CN108873157B - Low-magnetic-sensitivity polarization-maintaining photonic crystal fiber - Google Patents
Low-magnetic-sensitivity polarization-maintaining photonic crystal fiber Download PDFInfo
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- 239000000835 fiber Substances 0.000 title claims abstract description 128
- 239000004038 photonic crystal Substances 0.000 title claims abstract description 39
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 41
- 238000005253 cladding Methods 0.000 claims abstract description 39
- 239000010453 quartz Substances 0.000 claims abstract description 28
- 230000035945 sensitivity Effects 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 7
- 230000010287 polarization Effects 0.000 claims description 31
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
- 229910052710 silicon Inorganic materials 0.000 claims description 8
- 239000010703 silicon Substances 0.000 claims description 8
- 239000011248 coating agent Substances 0.000 claims description 7
- 238000000576 coating method Methods 0.000 claims description 7
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 claims 1
- 239000013307 optical fiber Substances 0.000 abstract description 46
- 239000010432 diamond Substances 0.000 abstract description 4
- 229910003460 diamond Inorganic materials 0.000 abstract description 4
- 238000012681 fiber drawing Methods 0.000 abstract description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 24
- 230000000694 effects Effects 0.000 description 9
- 238000005452 bending Methods 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 229910052732 germanium Inorganic materials 0.000 description 5
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 238000004891 communication Methods 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- 230000005540 biological transmission Effects 0.000 description 1
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- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/023—Microstructured optical fibre having different index layers arranged around the core for guiding light by reflection, i.e. 1D crystal, e.g. omniguide
- G02B6/02304—Core having lower refractive index than cladding, e.g. air filled, hollow core
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
- G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
- G02B6/02328—Hollow or gas filled core
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/024—Optical fibres with cladding with or without a coating with polarisation maintaining properties
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Abstract
The invention discloses a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber, which relates to the technical field of new materials and comprises a fiber core, and an air hole region and a quartz cladding which are sequentially coated on the fiber core from inside to outside, wherein the air hole region comprises 4 first air holes and a plurality of second air holes, the inner diameter of each first air hole is larger than that of each second air hole, and the 4 first air holes are uniformly arranged on the periphery of the fiber core and distributed in a diamond shape. The air hole region comprises a first air hole ring and a second air hole ring surrounding the periphery of the first air hole ring, wherein the first air hole ring comprises 2 first air holes, and the second air hole ring comprises 2 first air holes. The invention can effectively reduce the internal torsion during the optical fiber drawing, and achieve the purpose of reducing the magnetic sensitivity.
Description
Technical Field
The invention relates to the technical field of new materials, in particular to a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber.
Background
In an ideal round core single mode fiber, there is no circular birefringence, so the faraday phase error between two counter-propagating light waves in the fiber coil is zero, but this is only true in the ideal state of the fiber ring, i.e. when the polarization state of the light in the fiber ring does not change. The magneto-optical Faraday effect is that when linearly polarized light passes through a transparent medium under the action of a magnetic field, the polarization angle of the linearly polarized light rotates to generate an optical rotation phenomenon under the action of the magnetic field, and due to the magneto-optical Faraday effect, the phase of left and right circularly polarized light forming incident linearly polarized light is changed by the magnetic field in a single-mode optical fiber, so that an included angle is generated between polarization surfaces of the two linearly polarized light which are reversely propagated, a nonreciprocal phase difference is generated when the light is transmitted in an optical fiber ring, and the error cannot be distinguished from the Sagnac effect (Sagnac effect) of the optical fiber gyroscope, so that a Faraday effect error is generated, and the optical fiber gyroscope has magnetic sensitivity.
For a single-mode fiber optic gyroscope, residual stress generated in the process of manufacturing a single-mode fiber preform can bring torsion to a certain degree, and further circular birefringence is introduced. When the fiber is wound on the framework, the misalignment of the fiber winding machine and the gyroscope framework axis is almost inevitable, which can generate further torsion, and the circular birefringence caused by the torsion is a root cause of the radial magnetic sensitivity error of the fiber optic gyroscope.
In the polarization maintaining fiber-optic gyroscope, because the polarization maintaining fiber has high birefringence and can well maintain the original polarization state of light in the transmission of the fiber ring, the radial magnetic sensitivity error of the fiber-optic gyroscope can be reduced by using the polarization maintaining fiber. However, the preform of polarization maintaining optical fiber is subjected to high stress to form a helical stress bar, so that the main axis direction of the high birefringence polarization maintaining optical fiber rotates slowly during the drawing process. Because the birefringence axis of the optical fiber is twisted, the polarization state of light in the optical fiber is changed, and the Faraday effect in the polarization-preserving optical fiber is not completely zero. In addition, when the polarization maintaining fiber is wound, the principal axis of the fiber rotates to some extent, which also causes the intrinsic polarization mode of light to be no longer a standard linear polarization state, so that the magnetic sensitivity error of the fiber optic gyroscope cannot be zero. In an axial magnetic field environment, in the faraday effect, a magnetic field vertical component perpendicular to a light propagation direction does not form the faraday effect, but a certain bending exists after an optical fiber ring is wound, the magnetic field vertical component can enable a mode parallel to a bending plane in a bent optical fiber to have nonreciprocity, so that a phase error is generated, torsion is inevitably introduced in the processes of drawing the optical fiber and winding the optical fiber ring, the torsion can cause the component of the mode parallel to the bending plane to change, so that an axial magnetic sensitivity error of an optical fiber gyroscope is caused, and the conventional stress type polarization maintaining optical fiber has a pressure area, so that internal torsion is inevitable due to the existence of the stress area when the optical fiber is drawn.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide the low-magnetic-sensitivity polarization-maintaining photonic crystal fiber which can effectively reduce the internal torsion during fiber drawing and achieve the purpose of reducing the magnetic sensitivity.
In order to achieve the purpose, the invention adopts the technical scheme that the fiber core comprises a fiber core, and an air hole area and a quartz cladding which are sequentially coated on the fiber core from inside to outside, wherein the air hole area comprises 4 first air holes and a plurality of second air holes, the inner diameter of each first air hole is larger than that of each second air hole, and the 4 first air holes are uniformly arranged on the periphery of the fiber core and distributed in a diamond shape.
On the basis of the technical scheme, the air hole area comprises a first air hole ring and a second air hole ring surrounding the periphery of the first air hole ring, the first air hole ring comprises 2 first air holes, the second air hole ring comprises 2 first air holes, and a connecting line between the 2 first air holes in the first air hole ring is perpendicular to a connecting line between the 2 first air holes in the second air hole ring.
On the basis of the technical scheme, the first air hole ring comprises 4 second air holes, the 4 second air holes in the first air hole ring are symmetrically arranged on the periphery of the fiber core, the second air hole ring comprises 10 second air holes, and the 10 second air holes in the second air hole ring are symmetrically arranged on the periphery of the fiber core.
On the basis of the technical scheme, the filling materials between the first air hole and the second air hole and between the second air hole and the second air hole are quartz glass.
On the basis of the technical scheme, the radius of the fiber core is 5 um-7 um, the inner diameter of the first air hole is 6.0 um-11 um, and the inner diameter of the second air hole is 3-5 um.
On the basis of the technical scheme, the radius of the fiber core is 6um, the inner diameter of the first air hole is 7um, and the inner diameter of the second air hole is 3.5 um.
On the basis of the technical scheme, the diameter of the quartz cladding is 80-100 um.
On the basis of the technical scheme, a coating is also arranged outside the quartz cladding.
On the basis of the technical scheme, the diameter of the coating is 100-135 um.
On the basis of the technical scheme, the fiber core is a pure silicon lithium-doped fiber core, and the quartz cladding is a fluorine-doped quartz cladding.
Compared with the prior art, the invention has the advantages that: the design of 4 symmetrical large-diameter air holes is adopted, and the arrangement modes of the air holes with different sizes are adopted, so that the size of the air holes is optimized, the internal torsion during the drawing of the optical fiber is effectively reduced, the purpose of reducing the magnetic sensitivity is achieved, and the use requirement of the optical fiber gyroscope is effectively met.
Drawings
FIG. 1 is a schematic structural diagram of a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber according to the present invention.
In the figure: 1-fiber core, 2-air hole region, 3-quartz cladding, 4-first air hole, 5-second air hole, 6-first air hole ring and 7-second air hole ring.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Example 1
Referring to fig. 1, the embodiment of the invention provides a low magnetic sensitivity polarization-maintaining photonic crystal fiber, which is applied to a miniaturized high-precision fiber optic gyroscope, and not only has good birefringence, excellent radiation resistance and super strong bending insensitivity of a conventional polarization-maintaining photonic crystal fiber, but also has low magnetic sensitivity, and can effectively reduce the influence of a magnetic field on the precision of the fiber optic gyroscope. The low-magnetic-sensitivity polarization-maintaining photonic crystal fiber comprises a fiber core 1, and an air hole region 2 and a quartz cladding 3 which are sequentially coated on the fiber core 1 from inside to outside, namely the polarization-maintaining photonic crystal fiber of the invention sequentially comprises the fiber core 1, the air hole region 2 and the quartz cladding 3 from inside to outside, wherein the air hole region 2 consists of a plurality of air holes, specifically, the air hole region 2 comprises 4 first air holes 4 and a plurality of second air holes 5, and the air hole region 2 comprises 4 first air holes 4 and a plurality of second air holes 5. The second air holes 5 are arranged between the first air holes 4, the inner diameter of each first air hole 4 is larger than that of each second air hole 5, and the 4 first air holes 4 are uniformly arranged on the periphery of the fiber core 1 and distributed in a diamond shape, namely, the connecting line among the 4 first air holes 4 is in a diamond shape.
For the photonic crystal fiber, the birefringent photonic crystal fiber adopts a refractive index guide type waveguide structure design, the light guiding mechanism of the birefringent photonic crystal fiber is consistent with that of the conventional polarization maintaining fiber, and the light guiding mechanism is a total reflection principle, which requires that the refractive index of the fiber core 1 is higher than that of the cladding. The refractive index guide type implementation mode of the conventional polarization maintaining fiber is that the fiber core 1 adopts germanium to raise the refractive index of the fiber core 1, and the cladding is pure quartz, so that the refractive index of the fiber core 1 is higher than that of the cladding. For the photonic crystal fiber, a plurality of circles of air holes are distributed in a cladding of the photonic crystal fiber, and the air holes can reduce the overall refractive index of the region where the air holes are located, so that the effective refractive index of the cladding is reduced, the effect that the refractive index of a fiber core 1 is larger than that of the cladding can be realized even if the fiber core 1 is doped with little germanium or even not doped with germanium, and the optical signal is transmitted by total reflection.
The birefringence of the conventional polarization maintaining fiber is mainly realized by stress birefringence, that is, two stress regions are symmetrically distributed around the fiber core 1, and the two stress regions generate large stress, so that the states of two polarization modes of fundamental mode light transmitted in the fiber core 1 are influenced, and the birefringence is realized. The birefringent photonic crystal fiber needs to symmetrically introduce two air holes with different sizes from the surrounding air holes into the air holes around the fiber core 1, and the sizes of the two air holes are larger than those of other surrounding air holes, so that the effective refractive index of the cladding is sufficiently reduced in the region where the two air holes are located, the mode field transmitted by the fiber core 1 in the line direction of the two air holes is compressed, the mode field transmitted by the fiber core 1 is an elliptical mode field, and the birefringence is realized. In the optical fiber gyroscope, because a certain bending exists after the optical fiber ring is wound, the vertical component of a magnetic field can lead the mode parallel to a bending plane in the bent optical fiber to have nonreciprocity, thereby generating phase error, torsion is inevitably introduced in the processes of drawing the optical fiber and winding the optical fiber ring, and the torsion can cause the component parallel to the bending plane to change, therefore, the axial magnetic sensitivity error of the optical fiber gyroscope is related to the torsion of the optical fiber in the optical fiber ring, the root of reducing the magnetic sensitivity error of the optical fiber gyroscope is to reduce the internal torsion of the polarization maintaining optical fiber, the conventional polarization maintaining photonic crystal optical fiber can not perfectly ensure that the sizes of two large-diameter air holes are the same when the two large-diameter air holes are drawn, and the internal torsion is inevitably generated to cause the increase of the secondary sensitivity of the optical fiber, the invention adopts the design of 4 symmetrical large-diameter air holes, and optimizes the sizes of, effectively reduces the internal torsion of the optical fiber during drawing and achieves the purpose of reducing the magnetic sensitivity.
Example 2
Referring to fig. 1, in an embodiment of the present invention, a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber is provided, in which based on embodiment 1, an air hole region 2 includes a first air hole loop 6 and a second air hole loop 7 surrounding a periphery of the first air hole loop 6, the first air hole loop 6 includes 2 first air holes 4, the second air hole loop 7 includes 2 first air holes 4, and a connection line between the 2 first air holes 4 in the first air hole loop 6 is perpendicular to a connection line between the 2 first air holes 4 in the second air hole loop 7. The first air hole ring 6 comprises 4 second air holes 5, the 4 second air holes 5 in the first air hole ring 6 are symmetrically arranged on the periphery of the fiber core 1, the second air hole ring 7 comprises 10 second air holes 5, and the 10 second air holes 5 in the second air hole ring 7 are symmetrically arranged on the periphery of the fiber core 1, so that the arrangement mode of the air holes with different sizes of the photonic crystal fiber with the geometric birefringence characteristic is met.
Example 3
Referring to fig. 1, in an embodiment of the present invention, based on embodiment 2, an air hole region 2 includes a first air hole loop 6 and a second air hole loop 7 surrounding a periphery of the first air hole loop 6, the first air hole loop 6 includes 2 first air holes 4, the second air hole loop 7 includes 2 first air holes 4, and a connection line between the 2 first air holes 4 in the first air hole loop 6 is perpendicular to a connection line between the 2 first air holes 4 in the second air hole loop 7. The first air hole ring 6 comprises 4 second air holes 5, the 4 second air holes 5 in the first air hole ring 6 are symmetrically arranged on the periphery of the fiber core 1, the second air hole ring 7 comprises 10 second air holes 5, and the 10 second air holes 5 in the second air hole ring 7 are symmetrically arranged on the periphery of the fiber core 1. The filling material between the first air hole 4 and the second air hole 5 and between the second air hole 5 and the second air hole 5 is quartz glass.
Example 4
The embodiment of the invention provides a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber. For birefringent photonic crystal fibers, the mechanism for achieving the most important birefringence characteristics is completely different from that of conventional polarization maintaining fibers. The birefringence of the conventional polarization maintaining fiber is mainly realized by stress birefringence, that is, two stress regions are symmetrically distributed around the fiber core 1, and the two stress regions generate large stress, so that the states of two polarization modes of fundamental mode light transmitted in the fiber core 1 are influenced, and the birefringence is realized. The birefringent photonic crystal fiber needs to symmetrically introduce two air holes with different sizes from the surrounding air holes into the air holes around the fiber core 1, the sizes of the two air holes are larger than those of the other surrounding air holes, so that the effective refractive index of the cladding is sufficiently reduced in the area where the two air holes are located, the mode field transmitted by the fiber core 1 in the direction of the line connecting the two air holes is compressed, the mode field transmitted by the fiber core 1 is an elliptical mode field, and accordingly birefringence is achieved. Since different birefringent photonic crystal fibers are possible only if the size of the air holes is different, and if the number of air hole loops around the core 1 is combined, there will be more birefringent photonic crystal fiber designs, and therefore the size of the structures inside the fiber will have a critical impact on the performance of the fiber.
In this embodiment, the radius of the fiber core 1 is 5um to 7um, the inner diameter of the first air hole 4 is 6.0um to 11um, and the inner diameter of the second air hole 5 is 3 um to 5um based on embodiment 3. The diameter of the quartz cladding 3 is 80 um-100 um. The quartz cladding 3 is also provided with a coating for protecting the optical fiber, and the diameter of the coating is 100 um-135 um. In particular, the quartz cladding 3 may be a recessed inner cladding structure.
Example 5
The embodiment of the invention provides a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber, and on the basis of embodiment 4, a calculation method of a relative refractive index difference is described by combining with fig. 1, wherein a relative refractive index calculation formula is as follows:
Δ＝(n1-n2)/(n1+n2)*100％
wherein n2 is the refractive index of the fiber core 1, n1 is the refractive index of the quartz cladding 3, the relative refractive index difference △ n21 between the quartz cladding 3 and the fiber core 1 is in the range of-0.33 to-0.05%, the refractive index of the quartz glass filled between the air holes is the same as that of the quartz cladding 3, the radius of the fiber core 1 is 5um to 7um, the inner diameter of the first air hole 4 is 6.0um to 11um, the inner diameter of the second air hole 5 is 3 to 5 um., the air pressure of the first air hole 4 is p1, and the air pressure of the second air hole 5 is p2 in the optical fiber drawing process.
The implementation of the different sized fibers in 5 was performed at different gas pressures p1 and p2, and the specific dimensional parameters and implementation results are shown in table 1.
TABLE 1
| Optical fiber 1 | |
|
|
|
|
| △n21 | －0.33％ | －0.25％ | －0.2％ | －0.50％ | －0.05％ |
| |
7 | 8.2 | 8.9 | 9.3 | 10.5 |
| |
3.5 | 4.0 | 4.3 | 4.7 | 5.0 |
| Core 1 radius um | 6 | 6.1 | 6.3 | 5.8 | 5.9 |
| P1-P2kp | 0.5 | 1.1 | 1.5 | 1.7 | 2 |
| |
80 | 85 | 90 | 95 | 100 |
| Coating diameter um | 100 | 100 | 120 | 135 | 135 |
| 1550nm attenuation dB/km | 0.3 | 0.35 | 0.37 | 0.5 | 0.6 |
| 1550nm beat length mm | 0.5 | 1.12 | 1.7 | 0.4 | 0.4 |
| 1550n crosstalk dB/km | －20 | －21 | －18 | －25 | －30 |
As can be seen from Table 1, as the inner diameter of the first air hole 4, the inner diameter of the second air hole 5, the radius of the fiber core 1 and the diameter of the quartz cladding 3 increase, the 1550nm attenuation, the 1550nm beat length and the 1550n crosstalk become larger and larger for the overall performance of the birefringent polarization-maintaining photonic fiber of the present invention. Thus, for the optimum size, the radius of the core 1 is 6um, the inner diameter of the first air holes 4 is 7um, and the inner diameter of the second air holes 5 is 3.5 um.
Therefore, for the low magnetic sensitivity polarization-maintaining photonic crystal fiber with the optimal size, 1550nm attenuation can be controlled to be within 1dB/km, the optimal value can be within 0.3dB/km, crosstalk at 1550nm can reach-30 ddB/km, when the bending radius reaches 2mm, the crosstalk of the fiber at 1550nm can still reach-25 ddB/km, additional attenuation is less than 0.3dB, the low magnetic sensitivity polarization-maintaining photonic crystal fiber has excellent full-temperature performance, and the 1550nm full-temperature crosstalk variation is less than 0.5dB within the range of-45-85 ℃. The optical fiber has excellent low magnetic sensitivity, and the sub-sensitivity is one time better than that of the common polarization-maintaining photonic crystal fiber under the same magnetic flux.
Example 6
The embodiment of the invention provides a low-magnetic-sensitivity polarization-maintaining photonic crystal fiber, and on the basis of the embodiment 3, a fiber core 1 is a pure silicon lithium-doped fiber core 1, and a quartz cladding 3 is a fluorine-doped quartz cladding 3.
The pure silicon of the conventional low-attenuation photonic crystal fiber core 1 is protected by adding a fluorine-doped cladding, but the viscosity difference between a pure silicon region and the fluorine-doped cladding is larger when the fiber is drawn, so that larger stress exists, the fiber attenuation is increased, and the scattering loss of the ultra-low loss fiber is reduced, so that the pure silicon dioxide fiber core 1 is adopted. In order to form a total reflection waveguide structure, it is necessary to deposit a low refractive index material, usually doped with fluorine, around the pure silica core 1 to form a cladding, but the viscosities of the two materials are different at high temperature, the viscosity of the doped silica is about 1/3 of undoped silica, and the mismatch of the viscosities causes additional loss of the optical fiber due to stress, so that an element which does not change the refractive index and simultaneously reduces the viscosity of silica and does not have an absorption peak in a communication band itself needs to be added to the core region. According to the invention, the lithium ion doping is adopted, so that the viscosity of the optical fiber core 1 region is effectively reduced, the lithium element is proved to be capable of more effectively reducing the softening point of quartz than sodium element and potassium element, the ion size of the lithium element is far smaller than the communication wavelength of the optical fiber, and the absorption spectrum is not in the communication wavelength, so that the lithium element is very suitable for manufacturing the ultra-low loss optical fiber, the viscosity of the optical fiber core 1 region can be controlled by adjusting the ion concentration of the core region, the lithium element can be subjected to viscosity matching with the fluorine-doped cladding layer, and the loss caused by the mismatching of the stress of.
The theoretical calculation formula of the viscosity is as follows:
η＝6.1-ηF·ΔF-ηGe·ΔG
where 6.1 is the viscosity of pure silica, η F is the viscosity coefficient of influence of fluorine doping, η Ge is the viscosity coefficient of influence of germanium doping, Δ F is the contribution of fluorine doping to the refractive index, Δ Ge is the contribution of germanium doping to the refractive index, generally η F is 1.5, η Ge is 0.5, so the theoretical formula for viscosity calculation is simplified to η ═ 6.1-1.5 · Δ F-0.5 · Δ Ge.
In general, if the viscosity difference of adjacent interfaces is less than 0.1, the viscosity of the interfaces is matched, and the stress of the interfaces is small; if the difference between the viscosities of adjacent interfaces is larger than 0.1, the viscosities of the interfaces are not matched, and the interface stress is larger. The viscosity value of the pure silicon fiber core 1 is 6.1, the viscosity value of the fluorine-doped quartz cladding 3 is 5.6, the pure silicon fiber core 1 and the fluorine-doped quartz cladding are obviously not matched, and the interface stress is larger, so that lithium element is doped into the pure silicon fiber core 1, the viscosity value of the fiber core 1 area is reduced, the interface viscosity is matched to reduce the interface stress, the purpose of reducing attenuation is realized, and the loss of the optical fiber is reduced.
The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.
Claims (9)
1. A low magnetic sensitivity polarization-maintaining photonic crystal fiber, characterized in that: the core comprises a fiber core (1), and an air hole region (2) and a quartz cladding (3) which are sequentially coated on the fiber core (1) from inside to outside, wherein the air hole region (2) comprises 4 first air holes (4) and a plurality of second air holes (5), the inner diameter of each first air hole (4) is larger than that of each second air hole (5), and the 4 first air holes (4) are uniformly arranged on the periphery of the fiber core (1) and distributed in a rhombic shape;
the air hole area (2) comprises a first air hole ring (6) and a second air hole ring (7) surrounding the periphery of the first air hole ring (6), the first air hole ring (6) comprises 2 first air holes (4), the second air hole ring (7) comprises 2 first air holes (4), and the connecting line of the 2 first air holes (4) in the first air hole ring (6) is vertical to the connecting line of the 2 first air holes (4) in the second air hole ring (7);
the internal diameter of first air hole (4) is 7um, the internal diameter of second air hole (5) is 3.5 um.
2. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: the fiber core is characterized in that the first air hole ring (6) comprises 4 second air holes (5), the 4 second air holes (5) in the first air hole ring (6) are symmetrically arranged on the periphery of the fiber core (1), the second air hole ring (7) comprises 10 second air holes (5), and the 10 second air holes (5) in the second air hole ring (7) are symmetrically arranged on the periphery of the fiber core (1).
3. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: and the filling materials between the first air hole (4) and the second air hole (5) and between the second air hole (5) and the second air hole (5) are quartz glass.
4. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: the radius of the fiber core (1) is 5 um-7 um.
5. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 4, wherein: the radius of the fiber core (1) is 6 um.
6. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: the diameter of the quartz cladding (3) is 80 um-100 um.
7. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: and a coating is also arranged outside the quartz cladding (3).
8. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 7, wherein: the diameter of the coating is 100 um-135 um.
9. The low magnetic sensitivity polarization maintaining photonic crystal fiber of claim 1, wherein: the fiber core (1) is a pure silicon lithium-doped fiber core (1), and the quartz cladding (3) is a fluorine-doped quartz cladding (3).
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| CN111856648B (en) | 2020-08-24 | 2021-05-04 | 北京航空航天大学 | Torsion-resistant solid-core polarization-maintaining photonic crystal fiber based on stress distribution anisotropy |
| CN112505824B (en) * | 2020-12-09 | 2022-01-07 | 北京航空航天大学 | Two-layer Air Hole Structure Approximate Single-Polarization Thin-Diameter Solid-Core Polarization-Maintaining Photonic Crystal Fiber |
| CN112859234B (en) * | 2021-03-03 | 2022-04-29 | 唐山学院 | Microstructure optical fiber broadband polarization filter with tunable filtering direction |
| CN116088089A (en) * | 2022-12-19 | 2023-05-09 | 长飞光纤光缆股份有限公司 | High-birefringence solid polarization-maintaining microstructure optical fiber and preparation method thereof |
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