CN113655561A - High-birefringence low-limiting-loss photonic crystal fiber - Google Patents
High-birefringence low-limiting-loss photonic crystal fiber Download PDFInfo
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- CN113655561A CN113655561A CN202010422072.0A CN202010422072A CN113655561A CN 113655561 A CN113655561 A CN 113655561A CN 202010422072 A CN202010422072 A CN 202010422072A CN 113655561 A CN113655561 A CN 113655561A
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- 239000000835 fiber Substances 0.000 title claims abstract description 61
- 239000004038 photonic crystal Substances 0.000 title claims abstract description 43
- 238000005253 cladding Methods 0.000 claims abstract description 17
- 239000013307 optical fiber Substances 0.000 claims abstract description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
- 235000012239 silicon dioxide Nutrition 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 239000000758 substrate Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 abstract description 8
- 230000003287 optical effect Effects 0.000 abstract description 6
- 238000004891 communication Methods 0.000 abstract description 5
- 230000010287 polarization Effects 0.000 abstract description 4
- 230000008878 coupling Effects 0.000 abstract description 3
- 238000010168 coupling process Methods 0.000 abstract description 3
- 238000005859 coupling reaction Methods 0.000 abstract description 3
- 238000000034 method Methods 0.000 abstract description 3
- 230000008054 signal transmission Effects 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 4
- 230000005684 electric field Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000005855 radiation Effects 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
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
- G02B6/02361—Longitudinal structures forming multiple layers around the core, e.g. arranged in multiple rings with each ring having longitudinal elements at substantially the same radial distance from the core, having rotational symmetry about the fibre axis
-
- 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
- G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
- G02B6/02357—Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Abstract
The invention discloses a photonic crystal fiber with high birefringence and low limiting loss. The cladding of the optical fiber contains five layers of air holes in a regular hexagon shape. The air holes comprise oval air holes and round air holes, and the arrangement mode is vertically and symmetrically arranged. The first four rows of the upper half part of the optical fiber are formed by staggered arrangement of large oval air holes and round air holes, two ends of a row in the center are respectively provided with two large oval air holes, two sides close to the fiber core are provided with small oval air holes, the rest are round air holes with the same size, and the distance between every two adjacent air holes is equal to the distance from the center of the small oval air holes on the left side and the right side of the fiber core to the center of the optical fiber. The photonic crystal fiber has high birefringence and low restrictive loss performance, can reduce the coupling in two polarization directions in the signal transmission process, greatly improves the transmission distance of optical signals, and is suitable for long-distance optical fiber communication systems.
Description
Technical Field
The invention relates to the technical field of optical fibers, in particular to a photonic crystal optical fiber with high birefringence and low limiting loss.
Background
The concept of Photonic Crystal Fiber (PCF) was first introduced in 1992 by p.st.j.russel. The refractive index of the photonic crystal fiber has a two-dimensional periodicity in the fiber cross-section, and this two-dimensional periodic structure remains constant in the direction of the fiber longitudinal axis. The structure of the photonic crystal fiber is greatly different from that of the conventional fiber, the conventional fiber is a solid fiber core and a solid cladding, the materials of the conventional fiber are generally silicon dioxide, and air holes with a certain regular arrangement are introduced into the cladding of the photonic crystal fiber. It has "singular" characteristics that traditional optical fiber can not realize, such as high double refraction, flexible dispersion characteristic, nonlinear characteristic and radiation-resistant characteristic. The method has wide application prospect in the fields of optical communication, optical devices, optical sensing and laser.
Losses during signal transmission have a large impact in long-haul fiber optic communication systems and there is a need to reduce the coupling between the two polarization axis signals. The birefringence coefficient of the existing photonic crystal fiber is mostly 10-4～10-3The photonic crystal fiber structure with high birefringence and low restrictive loss inherits the excellent characteristic of flexible design of the photonic crystal fiber, and achieves both high birefringence and low restrictive loss at the incident light wavelength of 1550 nm. The photonic crystal fibers with different transmission characteristics can be conveniently manufactured by simply adjusting the structural parameters, and the method has potential application value in the aspect of long-distance optical fiber communication.
Disclosure of Invention
The invention overcomes the defects of lower birefringence coefficient and higher restrictive loss of the conventional photonic crystal fiber, and provides the photonic crystal fiber with high birefringence and low restrictive loss, which is suitable for long-distance transmission.
The invention provides a high-birefringence low-restriction-loss photonic crystal fiber which comprises a substrate material and cladding air holes, wherein the substrate material is silicon dioxide, the air holes are five layers, and the air holes are regularly distributed in a regular hexagon according to a certain arrangement rule.
Furthermore, the shape of the air holes in the photonic crystal fiber cladding comprises an ellipse and a circle, the whole arrangement structure is a regular hexagon array, and the arrangement mode is vertically and symmetrically arranged. The structure of the upper half part of the photonic crystal fiber is as follows: the first four layers are formed by large oval air holes and round air holes which are arranged in a staggered mode, two ends of the middle layer are respectively provided with two large oval air holes, the left side and the right side, close to the fiber core, of each middle layer are respectively provided with a small oval air hole, and the rest of the middle layer are round air holes. The hole spacing between two adjacent air holes of the photonic crystal fiber is equal to the distance from the center of the small oval air holes on the left side and the right side of the fiber core to the center of the fiber. The major semi-axis length of the large oval air hole in the cladding, the major semi-axis length of the small oval air hole and the radius length of the round air hole are equal, and the major axis of the large oval air hole and the major axis of the small oval air hole in the central layer are perpendicular to the major axis direction of the rest large oval air holes in the cladding.
The invention provides a photonic crystal fiber with high birefringence and low restrictive loss, which has the following characteristics compared with the conventional photonic crystal fiber:
realizes high birefringence cut-off-free single-mode transmission, and the birefringence coefficient can reach 3.51 multiplied by 10 at 1550nm-2；
Has low limiting loss, and the loss at 1550nm is as low as 10-10dB/m, reduced by 4-5 orders of magnitude, is suitable for the long distance optical fiber transmission system.
Drawings
FIG. 1 is a schematic cross-sectional view of a high birefringence, low confinement loss photonic crystal fiber according to an embodiment of the present invention. Wherein 1: a large oval air hole; 2: a circular air hole; 3: a small oval air hole; Λ: the air hole spacing; b: the length of the major semiaxis of the major ellipse and the minor ellipse, and the radius of the circular air hole; a: the length of the major ellipse air hole and the minor semi-axis; a is1: the length of the short half shaft of the small oval air hole.
FIG. 2 shows the variation of birefringence with wavelength when the ellipticity of the small elliptical air holes of the photonic crystal fiber in the example of FIG. 1 takes different values, and shows the comparison of the birefringence coefficients of a part of the conventional photonic crystal fiber introduced with elliptical air holes at 1550nm, which shows that the birefringence coefficients of the photonic crystal fiber in the example of FIG. 1 are significantly improved.
FIG. 3(a) is a graph showing the variation of the confinement loss of the fast axis of the optical fiber with the wavelength when the ellipticity of the small elliptical air holes of the photonic crystal fiber in the example of FIG. 1 is different, and FIG. 3(b) is a graph showing the variation of the confinement loss of the slow axis of the optical fiber with the wavelength when the ellipticity of the small elliptical air holes of the photonic crystal fiber in the example of FIG. 1 is different, from which it can be seen that the confinement loss of the photonic crystal fiber at the wavelength of 1550nm can be as low as 10-10dB/m, andcompared with the prior photonic crystal fiber with the oval air holes, the optical fiber is reduced by four to five orders of magnitude.
FIG. 4 is a graph of the variation of the electric field energy with the ellipticity η for the high birefringence, low confinement loss photonic crystal fiber of the example of FIG. 1.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
FIG. 1 is a schematic structural diagram of a cross section of a high birefringence photonic crystal fiber according to this embodiment. The optical fiber includes a core and a cladding portion. The substrate material is silicon dioxide. The cladding contains 5 layers of air holes which are arranged in a regular hexagon, and the number of the air holes is 11. The air holes in the cladding comprise large oval air holes 1, round air holes 2 and small oval air holes 3, and the arrangement mode is vertically and symmetrically arranged. The radius of the optical fiber is r; the length of the major semi-axis of the air hole of the big ellipse and the minor semi-axis is b, and the length of the minor semi-axis is a and a respectively1(ii) a The radius of the circular hole is b; the space between two small elliptical air holes on two sides of the fiber core is 2 lambada, and the hole spaces between the other adjacent air holes are lambada. The structure of the upper half part of the optical fiber is as follows: the front 4 layers of air holes are formed by staggered arrangement of round air holes and large oval air holes, the 1 st layer is 6 large oval air holes 1, and the ellipticity of the air holes is eta1A/b. The middle layer has 10 air holes, the left and right ends are respectively provided with two large elliptical air holes 1, the left and right sides close to the fiber core are respectively provided with a small elliptical air hole, and the ellipticity of the small elliptical air holes is eta ═ a1And b, the rest are round air holes with equal size. By changing the ellipticity eta of the small elliptical air holes around the fiber core, different transmission characteristics can be obtained so as to meet different communication environments and conditions.
The structural parameters of the photonic crystal fiber in the embodiment are as follows: Λ 0.87 μm, a 0.35 μm, b 0.4 μm, η1＝0.8，r＝5μm，a1Respectively take 0.08 μm, 0.16 μm and 0.24 μm, and correspondingly eta respectively takes 0.2, 0.4 and 0.6. The variation of the birefringence coefficient of the corresponding high-birefringence low-restrictive-loss photonic crystal fiber with the wavelength and the partial prior introductionThe birefringence coefficient of the photonic crystal fiber with elliptical air holes at 1550nm is shown in FIG. 2. The following conclusions can be drawn from the observation of FIG. 2:
the high-birefringence low-limiting-loss photonic crystal fiber has obviously improved birefringence coefficient, and when eta is 0.2 at the common wavelength of 1550nm, the birefringence coefficient is as high as 3.51 multiplied by 10-2Compared with the birefringence coefficients of the existing photonic crystal fibers with better performance, which are listed in the figure, the birefringence coefficients are greatly improved, the coupling degree of the transmission signals in two polarization directions can be reduced, and the transmission distance of the optical signals can be increased.
The limiting losses of the fast axis and the slow axis of the corresponding high-birefringence low-limiting-loss photonic crystal fiber are shown in fig. 3(a) and fig. 3(b) respectively according to the wavelength. Viewing fig. 3, it can be seen that:
at the wavelength of 1550nm, the limiting losses of two polarization axes of the photonic crystal fiber are as low as 10-10dB/m, the loss reduction contributes to an increase in optical signal transmission distance.
When the ellipticity η of the small ellipse varies from 0.2 to 0.8, the electric field energy of the corresponding high birefringence low confinement loss photonic crystal fiber as a function of η is shown in fig. 4. Viewing fig. 4, it can be seen that:
when the ellipticity is larger, the electric field energy is more concentrated on the core portion.
The above examples are intended to illustrate the invention without limiting its scope. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.
Claims (3)
1. A photonic crystal fiber with high birefringence and low restrictive loss is a photonic crystal fiber structure which is formed by opening a plurality of air holes in a fiber cladding taking silicon dioxide as a substrate and comprises a cladding and a fiber core; the cladding comprises five layers of air holes arranged in an array, and is characterized in that the fiber core is solid; the air holes in the cladding are arranged in an overall manner: the whole structure is a regular hexagon array which is distributed in a vertical symmetry way; the air holes in the upper half part of the cladding layer are arranged in the following mode: the front four layers of air holes are formed by staggered arrangement of round air holes and large oval air holes; the left end and the right end of the middle layer are large oval air holes, the left side and the right side close to the fiber core are respectively provided with a small oval air hole, and the rest are round air holes with equal sizes.
2. A high birefringence, low confinement loss photonic crystal fiber as claimed in claim 1, wherein the radius of the circular air holes in said cladding is equal to the length of the major semi-axis of the large elliptical air holes and the major semi-axis of the small elliptical air holes; the distance between two adjacent air holes is equal to the distance from the center of the small elliptical air hole at the left side and the right side of the fiber core to the center of the optical fiber, and the value is larger than the diameter of the circular air hole and smaller than 1.5 times of the diameter of the circular air hole.
3. A high birefringence, low confinement loss photonic crystal fiber as claimed in claim 1, wherein the major axes of said large elliptical air holes and said small elliptical air holes in the central layer are perpendicular to the major axes of the remaining large elliptical air holes in said cladding.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005003932A (en) * | 2003-06-12 | 2005-01-06 | Mitsubishi Cable Ind Ltd | Polarization retention photonic crystal fiber and its fiber edge working method |
| TWM484112U (en) * | 2014-04-25 | 2014-08-11 | Univ Chien Hsin Sci & Tech | Birefringence photonic crystal optical fiber |
| CN104991305A (en) * | 2015-07-14 | 2015-10-21 | 燕山大学 | Oval high-birefringence soft glass photonic crystal fiber |
| CN108152881A (en) * | 2018-01-26 | 2018-06-12 | 西安邮电大学 | A kind of sulphur system high double-refraction photon crystal fiber in the range of 2 to 5 micron waveband |
| CN108415121A (en) * | 2018-05-07 | 2018-08-17 | 上海理工大学 | A kind of high birefringence double-core photonic crystal fiber polarization beam apparatus |
| CN212276022U (en) * | 2020-05-12 | 2021-01-01 | 华北电力大学（保定） | High-birefringence low-limiting-loss photonic crystal fiber |
-
2020
- 2020-05-12 CN CN202010422072.0A patent/CN113655561A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005003932A (en) * | 2003-06-12 | 2005-01-06 | Mitsubishi Cable Ind Ltd | Polarization retention photonic crystal fiber and its fiber edge working method |
| TWM484112U (en) * | 2014-04-25 | 2014-08-11 | Univ Chien Hsin Sci & Tech | Birefringence photonic crystal optical fiber |
| CN104991305A (en) * | 2015-07-14 | 2015-10-21 | 燕山大学 | Oval high-birefringence soft glass photonic crystal fiber |
| CN108152881A (en) * | 2018-01-26 | 2018-06-12 | 西安邮电大学 | A kind of sulphur system high double-refraction photon crystal fiber in the range of 2 to 5 micron waveband |
| CN108415121A (en) * | 2018-05-07 | 2018-08-17 | 上海理工大学 | A kind of high birefringence double-core photonic crystal fiber polarization beam apparatus |
| CN212276022U (en) * | 2020-05-12 | 2021-01-01 | 华北电力大学（保定） | High-birefringence low-limiting-loss photonic crystal fiber |
Non-Patent Citations (2)
| Title |
|---|
| 姜凌红;郑义;侯蓝田;郑凯;: "低有效模场面积的高双折射PCF的优化设计", 半导体光电, no. 06, 15 December 2013 (2013-12-15) * |
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