Hollow-core anti-resonance optical fiber capable of breakpoint detection, production method thereof and optical cable

Abstract

The invention discloses a hollow-core anti-resonance optical fiber capable of breakpoint detection, a production method thereof and an optical cable, and belongs to the technical field of hollow-core optical fibers, the hollow-core anti-resonance optical fiber comprises an anti-resonance unit coated by a cladding, at least one solid fiber core made of germanium-doped fiber cores is arranged in the cladding, and the solid fiber cores are uniformly and spirally arranged on the periphery of the anti-resonance unit, so that the breakpoint of the hollow-core anti-resonance optical fiber can be detected. Therefore, the hollow-core optical fiber not only meets the application requirement of the anti-resonance effect, but also has the use function of breakpoint detection. The hollow-core anti-resonance optical fiber capable of breakpoint detection is simple in structure and convenient to produce and use, the anti-resonance effect of the hollow-core optical fiber can be met, breakpoint detection of the hollow-core optical fiber can be achieved on the premise that the anti-resonance use performance of the hollow-core optical fiber is not affected, and the service life of the hollow-core optical fiber is prolonged. The application of a conventional breakpoint detection technology (such as an OTDR technology) in the hollow-core optical fiber is effectively realized, the convenience and reliability of application and maintenance of the hollow-core optical fiber are further improved, the comprehensive performance of the hollow-core optical fiber is expanded, and the hollow-core optical fiber has a relatively good practical value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hollow core optical fiber, and particularly relates to a hollow core anti-resonant optical fiber capable of detecting a break point, and a production method and an optical cable thereof. BACKGROUND

[0002] A hollow core optical fiber is a breakthrough optical waveguide technology, and its core feature lies in that an optical signal is mainly transmitted in a fiber core composed of air rather than a solid glass of a traditional optical fiber. Such a unique structure makes its working principle no longer rely on traditional "total internal reflection", but utilize a precise microstructure of a cladding to confine light in an air channel to advance, including a photonic band gap optical fiber utilizing a photonic band gap effect and an anti-resonant microstructure optical fiber utilizing an anti-resonant reflection principle. Among them, the hollow core anti-resonant optical fiber, benefiting from a faster propagation speed and lower loss of light in air, can significantly reduce signal transmission delay (reduced by about 30%) and reduce signal attenuation. Therefore, it is regarded as a key technical direction to solve the bottleneck problems in the fields of future high-speed communication, high-power laser transmission, etc.

[0003] In the application process of the optical fiber, the detection of the break point of the optical fiber is a key link in the maintenance of the optical cable. For the traditional solid core optical fiber, an optical time domain reflection technology (OTDR technology) is usually used to detect the break point of the optical fiber. The working principle of the OTDR technology is similar to "radar" in the field of optical fiber communication. Backscattered light signals generated by Rayleigh scattering and Fresnel reflection at the break point of the fiber core are captured by transmitting optical pulses into the optical fiber, and the distance of the event point is accurately calculated according to the time difference of the optical pulses, so as to realize the positioning of the length, attenuation, joint loss and break point of the optical fiber and other faults.

[0004] However, since the fiber core of the hollow core optical fiber is air, there is no Fresnel reflection phenomenon at the break point due to the refractive index interface. Moreover, since the hollow core optical fiber guides light by the air core, its backscattering is about 40 dB lower than that of the solid core optical fiber, which is already lower than the detection limit of the traditional commercial OTDR technology, and it is difficult to meet the needs of the optical fiber break point detection. Even if a photon counting type OTDR or an OTDR with an amplifier is used, the detection result has low reliability due to weak signal strength and excessive noise interference.

[0005] In the prior art, research has been conducted to solve the above problems. For example, in Chinese Patent Document CN117572557A, a kind of anti-resonant hollow core fiber suitable for long-distance distributed detection is proposed, which is provided with a solid core fiber in the cavity area between the anti-resonant layer structure units. By detecting the breakage or damage of the solid core fiber, the detection result of the breakage and damage of the hollow core fiber is evaluated. Although this method can achieve the application of existing detection technology in hollow core fiber to some extent, it ignores the fact that the solid core fiber is more flexible than the hollow core fiber. Moreover, the solid core fiber is located in the inner wall of the hollow core fiber sleeve and only distributes on one side of the fiber. When the side of the hollow core fiber is partially damaged, the solid core fiber may still remain intact and have the ability to transmit light, resulting in errors between the detection result of the breakpoint and the actual situation, and the accuracy of the breakpoint detection result cannot be fully guaranteed. SUMMARY

[0006] To address one or more of the above deficiencies or improvements in the prior art, the present application provides a breakpoint-detectable hollow anti-resonant optical fiber, its production method and optical cable, which can meet the requirements of hollow anti-resonant optical fiber while achieving OTDR detection of the optical fiber breakpoint, improving the maintenance convenience and use reliability of the hollow anti-resonant optical fiber.

[0007] To achieve the above-mentioned purpose, one aspect of the present application provides a breakpoint-detectable hollow anti-resonant optical fiber, comprising an anti-resonant unit composed of a plurality of capillary glass tubes and a cladding layer arranged around the anti-resonant unit. At least one solid core for optical fiber breakpoint detection is arranged in the cladding layer. The solid core is a germanium-doped core which extends in a spiral form outside the anti-resonant unit.

[0008] As a further improvement of the present application, the relative refractive index difference between the germanium-doped core and the cladding layer is not less than 2.0%.

[0009] As a further improvement of the present application, the germanium-doped core is configured to satisfy single-mode transmission. and / or The solid core in the cladding layer is a plurality of equidistantly arranged rings; further preferably 2-4 rings. and / or The pitch of the spiral arrangement of the germanium-doped core is 5-20 mm.

[0010] As a further improvement of the present application, the outer diameter of the solid core is 2-3 μm; the wall thickness of the cladding layer is 40-80 μm. and / or The solid core is located on the side of the cladding layer away from the anti-resonant unit.

[0011] As a further improvement of the present application, the cladding includes an inner cladding located at the inner side and an outer cladding located at the outer side, and the germanium-doped fiber core is located in the outer cladding.

[0012] As a further improvement of the present application, the germanium-doped fiber core is located at the center of the thickness direction of the outer cladding, and the ratio between the wall thickness of the outer cladding and the wall thickness of the inner cladding is 3:1~1:7.

[0013] Another aspect of the present application also provides a production method of the hollow-core anti-resonant optical fiber, for producing the break-point detectable hollow-core anti-resonant optical fiber, which includes the following processes: (1) selecting a first quartz sleeve tube, and opening an embedding hole in the wall thickness area of the first quartz sleeve tube according to the design parameters of the solid core, and embedding a germanium-doped quartz rod in the embedding hole to make an outer sleeve; (2) selecting a second quartz sleeve tube, and making an anti-resonant core rod on the inner side of the second quartz sleeve tube according to the design parameters of the anti-resonant unit to make an inner rod body; (3) embedding and assembling the inner rod body in the outer sleeve to form a hollow-core anti-resonant optical fiber preform rod which is coaxial and separated from each other; (4) assembling the hollow-core anti-resonant optical fiber preform rod to a rotary drawing tower; wherein the tail end of the inner rod body is fixedly connected, and the outer sleeve is assembled on the rotating mechanism; (5) drawing the hollow-core anti-resonant optical fiber, and simultaneously drawing the inner rod body and rotatingly drawing the outer sleeve, so that the outer periphery of the inner fiber drawn by the inner rod body can be synchronously formed with the outer fiber drawn by the outer sleeve, and finally a hollow-core anti-resonant optical fiber is obtained, which is covered by a cladding and has an anti-resonant unit and a spiral solid core in the cladding.

[0014] As a further improvement of the present application, when the second quartz sleeve tube is selected in process (2), the outer diameter of the second quartz sleeve tube is controlled to be smaller than the inner diameter of the first quartz sleeve tube , and , satisfying the following relationship: .

[0015] As a further improvement of the present application, in process (5), the rotating speed of the outer sleeve during drawing is controlled to be 1rpm~5rpm.

[0016] Another aspect of the present application also provides a hollow-core anti-resonant optical fiber cable, which contains at least one hollow-core anti-resonant optical fiber prepared by the production method of the hollow-core anti-resonant optical fiber.

[0017] As a further improvement of the present application, the hollow-core anti-resonant fiber cable is a hybrid cable formed by mixing a hollow-core fiber cable and a solid-core fiber cable; Wherein, the hollow-core fiber cable contains at least one anti-resonant hollow-core fiber; the solid-core fiber cable includes at least one solid-core fiber unit, the solid-core fiber unit includes a loose tube and a plurality of solid-core fibers wrapped by the loose tube, and the solid-core fibers have a specification of G.652D, G.654E or G.655.

[0018] The above technical features can be combined with each other as long as they do not conflict with each other.

[0019] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects: The break-point detectable anti-resonant hollow-core fiber of the present application includes an anti-resonant unit covered by a cladding, and at least one solid core with a germanium-doped core in the cladding, and the solid core is uniformly spirally arranged outside the anti-resonant unit, so that the hollow-core fiber not only meets the application requirements of the anti-resonant effect, but also has the use function of break-point detection, effectively realizing the application of conventional break-point detection technology in the hollow-core fiber and improving the comprehensive use performance of the hollow-core fiber.

[0020] The break-point detectable anti-resonant hollow-core fiber of the present application has a simple structure, convenient production and use, can meet the anti-resonant effect of the hollow-core fiber, and can realize the break-point detection of the hollow-core fiber without affecting the use performance of the hollow-core fiber, effectively realizing the application of conventional break-point detection technology (such as OTDR technology) in the hollow-core fiber, further improving the convenience and reliability of the application and maintenance of the hollow-core fiber, and having good practical value. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 is a schematic diagram of the end face structure of the break-point detectable anti-resonant hollow-core fiber in the embodiments of the present application; Figure 2 is a schematic diagram of the outer sleeve structure of the core rod for preparing the anti-resonant hollow-core fiber in the embodiments of the present application; Figure 3 is a schematic diagram of the inner rod structure of the core rod for preparing the anti-resonant hollow-core fiber in the embodiments of the present application; Figure 4Figure 1 is a schematic diagram of a core rod structure combined by an outer sleeve and an inner rod body in an embodiment of the present application; In all the drawings, the same reference signs refer to the same technical features, specifically: 1, anti-resonance unit; 2, cladding layer; 3, solid core; 4, coating layer; 5, outer sleeve; 6, inner rod body; 101, capillary glass tube; 201, inner cladding layer; 202, outer cladding layer; 501, first quartz liner; 502, germanium-doped quartz rod; 601, second quartz liner; 602, anti-resonance glass tube. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0024] In the description of the present application, it should be understood that, unless otherwise explicitly specified and limited, the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0025] In addition, unless otherwise explicitly limited, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified and limited.

[0026] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or it can only mean that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or it can only mean that the horizontal height of the first feature is less than that of the second feature.

[0028] In the following, with reference to Figures 1-4 The present application describes a break point detectable hollow core anti-resonant optical fiber and its production method according to the preferred embodiment of the present application, and an optical cable comprising the same.

[0029] As an aspect of the present application, a break point detectable hollow core anti-resonant optical fiber is provided, which has a structure as shown in Figure 1 The corresponding arrangement of each capillary glass tube 101 in the anti-resonant unit 1 in the lumen of the cladding 2 makes the hollow core optical fiber have an anti-resonant effect, meeting the setting requirements of the hollow core anti-resonant optical fiber.

[0030] At the same time, at least one solid core 3 for optical fiber break point detection is arranged in the cladding 2; the solid core 3 is further specifically a germanium-doped core, which is arranged in a spiral form outside the anti-resonant unit 1.

[0031] Since the breakage direction of the optical fiber when it is broken is usually developed from the outside to the inside along the radial direction, by arranging the solid core 3 for detection inside the cladding 2 instead of in the lumen surrounded by the cladding 2, the solid core 3 is located in the "first breakage component" when the anti-resonant optical fiber is broken, avoiding the risk that the capillary glass tube 101 breaks before the solid core 3 from the arrangement position, and ensuring the accuracy of the break point detection of the hollow core optical fiber.

[0032] The setting of the solid core 3 in the cladding 2 makes the light waveguide structure between the germanium-doped core and the quartz cladding 2, which provides the condition for the breakpoint detection of the optical fiber (especially the OTDR technology detection). Moreover, based on the spiral arrangement of the germanium-doped core, the light waveguide structure for detection can be uniformly distributed on the outer wall of the anti-resonant optical fiber in the circumferential direction, which ensures that when the anti-resonant optical fiber is broken, the germanium-doped core can be accurately positioned by the breakpoint detection technology due to the fracture, thereby meeting the breakpoint detection requirement of the anti-resonant optical fiber.

[0033] In addition, the transmission performance of the anti-resonant optical fiber is determined by the end face structure. Although the end face structure of the anti-resonant optical fiber in the prior art has a rotational symmetry, it is not perfect circumferential symmetry in most cases. At this time, if the germanium-doped core in the anti-resonant end face structure adopts a spiral arrangement, it will inevitably affect the transmission performance of the anti-resonant optical fiber. Therefore, for the scheme in the preferred embodiment of the present application, the germanium-doped core is arranged in the annular cladding 2, and the perfect circumferential symmetry of the annular structure is utilized to avoid affecting the anti-resonant end face structure under the premise of spiral arrangement of the detection light waveguide, thereby ensuring the transmission performance of the anti-resonant optical fiber.

[0034] Meanwhile, the reason why the solid core 3 is selected as a germanium-doped core is mainly that the softening point temperature (about 1600°C) of the germanium-doped core is close to the softening point temperature (about 1700°C) of the pure quartz cladding 2, which can effectively reduce the interface stress during drawing and avoid delamination, thereby ensuring the accuracy of the arrangement of the solid core 3 in the cladding 2.

[0035] The spiral structure of the germanium-doped core is equivalent to a curved optical fiber. If the spiral pitch is too small, the bending of the germanium-doped core will be too large, resulting in high optical transmission signal loss during operation and reducing the signal-to-noise ratio during OTDR testing. If the spiral pitch is too large, the light waveguide structure is sparse on the outer wall of the hollow optical fiber, which will weaken the structural advantage of the spiral arrangement of the solid core 3. Based on the above technical considerations, the spiral arrangement pitch of the germanium-doped core is preferably 5mm-20mm.

[0036] On this basis, in order to ensure the detection distance and the uniformity of the distribution of the solid core 3 on the outer wall of the anti-resonant unit 1, the solid core 3 in the preferred embodiment is arranged in the cladding 2 in the form of multiple annular equidistant arrangements. By increasing the number of solid cores 3, the degree of bending of the light waveguide is reduced, and at the same time, the problem of crosstalk caused by too dense solid cores 3 during testing is avoided. Therefore, in actual arrangement, the number of solid cores arranged is 2-4; for example Figure 1 four as shown in the figure.

[0037] Further, in the germanium-doped core, the relative refractive index difference between the germanium-doped core and the cladding is not less than 2.0%.

[0038] It should be noted that the "relative refractive index difference " represents the degree of change of the refractive index of a substance relative to pure silicon dioxide, which is calculated by the formula: , wherein, is the refractive index at the germanium-doped core; is the refractive index of pure silicon dioxide.

[0039] The use of a high-concentration doped germanium core allows the refractive index to be greatly increased, and a high contrast is formed between the core and the pure quartz cladding 2, which enhances the OTDR backscattering signal during subsequent breakpoint detection, thereby improving the breakpoint detection sensitivity of the anti-resonant optical fiber.

[0040] In actual settings, the backscattering coefficient of the high-germanium-doped core is about 15 dB higher than that of pure quartz, which can compensate for the low scattering (-40 dB) of the hollow core optical fiber, and the signal-to-noise ratio during OTDR detection is improved by no less than 10 dB, thereby effectively ensuring the breakpoint detection sensitivity of the anti-resonant optical fiber.

[0041] In more detail, the germanium-doped core in the preferred embodiment is configured to satisfy single-mode transmission.

[0042] According to the single-mode transmission condition: the normalized frequency parameter < 2.405; combined with the calculation formula of the normalized frequency parameter: , wherein, is the core radius; is the operating wavelength; is the numerical aperture of the optical fiber. It can be obtained that: At this time, as long as the operating wavelength of the detection light satisfies the above relationship, the germanium-doped core can satisfy the requirement of single-mode transmission.

[0043] In a specific embodiment, the outer diameter of the solid core 3 is 2 μm ~ 3 μm. On this basis, the operating wavelength of the solid core 3 for single-mode transmission can be quickly selected.

[0044] For example, in a specific embodiment, the outer diameter of the solid core 3 is 3 μm, and the numerical aperture of the optical fiber is 0.22; at this time, the detection light with an operating wavelength of 1310 nm is selected, and the calculation of the normalized frequency parameter is as follows:

[0045] Obviously, the solid core 3 at this time satisfies the requirement of single-mode transmission. In addition, in the foregoing embodiment, as long as the operating wavelength of the detection light is greater than 860 nm, the single-mode transmission requirement of the solid core 3 can be satisfied, which provides sufficient convenience for the selection of breakpoint detection conditions and simplifies the breakpoint detection process of the hollow anti-resonant optical fiber.

[0046] Based on the small core diameter design of the solid core 3 (compared to the outer diameter size of the conventional core 8 μm ~ 10 μm), on the one hand, it ensures that the solid core 3 can be embedded in the thin-walled structure (corresponding to the wall thickness of the embedded cladding is usually not more than 50 μm), on the other hand, it also avoids the optical performance of the hollow core optical fiber being significantly affected due to the setting of the solid core 3. Based on the single-mode transmission configuration, not only the long-distance transmission during the breakpoint detection is supported, but also the stability of the OTDR detection signal is ensured.

[0047] Further, in the preferred embodiment, the wall thickness of the cladding 2 of the hollow core anti-resonant optical fiber is 40 μm ~ 80 μm, and further preferably 60 μm.

[0048] In addition, when the solid core 3 is provided, it is preferably provided on the side of the cladding 2 away from the anti-resonant unit 1.

[0049] More specifically, for the inner and outer cladding 201 and 202, the wall thickness between them preferably satisfies the following ratio relationship, that is, the ratio between the wall thickness of the outer cladding 202 and the wall thickness of the inner cladding 201 is 3:1 ~ 1:7.

[0050] In one specific example, the germanium-doped core is located at the center position of the outer cladding 202.

[0051] More specifically, for the inner and outer cladding 201 and 202, the wall thickness between them preferably satisfies the following ratio relationship, that is, the ratio between the wall thickness of the outer cladding 202 and the wall thickness of the inner cladding 201 is 3:1 ~ 1:7.

[0052] It can be understood that for the design of the foregoing size ratio, it can be realized by selecting the pure quartz liner tube and designing the size of the germanium-doped quartz core rod in the process of making the preform rod, which is not described here.

[0053] More preferably, for the hollow core anti-resonant optical fiber in the preferred embodiment, the outer side of the cladding 2 is further provided with a coating layer 4, such as an acrylic resin coating layer, which can be single-layer or multi-layer to balance the mechanical strength and bending performance of the optical fiber.

[0054] As another aspect of the present application, a production method of a hollow core anti-resonant optical fiber is further provided for producing the aforementioned breakpoint detectable hollow core anti-resonant optical fiber.

[0055] Specifically, the production method of the hollow core anti-resonant optical fiber preferably comprises the following processes: (1) Select a first quartz liner tube 501, and according to the design parameters of the solid core 3, open an embedding hole in the wall thickness area of the first quartz liner tube 501, and embed a germanium-doped quartz rod 502 in the embedding hole, to make a preform rod 500 as shown inFigure 2 The outer sleeve 5 shown in FIG. 1; Specifically, in the process of making the outer sleeve 5, the design parameters of the solid core 3 preferably include the ratio between the outer diameter of the solid core 3 and the wall thickness of the outer cladding 202, and the setting position of the solid core 3 in the direction of the wall thickness of the outer cladding 202.

[0056] Of course, for the germanium-doped quartz rod 502, its outer diameter size needs to correspond to the wall thickness of the first quartz liner tube 501 when it is made, that is, to correspond to the design ratio between the outer diameter of the solid core 3 and the wall thickness of the outer cladding 202. At the same time, it also needs to refer to the germanium doping mole concentration when the solid core 3 is designed, which is not described here.

[0057] (2) Select the second quartz liner tube 601, and make the anti-resonance core rod in the inside of the second quartz liner tube 601 according to the design parameters of the anti-resonance unit 1, to make the inner rod body 6 shown in FIG. 2; Figure 3 The inner rod body 6 shown in FIG. 2; It should be noted that the technology for making the anti-resonance core rod based on the anti-resonance glass tube 602 is a known prior art, which is not the core of the design of the present application, so it is not described here.

[0058] At the same time, for the selection of the second quartz liner tube 601, the wall thickness ratio between the inner cladding 201 and the outer cladding 202 and the wall thickness size of the first quartz liner tube 501 are referred to for selection design.

[0059] More specifically, in actual setting, the wall thickness of the first quartz liner tube 501 is 5mm~10mm, and the wall thickness of the second quartz liner tube 601 is 0.2mm~1mm. In addition, for the glass tube forming the anti-resonance unit 1, the wall thickness is preferably 0.1mm~0.5mm.

[0060] (3) Embed and assemble the inner rod body 6 in the outer sleeve 5 to form an inner-outer coaxial and mutually separated hollow-core anti-resonance optical fiber preform rod; (4) Assemble the hollow-core anti-resonance optical fiber preform rod to the rotary drawing tower; wherein the tail end of the inner rod body 6 is fixedly connected, and the outer sleeve 5 is assembled on the rotating mechanism; When assembling the hollow-core anti-resonance optical fiber preform rod, the coaxiality between the inner rod body 6 and the outer sleeve 5 needs to be fully considered to avoid errors in subsequent drawing preparation.

[0061] (5) Draw the hollow-core anti-resonance optical fiber, and at the same time draw the inner rod body 6 and rotate the outer sleeve 5, so that the inner fiber periphery drawn by the inner rod body 6 can be synchronously formed with the outer fiber formed by the rotary drawing of the outer sleeve 5, and finally obtain the hollow-core anti-resonance optical fiber in which the cladding 2 covers the anti-resonance unit 1 and the cladding 2 is provided with the spiral solid core 3, as shown in FIG. 3. Figure 1 FIG. 3.

[0062] Further, since the outer sleeve 5 needs to be in a rotating state throughout the drawing process, and the inner rod 6 does not rotate, a certain gap needs to be ensured between the inner rod 6 and the outer sleeve 5, such as the gap W shown in FIG. 6. Figure 4

[0063] In actual settings, the gap between the inner rod 6 and the outer sleeve 5 is related to the difficulty of the hollow-core anti-resonant optical fiber drawing production and the quality of the drawing preparation. If the gap is too small, the assembly precision and control precision of the preform on the drawing tower are required to be high, and it is necessary to ensure that the inner rod 6 and the outer sleeve 5 have a very high coaxiality during assembly and rotating drawing process, otherwise contact friction between the inner rod 6 and the outer sleeve 5 will occur, affecting the reliability of the optical fiber drawing preparation; however, if the gap is too large, it may affect the cladding 2 uniformity of the drawn optical fiber, there is an obvious inner and outer cladding boundary, and even a micro gap is introduced, which affects the performance of the hollow-core anti-resonant optical fiber.

[0064] In the preferred embodiment, considering the influence of various factors, in the process (2), the outer diameter of the second quartz liner 601 is controlled to be smaller than the inner diameter of the first quartz liner 501, and the following relationship is satisfied:

[0065] As an example, after the coaxial assembly of the hollow-core anti-resonant optical fiber preform is completed, the gap between the inner wall surface of the outer sleeve 5 and the outer wall surface of the inner rod 6 is preferably not more than 0.5 mm.

[0066] Further preferably, in the process (5), the rotating speed of the outer sleeve 5 during drawing is controlled to be 1 rpm to 5 rpm.

[0067] Based on the design of the above production method, the drawing production of the hollow-core anti-resonant optical fiber can be accurately completed, and the hollow-core optical fiber that meets the anti-resonance effect and the breakpoint detection requirement can be obtained.

[0068] On this basis, the preferred embodiment of the present application further proposes a hollow-core anti-resonant optical fiber cable, which internally contains at least one hollow-core anti-resonant optical fiber prepared by the above production method of the hollow-core anti-resonant optical fiber.

[0069] ​​​​​​Further preferably, according to the requirement of practical application, the aforementioned hollow-core anti-resonant fiber optical cable is a hybrid optical cable formed after the hollow-core fiber optical cable is mixed and cabled with a solid-core fiber optical cable. The hollow-core fiber optical cable contains at least one hollow-core anti-resonant fiber. The solid-core fiber optical cable includes at least one solid-core fiber unit, and the solid-core fiber unit includes a loose tube and a plurality of solid-core fibers wrapped by the loose tube. In more detail, the specification of the solid-core fiber is G.652D, G.654E or G.655.

[0070] In the laying and using process of the aforementioned hollow-core anti-resonant fiber optical cable, when the breakpoint detection requirement of the hollow-core fiber is faced, the detection can be completed based on the following process: The hollow-core fiber is connected to an OTDR detection device, the solid core 3 in the cladding 2 is shot, the abnormality or breakpoint position of the solid core 3 is detected, the ratio between the abnormality position length and the total length of the solid core 3 is calculated, and then the actual position of the breakpoint on the hollow-core anti-resonant fiber is calculated according to the ratio, so as to realize the breakpoint detection on the hollow-core anti-resonant fiber.

[0071] Obviously, based on the calculation of the ratio between the breakpoint length of the solid core 3 and the total length of the solid core 3, the length difference caused by the spiral arrangement of the solid core 3 (the length difference between the solid core 3 and the actual length of the fiber) is simplified, the breakpoint position determination process in the breakpoint detection is simplified, the calculation amount is saved, and the accuracy of the abnormality position detection is improved.

[0072] The hollow-core anti-resonant fiber capable of breakpoint detection in the application has simple structure, convenient production and use, can meet the anti-resonance effect of the hollow-core fiber, can realize the breakpoint detection of the hollow-core fiber without affecting the use performance of the hollow-core fiber, effectively realizes the application of the conventional breakpoint detection technology (such as the OTDR technology) in the hollow-core fiber, further improves the convenience and reliability of the application and maintenance of the hollow-core fiber, and has good practical value.

[0073] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A break point detectable hollow core anti-resonant fiber, comprising an anti-resonant unit composed of a plurality of capillary glass tubes and a cladding arranged outside the anti-resonant unit; characterized in that, at least one solid core for optical fiber break point detection is arranged in the cladding; the solid core is a germanium-doped core which extends in a spiral form outside the anti-resonant unit.

2. The breakage point detectable hollow core anti-resonant optical fiber of claim 1, wherein, In the germanium-doped core, the relative refractive index difference between the germanium-doped core and the cladding is not less than 2.0%.

3. The breakage point detectable hollow core anti-resonant optical fiber of claim 2, wherein, The germanium-doped core is configured to satisfy single-mode transmission; and / or the solid core in the cladding is a plurality of equidistantly arranged in a ring direction; and / or the pitch of the spiral arrangement of the germanium-doped core is 5mm-20mm.

4. The breakage detectable hollow core anti-resonant optical fiber according to any one of claims 1 to 3, characterized in that, The outer diameter of the solid core is 2μm-3μm; the wall thickness of the cladding is 40μm-80μm; and / or the solid core is located on the side of the cladding away from the anti-resonant unit.

5. The breakage detectable hollow core anti-resonant optical fiber according to claim 4, wherein, The cladding comprises an inner cladding on the inner side and an outer cladding on the outer side, and the germanium-doped core is located in the outer cladding.

6. The breakage detectable hollow core anti-resonant optical fiber according to claim 5, wherein, The germanium-doped core is located at the center of the thickness direction of the outer cladding, and the ratio between the wall thickness of the outer cladding and the wall thickness of the inner cladding is 1:7-3:

1.

7. A method for producing a hollow-core anti-resonant optical fiber for break point detectable hollow-core anti-resonant optical fiber according to any one of claims 1 to 6, characterized in that, The production method comprises the following processes: (1) selecting a first quartz bushing, and opening an embedding hole in the wall thickness area of the first quartz bushing according to the design parameters of the solid core, and embedding a germanium-doped quartz rod in the embedding hole to make an outer sleeve; (2) selecting a second quartz bushing, and making an anti-resonant core rod on the inner side of the second quartz bushing according to the design parameters of the anti-resonant unit to make an inner rod body; (3) embedding and assembling the inner rod body in the outer sleeve to form a hollow core anti-resonant fiber preform rod coaxial with each other and separated from each other; (4) assembling the hollow core anti-resonant fiber preform rod to a rotary drawing tower; wherein the tail end of the inner rod body is fixedly connected, and the outer sleeve is assembled on the rotating mechanism; (5) drawing the hollow core anti-resonant fiber, while drawing the inner rod body and rotating the outer sleeve, so that the outer fiber formed by the rotation drawing of the outer sleeve can be synchronously formed on the outer periphery of the inner fiber drawn by the inner rod body, and finally a hollow core anti-resonant fiber is obtained, which is composed of an anti-resonant unit covered by a cladding and a spiral solid core arranged in the cladding.

8. The method of producing an antiresonant hollow fiber according to claim 7, wherein In the process (2) of selecting the second quartz liner tube, the outer diameter of the second quartz liner tube is controlled to be smaller than the inner diameter of the first quartz liner tube , and , and , satisfies the following relationship 。 9. The method of producing an antiresonant hollow core fiber according to claim 7 or 8, characterized in that, In process (5), the rotating speed of the outer sleeve during drawing is controlled to be 1rpm-5rpm.

10. A hollow core anti-resonant optical fiber cable characterized by, The hollow core anti-resonant fiber cable comprises at least one hollow core anti-resonant fiber prepared by the production method of any one of claims 7-9.

11. The hollow-core, anti-resonant optical fiber cable of claim 10, wherein, The hollow core anti-resonant fiber cable is a hybrid cable formed by mixing a hollow core fiber cable and a solid core fiber cable; wherein the hollow core fiber cable comprises at least one hollow core anti-resonant fiber; the solid core fiber cable comprises at least one solid core fiber unit, the solid core fiber unit comprises a loose sleeve and a plurality of solid core fibers wrapped by the loose sleeve, and the specification of the solid core fiber is G.652D, G.654E or G.655.

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