阅读说明：本技术 一种涡旋光色散补偿光纤 (Vortex light dispersion compensation optical fiber ) 是由 岳洋 耿文璞 李意桥 姜纪聪 王英宁 方宇熙 王志 刘艳格 于 2020-06-11 设计创作，主要内容包括：本发明涉及一种涡旋光色散补偿光纤,应用于光纤通信和光学信号处理等技术领域。色散的存在极大限制了非线性效应的出现与应用范围,本发明提供一种可用于实现色散补偿的光纤技术方案：这种光纤,它的包层包含两层高折射率圆环,涡旋光被束缚在环形区域中传播,可以通过改变环形区域和包层的材料改变折射率对比度,进而改变光纤的色散性质,上述横截面结构沿光纤的长度方向不变。本发明的有益效果：该光纤在一定波长范围内有较大负色散,通过适当调节圆环位置、环宽度和光纤材料可以实现负色散大小和所在波长范围的调整。适当增加纤芯包层折射率对比度、环间距离和环宽度,可以使最大负色散变大。(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.)

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

2. A vortex optical dispersion compensating fiber as claimed in claim 1, wherein: the optical fiber comprises a fiber core and a fiber cladding sleeved outside the fiber core, wherein the fiber core is provided with a plurality of optical fibersThe optical fiber cladding comprises a first layer of annular region, an inter-annular cladding, a second layer of 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、n₄The value of (c).

3. A vortex optical dispersion compensating fiber as claimed in claim 2, wherein: 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.

4. A vortex optical dispersion compensating fiber as claimed in claim 1, 2 or 3, 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.

5. A vortex optical dispersion compensating fiber as claimed in claim 4, wherein: the optical fiber material is germanium-doped silicon dioxide or Schott glass or As₂S₃。

6. A vortex optical dispersion compensating fiber as claimed in claim 5, 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.

7. A vortex optical dispersion compensating fiber as claimed in claim 5, 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.

8. A vortex optical dispersion compensating fibre according to claim 1 or 2, wherein: the core is an elliptical core.

9. A vortex optical dispersion compensating fiber as claimed in claim 8, wherein: the core is filled with air.

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 in the center of the vortex rotation, the light intensity at the singularity is zero, the light wave phase is spirally distributed in the direction perpendicular to the propagation direction, and the vortex rotation 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 1Andtwo modes are linearly combinedVortex 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 in the optical fiberIn medium transmission, the chromatic dispersion of the optical fiber is a great obstacle for limiting the transmission quality of the optical fiber, and the longer the transmission distance is, the greater 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 fibers used for dispersion compensation include bragg fibers, photonic crystal fibers, and the like. T.D. Engene et al, 2003, in "Dispersion labeling and compensation by molecular interactions in Omniguide fibers", Optics express,11,1175-1196, propose a Bragg fiber with a defect layer introduced into a periodic multilayer, using TE₀₁The 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, J.Hsu, 2015, proposed a Wavelength tunable dispersion compensating photonic crystal fiber of a hybrid structure in "Wavelength-tunable 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 costly.

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 claddingRefractive 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 distribution₂S₃And the like.

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 HE₂₁Of modesThe dispersion 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 r₄A change in value.

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: