A kind of twin-core polarization-maintaining photonic crystal fiber
Technical field
The present invention relates to the design and production field of photonic crystal fiber, is specifically a kind of twin-core polarization-maintaining photonic crystal light
It is fine.
Background technology
The application of angle/motion-sensing is increasingly extensive, such as mobile phone, unmanned aerial vehicle widely apply gyro as a sensor to
Realize positioning and control.And a kind of angular transducer that optical fibre gyro is applied as inertial navigation system, usage amount rise year by year.Tradition
Optical fibre gyro use panda protecting polarized light fiber or bow-tie type polarization maintaining optical fibre more.These sensors have been successfully applied in winged at present
The fields such as machine, automobile, ship.But with application to optical fiber gyroscope precision requirement and volume small form factor requirements, optical fibre gyro
One extremely urgent difficulty is that the performance of polarization-maintaining fiber coil is increasingly difficult in adapt to this requirement.
Photonic crystal fiber has extensively by studying for many years in fields such as information transmission, temperature sensing and spectroscopy
General application.The structure design of photonic crystal fiber is also varied.
Chinese patent (Application No. 201110029982.3)《A kind of double waveguide parallel polarization maintaining fiber and its manufacturer
Method》A kind of method that polarization maintaining optical fibre is manufactured by the way of two fibers/waveguides arranged side by side is described, this method is to use two simultaneously
Row prefabricated rods wire drawing or wire drawing at the same time in two fiber drawing furnaces in a fiber drawing furnace, by two optical fiber and one is listed in coating
The method risen.Its optical fiber structure is as shown in Figure 1, structure includes two fibre cores 1 and respective covering 2, stressed zone 3 and internal coating
4th, external coating 5.The design uses two panda optic fibres.There are the problem of be not account for increasing sensing under the same volume
The problem of device light path and the coupling demand of double-core photonic crystal fiber.
The content of the invention
The present invention designs from optical fiber gyroscope precision requirement and volume small form factor requirements and has manufactured a kind of twin-core polarization-maintaining
The length of Fibre Optical Sensor is doubled by photonic crystal fiber, the optical fiber in same volume.
The present invention proposes this twin-core polarization-maintaining photonic crystal fiber, in the radial direction two dimension for the quartz substrate that outside diameter is 125um
Be disposed with the medium holes of periodic arrangement on direction, the medium holes form hexagon medium hole array, each medium holes it is straight
Footpath is d1;The spacing Λ of medium holes is 5.23~5.83um, lacked in the medium hole array two non-conterminous medium holes from
And two fibre cores are formed, the spacing of two fibre cores is 30~35um, has the diameter of two medium holes in each fiber core
D2, and d2 > d1 are changed to, so as to form four big medium holes.
The medium holes are airport, and the number of plies of the medium holes for being looped around fiber core is 6~7 layers.
The scope of the d1 is 2.5~3.0um, and the scope of the d2 is 6.5~8.5um.
One end of the double-core photonic crystal fiber is single curved waveguide, and the both ends of the curved waveguide are arranged in parallel,
Its radial spacing is 30~35um, is coupled respectively with two fibre cores.
One end of the double-core photonic crystal fiber is Y waveguide, the radial spacing of the two-arm of the Y waveguide for 30~
35um, couples with two fibre cores respectively.
One end of the double-core photonic crystal fiber is twin-core coupler, and the twin-core coupler includes two single light
Fibre, one end of two single-core fibers are arranged in parallel, its side all rubbing down, diameter reduction cause the fibre core spacing of two single-core fibers
For 30~35um, coupled respectively with two fibre cores of double-core photonic crystal fiber;The other end of two single-core fibers is free end.
The far field mode spot of described two fibre cores is ellipse, including major axis and short axle, and the length of major axis and short axle ratio is
1.2:1~1.7:1.
The major axis of described two far field mode spots is parallel with short axle difference, and one of two major axis and two short axles are one
On bar straight line.
Described four big medium holes are point-blank.
The major axis of described two far field mode spots is parallel with short axle difference, and two major axis are not point-blank, two short
Axis is also not point-blank.
The present invention is compared with the prior art possessed beneficial effect:Currently invention addresses optical fiber gyroscope precision requirement and
Volume small form factor requirements, design and have manufactured a kind of twin-core polarization-maintaining photonic crystal fiber, the optical fiber is in same volume by light
The length of fibre sensing is doubled, and is able to ensure that polarization-maintaining performance and overcomes cross-interference issue.This optical fiber and its apply in light
Fine gyro field still belongs to the first time.
Brief description of the drawings
Fig. 1 is the structure chart of the prior art;
Fig. 2 is the cross section topological diagram of embodiment 1;
Fig. 3 is the far field mode spot schematic diagram of embodiment 1;
Fig. 4 is crosstalk and fibre core spaced relationship curve map;
Fig. 5 is crosstalk and length relation curve map;
Fig. 6 is the Y waveguide coupling schematic diagram of embodiment 1;
Fig. 7 is the twin-core coupler structure schematic diagram of embodiment 1;
Fig. 8 is the cross section topological diagram of embodiment 2;
Fig. 9 is the twin-core coupler structure schematic diagram of embodiment 2;
Figure 10 is the cross section topological diagram of embodiment 3;
Figure 11 is the twin-core coupler structure schematic diagram of embodiment 3;
Embodiment
The polarization maintaining optical fibre that tradition is applied to optical fibre gyro is all an only fuse, its cladding outer diameter is 80um or 125um.
Under such design, the volume that each of which fuse takes is larger, and it is unfavorable to be minimized for optical fibre gyro.The light that the present invention designs
Fibre is that two fuses of placement, the volume that so each fuse occupies have been reduced to the circle of 62.5um diameters in the covering of 125um
Within cylinder.Or say under the same product around ring body, this fiber design allows longer light path, can improve optical fibre gyro
Precision.
Embodiment 1
Symmetrical twin-core polarization-maintaining photonic crystal fiber cross section topological diagram as shown in Figure 2, in the radial direction of quartz substrate
The airport of periodic arrangement is disposed with two-dimensional directional, airport forms regular hexagon medium hole array, each medium holes
The scope of diameter d1 is 2.5~3.0um.The spacing Λ of medium holes is 5.23~5.83um.The X-direction in figure, medium holes battle array
Two medium holes are lacked in row so as to form two fibre cores, the spacing of two fibre cores is 6 Λ, in the range of 31.4~35um.
D2 is changed in the diameter of two medium holes of each fibre core horizontal direction (i.e. X-direction) left and right, the diameter range of d2 is 6.5~
8.5um, so as to form four big medium holes.The most numbers of plies for being looped around the medium holes of single fiber core are 6 layers.
As shown in figure 3, two polarization-maintaining fibre cores are non-circular symmetric structures, the similar ellipse of its far field mode spot, there are one
Major axis and a short axle, and the length of major axis and short axle ratio is 1.2:1~1.7:1.
The center line of the center line and silica clad of the fiber core and air cladding layer is completely overlapped, as shown in Figure 2.It is this
Two major axis and short axle of optical fiber are all parallel constructions, specifically the two of this root optical fiber short axle in terms of Y-axis in straight line
On.Two major axis of this root optical fiber, 6 ∧ of deviation from X-axis.
For any one twin-core fiber, this optical fiber is used, it is necessary to consider cross-interference issue.Crosstalk refers to from one
The signal of a fibre core transmission has traveled to another fibre core.Crosstalk between the communications field, fuse can cause communications errors
The increase of rate, causes communication disruption when serious.For sensing, crosstalk is abnormal by the detection limit for causing test side, sensor
Correct sensing amount cannot be exported, causes faulty sensor.Simulation calculates fibre core spacing to cross talk effects in the present embodiment.Such as
Crosstalk and the curve map of fibre core spaced relationship shown in Fig. 4 see that crosstalk is less than -30dB when spacing is more than 27um.At the same time
In terms of another angle, crosstalk is increased with the increase of propagation distance, therefore simulation calculates transmission range from 100m
To influence of the distance to crosstalk of 3000m, as shown in Figure 5, it was confirmed that crosstalk is because distance increases 30 times from 100 meters, crosstalk increase
About 2dB.Accordingly, it is considered to arrive practical application reason, the scope by the line space design of twin-core into 30~35um, can be effectively ensured
The crosstalk of twin-core fiber does not influence the practical application of optical fiber.
In addition, the polarization holding capacity of twin-core polarization maintaining optical fibre is to determine another aspect of fiber optic applications, for this reason, this hair
The bright optical fiber for devising hole diameter size d1, air pitch of holes ∧ and diameter macropores size d2, ensures each of twin-core fiber
The cross-talk of a fuse is not more than the level of -30dB.The overall diameter of optical fiber is remained into 80~125um, the wherein model of d1 in design
It is 2.5-3um to enclose, and ∧ is 5.23-5.83um, and d2 is 6.5-8.5um, under such design, the major axis of the mould spot of fibre core:Short axle
The ratio between be not more than the level of -30dB in the cross-talks of 1.2~1.7 each fuse that can ensure twin-core fiber in the range of this,
Meet the requirement of application.
One end of above-mentioned optical fiber can be coupled by following three kinds of modes.
(1) one end face of curved waveguide uncoupling made of a lithium columbate crystal.The both ends of curved waveguide are parallel
Set, it is ensured that the radial spacing at its both ends is within 30~35um;Light from one end face of twin-core polarization-maintaining photonic crystal fiber its
In the injection of fuse, another end face is transferred to, due to the end face of two fibre core spacing and curved waveguide distance and polarization
Just the same, the light so coupled will be looped back in another fibre core of another end face and transmit.Laser is finally from entering afterwards
Another fuse of mouth end face projects.
(2) as shown in fig. 6, the 20 uncoupling low crosstalk twin-core polarization-maintaining photon of Y waveguide made of a lithium columbate crystal
Crystal optical fibre 21, the two-arm spacing of Y waveguide 20 is within 30-35um.In practical application, two fiber cores 22 will be directly right
The two-arm of Y waveguide should be coupled into, since the spacing range of two fuses of optical fiber is 30~35um, the Y waveguide of corresponding design
Radially spacing is also 30~35um to two-arm.The major and minor axis design of the two-arm of Y waveguide 20 is consistent with optical fiber 21, and according to major axis
The mode of major axis is aligned.
(3) the twin-core coupler uncoupling twin-core polarization-maintaining photonic crystal fiber made of two polarization maintaining optical fibre side rubbing downs
Two fibre cores.As shown in fig. 7, the panda protecting polarized light fiber fibre core spacing of two covering reductions is 30~35um.In this way, two fibres
Core is coupled into two fuses of fixing end of twin-core coupler by directly corresponding to, and major and minor axis design is consistent with optical fiber, and according to length
Axis is directed at the mode of major axis (major axis is upper and lower vertical direction, and spaced and parallel, and short axle is point-blank).Throw side
The other end for grinding the twin-core coupler of work is two independent polarization maintaining optical fibre free ends.(Fig. 7 cathetus is long axis direction)
Twin-core coupler can certainly be produced using bow-tie type polarization maintaining optical fibre side rubbing down.
Embodiment 2
Twin-core polarization-maintaining photonic crystal fiber cross section topological diagram as shown in Figure 8, its difference from Example 1 are
Mainly, its fibre core and covering all non-centrosymmetry:The center line of fiber core and air cladding layer in Fig. 8 (sit by the Y-direction i.e. in figure
Parameter) (center line is whole cross section by the center of the 6th airport of left number with the vertical center line of silica clad
Center line) there are half ∧ (∧ represent be the adjacent airport of any two center spacing) offset.The reason for offset, exists
In left side airport covering than 1 few one layer of embodiment.
In addition, fibre core is all disposed within Y-axis.In this way, two major axis in terms of X-axis point-blank, and two major axis
6 ∧ of deviation in terms of Y-axis.
Needed in view of observing axis, X-axis or Y-axis can also place symmetrical two mark points in optical fiber silica clad
(not shown), can be observed and be recognized with side so when carrying out optical fiber and device or optical fiber and optical fiber operates axis.
In coupling, three kinds of coupled modes in embodiment 1 can be used, are simply aligned in the long and short axis of far field mode spot
On adjust accordingly.Such as using mode in the 3rd, i.e., using twin-core coupler uncoupling when, two single polarization maintaining optical fibres
Structure is as shown in figure 9, point-blank, (Fig. 9 cathetus is major axis side to 6 ∧ of short axle parallel interval to major axis after the rubbing down of side
To).
Embodiment 3
Twin-core polarization-maintaining photonic crystal fiber cross section topological diagram as shown in Figure 10, its difference from Example 1 exist
In main, its fibre core is that X-axis and Y-axis are all asymmetrical.In Figure 10, the center line of air cladding layer and the center line of silica clad are complete
It is complete consistent, but the offset of the center line of two fibre cores and the center line of silica clad in Y-axis there are half of ∧, and be located at respectively
The arranged on left and right sides of silica clad Y-axis center line.A ∧ is spaced between two fibre cores in the X-axis, 6 are spaced in Y-direction
A ∧.Its far field mode spot is also similar ellipse, and there are a major axis and a short axle, and two major axis are all parallel with short axle
Structure, but two major axis 1 ∧ of deviation in terms of X-axis, 6 ∧ of deviation in terms of Y-axis.The fibre core and covering of this optical fiber are all rotations
Turn symmetrical.In the topological structure of the optical fiber, two fibre cores shift to install, it, which suppresses the performance of crosstalk, is also more improved.
With embodiment 2, it is contemplated that axis, which is observed, to be needed, and X-axis or Y-axis can also be placed symmetrically in optical fiber silica clad
Two mark point (not shown)s, can so be observed when carrying out optical fiber and device or optical fiber and optical fiber operates axis with side
And identification.
In coupling, three kinds of coupled modes in embodiment 1 can be used, are simply aligned in the long and short axis of far field mode spot
And adjusted accordingly in spacing.Such as using mode in the 3rd, i.e., using twin-core coupler uncoupling when, two single polarization-maintainings
The structure of optical fiber is as shown in figure 11, and long 1 ∧ of axis deviation after the rubbing down of side, (Figure 11 cathetus is major axis side to 6 ∧ of short axle deviation
To).
Above content is to combine specific embodiment further description made for the present invention, it is impossible to assert this hair
Bright specific implementation is confined to these explanations.