Anti-resonance hollow-core optical fiber with low polarization mode dispersion

Abstract

The invention provides an anti-resonance hollow-core optical fiber with low polarization mode dispersion, the optical fiber comprises an outer cladding and a fiber core layer, the outer cladding wraps the fiber core layer, the fiber core layer comprises a plurality of optical fiber cores, the plurality of optical fiber cores are uniformly arranged along the circumference of the outer cladding on the cross section of the optical fiber, and the optical fiber adopts a hollow-core optical fiber; and constructing a superposition parameter distribution schematic diagram based on the plurality of optical fiber parameter distribution schematic diagrams, and twisting each optical fiber core of the fiber core layer at each length position of the optical fiber by adopting the twisting rate recorded in the superposition parameter distribution schematic diagram. According to the scheme, superposition of multiple scales can be met, rapid oscillation on a short scale is achieved, slow change on a long scale is achieved, and the polarization state of light propagation is continuously affected by a changing axial stress field; and the long-period modulation further compensates the residual birefringence effect on a larger scale.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and in particular to an anti-resonant hollow optical fiber with low polarization mode dispersion. Background Technology

[0002] As optical communication technology continues to develop towards higher speeds and larger capacities, polarization mode dispersion (PMD) in optical fiber communication links has gradually become one of the important limiting factors affecting system performance. This is especially true in the application of novel hollow-core optical fibers. Due to their unique light-guiding mechanism and microstructure design, hollow-core fibers possess the potential for low loss, low nonlinearity, and high transmission rates. However, during the actual manufacturing process, microstructural asymmetries and random perturbations inevitably occur, leading to high inherent birefringence within the fiber and thus significant polarization mode dispersion, which restricts the further application of hollow-core fibers in long-distance, high-speed optical communication.

[0003] In existing technologies, a common approach to address the PMD (Polarization Mode Dispersion) problem in optical fibers is to apply periodic torsional perturbations along the fiber's length, a technique known as "fiber spin." Existing research and patents demonstrate that applying periodic axial rotation during fiber drawing can effectively reduce polarization mode dispersion within the fiber. For example, in the manufacture of conventional single-mode solid-core optical fibers, constant pitch or single-period spin torsion structures are widely used. This approach can, to some extent, average the birefringence effect within the fiber, thereby significantly reducing the PMD value. However, the aforementioned single-period or constant-period torsion techniques have significant limitations. Specifically, spin structures with constant or single-period helical perturbations can typically only effectively reduce PMD within a specific wavelength or narrow band range. Once deviating from the target wavelength optimized for design, the control effect of this technology on PMD will rapidly decline, thus failing to meet the higher requirements of current broadband high-speed communication systems for fiber optic PMD control. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide an anti-resonant hollow fiber with low polarization mode dispersion to eliminate or improve one or more defects existing in the prior art.

[0005] One aspect of the present invention provides an anti-resonant hollow-core optical fiber with low polarization mode dispersion, the optical fiber comprising an outer cladding and a core layer, the outer cladding enclosing the core layer, the core layer comprising a plurality of optical fiber cores, the plurality of optical fiber cores being uniformly arranged along the circumference of the outer cladding in the cross section of the optical fiber, the optical fiber being a hollow-core optical fiber; A superimposed parameter distribution diagram is constructed based on multiple optical fiber parameter distribution diagrams. At each length position of the optical fiber, each optical fiber core of the core layer is twisted at the twist rate recorded in the superimposed parameter distribution diagram.

[0006] Using the above scheme, the torsional velocities of the optical fiber along its length can be superimposed, satisfying rapid oscillation at one segment scale (determined by a portion of the multiple optical fiber parameter distribution diagrams) and slow variation at a longer scale (determined by another portion of the multiple optical fiber parameter distribution diagrams). This multi-scale perturbation causes the polarization state of light propagation to be continuously affected by the changing axial stress field: short-period torsion disrupts the local coupling relationship of polarization modes, while long-period modulation further compensates for the residual birefringence effect on a larger scale. Simulation analysis shows that this dual-period torsion structure can significantly reduce the PMD of the optical fiber.

[0007] In some embodiments of the present invention, a superimposed parameter distribution diagram is constructed based on multiple optical fiber parameter distribution diagrams. The step of twisting each optical fiber core of the core layer at each length position of the optical fiber using the twist rate recorded in the superimposed parameter distribution diagram includes: Obtain multiple optical fiber parameter distribution diagrams, where the vertical axis of the optical fiber parameter distribution diagrams represents the torsion rate and the horizontal axis represents the optical fiber length position; For the same length position in multiple optical fiber parameter distribution diagrams, the value of the superimposed torsion rate is calculated based on the value of the torsion rate; The superposition parameter distribution diagram is determined based on the superposition torsion rate values ​​at each length position, and the fiber core is twisted based on the superposition parameter distribution diagram.

[0008] In some embodiments of the present invention, in the step of twisting the fiber core based on the superimposed parameter distribution diagram, the twisting rate at each length position of the fiber core is adopted at the corresponding position in the superimposed parameter distribution diagram.

[0009] In some embodiments of the present invention, in the step of calculating the value of the superimposed torsion rate based on the value of the torsion rate at the same length position of multiple optical fiber parameter distribution diagrams, the single torsion rate corresponding to each optical fiber parameter distribution diagram is calculated based on the amplitude and period of each optical fiber parameter distribution diagram, and the value of the superimposed torsion rate is calculated based on the single torsion rate corresponding to each optical fiber parameter distribution diagram.

[0010] In some embodiments of the present invention, in the step of calculating the value of the superimposed torsion rate based on the single torsion rate corresponding to each optical fiber parameter distribution diagram, the superimposed torsion rate is calculated using the following formula: ; in, Indicates the superimposed torsional rate. , and The diagrams represent the single torsion rate at length position z for each fiber parameter distribution.

[0011] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each optical fiber parameter distribution diagram based on the amplitude and period of each optical fiber parameter distribution diagram, if the number of optical fiber parameter distribution diagrams is 2, and both optical fiber parameter distribution diagrams are sine waves, then the direction determination of the torsion rate at the same length position is based on the first algorithm or the second algorithm to calculate the single torsion rate at that length position.

[0012] In some embodiments of the present invention, in the step of calculating the single torsion rate at a length position using a first algorithm or a second algorithm based on the direction determination of the torsion rate at the same length position, if the directions of the torsion rates at the same length position are the same, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. This indicates the period of the sine wave.

[0013] In some embodiments of the present invention, in the step of calculating the single torsion rate at the same length position using a first algorithm or a second algorithm based on the direction determination of the torsion rate at the same length position, if the directions of the torsion rates at the same length position are not the same, the single torsion rate is calculated using the following formula: in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. Indicates the period of the sine wave. The schematic diagram of the parameter distribution of two optical fibers at the location of this length position shows that the directions of the torsion rates are opposite and the total length is opposite.

[0014] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a triangular wave diagram, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. Indicates the amplitude of the triangular wave diagram. This indicates the period of the triangular wave diagram.

[0015] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a sawtooth wave diagram, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. Indicates the amplitude of the sawtooth waveform. This indicates the period of the sawtooth waveform.

[0016] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the text, or may be learned by practice of the invention. The objects and other advantages of the invention will become apparent from the description and the accompanying drawings.

[0017] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, are not intended to limit the scope of the invention.

[0019] Figure 1 This is a schematic diagram of the anti-resonant hollow fiber with low polarization mode dispersion in this scheme. Figure 2 This is a schematic diagram of the fiber core twisting process for the low polarization mode dispersion anti-resonant hollow fiber of this scheme. Figure 3 This is a radial refractive index distribution diagram of one embodiment of the optical fiber in this scheme; Figure 4 This is a schematic diagram showing the structural parameter distribution of one embodiment of the optical fiber in this scheme; Figure 5 This scheme constructs a superimposed parameter distribution diagram based on the two optical fiber parameter distribution diagrams. Figure 6 A schematic diagram illustrating the theoretical mechanism by which this solution reduces PMD in optical fibers; Figure 7 The graph shows a comparison of the PMD performance of the optical fiber in this scheme with that of existing technologies with single-cycle or constant spiral perturbation. Figure 8 This is a waveform diagram illustrating the distribution of different fiber parameters in this scheme. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0021] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0022] The disadvantages of existing technologies include: First, spin structures with constant or single-period spiral perturbations can usually only effectively reduce PMD within a specific wavelength or narrow band range. Once they deviate from the target wavelength optimized by the design, the control effect of this technology on PMD will drop rapidly, thus failing to meet the higher requirements of current broadband high-speed communication systems for fiber optic PMD control. Second, the traditional constant period spin structure or single period perturbation method causes the fiber to accumulate torsional stress in one direction, which makes the fiber prone to internal stress release during long-term operation or laying. This internal stress release will further cause birefringence inhomogeneity, ultimately leading to the degradation of PMD performance. Third, existing spin perturbation schemes generally lack flexible parameter adjustability, making it impossible to flexibly adapt to different fiber structures and application requirements. Especially in the field of hollow fiber, due to the complex and variable structure and mode characteristics, traditional single-period or constant pitch schemes are difficult to meet the requirements of fine and personalized polarization control.

[0023] Therefore, current traditional constant or single-period spin techniques have shortcomings in achieving low PMD broadband transmission, maintaining long-term stability, and providing flexible engineering control in hollow-core optical fibers. How to further reduce the broadband PMD of hollow-core optical fibers while simultaneously avoiding structural instability during long-term use, improving the engineering controllability and flexibility of the fiber manufacturing process, and realizing a new type of hollow-core optical fiber structure suitable for the requirements of future high-speed, high-capacity optical communication systems has become a crucial problem urgently needing to be solved in the field of optical fiber communication.

[0024] like Figure 1 As shown, this invention proposes a low polarization mode dispersion anti-resonant hollow fiber, the fiber comprising an outer cladding and a core layer, the outer cladding wrapping the core layer, the core layer comprising a plurality of fiber cores, the plurality of fiber cores being uniformly arranged along the circumference of the outer cladding in the cross section of the fiber, the fiber being a hollow fiber. A superimposed parameter distribution diagram is constructed based on multiple optical fiber parameter distribution diagrams. At each length position of the optical fiber, each optical fiber core of the core layer is twisted at the twist rate recorded in the superimposed parameter distribution diagram.

[0025] like Figure 2 As shown, in some embodiments of the present invention, a superimposed parameter distribution diagram is constructed based on multiple optical fiber parameter distribution diagrams. The step of twisting each optical fiber core at each length position of the optical fiber using the twist rate recorded in the superimposed parameter distribution diagram includes: Step S100: Obtain multiple optical fiber parameter distribution diagrams, wherein the vertical axis of the optical fiber parameter distribution diagrams is the torsion rate and the horizontal axis is the optical fiber length position. Step S200: For the same length position in multiple optical fiber parameter distribution diagrams, calculate the value of the superimposed torsion rate based on the value of the torsion rate; Step S300: Determine the superposition parameter distribution diagram based on the superposition torsion rate values ​​at each length position, and twist the fiber core based on the superposition parameter distribution diagram.

[0026] Using the above scheme, the twisting velocity of the optical fiber along its length can satisfy rapid oscillation on a segmental scale (determined by a portion of the multiple optical fiber parameter distribution diagrams) and slow variation on a long scale (determined by another portion of the multiple optical fiber parameter distribution diagrams). This multi-scale perturbation causes the polarization state of light propagation to be continuously affected by the changing axial stress field: short-period twisting breaks up the local coupling relationship of polarization modes, while long-period modulation further compensates for the residual birefringence effect on a larger scale. Simulation analysis shows that this dual-period twisting structure can significantly reduce the PMD of the optical fiber.

[0027] In some embodiments of the present invention, in the step of twisting the fiber core based on the superimposed parameter distribution diagram, the twisting rate at each length position of the fiber core is adopted at the corresponding position in the superimposed parameter distribution diagram.

[0028] In some embodiments of the present invention, in the step of calculating the value of the superimposed torsion rate based on the value of the torsion rate at the same length position of multiple optical fiber parameter distribution diagrams, the single torsion rate corresponding to each optical fiber parameter distribution diagram is calculated based on the amplitude and period of each optical fiber parameter distribution diagram, and the value of the superimposed torsion rate is calculated based on the single torsion rate corresponding to each optical fiber parameter distribution diagram.

[0029] like Figure 4 and 5As shown, in some embodiments of the present invention, in the step of calculating the value of the superimposed torsion rate based on the single torsion rate corresponding to each optical fiber parameter distribution diagram, the superimposed torsion rate is calculated using the following formula: ; in, Indicates the superimposed torsional rate. , and The diagrams represent the single torsion rate at length position z for each fiber parameter distribution.

[0030] Using the above scheme, the fiber core has multiple helical twist structures with different periods along its length, that is, multi-period spin twist modulation is applied in the fiber axial direction; the modulation mode of the helical perturbation is not limited to a sine wave form, but contains two or more periodic components with different parameters in spatial frequency, twist amplitude or twist direction, forming a composite helical modulation structure.

[0031] By introducing the aforementioned helical perturbation structure with a composite period along the fiber length, the fiber can average and compensate for polarization mode coupling at multiple spatial scales, significantly reducing polarization mode dispersion (PMD) in the fiber over a wide frequency band and improving the consistency and stability of optical pulse transmission.

[0032] The scope of protection of this invention concerns the structural features of the optical fiber body and does not involve specific manufacturing methods or steps. In other words, this invention is an improvement on the structure of an optical fiber product, which can be achieved using existing optical fiber drawing processes in conjunction with a specific twisting device.

[0033] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each optical fiber parameter distribution diagram based on the amplitude and period of each optical fiber parameter distribution diagram, if the number of optical fiber parameter distribution diagrams is 2, and both optical fiber parameter distribution diagrams are sine waves, then the direction determination of the torsion rate at the same length position is based on the first algorithm or the second algorithm to calculate the single torsion rate at that length position.

[0034] In some embodiments of the present invention, in the step of calculating the single torsion rate at a length position using a first algorithm or a second algorithm based on the direction determination of the torsion rate at the same length position, if the directions of the torsion rates at the same length position are the same, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. This indicates the period of the sine wave.

[0035] Using the above scheme, this method can achieve rapid oscillation on a scale of tens of meters and slow changes on a scale of hundreds of meters. This multi-scale perturbation causes the polarization state of light propagation to be continuously affected by the changing axial stress field: short-period torsion breaks up the local coupling relationship of polarization modes, while long-period modulation further compensates for the residual birefringence effect on a larger scale. Simulation analysis shows that this dual-period torsion structure can significantly reduce the PMD of optical fiber. For example, compared with untwisted hollow fiber, after introducing the above torsion under the same structure, the polarization mode delay difference per kilometer measured in the 1550 nm communication band is greatly reduced, the average PMD value is only one-tenth of the original, and it remains at an ultra-low level in the broadband range of 1520–1580 nm.

[0036] In some embodiments of the present invention, in the step of calculating the single torsion rate at the same length position using a first algorithm or a second algorithm based on the direction determination of the torsion rate at the same length position, if the directions of the torsion rates at the same length position are not the same, the single torsion rate is calculated using the following formula: in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. Indicates the period of the sine wave. The schematic diagram of the parameter distribution of two optical fibers at the location of this length position shows that the directions of the torsion rates are opposite and the total length is opposite.

[0037] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a triangular wave diagram, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. Indicates the amplitude of the triangular wave diagram. This indicates the period of the triangular wave diagram.

[0038] In some embodiments of the present invention, in the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a sawtooth wave diagram, the single torsion rate is calculated using the following formula: ; in, This represents the single torsional rate at length position z. Indicates the amplitude of the sawtooth waveform. This indicates the period of the sawtooth waveform.

[0039] Example 1, such as Figure 5 As shown, the optical fiber is subjected to a dual-period sinusoidal helical torsion perturbation during the drawing process. The optical fiber comprises a hollow fiber core and a cladding layer of anti-resonant tube arrays of the fiber core, as shown... Figure 3 As shown, its cross-section can be a conventional circular symmetrical structure. The optical fiber is twisted axially, resulting in a torsion rate distribution of the following form: Periodic torsion with shorter cycles. For example, the basic torsion cycle is set to... The magnitude refers to the number of times a complete 360° twist is completed every 20 meters of optical fiber (the positive direction is defined as clockwise). The amplitude (torsional rate) of the basic twist can be set as follows: Turns / meters.

[0040] A longer-period torsion modulation is superimposed on the basic torsion. For example, the secondary torsion period is set to... The magnitude refers to the introduction of a slow-changing torsion of a full cycle over a longer axial scale. This secondary perturbation can have an amplitude of The revolutions per meter are superimposed on the fundamental torsion, and its phase causes the overall torsion rate to increase over one length of the fiber and decrease over another length.

[0041] By superimposing the above-mentioned dual-period torsion functions, the superimposed torsion rate TP(z) of the optical fiber can be expressed as a function of the length position z, for example: .in and These correspond to the amplitudes of the two periodic components, and These are their periods. It should be noted that the above formula gives an idealized continuous sine model; in actual manufacturing, equivalent periodic torsional control can also be used.

[0042] In this structure, the twisting velocity of the optical fiber along its length oscillates rapidly on a scale of tens of meters (by...). The decision, and then slowly changed on a scale of hundreds of meters (from...). (Decision). This multi-scale perturbation causes the polarization state of light propagation to be continuously affected by the changing axial stress field: short-period torsion disrupts the local coupling relationship of polarization modes, while long-period modulation further compensates for the residual birefringence effect on a larger scale. Simulation analysis shows that this dual-period torsion structure can significantly reduce the PMD of optical fibers. For example, compared with untwisted hollow fiber, after introducing the above torsion under the same structure, the polarization mode delay difference per kilometer measured in the 1550 nm communication band is greatly reduced, the average PMD value is only one-tenth of the original, and it remains at an ultra-low level in the broadband range of 1520–1580 nm.

[0043] Example 2, wherein the helical perturbation includes a multi-period combination of alternating torsional directions. The basic structure of the optical fiber is similar to that of Example 1, and will not be described again. The torsion rate TP(z) of the optical fiber can be expressed as a function of the length position z. For example: The difference lies in the following twisting pattern: First, within a short period (e.g., the fundamental period) The optical fiber is continuously twisted at a certain angle (meters), and then twisted in the opposite direction at the same angle in the next cycle. This forms a spiral structure with alternating directions: for example, every 10 meters it twists +360°, followed by the next 10 meters twisting -360°, and so on. In this way, the optical fiber completes one "forward and reverse" twisting cycle every 20 meters along its axis.

[0044] Secondly, on a longer periodic scale, variations in the torsional amplitude or period are introduced. For example, each 500 meters is considered a supercycle, and the short period is slightly adjusted within different supercycles. The peak value of the length or torsion angle causes the aforementioned "positive and negative" torsion structures to change slowly over longer distances. This avoids the cumulative effect that a fixed period might cause, resulting in more uniform polarization coupling.

[0045] The alternating twist helps prevent the fiber from being over-tightened in a single direction, while ensuring the balance of average stress. More importantly, the alternating twist itself introduces two perturbations in opposite directions, which can be regarded as a special dual-period component (whose spectrum includes the fundamental frequency and higher harmonic components). When combined with long-period amplitude / frequency modulation, the overall effect is equivalent to including multiple spatial frequency components. Simulation tests show that multi-period hollow fiber with alternating twist has significantly reduced sensitivity to polarization state when subjected to external pressure or temperature changes. Regardless of the polarization direction of the external perturbation, the delay difference caused by birefringence is averaged by the fiber's internal twist, preventing a surge in PMD caused by a perturbation in a specific direction. Therefore, this structure can maintain low PMD performance under environmental changes, improving the stability of the fiber optic link.

[0046] Example 3 illustrates another variation of the structure of the present invention, where the waveform of the helical perturbation is not limited to sine, but uses a non-sine periodic waveform to enhance specific effects, such as... Figure 8 As shown. The instantaneous torsional rate TP(z) of an optical fiber can be expressed as a function of its length and position z, for example, in sine and triangular waves: Or triangular waves and sawtooth waves: During the optical fiber drawing process, a dedicated torsion control program is used to achieve the following torsion function: With long cycle Using a period of 100 meters (for example), the torsional rate is piecewise linearly modulated (sawtooth wave). From the beginning of the period to half its length, the torsional rate is gradually increased, from 0 to its maximum value. In the latter half of the cycle, the torsional rate is rapidly reduced back to 0, and the above cycle is repeated. Thus, The internal structure forms a sawtooth-shaped distribution of torsional velocity.

[0047] At the same time, in a shorter period Small, rapid disturbances can be superimposed on a 5-meter segment, using alternating rectangular or triangular waves. For example, within each 5-meter segment, a fixed rate can be used initially. Twist 2.5 meters, then... A 2.5-meter twist creates a high-frequency, small-amplitude forward and reverse twist. Alternatively, a similar method with a period of 5 meters and an amplitude of... The triangular wave twist achieves continuous and smooth reciprocating rotation.

[0048] This combination achieves a composite helical perturbation of long-period sawtooth waves and short-period square and triangular waves. Sawtooth wave modulation ensures that the average fiber torsion value changes piecewise over ultra-long scales, avoiding the accumulation of small residual birefringence over long distances. Meanwhile, short-period square / triangular waves ensure rapid alternation of polarization states at small scales. These non-sinusoidal waveforms, such as triangular or rectangular waves, often effectively contain the fundamental wave and a series of harmonic components, equivalent to a one-time superposition of multiple frequency perturbations. Therefore, the structure in this embodiment can introduce rich spatial frequency components in the frequency domain, achieving a more comprehensive averaging effect on polarization mode coupling.

[0049] like Figure 7 As shown, under laboratory conditions, the PMD performance of sawtooth + square wave composite twisted hollow fiber and single-period sinusoidal twisted fiber were compared and tested. Polarization mode dispersion (PMD) measurements were performed on a 10 km long sample with a center wavelength of 1550 nm. The results showed that the DGD (time delay difference) distribution of the fiber in this embodiment was significantly more concentrated, and its average PMD value was reduced by more than 50% compared to the single-period sinusoidal twisted fiber. Especially within a wide spectral range (1530–1570 nm), the PMD of the fiber in this embodiment remained below 0.1 ps / √km, while the single-period twisted fiber showed peak values ​​above 0.2 ps / √km at some wavelengths. This demonstrates the superiority of non-sinusoidal multi-period perturbations in broadband PMD suppression, such as... Figure 6 As shown.

[0050] It should be noted that the specific parameters in the above embodiments (e.g., torsion period length of 20 m, 100 m, torsion rate of 2 revolutions / meter, etc.) are only examples and can be optimized and selected according to the fiber type and application requirements. For example, for hollow-core fibers with different structures (such as bandgap type or anti-resonant type), and different transmission distances and wavelength requirements, the frequency combination and amplitude of the helical perturbation can be adjusted. The multiple periods can be a combination of two or more spatial frequency components, and the waveform can be a sine wave, a triangular wave, a rectangular wave, a sawtooth wave, or a combination thereof. It can even form a quasi-random period combination through control algorithms to achieve an effect similar to random perturbation. As long as the characteristic of "containing multiple helical torsion components with different period parameters in the fiber length direction" is met, it falls within the scope of the multi-period helical spin perturbation structure defined in this invention.

[0051] Furthermore, this invention does not limit the specific materials or cross-sectional structure used in the manufacture of hollow-core optical fibers. For example, hollow-core optical fibers can be of the type described in this invention, such as hollow-core photonic bandgap fiber (PCF) or hollow-core anti-resonant fiber (HC-ARF); their common feature is that air (or a low-refractive-index gas) is the primary transmission medium in the core region. Regardless of the type of hollow-core fiber, introducing the multi-period helical perturbation described in this invention into its core and cladding as a whole can reduce polarization mode dispersion. Therefore, this invention has broad applicability and can be combined with current hollow-core optical fiber drawing processes to manufacture the fiber by applying a predetermined twisting mode during the drawing process. Without changing the fiber material and cross-sectional structure, performance improvement is achieved solely through structural design, demonstrating significant practical value.

[0052] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this invention are programs or code segments used to perform the desired tasks. The programs or code segments can be stored in a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[0053] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0054] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the embodiments of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-polarization-mode-dispersion anti-resonant hollow-core optical fiber, characterized in that, The optical fiber includes an outer cladding layer and a core layer. The outer cladding layer wraps around the core layer. The core layer includes multiple optical fiber cores. The multiple optical fiber cores are evenly arranged along the circumference of the outer cladding layer in the cross-section of the optical fiber. The optical fiber is a hollow-core optical fiber. A superimposed parameter distribution diagram is constructed based on multiple optical fiber parameter distribution diagrams. At each length position of the optical fiber, each optical fiber core of the core layer is twisted at the twist rate recorded in the superimposed parameter distribution diagram.

2. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 1, characterized in that, Based on multiple optical fiber parameter distribution diagrams, a superimposed parameter distribution diagram is constructed. The steps for twisting each fiber core of the core layer at various length positions of the optical fiber using the twist rate recorded in the superimposed parameter distribution diagram include: Obtain multiple optical fiber parameter distribution diagrams, where the vertical axis of the optical fiber parameter distribution diagrams represents the torsion rate and the horizontal axis represents the optical fiber length position; For the same length position in multiple optical fiber parameter distribution diagrams, the value of the superimposed torsion rate is calculated based on the value of the torsion rate; The superposition parameter distribution diagram is determined based on the superposition torsion rate values ​​at each length position, and the fiber core is twisted based on the superposition parameter distribution diagram.

3. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 2, characterized in that, In the step of twisting the fiber core based on the superimposed parameter distribution diagram, the twisting rate at each length position of the fiber core is adopted according to the corresponding position in the superimposed parameter distribution diagram.

4. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 2 or 3, characterized in that, In the step of calculating the superimposed torsion rate based on the torsion rate at the same length position for multiple optical fiber parameter distribution diagrams, the single torsion rate corresponding to each optical fiber parameter distribution diagram is calculated based on the amplitude and period of each optical fiber parameter distribution diagram, and the superimposed torsion rate is calculated based on the single torsion rate corresponding to each optical fiber parameter distribution diagram.

5. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 4, characterized in that, In the step of calculating the value of the superimposed torsion rate based on the single torsion rate corresponding to the schematic diagram of each fiber parameter distribution, the superimposed torsion rate is calculated using the following formula: ； in, Indicates the superimposed torsional rate. , and The diagrams represent the single torsion rate at length position z for each fiber parameter distribution.

6. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 4, characterized in that, In the step of calculating the single torsion rate corresponding to each optical fiber parameter distribution diagram based on the amplitude and period of each optical fiber parameter distribution diagram, if the number of optical fiber parameter distribution diagrams is 2, and both optical fiber parameter distribution diagrams are sine waves, then the direction determination of the torsion rate at the same length position is based on the first algorithm or the second algorithm to calculate the single torsion rate at that length position.

7. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 6, characterized in that, In the step of calculating the single torsional rate at the same length position using either the first or second algorithm based on the direction determination of the torsional rate at that position, if the directions of the torsional rates at the same length position are the same, then the single torsional rate is calculated using the following formula: ； in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. This indicates the period of the sine wave.

8. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 6, characterized in that, In the step of determining the direction of the torsional rate at the same length position using either the first or second algorithm to calculate the single torsional rate, if the directions of the torsional rates at the same length position are not the same, the single torsional rate is calculated using the following formula: ； in, This represents the single torsional rate at length position z. This represents the amplitude of the sine wave. Indicates the period of the sine wave. The schematic diagram of the parameter distribution of two optical fibers at the location of this length position shows that the directions of the torsion rates are opposite and the total length is opposite.

9. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 4, characterized in that, In the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a triangular wave diagram, the single torsion rate is calculated using the following formula: ； in, This represents the single torsional rate at length position z. Indicates the amplitude of the triangular wave diagram. This indicates the period of the triangular wave diagram.

10. The low polarization mode dispersion antiresonant hollow-core optical fiber according to claim 4, characterized in that, In the step of calculating the single torsion rate corresponding to each fiber parameter distribution diagram based on the amplitude and period of each fiber parameter distribution diagram, if the fiber parameter distribution diagram is a sawtooth wave diagram, the single torsion rate is calculated using the following formula: ； in, This represents the single torsional rate at length position z. Indicates the amplitude of the sawtooth waveform. This indicates the period of the sawtooth waveform.

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