CN108732678B - Photonic crystal fiber - Google Patents
Photonic crystal fiber Download PDFInfo
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- CN108732678B CN108732678B CN201810537357.1A CN201810537357A CN108732678B CN 108732678 B CN108732678 B CN 108732678B CN 201810537357 A CN201810537357 A CN 201810537357A CN 108732678 B CN108732678 B CN 108732678B
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- cladding
- photonic crystal
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- crystal fiber
- ring
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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
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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
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
Abstract
The invention discloses a photonic crystal fiber, which is characterized by comprising:from interior from outer sandwich layer, covering and coating, the cross section of optic fibre is circular, the sandwich layer, covering and coating are all concentric, the sandwich layer is located the inlayer of optic fibre, the center of sandwich layer cross section is the circular port, evenly set up a plurality of semicircular gas pockets in the covering, the covering includes 5 covering rings, every covering ring is connected gradually by the semicircular gas pocket of equidimension and forms, the size of the semicircular gas pocket in the covering ring increases progressively from the inner circle to the outer lane in proper order, the coating is located outmost, the covering adopts silica crystal material to make, the sandwich layer adopts silica crystal material or schottky glass (schott SF57) material to make. The electronic crystal fiber can transmit a plurality of orbital angular momentum modes, and the effective refractive index difference of the mode group reaches 10‑3Magnitude.
Description
Technical Field
The invention belongs to the field of communication, and particularly relates to a photonic crystal fiber.
Background
Orbital Angular momentum (Orbital Angular mometer) is another important parameter of photons in addition to the traditional wavelength, polarization, etc. parameters. With the continuous development of wavelength division multiplexing, time division multiplexing, code division multiplexing and other technologies in the field of optical communication, the transmission data volume of the traditional optical fiber is close to saturation, and OAM provides a brand new degree of freedom for the multiplexing of light beams.
In an OAM optical fiber communication system, an optical fiber supporting OAM mode transmission is a key device. Photonic Crystal Fibers (PCFs), which have attracted considerable attention in recent years, have a relatively complex refractive index profile in their cross-section, usually containing a different arrangement of air holes whose dimensions and wavelength are of approximately the same order and which extend over the entire length of the device, can be confined to the core region of the Fiber at low refractive index. The appearance of photonic crystal fibers shows a new mechanism for controlling photons, and the research field of light transmission is greatly expanded. With the recent gradual and deep research on Photonic Crystal Fibers (PCF) and the gradual maturity of the manufacturing technology of the PCF, the photonic crystal fibers and the optical soliton theory inject the bobby mechanism into the development of the optical communication technology.
For an optical fiber transmitting OAM modes, more modes mean more channels are packed on a single frequency, which significantly increases the amount of information transmitted. In addition, in order to support the stable transmission of OAM modes in the fiber, the fiber must have a high effective index difference to avoid mutual coupling and degeneracy between the individual vector eigenmodes in the fiber. Many specially structured fibers have been proposed to support OAM mode transmission, but the effective refractive index difference between modes in these fibers is always 10-4And in order of magnitude, no more significant improvement can be obtained. Since the difference in effective refractive index between the modes cannot be increased, when OAM mode transmission occurs, odd-even eigenmode walk, birefringence and polarization mode dispersion may occur, affecting the mode purity and causing coupling or crosstalk between the modes.
Disclosure of Invention
The present invention has been made to solve the above problems, and an object of the present invention is to provide a photonic crystal fiber capable of increasing the number of transfer orbital angular momentum modes and reducing confinement loss.
The present invention provides a photonic crystal fiber having the features comprising:
the optical fiber comprises a core layer, a cladding layer and a coating layer from inside to outside, wherein the cross section of the optical fiber is circular, the core layer, the cladding layer and the coating layer are all concentric, and the cladding layer comprises a plurality of cladding rings.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the core cross-section has a circular hole in the center.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the core layer is uniformly provided with four same round air holes which are distributed in a cross shape.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the cladding comprises 5 cladding rings, and the cross section of each cladding ring is a circular ring.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: a plurality of air holes with the same shape and size are uniformly arranged in the cladding ring.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the cross section of the air hole is semicircular, and the semicircular parts are adjacent in sequence.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the semicircular openings of the air holes in the cladding ring face the core layer.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the size of the air holes in the cladding ring increases gradually from the inner ring to the outer ring.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the core refractive index is greater than the cladding refractive index.
In addition, the photonic crystal fiber provided by the present invention may further have the following characteristics: the cladding layer is made of silica crystal material, and the core layer is made of silica crystal material or Schottky SF57 (Schottky SF57) material.
Action and Effect of the invention
The photonic crystal fiber has the beneficial effects that: the optical fiber can transmit a plurality of orbital angular momentum modes, and the refractive index difference of the mode group reaches 10-3Magnitude.
Drawings
FIG. 1 is a schematic cross-sectional view of a photonic crystal fiber according to the present invention;
FIG. 2 is a PCF with silica material for both the core and cladding, EH mode for the highest order EH mode16,1E of (A)ZField intensity distribution diagram;
FIG. 3 shows a PCF with a core layer made of silica material and a cladding layer made of Schottky glass material, in the highest-order EH mode of the EH mode19,1E of (A)ZField intensity distribution diagram;
FIG. 4 shows the | -HE of PCF with both core and cladding made of silicaa+1,1‐EHa‐1,1| an effective refractive index difference Δ n of 2,3,4,7,9,11,13,15,17efffA graph of the relationship as a function of wavelength;
FIG. 5 is the | -HE of PCF with core layer made of silica material and cladding layer made of Schottky glass materiala+1,1‐EHa‐1,1| an effective refractive index difference Δ n of 2,3,4,7,9,11,13,15,17efffA graph of the relationship as a function of wavelength;
FIG. 6 is a schematic cross-sectional view of a photonic crystal fiber according to the present invention.
Detailed Description
In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the following embodiments are specifically described with reference to the attached drawings.
< example one >
FIG. 1 is a schematic cross-sectional view of a photonic crystal fiber according to the present invention.
The photonic crystal fiber is in a strip line shape. The photonic crystal fiber cross-sectional structure is shown in fig. 1, and the photonic crystal fiber 100 includes a core layer 10, a cladding layer 20 and a coating layer 30 from the inside to the outside. And the core layer 10, the cladding layer 20, and the coating layer 30 are all concentric.
The core layer 10 is located at the inner ring of the cross-sectional structure of the photonic crystal fiber 100. The center of the core layer 10 is provided with a circular hole, the radius of the circular hole ranges from 4 to 10 μm, and the thickness of the core layer 10 ranges from 1 to 2 μm. In this embodiment, the radius of the central circular hole is 6.7 μm, and the thickness of the core layer 10 is 1.5 μm.
The cladding 20 is located between the core layer 10 and the coating layer 30, and includes five cladding rings, which are, in order from the inner circumference to the outer circumference of the cladding 20, a first cladding ring 21, a second cladding ring 22, a third cladding ring 23, a fourth cladding ring 24, and a fifth cladding ring 25.
The cladding ring 21 is uniformly provided with a plurality of semicircular air holes 211, the air holes 211 are adjacent to each other in sequence, the radius of each air hole 211 ranges from 0.3 μm to 0.9 μm, and in this embodiment, the radius of each semicircular air hole 211 ranges from 0.6 μm.
The cladding ring 22 is uniformly provided with a plurality of semicircular air holes 221, the air holes 221 are adjacent in sequence, the radius of each air hole 221 ranges from 0.4 μm to 1 μm, and in the embodiment, the radius of each semicircular air hole 221 ranges from 0.65 μm.
The cladding ring 23 is uniformly provided with a plurality of semicircular air holes 231, the air holes 231 are adjacent in sequence, the radius of the air holes 231 ranges from 0.5 μm to 1.1 μm, and in the embodiment, the radius of the semicircular air holes 231 ranges from 0.7 μm.
The cladding ring 24 is uniformly provided with a plurality of semicircular air holes 241, the air holes 241 are adjacent in sequence, the radius of the air holes 241 ranges from 0.6 μm to 1.2 μm, and in this embodiment, the radius of the semicircular air holes 241 ranges from 0.75 μm.
The cladding ring 25 is uniformly provided with a plurality of semicircular air holes 251, the air holes 251 are adjacent in sequence, the radius of the air holes 251 ranges from 0.7 μm to 1.3 μm, and in the embodiment, the radius of the semicircular air holes 251 ranges from 0.8 μm.
The size of the air holes in the cladding ring increases gradually from the inner ring to the outer ring. The spacing between the cladding layers was the same and was 0.1. mu.m. The number of semi-circular holes in each cladding ring is the same, and in this embodiment, the number of holes is 42. The semicircular openings of the air holes in the cladding ring face the core layer.
The coating layer 30 is located at an outer ring of the cross-sectional structure of the photonic crystal fiber 100.
In the present embodiment, the core layer 10 and the cladding layer 20 of the photonic crystal fiber 100 are both made of silica crystal material.
FIG. 2 shows the PCF in EH mode16,1E of (A)ZField intensity distribution graph.
Effective refractive index difference Δ neffFor HEs with the same topological charge number a and the same mode field intensity pattern concentric ring number ba+1，bDie and EHa‐1，bAbsolute value of difference between real parts of effective refractive indices of modes, i.e. | HEa+1,b‐EHa‐1,b| a. Proved by experiments, the effective refractive index difference delta neffGreater than 10‐4In time, the mold HE can be effectively preventeda+1，bAnd EHa‐1，bDegenerating into linear polarization mode LPa，bAnd to intermodal crosstalk between them, resulting in loss or error of data, which is detrimental to fiber transmission. The larger the difference in effective refractive index is, the better. (in HE)a+1，bAnd EHa‐1，bAnd LPa，bWherein a represents the number of topological charges, b represents the number of concentric rings)
The number of all concentric rings in the photonic crystal fiber of the present invention is 1,
FIG. 4 shows the optical fiber |. HEa+1,1‐EHa‐1,1| an effective refractive index difference Δ n of 2,3,4,7,9,11,13,15,17efffGraph of wavelength dependence.
As shown in FIG. 4, the abscissa is wavelength (μm) and the ordinate is | -HEa+1,1‐EHa‐1,1Value of | i.e. the difference in effective refractive index Δ neffIt can be seen that all | HE's are in the 1.3 μm to 1.7 μm banda+1,1‐EHa‐1,1-the values of ═ 2,3,4,7,9,11,13,15,17 are all greater than 10‐3Effectively prevent them from synthesizing LPa,1The mode coupling is generated, and the transmission of more modes is facilitated.
By optimally designing the parameters of the fiber structure, the supported eigenmodes include HEa+1，1Die and EHa‐1，1(a-2-18) in 17 mode groups, where each mode group contains 4 OAM modes, plus TM0,1And TE0,1Collectively, 70 patterns are formed.
< example two >
In the second embodiment, the silica material of the core layer of the optical fiber in the first embodiment is changed to the schottky glass material, and the other materials are not changed.
FIG. 3 shows the PCF in EH mode19,1E of (A)ZField intensity distribution graph.
Effective refractive index difference Δ neffFor HEs with the same topological charge number a and the same mode field intensity pattern concentric ring number ba+1，bDie and EHa‐1，bAbsolute value of difference between real parts of effective refractive indices of modes, i.e. | HEa+1,b‐EHa‐1,b| a. Proved by experiments, the effective refractive index difference delta neffGreater than 10‐4In time, the mold HE can be effectively preventeda+1，bAnd EHa‐1，bDegenerating into linear polarization mode LPa，bAnd to intermodal crosstalk between them, resulting in loss or error of data, which is detrimental to fiber transmission. The larger the difference in effective refractive index is, the better. (in HE)a+1，bAnd EHa‐1，bAnd LPa，bWherein a represents the number of topological charges, b represents the number of concentric rings)
The number of all concentric rings in the photonic crystal fiber of the present invention is 1,
FIG. 5 is |. HEa+1,1‐EHa‐1,1| an effective refractive index difference Δ n of 2,3,4,7,9,11,13,15,17efffGraph of wavelength dependence.
As shown in FIG. 5, the abscissa is wavelength (μm) and the ordinate is | -HEa+1,1‐EHa‐1,1Value of | i.e. the difference in effective refractive index Δ neffIt can be seen that all | HE's are in the 1.3 μm to 1.7 μm banda+1,1‐EHa‐1,1-the values of ═ 2,3,4,7,9,11,13,15,17 are all greater than 10‐3Effectively prevent them from synthesizing LPa,1The mode coupling is generated, and the transmission of more modes is facilitated.
By optimally designing the parameters of the fiber structure, the supported eigenmodes include HEa+1，1Die and EHa‐1，1(a-2-21) for 20 mode groups, each mode group containing 4 OAM modes, plus TM0,1And TE0,1Collectively, 82 patterns are formed.
< example three >
FIG. 6 is a schematic cross-sectional view of a photonic crystal fiber according to the present invention.
As shown in fig. 6, in the optical fiber of the third embodiment, a plurality of identical circular air holes are added to the core layer based on the optical fiber of the second embodiment, the radius of the circle is 0.5 μm, and the distance between the center of the circle and the inner ring of the core layer is the same as the distance between the center of the circle and the outer ring of the core layer. In this embodiment, the number of the circles is 4, the circles are distributed in a cross shape, and the arrangement of the four circular air holes is beneficial to a mode that the core layer transmits more.
Effects and effects of the embodiments
According to the photonic crystal fiber related in the embodiment, the beneficial effects are as follows: the optical fiber can transmit a plurality of orbital angular momentum modes, and the refractive index difference of the mode group reaches 10-3Magnitude.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (6)
1. A photonic crystal fiber, comprising:
a core layer, a cladding layer and a coating layer from inside to outside,
the cross section of the optical fiber is circular, the core layer, the cladding layer and the coating layer are all concentric,
wherein the cladding comprises a plurality of cladding rings,
four identical circular air holes which are distributed in a cross shape are uniformly arranged in the core layer,
a plurality of air holes with the same shape and size are uniformly arranged in the cladding ring, the cross section of each air hole is semicircular, the semicircles are adjacent in sequence,
the size of the air holes in the cladding ring is increased progressively from the inner ring to the outer ring.
2. A photonic crystal fiber according to claim 1, wherein:
wherein the center of the cross section of the core layer has a circular hole.
3. A photonic crystal fiber according to claim 1, wherein:
wherein the cross section of the cladding ring is a circular ring.
4. A photonic crystal fiber according to claim 1, wherein:
wherein the semi-circular openings of the air holes in the cladding ring are all facing the core layer.
5. A photonic crystal fiber according to claim 1, wherein:
wherein the refractive index of the core layer is greater than the refractive index of the cladding layer.
6. A photonic crystal fiber according to claim 1, wherein:
the cladding layer is made of a silica crystal material, and the core layer is made of a silica crystal material or a Schottky glass material.
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| CN201810537357.1A CN108732678B (en) | 2018-05-30 | 2018-05-30 | Photonic crystal fiber |
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| CN109596573B (en) * | 2018-12-18 | 2021-02-26 | 华北水利水电大学 | Novel D-type structure photonic crystal fiber sensor based on surface plasma resonance |
| CN110146953B (en) * | 2019-05-17 | 2020-11-17 | 西安理工大学 | Photonic crystal fiber generating multiple orbital angular momentum modes and design method |
| CN112649915B (en) * | 2020-12-25 | 2022-08-02 | 东北石油大学 | Photonic crystal fiber supporting 114 OAM mode transmission |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101779149A (en) * | 2007-07-02 | 2010-07-14 | 泰科电子瑞侃有限公司 | The hole arranged photonic crystal fiber that is used for low-loss, tight fibre-optical bending application |
| CN106842414A (en) * | 2017-03-08 | 2017-06-13 | 南京邮电大学 | A kind of new photonic crystal fiber for transmitting multiple OAM patterns |
| CN107238890A (en) * | 2017-07-05 | 2017-10-10 | 南京邮电大学 | A kind of photonic crystal fiber for transmitting 22 photon angular momentum moulds |
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| US20030190129A1 (en) * | 2000-08-25 | 2003-10-09 | Ian Bassett | Optical waveguide fibre |
| US20060133753A1 (en) * | 2004-12-22 | 2006-06-22 | Nelson Brian K | Hole assisted fiber device and fiber preform |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101779149A (en) * | 2007-07-02 | 2010-07-14 | 泰科电子瑞侃有限公司 | The hole arranged photonic crystal fiber that is used for low-loss, tight fibre-optical bending application |
| CN106842414A (en) * | 2017-03-08 | 2017-06-13 | 南京邮电大学 | A kind of new photonic crystal fiber for transmitting multiple OAM patterns |
| CN107238890A (en) * | 2017-07-05 | 2017-10-10 | 南京邮电大学 | A kind of photonic crystal fiber for transmitting 22 photon angular momentum moulds |
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