CN111562649B

CN111562649B - Vortex light dispersion compensation optical fiber

Info

Publication number: CN111562649B
Application number: CN202010527020.XA
Authority: CN
Inventors: 岳洋; 耿文璞; 李意桥; 姜纪聪; 王英宁; 方宇熙; 王志; 刘艳格
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2020-06-11
Filing date: 2020-06-11
Publication date: 2022-04-12
Anticipated expiration: 2040-06-11
Also published as: CN111562649A

Abstract

The invention relates to a vortex optical dispersion compensation optical fiber, which is applied to the technical fields of optical fiber communication, optical signal processing and the like. The existence of chromatic dispersion greatly limits the appearance and application range of nonlinear effect, the invention provides a technical scheme of optical fiber for realizing chromatic dispersion compensation, which comprises the following steps: the optical fiber has a cladding comprising two high-refractive-index rings, vortex light is bound in the annular region to propagate, the refractive index contrast can be changed by changing the materials of the annular region and the cladding, and the dispersion property of the optical fiber can be further changed, and the cross-sectional structure is constant along the length direction of the optical fiber. The invention has the beneficial effects that: the optical fiber has larger negative dispersion in a certain wavelength range, and the adjustment of the size of the negative dispersion and the wavelength range can be realized by properly adjusting the position of the circular ring, the width of the circular ring and the material of the optical fiber. The maximum negative dispersion can be increased by properly increasing the core cladding refractive index contrast, the inter-ring distance and the ring width.

Description

Vortex light dispersion compensation optical fiber

Technical Field

The invention relates to a vortex optical annular optical fiber, in particular to an annular optical fiber with dispersion compensation characteristics. The method is applied to the technical fields of optical fiber communication, optical signal processing and the like.

Background

The vortex rotation has unique field distribution, a phase singularity exists at the central position of the vortex rotation, the light intensity at the singularity is zero, and the light wave phase isThe spiral distribution is vertical to the propagation direction, and the spiral distribution has orbital angular momentum. The vortex rotation is divided into polarized vortex rotation and phase vortex rotation, and the polarized vortex rotation is composed of radial vector light beam TM₀₁Sum angular vector beam TE₀₁Two modes, phase vortex rotation also known as Orbital Angular Momentum (OAM) vortex rotation, the OAM mode can be expressed as OAM_l,mWhere l (l ═ 1, ± 2, ± 3 …) is the topological charge, and m is the radial order corresponding to the intensity distribution of the mode in the radial direction. OAM modes for transmission in an optical fiber may consist of the vector eigenmodes by the following relationship:

OAM vortex rotation induced by a topological charge number of 1

And

two modes are linearly combined

Vortex rotation can be used as a carrier for transmitting optical information, which is different from phase and polarization, and the vortex rotation provides new dimension for information transmission and expands new channels.

When light is transmitted in an optical fiber, the chromatic dispersion of the optical fiber is a large obstacle for limiting the transmission quality of the optical fiber, and the farther the transmission distance is, the larger the dispersion effect is, which will cause intersymbol interference to increase the error rate and reduce the information transmission efficiency and distance. To minimize dispersion loss and improve fiber performance, dispersion compensating fibers with negative dispersion are used to improve fiber performance by periodically balancing the positive dispersion of the fiber. Optical fiber Bragg Grating for Dispersion CompensationLattice fibers, photonic crystal fibers, and the like. T.D. Engene et al, 2003, in "Dispersion labeling and compensation by modal interactions in Omniguide fibers", Optics express,11,1175-₀₁The modes produce large negative dispersion, but the actual transmission loss may not be very low, as can be seen from their principle. Hsu et al in 2015 propose a Wavelength tunable dispersion compensating photonic crystal fiber with a mixed structure in "Wavelength-tunable dispersion compensating photonic crystal fibers usable for capacitive/coarse Wavelength division multiplexing systems", Journal of light Technology,33,2240-2245(2015), which has a large negative dispersion coefficient, but the manufacturing process of the photonic crystal fiber is complicated and the cost is high.

Disclosure of Invention

In view of the above, the present invention provides a vortex optical dispersion compensation fiber having a large negative dispersion, which aims to transmit vortex rotation and simplify the structure of the fiber having a large negative dispersion characteristic.

The technical scheme adopted by the invention is specifically as follows:

the vortex optical dispersion compensation fiber with larger negative dispersion comprises a fiber core and a fiber cladding sleeved outside the fiber core, wherein the fiber cladding comprises a first annular region, an inter-annular cladding, a second annular region and an outer fiber cladding, and the first annular region, the inter-annular cladding and the second annular region are sequentially arranged between the fiber core and the outer fiber cladding from inside to outside; wherein: the core, the first annular region, the inter-annular cladding, the second annular region, and the outer fiber cladding have a refractive index n₁、n₂、n₃、n₄、n₅Satisfy n₁、n₃、n₅Is less than n₂、n₄The value of (a), i.e., the refractive index of each of the first and second annular regions is greater than that of the other region; the optical fiber material can be germanium-doped silicon dioxide, Schott glass and As under the condition of meeting the refractive index distribution₂S₃Of equal materialAnd (4) combining.

In this structure, the loop width of the first layer of loop region is greater than the loop width of the second layer of loop region in the cross section of the optical fiber. On the basis that the refractive index of the annular region is higher than that of the cladding region, the mode is limited to be transmitted in two annular regions, the effective refractive index of the vortex rotation in the annular region of the first layer is reduced faster along with the wavelength than that in the annular region of the second layer under certain refractive index contrast and structural parameters, the refractive indexes of the same mode in the two rings are close to each other at a certain wavelength, and strong mode coupling occurs near the wavelength to form a composite mode, namely a symmetric mode and an anti-symmetric mode, wherein the symmetric mode has negative dispersion and the anti-symmetric mode has positive dispersion. The vortex optical dispersion compensation fiber with larger negative dispersion adopts a symmetrical mode with larger negative dispersion.

The invention has the beneficial effects that: by selecting the materials of the annular region and the fiber core cladding, properly adjusting the width of the ring or the positions of the two annular regions, the adjustment of the maximum negative dispersion of different modes and the adjustment of the wavelength range can be realized. Numerical calculations show that by appropriately increasing the distance (r) between the two annular zones₃-r₁) The negative dispersion can be increased and the wavelength range in which there is a large negative dispersion is tightened. The wavelength of the maximum negative dispersion can be changed by properly adjusting the width of the annular region of the first layer.

Drawings

FIG. 1 is a schematic cross-sectional structure of an optical fiber of the present invention.

FIG. 2 shows the structure of an optical fiber according to the present invention₁＝1μm，r₂＝2μm，r₃＝12μm，r₄TE at 12.6 μm₀₁、TM₀₁And HE₂₁The dispersion of the mode varies with wavelength.

FIG. 3 shows the structure of an optical fiber according to the present invention₁＝1μm，r₃TE at 10 μm₀₁Mode dispersion with wavelength, r₂And r₄A change in (c).

FIG. 4 shows the structure of an optical fiber according to the present invention₁＝1μm，r₂TE at 2 μm₀₁Mode dispersion with wavelength, r₃And r₄Variation of valueAnd (4) transforming.

FIG. 5 is a HE in an optical fiber configuration of the present invention₂₁、HE₃₁、HE₄₁And HE₆₁Dispersion of (2) varies with wavelength.

In the figure: 1. a fiber core; 2. a first layer of annular regions; 3. an inter-annular cladding; 4. a second layer of annular regions; 5. an outer fiber cladding;

r₁a core radius; r is₂A first layer annular zone radius; r is₃Inter-ring cladding radius; r is₄A second layer annular zone radius.

Detailed Description

The following further describes embodiments of the present invention with reference to the accompanying drawings:

example 1:

the vortex optical dispersion compensation fiber with larger negative dispersion of the invention is shown in figure 1, and comprises a fiber core 1, a first annular region 2, an inter-annular cladding 3, a second annular region 4 and an outer fiber cladding 5 from inside to outside, wherein the refractive indexes are n respectively₁、n₂、n₃、n₄、n₅The first layer annular region 2 and the second layer annular region 4 are concentric high-refractive-index circular rings, the refractive index is greater than that of other regions, and the refractive index distribution satisfies n₁＝n₃＝n₅，n₂＝n₄，n₁<n₂The optical fiber material can be germanium-doped silicon dioxide, Schott glass and As under the condition of meeting the refractive index distribution₂S₃And the higher-order OAM mode can also have larger negative dispersion by adjustment. In this embodiment, the material of the annular region is silica doped with germanium at a molar concentration of 40 mol%, the material of the core cladding is silica, and the cross-sectional structure is constant along the length direction of the optical fiber.

When r is₁＝1μm，r₂＝2μm，r₃＝12μm，r₄TE at 12.6 μm₀₁、TM₀₁And HE₂₁The dispersion of the mode as a function of wavelength is shown in fig. 2. It can be seen that the different modes of vortex light transmitted in the optical fiber of the present invention can achieve large negative dispersion.

FIG. 3 is a drawing showing₁＝1μm，r₃R is different at 10 μm₂And r₄TE corresponding to value₀₁The dispersion of a mode is plotted against wavelength. As can be seen from the figure, by adjusting r₂And r₄I.e. the width of the annular region, the wavelength range in which the negative dispersion is located can be selected.

FIG. 4 is a drawing showing₁＝1μm，r₂R is different at 2 μm₃And r₄TE corresponding to value₀₁The dispersion of a mode is plotted against wavelength. As can be seen from the figure, by adjusting r₃And r₄That is, the distance between the two annular regions can change the maximum negative dispersion of the fiber and the bandwidth of the fiber with the negative dispersion under the condition that the wavelength is basically unchanged.

Example 2:

the vortex optical dispersion compensation fiber structure of the present embodiment is shown in fig. 1, and includes a fiber core 1, a first annular region 2, an inter-annular cladding 3, a second annular region 4, and an outer fiber cladding 5 from inside to outside, and refractive indexes n₁、n₂、n₃、n₄、n₅The first layer annular region 2 and the second layer annular region 4 are concentric high-refractive-index circular rings, and the refractive index distribution satisfies n₁＝n₃＝n₅，n₂＝n₄，n₁<n₂. In this example, the material used was Schott glass, the material of the annular region was SF57 glass, the refractive index of the material was 1.80 at a wavelength of 1550nm, the core cladding material was SF2 glass, the refractive index of the material was 1.62 at a wavelength of 1550nm, and the cross-sectional structure was constant along the length of the fiber.

FIG. 5 is HE₂₁、HE₃₁、HE₄₁And HE₆₁The dispersion of (2) varies with wavelength, and the parameter of each mode in the figure is HE₂₁：r₁＝1μm，r₂＝1.7μm，r₃＝5μm，r₄＝5.6μm；HE₃₁：r₁＝1μm，r₂＝1.95μm，r₃＝5μm，r₄＝5.6μm；HE₄₁：r₁＝1μm，r₂＝1.95μm，r₃＝5μm，r₄＝5.4μm；HE₆₁：r₁＝1μm，r₂＝3μm，r₃＝5μm，r₄5.6 μm. It can be seen from the figure that higher order mode vortex rotation of the transmission in the optical fiber of the present invention can achieve larger negative dispersion.

Further, the fiber core 1 with a circular cross section can be designed into an elliptical fiber core, and the fiber core can also be filled with air, so that vortex optical dispersion compensation is realized through design.

There are many choices and combinations of fiber materials that can be used to achieve dispersion compensation, and any further extension that includes the present invention is also within the scope of the present invention.

The foregoing detailed description of embodiments of the invention has been presented with reference to the accompanying drawings, which are included to provide a further understanding of the invention. The scope of the invention is not limited to the disclosed embodiments and is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and higher order vortex optical modes with large negative dispersion present in the inventive fiber. Therefore, the technical idea of the invention and only obvious changes of the technical scheme are all within the protection scope of the invention.

Claims

1. A vortex optical dispersion compensating fiber, comprising: the optical fiber core is provided with two concentric annular regions, and the refractive index of the two concentric annular regions is higher than that of the cladding;

the optical fiber comprises a fiber core and an optical fiber cladding sleeved outside the fiber core, wherein the optical fiber cladding comprises a first annular region, an inter-annular cladding, a second annular region and an outer optical fiber cladding; the first annular region, the inter-annular cladding and the second annular region are sequentially arranged between the fiber core and the outer fiber cladding from inside to outside; the refractive index n of the fiber core, the first annular region, the inter-annular cladding, the second annular region and the outer fiber cladding₁、n₂、n₃、n₄、n₅Satisfies the following conditions: n is₁、n₃、n₅Is less than n₂、n₄A value of (d);

the ring width of the first layer of ring-shaped region is larger than that of the second layer of ring-shaped region on the cross section of the optical fiber.

2. A vortex optical dispersion compensating fiber as claimed in claim 1, wherein: by suitably increasing the distance r between the two annular regions₃-r₁The negative dispersion can be enlarged, and the wavelength range with larger negative dispersion is narrowed; wherein r is₃Is the width of the inter-annular cladding, r₁Is the core width.

3. A vortex optical dispersion compensating fiber as claimed in claim 2, wherein: the optical fiber material is germanium-doped silicon dioxide or Schott glass or As₂S₃。

4. A vortex optical dispersion compensating fiber as claimed in claim 3, wherein: the first layer of annular region and the second layer of annular region are made of germanium-doped silica, and the core cladding material is silica.

5. A vortex optical dispersion compensating fiber as claimed in claim 3, wherein: the material of the first layer of annular region and the second layer of annular region is SF57 glass, and the refractive index of the material at the wavelength of 1550nm is 1.80; the core cladding material was SF2 glass, which had a refractive index of 1.62 at a wavelength of 1550 nm.

6. A vortex optical dispersion compensating fiber as claimed in claim 1, wherein: the core is an elliptical core.

7. A vortex optical dispersion compensating fiber as claimed in claim 6, wherein: the core is filled with air.