An anti-resonant hollow core optical fiber, a method for determining structural parameters of the same, and an optical communication system

Abstract

The application discloses a kind of anti-resonant hollow optical fiber and its structural parameter determination method, optical communication system;The anti-resonant hollow optical fiber includes: outer sleeve, and air core and cladding located in the outer sleeve, the cladding is arranged around the air core;The cladding contains one or more anti-resonant components, wherein one or more anti-resonant components in the cladding satisfy: the dispersion-loss merit factor of the anti-resonant hollow optical fiber at working wavelength is greater than the first threshold value, the dispersion-loss merit factor is related to the dispersion coefficient and transmission loss coefficient of the anti-resonant hollow optical fiber.By cladding structure design, the application realizes the decoupling of dispersion and loss at resonance wavelength, can obtain high dispersion compensation with lower loss cost, and is suitable for dispersion management of long-distance, large-capacity optical communication system.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication technology, and in particular to an anti-resonant hollow optical fiber and a method for determining its structural parameters, as well as an optical communication system. Background Technology

[0002] With the rapid development of the Internet, cloud computing, and 5G / 6G mobile communication technologies, modern optical communication systems are evolving towards ultra-high speeds (such as 800Gbps, 1.6Tbps and above), ultra-large capacity, and ultra-long-distance transmission. Against this backdrop, signal impairment problems in fiber optic links have become particularly prominent, with dispersion being one of the key factors limiting system performance.

[0003] Dispersion refers to the phenomenon where different frequency (or wavelength) components of an optical signal travel at different speeds in an optical fiber, causing the pulse to broaden in the time domain. This broadening can cause intersymbol interference, severely degrading signal quality, increasing the bit error rate, and thus limiting transmission distance and speed.

[0004] However, existing dispersion compensation technologies all have shortcomings, making it difficult to achieve an ideal balance in multiple dimensions such as high performance (large bandwidth, high flatness), low loss, high integration, high stability, and low manufacturing cost. Summary of the Invention

[0005] To address the aforementioned technical problems, embodiments of this application provide an anti-resonant hollow optical fiber and a method for determining its structural parameters, as well as an optical communication system.

[0006] The anti-resonant hollow fiber provided in this application embodiment includes: an outer tube, an air core and a cladding located inside the outer tube, wherein the cladding is disposed around the air core; The cladding includes one or more anti-resonant components, wherein the one or more anti-resonant components in the cladding satisfy the following: the dispersion-loss figure of merit F of the anti-resonant hollow fiber at the target operating wavelength is greater than a first threshold value, F = |D| / α, where D is the dispersion coefficient and α is the transmission loss coefficient.

[0007] In some embodiments, the anti-resonance component is a single-layer ring tube; The cladding comprises a ring-shaped tube; or... The cladding comprises multiple layers of annular tubes.

[0008] In some embodiments, the annular tube has a non-circular cross-section.

[0009] In some embodiments, the annular tube has a gradually varying wall thickness distribution.

[0010] In some embodiments, the gradient wall thickness distribution satisfies the following condition: the product of the refractive index and wall thickness of the annular tube facing the air core region is less than the product of the refractive index and wall thickness of the annular tube away from the air core region.

[0011] In some embodiments, the cladding comprises multiple annular tubes, at least two of which have one or more of the following characteristics: Different wall thickness distributions; The product of different refractive indices and wall thickness distributions; Different arrangements of the annular tubes.

[0012] In some embodiments, the multilayer annular tube has a nested structure, wherein the wall thickness, or the product of the refractive index and the wall thickness, of the annular tubes located in different layers varies non-monotonically along the radial direction.

[0013] In some embodiments, the annular tube is at least one of quartz glass, doped glass, soft glass, or polymer material.

[0014] In some embodiments, the target operating wavelength is set within a preset range near the structural resonant wavelength of the anti-resonant component, for generating dispersion at the resonant wavelength for dispersion compensation.

[0015] In some embodiments, the dispersion-loss figure of merit is:

[0016] in, The figure of merit is the dispersion-loss coefficient. The dispersion coefficient is... The transmission loss coefficient α is the value of the fiber core fundamental mode (LP01 mode) measured at the target operating wavelength under standard test conditions using the cut-back method or a standard loss coefficient test method with equivalent effect, expressed in dB / km. During measurement, the optical fiber should be kept straight without macrobending, and the ambient temperature should be controlled at 23±2℃. Furthermore, in some embodiments, the dispersion-loss figure of merit F can also be equivalently represented as the reciprocal of the quality factor Q, or as the normalized dispersion efficiency parameter η = D × A_eff / α, where A_eff is the effective mode field area. Those skilled in the art should understand that regardless of the mathematical transformation used, as long as its physical essence represents the amount of dispersion compensation obtained per unit loss cost, it should be considered to fall within the protection scope of this application.

[0017] In some implementations, the first threshold value is 20 ps / (nm·dB).

[0018] In some embodiments, the cladding is configured to introduce a mode coupling suppression mechanism at the target operating wavelength through structural asymmetry to reduce leakage losses associated with dispersive resonance peaks. In some embodiments, the cladding decouples dispersion-related resonance effects and loss-related leakage channels spectrally by introducing at least two radially distributed anti-resonant interfaces with different structural parameters.

[0019] The optical communication system provided in this application includes an anti-resonant hollow fiber as described above for dispersion compensation.

[0020] The method for determining the structural parameters of anti-resonant hollow optical fiber provided in this application includes: The structural parameters of one or more anti-resonant components in the cladding are optimized with the goal of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength.

[0021] In some implementations, optimizing the structural parameters of one or more anti-resonant components in the cladding with the goal of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength includes: S1. Based on the target operating wavelength and the required dispersion compensation, select the fundamental frequency resonance order of the anti-resonance component, and preliminarily determine the range of values ​​for the wall thickness of the annular tube in the anti-resonance component, so that the target operating wavelength is located in the preset slope region of the short-wave side or long-wave side of the corresponding resonance peak. S2. Determine the structural parameters of the cladding. By adjusting the structural parameters, regulate the imaginary part of the effective refractive index of the leakage mode, so that the transmission loss coefficient is reduced while keeping the change of the dispersion coefficient within the preset range. S3. When the cladding adopts a nested structure of multiple ring tubes, the wall thickness combination of each ring tube is determined in sequence so that the resonant wavelength and the anti-resonant wavelength form a spectral overlap, thereby generating destructive interference at the target working wavelength; the wall thickness combination includes the inner wall thickness and the outer wall thickness. S4. Verify the dispersion-loss figure of merit through numerical simulation. If the dispersion-loss figure of merit is less than or equal to the first threshold, return to S2 to adjust the structural parameters until the dispersion-loss figure of merit is greater than the first threshold.

[0022] In some embodiments, the structural parameters of the cladding include at least one or more of the following: the ellipticity of the annular tube, and the wall thickness gradient factor of the annular tube; the wall thickness gradient factor is related to the maximum wall thickness and the minimum wall thickness.

[0023] In some embodiments, the method further includes: The target operating wavelength is determined and set within a preset range near the structural resonant wavelength of the anti-resonant component.

[0024] In the technical solution of this application embodiment, the anti-resonant hollow fiber includes: an outer tube, an air core and a cladding located inside the outer tube. The cladding surrounds the air core and contains one or more anti-resonant components. The one or more anti-resonant components in the cladding satisfy the following: the dispersion-loss figure of merit F of the anti-resonant hollow fiber at the target operating wavelength is greater than a first threshold value, F = |D| / α, where D is the dispersion coefficient and α is the transmission loss coefficient. Thus, the cladding designed by this application embodiment can ensure that the "dispersion-loss figure of merit F" is greater than the first threshold value. Such an anti-resonant hollow fiber device has comprehensive advantages in key performance indicators and implementation paths, specifically reflected in the following aspects: high dispersion efficiency, wide dispersion compensation bandwidth, intrinsic low power consumption, high reliability, and high system integration. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the anti-resonant hollow fiber provided in the embodiments of this application; Figure 2 This is a schematic diagram of an application example of this application; Figure 3 This is a schematic diagram of application example two of this application; Figure 4 This is a schematic diagram of the simulation results of the dispersion coefficient and transmission loss coefficient provided in the embodiments of this application; Figure 5 This is a flowchart of the method for determining the structural parameters of anti-resonant hollow optical fiber provided in the embodiments of this application; Figure 6 This is a schematic diagram of the structural composition of the optical communication system provided in the embodiments of this application. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0027] Dispersion is mainly divided into material dispersion and waveguide dispersion. In standard single-mode fiber, it exhibits positive dispersion within the 1550nm communication window. Currently, the industry has proposed the following main technical solutions to achieve dispersion compensation in fiber optic communication systems: 1. Dispersion-compensating fiber: This scheme uses a special fiber with high negative dispersion characteristics, which is connected in series to the transmission link to compensate for the positive dispersion fiber.

[0028] 2. Chirped Fiber Bragg Grating: This scheme utilizes ultraviolet lasers to write a grating with a linearly varying refractive index period (chirped) into the fiber core. Light of different wavelengths is reflected at different positions of the grating, thereby generating a wavelength-dependent group delay and achieving dispersion compensation.

[0029] 3. Integrated solutions based on planar optical waveguides: These solutions utilize semiconductor processes to fabricate optical waveguide devices on chips, achieving dispersion compensation. They offer advantages such as compact structure and ease of large-scale integration. The main technical approaches include: 3.1 Cascaded Mach-Zehnder Interferometer: This scheme cascades multiple basic MZI units with different optical arm length differences to form a transverse filter. By precisely designing the coupling coefficient and phase difference of each MZI, the optical transfer function of the entire cascaded structure approximates the target response, thereby achieving a specific dispersion curve.

[0030] 3.2 Microring Resonator Array: This scheme utilizes the abrupt phase change generated by the microring resonator near the resonant wavelength to obtain a large dispersion. To extend the effective operating bandwidth, multiple microring resonators are typically coupled together to form a high-order coupled resonator optical waveguide or parallel array.

[0031] 4. Digital Signal Processing Algorithm: Dispersion compensation is performed at the receiving end using a digital signal processing (DSP) algorithm. This algorithm is adaptive and offers flexible compensation.

[0032] Although the above solutions each have their own characteristics, they all have obvious technical limitations: 1. Disadvantages of dispersion-compensated fiber optic solutions: high insertion loss, strong nonlinear effects, large size, high cost, and difficult integration.

[0033] 2. Disadvantages of chirped fiber Bragg grating schemes: limited bandwidth (tens of GHz), fixed dispersion with lack of flexibility, and high temperature sensitivity.

[0034] 3. Disadvantages of integration schemes based on planar optical waveguides: 3.1 Disadvantages of the Mach-Zehnder interferometer cascade scheme: narrow operating bandwidth, long cascaded device size, high cumulative loss, and high control complexity.

[0035] 3.2 Disadvantages of the micro-ring resonator array scheme: narrow operating bandwidth, extremely high process sensitivity, high coupling loss, and the need for power control, etc.

[0036] 4. Disadvantages of digital signal processing algorithms: They require high-speed analog-to-digital converters and powerful DSP chips, have high power consumption, and their processing capabilities may face bottlenecks for ultra-high-speed systems and complex modulation formats.

[0037] As can be seen from the above descriptions, each of the aforementioned dispersion compensation schemes has its shortcomings, making it difficult to achieve an ideal balance across multiple dimensions such as high performance (high bandwidth, high flatness), low loss, high integration, high stability, and low manufacturing cost. Therefore, the following technical solution is proposed according to embodiments of this application. The technical solution of this application proposes a novel anti-resonant hollow core fiber (AR-HCF), which can be used as a high-bandwidth dispersion compensation device.

[0038] To facilitate understanding of the technical solutions in the embodiments of this application, the anti-resonant hollow optical fiber is described below.

[0039] The light guiding mechanism of antiresonant hollow fiber is based on antiresonant reflection, and its transmission spectrum exhibits a series of high-loss stopbands and low-loss passbands. At the boundary between the passband and the stopband, i.e. near the resonance peak, the effective refractive index of the fiber changes drastically.

[0040] For an antiresonant hollow fiber cladding with a thickness of... , refractive index The capillary wall, its The conditions for the occurrence of a first-order resonance peak (high loss) are:

[0041] in, The resonant wavelength, The thickness of the capillary wall. The refractive index of the capillary wall; It represents the resonance order.

[0042] The refractive index relationship of antiresonant hollow fiber is shown in the following formula:

[0043] in, The effective refractive index of the anti-resonant hollow fiber; ≈ 2.405, which is the first zero of a class of Bessel functions; The target operating wavelength for anti-resonant hollow fiber; The effective radius of the anti-resonant hollow fiber; The strength of the waveguide material; The refractive index of the waveguide material (such as glass); It is the resonance order; The thickness is the capillary wall thickness.

[0044] The dispersion coefficient of antiresonant hollow fiber is shown in the following formula:

[0045] in, The dispersion coefficient of the anti-resonant hollow fiber; The target operating wavelength for anti-resonant hollow fiber; It is the speed of light in a vacuum. The effective refractive index of the anti-resonant hollow fiber.

[0046] Using the above formula, when the target operating wavelength is... Approaching a certain resonant wavelength At that time, the value of the resonance term will change drastically, thus causing The mutation ultimately leads to dispersion. This produces a sharp peak.

[0047] For anti-resonant hollow-core optical fibers used in ordinary transmission applications, although the dispersion is extremely high near the resonance peak, the transmission loss at this point also increases sharply, exhibiting a near-exponential growth. This strong correlation between dispersion and loss makes direct dispersion compensation using the resonance peak impractical, as the signal would be excessively attenuated, rendering it unusable. This is the fundamental technical obstacle preventing resonant hollow-core optical fibers from becoming high-performance dispersion compensation devices.

[0048] The technical solution of this application proposes a novel anti-resonant hollow-core optical fiber. It utilizes the significant dispersion effect generated by the drastic change in effective refractive index at the resonance peak of the anti-resonant hollow-core fiber. Through a special design of the microstructure of the anti-resonant hollow-core fiber, employing at least one mechanism among multi-ring functional separation, geometrically induced selective suppression, or hybrid resonant interference, and specific implementation methods such as multi-ring structures and non-circular interface ring tubes, the transmission loss at the target operating wavelength is significantly reduced, breaking the locked proportional growth relationship between dispersion and loss at the resonance peak, achieving a combination of high dispersion and relatively low loss. To quantify the decoupling effect of "high dispersion and low loss," this application defines a core quality factor as shown in the following formula:

[0049] in, The figure of merit is the dispersion-loss coefficient. The dispersion coefficient is... This is the transmission loss factor. The dispersion-loss figure of merit is measured in ps / (nm·dB).

[0050] Figure 1 This is a schematic diagram of the anti-resonant hollow fiber provided in the embodiments of this application, as shown below. Figure 1 As shown, the anti-resonant hollow fiber includes: an outer tube #10, and an air core #11 and a cladding #12 located inside the outer tube #10, wherein the cladding #12 is disposed around the air core #11; The cladding #12 includes one or more anti-resonant components, wherein one or more anti-resonant components in the cladding #12 satisfy the following: the dispersion-loss figure of merit of the anti-resonant hollow fiber at the target operating wavelength is greater than a first threshold value, and the dispersion-loss figure of merit is related to the dispersion coefficient and transmission loss coefficient of the anti-resonant hollow fiber.

[0051] In some embodiments, the dispersion-loss figure of merit is:

[0052] in, The figure of merit is the dispersion-loss coefficient. The dispersion coefficient is... The transmission loss coefficient α is the value of the fiber core fundamental mode (LP01 mode) measured at the target operating wavelength under standard test conditions using the cut-back method or a standard loss coefficient test method with equivalent effect, expressed in dB / km. During measurement, the optical fiber should be kept straight without macrobending, and the ambient temperature should be controlled at 23±2℃. Furthermore, in some embodiments, the dispersion-loss figure of merit F can also be equivalently represented as the reciprocal of the quality factor Q, or as the normalized dispersion efficiency parameter η = D × A_eff / α, where A_eff is the effective mode field area. Those skilled in the art should understand that regardless of the mathematical transformation used, as long as its physical essence represents the amount of dispersion compensation obtained per unit loss cost, it should be considered to fall within the protection scope of this application.

[0053] In some implementations, the first threshold value is 20 ps / (nm·dB).

[0054] In some embodiments, the anti-resonance component is a single-layer ring tube; The cladding #12 comprises a ring-shaped tube; or... The cladding #12 comprises multiple layers of annular tubes.

[0055] Here, the ring tube can also be called an anti-resonance ring, such as a glass tube / glass wall, a capillary tube / capillary wall, etc.

[0056] In some embodiments, the annular tube has a non-circular cross-section.

[0057] In some embodiments, the annular tube has a gradually varying wall thickness distribution.

[0058] In some embodiments, the gradient wall thickness distribution satisfies the following condition: the product of the refractive index and wall thickness of the annular tube facing the air core #11 region is less than the product of the refractive index and wall thickness of the annular tube away from the air core #11 region.

[0059] In one example, the cross-section of the annular tube can be elliptical, spindle-shaped, or other non-circular structures with a specific curvature, and the wall thickness of the annular tube is non-uniform (or gradually varying). This shape anisotropy differentially modulates the leakage modes at different spatial frequencies, thereby selectively enhancing the resonant effects that contribute to dispersion at the target resonant wavelength, while suppressing the leakage channels that contribute the most to loss.

[0060] In some embodiments, the cladding #12 comprises multiple annular tubes, at least two of which have one or more of the following characteristics: Different wall thickness distributions; The product of different refractive indices and wall thickness distributions; Different arrangements of the annular tubes.

[0061] In some embodiments, the multilayer annular tube has a nested structure, wherein the wall thickness, or the product of the refractive index and the wall thickness, of the annular tubes located in different layers varies non-monotonically along the radial direction.

[0062] In one example, a nested structure of two or more toroidal tubes is used. For a two-layer toroidal tube, the first layer is the innermost; the second layer, enclosing the first, is the outermost. Similarly, for a three-layer toroidal tube, the first layer is the innermost; the second layer enclosing the first, and the third layer enclosing the second, is the outermost. This nested structure allows for optimization of the thickness and spacing of each toroidal tube, enabling one or more layers to primarily control dispersion characteristics, while the remaining toroidal tubes provide additional anti-resonance constraints, reducing light field penetration into the cladding material and suppressing losses.

[0063] In one example, a hybrid resonance mechanism is used for modulation, which involves introducing specific materials or microstructures (such as high-refractive-index nanodoped dots or ultrathin coatings) into the cladding to introduce an additional, controllable resonance or scattering mechanism. This resonance causes destructive interference or resonance with the intrinsic anti-resonance mode of the anti-resonance hollow fiber, thereby suppressing the loss peak while preserving or even sharpening the desired dispersion curve.

[0064] In some embodiments, the target operating wavelength is set within a preset range near the structural resonant wavelength of the anti-resonant component, for generating dispersion at the resonant wavelength for dispersion compensation.

[0065] Here, the target operating wavelength of the anti-resonant component is set near its structural resonant wavelength to generate ultra-high group velocity dispersion for dispersion compensation at that resonant wavelength.

[0066] The above scheme, through the gradual wall thickness distribution of the toroidal tube or the differentiated combination of different toroidal tubes, suppresses the transmission loss at the resonant wavelength, thereby achieving decoupling between dispersion performance and transmission loss.

[0067] In the technical solution of this application embodiment, the anti-resonant hollow fiber device has comprehensive advantages in key performance indicators and implementation path, specifically reflected in the following aspects: high dispersion efficiency, wide dispersion compensation bandwidth, intrinsic low power consumption, high reliability, and high system integration.

[0068] The technical solutions of the embodiments of this application are illustrated below with specific application examples.

[0069] Application Example 1 like Figure 2 As shown, in this application example, the anti-resonant hollow fiber includes: an outer tube #10, and an air core #11 and a cladding #12 located inside the outer tube #10, wherein the cladding #12 is disposed around the air core #11; The cladding #1 comprises a ring-shaped tube, which includes several ring-shaped tubes distributed around the air core #11. These ring-shaped tubes are not in contact with each other and consist entirely of air. The cross-section of the ring-shaped tubes is elliptical, and the wall thickness of the ring-shaped tubes is non-uniform. In a specific implementation scenario, using... Figure 2 Taking the elliptical annular tube as an example, the ratio of its major axis (radial direction) to its minor axis (circumferential direction) typically ranges from 1.5:1 to 4:1. Its wall thickness has a minimum thickness t_min at the innermost point facing the air core #11 and a maximum thickness t_max in the regions on both sides away from the air core #11, where the ratio of t_min to t_max typically ranges from 1:1.5 to 1:3. This specific gradient distribution is configured to enhance the anti-cross-coupling effect at the target operating wavelength, thereby suppressing higher-order mode leakage while generating high negative dispersion.

[0070] Application Example 2 like Figure 3 As shown, in this application example, the anti-resonant hollow fiber includes: an outer tube #10, and an air core #11 and a cladding #12 located inside the outer tube #10, wherein the cladding #12 is disposed around the air core #11; The cladding #1 comprises two annular tubes. The first annular tube is the innermost annular tube, and the second annular tube surrounds the first annular tube, forming the outermost annular tube. The first annular tube has an elliptical cross-section, and its wall thickness is non-uniform. The second annular tube has a teardrop-shaped cross-section, and its wall thickness is also non-uniform.

[0071] Application Example 3 like Figure 4 As shown, "5-unit - single nesting" corresponds to the following structure: the cladding includes two layers of annular tubes, each containing 5 units (i.e., glass tubes), and the two layers of annular tubes form a nested structure (i.e., single nesting). "5-unit - double nesting" corresponds to the following structure: the cladding includes three layers of annular tubes, each containing 5 units (i.e., glass tubes), and the three layers of annular tubes form a nested structure (i.e., double nesting). After applying the technical solution to the embodiments of this application, Figure 4 The dispersion coefficient and transmission loss coefficient of the "5-element single-nested" and "5-element double-nested" structures were simulated respectively. According to the simulation results, near the target resonant wavelength, the optimized "5-element double-nested" structure produces a large dispersion coefficient that is basically consistent with that of the "5-element single-nested" structure. Meanwhile, at the same resonant operating point, the transmission loss coefficient of the "5-element double-nested" structure is reduced by about an order of magnitude compared to the "5-element single-nested" structure. This result reflects the idea of ​​"decoupling" dispersion and loss in this application: the introduction of the inner anti-resonant ring enhances the suppression of leakage and effectively breaks the proportional relationship between dispersion and loss at the resonant point in the traditional structure.

[0072] To achieve the design goal of having a dispersion-loss figure of merit greater than a first threshold, embodiments of this application further provide a method for determining the structural parameters of an antiresonant hollow-core optical fiber. The specific structure of the antiresonant hollow-core optical fiber can be referred to the foregoing description, such as... Figure 5 As shown, the method includes: Step 501: Optimize the structural parameters of one or more anti-resonant components in the cladding with the optimization objective of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength.

[0073] In some implementations, optimizing the structural parameters of one or more anti-resonant components in the cladding with the goal of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength includes the following steps: S1. Based on the target operating wavelength and the required dispersion compensation, select the fundamental frequency resonance order of the anti-resonance component, and preliminarily determine the range of values ​​for the wall thickness of the annular tube in the anti-resonance component, so that the target operating wavelength is located in the preset slope region of the short-wave side or long-wave side of the corresponding resonance peak. S2. Determine the structural parameters of the cladding. By adjusting the structural parameters, regulate the imaginary part of the effective refractive index of the leakage mode, so that the transmission loss coefficient is reduced while keeping the change of the dispersion coefficient within the preset range. S3. When the cladding adopts a nested structure of multiple ring tubes, the wall thickness combination of each ring tube is determined in sequence so that the resonant wavelength and the anti-resonant wavelength form a spectral overlap, thereby generating destructive interference at the target working wavelength; the wall thickness combination includes the inner wall thickness and the outer wall thickness. S4. Verify the dispersion-loss figure of merit through numerical simulation. If the dispersion-loss figure of merit is less than or equal to the first threshold, return to S2 to adjust the structural parameters until the dispersion-loss figure of merit is greater than the first threshold.

[0074] In some embodiments, the structural parameters of the cladding include at least one or more of the following: the ellipticity of the annular tube, and the wall thickness gradient factor of the annular tube; the wall thickness gradient factor is related to the maximum wall thickness and the minimum wall thickness.

[0075] In some embodiments, the method further includes: The target operating wavelength is determined and set within a preset range near the structural resonant wavelength of the anti-resonant component.

[0076] Taking a first threshold value of 20 ps / (nm·dB) as an example, in order to achieve the design goal of F greater than 20 ps / (nm·dB), this application embodiment further provides a systematic method for determining optical fiber structure parameters, including the following steps: S1. Based on the target operating wavelength λ_target and the required dispersion compensation, select the fundamental frequency resonance order m of the anti-resonance component, and preliminarily determine the range of values ​​for the tube wall thickness t, so that λ_target is located in the preset slope region of the short-wavelength side or long-wavelength side of the corresponding resonance peak. S2. Introduce cladding structure asymmetry parameters, including but not limited to: the ellipticity e of the annular tube (defined as the ratio of the major axis to the minor axis) and the wall thickness gradient factor δ (defined as the ratio of the maximum wall thickness to the minimum wall thickness). By adjusting e and δ, the effective imaginary part of the leakage mode is controlled, so that the transmission loss coefficient α is reduced while keeping the dispersion coefficient D basically unchanged. S3. When using a multi-layer nested structure, determine the wall thickness combination (t_inner, t_outer) of the inner ring tube and the outer ring tube in sequence, so that the inner resonant wavelength and the outer anti-resonant wavelength form a spectral overlap, thereby generating destructive interference at the target wavelength to suppress leakage loss. S4. Verify the F value through numerical simulation. If F>20 ps / (nm·dB) is not satisfied, return to S2 to adjust the ellipticity e or the wall thickness gradient factor δ until the condition is met.

[0077] Using the above method, the specific structural parameters of the anti-resonant hollow fiber that satisfy F>20 ps / (nm·dB) can be obtained.

[0078] Figure 6 This is a schematic diagram of the structural composition of the optical communication system provided in the embodiments of this application, as shown below. Figure 6 As shown, the optical communication system includes an anti-resonant hollow fiber #61 for dispersion compensation. The specific implementation of the anti-resonant hollow fiber #61 can be referred to the aforementioned related description.

[0079] In some embodiments, the optical communication system is a long-distance coherent optical communication system based on anti-resonant hollow optical fiber, which is suitable for long-distance transmission scenarios in backbone networks, with a transmission distance ≥1000km and a communication rate of 100Gbit / s. It adopts QPSK high-order modulation, which can effectively reduce transmission loss, suppress nonlinear effects, and improve system communication quality and transmission capacity. The following provides a detailed description of the system components, connection relationships, and working principles.

[0080] I. System Overall Architecture The system is divided into six main modules: optical transmission module, optical coupling connection module, transmission link module, optical amplification and relay module, optical receiving module, and control and monitoring auxiliary module. These modules are connected in series to form a complete optical signal transmission-reception-monitoring closed loop. Anti-resonant hollow fiber is the core component of the transmission link, which undertakes the task of long-distance optical signal transmission. The specific component selection, parameters and functions of each module are as follows.

[0081] II. Specific components and implementation details of each module 2.1 Optical Transmitter Module (Electrical-to-Optical Conversion, Signal Loading): The core function of this module is to convert electrical signals into optical signals that meet transmission requirements and load them onto an anti-resonant hollow fiber. The specific components and parameters are as follows: Light source module: It adopts a narrow linewidth external cavity laser (ECL), model ECL-1550-100, with a working wavelength of 1550nm (communication window, lowest loss), linewidth ≤100kHz, output power 10dBm, frequency stability ≤±10MHz / ℃, which can effectively reduce phase noise and adapt to coherent communication requirements. Optical modulator: A lithium niobate modulator (LN) is used, model LN-MOD-100G, with a modulation rate of 100Gbit / s, an operating wavelength range of 1530-1565nm, an insertion loss of ≤3dB, an extinction ratio of ≥25dB, and support for QPSK high-order modulation. The electrical signal is loaded onto the laser carrier to form a modulated optical signal. Driver circuit: Equipped with a high-speed DAC (model DAC-12G-16bit), driver amplifier (model AMP-100G) and clock recovery module (model CR-100G). The DAC has a sampling rate of 12GS / s and a resolution of 16bit. The driver amplifier gain is ≥20dB and the clock recovery jitter is ≤1ps, ensuring stable electrical signal driving of the modulator and guaranteeing modulation accuracy.

[0082] Optical emission module workflow: The clock recovery module outputs a stable clock signal, the high-speed DAC converts the digital electrical signal into an analog electrical signal, which is then amplified by the driver amplifier and input to the lithium niobate modulator. The continuous laser output from the narrow linewidth external cavity laser passes through the modulator and is modulated into a QPSK modulated optical signal by the applied electrical signal, which then enters the subsequent coupling module.

[0083] 2.2 Optical Coupler Connection Module (Optical Signal Adaptation, Access to Transmission Link): The core function of this module is to adapt the modulated optical signal output from the optical transmitting module to the mode field characteristics of the anti-resonant hollow fiber, thereby achieving efficient coupling and reducing signal loss. The specific components and parameters are as follows: Mode field adapter: Model MFA-ARHCF-1550, adapted for mode field matching between anti-resonant hollow fiber and single-mode fiber (SMF), with a working wavelength of 1550nm, coupling loss ≤0.5dB, and a mode field diameter adaptation range of 8-10μm, solving the coupling loss problem caused by the difference in mode field between anti-resonant hollow fiber and conventional single-mode fiber. Optical connector: SC type adapter anti-resonant hollow fiber version, model SC-ARHCF-APC, interface is APC polished, insertion loss ≤0.3dB, return loss ≥60dB, to avoid reflected light interfering with laser operation; WDM Multiplexer: A dense wavelength division multiplexer (DWDM) is used, model DWDM-40CH-1550, with 40 channels, a channel spacing of 100GHz, insertion loss ≤1.5dB, and isolation ≥30dB. It can realize multiplexing and transmission of multiple optical signals, thereby improving the system transmission capacity. In this embodiment, only one channel is used, reserving space for future expansion.

[0084] Optical coupling connection module workflow: The QPSK modulated optical signal output by the optical transmitter module is connected to the mode field adapter via the SC type optical connector. The mode field adapter completes the mode field matching with the anti-resonant hollow fiber to reduce coupling loss. Then, it is output to the transmission link module via the DWDM multiplexer (single-channel operation).

[0085] 2.3 Transmission Link Module (Long-distance optical signal transmission, core of which is anti-resonant hollow fiber): The core component of this module is antiresonant hollow fiber, with conventional single-mode fiber used as an auxiliary link. The specific components and parameters are as follows: Anti-resonant hollow fiber (AR-HCF): Model ARHCF-1550-LP, operating wavelength 1550nm, core diameter 12μm, cladding diameter 125μm, transmission loss ≤0.15dB / km, dispersion coefficient ≤±1ps / (nm·km), nonlinear coefficient ≤0.01W - ¹·km - ¹, with a length of 1000km, adopts a loose-tube stranded structure, which can effectively suppress nonlinear effects and reduce long-distance transmission loss. Compared with conventional single-mode fiber, the transmission loss is reduced by more than 30%. Auxiliary single-mode fiber (SMF): Model SMF-28e, operating wavelength 1550nm, transmission loss ≤0.2dB / km, used for short-distance connections (length ≤10m) at both ends of the system, connecting the mode field adapter with the anti-resonant hollow fiber, and the anti-resonant hollow fiber with the optical amplification module, avoiding the increase in loss caused by direct bending of the anti-resonant hollow fiber; Dispersion-compensated fiber (DCF): Model DCF-1550, dispersion compensation amount -100ps / (nm·km), length 10km, with one segment set every 100km, used to compensate for the slight dispersion of anti-resonant hollow fiber and ensure the integrity of optical signal transmission.

[0086] Transmission link module workflow: The coupled QPSK modulated optical signal is connected to the anti-resonant hollow fiber via the auxiliary single-mode fiber, and transmitted over a long distance along the anti-resonant hollow fiber. Every 100km, it passes through a dispersion compensation fiber to compensate for dispersion and avoid signal distortion, and is finally transmitted to the optical amplification repeater module.

[0087] 2.4 Optical Amplifier Repeater Module (Signal Amplification, Extending Transmission Distance): The core function of this module is to amplify the attenuated optical signal during long-distance transmission, ensuring that the signal strength meets the reception requirements. The specific components and parameters are as follows: Optical amplifier: Erbium-doped fiber amplifier (EDFA) is used, model EDFA-1550-20, with a working wavelength of 1530-1565nm, a gain range of 20-30dB, a noise figure of ≤4dB, and an output power of 20dBm. One unit is set up every 100km to amplify the attenuated optical signal and compensate for transmission loss. Raman amplifier: Model Raman-1550-15, operating wavelength 1550nm, gain ≥15dB, noise figure ≤5dB, used in series with EDFA, placed in front of EDFA to further improve signal amplification and reduce system noise; 3R Repeater: Model 3R-100G, supports 100Gbit / s rate, realizes signal retiming, reshaping and re-amplification, one unit is set up every 500km, eliminates distortion and jitter in the signal transmission process, and ensures signal quality.

[0088] The optical amplifier repeater module works as follows: The attenuated optical signal transmitted from the anti-resonant hollow fiber is first amplified by a Raman amplifier, and then amplified again by an EDFA to increase the signal power to 20dBm. Every 500km, the signal is shaped, timed and amplified by a 3R repeater to ensure that the optical signal is stably transmitted to the receiving module.

[0089] 2.5 Optical Receiver Module (Optical-to-Electronic Conversion, Signal Demodulation): The core function of this module is to convert the transmitted optical signal into an electrical signal, demodulate, amplify, and process it to restore the original information. The specific components and parameters are as follows: The coherent receiving component includes a local oscillator laser (LO), a 90° optical mixer, and a balanced detector. The LO-1550-10 LO laser operates at a wavelength of 1550nm, with a linewidth ≤50kHz and an output power of 8dBm. The MIX-90-1550 90° optical mixer has an insertion loss ≤4dB and an isolation ≥25dB. The BD-100G balanced detector has a responsivity ≥0.8A / W and a bandwidth ≥50GHz. It mixes the optical signal with the LO laser to achieve coherent demodulation. Photodetector: Backup PIN photodiode (model PIN-1550), responsivity ≥0.7A / W, bandwidth ≥40GHz. When the coherent receiving component fails, it can be switched to the PIN photodetector to ensure emergency operation of the system. Receiver signal processing components include a TIA transimpedance amplifier (model TIA-100G), an ADC (model ADC-25G-14bit), and a DSP digital signal processing module (model DSP-100G). The TIA transimpedance amplifier has a gain of ≥40dB, the ADC has a sampling rate of 25GS / s, and the DSP module supports dispersion compensation, phase recovery, and equalization processing, which can eliminate dispersion, noise, and distortion during transmission and restore the original digital electrical signal.

[0090] Optical receiver module workflow: The optical signal output from the optical amplifier repeater module enters the coherent receiver component, where it is mixed with the laser output from the local oscillator laser in a 90° optical mixer. The mixture is then converted into an electrical signal by a balanced detector. After being amplified by a TIA transimpedance amplifier, the electrical signal is converted into a digital signal by an ADC, and then processed by a DSP module to finally restore the original digital information, which is then output to subsequent devices.

[0091] 2.6 Control, Monitoring, and Auxiliary Modules (Ensuring Stable System Operation): The core function of this module is to monitor the system's operating status, control the operating parameters of each component, prevent external interference, and ensure the stable and reliable operation of the system. Specific components and parameters are as follows: Optical isolator: Model ISO-1550, operating wavelength 1550nm, insertion loss ≤0.2dB, isolation ≥30dB, installed at the laser output end of the optical emitting module and the input end of the optical receiving module to prevent reflected light from interfering with the operation of the laser and receiving components; Adjustable optical attenuator (VOA): Model VOA-1550-10, attenuation range 0-10dB, accuracy ±0.1dB, installed between the coupling module and the transmission link to adjust the optical signal power and prevent excessive optical power from damaging subsequent components; Optical switch: Model OS-1×4-1550, 1×4 channels, insertion loss ≤0.5dB, used to switch between different transmission links, facilitating system maintenance and troubleshooting; Polarization controller: Model PC-1550, operating wavelength 1550nm, insertion loss ≤0.3dB, adjusts the polarization state of the optical signal to ensure stable polarization of the optical signal, and improves coupling efficiency and reception quality; Optical monitoring module: includes optical power meter module (model PM-1550, measurement range -50~20dBm, accuracy ±0.1dBm) and optical signal-to-noise ratio (OSNR) monitoring module (model OSNR-1550, measurement range 10~40dB, accuracy ±0.5dB), which monitors optical signal power and optical signal-to-noise ratio in real time, and issues an alarm signal when the parameters are abnormal; Power module: Model PS-220V-500W, input voltage 220V AC, output voltage 5V DC, 12V DC, provides stable power to all system components, supports backup power switching, and ensures uninterrupted system operation.

[0092] III. System Connection Relationships The modules are connected in the following order to form a complete system: Optical transmitting module (narrow linewidth ECL → lithium niobate modulator → driver circuit) → optical coupling connection module (SC connector → mode field adapter → DWDM multiplexer) → transmission link module (auxiliary SMF → anti-resonant hollow fiber → dispersion compensation fiber) → optical amplification and repeater module (Raman amplifier → EDFA → 3R repeater) → transmission link module (anti-resonant hollow fiber → auxiliary SMF) → optical receiving module (coherent receiving component → TIA transimpedance amplifier → ADC → DSP); In the control and monitoring auxiliary module, optical isolators are connected to the output of the optical transmitting module and the input of the optical receiving module, respectively. The VOA is connected between the coupling module and the transmission link. The optical switch is connected to the branch of the transmission link. The polarization controller is connected between the coupling module and the anti-resonant hollow fiber. The optical monitoring module is connected to the transmission link through the branch fiber to collect optical signal parameters in real time. The power supply module supplies power to all components.

[0093] Using anti-resonant hollow fiber as the core transmission medium results in low transmission loss and weak nonlinear effects. Compared with conventional single-mode fiber transmission systems, the transmission distance is increased by more than 20%, and the signal quality is significantly improved.

[0094] It should be noted that although the above embodiments illustrate the application scenarios of the anti-resonant hollow-core optical fiber of this application in conjunction with a coherent optical communication system, the anti-resonant hollow-core optical fiber provided by this application can itself be manufactured, sold and used as an independent dispersion compensation device or module. Its application scenarios include, but are not limited to: external dispersion management of fiber laser cavity, dispersion compensation of optical coherence tomography (OCT) systems, and pulse shaping in supercontinuum generation.

[0095] Compared with the prior art, the anti-resonant hollow fiber provided in this application has at least the following beneficial effects: Compared to dispersion-compensating fiber (DCF): This application utilizes air core light guiding, which greatly reduces nonlinear effects (the nonlinear coefficient is 3-4 orders of magnitude lower than that of solid fiber), avoids signal distortion caused by high nonlinearity in DCF, and the dispersion coefficient per unit length (absolute value) can be much higher than that of DCF, greatly shortening the length of the required compensation fiber.

[0096] Compared to chirped fiber gratings (CFBGs), the anti-resonant hollow fiber of this application is a transmission-type rather than a reflection-type device, which does not require a circulator and has lower insertion loss; and through structural design, it can achieve broadband dispersion compensation on the order of tens of nanometers, far exceeding the GHz-level narrowband limitation of CFBGs.

[0097] Compared to digital signal processing (DSP), this application performs dispersion compensation directly in the optical domain, eliminating the need for high-speed ADCs and complex algorithm iterations, significantly reducing power consumption, and is transparent to signal modulation formats.

[0098] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. An anti-resonant hollow-core optical fiber, characterized in that, The anti-resonant hollow fiber includes: an outer tube, an air core and a cladding located inside the outer tube, the cladding being disposed around the air core; The cladding includes one or more anti-resonant components, wherein the one or more anti-resonant components in the cladding satisfy the following: the dispersion-loss figure of merit of the anti-resonant hollow fiber at the target operating wavelength is greater than a first threshold value, and the dispersion-loss figure of merit is related to the dispersion coefficient and transmission loss coefficient of the anti-resonant hollow fiber.

2. The anti-resonant hollow-core optical fiber according to claim 1, characterized in that, The anti-resonance component is a single-layer ring tube; The cladding comprises a ring-shaped tube; or... The cladding comprises multiple layers of annular tubes.

3. The anti-resonant hollow-core optical fiber according to claim 2, characterized in that, The annular tube has a non-circular cross-section.

4. The anti-resonant hollow-core optical fiber according to claim 2, characterized in that, The annular tube has a gradually varying wall thickness distribution.

5. The anti-resonant hollow-core optical fiber according to claim 4, characterized in that, The gradient wall thickness distribution satisfies the following condition: the product of the refractive index and wall thickness of the annular tube facing the air core region is less than the product of the refractive index and wall thickness of the annular tube away from the air core region.

6. The anti-resonant hollow-core optical fiber according to any one of claims 2 to 5, characterized in that, The cladding comprises multiple annular tubes, at least two of which have one or more of the following characteristics: Different wall thickness distributions; The product of different refractive indices and wall thickness distributions; Different arrangements of the annular tubes.

7. The anti-resonant hollow-core optical fiber according to claim 6, characterized in that, The multi-layered annular tube has a nested structure, wherein the wall thickness or the product of the refractive index and the wall thickness of the annular tubes located in different layers varies non-monotonically along the radial direction.

8. The anti-resonant hollow-core optical fiber according to any one of claims 2 to 5, characterized in that, The annular tube is at least one of quartz glass, doped glass, soft glass, or polymer material.

9. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 5, characterized in that, The target operating wavelength is set within a preset range near the structural resonant wavelength of the anti-resonant component, and is used to generate dispersion for dispersion compensation at the resonant wavelength.

10. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 5, characterized in that, The dispersion-loss figure of merit is: in, The figure of merit is the dispersion-loss coefficient. The dispersion coefficient is... This is the transmission loss coefficient.

11. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 5, characterized in that, The first threshold value is 20 ps / (nm·dB).

12. An optical communication system, characterized in that, The optical communication system includes an anti-resonant hollow fiber as described in any one of claims 1 to 11 for dispersion compensation.

13. A method for determining the structural parameters of an anti-resonant hollow-core optical fiber, characterized in that, The anti-resonant hollow fiber is the anti-resonant hollow fiber according to any one of claims 1 to 11, and the method includes: The structural parameters of one or more anti-resonant components in the cladding are optimized with the goal of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength.

14. The method for determining optical fiber structure parameters according to claim 13, characterized in that, The optimization of the structural parameters of one or more anti-resonant components in the cladding, with the goal of achieving a dispersion-loss figure of merit greater than a first threshold at the target operating wavelength, includes: S1. Based on the target operating wavelength and the required dispersion compensation, select the fundamental frequency resonance order of the anti-resonance component, and preliminarily determine the range of values ​​for the wall thickness of the annular tube in the anti-resonance component, so that the target operating wavelength is located in the preset slope region of the short-wave side or long-wave side of the corresponding resonance peak. S2. Determine the structural parameters of the cladding. By adjusting the structural parameters, regulate the imaginary part of the effective refractive index of the leakage mode, so that the transmission loss coefficient is reduced while keeping the change of the dispersion coefficient within the preset range. S3. When the cladding adopts a nested structure of multiple ring tubes, the wall thickness combination of each ring tube is determined in sequence so that the resonant wavelength and the anti-resonant wavelength form a spectral overlap, thereby generating destructive interference at the target working wavelength; the wall thickness combination includes the inner wall thickness and the outer wall thickness. S4. Verify the dispersion-loss figure of merit through numerical simulation. If the dispersion-loss figure of merit is less than or equal to the first threshold, return to S2 to adjust the structural parameters until the dispersion-loss figure of merit is greater than the first threshold.

15. The method for determining optical fiber structure parameters according to claim 14, characterized in that, The structural parameters of the cladding include at least one or more of the following: the ellipticity of the annular tube and the wall thickness gradient factor of the annular tube; the wall thickness gradient factor is related to the maximum wall thickness and the minimum wall thickness.

16. The method for determining optical fiber structure parameters according to any one of claims 13 to 15, characterized in that, The method further includes: The target operating wavelength is determined and set within a preset range near the structural resonant wavelength of the anti-resonant component.

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