine (, mentioning in 629,485), and carry out fixedly in step 467, the glass of additional doped with fluorine is added on this fixed subassembly as US4.Doped with fluorine can be carried out in consolidation furnace, is in fluoro-gas (SiF by making soot at 1225 ℃ ₄Or CF ₄) in about 60-120 minute, adulterated soot is fixed when furnace temperature being increased to about 1450-1500 ℃ afterwards, and in the sintering device that this soot is in move down about 7-10 minute.Stop fluorine gas (only using helium) before fixed or carry out at prefabricated component that fluorine and helium combination continue to flow when fixed.At square frame 472 repeating steps 466,468 and 467, add other coating layer, meet the requirements of core/covering ratio.Then, the optical fiber of typical example with covering of the silica core of alkali metal oxide-doped and doped with fluorine can be in conventional wire-drawing equipment and method is carried out wire drawing.402 optical fiber of making are shown in Figure 28 according to the method.This optical fiber 446 comprises a silicon-dioxide covering 450 that comprises the silica core 448 and the doped with fluorine of alkali doped.Core 448 comprises the fluorine from the fluorine purging of little weight %.

In the embodiment of second group of preferred fiber, the optical fiber that this paper discloses comprise a core and surround core and with the covering of its direct neighbor, wherein, core has fully non-negative with respect to covering, is preferably positive relative refractive index and distributes.Preferably, core is substantially free of germanium oxide, better, and core oxygen-free germanium.

In some preferred implementation of second group of preferred implementation, core is by an independent core ring section, it is central core ring section, form with the encirclement core and with the covering of its direct neighbor, shown in the variation that the illustrative of Fig. 1 and Fig. 1 distributes, for example have step, sphering, α or leg-of-mutton distribution, as described above, wherein, to have relative covering be positive refractive index to central core ring section ₁(r).In other preferred implementations of second group of preferred implementation, core comprises a plurality of core ring sections, as central core ring section with directly be enclosed in the first ring core ring section on this central core ring section, directly be coated on the covering that the first ring core axon puts, wherein, it is non-negative that central core ring section has relative covering, is preferably positive relative refractive index Δ ₁% (r), the core ring section of first ring is a pure silicon dioxide, it is non-negative having relative covering, is preferably positive relative refractive index Δ ₂% (r).

In second group of preferred implementation, core comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 20-1000ppm, is preferably 20-700ppm, more preferably 20-500ppm.Maximum alkali metal oxide concentration is better less than 200ppm, better less than 50ppm in the covering.The concentration of the fluorine that this optical fiber comprises is at least 0.02 weight %, and better greater than 0.15 weight %, maximum preferably fluorine concentration is 0.5-0.15 weight %.Core comprises the fluorine of 0.1-0.4 weight %, 0.15-0.4 weight % fluorine more preferably, and in some preferred implementation, be 0.2-0.3 weight %.Core better comprises the chlorine less than 500ppm, better less than 300ppm chlorine, and in some preferred implementation, comprises the chlorine less than 200ppm.Covering comprises the fluorine greater than 0.5 weight %, better greater than 1 weight % fluorine, and in some preferred implementation, is 1-2 weight % fluorine.

In some preferred implementation of second group, core comprises fluorine and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 20-1000ppm, is preferably 20-700ppm, more preferably 20-500ppm is preferably 100-500ppm; Core also comprises the peak value relative refractive index of (with respect to covering)＞0.2%, Δ % (r), and in other preferred implementation, core also comprises the peak value relative refractive index of 0.2-0.5%, Δ _Maximum, in other preferred implementations, core also comprises the peak value relative refractive index of 0.3-0.4%, Δ _MaximumCovering comprises the fluorine of at least 0.02 weight %, and better greater than 0.15 weight % fluorine, and maximum fluorine concentration is 0.5-1.5 weight %.

In other preferred implementation of second group, the optical fiber that this paper discloses comprise an independent core ring section be central core ring section and surround core and with the covering of its direct neighbor, wherein, covering has with respect to the specific refractory power of pure silicon dioxide for bearing, and core comprises fluorine and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 20-1000ppm, is preferably 20-500ppm, more preferably 100-400ppm; Core also comprises (with respect to covering) peak value relative refractive index, Δ _Maximum, be 0.2-0.5%, be preferably 0.3-0.4%, maximum alkali metal oxide concentration is better less than 200ppm, better less than 50ppm in the covering.This optical fiber comprises greater than 90 weight %SiO ₂, better more than or equal to 95 weight %SiO ₂Core better comprises the chlorine less than 500ppm, better less than 300ppm chlorine, and in some preferred implementation, comprises the chlorine less than 200ppm.

Other preferred implementations at second group, the optical fiber that this paper discloses comprise an independent core ring section be central core ring section and surround core and with the covering of its direct neighbor, wherein, covering has relative pure silicon dioxide and is negative refractive index covering, and core comprises fluorine and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, the peak concentration of alkalimetal oxide is 100-400ppm, is preferably 200-300ppm; Its SMIS also comprises (with respect to covering) peak value relative refractive index, Δ _Maximum, be 0.2-0.5%, be preferably 0.3-0.5%, better 0.3-0.4%, maximum alkali metal oxide concentration is better less than 200ppm, better less than 50ppm in the covering.This optical fiber comprises greater than 90 weight %SiO ₂, better more than or equal to 95 weight %SiO ₂Core better comprises the chlorine less than 500ppm, better less than 300ppm chlorine, preferably less than 200ppm, and in some preferred implementation, comprises the chlorine less than 50ppm.

Other preferred implementation at second group, the optical fiber that this paper discloses comprise an independent core ring section be central core ring section and surround core and with the covering of its direct neighbor, it is that positive index distribution is negative index distribution with relative pure silicon dioxide that this core ring section has relative covering, wherein, covering has relative pure silicon dioxide and is negative index distribution, described core comprises fluorine and potassium oxide, and the peak concentration of potassium oxide is 100-400ppm, is preferably 200-300ppm; Core also comprises (with respect to covering) peak value relative refractive index, Δ _Maximum, be 0.2-0.4%, be preferably 0.3-0.4%, maximum oxidation potassium concn is better less than 200ppm, better less than 50ppm in the covering.This optical fiber comprises greater than 90 weight %SiO ₂, better more than or equal to 95 weight %SiO ₂Core better comprises the chlorine less than 500ppm, better less than 300ppm chlorine, preferably less than 200ppm, and in some preferred implementation, comprises the chlorine less than 50ppm.

In the 3rd group of preferred implementation, a kind of optical fiber comprise core and surround core and with the covering of its direct neighbor, described core comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture wherein, is deposited on core near the longitudinal center line; This optical fiber comprises the impurity in the zone, bosom that is limited to core basically.The decay of optical fiber 1550nm is less than 0.20dB/km, better less than 0.19dB/km, better less than 0.185dB/km, preferably less than 0.180dB/km.Preferably, core comprises the OH less than about 100 weight ppb.Preferably, the peak concentration of described impurity in the district of bosom than optical fiber in the concentration big at least 20% of any impurity of this bosom district outside part; In some embodiments, the impurity concentration of this bosom district outside part is zero in the optical fiber.Described impurity can be to be selected from transition metal, crystalline alkali metal compound, adsorptive (occlusion), their combination or the impurity of mixture.

In some embodiment of the 3rd group, optical fiber comprise core and surround core and with the covering of its direct neighbor, described core comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, wherein, core is deposited near the longitudinal center line, described core comprises the bosom district of the transition metal that contains peak concentration, and the maximum transiting metal concentration that optical fiber had outside this bosom district is less than 20% of the peak value transiting metal concentration in this bosom district.In different embodiments, the maximum transiting metal concentration outside the district of bosom is zero.Preferably, the bosom district is at this medullary ray and radius between the zone less than 5 μ m.Preferably, at radius greater than the concentration of the transition metal of the All Ranges of 5 μ m less than about 0.01 mole of %.In some embodiments, at the peak concentration of the transition metal in bosom district greater than about 0.1 mole of %.

In other embodiment of the 3rd group, optical fiber comprise core and surround core and with the covering of its direct neighbor, described core comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, wherein, core is deposited near the longitudinal center line, this optical fiber has transition metal peak concentration greater than about 0.1 mole of % at this medullary ray and radius less than the zone between 5 μ m, in radius all parts greater than 5 μ m, the concentration of transition metal is less than about 0.01 mole of %.

In all embodiments of this announcement, optical fiber better comprises first coating that encirclement covering most outer diameter part also directly contacts with it, and surrounds second coating that first coating also directly contacts with it.

In some preferred implementation of the optical fiber of this announcement, described optical fiber also comprises the outermost seal coating of one deck in its outside.This outer gland sealing coating is better surrounded second coating and directly contact with it.In a preferred implementation, comprise doped with oxygen germanium and K at the optical fiber of this announcement ₂The core of O-, surround core and with the covering of its direct neighbor, first coating of surrounding this covering and being in direct contact with it, second coating of surrounding this first coating and being in direct contact with it, and the seal coating that surrounds this second coating and be in direct contact with it.U.S. Patent No. 5,152,817 have described the method and apparatus of the optical fiber of preparation sealing coating.

Embodiment

By top, form doping K with reference to the described method of Figure 11 ₂The glass plug of O.As shown in figure 17, the K of glass plug ₂O concentration 164 is functions of radius, near Gaussian curve.Curve 166 shows the relative refractive index of the relative pure silicon dioxide of glass stick.Be used for K ₂The original tube of O diffusion is pure (unadulterated) silicon-dioxide.Plug has maximum K near excellent medullary ray 168 ₂O concentration is about 1 weight %.Part 171 corresponding to the outer layer segment of rod better should have been avoided adulterated basic metal substantially.Particularly, doping should make the alkali metal concn of outer half part of this rod minimum, and the alkali metal concn of interior half part is the highest.More specifically, the peak concentration of the preferred alkali-metal-doped agent of half outside less than interior half peak concentration 50%; Better less than 25%.

Embodiment 2

Form doping Na by top with reference to the described method of Figure 11 ₂The glass stick of O.As shown in figure 18, the Na of glass stick ₂O concentration 170 is functions of radius, near Gaussian curve.Curve 172 shows the relative refractive index of the relative pure silicon dioxide of glass stick.This rod has maximum Na near center glass rod line 174 ₂ O concentration 170 is greater than 2 weight %.

Embodiment 3

The method that adopts this paper to disclose, and as shown in figure 12, use K ₂O mixes to silicon dioxide tube.Alkali metal source compound 110 is KI.With I to 1100-1200 ℃ of burner 114 Heating K.Burner 124 moves around along pipe 106 with 400mm/min speed forward backward with about 220mm/min speed, up to evaporation alkali metal source compound 110.Downcut storer 108 from managing 106, burning shrinkage pipe 106 forms first glass stick.The etching 13 hours in 49%HF of this first glass stick.Then first glass stick is placed lathe, and the silica glass soot is deposited on first glass stick, form first composite glass product with the outer vapour deposition process of routine.By the fixed doping of routine, this first composite glass product to be carried out fixed, drying and doped F are drawn into second glass stick then.Measure second glass stick with the microprobe that crosses this rod diameter.Figure 19 is illustrated in the K on this second glass stick diameter ₂The curve 176 of O concentration, the curve 178 of Cl concentration and the curve 180 of F concentration.Second glass stick placed on the lathe and the silicon-dioxide soot is deposited on and form second composite glass product on second glass stick.It is fixed to adopt ordinary method that second glasswork is carried out, and dry and F mixes, and is drawn into the 3rd glass stick then.The 3rd glass stick is placed on the lathe, and the silica glass soot is deposited on the 3rd glass stick, form the 4th composite glass product with the outer vapour deposition process of routine.The 4th glasswork is carried out fixed, carries out drying with Cl gas, and during fixed doped F, form the fibre-optical preform (wire drawing prefabricated component) that preparation is used for being drawn into optical fiber.Under 70 gram optical fiber tension force,, this drawing optical fibers prefabricated component is drawn into optical fiber with 7m/s speed.The cutoff wavelength of this optical fiber (measuring on the 2m long optical fibers) is 1150nm, at the 0.17dB/km that decays to of 1550nm.Optical fiber is carried out microprobe analysis, be shown in Figure 20 as the curve of concentration of dopant in the optical fiber of the function of radius, wherein, the K that curve 182 representatives are represented with weight % ₂O concentration, the F concentration that curve 184 representatives are represented with weight %.

Embodiment 4

Another kind of optical fiber is by using GeO ₂Glass stick mixed prepare.This Glass tubing is then by method of diffusion doping K as herein described ₂O, burning shrinkage also is drawn into doping K ₂O-GeO ₂Glass stick.Adopt conventional outside vapour deposition process, deposition glass soot coats this glass stick on glass stick, carries out fixedly then according to routine, forms the drawing optical fibers prefabricated component.This coating soot F that mixed in consolidation process.The wire drawing prefabricated component is drawn into the single-mode fiber of the core with step-refraction index, and this core has about 0.75% peak value relative refractive index Δ %.This optical fiber is at the 0.228dB/km that decays to of 1550nm.This optical fiber is carried out microprobe analysis, be shown in Figure 21 as the curve of concentration of dopant in the optical fiber of the variable of radius, wherein, the K that curve 186 representatives are represented with weight % ₂O concentration, the F concentration that curve 188 representatives are represented with weight %, the GeO that curve 190 representatives are represented with weight % ₂Concentration.

Embodiment 5

According to the present invention to containing GeO ₂SiO ₂The Glass tubing K that mixes ₂O.With this glass stick at H ₂/ O ₂Move around on the burner flame and heat, come this glass stick of burning shrinkage, form solid, diameter is about the major diameter glass stick of 15-17mm.With about 1.5-2cm/min speed burner flame that moves around.Flame temperature is about 2150-2200 ℃.About 8 hours of the outside of major diameter glass stick etching in 49%HF solution.To remove the impurity on rod surface.K in the major diameter glass stick ₂The O peak volume is about 1.5-2 weight %.The major diameter glass stick has the relative refractive index that is about 0.35-0.4% with respect to pure silicon dioxide.Then, adopt conventional drawing process that the major diameter glass stick is drawn, obtain the small diameter glass rod that diameter is about 6mm.The minor diameter sheet glass is cut into several sections.Adopt outside vapour deposition process to make the core prefabricated component of sintered glass soot, wherein, the glass soot is deposited on target compound or the bait rod.This sintered glass soot core prefabricated component comprises the cladding glass soot of core glass soot and at least a portion.In case form porous soot prefabricated component, remove the target rod, stay next hole along the prefabricated component medullary ray.To contain K ₂O and GeO ₂Small diameter glass rod insert the centerline hole of this sintered glass soot prefabricated component, form the first compound prefabricated component.The first compound prefabricated component carries out fixed then in conventional consolidation furnace, forms fixed core prefabricated component.This fixed core prefabricated component carries out wire drawing in the fiber drawing furnace again of routine, form the second glass plug.The second glass plug is cut into a plurality of parts.First mandrel segment is placed a forming of glass lathe, and the additional coating glass soot of deposition forms the second compound prefabricated component on first plug.The second compound prefabricated component carries out fixed in conventional consolidation furnace, forms fixed wire drawing prefabricated component.Adopt ordinary method that this wire drawing prefabricated component is drawn into then and have doping K ₂O and GeO ₂The optical fiber of core.In a comparable manner, the remaining second glass mandrel segment is processed obtaining the wire drawing prefabricated component, and this wire drawing prefabricated component is drawn into optical fiber.Use is measured the light loss (decay) of this optical fiber according to EIA/TIAFOTP-78 spectrum attenuation measurement platform and optical time-domain reflectometry (OTDR) EIA/TIA FOTP-60.Measurement result is listed in the table below 1.In table 1, MFD is illustrated in the mode field diameter of the optical fiber of 1310nm wavelength mensuration, and the cutoff wavelength of optical fiber is according to EIA/TIA FOTP-80, the cutoff wavelength of measuring on the 2m long optical fibers.

Table 1

Optical fiber	Drawing speed (m/s)	At the decay dB/km of 1550nm (OTDR)	At the decay dB/km of 1550nm (spectrum)	The MFD nm of 1310nm	Fiber cut off wavelength (nm)	Zero-dispersion wavelength (nm)	Zero-dispersion slop (ps/nm 2/km)
								1	20	0.1830	0.185	9.55	1508.8	1308.1	0.088
2	20	0.1783	0.176	9.60	1427.4	1309.1	0.088
								3	20	0.1821	0.175	9.25	1518.3	1316.1	0.086
4	10	0.1853	0.184	9.27	1518.7	1317.4	0.086
								5	10	0.1799	0.183	9.31	1302.7	1320.9	0.085
6	10	0.1827	0.182	9.24	1189.5	1322.6	0.084
								7	20	0.1827	0.180	9.37	1200.2	1323.5	0.084
8	20	0.1809	0.177	9.24	1311.1	1318.5	0.085

Embodiment 6

The method that discloses according to this paper is to the first silica glass tube doping Rb ₂O heats and burning shrinkage formation solid glass plug this pipe.Also the method that discloses according to this paper is to the second silica glass tube doping Cs ₂O.Heating also to second glass stick, burning shrinkage formation is doped with Cs ₂The second solid glass plug of O.Electron microprobe(EMP) is traversed the diameter parts of glass stick near its medullary ray, measure doping Rb ₂The glass plug of O and doping Cs ₂The glass plug of O.Each glass stick survey Rb on the diameter ₂O and Cs ₂The concentration of O is shown in Figure 22 and Figure 23 respectively.Among Figure 22, curve 192 is illustrated in the Rb on a part of diameter of glass plug ₂O concentration, curve 194 illustrates the concentration of F.In Figure 23, curve 196 is illustrated in the Cs on a part of diameter of glass plug ₂O concentration, curve 198 illustrates F concentration.

Embodiment 7

Use the plug of the foregoing description 5 to make optical fiber.The index distribution of this optical fiber and K ₂O concentration is shown in Figure 24.Among Figure 24, the index distribution of curve 200 expression cores, curve 202 is expressed as the K of function of radius ₂O concentration.Adopt optical time-domain reflectometry (OTDR) when measuring, this optical fiber is at the 0.1827dB/km that decays to of 1550nm, and is 9.52 μ m in the mode field diameter of 1310nm.Optical fiber also has the cutoff wavelength of about 1519nm, 0.088ps/nm under the zero-dispersion wavelength of 1308.2nm and the zero-dispersion wavelength ²The chromatic dispersion gradient of/km.Optical fiber carries out wire drawing with the 10m/s drawing speed under 150 gram optical fiber tension force.

Embodiment 8

The relative refractive index that Figure 31 illustrates the optical fiber that belongs to first group of preferred fiber embodiment disclosed herein distributes, and this optical fiber is according to method manufacturing shown in Figure 25.Δ _Maximum=0.41%, peak width at half height, HHPW are 4.4 μ m, R _CoreIt is 62.5 μ m places that=7.1 μ m, covering extend to radius.The diffusion hangover extends to covering from 7.1 μ m to about 22 μ m.

Figure 32 illustrates the K that Figure 31 optical fiber is measured ₂O, GeO ₂, F and Cl concentration distribution.Table 2 has been summed up Figure 32.

Table 2

		Core	Covering
				Maximum K 2O	ppm	48	15
Maximum Ge 2O	Weight %	7.6	0.12
				Maximum F	Weight %	0.12	0.03
Minimum Cl	Weight %	0.016	0.08
				Maximum Cl	Weight %	0.12	0.22

Table 3 is listed the mensuration character of the optical fiber of Figure 31 and 32:

Table 3

Length	Rice	7797
			Decay at 1310nm	dB/km	0.326
Decay at 1380nm	dB/km	0.959
			Decay at 1410nm	dB/km	0.454
Decay at 1550nm	dB/km	0.183
			Decay at 1625nm	dB/km	0.193
Mode field diameter at 1310nm	μm	9.52
			Fiber cutoff	μm	1519
Zero-dispersion wavelength	μm	1308
			Chromatic dispersion gradient at 1310nm	ps/nm 2-km	0.088

Embodiment 9,10, and 11

Figure 33 illustrates the K of the optical fiber of embodiment 8 (Figure 31 representative) ₂O concentration distribution, and K in the optical fiber of embodiment 9-11 ₂The concentration distribution of O, embodiment 9-11 roughly is similar to embodiment 8, except K ₂The O dopant distribution.Table 4 is listed the K to embodiment 8-11 ₂The peak concentration of O and K ₂High width of half-peak and the corresponding decay that records that O distributes at 1550nm.Embodiment 11 has minimum K ₂The O peak, minimum K ₂O distributes and the highest decay.Find that the decline of decay is the K that exists ₂The O peak concentration drops to the result less than about 20ppm.

Table 4

		Embodiment 8	Embodiment 9	Embodiment 10	Embodiment 11
						Maximum K 2O	ppm	48	22	19	14
HHPW K 2O	μm	5.4	5.9	5.4	5.8
						Decay at 1550nm	dB/km	0.183	0.179	0.180	0.198

Embodiment 12

Figure 34 illustrate according to belonging to of method manufacturing shown in Figure 26 second group of preferred implementation disclosed herein the relative refractive index of optical fiber distribute.Δ _Maximum=0.33%, the high width HHPW of half-peak is 4.4 μ m, R _CoreIt is 62.5 μ m places that=4.7 μ m, covering extend to radius.K in the core ₂The O mean concns is 250ppm.

Table 5 is listed the mensuration character of the optical fiber of Figure 34:

Table 5

		Embodiment 12
			The spectrum decay
	1310nm	0.289dB/km
				1550nm	0.167dB/km
	1625nm	0.189dB/km
			Chromatic dispersion	λ 0	1296nm
	1310nm	1.19ps/(nm·km)
				1550nm	17.23ps/(nm·km)
	1625nm	21.11ps/(nm·km)
			λ 0Place's slope		0.0861ps/nm 2·km
1550nm place slope		0.0543ps/nm 2·km
			Mode field diameter	1310nm	8.90μm
	1550nm	10.22μm
			Fiber cutoff		1298nm

Embodiment 13-17

Other representational optical fiber of second group of preferred implementation disclosed herein have the index distribution that is similar to Figure 34 according to belonging to of method manufacturing shown in Figure 26.Embodiment 18, and making has high density K ₂The optical fiber of the core of O, and measure.

Table 6 is listed the measured value of embodiment 13-18:

Table 6

Embodiment	13	14	15	16	17	18
							Average K 2O(ppm)	109	176	220	220	222	462
Minimum F (weight %) in the core		0.026	0.14	0.16	0.17	0.12
							Minimum F (weight %) in the covering			1.08	1.17	1.04	1.12
Maximum F (weight %) in the covering			1.43	1.49	1.41	1.49
							Maximum Cl (weight %) in the core		0.013	0.025	0.025	0.022	0.029
The decay at 1310nm place (passing through OTDR) (dB/km)	0.307		0.295		0.295
							The decay at 1550nm place (passing through OTDR) (dB/km)	0.178		0.169		0.171
The decay at 1310nm place (passing through spectrum) (dB/km)	0.307	0.281	0.296	0.295	0.296	0.659
							The decay at 1550nm place (passing through spectrum) (dB/km)	0.178	0.165	0.17	0.169	0.17	0.528

Comparative example 18 has higher measurement decay at 1550nm.

Figure 35 illustrates the K of embodiment 15 ₂The concentration distribution of O, F and Cl.K in the core ₂The O peak concentration is 400ppm, K ₂Maximum half overall with (FWHM) of O concentration distribution is 4.8 μ m.

All be apparent not departing from the various modifications and changes of under the spirit and scope of the invention the present invention being carried out to those skilled in the art.Therefore, the present invention is intended to be included within the scope of appended claims and its content of equal value to modification of the present invention and change.

Claims (98)

1. optical fiber, this optical fiber comprises:

Silicon dioxide base core, described core comprise first doping agent that is selected from germanium oxide, fluorine and their mixture, and are selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration are 20-1000ppm; With

Surround core and with the silicon dioxide base covering of its direct neighbor;

It is characterized in that, in the decay of 1550nm less than 0.185dB/km.

2. optical fiber as claimed in claim 1 is characterized in that, described decay at 1550nm less than 0.18dB/km.

3. optical fiber as claimed in claim 1 is characterized in that, described decay at 1550nm less than 0.17dB/km.

4. optical fiber as claimed in claim 1 is characterized in that described decay is less than or equal to 0.167dB/km at 1550nm.

5. optical fiber as claimed in claim 1 is characterized in that the concentration of alkalimetal oxide descends with fiber radius in the core.

6. optical fiber as claimed in claim 1 is characterized in that, the peak concentration of alkalimetal oxide is greater than about 0.002 weight % but less than about 0.07 weight % in the core.

7. optical fiber as claimed in claim 1 is characterized in that, in the alkali metal oxide concentration of the radius of the spot size that equals optical fiber at least about 0.0001 weight %.

8. optical fiber as claimed in claim 1 is characterized in that described core comprises GeO ₂

9. optical fiber as claimed in claim 1 is characterized in that described core does not contain GeO ₂

10. optical fiber as claimed in claim 9 is characterized in that, described core comprises an independent axle sleeve.

11. optical fiber as claimed in claim 1 is characterized in that, described core comprises a plurality of axle sleeves.

12. optical fiber as claimed in claim 1 is characterized in that, described covering comprises F.

13. optical fiber as claimed in claim 1 is characterized in that, the peak volume of alkalimetal oxide is greater than about 0.002 weight % but less than about 0.05 weight % in the core.

14. optical fiber as claimed in claim 1, this optical fiber also comprises the outer gland sealing coating.

15. optical fiber as claimed in claim 1 is characterized in that, described first doping agent is a germanium oxide, and this optical fiber also comprises the outer gland sealing coating.

16. optical fiber as claimed in claim 1 is characterized in that, described core has graded index and distributes, and this optical fiber is multimode optical fibers.

17. optical fiber as claimed in claim 1 is characterized in that, is 1-6ps/nm-km in the chromatic dispersion of 1550nm.

18. optical fiber as claimed in claim 1 is characterized in that, is 6-15ps/nm-km in the chromatic dispersion of 1550nm.

19. an optical fiber, this optical fiber comprises:

Core, this core comprises GeO ₂Be selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture;

It is characterized in that, select the index distribution of optical fiber, be provided at the total dispersion of 1550nm greater than about 1ps/nm/km, at the zero-dispersion wavelength place less than about 0.10ps/nm ²The chromatic dispersion gradient of/km.

20. optical fiber as claimed in claim 19 is characterized in that, total dispersion at 1550nm greater than about 6ps/nm ²/ km.

21. optical fiber as claimed in claim 19, this optical fiber also are included in the decay of 1550nm less than about 0.18dB/km.

22. optical fiber as claimed in claim 19, this optical fiber also are included in the decay of 1550nm less than about 0.17dB/km.

23. an optical fiber, this optical fiber comprises:

Core, this core comprise and are selected from Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration are greater than about 0.001 weight % but less than about 1 weight %;

Surround core and with the covering of its direct neighbor.

24. an optical fiber, this optical fiber comprises:

Core, this core comprise peak concentration greater than about 0.001 weight % but less than the Rb of about 1 weight % ₂O;

With surround core and with the covering of its direct neighbor.

25. an optical fiber, this optical fiber comprises:

Silicon dioxide base core, this core comprise first doping agent that is selected from germanium oxide, fluorine and their mixture and are selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration are 20-1000ppm; With

Surround core and with the silicon dioxide base covering of its direct neighbor;

It is characterized in that, the relative refractive index peak Δ maximum in the index distribution of core institute tool is bigger by 0.2% than covering.

26. optical fiber as claimed in claim 25 is characterized in that, this optical fiber in the decay of 1550nm less than 0.185dB/km.

27. optical fiber as claimed in claim 25 is characterized in that, in the decay of 1550nm less than 0.18dB/km.

28. optical fiber as claimed in claim 25 is characterized in that, is less than or equal to 0.17dB/km in the decay of 1550nm.

29. optical fiber as claimed in claim 25 is characterized in that, is less than or equal to 0.167dB/km in the decay of 1550nm.

30. optical fiber as claimed in claim 25 is characterized in that, this optical fiber is multimode optical fibers, and core comprises at least 70 weight %SiO ₂

31. optical fiber as claimed in claim 25 is characterized in that, this core comprises at least 80 weight %SiO ₂

32. optical fiber as claimed in claim 25 is characterized in that, this core comprises at least 90 weight %SiO ₂

33. optical fiber as claimed in claim 25 is characterized in that, this core also comprises the chlorine of peak concentration less than 3000ppm.

34. optical fiber as claimed in claim 25 is characterized in that, the peak concentration of alkalimetal oxide is less than 700ppm.

35. optical fiber as claimed in claim 25 is characterized in that, the mean concns of alkalimetal oxide is less than 350ppm.

36. optical fiber as claimed in claim 25 is characterized in that, the peak concentration of alkalimetal oxide is less than 500ppm.

37. optical fiber as claimed in claim 25 is characterized in that, the peak concentration of alkalimetal oxide is 20-500ppm.

38. optical fiber as claimed in claim 25 is characterized in that, alkalimetal oxide is K ₂O.

39. optical fiber as claimed in claim 25 is characterized in that, first doping agent is a germanium oxide, and the peak concentration of alkalimetal oxide is 30-300ppm.

40. optical fiber as claimed in claim 25 is characterized in that, first doping agent is a germanium oxide, and the peak concentration of alkalimetal oxide is 30-150ppm.

41. optical fiber as claimed in claim 39 is characterized in that, alkalimetal oxide is K ₂O.

42. optical fiber as claimed in claim 39 is characterized in that, this core also comprises the chlorine of peak concentration less than 3000ppm.

43. optical fiber as claimed in claim 39 is characterized in that, the maximum fluorine concentration of this core is less than 0.2 weight %.

44. optical fiber as claimed in claim 39 is characterized in that, covering comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration is less than 200ppm.

45. optical fiber as claimed in claim 25 is characterized in that, first doping agent is a fluorine, and the peak concentration of alkalimetal oxide is 200-500ppm.

46. optical fiber as claimed in claim 25 is characterized in that, first doping agent is a fluorine, and the mean concns of alkalimetal oxide is 100-300ppm.

47. optical fiber as claimed in claim 45 is characterized in that, the fluorine concentration of this core is greater than 0.02 weight %.

48. optical fiber as claimed in claim 45 is characterized in that, the fluorine concentration of this core is greater than 0.15 weight %.

49. optical fiber as claimed in claim 45 is characterized in that, the maximum fluorine concentration of this core is 0.5-1.5 weight %.

50. optical fiber as claimed in claim 45 is characterized in that, this core oxygen-free germanium.

51. optical fiber as claimed in claim 45 is characterized in that, the minimum fluorine concentration of covering is at least 1.0 weight %.

52. optical fiber as claimed in claim 45 is characterized in that, described alkalimetal oxide is K ₂O.

53. optical fiber as claimed in claim 45 is characterized in that, this core also comprises the chlorine of peak concentration less than 500ppm.

54. optical fiber as claimed in claim 45 is characterized in that, described covering comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture, its peak concentration is less than 200ppm.

55. a fibre-optical preform, this prefabricated component comprises:

The main centre portions of forming by solid glass;

Surround the outer layer segment of this centre portions, this outer layer segment comprises the glass soot; And

It is characterized in that this centre portions comprises and is selected from K ₂O, Na ₂O, Li ₂O, Cs ₂O, Rb ₂O, and the alkalimetal oxide of their combination.

56. fibre-optical preform as claimed in claim 55 is characterized in that centre portions comprises K ₂O.

57. fibre-optical preform as claimed in claim 55 is characterized in that centre portions comprises Rb ₂O.

58. fibre-optical preform as claimed in claim 55 is characterized in that centre portions comprises GeO ₂

59. fibre-optical preform as claimed in claim 55 is characterized in that, outer layer segment comprises GeO ₂

60. a method of making optical fiber, this method comprises:

Formation comprises and is selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂First glass stick of the alkalimetal oxide of O and their mixture;

First glass stick is inserted in the centerline hole of fibre-optical preform, to form compound prefabricated component.

61. method as claimed in claim 60 is characterized in that, described glass stick comprises GeO ₂

62. method as claimed in claim 60 is characterized in that, the fibre-optical preform in the inserting step comprises the glass soot.

63. method as claimed in claim 60 is characterized in that, described fibre-optical preform comprises GeO ₂

64. method as claimed in claim 60, this method comprise that also fixed compound prefabricated component is to form the step of core prefabricated component.

65. as the described method of claim 64, this method also comprises the core prefabricated component is stretched to form the step of second glass stick.

66. as the described method of claim 65, this method also is included in the step that forms additional glass on second glass stick.

67., it is characterized in that the step that forms additional glass comprises deposition glass soot as the described method of claim 66.

68. a method of making optical fiber, this method may further comprise the steps:

Provide the glasswork of outside dimension (d1), with these goods with being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂O, and the alkalimetal oxide of their mixture mixes; With

Additional glass is made an addition to this glasswork, the final fixed wire drawing prefabricated component that has final outside dimension (d2) with formation, wherein outside dimension (d1) is less than or equal to 0.06 times of final size (d2), thereby alkalimetal oxide is concentrated near the center of finally fixed wire drawing prefabricated component.

69., it is characterized in that outside dimension (d1) is less than or equal to 0.03 times of final outside dimension (d2) as the described method of claim 68.

70. as the described method of claim 68, it is characterized in that, provide the step of glasswork further comprising the steps of:

To contain the silicon-dioxide soot and be deposited on the live spindle, with formation soot pipe,

By this soot pipe being exposed to the dry soot pipe of atmosphere containing chlorine;

With fluorine-containing atmosphere the soot pipe is carried out fluorine and purge, to remove dechlorination;

Fixed this silicon-dioxide soot pipe is to form vitrified silicon dioxide tube that contains.

71., it is characterized in that the described step of glasswork that provides is further comprising the steps of as the described method of claim 68:

Oxygen is passed through on the Potassium Bromide of heating with the formation dopant gas, and

This dopant gas is exposed to vitrified silicon dioxide tube.

72., it is characterized in that the described step of glasswork that provides is further comprising the steps of as the described method of claim 68:

Burning shrinkage is doped with the consolidated tubes of alkalimetal oxide to form glass stick.

73., it is characterized in that the described step of glasswork that provides is further comprising the steps of as the described method of claim 68:

Glasswork is carried out etching, to remove OH.

74., it is characterized in that the described step of glasswork that provides is further comprising the steps of as the described method of claim 68:

Alkalimetal oxide is diffused into this glasswork, wherein, concentration of dopant radial variations in this glasswork, in interior half part peak concentration is arranged, half part has minimum concentration outside, according to weight %, the peak concentration of half part is less than at 50% of the peak concentration of interior half part outside.

75., it is characterized in that the step of described interpolation additional glass also comprises inserts the step that contains silicon dioxide tube with this glasswork as the described method of claim 68.

76. as the described method of claim 68, it is characterized in that, described glasswork comprises silicon-dioxide and the additional glass that is doped with alkalimetal oxide, and described additional glass comprises the outside radius part of the silicon-dioxide of the inside radius part of unadulterated silicon-dioxide basically and doped with fluorine.

77. as the described method of claim 68, it is characterized in that, glasswork comprises the silicon-dioxide and the additional glass of doping germanium oxide and alkalimetal oxide, and described additional glass comprises the inside radius part of silicon-dioxide of doping germanium oxide and the outside radius part of unadulterated substantially silicon-dioxide.

78. a method of making optical fiber, this method may further comprise the steps:

To contain the silicon-dioxide soot and be deposited on the live spindle, contain silicon-dioxide soot pipe with formation,

At first contain silicon-dioxide soot pipe with dry this of chlorine-containing gas,

Contain silicon-dioxide soot pipe with further dry this of fluoro-gas then,

Fixed this contains silicon-dioxide soot pipe, with the formation Glass tubing,

With being selected from K ₂O, Na ₂O, Rb ₂O, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms;

This Glass tubing of burning shrinkage or intermediate, with the rod that forms alkali doped and

Contain the rod that silica glass makes an addition to alkali doped and add additional.

79., it is characterized in that described interpolation is additional, and to contain the step of silica glass further comprising the steps of as the described method of claim 78:

With the rod of alkali doped insert contain in the silicon-dioxide soot pipe with form rod in soot subassembly and

Fixed should the subassembly of rod in soot, to form fixed subassembly.

80. as the described method of claim 79, this method is further comprising the steps of:

On fixed subassembly, add the glass of doped with fluorine.

81., it is characterized in that described doping step is further comprising the steps of as the described method of claim 78:

Peak concentration diffusion alkalimetal oxide with about 20-1000ppm.

82., it is characterized in that described doping or burning shrinkage step also comprise with dry heat source heating glass pipe or intermediate as the described method of claim 78.

83. a method of making optical fiber, this method may further comprise the steps:

To contain the silicon-dioxide soot and be deposited on the live spindle, contain silicon-dioxide soot pipe with formation,

Contain silicon-dioxide soot pipe with dry this of chlorine-containing gas,

Contain silicon-dioxide soot pipe with further dry this of fluoro-gas again,

Fixed this silicon-dioxide soot pipe, with the formation Glass tubing,

With being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms;

This Glass tubing of burning shrinkage or intermediate, with the rod of formation alkali doped,

The rod insertion of alkali doped is contained in the silicon-dioxide soot pipe,

By the rod of this alkali doped with contain silicon-dioxide soot pipe and form plug,

With the silicon-dioxide of doped with fluorine make an addition to this plug and

The silicon-dioxide of fixed doped with fluorine is to form final wire drawing prefabricated component.

84. a method of making optical fiber, this method may further comprise the steps:

The silicon-dioxide soot of doped germanium is deposited on the live spindle, contains the silicon-dioxide soot pipe of doped germanium with formation,

With the silicon-dioxide soot pipe of dry this doped germanium of chlorine-containing gas,

Contain silicon-dioxide soot pipe with further dry this of fluoro-gas again,

The silicon-dioxide soot pipe of fixed this doped germanium, with the formation Glass tubing,

With being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms,

Form the rod of alkali doped by this Glass tubing or intermediate,

The rod of alkali doped inserted contain in the silicon-dioxide soot pipe, this contain silicon-dioxide soot pipe comprise doped germanium the silicon-dioxide soot annular inner portion and do not carry out the outer ring portion of doped silica soot substantially.

85. a method of making optical fiber, this method may further comprise the steps:

To contain the silicon-dioxide soot and be deposited on the live spindle, contain silicon-dioxide soot pipe with formation,

Contain silicon-dioxide soot pipe with dry this of chlorine-containing gas,

Contain silicon-dioxide soot pipe with further dry this of fluoro-gas again,

Fixed this silicon-dioxide soot pipe, with the formation Glass tubing,

With being selected from K ₂O, Na ₂O, LiO ₂, Rb ₂O, Cs ₂The alkalimetal oxide of O and their mixture mixes to this Glass tubing or by the intermediate that this Glass tubing forms, and to form the goods of alkali doped, wherein alkalimetal oxide mixes with the amount of about 20-1000ppm alkalimetal oxide.

86. as the described method of claim 85, this method is further comprising the steps of:

The goods of burning shrinkage alkali doped, with the rod of formation alkali doped,

The additional silicon-dioxide soot that contains of deposition on the rod of this alkali doped,

With the dry additional silicon-dioxide soot that contains of chlorine-containing gas,

The fixed additional silicon-dioxide soot that contains, with form fixed core prefabricated component and

With fixed core prefabricated component again wire drawing to form second plug.

87. as the described method of claim 86, this method also comprises with fluoro-gas carries out further exsiccant step to the additional silicon-dioxide soot that contains.

88. as the described method of claim 86, this method also comprises uses D ₂The step that fixed core prefabricated component or second plug are handled.

89. as the described method of claim 86, this method is further comprising the steps of:

The silicon-dioxide soot that contains of first covering is deposited on second plug,

With dry first covering of chlorine-containing gas contain the silicon-dioxide soot,

Carry out fluorine and mix with the silicon-dioxide soot that contains of fluoro-gas first covering,

Fixed this first covering contain the silicon-dioxide soot, with form the third leg and

With the third leg again wire drawing become the fourth leg.

90. as the described method of claim 89, this method is further comprising the steps of:

The silicon-dioxide soot that contains of second covering is deposited in the fourth leg,

With dry second covering of chlorine-containing gas contain the silicon-dioxide soot,

With fluoro-gas to second covering contain that the silicon-dioxide soot carries out that fluorine mixes and

Fixed this second covering contain the silicon-dioxide soot, to form final wire drawing prefabricated component.

91., it is characterized in that the weight % of fluorine is less than the fluorine weight % that contains the silicon-dioxide soot of first covering in the silicon-dioxide soot of second covering as the described method of claim 90.

92., it is characterized in that described doping step is further comprising the steps of as the described method of claim 85:

Heating is by KBr, KI or KNO ₃The alkali-metal source material of forming and

Carrier gas is passed through on source material, and entered in Glass tubing or the intermediate, so that alkalimetal oxide is diffused in Glass tubing or the intermediate.

93. the device of a diffusing, doping, it comprises:

Frame,

Be mounted to the Glass tubing of this frame rotation relatively,

Be connected to Glass tubing dopant source and

Dry heat source near the Glass tubing installation.

94., it is characterized in that described dopant source comprises a storer that links to each other with Glass tubing as the described diffusing, doping device of claim 93, described holder holds the alkali-metal-doped agent through the heating source heating.

95., it is characterized in that described dry heat source is an induction heater as the described diffusing, doping device of claim 93.

96. as the described diffusing, doping device of claim 95, it is characterized in that, described induction heater comprises inductor block that surrounds Glass tubing and the coil of installing near this inductor block, so that coil causes eddy current in inductor block when obtaining energy, thereby make the inductor block heating, and therefore heat described pipe.

97. as the described diffusing, doping device of claim 93, it is characterized in that, described induction heater comprises the tubular type inductor block that surrounds Glass tubing, surround the glass sock of this inductor block, be installed near the glass sock and the coil of close this inductor block, so that coil causes eddy current in inductor block when obtaining energy, thereby make the inductor block heating, and therefore heat described pipe.

98. as the described diffusing, doping device of claim 97, this device also comprise with inductor block and Glass tubing between the first inert gas flows passage that links to each other at interval, and second interval that between inductor block and glass sock, is used for around inductor block, providing rare gas element.

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