CN1186656C - Negative dispersion monomode optical fibre - Google Patents

Abstract

The present invention relates to a negative dispersion single-mode optical fiber which has the dispersion characteristic that the total dispersion is negative in a C-band optical communication window or both the C-band optical communication window and an L-band optical communication window and has a positive dispersion gradient. The optical fiber can be used for transmitting signals in DWDM optical communication systems at high speed at the C band and the L band. The fiber core of the optical fiber has three layers and four envelope layers which are provided by the PCVD technology and have different refractivity distribution, and two envelope layers provided by the OVD technology. The optical fiber satisfies the requirement of reducing the PMD value of optical fibers, and improves the bending resistance characteristic and the hydrogen loss resistance characteristic of the optical fibers. The optical fiber can generate a light pulse width compression effect and can consequently prolong dispersion restriction distance when used in 2.5Gbps with a direct intensity modulation laser with positive chirp. The optical fiber is very favorable to DWDM systems for middle and long distance transmission, and is capable of decreasing dispersion compensation expenses, avoiding using expensive external modulators and consequently reducing the cost of optical transmission devices.

Description

Monomode fiber with negative dispersion and manufacture method thereof

Technical field

The present invention relates to a kind of single-mode fiber that is used for the signal transmission at optical communication field.Thereby this optical fiber distributes can have at C-band (1525nm-1565nm) optical communication window or have total dispersion at C-band and L-band (1565nm-1625nm) optical communication window simultaneously and is negative dispersion characteristics and positive chromatic dispersion gradient by adjusting waveguide index, have low fiber PMD, and have the flexural property and the anti-hydrogen loss characteristic of improvement.

Background technology

Along with the fast development of the communication technology, Transmission Fibers capacity and transfer rate are had higher requirement.

Traditional G.652 single-mode fiber has 1310nm and two transmission windows of 1550nm, and its zero dispersion point is positioned near the 1310nm.For a long time, G.652 optical fiber only obtains widespread use on the 1310nm wave band.And at the 1550nm window, its bigger dispersion values (about 18ps/nm.km) has limited the raising of transfer rate, generally is used for the following transmission system of 2.5Gbps.Dwdm system is operated in C-band 1550nm window mostly at present, that is the operation window of EDFA.Along with the practicability of EDFA, the C-band window progressively becomes the groundwork window of dwdm optical communication system.Be adaptation C-band DWDM The Application of Technology, non-zero dispersion displacement optical fiber, promptly G.655 optical fiber arises at the historic moment.G.655 optical fiber designs is for having non-vanishing and lower dispersion values on 1550nm window banging wavelength, such as 2 to 4ps/nm.km, make it both can overcome nonlinear effect, can support two-forty again, long Distance Transmission as the dwdm system of 10Gbps and 40Gbps, and need not dispersion compensation or the dispersion compensation cost reduces, thereby finally reduce the complicacy and the network cost of network.It is fit to the needs that dwdm system develops to more intensive channel spacing direction in the inhibition of 1550nm operation window to nonlinear effects such as FWM and XPM, and satisfies the development need of TDM and two kinds of technology of DWDM simultaneously.For the 10Gbps system, G.655 the CHROMATIC DISPERSION IN FIBER OPTICS restricted distance is about 200km, far beyond G.652 optical fiber property is superior.

Can obtain respectively at the dispersion values of C-band and L-band to just or be negative dispersion characteristics by zero dispersion point design optical fiber G.655.Single order and 2nd order chromatic dispersion that two kinds of optical fiber all can support the long distance D WDM transmission system of 2.5Gbps and 10Gbps speed to have the G.655 optical fiber of positive dispersion all can compensate.Its major defect is possible produce modulational instability.Major advantage with G.655 optical fiber of negative dispersion is not have the modulational instability problem, and can utilize the cheap G.652 optical fiber of cost to compensate its 1st order chromatic dispersion.In the application scenario of transmission range greater than 1000km, as the submarine optical fiber cable system, because the pulse frequency spectrum broadening of positive dispersion fiber will be is greatly fallen outside the WDM filter transmission band to part power wherein, perhaps can narrow down and filtered owing to image intensifer link gain band, be used alternatingly positive negative dispersion optical fiber this moment in link will be good selection.In addition, the G.655 optical fiber with negative dispersion with have the direct intensity modulated laser instrument of just warbling when using, can produce light pulsewidth pinch effect, thereby prolong dispersion limit.But existing PMD value, flexural property and anti-hydrogen loss characteristic with G.655 optical fiber of negative dispersion still treated further improvement.

Disclosed a kind of optical fiber in patent CN1274856A, it has at EDFA workspace (1530nm-1565nm)-negative dispersion that 3.0 ± 1.7ps/nm.km is little, and on average less than 0.05ps/nm ².km positive dispersion slope, this optical fiber is used to have the wdm system of dispersion compensation, and this CHROMATIC DISPERSION IN FIBER OPTICS characteristic does not comprise the use expansion of L-band.This optical fiber has solved the crooked sensitive issue of general negative dispersion optical fiber, but the fiber PMD link value needs more strict requirement in close relations with the high speed dwdm system.

Generally speaking the characteristic of optical fiber except the attenuation characteristic, almost all can be determined by the geometry and the optics cross-section structure of optical fiber.Wherein as: dispersion characteristics, cutoff wavelength, mode field diameter or useful area, macrobending characteristic or the like.The environmental characteristics of optical fiber is decided by the production technology of optical fiber and the cabling process of optical fiber greatly.

Studies show that, should satisfy following condition with optical fiber for long distance or middle and long distance high-speed high capacity dwdm system:

-can adapt to the DWDM technology application of C-band EDFA window.

-can adapt to the application extension of DWDM technology on L-band.

-tool suitable dispersion characteristic adaptation two-forty optical transmission system on service band.

The useful area that-tool is fit to is to suppress nonlinear effect.

-have a low attenuation, good flexural property.

-strong anti-hydrogen loss characteristic.

-low PMD.

Below be the definition and the explanation of some terms among the present invention:

The useful area A of optical fiber _EffBe meant the average area of transmitting optical power in the optical fiber, A _EffDetermine by following formula:

$A_{\mathrm{eff}}=\frac{2\mathrm{\π}\[{\∫}_0^{\∞}{E}^2\left(R\right)\mathrm{RdR}{\]}^2}{{\∫}_0^{\∞}{E}^4\left(R\right)\mathrm{RdR}}$

Wherein R is an optical fiber normalization radius, and R=r/a, r are coordinates radially, and a is a fiber core radius, and E (R) is the field distribution function of basic mode, and this formula is applicable to arbitrary refractive index section optical fiber effective area A _EffCalculating.

The mode field diameter MFD of single-mode fiber roughly can be expressed as: the maximal value that the radial field distribution is located by fiber axis (r=0) in the optical fiber is reduced to 1/e to two ends and (is about 37%, pairing diameter in the time of e=2.71828).If mode field diameter MFD is W, its Petermann II definition is:

${\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="C0213885900192.png"\; state="\{\{state\}\}">W</figure-callout>}}^2=\frac{2{\&Integral;}_0^{\&infin;}{E}^2\left(R\right)\mathrm{RdR}}{{\&Integral;}_0^{\&infin;}{\left(\frac{\mathrm{dE}\left(R\right)}{\mathrm{dR}}\right)}^2\mathrm{RdR}}$

Refractive index contrast Δ % is defined as follows: Δ %=[(n ₁ ²-n ₀ ²)/2n ₀ ²] * 100%

N wherein ₁Be fiber core refractive index, n ₀Be the optical fiber jacket refractive index, be pure silicon dioxide (SiO ₂) refractive index.Do not explain in addition as having among the present invention, Δ % is by the maximum n of core region ₁The maximum relative refractive index that is characterized is poor.

Polarization mode dispersion PMD.

The flexural property of optical fiber is described as by a certain Standard test programme test down, and the attenuation of optical fiber on specified wavelength increases.Press the G.655.B optical fiber macrobend characteristic test standard shown in the optical fiber technology standard of ITU, under the tested optical fiber crooked situation in 100 weeks on the axle of 75mm diameter, it causes maximum permission to decay to 0.5dB in the bending of 1550nm place, cause maximum permission to decay to 0.5dB in the bending of 16xxnm place, xxnm≤25nm is wherein arranged.

Optical fiber hydrogen loss characteristic evaluation method of testing is: optical fiber is placed hydrogen (H ₂) and the mixed gas of helium (He) in, hydrogen (H wherein ₂) volumetric molar concentration be 1%, the volumetric molar concentration of helium (He) is 99%, and in insulation under the constant 70 ℃ environment temperature after 16 hours, takes out optical fiber and surveys near its hydrogen 1530nm and cause attenuation and increase, and should be not more than 0.01dB/km.

DWDM is the english abbreviation of dense wave division multipurpose.

Summary of the invention

Technical matters to be solved by this invention provides a kind of monomode fiber with negative dispersion, and this optical fiber has the dispersion characteristics of total dispersion for bearing at C-band or at C-band and L-band.This optical fiber can satisfy the transmission requirement of long distance or middle and long distance dwdm optical communication system, can support two-forty (for example 2.5Gbps or 10Gbps) the DWDM technology of the following channel spacing of 100GHZ.This optical fiber has satisfied the needs that reduce the type fiber PMD, has also satisfied the flexural property that improves the type optical fiber and the needs of anti-hydrogen loss characteristic.

The present invention solves the problems of the technologies described above the technical scheme that is proposed to be: have a core layer and a covering, it is characterized in that fibre core is provided with three different fibre core layerings of index distribution, covering includes six layerings, the diameter R of the described optical fiber first fibre core layering Core1 _Core1Be about 1.0 μ m to 5.0 μ m, its refractive index contrast Δ % _Core1The diameter R that is about 0.6% to 1.2%, the second fibre core layering Core2 _Core2Be about 3.0 μ m to 6.0 μ m, its refractive index contrast Δ % _Core2The diameter R that is about 0.25% to 0.65%, the three fibre core layering Core3 _Core3Be about 4.0 μ m to 8.0 μ m, its refractive index contrast Δ % _Core3The diameter R that is about 0.05% to 0.25%, the first covering layering Clad.1 _Clad.1Be about 8.0 μ m to 12.0 μ m, its refractive index contrast Δ % _Clad.1The diameter R that is about-0.15% to 0.15%, the second covering layering Clad.2 _Clad.2Be about 12.0 μ m to 20.0 μ m, its refractive index contrast Δ % _Clad.2The diameter R that is about 0.1% to 0.4%, the triple clad layering Clad.3 _Clad.3Be about 18.0 μ m to 30.0 μ m, its refractive index contrast Δ % _Clad.3Be about-0.1% to 0.1%, the four, five, six covering layering Clad.4, Clad.5, Clad.6, its diameter R _Clad.4, R _Clad.5, R _Clad.6Be respectively 20.0 μ m to 40.0 μ m, 30.0 μ m to 50.0 μ m, 123.0 μ m to 126.0 μ m, its refractive index is the pure silicon dioxide refractive index, be constant refractive index, described optical fiber is under the crooked situation in 100 weeks on the 75mm diameter axle, because the crooked loss that causes is not more than 0.02dB at 1550nm, be not more than 0.02dB at 1625nm, cable optical fiber PMD coefficient is not less than 0.036ps/km ^1/2Clad.3 in the covering layering applies the germanium of 2.0% to 5.0% volumetric molar concentration, described optical fiber has at 1525nm to 1565nm wave band-and 1.0ps/nm.km is to the negative dispersion of-10.0ps/nm.km, perhaps, described optical fiber have at 1525nm to 1625nm wave band-1.0ps/nm.km is to the negative dispersion of-10.0ps/nm.km.

Above-mentioned optical fiber has comprised L-band in 1525nm to 1625nm wavelength band, i.e. 1565nm to 1625nm wave band, this wave band are that wave band is used in the expansion of dwdm system.

Described optical fiber has the mode field diameter MFD that is not less than 7.6 μ m at 1550nm; Have at 1550nm and be not less than 45 μ m ²Useful area A _EffDescribed optical fiber has at 1550nm and is not more than 0.1ps/nm ².km chromatic dispersion gradient; Has the not cable optical fiber cutoff wavelength λ that is not more than 1700nm _c

The parameter distribution of one group of preferable fibre core and covering is in this optical fiber:

Δ % _Core1Be about 0.69% to 0.85% R _Core1Be about 3.45 to 4.22 μ m

Δ % _Core2Be about 0.47% to 0.57% R _Core2Be about 4.62 to 5.65 μ m

Δ % _Core3Be about 0.17% to 0.22% R _Core3Be about 5.46 to 6.67 μ m

Δ % _Clad.1Be about-0.06% to 0.06% R _Clad.1Be about 8.52 to 10.42 μ m

Δ % _Clad.2Be about 0.14% to 0.17% R _Clad.2Be about 15.27 to 18.66 μ m

Δ % _Clad.3Be about 0.03% to 0.04% R _Clad.3Be about 19.83 to 24.24 μ m

Δ % _Clad.4Be about 0% R _Clad.4Be about 21.72 to 26.55 μ m

Δ % _Clad.5Be about 0% R _Clad.5Be about 30.0 to 36.41 μ m

Δ % _Clad.6Be about 0% R _Clad.6Be about 123 to 125 μ m.

The index distribution of above-mentioned each layering is the function of this layering each point apart from optical fiber axis radial distance, and the index distribution of getting each layering is the step function of step function or angle slyness.

The technical scheme of single-mode fiber method for making of the present invention is:

Described single-mode fiber is to be drawn with preform by Gong the wire drawing that PCVD technology and OVD technology provide jointly to form, and each layering of this preform and each layering of single-mode fiber are one to one, each stratified sedimentation technology of described preform is: sandwich layer layering Core1, Core2, Core3, covering layering Clad.1, Clad.2, Clad.3, the sedimentary deposit that Clad.4 provides for PCVD technology; Covering layering Clad.5, the sedimentary deposit that Clad.6 provides for OVD technology, and provide the pure silicon dioxide bushing pipe to be covering layering Clad.5 by OVD technology.

In the present invention, the sandwich layer layering Core1 of this preform, Core2, Core3 are pure silicon dioxide (SiO ₂) matrix doped germanium (Ge), or be pure silicon dioxide (SiO ₂) matrix mixes germanium (Ge) and fluorine (F) altogether to form required positive relative index of refraction difference cloth.Clad.1 in the covering layering of this preform, Clad.2, Clad.3 are pure silicon dioxide (SiO ₂) matrix doped germanium (Ge) or doped with fluorine (F), or be pure silicon dioxide (SiO ₂) matrix mixes germanium (Ge) altogether and fluorine (F) distributes with the refractive index contrast that forms required plus or minus.Clad.4 in the covering layering of this preform, Clad.5, Clad.6 are pure silicon dioxide (SiO ₂).

In covering layering Clad.3, apply the anti-hydrogen loss performance of germanium (Ge) doping can raising optical fiber.Experiment shows, the germanium (Ge) that the Clad.3 in the covering layering applies 2.0% to 5.0% volumetric molar concentration can effectively improve the anti-hydrogen loss performance of optical fiber.In the present invention, can in Clad.3, apply the optical waveguide structure of fluorine (F) doping simultaneously to realize presetting.

In the method for manufacturing single-mode fiber of the present invention, optical fiber prefabricated rod mandrel partly comprises sandwich layer layering Core1, Core2, the Clad.1 in Core3 and the covering layering, Clad.2, C1ad.3, Clad.4, C1ad.5, this plug are that molten the contracting of electricity consumption collapsar technics formed after PCVD technology was finished the interior deposition of pipe, be the optical fiber prefabricating plug, the pure silicon dioxide (SiO of plug is provided by OVD technology at last again ₂) surrounding layer is Clad.6, thereby the preform that formation can supply wire drawing to use, this preform draws via drawing process and is this kind optical fiber of nominal outside diameter 125 μ m.Adopt electric smelting contract technology will to optical fiber prefabricated rod mandrel axially and geometry homogeneity radially be greatly improved, can improve the circularity of optical fiber prefabricated rod mandrel, reduction fiber PMD index is had great role.

Single-mode fiber of the present invention has the dispersion characteristics of total dispersion for bearing at C-band or at C and L-band.For single-mode fiber, owing to do not exist intermode dispersion, the total dispersion of optical fiber to be meant the material dispersion and the waveguide dispersion sum of optical fiber.The light field of single-mode fiber mainly is distributed in the fiber core district, other has the part optical field distribution in covering, the light wave of different wave length is different in the energy distribution of fiber core and covering, and the group velocity of the light wave of different wave length in optical fiber is also different, constitutes waveguide dispersion.The unique optical waveguide structure that depends on of the waveguide dispersion of single-mode fiber, promptly refractive index profile distributes.The material dispersion of optical fiber remains unchanged when the matrix material of making optical fiber and dopant material are determined substantially.For obtaining total negative dispersion characteristic of expectation, must reduce the waveguide dispersion of optical fiber.If will obtain negative dispersion characteristics on pre-wave band, then optical waveguide structure should satisfy and makes long wavelength light faster than short-wavelength light velocity of propagation, otherwise then shows as positive dispersion characteristics.

The present invention can be by adjusting the refractive index contrast Δ % of fibre core layering Core1 _Core1Refractive index contrast Δ % with covering layering Clad.1 _Clad.1And the diameter R of fibre core layering Core3 _Core3Diameter R with covering layering Clad.1 _Clad.1Obtain required negative wave and lead chromatic dispersion; By changing the diameter R of covering layering Clad.1 _Clad.1Diameter R with covering layering Clad.2 _Clad.2And the refractive index contrast Δ % of covering layering Clad.2 _Clad.2Obtain suitable optical fiber effective area and chromatic dispersion gradient.The refractive index contrast Δ % of covering layering Clad.3 _Clad.3With diameter R _Clad.3The scalable cutoff wavelength.

Theoretical analysis shows to have bigger negative dispersion for making waveguide dispersion, the refractive index contrast Δ % of covering Clad.1 _Clad.1Should be low as far as possible, the refractive index contrast Δ % of sandwich layer Core1 _Core1The height of should trying one's best, and under the prerequisite of not destroying the overall optical waveguiding structure, reduce the refractive index contrast Δ % of covering Clad.2 as far as possible _Clad.2

As described in background of invention, the various optical characteristics of optical fiber have very complicated inner link each other, are being mutual contradiction sometimes.For example the negative dispersion characteristic of optical fiber is relevant with the attenuation or the flexural property of optical fiber.For the waveguide dispersion that obtains to bear, sandwich layer Core1 must adopt a higher refractive index contrast Δ % _Core1, optical fiber of the present invention has and is not less than 0.6% sandwich layer refractive index contrast.The Rayleigh loss that higher sandwich layer refractive index contrast Δ % will strengthen optical fiber, fibre core hierarchical design can improve light field because of the too high situation about too concentrating of Δ %, reduce the Rayleigh loss.Core region is made as at least three layering Core1 among the present invention, Core2, and Core3, this three layerings refractive index contrast Δ % successively decreases according to this.Select less optical fiber core diameter R _Core3Purpose be to lead chromatic dispersion in order to obtain bigger negative wave.Under the negative dispersion characteristic requires, avoid the measure of too high core refractive index % also to comprise and introduce sink covering Clad.1, i.e. Δ % _Clad.1Value is less than zero.Sagging covering can worsen the flexural property of optical fiber, thereby total attenuation of optical fiber is increased, so Δ % _Clad.1Value should not be selected negative, Δ % among the present invention _Clad.1Value is not less than-0.15%.The refractive index contrast Δ % of surrounding layer Clad.2 _Clad.2Selected low optical fiber MFD is too reduced, this flexural property to optical fiber is beneficial, but is unfavorable for the application requirements of DWDM.The refractive index contrast Δ % of Clad.2 among the present invention _Clad.2Selection is not less than 0.1%.

Optical fiber of the present invention use the chromatic dispersion gradient of wave band be chosen as on the occasion of, with respect to the optical waveguide of negative dispersion slope, do not need too dark sagging blanket design, this is favourable to improving bending loss.But because negative dispersion optical fiber of the present invention requires to have very big zero-dispersion wavelength, note that control fibre-optic mode field diameter MFD does not want excessive and too small under the prerequisite that satisfies the zero-dispersion wavelength requirement, excessive MFD can worsen the flexural property of optical fiber, and too small MFD can bring the increase of spillage of material.

As previously mentioned, the purpose of optical fiber inner core hierarchical design is to optimize optical field distribution, reduces spillage of material, and suitably increases optical fiber MFD.For guaranteeing the fibre-optical bending characteristic simultaneously, not destroying under the waveguide optical characteristic prerequisite, require waveguide design accurate, and manufacturing process have strict manufacturing tolerance.Select higher sandwich layer refractive index contrast Δ % _Core1, the sandwich layer diameter R of selection broad _Core1, can between concentrated and dispersion, obtain a moderate balance to optical field distribution.Sandwich layer refractive index contrast Δ % _Core2Height then be for the influence of the balanced second covering layering Clad.2 to light field, destroy flexural property in order to avoid light field is too attracted by surrounding layer.Sandwich layer width R _Core2Requirement has very little design and manufacturing tolerance so that do not influence the fibre-optical dispersion characteristic, and contribution is very large because this sandwich layer Core2 is to fibre-optical dispersion.Sandwich layer Core3 has been alleviated the refractive index sudden change from the sandwich layer to the covering, can reduce the internal stress that inside of optical fibre forms because of high index-contrast, and experiment shows that the index distribution of gradual change is helpful to the flexural property of optimizing optical fiber.In like manner, select higher covering refractive index contrast Δ % _Clad.2With the influence of the sagging covering of equilibrium to light field, control cladding diameter R _Clad.1Not excessive to control MFD in the reasonable scope, the fibre-optical bending characteristic that can obtain.The process advantage of PCVD is to realize requiring the extremely waveguide section of strictness of design tolerance, and this not only can guarantee the intact characteristic of optical fiber, also can guarantee high finished product efficient.

Standard method of test according to the fibre-optical bending performance that provides in the definition, under the crooked situation in 100 weeks on the 75mm diameter axle, this invents described monomode fiber with negative dispersion because the crooked loss that causes is not more than 0.02dB at 1550nm, be not more than 0.02dB at 1625nm, the requirement that is lower than 0.5dB that the standard of being much better than provides.Optical fiber of the present invention has good bending property.

Large effective area and low-dispersion slope as optical fiber also is not easy to realize simultaneously in addition.Low-dispersion slope is to reducing the system dispersion handling cost highly significant, and large effective area is to suppress fiber nonlinear effect, improves the valid approach of system signal noise ratio, and therefore the Transmission Fibers used of following dwdm system should require to possess simultaneously above two characteristics.The waveguide design method of pointing out according to the present invention, and utilization PCVD technology is in conjunction with OVD technology helps being in harmonious proportion the two contradiction of useful area and chromatic dispersion gradient.

Above-mentioned showing, for under the prerequisite of the basic dispersion characteristics of not destroying waveguide, taking into account other optical parametric, need the complicated waveguide section of design, and require production technology to control accurately, so that reproduce the waveguide section of pre-design in the optical fiber error freely.The waveguide section of this invention optical fiber tool complexity, its fibre core layering Core1, Core2, Core3 and covering layering Clad.1, Clad.2, the geometry of Clad.3 and refractive index parameter major decision the optical characteristics of this waveguide.Above-mentioned each layering provides by PCVD technology.The process characteristic of PCVD technology can guarantee accurately to realize default waveguide section.

The hydrogen loss characteristic of optical fiber is meant made surface-coated optical fiber in hydrogen atmosphere, and it is in the increase of 1530nm place attenuation.Because it has influence near the operation window of dwdm system 1550nm, so must reduce the hydrogen-sensitivity of optical fiber.Improve the cabling process of optical fiber, or adopt special optical fiber surface coating material all to help to improve the anti-hydrogen loss ability of optical fiber.Point out among the present invention, in the covering layering Clad.3 of described single-mode fiber, with pure silicon dioxide (SiO ₂) matrix doped germanium (Ge) material will improve the anti-hydrogen loss characteristic of optical fiber.

The defective of the hydrogen loss of optical fiber and optical fiber self is relevant, and its defective is many more, and hydrogen loss is serious more.Defective in the optical fiber, no matter be inside or surface imperfection, all make the hydrogen atom (H) in the atmosphere be easy to spread to inside of optical fibre, and with between the silicon atom in the optical fiber (Si) with the chemical bond combination, it can be expressed as Si-H, this kind combination can cause the luminous energy absorption peak at the 1530nm wavelength, thereby the loss that makes optical fiber appear at the 1530nm place increases, and promptly is referred to as the hydrogen loss of optical fiber.Therefore, the defective of minimizing optical fiber is to improve the effective way of the anti-hydrogen loss performance of optical fiber.Germanium (Ge) material that dopes certain volumetric molar concentration when PCVD process deposits covering layering Clad.3 will help to reduce the viscosity of preform, thereby allow drawing process to reduce drawing tensile force, verified little drawing tensile force helps to reduce the inside or the surface imperfection of optical fiber.PCVD technology is as a kind of gas-phase deposition, reacting gas oxygen (O in its deposition process ₂) keep redundant, some superfluous amount oxygen atom (O) will be fixed in the sediment, proved that the residue oxygen atom (O) in the sedimentary deposit can cause the inside of optical fibre defective, and germanium (Ge) can combine with the residue oxygen atom (O) in the sediment, thereby reduce the inherent vice of covering layering Clad.3, and, improved the anti-hydrogen loss performance of optical fiber to left each adjacent core bag layering formation hydrogen (H) restraining barrier of Clad.3.

Experiment shows, the germanium (Ge) that the Clad.3 in the covering layering applies 2.0% to 5.0% volumetric molar concentration can effectively improve the anti-hydrogen loss performance of optical fiber.Optical fiber of the present invention is implemented pure silicon dioxide (SiO in covering layering Clad.3 ₂) the matrix germanium (Ge) of 3.5% volumetric molar concentration that mixes, and mix optical waveguide structure to realize presetting of the fluorine (F) that in Clad.3, applies respective amount simultaneously.According to the optical fiber hydrogen loss characteristic evaluation method of testing described in the definition, test its hydrogen and cause loss less than 0.002dB/km at 1530nm, be much better than the standard that is not more than 0.01dB/km that method of testing is recommended.

PMD is considered to improve the final limiting factor of optical fiber telecommunications system transfer rate, and reducing PMD has crucial meaning.The reduction of PMD has a variety of methods, and wherein most important aspect is to produce the optical waveguide of circle as far as possible, and the circularity that improves preform can help to improve the circularity of optical fiber, and then finally reduces fiber PMD.The pointed optical fiber prefabricated rod mandrel electric smelting of the present invention technology that contracts can improve the circularity of preform, effectively reduces fiber PMD.

The electric smelting of adopting among the present invention is contracted technology because of adopting 360 degree ring-type hot-zones, changed prefabricated rod mandrel monolateral state that is heated in molten compression process, can obtain the fabulous optical fiber prefabricated rod mandrel of circularity, its sandwich layer out-of-roundness index can accomplish whole axially on less than 1.0%; The electric smelting compression process has been avoided the impact of oxyhydrogen flame collapsar technics high speed air-flow to prefabricated rods, the no axial bending of whole rod, and the bow degree can be lower than 0.1mm.The contract optical fiber prefabricated rod mandrel circularity of technology manufacturing and how much homogeneity of electric smelting can guarantee fine low PMD characteristic.The not cable optical fiber PMD coefficient of single-mode fiber of the present invention is less than 0.036ps/km ^1/2, best values 0.035ps/km ^1/2, representative value 0.035ps/km ^1/2

Description of drawings

Fig. 1 is the diagram of optical fibre refractivity section distribution of the present invention and each layering refractive index contrast Δ % and diameter R.

Fig. 2 is the dispersion characteristic curve diagram of optical fiber embodiment 1,2,3 of the present invention.

Fig. 3 is the waveguide cross-section illustration of optical fiber embodiment 1 of the present invention.

Fig. 4 is the waveguide cross-section illustration of optical fiber embodiment 2 of the present invention.

Fig. 5 is the waveguide cross-section illustration of optical fiber embodiment 3 of the present invention.

Embodiment

Below provide three embodiment and the optical characteristics thereof of monomode fiber with negative dispersion of the present invention, wherein embodiment 1, optical fiber shown in the embodiment 2 has total dispersion at C-band (1525nm-1565nm) optical communication window and is negative dispersion characteristics and positive chromatic dispersion gradient, and optical fiber shown in the embodiment 3 has total dispersion at C-band (1525nm-1565nm) and L-band (1565nm-1625nm) optical communication window and is the dispersion characteristics born and positive chromatic dispersion gradient.

-embodiment 1:

The optical fibre refractivity section that Figure 3 shows that negative dispersion optical fiber embodiment 1 of the present invention distributes.

1 oblique line of example shown in Fig. 2 is the dispersion characteristics of negative dispersion optical fiber embodiment 1 of the present invention.

This optical fiber is single-mode fiber, and it has three sandwich layer layering Core1, Core2, and Core3 and six covering layering Clad.1, Clad.2, Clad.3, Clad.4, Clad.5, Clad.6, wherein:

-the first fibre core layering Core1, its refractive index contrast Δ % _Core1Be about 0.760%, its diameter R _Core1Be about 3.4 μ m.

-the second fibre core layering Core2, its refractive index contrast Δ % _Core2Be about 0.520%, its diameter R _Core2Be about 4.6 μ m.

-Di three fibre core layering Core3, its refractive index contrast Δ % _Core3Be about 0.190%, its diameter R _Core3Be about 5.6 μ m.

-the first covering layering Clad.1, its refractive index contrast Δ % _Clad.1Be about 0.043%, its diameter R _Clad.1Be about 9.4 μ m.

-the second covering layering Clad.2, its refractive index contrast Δ % _Clad.2Be about 0.160%, its diameter R _Clad.2Be about 17.0 μ m.

-Di triple clad layering Clad.3, its refractive index contrast Δ % _Clad.3Be about 0.038%, its diameter R _Clad.3Be about 21.8 μ m.

-Di four covering layering Clad.4, its refractive index contrast Δ % _Clad.4Be about 0.0%, its diameter R _Clad.4Be about 23.2 μ m.

-Di five covering layering Clad.5, its refractive index contrast Δ % _Clad.5Be about 0.0%, its diameter R _Clad.5Be about 33.0 μ m.

-Di six covering layering Clad.6, its refractive index contrast Δ % _Clad.6Be about 0.0%, its diameter R _Clad.6Be about 125 μ m.

Three sandwich layer layering Core1 of this invention optical fiber, Core2, the Clad.1 in Core3 and the covering layering, Clad.2, Clad.3 are the pure silicon dioxide (SiO that PCVD technology provides ₂) sedimentary deposit of matrix doped germanium (Ge) and fluorine (F), the pure silicon dioxide (SiO that the Clad.4 in its covering layering provides for PCVD technology ₂) sedimentary deposit, the Clad.5 in its covering layering, the pure silicon dioxide (SiO that Clad.6 provides for OVD technology ₂) sedimentary deposit.

This inventive embodiments 1 optical fiber has following characteristic:

-dispersion characteristics

1550nm abbe number :-4.5ps/nm.km

1525nm to 1565nm abbe number scope :-1.0ps/nm.km is to-8.0ps/nm.km

1550nm chromatic dispersion gradient: 0.093ps/nm ².km

Zero-dispersion wavelength: 1595nm

-attenuation characteristic

1550nm attenuation coefficient: 0.202dB/km

-cable optical fiber cutoff wavelength λ not _c: 1450nm to 1560nm

-1550nm mode field diameter MFD:8.5 μ m

-1550nm useful area A _Eff: 57 μ m ²

-macrobending loss (75mm mandrel, 100 circles)

1550nm：≤0.008dB

-hydrogen loss characteristic (1%H ₂Add 99%He, 70 ℃ are incubated 16 hours)

1530nm：≤0.001dB/km

-cable optical fiber PMD coefficient :≤0.035ps/km not ^1/2

This inventive embodiments 1 described single-mode fiber has total dispersion at C-band (1525nm-1565nm) optical communication window and is negative dispersion characteristics and positive chromatic dispersion gradient.This wave band is the service band of EDFA.This optical fiber can satisfy the transmission requirement of long distance or middle and long distance dwdm optical communication system, can support the DWDM technology of the 2.5Gbps/10Gbps speed of the following channel spacing of 100GHz.This optical fiber has satisfied the needs that reduce the PMD value of the type optical fiber.In addition, this optical fiber has also satisfied the counter-bending characteristic of improving the type optical fiber and the needs of anti-hydrogen loss characteristic.

This negative dispersion optical fiber with have the direct intensity modulated laser instrument of just warbling when being used in 2.5Gbps, can produce light pulsewidth pinch effect, thereby prolong dispersion limit.Its dwdm system for the middle and long distance transmission is highly beneficial, can reduce the dispersion compensation expense, and can avoid using expensive external modulator, thereby can reduce the cost of optical transmission device.

-embodiment 2:

The optical fibre refractivity section that Figure 4 shows that negative dispersion optical fiber embodiment 2 of the present invention distributes.

2 oblique lines of example shown in Fig. 2 are the dispersion characteristics of negative dispersion optical fiber embodiment 2 of the present invention.

This optical fiber is single-mode fiber, and it has three sandwich layer layering Core1, Core2, and Core3 and six covering layering Clad.1, Clad.2, Clad.3, Clad.4, Clad.5, Clad.6, wherein:

-the first fibre core layering Core1, its refractive index contrast Δ % _Core1Be about 0.758%, its diameter R _Core1Be about 4.0 μ m.

-the second fibre core layering Core2, its refractive index contrast Δ % _Core2Be about 0.519%, its diameter R _Core2Be about 5.3 μ m.

-Di three fibre core layering Core3, its refractive index contrast Δ % _Core3Be about 0.190%, its diameter R _Core3Be about 6.2 μ m.

-the first covering layering Clad.1, its refractive index contrast Δ % _Clad.1Be about-0.031%, its diameter R _Clad.1Be about 8.5 μ m.

-the second covering layering Clad.2, its refractive index contrast Δ % _Clad.2Be about 0.153%, its diameter R _Clad.2Be about 15.8 μ m.

-Di triple clad layering Clad.3, its refractive index contrast Δ % _Clad.3Be about 0.036%, its diameter R _Clad.3Be about 22.3 μ m.

-Di four covering layering Clad.4, its refractive index contrast Δ % _Clad.4Be about 0.0%, its diameter R _Clad.4Be about 24.7 μ m.

-Di five covering layering Clad.5, its refractive index contrast Δ % _Clad.5Be about 0.0%, its diameter R _Clad.5Be about 33.2 μ m.

-Di six covering layering Clad.6, its refractive index contrast Δ % _Clad.6Be about 0.0%, its diameter R _Clad.6Be about 125 μ m.

Three sandwich layer layering Core1 of this invention optical fiber, Core2, the Clad.1 in Core3 and the covering layering, Clad.2, Clad.3 are the pure silicon dioxide (SiO that PCVD technology provides ₂) sedimentary deposit of matrix doped germanium (Ge) and fluorine (F), the pure silicon dioxide (SiO that the Clad.4 in its covering layering provides for PCVD technology ₂) sedimentary deposit, the Clad.5 in its covering layering, the pure silicon dioxide (SiO that Clad.6 provides for OVD technology ₂) sedimentary deposit.

These inventive embodiments 2 optical fiber have following characteristic:

-dispersion characteristics

1550nm abbe number :-3.4ps/nm.km

1525nm to 1565nm abbe number scope :-1.0ps/nm.km is to-6.0ps/nm.km

1550nm chromatic dispersion gradient: 0.073ps/nm ².km

Zero-dispersion wavelength: 1595nm

-attenuation characteristic

1550nm attenuation coefficient: 0.208dB/km

-cable optical fiber cutoff wavelength λ not _c: 1300nm to 1400nm

-1550nm mode field diameter MFD:8.2 μ m

-1550nm useful area A _Eff: 53 μ m ²

-macrobending loss (75mm mandrel, 100 circles)

1550nm：≤0.01dB

-hydrogen loss characteristic (1%H ₂Add 99%He, 70 ℃ are incubated 16 hours)

1530nm：≤0.001dB/km

-cable optical fiber PMD coefficient :≤0.035ps/km not ^1/2

These inventive embodiments 2 described single-mode fibers have total dispersion at C-band (1525nm-1565nm) optical communication window and are negative dispersion characteristics and positive chromatic dispersion gradient, and this wave band is the service band of EDFA.This optical fiber can satisfy the transmission requirement of long distance or middle and long distance dwdm optical communication system, can support the DWDM technology of the 2.5Gbps/10Gbps speed of the following channel spacing of 100GHz. and this optical fiber has satisfied the needs that reduce the PMD value of the type optical fiber.In addition, this optical fiber has also satisfied the counter-bending characteristic of improving the type optical fiber and the needs of anti-hydrogen loss characteristic.

This negative dispersion optical fiber with have the direct intensity modulated laser instrument of just warbling when being used in 2.5Gbps, can produce light pulsewidth pinch effect, thereby prolong dispersion limit.Its dwdm system for the middle and long distance transmission is highly beneficial, can reduce the dispersion compensation expense, and can avoid using expensive external modulator, thereby can reduce the cost of optical transmission device.

-embodiment 3:

The optical fibre refractivity section that Figure 5 shows that negative dispersion optical fiber embodiment 3 of the present invention distributes.

3 oblique lines of example shown in Fig. 2 are the dispersion characteristics of negative dispersion optical fiber embodiment 3 of the present invention.

This optical fiber is single-mode fiber, and it has three sandwich layer layering Core1, Core2, and Core3 and six covering layering Clad.1, Clad.2, Clad.3, Clad.4, Clad.5, Clad.6, wherein:

-the first fibre core layering Core1, its refractive index contrast Δ % _Core1Be about 0.788%, its diameter R _Core1Be about 4.1 μ m.

-the second fibre core layering Core2, its refractive index contrast Δ % _Core2Be about 0.521%, its diameter R _Core2Be about 5.5 μ m.

-Di three fibre core layering Core3, its refractive index contrast Δ % _Core3Be about 0.200%, its diameter R _Core3Be about 6.4 μ m.

-the first covering layering Clad.1, its refractive index contrast Δ % _Clad.1Be about-0.033%, its diameter R _Clad.1Be about 10.5 μ m.

-the second covering layering Clad.2, its refractive index contrast Δ % _Clad.2Be about 0.160%, its diameter R _Clad.2Be about 18.1 μ m.

-Di triple clad layering Clad.3, its refractive index contrast Δ % _Clad.3Be about 0.033%, its diameter R _Clad.3Be about 22.0 μ m.

-Di four covering layering Clad.4, its refractive index contrast Δ % _Clad.4Be about 0.0%, its diameter R _Clad.4Be about 24.5 μ m.

-Di five covering layering Clad.5, its refractive index contrast Δ % _Clad.5Be about 0.0%, its diameter R _Clad.5Be about 33.1 μ m.

-Di six covering layering Clad.6, its refractive index contrast Δ % _Clad.6Be about 0.0%, its diameter R _Clad.6Be about 125 μ m.

Three sandwich layer layering Core1 of this invention optical fiber, Core2, the Clad.1 in Core3 and the covering layering, Clad.2, Clad.3 are the pure silicon dioxide (SiO that PCVD technology provides ₂) sedimentary deposit of matrix doped germanium (Ge) and fluorine (F), the pure silicon dioxide (SiO that the Clad.4 in its covering layering provides for PCVD technology ₂) sedimentary deposit, the Clad.5 in its covering layering, the pure silicon dioxide (SiO that Clad.6 provides for OVD technology ₂) sedimentary deposit.

These inventive embodiments 3 optical fiber have following characteristic:

-dispersion characteristics

1550nm abbe number :-6.8ps/nm.km

1600nm abbe number :-3.4ps/nm.km

1525nm to 1625nm abbe number scope :-1.0ps/nm.km is to-10.0ps/nm.km

1550nm chromatic dispersion gradient: 0.061ps/nm ².km

Zero-dispersion wavelength: 1645nm

-attenuation characteristic

1550nm attenuation coefficient: 0.222dB/km

1600nm attenuation coefficient: 0.219dB/km

-cable optical fiber cutoff wavelength λ not _c: 1450nm to 1540nm

-1550nm mode field diameter MFD:7.8 μ m

-1550nm useful area A _Eff: 48 μ m ²

-macrobending loss (75mm mandrel, 100 circles)

1550nm：≤0.02dB

1625nm：≤0.02dB

-hydrogen loss characteristic (1%H ₂Add 99%He, 70 ℃ are incubated 16 hours)

1530nm：≤0.001dB/km

-cable optical fiber PMD coefficient :≤0.035ps/km not ^1/2

These inventive embodiments 3 described single-mode fibers have total dispersion at C-band (1525nm-1565nm) and L-band (1565nm-1625nm) optical communication window and are negative dispersion characteristics and positive chromatic dispersion gradient.Wherein C-band is the service band of EDFA, and L-band is that wave band is used in the expansion of dwdm optical communication system.This optical fiber can satisfy the transmission requirement of long distance or middle and long distance dwdm optical communication system, can support the DWDM technology of the 2.5Gbps/10Gbps speed of the following channel spacing of 100GHz.This optical fiber has satisfied the needs that reduce the PMD value of the type optical fiber.In addition, this optical fiber has also satisfied the counter-bending characteristic of improving the type optical fiber and the needs of anti-hydrogen loss characteristic.

This negative dispersion optical fiber with have the direct intensity modulated laser instrument of just warbling when being used in 2.5Gbps, can produce light pulsewidth pinch effect, thereby prolong dispersion limit.Its dwdm system for the middle and long distance transmission is highly beneficial, can reduce the dispersion compensation expense, and can avoid using expensive external modulator, thereby can reduce the cost of optical transmission device.

Claims (9)

1, a kind of monomode fiber with negative dispersion has a core layer and a covering, it is characterized in that fibre core is provided with three different fibre core layerings of index distribution, and covering includes six layerings, the diameter R of the described optical fiber first fibre core layering Core1 _Core1Be about 1.0 μ m to 5.0 μ m, its refractive index contrast Δ % _Core1The diameter R that is about 0.6% to 1.2%, the second fibre core layering Core2 _Core2Be about 3.0 μ m to 6.0 μ m, its refractive index contrast Δ % _Core2The diameter R that is about 0.25% to 0.65%, the three fibre core layering Core3 _Core3Be about 4.0 μ m to 8.0 μ m, its refractive index contrast Δ % _Core3The diameter R that is about 0.05% to 0.25%, the first covering layering Clad.1 _Clad.1Be about 8.0 μ m to 12.0 μ m, its refractive index contrast Δ % _Clad.1The diameter R that is about-0.15% to 0.15%, the second covering layering Clad.2 _Clad.2Be about 12.0 μ m to 20.0 μ m, its refractive index contrast Δ % _Clad.2The diameter R that is about 0.1% to 0.4%, the triple clad layering Clad.3 _Clad.3Be about 18.0 μ m to 30.0 μ m, its refractive index contrast Δ % _Clad.3Be about-0.1% to 0.1%, the four, five, six covering layering Clad.4, Clad.5, Clad.6, its diameter R _Clad.4, R _Clad.5, R _Clad.6Be respectively 20.0 μ m to 40.0 μ m, 30.0 μ m to 50.0 μ m, 123.0 μ m to 126.0 μ m, its refractive index is the pure silicon dioxide refractive index, be constant refractive index, described optical fiber is under the crooked situation in 100 weeks on the 75mm diameter axle, because the crooked loss that causes is not more than 0.02dB at 1550nm, be not more than 0.02dB at 1625nm, cable optical fiber PMD coefficient is not less than 0.036ps/km ^1/2Clad.3 in the covering layering applies the germanium of 2.0% to 5.0% volumetric molar concentration, described optical fiber has at 1525nm to 1565nm wave band-and 1.0ps/nm.km is to the negative dispersion of-10.0ps/nm.km, perhaps, described optical fiber have at 1525nm to 1625nm wave band-1.0ps/nm.km is to the negative dispersion of-10.0ps/nm.km.

2, by the described negative throwaway mode fiber of claim 1, it is characterized in that the parameter distribution of fibre core and covering is:

Δ % _Core1Be about 0.69% to 0.85% R _Core1Be about 3.45 to 4.22 μ m

Δ % _Core2Be about 0.47% to 0.57% R _Core2Be about 4.62 to 5.65 μ m

Δ % _Core3Be about 0.17% to 0.22% R _Core3Be about 5.46 to 6.67 μ m

Δ % _Clad.1Be about-0.06% to 0.06% R _Clad.1Be about 8.52 to 10.42 μ m

Δ % _Clad.2Be about 0.14% to 0.17% R _Clad.2Be about 15.27 to 18.66 μ m

Δ % _Clad.3Be about 0.03% to 0.04% R _Clad.3Be about 19.83 to 24.24 μ m

Δ % _Clad.4Be about 0% R _Clad.4Be about 21.72 to 26.55 μ m

Δ % _Clad.5Be about 0% R _Clad.5Be about 30.0 to 36.41 μ m

Δ % _Clad.6Be about 0% R _Clad.6Be about 123 to 125 μ m.

3, by claim 1 or 2 described monomode fiber with negative dispersion, it is characterized in that described optical fiber has the mode field diameter MFD that is not less than 7.6 μ m at 1550nm; Have at 1550nm and be not less than 45 μ m ²Useful area A _EffDescribed optical fiber has at 1550nm and is not more than 0.1ps/nm ².km chromatic dispersion gradient; Has the not cable optical fiber cutoff wavelength λ that is not more than 1700nm _c

4, a kind of method of making the described monomode fiber with negative dispersion of claim 1, it is characterized in that described single-mode fiber is to be drawn with preform by Gong the wire drawing that PCVD technology and OVD technology provide jointly to form, and each layering of this preform and each layering of single-mode fiber are one to one, each stratified sedimentation technology of described preform is: sandwich layer layering Core1, Core2, Core3, covering layering Clad.1, Clad.2, Clad.3, the sedimentary deposit that Clad.4 provides for PCVD technology; Covering layering Clad.5, the sedimentary deposit that Clad.6 provides for OVD technology, and provide the pure silicon dioxide bushing pipe to be covering layering Clad.5 by OVD technology.

5, press the method for the described manufacturing monomode fiber with negative dispersion of claim 4, it is characterized in that described preform sandwich layer layering Core1, Core2, Core3 are pure silicon dioxide matrix doped germanium, or mix germanium and fluorine altogether to form required positive relative index of refraction difference cloth for the pure silicon dioxide matrix; Clad.1 in the described optical fiber prefabricating stick cladding layering, Clad.2, Clad.3 are pure silicon dioxide matrix doped germanium or doped with fluorine, or are that the pure silicon dioxide matrix is mixed germanium altogether and fluorine distributes with the refractive index contrast that forms required plus or minus; Clad.4 in the described optical fiber prefabricating stick cladding layering, Clad.5, Clad.6 are the pure silicon dioxide layer.

6, press the method for claim 4 or 5 described manufacturing monomode fiber with negative dispersion, it is characterized in that applying among the described optical fiber prefabricating stick cladding layering Clad.3 the anti-hydrogen loss performance of the germanium of 2.0% to 5.0% volumetric molar concentration, and in Clad.3, apply the optical waveguide structure of fluorine doping simultaneously to realize presetting with raising optical fiber.

7, press the method for the described manufacturing monomode fiber with negative dispersion of claim 6, it is characterized in that applying among the described optical fiber prefabricating stick cladding layering Clad.3 germanium of 3.5% volumetric molar concentration, and apply the fluorine doping of satisfying default optical waveguide structure required amount simultaneously, finish drawing back optical fiber and cause loss less than 0.002dB/km at the hydrogen of 1530nm.

8, by the method for claim 4 or 5 described manufacturing monomode fiber with negative dispersion, it is characterized in that the electricity consumption collapsar technics finishes molten the contracting of described PCVD process deposits bushing pipe, described optical fiber prefabricated rod mandrel is provided.

9, press the method for the described manufacturing monomode fiber with negative dispersion of claim 8, it is characterized in that providing the axial bow degree of described optical fiber prefabricated rod mandrel to be lower than 0.1mm by the electric smelting technology that contracts, each core bag layering out-of-roundness index is lower than 1.0%, finishes after the drawing not cable optical fiber PMD coefficient less than 0.036ps/km ^1/2

Images