CN106443885B - A method of realizing photonic crystal fiber and solid core fibres low loss welding - Google Patents
A method of realizing photonic crystal fiber and solid core fibres low loss welding Download PDFInfo
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Abstract
The invention belongs to optical design techniques, are related to a kind of method for realizing photonic crystal fiber Yu solid core fibres low loss welding.The present invention derives that airport collapses the numerical relation between degree and carbon dioxide laser discharge parameter by the thermo parameters method model and airport stress model established under photonic crystal fiber and solid core fibres molten condition.Again by establishing the numerical relation of photonic crystal fiber end face structure Yu its effective core area, the loss model of photonic crystal fiber Yu solid core fibres welding is obtained, and then accurately calculate the carbon dioxide laser discharge parameter for realizing low loss welding.The present invention can control photonic crystal fiber air pore structure, so that photonic crystal fiber and effective mould field of the solid plain optical fiber in molten condition is reached best match state, and then reduce splice loss, splice attenuation by accurately calculating to carbon dioxide laser discharge parameter.
Description
Technical field
The invention belongs to optical design techniques, it is related to a kind of photonic crystal fiber and solid core fibres low loss welding realized
Method.
Background technique
Photonic crystal fiber (Photonic Crystal Fiber, PCF) or be microstructured optical fibers (Micro-
Structure Fiber, MSF), it is a kind of novel optical fiber occurred the nearly more than ten years, has significant difference with conventional tubeless optical fiber
New special optical fiber.The optical fiber of this structure is regularly dispersed with many airports along light axial direction, changes airport
Size and arrangement mode, it will change the characteristic of output light, this peculiar feature make it be expected to develop it is various novel
Opto-electronic device, special optical fiber, therefore photonic crystal fiber will be widely used in optic communication and optoelectronic areas.
But developmental research these in application, be directed to the interconnection technique of photonic crystal fiber, it is living that optical fiber can be passed through at present
Movement connector, arc discharge welding mode, carbon dioxide laser welding mode carry out photonic crystal fiber and solid plain light
Connection between fibre.And carbon dioxide laser welding mode is with its high-absorbility (wavelength 10.6um), the shape and energy of laser
Amount is controllable, but the advantages such as dye and residue become the preferred manner of photonic crystal fiber and solid plain fused fiber splice.
However on the one hand since photonic crystal fiber and solid plain optical fiber structure, physical parameter all have differences, simultaneously
The presence of special air pore structure existing for photonic crystal fiber can go out in carbon dioxide laser electric discharge heating process
Now the phenomenon inconsistent with the temperature rise of solid plain optical fiber, profiling temperatures, melting situation influences splice loss, splice attenuation；It on the other hand can
Reduce splice loss, splice attenuation by matching photonic crystal fiber and solid plain optical fiber mode fields, and the effective mould field face of photonic crystal fiber
Product depends on the photonic crystal fiber air pore structure after the completion of welding.Therefore, it is necessary to by the temperature in electric discharge heating process
Field distribution numerical analysis and emulation are spent, the method for developing a set of control photonic crystal fiber air pore structure parameter is accurate real
While existing two sides fiber fuse, control photonic crystal fiber airport, which collapses degree, makes two kinds of effective mould fields of optical fiber reach best
Matching, so that splice loss, splice attenuation be made to be reduced to minimum.
Summary of the invention
The purpose of the present invention: providing one kind by controlling photonic crystal airport and collapse degree, realizes photonic crystal fiber
With the method for solid core fibres low loss welding.
Technical solution of the present invention: a method of it realizing photonic crystal fiber and solid core fibres low loss welding, leads to
The thermo parameters method model and airport stress model established under photonic crystal fiber and solid plain fiber fuse state are crossed,
Two sides fiber optic temperature situation of change and air hole wall stress condition in discharge process are simulated, and then derives that airport collapses journey
Numerical relation between degree and carbon dioxide laser discharge parameter, then have by establishing photonic crystal fiber end face structure with it
The numerical relation for imitating mode field area, obtains the loss model of photonic crystal fiber Yu solid core fibres welding, and then accurately calculate
Realize the carbon dioxide laser discharge parameter of low loss welding.
Carbon dioxide laser discharge parameter includes discharge centers position, discharge time, discharge capacity.
The method of the realization photonic crystal fiber and solid core fibres low loss welding, the specific steps of which are as follows:
Step 1: establishing two optical fiber effective core areas and splice loss, splice attenuation model
The high birefringence characteristic of photonic crystal fiber is formed by the geometry of its two great circle of immediate vicinity, according to
The electromagnetic theory of light calculates, when light is bound in fiber optic hub, the electric field strength at electric-field intensity distribution photonic crystal fiber center
It is distributed E1；The field distribution E2 in solid plain fiber core is calculated simultaneously；
When high birefringence type photonic crystal fiber and panda protecting polarized light fiber couple, emergence pattern is converted in abrupt interface,
A portion and the mode of waveguide match, and continuation is propagated in the waveguide；Another part and the mode of waveguide mismatch, and become
It is lost at radiation mode, this portion of energy lost becomes coupling mismatch loss, is calculated by the pattern match of two waveguides
Coupling efficiency, and then can establish the model of two optical fiber effective core areas and splice loss, splice attenuation；
Step 2: the analysis of photonic crystal fiber thermal conduction characteristic
The thermal conduction characteristic being heated to photonic crystal fiber is analyzed, and is obtained under different carbon dioxide laser discharge parameters
Photonic crystal fiber thermo parameters method model；
Step 3: thermal conduction characteristic is analyzed when photonic crystal fiber and solid plain fused fiber splice
In conjunction with step 2 photonic crystal fiber thermo parameters method model, photonic crystal fiber and solid plain optical fiber welding are carried out
Thermal conduction characteristic analysis when connecing, and then establish the thermo parameters method mould of two optical fibers under different carbon dioxide laser discharge parameters
Type；
Step 4: mechanical characteristic analysis when photonic crystal fiber and solid plain fused fiber splice
In conjunction with the two sides fiber optic temperature field distribution model under the different carbon dioxide laser discharge parameters of step 3, establish molten
The relationship and photonic crystal fiber flow equation for melting photonic crystal fiber viscosity coefficient and temperature under state, according to photonic crystal light
The flow process at gas-liquid two-phase interface in fibre carries out its quartz-Air Interface using the Level Set Method in biphase gas and liquid flow
Tracking, obtains quartzy liquid surface equation of motion under surface tension, and then establish different carbon dioxide laser discharge parameters
Lower photonic crystal fiber air micro pore structure；
Step 5: establishing the numerical model of carbon dioxide laser discharge parameter and splice loss, splice attenuation
In conjunction with photonic crystal fiber air micro pore structure under the different carbon dioxide laser discharge parameters of step 4, and
Step 1 photonic crystal fiber and solid plain optical fiber effective core area and loss model establish carbon dioxide laser electric discharge
The numerical relation of parameter and splice loss, splice attenuation；
Step 6: low loss welding parameter determines
It is minimum molten in order to obtain in conjunction with the numerical model of step 5 carbon dioxide laser discharge parameter and splice loss, splice attenuation
Loss is connect, that is, needs to realize the best match of two sides optical fiber mode fields, acquires photonic crystal fiber air pore structure under molten condition,
And then it can derive the carbon dioxide laser discharge parameter that above structure to be obtained needs: discharge capacity, discharge time, electric discharge
Center.
When determining discharge time, discharge centers position delta can be obtained by formula (1)
Z=-419.6delta2-0.945delta+7.943×10-5 (7)
Wherein, Z is fiber end face axial coordinate.
Discharge capacity is in the case where determining discharge time, and by the position z=0, the relation curve of temperature and discharge time are determined.
In the case where determining discharge time, at the position z=0, the relation curve of temperature and discharge time, as shown in formula (8)
Silica viscosity coefficient μ is determined
Wherein, T is temperature relevant to discharge time.
The degree influence that collapses of photonic crystal fiber airport collapses area, to influence fiber coupling, two optical fibers exist
Optical coupling efficiency when abrupt interface matches emergence pattern, it is determining by formula (5),
Wherein, E1(x, y) and E2(x, y) is respectively two mode distributions of two optical fibers in abrupt interface.
The advantages of the present invention are: by establishing under photonic crystal fiber and solid plain fiber fuse state
Thermo parameters method model and airport stress model, simulate discharge process in two sides fiber optic temperature situation of change and air
Hole wall stress condition, and then derive and collapse degree by airport (discharge centers position is put with carbon dioxide laser discharge parameter
Electric time, discharge capacity) between numerical relation, pass through the numerical model of two optical fiber effective core areas and splice loss, splice attenuation derive
The effective mode field diameter of photonic crystal fiber after cooling down out, and then accurately calculate the discharge parameter (electric discharge of carbon dioxide laser
Center, discharge time, discharge capacity).On the one hand can accurately calculate before fusing operation implementation in this way can make two sidelights
It is fine to reach molten condition simultaneously, and maximum temperature point appears in the carbon dioxide laser discharge parameter of interface, avoids specific
Operation failure bring is lost during production operation, and reduction is done over again；It on the other hand can be by being put to carbon dioxide laser
Electrical parameter accurately calculates, and can control photonic crystal fiber air pore structure, makes photonic crystal fiber and solid plain optical fiber
Effective mould field in molten condition reaches best match state, and then minimizes splice loss, splice attenuation after cooling.
Detailed description of the invention
Fig. 1 is the isogram of photonic crystal fiber electric field effective model；
Fig. 2 is that carbon dioxide laser heating is melt optical fiber schematic diagram；
Fig. 3 is carbon oxide laser device heating photonic crystal fiber schematic diagram；
Fig. 4 is the temperature distribution history of two optical fiber of t=300ms；
Fig. 5 is the photonic crystal end view for causing airport to collapse at temperature and surface tension effects；
Fig. 6 is the relation curve of viscosity and temperature；
Fig. 7 end face temperature and time curve；
The contraction situation of airport when Fig. 8 0.5s；
Fig. 9 shrinks front and back model comparison；
Photonic crystal fiber mode after Figure 10 is shunk.
Specific embodiment
The present invention will be further described below with reference to the drawings:
The present invention realizes photonic crystal fiber with the method for solid core fibres low loss welding by establishing photonic crystal fiber
With the thermo parameters method model and airport stress model under solid plain fiber fuse state, two sides in discharge process are simulated
Fiber optic temperature situation of change and air hole wall stress condition, and then derive that airport collapses degree and carbon dioxide laser
Numerical relation between discharge parameter.It is closed again by establishing the numerical value of photonic crystal fiber end face structure and its effective core area
System, obtains the loss model of photonic crystal fiber Yu solid core fibres welding, and then accurately calculates and realize the two of low loss welding
Carbon oxide laser device discharge parameter.
Detailed process includes the following steps:
Step 1: establishing two optical fiber effective core areas and splice loss, splice attenuation model
The guiding property of photonic crystal fiber is to determine that high birefringence characteristic is by several layers of airport of immediate vicinity
It is formed by the geometry of its two great circle of immediate vicinity.According to the electromagnetic theory of light, using the method for finite element, by following formula
Based on can analyze the mode of photonic crystal fiber.
εr=(n-jk)2 (3)
Wherein, E is electric field strength, k0For wave number in vacuum, εrFor relative dielectric constant, β is propagation constant, and n is refraction
Rate.(1) formula is Helmholtz equation, and (2) formula is to separate the z-component of electric field, (3) formula be refractive index and relative dielectric constant and
The relationship of wave number.According to (2) formula, (1) formula can be converted to x, the electric field equation on y plane.According to (3) formula, (1) formula can be turned
Turn to equation relevant to refractive index.
Light includes many modes, each mode and corresponding effective refractive index are corresponding when entering optical fiber.Due to optical fiber
The limitation of structure, only specific mode may exist.Therefore, using finite element method to photonic crystal fiber Refractive Index of Material
Neighbouring effective refractive index is screened, and the mode that can be propagated in fibre core, electric field of the communication mode on end face can be obtained
It is distributed as E1(x, y), as shown in Fig. 1.
For panda type single-mode polarization maintaining fiber, light intensity is distributed as Gaussian in cross section, if mode field diameter is 2 ω
(in 1/e2At light intensity), the mode distributions of Gaussian beam indicate are as follows:
When high birefringence type photonic crystal fiber and panda protecting polarized light fiber couple, emergence pattern is converted in abrupt interface,
A portion and the mode of waveguide match, and continuation is propagated in the waveguide；Another part and the mode of waveguide mismatch, and become
It is lost at radiation mode, this portion of energy lost becomes coupling mismatch loss, therefore its coupling efficiency η can be obtained are as follows:
Step 2: the analysis of photonic crystal fiber thermal conduction characteristic
Laser has the characteristics that high monochromaticity, high coherence, high directivity and high brightness, it is a kind of ideal hot, light
The energy.The wavelength of carbon dioxide laser is 10.6um, and photon energy 0.176eV cannot much smaller than the ionization energy of compound
Compound is directly resulted in chemically react.
The operating mode of carbon dioxide laser is TEM00, and light beam is Gaussian Profile, and hot spot is circle, laser irradiation region
Relative position schematic diagram is as shown in Fig. 2 between optical fiber.
Laser radiation rate is
Wherein, PtotalFor general power, Wy, WzRespectively carbon dioxide laser light beam irradiates the circular light spot y, z to be formed
The radius of field.
Since the material of solid PCF is silica, fusing point is (1700 ± 5) K, and welding photonic crystal fiber both required
The temperature of welding area can reach fusing point, and can not be too high, in order to avoid collapsing for airport is caused, and welding in order to obtain
The preferable photonic crystal fiber of quality needs fibre core and covering while reaching fusing point.As long as by heat transfer theory it is found that cross section
The temperature difference of covering and fibre core is less than 1%, so that it may think that they have reached unified temperature.In addition, since laser energy is in light
Fine length direction is in Gaussian Profile, carries out three-dimensional artificial to fiber optic temperature field, studies the effect of airport in photonic crystal fiber
With the control to welding condition.
Attached drawing 3 show the experimental provision schematic diagram using carbon dioxide laser heating photonic crystal fiber, z=in figure
0 position, that is, photonic crystal fiber left side is located at the center of laser irradiation region.
Using parameter shown in attached drawing 3 and photonic crystal fiber One-dimensional Heat Conduction Equation as boundary condition, establish and dioxy
Change the relevant photonic crystal fiber distribution of three-dimensional temperature model of carbon laser discharge parameter.
Step 3: thermal conduction characteristic is analyzed when photonic crystal fiber and solid core fibres welding
Numerical value emulation method based on step 2 will calculate laser power required for solid PCF and PM fused fiber splice and put
Electric time, the offset for needing the center for calculating laser irradiation region first to deviate to the solid direction PCF.Offset is determined
Justice are as follows: two end centre of optic fibre positions are offset zero point when welding, mobile to PM optical fiber direction, and offset is positive；To photon
Crystal optical fibre direction is mobile, and offset is negative.The value of offset is laser irradiation region center to (x=0, y=0, z=0)
The distance of point.
Since there are two when controllable splicing parameter, i.e. laser power P and electric discharge when carbon dioxide is for fused fiber splice
Between t, meanwhile, the particularity for solid PCF and when PM fused fiber splice, there is also in third splicing parameter, that is, laser irradiation region
The position delta of the heart.Needing exist for calculating can make two kinds of optical fibre interface positions (i.e. the position of z=0) to be entirely to be heated area
The thermal self-restraint stress in domain, the heated center position delta of carbon dioxide laser and two optical fibre interface positions be (i.e. z=0's
Position) at temperature curve and laser heating power P, heating time t relationship.To power P under different time in table 1, swash
The value of light irradiated site center delta is emulated.
1 simulated conditions parameter list of table
Under available determining heating time, when corresponding to different capacity P and different heating center z, solid PCF and PM optical fiber
On temperature distribution history.
Simulation numerical result under the determining time is analyzed, the position delta of thermal self-restraint stress is only in heated center z
Position it is related, it is unrelated with heating power, thus can to the position delta of heated center z and thermal self-restraint stress carry out it is secondary
Item fitting, as a result as shown in formula (5).
Z=-419.6delta2-0.945delta+7.943×10-5 (7)
Heated center position when can appear in two optical fibre interfaces in the hope of the position of thermal self-restraint stress, i.e. when z=0
Delta is as shown in table 2.
The numerical result of the corresponding different heating time heated center position of table 2
| Serial number | Carbon dioxide laser heating time T (ms) | Heated center position delta (um) | Thermal self-restraint stress position Z (um) |
| 1 | 300 | 113.68 | 0 |
| 2 | 350 | 90.22 | 0 |
| 3 | 400 | 88.42 | 0 |
| 4 | 450 | 86.5 | 0 |
| 5 | 500 | 81.1 | 0 |
Followed by heating power P and temperature maximum T linear fit, available two optical fibre interface position (i.e. z
=0 position) at temperature curve and laser heating power P, heating time t relational model.It is as shown in Fig. 4 t=
300ms, corresponding different offset delta, under different heating power, the temperature curve of two optical fibers is distributed.
Step 4: mechanical characteristic analysis when photonic crystal fiber and solid plain fused fiber splice
It is quartzy liquid after photonic crystal fiber melted by heating, the interface of quartzy liquid-to-air is in micro molecule power
Under effect, macroscopic view forms surface tension, and surface tension shrinks the airport in quartzy liquid, and shrinking law meets hydrodynamics
It is theoretical.Since the viscosity of air, density are much smaller than quartzy liquid, only study this incompressible fluid of quartzy liquid
Flow field under surface tension effects.
Meanwhile according to the two sides fiber optic temperature field distribution model under the different carbon dioxide laser discharge parameters of step 3, push away
It exports under quartzy photonic crystal fiber molten condition, thermo parameters method and viscosity coefficient model, and then establishes light under molten condition
Photonic crystal fiber flow equation, as shown in formula (8) (9), (10).
Wherein, FstFor surface tension, U is flow field velocity, and ρ is the density at research point, and I is unit matrix, and t is the time, μ
For viscosity.Formula (9), (10) derive from the Navier-Stokes equation of fluid flowing.
In formula (9), the surface tension for acting on gas-liquid two-phase interface is related with surface tension coefficient, curvature, thus builds
The Surface Tension Equation of vertical (10).
Fst=σ κ δ n (11)
σ is surface tension coefficient in formula (11), and κ is curvature, and δ is that Dirac function (is 1 at gas-liquid interface, at it
His position is that 0), n is the normal unit vector of interface.
In formula (7), viscosity, mu is the function of end face temperature, and with the raising of end face temperature, viscosity value becomes smaller.By step
Three can obtain, and end face temperature is the function of carbon dioxide laser heating time, heating location and heating power.Ignore quartzy liquefaction
Change caused by Shi Midu and latent heat of liquefaction, it is known that the contraction of photonic crystal fiber end face airport adds with carbon dioxide laser
Hot time, heating location and heating power are related.Gravity item is not included in formula (8), since surface tension is much larger than gravity, therefore not
Consider the influence that gravity shrinks photonic crystal fiber.
According to the flow process at gas-liquid two-phase interface in photonic crystal fiber, the Level Set Method in biphase gas and liquid flow is used
Its quartz-Air Interface is tracked, it is shown to obtain the quartzy liquid surface equation of motion such as formula (11) under surface tension.
In formula, γ is again initiation parameter, and ε is interfacial thickness parameter, and φ indicates the substance ratio at two fluid interfaces
Example, ρ ' are the equivalent density of intersection, and μ ' is the equivalent viscosity of intersection, ρ1For quartzy fluid density, ρ2It is close for air gas
Degree, μ1For quartzy liquid viscosity, μ2For air gas viscosity.It is quartzy liquid when defining φ < 0.5 according to the physical significance of φ,
It is air fluid when φ > 0.5.
Under conditions of ignoring atmospheric density and viscosity, it is interior under surface tension effects that quartzy liquid is analyzed according to (9) formula
The flow field velocity in portion is distributed, and the Interface Moving of quartzy liquid outer boundary is analyzed according to (12) formula.Convolution (9) and formula (12), according to
By finite element analysis means, the position of the point by calculating φ=0.5, i.e., traceable quartzy liquid surface is transported under surface tension
Dynamic process, and then establish photonic crystal fiber air micro pore structure under different carbon dioxide laser discharge parameters.Attached drawing 5
Show the heating by carbon dioxide laser, airport collapse after surface texture schematic diagram.
Step 5: establishing the numerical model of carbon dioxide laser discharge parameter and splice loss, splice attenuation
According to the knot of photonic crystal fiber and solid plain optical fiber in the mould field loss model and practical application of step 1
The calculating of structure parameter meets lowest loss requirement, the matched effective core area of two optical fibers, and then acquires to be heated and collapse rear photon
The end face structure of crystal optical fibre.
It is thermal self-restraint stress by the position that reach two sides interface (i.e. z=0) under different discharge times that step 3 acquires
Corresponding heated center position, and when different discharge times t, discharge power P, the position of (i.e. z=0) at the optical fibre interface of two sides
Simulated conditions of the temperature curve as step 4, and then simulation calculation goes out to obtain photonic crystal fiber when the matching of final mould field
End face structure, discharge parameter (the discharge time t, discharge centers position delta, and electric discharge of the carbon dioxide laser needed
Power P).
Embodiment 1
The invention proposes a kind of collapsed by control photonic crystal fiber airport to realize itself and solid core fibres low-loss
The method of welding.The following are specific embodiments.
Or less in the present embodiment, point four steps are calculated:
(1) according to the analysis of step 3, high double-refraction photon crystal fiber and panda protecting polarized light fiber welding when, optical fiber axial direction
Maximum temperature position is unrelated with carbon dioxide laser heating power, related with heating time, heating location.Therefore, it may specify
Heating time and heating location make its temperature highest at two kinds of optical fiber interfaces, and carbon dioxide laser then can be changed and add
Thermal power acquires photonic crystal fiber end face structure appropriate, so that splice loss, splice attenuation is minimum.This example selects a carbon dioxide
Laser heating power is determining heating time, is determining under heating location, calculates splice loss, splice attenuation.
(2) under above-mentioned selected carbon dioxide laser heating power, heating time, heating location, two kinds of light are calculated
Fine Axial Temperature Distribution.By the relationship of two kinds of optical fiber intersection temperature and times with Polynomial curve-fit, obtain temperature when
Between function:
T=T (t) (13)
(3) in the mechanical model described in step 4, by temperature T=T (t) as inputting, change viscosity with temperature, count
The airport calculated under viscosity change is shunk.After contraction, its effective model is calculated according to the shrinkage in hole and position.To have
Electric field strength output under effect mode.
(4) according to the electric field strength under photonic crystal fiber effective model, with the theory of step 1, computed losses.
Before starting calculating, the structure size for providing solid photonic crystal fiber first is as shown in table 3, in calculating process
Required physical parameter is as shown in table 4.
The solid PCF airport structure size table of table 3
| Serial number | Title | Length (um) |
| 1 | Fibre cladding outer diameter | 80 |
| 2 | Core diameter (x) | 4.09 |
| 3 | Core diameter (y) | 8.18 |
| 4 | Pitch of holes | 5.75 |
| 5 | Diameter macropores | 7.21 |
| 6 | Hole diameter | 3.9 |
4 physical parameter table of table
| Symbol | Definition | Value | Unit |
| CSiO2 | Quartzy specific heat capacity | 1345 | J.Kg-1.K-1 |
| Cair | Air specific heat capacity | 1010 | J.Kg-1.K-1 |
| D | Fibre diameter | 80 | um |
| R | Fiber radius | 40 | um |
| I | Carbon dioxide laser irradiation level | See formula (1) | W.m-2 |
| Ptotal | The output power of laser | It is undetermined | W |
| q | Heat flow density | See formula (8) | W.m-3 |
| Qabs | Absorption coefficient | 3E-5 | Dimensionless |
| t | Time | It is undetermined | ms |
| T | Melting temperature | 1700 | K |
| Wy, Wz | The beam width in the direction y, z | 1.5 | mm |
| Wabs | S. E. A. | / | W |
| SiO2 | Quartzy density | 2200 | Kg.m-3 |
| air | Atmospheric density | 0.93 | Kg.m-3 |
| kSiO2 | Quartzy pyroconductivity | 2.68 | W.m-1.K-1 |
| Kair | Air pyroconductivity | 0.032 | W.m-1.K-1 |
With reference to the accompanying drawings 2, definition optical fiber axial direction is the direction z, and the range in the direction photonic crystal fiber z is 0mm < z < 3mm, panda
The range in the direction optical fiber z is -3mm < z < 0mm, and the range of carbon dioxide laser heating is -1.5mm < z < 1.5mm.Selected heating
Time is 500ms, and selecting heating power is 1.7W.
To find out under selected heating time, make the carbon dioxide laser heated center of two optical fiber intersection maximum temperatures
Offset, selecting carbon dioxide laser heated center position in the offset of z-axis negative sense is delta=0:30um:300um.I.e.
Since offset is 0, selects an offset point to be calculated every 30um, terminate to offset for 300um.According to each inclined
The maximum temperature position function for moving point fits maximum temperature in the offset of two optical fiber intersections.Heat source range after offset
It, using finite element analysis as means, is calculated selected under with upper boundary conditions for -1.5mm-delta < z < 1.5mm-delta
Heating time is 500ms, and selecting heating power is 1.7W, and the maximum temperature position under each offset is as shown in table 5.
Maximum temperature and position under each offset of table 5
| delta(um) | Position (um) | Maximum temperature (K) |
| 0 | 81 | 1922.331 |
| 30 | 42 | 1917.443 |
| 60 | 27 | 1912.583 |
| 90 | -6 | 1907.861 |
| 120 | -36 | 1902.986 |
| 150 | -72 | 1898.256 |
| 180 | -111 | 1893.655 |
| 210 | -138 | 1889.204 |
| 240 | -171 | 1885.176 |
| 270 | -207 | 1881.061 |
| 300 | -240 | 1877.102 |
Maximum value position z and offset delta are made into fitting of a polynomial, obtained:
Z=-419.6delta2-0.945delta+7.943×10-5 (14)
Z=0 is enabled, acquiring offset is delta=81.13um.I.e. when heated between under 500ms so that two optical fiber are handed over
The highest carbon dioxide laser center offset of interface temperature is 81.13um.Maximum temperature is observed, is 1900K or so, herein
At a temperature of quartzy liquid viscosity it is very big, be unfavorable for the contraction (will be specifically described later) of photonic crystal fiber airport.By
It is unrelated with its heating power in carbon dioxide laser center offset, so after improving heating power, carbon dioxide laser
Center offset is still 81.13um.
Heating power is taken a bit every 0.1W to originate with 1.8W, until 2.5W terminates, acquired under each power most
Big temperature is as shown in table 6:
Maximum temperature under 6 different heating power of table
| Power (W) | 1.8 | 1.9 | 2.0 | 2.1 | 2.2 | 2.3 | 2.4 | 2.5 |
| Maximum temperature (K) | 2006 | 2101 | 2197 | 2292 | 2388 | 2483 | 2579 | 2675 |
The boiling point of quartzy liquid is about 2600K, when selecting heating power, should ensure that the maximum temperature under this heating power is small
In 2600K.In the unmatched situation of mode field diameter, it should select certain temperature that the viscosity of quartzy liquid is made to meet contraction and want
It asks, and then keeps the shrinkage of airport certain, the mould field formed after shrinking it meets requirement.
The viscosity of quartz and the relationship of temperature are as shown in Fig. 6, and viscosity number reduces index decreased with temperature, and airport is shunk
Speed is also accelerated therewith.It (is obtained by the contraction process of hereinafter airport) according to calculating, the photonic crystal fiber in the present invention
It is 10 in viscosity value5When (corresponding temperature 2100K or so), contraction speed is about 0.7um/s.
In this example calculating, according to the relationship of temperature and quartzy liquid viscosity, carbon dioxide laser heating power is selected
For 2.2W.In the case where carbon dioxide laser power is 2.2W, the temperature in 0~0.5s time is as shown in Fig. 7.
With the curve in quadratic polynomial fitted figure 8, the relationship of temperature and time is obtained are as follows:
T=-1882t2+ 5094t+302.1 (0 < t < 0.5) (15)
Thus the relationship of viscosity and time, i.e. μ=μ (T (t)) can be established.
According to the theory analysis of step 4, the contraction situation in 0~0.5s airport is calculated.Gained shrinkage such as Fig. 8 institute
Show, can be obtained from the numerical value of shrinkage, the shape after photonic crystal fiber airport is shunk is approximately round, the shape of airport arrangement
Formula is still triangle, and whole airports still constitute approximate regular hexagon.
Photonic crystals optical fiber structure after contraction is as shown in table 7 compared with primary photon crystal optical fibre structure:
7 photonic crystal fiber of table shrinks front and back parameter and compares
| Serial number | Title | Before contraction (um) | After contraction (um) |
| 1 | Fibre cladding outer diameter | 80 | 76.62 |
| 2 | Pitch of holes | 5.75 | 5.00 |
| 3 | Diameter macropores | 7.21 | 5.18 |
| 4 | Hole diameter | 3.9 | 2.65 |
The modeling of photonic crystal fiber end face is carried out, according to upper table to carry out the calculating of effective model.Shrink front and back model
Comparison it is as shown in Figure 9.
Under model after shrinking, according to the theory of step 1, communication mode of the light in photonic crystal fiber can be acquired such as
Shown in attached drawing 10.
Meanwhile the mode electric field distribution of panda optic fibre formula can indicate as follows:
Wherein, ω=3.2um takes A=1,
It is η=0.9493 that coupling efficiency, which can be calculated, by formula (5).Therefore in this example, photonic crystal fiber and common
The splice loss, splice attenuation of solid core fibres are as follows:
Claims (8)
1. a kind of method for realizing photonic crystal fiber Yu solid core fibres low loss welding, which is characterized in that by establishing photon
Thermo parameters method model and airport stress model under crystal optical fibre and solid plain fiber fuse state, simulation difference two
Two sides fiber optic temperature situation of change and air hole wall stress condition in carbon oxide laser device discharge process, and then derive air
Hole collapses the numerical relation between degree and carbon dioxide laser discharge parameter, then by establishing photonic crystal fiber end face knot
The numerical relation of structure and its effective core area obtains the loss model of photonic crystal fiber Yu solid core fibres welding, Jin Erjing
Really calculate the carbon dioxide laser discharge parameter for realizing low loss welding.
2. the method according to claim 1 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In carbon dioxide laser discharge parameter includes discharge centers position, discharge time, discharge capacity.
3. the method according to claim 2 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In, the specific steps are as follows:
Step 1: establishing two optical fiber effective core areas and splice loss, splice attenuation model
The high birefringence characteristic of photonic crystal fiber is formed by the geometry of its two great circle of immediate vicinity, according to light
Electromagnetic theory calculates, when light is bound in fiber optic hub, the electric-field intensity distribution at electric-field intensity distribution photonic crystal fiber center
E1；The field distribution E2 in solid plain fiber core is calculated simultaneously；
When high birefringence type photonic crystal fiber and panda protecting polarized light fiber couple, emergence pattern is converted in abrupt interface, wherein
A part and the mode of waveguide match, and continuation is propagated in the waveguide；Another part and the mode of waveguide mismatch, and become spoke
It penetrates mould and loses, this portion of energy lost becomes coupling mismatch loss, calculates coupling by the pattern match of two waveguides
Efficiency, and then can establish the model of two optical fiber effective core areas and splice loss, splice attenuation；
Step 2: the analysis of photonic crystal fiber thermal conduction characteristic
The thermal conduction characteristic being heated to photonic crystal fiber is analyzed, and photon under different carbon dioxide laser discharge parameters is obtained
Crystal optical fibre thermo parameters method model；
Step 3: thermal conduction characteristic is analyzed when photonic crystal fiber and solid plain fused fiber splice
In conjunction with step 2 photonic crystal fiber thermo parameters method model, when carrying out photonic crystal fiber and solid plain fused fiber splice
Thermal conduction characteristic analysis, and then establish the thermo parameters method model of two optical fibers under different carbon dioxide laser discharge parameters；
Step 4: mechanical characteristic analysis when photonic crystal fiber and solid plain fused fiber splice
In conjunction with the two sides fiber optic temperature field distribution model under the different carbon dioxide laser discharge parameters of step 3, molten is established
The relationship and photonic crystal fiber flow equation of photonic crystal fiber viscosity coefficient and temperature under state, according in photonic crystal fiber
The flow process at gas-liquid two-phase interface is tracked its quartz-Air Interface using the Level Set Method in biphase gas and liquid flow,
Quartzy liquid surface equation of motion under surface tension is obtained, and then establishes photon under different carbon dioxide laser discharge parameters
Crystal optical fibre air micro pore structure；
Step 5: establishing the numerical model of carbon dioxide laser discharge parameter and splice loss, splice attenuation
In conjunction with photonic crystal fiber air micro pore structure and step 1 under the different carbon dioxide laser discharge parameters of step 4
Photonic crystal fiber and solid plain optical fiber effective core area and loss model, establish carbon dioxide laser discharge parameter with
The numerical relation of splice loss, splice attenuation；
Step 6: low loss welding parameter determines
In conjunction with the numerical model of step 5 carbon dioxide laser discharge parameter and splice loss, splice attenuation, minimum welding is damaged in order to obtain
Consumption, that is, need to realize the best match of two sides optical fiber mode fields, acquire photonic crystal fiber air pore structure under molten condition, in turn
Derive the carbon dioxide laser discharge parameter that above structure to be obtained needs: discharge capacity, discharge time, discharge centers position
It sets.
4. the method according to claim 3 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In when determining discharge time, discharge centers position delta can be obtained by formula (1)
Z=-419.6delta2-0.945delta+7.943×10-5 (7)
Wherein, Z is fiber end face axial coordinate.
5. the method according to claim 3 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In discharge capacity is in the case where determining discharge time, and by the position z=0, the relation curve of temperature and discharge time are determined.
6. the method according to claim 3 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In, in the case where determining discharge time, at the position z=0, the relation curve of temperature and discharge time, as the titanium dioxide as shown in formula (8)
Silicon viscosity coefficient μ is determined
Wherein, T is temperature relevant to discharge time.
7. the method according to claim 3 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In in the case where determining discharge time, silica viscosity coefficient is by the photonic crystal fiber airport that needs to realize under molten condition
Collapse degree determine.
8. the method according to claim 3 for realizing photonic crystal fiber and solid core fibres low loss welding, feature exist
In the degree influence that collapses of photonic crystal fiber airport collapses area, to influence fiber coupling, two optical fibers are on mutation circle
Optical coupling efficiency when face matches emergence pattern, it is determining by formula (5),
Wherein, E1(x, y) and E2(x, y) is respectively two mode distributions of two optical fibers in abrupt interface.
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| JP2001116949A (en) * | 1999-10-18 | 2001-04-27 | Sumitomo Electric Ind Ltd | Fusion splicing method for optical fiber |
| JP2004325863A (en) * | 2003-04-25 | 2004-11-18 | Furukawa Electric Co Ltd:The | Connection method of optical fiber and optical fiber having connection part |
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