An all-solid anti-resonant optical fiber

Abstract

The application belongs to the technical field of solid anti-resonant fiber communication, and particularly relates to a full-solid anti-resonant fiber for generating and transmitting flat-top light. The full-solid anti-resonant fiber comprises a cladding, a core inner layer and a high-refractive annular nested core outer layer arranged in the cladding, the high-refractive annular nested core outer layer is composed of 16 two-annular inscribed nested elements, and adjacent two of the nested elements are tangent and the 16 nested elements are all tangent to the core inner layer. The application applies the anti-resonant structure to the flat-top fiber for the first time, which greatly reduces the constraint loss of the flat-top fiber in generation and propagation, and the full-solid anti-resonant fiber has low constraint loss of the flat-top light beam in transmission, large mode area, and generates and transmits low-loss flat-top light beams with wavelengths from 1100nm to 2200nm, which opens up the application of the anti-resonant fiber in beam shaping.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid anti-resonant fiber communication, and particularly relates to a full solid anti-resonant fiber. BACKGROUND

[0002] The conventional anti-resonant fiber is hollow, and utilizes the combined action of anti-resonance of the core mode and the coupling suppression between the air and the mode in the cladding to achieve better optical performance. The hollow anti-resonant fiber (ARF) is a kind of hollow fiber, and light can be confined in the hollow with a refractive index smaller than the material of the fiber to conduct along the fiber axis.

[0003] In recent years, the hollow anti-resonant fiber (ARF) has experienced great development, and the hollow anti-resonant fiber (ARF) has the potential to exceed the loss of the existing quartz fiber, and is favored due to its fast transmission speed, wide transmission bandwidth and low transmission loss.

[0004] However, the hollow cavity of the hollow anti-resonant fiber (ARF) in the prior art is mainly filled with air or other gas, so that the hollow anti-resonant fiber (ARF) is prone to collapse of the unstable fiber structure, which inevitably increases the difficulty of fiber stretching and manufacturing process. SUMMARY

[0005] In order to solve the defects of the prior art, the present application provides a full solid anti-resonant fiber for generating a flat-top light beam, which first uses the anti-resonant fiber for the flat-top fiber, and the full solid anti-resonant fiber structure is more stable, solving the problem of difficult manufacturing of the conventional hollow anti-resonant fiber.

[0006] In order to achieve the above purpose, the present application is realized by the following technical scheme:

[0007] The present application is a full solid anti-resonant fiber for generating and transmitting a flat-top light, which comprises a core and a cladding, and a core inner layer and a high refractive index annular nested core outer layer are arranged inside the core, the high refractive index annular nested core outer layer is composed of 16 two-annular inscribed nested elements, and adjacent two of the nested elements are tangent and the 16 nested elements are all tangent to the core inner layer, the side length of the core inner layer is 2R cor , R cor is the radius of the core inner layer, the outer ring thickness of the two annular of the high refractive index annular nested core outer layer is t or , and the inner ring thickness is t ir .

[0008] Further improvement of the present application is that the wavelength range of the flat-top light beam generated and transmitted by the full solid anti-resonant fiber is 1100-2200nm.

[0009] A further improvement of the present invention is that the outer layer of the high refractive index annular nested fiber core is doped with germanium dioxide, which has a refractive index of 1.48.

[0010] A further improvement of the present invention is that the inner layer of the fiber core is doped with germanium quartz material with a refractive index of 1.46.

[0011] A further improvement of the present invention is that the cladding is made of quartz material with the lowest refractive index of 1.45.

[0012] A further improvement of the present invention is that the side length of the inner layer of the fiber core is 2R. cor It is 17.6 micrometers.

[0013] A further improvement of the present invention is that the outer ring thickness of the high refractive index annular nested fiber core is 110 nanometers and the outer ring radius is 1.9 micrometers.

[0014] A further improvement of the present invention is that the inner ring thickness of the outer layer of the high refractive index annular nested fiber core is 120 nanometers and the inner ring radius is 1.63 micrometers.

[0015] A further improvement of the present invention is that the inner layer of the fiber core has an axisymmetric shape.

[0016] A further improvement of the present invention is that the inner layer of the fiber core is square, circular, hexagonal, or octagonal.

[0017] The beneficial effects of this invention are:

[0018] (1) This invention is the first to apply an anti-resonance structure to a flat-top fiber, which will greatly reduce the constraint loss of the generation and propagation of the flat-top fiber.

[0019] (2) Due to the anti-resonant structure, the constraint loss of the flat-top beam transmitted in the all-solid anti-resonant fiber is very low, and the anti-resonant structure reduces the constraint loss to 10. -13 This is on the order of magnitude, which also helps it to have a larger modal area.

[0020] (3) The non-uniformity (Δ) of the flat-top modal field obtained by the present invention is 0.2%, and the spot side length is 15 micrometers.

[0021] (4) The all-solid-state anti-resonant fiber structure of the present invention is more stable and easier to manufacture. Future special fiber structure designs will focus on this field.

[0022] (5) Low-loss flat-top light can be generated in the 1100nm~2200nm wavelength range. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the cross-section of the all-solid-state anti-resonant optical fiber of the present invention.

[0024] Figure 2 is the full solid anti-resonant fiber core profile of the present invention.

[0025] Figure 3 is the plot of the full solid anti-resonant fiber confinement loss and the uniformity Δ of the flattened mode field as a function of the core inner cladding radius.

[0026] Figure 4 is the refractive index profile of the square core fiber for flattened beam generation, R h is the radius of the core outer layer.

[0027] Figure 5 is the plot of the flattened fiber CL, the uniformity Δ of the flattened mode field as a function of the core refractive index, n core , n doped are the refractive indices of the core inner and outer layer doping respectively.

[0028] Figure 6 is the plot of the flattened fiber CL, the uniformity Δ of the flattened mode field as a function of the inner ring thickness t ir , the outer ring thickness t or .

[0029] Figure 7 is the field distribution of the LP11 mode (a and b) and the LP21 mode (c and d).

[0030] Figure 8 is the mode field pattern.

[0031] Figure 9 is the power flow of the output mode field central axis segment.

[0032] Figure 10 is the plot of the fiber loss for the full solid anti-resonant fiber for bend radii of 10 cm, 8.5 cm and 7 cm.

[0033] Figure 11 is the flattened mode field after bending 8.5 cm at a wavelength of 1600 nm.

[0034] Figure 12 is the plot of the flattened fiber CL as a function of wavelength from 750 nm to 2250 nm.

[0035] Figure 13 is the dispersion property of the fiber.

[0036] Figure 14 is the structure and the output flattened mode field for hexagonal core (a, b), octagonal core (c, d), and circular core (e, f). DETAILED DESCRIPTION

[0037] Embodiments of the present application will be described below with reference to the drawings, in which some practical details are shown in the following description for the purpose of making the present application clear. It should be understood that these practical details are not intended to limit the present application. That is, in some embodiments of the present application, these practical details are not necessary. In addition, for the purpose of simplifying the drawings, some conventional structures and components will be shown in the drawings in a simplified schematic manner.

[0038] As shown in Figures 1-2 , the present application is a full solid anti-resonant optical fiber, which comprises a core and a cladding 1, and a high refractive index annular nested core outer layer 3 is arranged inside the core.

[0039] The core inner layer 2 is a germanium-doped quartz material, and the refractive index is 1.46. The core R cor is 8.8 microns.

[0040] The refractive index of the core inner layer 2 is 1.46, and the refractive index of the high refractive index annular nested core outer layer 3 is 1.48. The refractive index of the core inner layer 2 is lower than that of the core outer layer 3, and the overall refractive index distribution is low-high-low from inside to outside.

[0041] The high refractive index annular nested core outer layer 3 is doped, and the doping medium is germanium dioxide. The core inner layer 2 is doped, and the doping medium is germanium dioxide.

[0042] The high refractive index annular nested core outer layer 3 is composed of 16 two-ring inscribed nested elements, and the adjacent two nested elements are tangent, and the 16 nested elements are tangent to the core inner layer 2. The outer ring thickness of the high refractive index annular nested core outer layer 3 is 110 nanometers, and the outer ring radius is 1.9 microns. The inner ring thickness of the high refractive index annular nested core outer layer 3 is 120 nanometers, and the inner ring radius is 1.63 microns.

[0043] Figure 3 is a diagram of the variation of the full solid anti-resonant optical fiber with the core inner cladding radius. It can be seen from the diagram that when the core inner cladding radius R core = 8.5 μm to 9 μm, the confinement loss and the relative power difference Δ are small, and therefore, the core inner cladding radius Rcore is selected to be 8.8 μm. In order to obtain a flat beam, the refractive index distribution of the optical fiber has a low-high-low requirement.

[0044] Figure 4 is a refractive index distribution of a full solid anti-resonant optical fiber. A low refractive index region is introduced in the core, but its refractive index is higher than that of the cladding. A germanium dioxide-doped annular nested core outer layer forms a high refractive index region to achieve the required refractive index distribution.

[0045] Figure 5 is the CL and Δ with the change of the inner and outer layer refractive index of the core, it can be seen that the inner and outer layer refractive index of the core is selected as 1.46 and 1.48 respectively, and there is a smaller CL and Δ.

[0046] Figure 6 is the CL and Δ with the change of the outer and inner thickness of the cladding tube of the core, the outer and inner thickness is determined as 120 nm and 110 nm. The flat-top optical fiber is a multimode optical fiber, the flat-top mode is the fundamental mode, and the LP11 and LP21 modes are shown in Figure 7 Due to the influence of the square core and the doped layer, they have different degrees of uniformity distortion, and the confinement losses of the LP11 and LP21 modes are about 10 -8 and 10 -7 , respectively, which are larger than that of the fundamental mode.

[0047] At the wavelength of 1550 nm, the output light field is as shown in Figure 8 , the mode field presents a flat-top square column shape, Figure 9 is the intensity distribution along the central axis, and the non-uniformity is as small as 0.2%, and the mode field area is 1699.32 μm 2 . In addition to the above CL, another basic loss of the optical fiber is the bending loss, which reflects the transmission loss when the optical fiber is bent.

[0048] Figure 10 is the loss diagram of the all-solid anti-resonant optical fiber when the bending radius is 10 cm, 8.5 cm and 7 cm. Figure 11 is the flat-top mode field after bending 8.5 cm at the wavelength of 1600 nm, and the flat-top mode field intensity tilts towards the bending direction, but the basic beam profile does not deform. Through actual measurement, it is found that the flat-top light can stably output in the wavelength range of 1200 nm to 2200 nm in Figure 12 .

[0049] As the wavelength becomes shorter, multiple loss peaks appear, the flat-top mode can no longer be transmitted, and the main maximum peak appears at 1100 nm, and the maximum peak decreases with the decrease of the wavelength. The zero dispersion wavelength of the all-solid anti-resonant flat-top optical fiber is near 1650 nm, and the dispersion increases with the increase of the wavelength. At 1550 nm, the communication window can meet the communication demand with a small negative dispersion.

[0050] In the optimization process of the all-solid anti-resonant optical fiber, changing the shape of the core into an axisymmetric shape does not affect the generation and transmission of the flat-top light beam. The reason is that in each direction, the anti-resonant structure can well achieve the purpose of uniformization of the light field. The core is modified to hexagonal, octagonal, circular and equilateral shape, and the results are shown in Figure 14 . A specific shape can produce similar light beam field profiles.

[0051] The anti-resonance fiber of the full solid structure flat-top light beam of the present application is based on the anti-resonance principle, and the stability of the reinforced structure is enhanced, and the manufacturing difficulty is reduced. By changing the structure and parameters of the fiber core, the uniformization output flat-top light of the optical field is realized. The proposed flat-top fiber is a multimode fiber, and the flat-top mode is the basic mode. The transmission limited loss is greatly reduced in 1100-2200nm, and the mode field area is large.

[0052] The above merely describes the embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. An all-solid anti-resonant optical fiber, characterized in that: The full solid anti-resonance optical fiber for generating and transmitting flat-top light comprises a core and a cladding (1), a core inner layer (2) and a high refractive index annular nested core outer layer (3) are arranged inside the core, the high refractive index annular nested core outer layer (3) is composed of 16 two-annular inscribed nested elements, and adjacent two of the nested elements are tangent, and the 16 nested elements are all tangent to the core inner layer (2), the thickness of the outer ring of the two-annular high refractive index annular nested core outer layer (3) is t or , the thickness of the inner ring is t ir , the core inner layer (2) is axially symmetrical, and the core inner layer (2) is square, circular, hexagonal or octagonal.

2. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The full solid anti-resonant fiber can generate and transmit flat-top beams in a wavelength range of 1100-2200 nm.

3. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The high-refractive annular nested core outer layer (3) is doped, and the doping medium is germanium dioxide with a refractive index of 1.

48.

4. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The core inner layer (2) is doped, and the doping medium is germanium quartz material with a refractive index of 1.

46.

5. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The cladding (1) is quartz material with a refractive index of 1.

45.

6. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The edge length 2R of the inner layer (2) of the core cor is 17.6 microns.

7. A solidly mounted anti-resonant optical fiber according to claim 1, wherein: The outer ring of the high-refractive annular nested core outer layer (3) has a thickness of 110 nm and a radius of 1.9 microns.

8. A full solid anti-resonant optical fiber according to claim 1, characterized in that: The inner ring of the high-refractive annular nested core outer layer (3) has a thickness of 120 nm and a radius of 1.63 microns.

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