Anti-resonance hollow-core optical fiber with special-shaped structure
Patent Information
- Application Number
- CN202511268359.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-05
- Publication Date
- 2025-10-17
AI Technical Summary
Existing anti-resonant hollow fiber relies on nested structures in terms of shape design. Multi-core fiber has a simple structure and insufficient space for loss optimization, resulting in high transmission loss.
An irregular structure is constructed by using multiple sets of first anti-resonant microstructures and multiple second anti-resonant microstructures to disrupt the phase matching between the core and cladding mode fields. Ultra-low transmission loss is achieved through non-nested design, and low loss is maintained over a wide spectrum.
It achieves ultra-low transmission loss of less than 0.015 dB/km in the 1.55 μm band and maintains a loss of less than 1 dB/km in the 1.35–1.65 μm wide spectrum range, which broadens the effective scheme for structural design and increases the theoretical transmission capacity to N times that of a single-core fiber.
Smart Images
Figure CN120802423A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of optical fiber technology, in particular to a heteromorphic structure of a hollow-core anti-resonant fiber. BACKGROUND
[0002] Hollow-core fiber is an optical fiber that confines optical power in an air core, which can effectively avoid the inherent nonlinear effects, dispersion and material absorption loss of quartz material. It is mainly divided into two categories: hollow-core photonic bandgap fiber and hollow-core anti-resonant fiber (HC-ARF).
[0003] The working principle of HC-ARF relies on the anti-resonant effect, which suppresses the coupling between the cladding modes and the core modes, and confines most of the optical power in the air core for transmission. Compared with the photonic bandgap fiber, the cladding structure of HC-ARF is simpler and more flexible, and is not strictly limited by the photonic bandgap effect. By reasonably designing the cladding structure and the fiber size, HC-ARF can realize low-loss transmission in a wide wavelength band from ultraviolet to terahertz. This kind of fiber significantly reduces the energy coupling of the mode field and the medium interface through the coherent cancellation effect of the leaky waveguide produced by the thickness of the specific microstructure ring, which can theoretically achieve the loss limit beyond the traditional quartz optical fiber.
[0004] Although the HC-ARF technology continues to develop, there are still some spaces and technical defects to be optimized. Mainly reflected in:
[0005] Dependence on nested structure: The existing low-loss anti-resonant hollow-core fiber usually depends on the nested structure to reduce the loss, but there is still a considerable gap in the shape design.
[0006] Single structure of multi-core optical fiber: The current multi-core hollow-core fiber design often relies on a simple periodic structure.
[0007] Loss optimization space: Fiber loss is a key challenge for HC-ARF technology. Although this technology can theoretically achieve a loss limit beyond traditional quartz optical fiber, the transmission loss of the existing structure design is still high. SUMMARY
[0008] In view of the problems existing in the prior art, the present application provides a heteromorphic structure of a hollow-core anti-resonant fiber, comprising:
[0009] A plurality of first anti-resonant microstructures, the open end of the first anti-resonant microstructure is connected with the inner wall of the outer cladding and forms a microstructure closed cavity, and the closed end of all the first anti-resonant microstructures is directed to the center of the outer cladding and surrounds a core region;
[0010] a plurality of second anti-resonant microstructures, each connected to the inner wall of the outer cladding, and at least one of the second anti-resonant microstructures is arranged between two adjacent first anti-resonant microstructures to form a special-shaped structure.
[0011] Preferably, the first anti-resonant microstructures are uniformly and equidistantly distributed along the circumferential direction of the inner wall of the outer cladding.
[0012] Preferably, the number of the second anti-resonant microstructures is twice that of the first anti-resonant microstructures, and two second anti-resonant microstructures are arranged between two adjacent first anti-resonant microstructures.
[0013] And the two second anti-resonant microstructures are symmetrically distributed along the center symmetry line of the adjacent first anti-resonant microstructures.
[0014] Preferably, each of the first anti-resonant microstructures comprises two mirror-symmetric half-outer arcs, and the half-outer arcs comprise a first circular arc, a second circular arc and a third circular arc connected in turn from the core area to the inner wall of the outer cladding.
[0015] The curvatures of the third circular arcs of the two half-outer arcs are opposite.
[0016] Preferably, the first circular arc and the second circular arc are tangent and inscribed.
[0017] Preferably, the second circular arc and the third circular arc are tangent and inscribed with opposite curvature directions.
[0018] Preferably, the wall thickness of the first anti-resonant microstructure is uniform.
[0019] Preferably, the wall thickness of the second anti-resonant microstructure is uniform.
[0020] Preferably, the second anti-resonant microstructure is circular, or arc, or elliptical.
[0021] The above technical solution has the following advantages or beneficial effects:
[0022] 1. The second anti-resonant microstructure in the application is arranged between the first anti-resonant microstructures to form a non-nested special-shaped structure, which destroys the phase matching of the core and the cladding mode field through the design of the non-nested special-shaped structure, realizes ultra-low transmission loss, and maintains low loss in a wide spectrum range.
[0023] 2. In the application, every two adjacent first microstructures and the second microstructure between them jointly form a new waveguide core, which is not a simple cascade of traditional fundamental mode space, but a physical integration realized through microstructure topology innovation, which can reduce the mode field transmission loss. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1FIG1 is a schematic diagram of the end face structure of an antiresonant hollow-core optical fiber with a special-shaped structure in a preferred embodiment of the present invention;
[0025] Figure 2 FIG1 is an enlarged schematic diagram of a first antiresonant microstructure of an antiresonant hollow-core optical fiber with a special-shaped structure in a preferred embodiment of the present invention;
[0026] Figure 3 The figure is a loss spectrum curve of an antiresonant hollow-core optical fiber with a special-shaped structure in a preferred embodiment of the present invention;
[0027] Figure 4 FIG1 is a schematic diagram of an end face structure in a preferred embodiment of the present invention when the second anti-resonance microstructure is not added between the first anti-resonance microstructures;
[0028] Figure 5 1 is a loss spectrum in a preferred embodiment of the present invention when the second anti-resonant microstructure is not added between the first anti-resonant microstructures;
[0029] Figure 6 This is the waveguide condition corresponding to the fundamental mode of the low-loss antiresonant hollow-core optical fiber in the 1.55 μm band in a preferred embodiment of the present invention;
[0030] Figure 7 This is the waveguide condition corresponding to the gap region mode of the low-loss antiresonant hollow-core optical fiber in the 1.55 μm band in a preferred embodiment of the present invention;
[0031] Figure 8 This is a loss spectrum curve in the 1.2-1.9 μm band in a preferred embodiment of the present invention;
[0032] Figure 9 for Figure 7 A partial magnified view of the shield-shaped waveguide;
[0033] Figure 10 In a preferred embodiment of the present invention, the loss spectrum of the shield-shaped waveguide in the 1.55 μm band as the loss changes with the radius of the second microstructure closed cavity;
[0034] Figure 11 is a schematic diagram of the end face structure when the shape of the second anti-resonant microstructure is an arc;
[0035] Figure 12 Schematic diagram of the end face structure when the shape of the second anti-resonance microstructure is an ellipse. DETAILED DESCRIPTION
[0036] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.
[0037] In the preferred embodiment of the present application, based on the above-mentioned problems existing in the prior art, a special-shaped structure of the anti-resonant hollow core fiber is provided, as shown in the accompanying drawings, comprising: Figure 1
[0038] A plurality of first anti-resonant microstructures 1, the opening end of the first anti-resonant microstructure 1 is connected with the inner wall of the outer cladding 3 and forms a first microstructure closed cavity 10, and the closed end of all the first anti-resonant microstructures 1 is directed to the center of the outer cladding 3 and surrounds the core area 4;
[0039] A plurality of second anti-resonant microstructures 2, each second anti-resonant microstructure 2 forms a second microstructure closed cavity 20 and is connected with the inner wall of the outer cladding 3, and at least one second anti-resonant microstructure 2 is arranged between adjacent first anti-resonant microstructures 1 to form a special-shaped structure.
[0040] Specifically, in the embodiment, the second anti-resonant microstructure 2 is arranged between the first anti-resonant microstructures 1 to form a non-nested special-shaped structure, the phase matching of the core and the cladding mode is destroyed by the non-nested special-shaped structure design, the ultra-low transmission loss (typical value is less than 0.015 dB / km) is realized in the 1.55 μm wave band, and the loss is kept below 1 dB / km in the 1.35-1.65 μm wide spectrum range, which widens the effective scheme of the structure design;
[0041] Further, because the second anti-resonant microstructure 2 is arranged between the adjacent first anti-resonant microstructures 1, the energy leakage at the gap of the adjacent first anti-resonant microstructures 1 is effectively suppressed, and the fiber loss is further reduced by one order of magnitude;
[0042] Each pair of adjacent first anti-resonant microstructures 1 (N) and the second anti-resonant microstructure 2 therebetween form an independent waveguide core, and naturally form a multicore multiplexing structure with the central core area 4, and the theoretical transmission capacity is increased to N times of that of a single-core fiber.
[0043] In the preferred embodiment of the present application, as shown in the accompanying drawings, the first anti-resonant microstructures 1 are uniformly and equidistantly distributed along the inner wall of the outer cladding in the circumferential direction. Figure 1
[0044] In the preferred embodiment of the present application, the number of the second anti-resonant microstructures 2 is twice that of the first anti-resonant microstructures, and two second anti-resonant microstructures 2 are arranged between the adjacent first anti-resonant microstructures 1;
[0045] And the two second anti-resonant microstructures 2 are symmetrically distributed along the center symmetry line A of the adjacent first anti-resonant microstructures 1.
[0046] Specifically, in the embodiment, as shown in the accompanying drawings, Figure 1 The anti-resonance hollow optical fiber of the present application comprises an outer cladding, 6 groups of first anti-resonance microstructures connected to the inner wall of the outer cladding, and 12 groups of second anti-resonance microstructures arranged between the first anti-resonance microstructures; the center of the outer cladding is surrounded by the 6 groups of first anti-resonance microstructures to form a core area 4.
[0047] The outer cladding 3 in the embodiment is preferably a circular outer cladding tube.
[0048] The diameter of the core area 4 in the embodiment is set to 30 times the wavelength of the communication waveband ( Figure 1 ), and this size design significantly reduces the number of reflections and energy leakage probability of the optical signal in unit transmission distance by expanding the equivalent cross-sectional area of the optical wave transmission.
[0049] In the preferred embodiment of the present application, as shown in Figure 2 , each first anti-resonance microstructure 1 comprises two mirror-symmetrical half-outer arcs, and the half-outer arcs comprise a first circular arc 11, a second circular arc 12 and a third circular arc 13 connected in turn from the core area to the inner wall of the outer cladding;
[0050] The curvatures of the third circular arcs 13 of the two half-outer arcs are opposite.
[0051] In the preferred embodiment of the present application, the first circular arc 11 and the second circular arc 12 are tangent to each other. The tangent line is shown by the dotted line in Figure 2 .
[0052] In the preferred embodiment of the present application, the second circular arc 12 and the third circular arc 13 are tangent to each other with opposite curvature directions. The tangent line is shown by the dotted line in Figure 2 .
[0053] In the preferred embodiment of the present application, the wall thickness of the first anti-resonance microstructure 1 is equal everywhere.
[0054] In the preferred embodiment of the present application, the wall thickness of the second anti-resonance microstructure 2 is equal everywhere.
[0055] Specifically, the first anti-resonance microstructure 1 is composed of three continuous circular arcs (see the specific geometric relationship in Figure 2 ), which are defined in turn as the first circular arc 11, the second circular arc 12 and the third circular arc 13 from the core area 4 to the outer cladding 3.
[0056] Furthermore, none of the three arcs intersect and all remain within a reasonable spatial range. The geometric parameters of each arc have been precisely optimized: the central angle of the first arc 11 is approximately 94°, with the ratio of its arc length (in micrometers) to its central angle (in degrees) controlled within the range of 0.13 to 0.16; the central angle of the second arc 12 is approximately 3.6°, with the ratio of its arc length to its central angle ranging from 10.5 to 11.5; and the central angle of the third arc 13 is approximately 45°, with the ratio of its arc length to its central angle limited to between 0.26 and 0.3.
[0057] Key geometric constraints such as Figure 2 As shown, the first arc 11 and the second arc 12 are in an inward tangent relationship; the second arc 12 and the third arc 13 are inward tangent with opposite curvature directions. All arcs are strictly prevented from intersecting in the spatial arrangement and are constrained within a preset boundary range.
[0058] The first antiresonant microstructure 1 is composed of multiple smooth arc segments connected together, with a constant wall thickness. A mirror-symmetric operation is used to extend the semi-circular arc (the first arc 11, the second arc 12, and the third arc 13 on a single side) into the first antiresonant microstructure 1. This structure, together with the outer cladding, forms a microstructured closed cavity. A specific air gap is maintained between adjacent microstructured closed cavities to ensure optical isolation.
[0059] like Figure 1 As shown, the complete optical fiber cross section is composed of six of the above-mentioned first antiresonant microstructures 1 and twelve second antiresonant microstructures 2, and exhibits bidirectional symmetry characteristics along the x-axis and the y-axis at a specified placement angle.
[0060] The technical effect of this embodiment has been verified experimentally: the circular core region 4 formed by the special-shaped structure achieves an ultra-low transmission loss of 0.0148dB / km in the 1.5μm communication band. This provides a new design paradigm for non-nested antiresonant optical fibers.
[0061] The traditional nested structure relies on nested rings to reduce the power of the core light field flowing out of the boundary along the radial direction through the microstructure ring to suppress leakage loss; while this scheme uses the special-shaped arc (first anti-resonant microstructure 1) design ( Figure 1 ) compresses the mode field distribution within the microstructure, effectively destroying the phase matching condition between the core mode field and the microstructure mode field, thereby suppressing the leakage loss along the line connecting the center of the core to the center of the nearest microstructure arc. Figure 3 , which is the loss spectrum curve of the antiresonant hollow-core optical fiber in this embodiment.
[0062] Furthermore, the first arc closest to the fiber core adopts an optimized curvature radius, forming a moderate negative curvature rather than an extreme bending shape. This design reduces power loss at the node while ensuring the stability of long-distance transmission.
[0063] Meanwhile, the introduction of the proper second micro-structure enclosed cavity 20 (formed by the second anti-resonant micro-structure 2) can effectively reduce the coupling degree between the core mode and the mode at the gap, limit the power loss from the gap, and thus provide new possibilities for the non-nested structure design of the low-loss anti-resonant hollow optical fiber.
[0064] To evaluate the inhibitory mechanism of the second micro-structure enclosed cavity 20 in the process of optical wave transmission for limiting loss, the embodiment is verified by comparison simulation. As shown in Figure 4 , the second anti-resonant micro-structure 2 is removed to obtain a simplified profiled structure optical fiber for optical property analysis.
[0065] The specific simulation result data are shown in Figure 5 , which shows the loss spectrum of the 1.2-1.8 μm band. When the micro-structure wall thickness is constant at 1.13 μm, the optical fiber loss in the 1.45-1.65 μm wavelength range is less than 1 dB / km. Especially in the 1.55 μm communication band, a low-loss transmission performance of 0.109 dB / km is achieved, proving that the basic structure has excellent light guiding ability.
[0066] The above results show that the profiled structure optical fiber composed of only six groups of first micro-structure enclosed cavities 10 can still maintain high-efficiency light guiding characteristics.
[0067] However, the energy leakage at the gap between adjacent first anti-resonant micro-structures 1 becomes the main source of limiting loss. As shown in Figure 6 , after the introduction of twelve groups of second micro-structure enclosed cavities 20, the cladding structure formed thereby effectively suppresses the gap leakage effect, and the minimum limiting loss is further reduced by an order of magnitude based on the original basic structure.
[0068] Figure 6 Meanwhile, the fundamental mode waveguide field distribution of the profiled anti-resonant hollow optical fiber with complete first micro-structure enclosed cavities 10 and second micro-structure enclosed cavities 20 at the 1.55 μm band is shown. The fundamental mode field presents a hexagonal feature close to a circle, indicating that the optical field is well confined in the core.
[0069] The innovative extension of the embodiment is that every two adjacent first micro-structure enclosed cavities 10 and the two second micro-structure enclosed cavities 20 therebetween jointly constitute a new type of waveguide core. As shown in Figure 7 , such a waveguide core also has low-loss transmission characteristics due to the optimized design of the boundary second micro-structure enclosed cavities.
[0070] Specifically, Figure 7 , the mode field distribution of the new type of waveguide is shown, which presents a unique "shield-shaped" geometry.
[0071] Figure 8Further, the simulation loss curve of the shield-shaped waveguide in the 1.2-1.9 μm waveband is given, which proves that the shield-shaped waveguide has excellent transmission performance with the loss less than 1 dB / km in the 1.35-1.65 μm waveband.
[0072] It can be seen that the shield-shaped waveguide can form a seven-core multiplexing structure together with the central fundamental mode waveguide, and the theoretical transmission capacity can reach 7 times of that of a single-core optical fiber. The wide-spectrum low-loss characteristics of the two types of waveguides make the optical fiber particularly suitable for space division multiplexing systems, which significantly reduces the unit bit transmission cost.
[0073] It can be seen that the multi-core structure is not a simple cascade of traditional fundamental mode spaces, but a physical integration realized by microstructure topology innovation.
[0074] To explore the influence of the size of the second microstructure closed cavity on the multi-core mode field loss, the geometric parameters of the first microstructure closed cavity are fixed, and only the inner ring radius of the second microstructure closed cavity (defined as "Radius" parameter in Figure 9 ) is adjusted. The simulated transmission loss is shown in Figure 10 The simulation results show that when the Radius value is 22 μm, the shield-shaped multi-core mode field transmission loss can be as low as 0.168 dB / km in the 1550 nm working waveband, which verifies the feasibility of the structure parameter optimization.
[0075] In the preferred embodiment of the present application, the second anti-resonant microstructure is circular, or arcuate, or elliptical.
[0076] Further, the second anti-resonant microstructure in the present application can be circular as shown in Figure 1 , arcuate as shown in Figure 10 , and elliptical as shown in Figure 10 , all of which can achieve the same technical effects
[0077] The above is only the preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application. For those skilled in the art, it should be realized that any equivalent replacement and obvious changes made by using the contents of the present application and drawings should be included in the protection scope of the present application.
Claims
1. An antiresonant hollow-core optical fiber with a special-shaped structure, characterized in that: include: multiple groups of first anti-resonant microstructures, wherein open ends of the first anti-resonant microstructures are connected to the inner wall of the outer cladding to form a first microstructure closed cavity, and the closed ends of all the first anti-resonant microstructures face the center of the outer cladding and surround a core region; A plurality of second anti-resonance microstructures are provided, each of which forms a second microstructure closed cavity and is connected to the inner wall of the outer cladding. At least one second anti-resonance microstructure is provided between adjacent first anti-resonance microstructures to form a special-shaped structure.
2. The antiresonant hollow core optical fiber according to claim 1, wherein: The first anti-resonance microstructures are evenly and equidistantly distributed along the inner wall of the outer cladding in a circumferential direction.
3. The antiresonant hollow core optical fiber according to claim 1, wherein: The number of the second anti-resonance microstructures is twice that of the first anti-resonance microstructures, and two second anti-resonance microstructures are provided between adjacent first anti-resonance microstructures; Furthermore, the two second anti-resonance microstructures are symmetrically distributed along the central symmetry line of the adjacent first anti-resonance microstructures.
4. The antiresonant hollow core optical fiber according to claim 1, wherein: Each of the first antiresonant microstructures includes two mirror-symmetrical half outer arcs, each of the half outer arcs including a first arc, a second arc, and a third arc sequentially connected from the core region to the inner wall of the outer cladding; The curvatures of the third circular arcs of the two semi-outer arcs are opposite.
5. The antiresonant hollow core optical fiber according to claim 4, wherein: The first circular arc and the second circular arc are inscribed and tangent to each other.
6. The antiresonant hollow core optical fiber according to claim 4, wherein: The second arc segment and the third arc segment are inscribed in each other with opposite curvature directions.
7. The antiresonant hollow-core optical fiber according to claim 1, wherein: The wall thickness of the first anti-resonance microstructure is equal everywhere.
8. The antiresonant hollow core optical fiber according to claim 1, wherein: The wall thickness of the second anti-resonant microstructure is equal everywhere.
9. The antiresonant hollow core optical fiber according to claim 1, wherein: The second anti-resonance microstructure is circular, or arc-shaped, or elliptical.