WO2019184256A1

WO2019184256A1 - Photonic-crystal fiber for transmitting photon orbital angular momentum

Info

Publication number: WO2019184256A1
Application number: PCT/CN2018/104569
Authority: WO
Inventors: 罗文勇; 杜城; 李伟; 张洁; 雷琼; 严垒
Original assignee: 烽火通信科技股份有限公司; 锐光信通科技有限公司
Priority date: 2018-03-28
Filing date: 2018-09-07
Publication date: 2019-10-03
Also published as: CN108318965B; CN108318965A

Abstract

A photonic-crystal fiber for transmitting a photon orbital angular momentum (OAM), comprising an annular fiber core (1), an annular micropore layer, and a cladding layer (3). Both the annular fiber core (1) and the cladding layer (3) are made of quartz. The annular fiber core (1) is provided with a fiber core air hole (10) having the same circle center as the annular fiber core (1). The annular micropore layer is provided at an outer side of the annular fiber core (1), and is provided with micropores (2) in the same shape. Multiple micropores (2) are arranged at equal intervals to together form approximately circular regions. The approximately circular region has the same circle center as the fiber core air hole (10). At least one approximately circular region is externally and sequentially arranged in an optical fiber axial direction. The number of micropores (2) on the approximately circular region is equal to an ordinal number of the approximately circular region × 6. Elongated support walls (20) are formed between two adjacent micropores (2) on each approximately circular region in the optical fiber axial direction. The cladding layer (3) is provided at the outer side of the annular micropore layer, and has the same circle center as the annular fiber core (1). The photonic-crystal fiber for transmitting the OAM can support propagation of a fourth-order OAM optical signal, which verifies the practicability that the photonic-crystal fiber transmits an OAM signal, and broadens the application field of photonic-crystal fibers.

Description

Photonic crystal fiber for transmitting photon orbital angular momentum

Technical field

The present invention relates to the field of optical fiber communication technologies, and in particular, to a photonic crystal optical fiber that transmits photon orbital angular momentum.

Background technique

With the rapid development of mobile communication services, Internet technologies such as cloud computing, Internet of Things, and big data are on the rise, and the demand for communication capacity in today's highly informationized society is increasing. In order to improve information transmission capacity and speed, wavelength division multiplexing, polarization multiplexing and space division multiplexing technologies are widely used in single-mode fiber-optic communication systems, and their transmission capacity is close to the Shannon limit. However, the lack of breakthrough innovations makes it extremely difficult to further increase the information's ability to put on each other's capacity.

According to the principle of wave-particle duality, electromagnetic waves are also photons. In 1992, scientists confirmed by experiments that photons have the basic properties of Orbital Angular Momentum (OAM). Electromagnetic waves of the same frequency can theoretically have an infinite number of different OAM values. The core of OAM communication system research is to use photon orbit angular momentum (OAM), an unused electromagnetic wave parameter dimension, for communication, making full use of photon orbital angular momentum to greatly improve the spectrum efficiency and capacity of communication systems to meet the future 10-20 The annual communication capacity is 2-3 orders of magnitude growth demand.

The concept of OAM communication is to use the OAM mode, the order of the electromagnetic wave eigenmode, as the new parameter dimension resource available for modulation or multiplexing, that is, using different l values to represent different coding states or different information channels. , thus opening up new ways to further improve spectrum efficiency. Since the value of l has an infinite range of values, this method may theoretically have the potential to infinitely increase the amount of information carried by photons or electromagnetic waves.

More importantly, the electromagnetic OAM dimension is orthogonal to the dimensions currently used for communication, the phase of the propagation direction, the amplitude, and the like. This means that the introduction of the OAM dimension does not in principle hinder the continued use of the existing communication system. Therefore, on the basis of the existing communication system, the OAM dimension can be directly increased to provide a large amount of new capacity.

However, the above theoretical potential has not been properly explored, developed, and utilized.

Summary of the invention

Aiming at the defects existing in the prior art, the object of the present invention is to provide a photonic crystal fiber that transmits photon orbital angular momentum, which can support 4th order OAM optical signal propagation, and verify the feasibility of transmitting OAM signal of photonic crystal fiber. The application field of photonic crystal fiber.

In order to achieve the above object, the technical solution adopted by the present invention is: a photonic crystal fiber that transmits photon orbital angular momentum, and includes:

a ring core having a core air hole coaxial with the core;

An annular microporous layer, the annular microporous layer is disposed outside the annular core, and the annular microporous layer is provided with micropores of the same shape, and the plurality of micropores are equally spaced and form a near ring a region in which the near-circular annular region is concentric with the core air hole, the proximal annular region being sequentially arranged at least one along the axial direction of the optical fiber; The number of micropores is the number of the near-circular annular region *6; and the adjacent two of the micropores on each of the near-circular annular regions form an elongated supporting wall along the axial direction of the optical fiber;

The cladding layer is disposed outside the annular microporous layer and is concentric with the annular core.

Based on the above technical solution, the near-circular annular region is provided with one.

In the above technical solution, the edge of the micro hole away from the core air hole and the support wall on both sides of the micro hole are respectively provided with a first chamfer; and/or

A second chamfer is disposed at an edge of the microhole adjacent to the core air hole and a side of the support wall located at both sides of the micro hole.

In the above technical solution, each of the micropores located on the same annular region is connected to an edge of the core air hole and forms a circle concentric with the core air hole.

In the above technical solution, each of the micropores located on the same annular region is connected away from the edge of the core air hole and forms a circle concentric with the core air hole.

Based on the above technical solution, the support wall thickness h is smaller than a half wavelength of light, wherein the wavelength is 1550 nm.

In addition to the above technical solution, the inner diameter d of the annular core is 5.0 μm to 7.0 μm.

In addition to the above technical solution, the outer diameter D ₁ of the annular core is 6.5 μm to 8.0 μm.

Based on the above technical solution, a coating layer is further disposed outside the cladding layer.

The invention provides a photonic crystal fiber for transmitting photon orbital angular momentum, which comprises:

a ring core having a core air hole coaxial with the core;

An annular microporous layer, the annular microporous layer is disposed outside the annular core, and the annular microporous layer is provided with micropores in the shape of corn grains, and the plurality of micropores are equally spaced and form a near a circular annular region, the near-circular annular region being concentric with the core air hole, the proximal annular region being sequentially arranged at least one along an axially outward direction of the optical fiber; the near-circular annular region The number of the micropores in the upper circular annular region is *6; the adjacent two of the micropores on each of the proximal annular regions form an elongated supporting wall along the axial direction of the optical fiber. ;

The advantages of the present invention over the prior art are:

The transmission photon orbit angular momentum photonic crystal fiber provided by the invention can transmit the fourth-order orbital angular momentum signal, and the high-order mode of the OAM signal is not distributed in the support wall through the optimized combination design of the micro-hole and the core air hole. This will not form a resonant mode in the support wall, thereby reducing the loss of the fiber. This photonic crystal fiber has excellent characteristics of transmitting OAM signals, which lays a foundation for photon orbit angular momentum communication and design during sensing.

DRAWINGS

1 is a schematic structural view of an end face of a photonic crystal fiber according to an embodiment of the present invention;

2 is a schematic diagram of a half structure of an end face of a photonic crystal fiber according to an embodiment of the present invention, and various parameters of the structure are indicated in the figure;

3 is an electron microscope diagram of an end face of a photonic crystal fiber according to an embodiment of the present invention;

4 is a diffraction diagram of an output of an OAM optical signal of different orders through an optical fiber according to an embodiment of the present invention.

In the figure: 1, annular core; 10, core air hole; 2, micro hole; 20, support wall; 21, first chamfer; 22, second chamfer; 3, cladding; 4, coating.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

Referring to FIG. 1 , an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes a ring core 1, an annular microporous layer, and a cladding layer 3, and both the annular core 1 and the cladding layer 3 are made of quartz. The annular core 1 is provided with a core air hole 10 coaxial with the core; the annular microporous layer is disposed outside the annular core 1 , and the annular microporous layer is provided with micropores of the same shape 2, a plurality of the micropores 2 are equally spaced and collectively form a near-circular annular region, the near-circular annular region being co-centered with the core air hole 10, the near-circular annular region along the optical fiber Having at least one axially outwardly arranged; the number of micropores 2 on the near-circular annular region is the nearest circular annular region number *6; two adjacent ones on each of the proximal circular annular regions An elongated support wall 20 is formed between the micropores 2 along the axial direction of the optical fiber; the cladding 3 is disposed outside the annular microporous layer and is concentric with the annular core 1.

The structural state of the annular microporous layer of the present invention is as shown in FIG. 1. An annular microporous layer is distributed around the outer side of the core air hole 10. The annular microporous layer includes at least one near-circular annular region and a near-circular annular region. Coinciding with the core air hole 10, the near-circular annular region is formed by a plurality of micropores 2 equally spaced, and the number of micropores 2 on the near-circular annular region is respectively (from the inside to the outside along the axial direction of the optical fiber) : The number of micropores 2 in the first round annular region of the first layer is N1=1*6=6, and the number of micropores 2 in the near circular region of the second layer is N2=2*6=12, and so on. The number of micropores 2 of the x-th layer near-circular area is Nx=x*6. Preferably, as shown in FIG. 1, the near-circular annular region is provided with one, and the number of micro-holes 2 is six. At this time, the crystal fiber manufacturing process is the simplest and the optical fiber transmission effect is the best.

Example 2

As shown in FIG. 1 , an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes an annular core 1, an annular microporous layer, and a cladding layer 3; a central core hole 10; the annular microporous layer is disposed outside the annular core 1, and the annular microporous layer is provided with micropores 2 of the same shape, and the plurality of micropores 2 are equally spaced And forming a near-circular annular region, the near-circular annular region being concentric with the core air hole 10, wherein the near-circular annular region is arranged at least one along the axial direction of the optical fiber; The number of micropores 2 on the near-circular annular region is the nearest circular annular region number *6; the adjacent two of the micropores 2 on each of the proximal annular regions are along the axial direction of the optical fiber Forming a strip-shaped support wall 20; the cladding layer 3 is disposed outside the annular microporous layer and is concentric with the annular core 1; further, the microhole 2 is away from the core air hole 10 a first chamfer 21 is disposed at an edge of the support wall 20 on both sides of the microhole 2; and/or the microhole 2 is At a contact edge 20 of the core 10 and the air holes located at both sides of the microporous support wall 2 are provided with a second chamfer 22.

Since the orbital angular momentum energy of light is provided by the light angle to the momentum with energy. However, the support wall 20 - the annular core 1 has a periodic refractive index fluctuation caused by the support wall 20 in the angular direction, which affects the angular movement, resulting in an angular derivative mode, and the annular core 1 and the support wall 20 are present. The periodic refractive index fluctuation caused by the support wall 20 affects the angularly moving optical signal, resulting in an angular derivative mode. The closer the chamfer is to 90 degrees, the smaller the effect, and vice versa. Therefore, By providing a chamfer, the support walls 20 and the two edges of the micropores 2 are brought as close as possible to an angle of 90°, thereby improving signal transmission performance.

Example 3

As shown in FIG. 1 , an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes an annular core 1, an annular microporous layer, and a cladding layer 3; a central core hole 10; the annular microporous layer is disposed outside the annular core 1, and the annular microporous layer is provided with micropores 2 of the same shape, and the plurality of micropores 2 are equally spaced And forming a near-circular annular region, the near-circular annular region being concentric with the core air hole 10, wherein the near-circular annular region is arranged at least one along the axial direction of the optical fiber; The number of micropores 2 on the near-circular annular region is the nearest circular annular region number *6; the adjacent two of the micropores 2 on each of the proximal annular regions are along the axial direction of the optical fiber Forming a strip-shaped support wall 20; the cladding layer 3 is disposed outside the annular microporous layer and is concentric with the annular core 1;

Each of the micropores 2 located on the same annular region is connected to an edge of the core air hole 10 and forms a circle concentric with the core air hole 10;

Of course, each of the micropores 2 located on the same annular region is connected away from the edge of the core air hole 10 and forms a circle concentric with the core air hole 10.

Since the OAM mode exists in the fiber, there is a linear superposition of phase differences for the two fiber fundamental modes:

Therefore, ensuring the circular symmetrical structure of the fiber ring core 1 can reduce the attenuation and disintegration in the OAM mode propagation process.

Example 4

Referring to FIG. 1 and FIG. 2, an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes an annular core 1, an annular microporous layer, and a cladding layer 3; a core air hole 10 having a center of the same; the annular microporous layer is disposed outside the annular core 1; the annular microporous layer is provided with micropores 2 of the same shape, and the plurality of micropores 2 Equally spaced and collectively forming a near-circular annular region that is concentric with the core air hole 10, the proximal annular region being arranged at least one along the axial direction of the optical fiber The number of the micropores 2 on the near-circular annular region is the nearest circular annular region number *6; between each of the two adjacent micropores 2 on each of the proximal circular annular regions An optical fiber axially forms an elongated support wall 20; the cladding 3 is disposed outside the annular microporous layer and is concentric with the annular core 1; wherein the support wall 20 has a thickness h smaller than that of the light Half-wavelength, where the wavelength is 1550 nm, less than half a wavelength can limit the signal light to the ring core 1 more, so as not to let it Leaked out, the structure is designed to ensure low attenuation of the optical fiber, and the length l of the support wall 20 along the axial direction of the optical fiber is 2.5 μm to 5.0 μm.

Example 5

Referring to FIG. 1 and FIG. 2, an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes an annular core 1, an annular microporous layer, and a cladding layer 3; a core air hole 10 having a center of the same; the annular microporous layer is disposed outside the annular core 1; the annular microporous layer is provided with micropores 2 of the same shape, and the plurality of micropores 2 Equally spaced and collectively forming a near-circular annular region that is concentric with the core air hole 10, the proximal annular region being arranged at least one along the axial direction of the optical fiber The number of the micropores 2 on the near-circular annular region is the nearest circular annular region number *6; between each of the two adjacent micropores 2 on each of the proximal circular annular regions The optical fiber axially forms an elongated support wall 20; the cladding 3 is disposed outside the annular microporous layer and is concentric with the annular core 1.

Wherein, the inner diameter d of the annular core 1 is 5.0 μm to 7.0 μm, the outer diameter D ₁ of the annular core ₁ is 6.5 μm to 8.0 μm, and the diameter D ₂ of the cladding 3 is 100-165 μm. Preferably, the transmission loss of the optical fiber at a wavelength of 1550 nm is 125 dB/km.

In the crystal fiber, since the number of modes depends on the inner diameter of the core air hole 10 of the annular core 1 and the width of the annular core 1, a slight change will bring about a large change, and therefore, the accuracy and uniformity of the ring structure. There is a high requirement. In order to facilitate the more accurate drawing, the micropores 2 in the cross section are still designed as a triangular stable distribution, and the width of the support wall 20 is reduced to less than half a wavelength according to the model, so that Support optical resonance mode, reduce light leakage, reduce transmission loss, and optimize the joint structure of support wall 20 and micropores 2, so that the curve on the outer side of the ring is close to a circle, and the transmission performance of the actually developed fiber is tested. The analysis and comparison between the design value and the actual measured value are carried out, thereby further optimizing the optical fiber air hole structure required for the photonic crystal fiber to meet the optimal performance of transmitting the OAM signal, and finally realizing the successful development of the OAM mode signal transmission fiber.

Example 6

Referring to FIG. 1 , an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes an annular core 1, an annular microporous layer, a cladding 3, and a coating layer 4; a core air hole 10 is provided with a core center; the annular microporous layer is disposed outside the annular core 1 , and the annular microporous layer is provided with micropores 2 of the same shape, and the plurality of micro holes 2 equally spaced and collectively forming a near-circular annular region, the near-circular annular region being concentric with the core air hole 10, the proximal annular region being arranged at least along the axial direction of the optical fiber One; the number of the micropores 2 on the near-circular annular region is the nearest circular annular region number *6; the adjacent two micropores 2 on each of the proximal circular annular regions The optical fiber is axially formed into an elongated support wall 20; the cladding 3 is disposed outside the annular microporous layer and is concentric with the annular core 1; the coating 4 is disposed outside the cladding 3, and is coated The layer 4 is made of a material such as a polypropylene resin having a diameter D ₃ of 200 to 350 μm, preferably 245 μm.

Example 7

As shown in FIG. 1 , an embodiment of the present invention provides a photonic crystal fiber that transmits photon orbital angular momentum, and includes a ring core 1, an annular microporous layer, and a cladding layer 3; a central core hole 10; the annular microporous layer is disposed outside the annular core 1, and the annular microporous layer is provided with micropores 2 in the shape of corn grains, a plurality of the micropores 2, etc. Arranging and collectively forming a near-circular annular region, the near-circular annular region being concentric with the core air hole 10, wherein the proximal annular region is arranged at least one along the axial direction of the optical fiber; The number of the micropores 2 on the near-circular annular region is the nearest circular annular region number *6; the adjacent two of the micropores 2 on each of the proximal annular regions are along the optical fiber An elongated support wall 20 is formed in the axial direction; the cladding 3 is disposed outside the annular microporous layer and is concentric with the annular core 1 .

The crystal fiber drawn by the invention has a porous structure, and the air pressure of the core air hole and the micro hole is controlled during drawing, and the air pressure of the core air hole and the micro hole in the structure is controlled by drawing the optical fiber to ensure the optical fiber. The final structure can meet the design requirements. During the process implementation, the micropores and the core air holes are separately controlled. The gas pressure of the core air hole is recorded as P1, and the gas pressure of the micro hole is recorded as P2; the pressure difference between the two is ΔP. The structure and size of the core air holes and micropores are controlled by the difference in pressure between the two parts.

In the following Table 1, there is one parameter in the near-circular annular region, the parameters of the crystal fiber when the number of micropores is six, and the number of transmitted OAM signal modes.

Table 1 Orbital angular momentum transmission photonic crystal fiber embodiment

With two-stage air pressure control, the structure of the optical fiber meets the design requirements, and the photonic orbital angular momentum transmission photonic crystal fiber capable of transmitting the fourth-order OAM signal is successfully drawn.

When the test was carried out using the example 3 in Table 1, the effect was the best. First, the end face structure of the fiber was examined by electron microscopy (see Figure 3). According to the fiber end face structure, the fiber is measured to meet the design requirements, and the attenuation of the OAM signal transmitted by the photonic crystal fiber is tested by the truncation method, and the loss of the 1550 wavelength is measured to be 1.8 dB/km; The test platform is built to verify the OAM signal transmission. The verification result is shown in Figure 4. The OAM fiber can transmit the 4th order OAM signal and the transmission distance reaches 2km. The result is the known photonic crystal fiber. The longest distance to perform OAM signal transmission. The progress of this work has been widely concerned by academic circles at home and abroad. This result fills the gap of domestic OAM photonic crystal fiber and promotes the development of OAM communication research.

The present invention is not limited to the above embodiments, and those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. These improvements and retouchings are also considered as protection of the present invention. Within the scope. The contents not described in detail in the present specification belong to the prior art well known to those skilled in the art.

Claims

A photonic crystal fiber for transmitting photon orbital angular momentum, characterized in that it comprises:

a ring core (1), the core core (1) is provided with a core air hole (10) coaxial with it;

An annular microporous layer, the annular microporous layer is disposed outside the annular core (1), and the annular microporous layer is provided with micropores (2) having the same shape, and the plurality of micropores (2) Equally spaced and collectively forming a near-circular annular region that is concentric with the core air holes (10), the proximal annular regions being sequentially arranged axially outward along the optical fiber At least one; the number of micropores (2) on the near-circular annular region is the nearest circular annular region number *6; two adjacent micropores on each of the proximal circular annular regions (2 Forming an elongated support wall (20) along the axial direction of the optical fiber;

a cladding layer (3), the cladding layer (3) is disposed outside the annular microporous layer and is concentric with the annular core (1).
A photonic crystal fiber for transmitting photon orbital angular momentum according to claim 1, wherein said near-circular annular region is provided with one.
The photonic crystal fiber for transmitting photon orbital angular momentum according to claim 1, wherein said microhole (2) is away from an edge of said core air hole (10) and is located on both sides of said microhole (2) The support walls (20) are each provided with a first chamfer (21); and/or

a second chamfer (22) is disposed at an edge of the microhole (2) adjacent to the core air hole (10) and the support wall (20) located at two sides of the micro hole (2) .
The photonic crystal fiber for transmitting photon orbital angular momentum according to claim 1, wherein each of said micropores (2) located on said nearly circular annular region is adjacent to said core air hole (10) The edges are joined and form a circle that is concentric with the core air hole (10).
The photonic crystal fiber for transmitting photon orbital angular momentum according to claim 1, wherein each of said micropores (2) located on said nearly circular annular region is away from said core air hole (10) The edges are joined and form a circle that is concentric with the core air hole (10).
The photonic crystal fiber for transmitting photon orbital angular momentum according to any one of claims 1 to 5, wherein the support wall (20) has a thickness h smaller than a half wavelength of light, wherein the wavelength is 1550 nm.
A photonic crystal fiber for transmitting photon orbital angular momentum according to claim 1, wherein said annular core (1) has an inner diameter d of from 5.0 μm to 7.0 μm.
As claimed in claim 1 photon transfer orbital angular momentum of photonic crystal fiber, wherein: the annular core (1) the outer diameter D 1 is 6.5μm ~ 8.0μm.
The photonic crystal optical fiber for transmitting photon orbital angular momentum according to claim 1, wherein a coating (4) is further disposed outside the cladding (3).
A photonic crystal fiber for transmitting photon orbital angular momentum, characterized in that it comprises:

a ring core (1), the core core (1) is provided with a core air hole (10) coaxial with it;

An annular microporous layer, the annular microporous layer is disposed outside the annular core (1), and the annular microporous layer is provided with micropores (2) in the shape of corn grains, and the plurality of micropores ( 2) equally spaced and collectively forming a near-circular annular region that is concentric with the core air hole (10), the near-circular annular region being axially outward along the fiber axis Arranging at least one; the number of micropores (2) on the near-circular annular region is the nearest circular annular region number *6; two adjacent micropores on each of the proximal circular annular regions (2) forming an elongated support wall (20) along the axial direction of the optical fiber;

a cladding layer (3), the cladding layer (3) is disposed outside the annular microporous layer and is concentric with the annular core (1).