Negative curvature antiresonant hollow core fiber

Abstract

A negative curvature anti-resonant hollow-core optical fiber, comprising, from outside to inside, an outer cladding, a first capillary layer and a second capillary layer, wherein: a third capillary is respectively arranged in each capillary of the second capillary layer, the first capillary layer as the first anti-resonant layer is composed of a plurality of rotationally symmetrically distributed first capillaries and the outer wall of the first anti-resonant layer is tangent to the inner wall of the outer cladding; the second capillary layer as the second anti-resonant layer is composed of a plurality of rotationally symmetrically distributed second capillaries and the second capillary is only arranged at a single position on the cladding surface of the first anti-resonant layer and connected to the first capillary, the third capillary is connected to the corresponding second capillary, and the first capillary and the second capillary support each other to realize the positioning of the first anti-resonant layer. The present invention provides additional curvature in the cladding of the hollow-core optical fiber by evenly arranging capillaries on the inner surface of the outer ring cladding and using them as a reference, placing a tubular element in the concave area formed by every two capillaries, and simultaneously introducing the second ring of the anti-resonant tube.

Description

Technical Field

[0001] The invention relates to a technology in the field of optical communication technology, in particular to a negative curvature anti-resonance hollow core optical fiber. Background Art

[0002] Conventional solid-core optical fibers, such as step-index optical fibers, use materials with higher refractive indexes for the core and materials with lower refractive indexes for the cladding, so as to guide light through total reflection. Currently, the widely used solid-core optical fibers have intrinsic defects such as nonlinearity of the core adapting to the matrix material, dispersion, photo-induced damage, and UV, mid-infrared and non-transmission of light, which greatly limits their application in certain fields such as communication and data transmission.

[0003] In antiresonant fibers, light in the air is confined to the core by surrounding multiple glass pillars. Since the pillars effectively repel light, scattering losses are usually negligible in antiresonant fibers. Losses in antiresonant fibers are mainly leakage losses. In addition, due to the presence of nodes at the intersections between glass pillars, especially when these nodes have different and multiple thicknesses, stray and spectrally dense resonances are introduced in the antiresonant region, resulting in additional losses. Summary of the invention

[0004] The present invention aims to solve the technical problems that the existing anti-resonance negative curvature hollow-core optical fiber has large limiting loss, the non-contact tube ring structure cannot ensure uniformity, and the multi-layer anti-resonance structure is difficult to prepare. The present invention proposes a negative curvature anti-resonance hollow-core optical fiber. The present invention can provide a mode coupling suppression effect and further reduce the loss of the optical fiber. At the same time, the second ring of the anti-resonance tube is introduced to provide additional curvature in the cladding of the hollow-core optical fiber, thereby improving anti-resonance reflection and ensuring better light confinement in the fiber core.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a negative curvature antiresonant hollow-core optical fiber, which comprises, from the outside to the inside, an outer cladding, a first capillary layer and a second capillary layer, wherein: a third capillary is respectively arranged in each capillary of the second capillary layer, the first capillary layer as a first antiresonant layer is composed of a plurality of rotationally symmetrically distributed first capillaries, and the outer wall of the first antiresonant layer is tangent to the inner wall of the outer cladding; the second capillary layer as a second antiresonant layer is composed of a plurality of rotationally symmetrically distributed second capillaries, and the second capillary is only arranged at a single position on the cladding surface of the first antiresonant layer and connected to the first capillary, and the third capillary is connected to the corresponding second capillary.

[0007] The connection point between the third capillary and the second capillary is specifically where the second capillary is connected to the inner wall of the outer cladding.

[0008] The outer cladding layer, the first capillary layer, the second capillary layer and the third capillary are made of glass, or optionally, made of silicon.

[0009] The present invention relates to a method for preparing the above-mentioned negative curvature antiresonant hollow core optical fiber, comprising the following steps:

[0010] Step 1, capillary drawing: using a glass tube, three capillaries with different radii are drawn respectively;

[0011] Step 2: Preform preparation, specifically including:

[0012] 2.1. n tubular elements are evenly arranged along the inner circumferential direction of the inner wall of the sleeve so that they are spaced apart and do not contact each other, and a first annular mold is inserted from both ends of the sleeve so that the capillary of the first tubular element is fixed between the outer surface of the first mold and the inner surface of the sleeve;

[0013] 2.2. Place n / 2 second tubular element capillaries in the concave area formed by the capillary of the first tubular element, and insert a circular second mold from both ends of the sleeve to fix the second tubular element;

[0014] Step 3: Drawing the preform prepared in step 2, and performing fiber drawing on the intermediate to obtain a negative curvature antiresonant hollow core optical fiber.

[0015] The drawing process described above does not require too many complicated operations at the preform stage after assembly is completed. The stability of the structure can ensure that the structure remains unchanged before the preform enters the drawing furnace. There is no need to perform welding operations before the preform enters the drawing furnace as in other preparation schemes. The heat source stability and manual operation techniques of the welding operation will inevitably cause a certain degree of damage to the uniformity of the preform structure.

[0016] Technical Effects

[0017] The present invention solves the defects of the prior art that loss characteristics and manufacturing complexity cannot be taken into account at the same time, as well as the polarization difference of the optical fiber mode caused by the random and uneven distribution of the non-contact tube ring of the negative curvature hollow-core optical fiber; the present invention arranges capillaries evenly on the inner surface of the outer ring cladding and uses them as a reference to place a tubular element in the concave area formed by every two capillaries to ensure their uniform distribution, thereby significantly improving the performance of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the present invention;

[0019] In the figure: outer cladding 1, first capillary 2, second capillary 3, third capillary 4;

[0020] Figure 2This is the fundamental mode field diagram at 1.55 μm of the present invention;

[0021] Figure 3 This is the mode field diagram of the high-order mode at 1.55 μm of the present invention;

[0022] Figure 4 A curve diagram showing a comparison of fundamental mode and high-order mode losses in an embodiment of the present invention;

[0023] Figure 5 Graph showing fundamental mode loss in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] like Figure 1 As shown, this embodiment relates to a negative curvature antiresonant hollow-core optical fiber, which includes, from the outside to the inside, an outer cladding 1, a first capillary layer and a second capillary layer, wherein: a third capillary 4 is respectively provided in each capillary of the second capillary layer, and the first capillary layer as the first antiresonance layer is composed of a plurality of rotationally symmetrically distributed first capillaries 2, and the outer wall of the first antiresonance layer is tangent to the inner wall of the outer cladding 1; the second capillary layer as the second antiresonance layer is composed of a plurality of rotationally symmetrically distributed second capillaries 3, and the second capillary 3 is only arranged at a single position on the cladding surface of the first antiresonance layer and connected to the first capillary 2, and the third capillary 4 is connected to the corresponding second capillary, and the connection point is the position where the second capillary is connected to the inner wall of the outer cladding.

[0025] The area surrounded by the outer boundary of the second capillary 3 is the core area.

[0026] The first capillary 2 and the second capillary 3 support each other to achieve the positioning of the first anti-resonance layer. By ensuring that the sizes of capillaries of the same type are equal, the support of the capillaries is achieved and the manufacturing difficulty is significantly reduced.

[0027] Preferably, the number of the first capillaries 2 is 12, and the number of the second capillaries 3 and the number of the third capillaries 4 are the same, that is, 6.

[0028] The capillaries corresponding to the first and second anti-resonance layers each have the same cross-sectional size and structure.

[0029] Preferably, the wall thickness of the first, second and third capillaries are all in the range of 0.2-1 μm. The wall thickness of the first capillary and the second capillary are substantially the same, and the wall thickness of the third capillary is slightly different.

[0030] Preferably, the core diameter of the negative curvature antiresonant hollow-core optical fiber is 30-35 μm.

[0031] The radius r of the core region core , the radius r1 of the first capillary and the radius r2 of the second capillary satisfy: r1 / rcore =0.5~0.7, r2 / r core =0.5~0.9.

[0032] Preferably, the core diameter is about 35 μm, the radius of the first capillary and the second capillary is 10 μm, and the capillary wall thickness is 0.5 μm. The radius of the third capillary is 5 μm, and the capillary wall thickness is 0.53 μm. The corresponding limiting loss simulation results are as follows: Figure 2 As shown, it can be seen that the basic loss of the optical fiber is less than 0.12 dB / km when the wavelength is between about 1.3-1.7 μm, and the loss is 0.023 dB / km at 1.55 μm.

[0033] The preparation method of the negative curvature antiresonant hollow core optical fiber is specifically as follows:

[0034] Step 1: Capillary drawing: Use a glass tube to draw three capillaries with different radii.

[0035] Step 2: Preform preparation, specifically including:

[0036] 2.1. n tubular elements are evenly arranged along the inner circumferential direction of the inner wall of the sleeve so that they are spaced apart and do not contact each other, and a first annular mold is inserted from both ends of the sleeve so that the capillary of the first tubular element is fixed between the outer surface of the first mold and the inner surface of the sleeve;

[0037] 2.2. Place n / 2 second tubular element capillaries in the concave area formed by the capillary of the first tubular element, and insert a circular second mold from both ends of the sleeve to fix the second tubular element;

[0038] 2.3. Nest the third tubular element capillary in the second tubular element capillary in the same manner;

[0039] One end of the first, second and third tubular elements is sealed and the sealed ends of all tubular elements are located on the same side;

[0040] The annular mold is preferably a round tube with a length of 10-50 mm, extending into both ends of the inner part of the sleeve, so that the capillary is located between the outer surface of the mold and the inner surface of the sleeve;

[0041] Step 3, drawing the preform prepared in step 2, and performing optical fiber drawing on the intermediate to obtain a negative curvature hollow-core optical fiber;

[0042] The present invention arranges capillaries uniformly on the inner surface of the outer ring cladding, and uses it as a reference, and places a tubular element in the concave area formed by every two capillaries to ensure uniform distribution, thereby avoiding the polarization difference of the optical fiber mode caused by the random uneven distribution of the non-contact tube of the negative curvature hollow-core optical fiber. It can also provide the effect of suppressing mode coupling, further reducing the loss of the optical fiber, and at the same time, the second ring of the anti-resonance tube introduced provides additional curvature in the cladding of the hollow-core optical fiber, improves the anti-resonance reflection, and ensures better light confinement in the core.

[0043] Compared with the prior art, this method reduces manufacturing complexity and at the same time, the loss of the negative curvature hollow core optical fiber at 1.55um is 0.017dB / km.

[0044] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for realizing negative curvature antiresonant hollow core optical fiber, characterized in that: include: Step 1, capillary drawing: using a glass tube, three capillaries with different radii are drawn respectively; Step 2: Preform preparation, specifically including: 2.

1. n tubular elements are evenly arranged along the inner circumferential direction of the inner wall of the sleeve so that they are spaced apart and do not contact each other, and a first annular mold is inserted from both ends of the sleeve so that the capillary of the first tubular element is fixed between the outer surface of the first mold and the inner surface of the sleeve; 2.

2. Place n / 2 second tubular element capillaries in the concave area formed by the capillary of the first tubular element, and insert a circular second mold from both ends of the sleeve to fix the second tubular element; 2.

3. Nest the third tubular element capillary in the second tubular element capillary in the same manner; Step 3, drawing the preform prepared in step 2, and performing optical fiber drawing on the intermediate to obtain a negative curvature antiresonant hollow core optical fiber; The negative curvature antiresonant hollow-core optical fiber comprises, from outside to inside, an outer cladding, a first capillary layer and a second capillary layer, wherein: a third capillary is respectively arranged in each capillary of the second capillary layer, the first capillary layer as the first antiresonant layer is composed of a plurality of rotationally symmetrically distributed first capillaries, and the outer wall of the first antiresonant layer is tangent to the inner wall of the outer cladding; the second capillary layer as the second antiresonant layer is composed of a plurality of rotationally symmetrically distributed second capillaries, and the second capillary is only arranged at a single position on the cladding surface of the first antiresonant layer and connected to the first capillary, the third capillary is connected to the corresponding second capillary, and the first capillary and the second capillary support each other to realize the positioning of the first antiresonant layer; The radius of the core region , the radius of the first capillary and the radius of the second capillary Respectively meet: , .

2. The method for realizing negative curvature antiresonant hollow core optical fiber according to claim 1, characterized in that: The connection point between the third capillary and the second capillary is specifically where the second capillary is connected to the inner wall of the outer cladding.

3. The method for realizing negative curvature antiresonant hollow core optical fiber according to claim 1, characterized in that: The outer cladding layer, the first capillary layer, the second capillary layer and the third capillary are made of glass.

4. The method for realizing negative curvature antiresonant hollow core optical fiber according to claim 1, characterized in that: The wall thickness of the first, second and third capillaries are all in the range of 0.2-1 μm.

5. The method for realizing negative curvature antiresonant hollow core optical fiber according to claim 1, characterized in that: The core diameter of the negative curvature antiresonant hollow core optical fiber is 30-35 μm.

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