A multi-core optical fiber structure with an isolation film

Abstract

The present invention provides a multi-core optical fiber structure with an isolation film, belonging to the technical field of special optical fibers. It includes a common cladding and at least one core uniformly wrapped in the common cladding. Adjacent cores are isolated from each other by coating an isolation film on the outer side of one of the cores or both cores, and there is a retained cladding between the isolation film and the core. In the present invention, a metal film is coated around the core, which has a good isolation effect on the core modes outside the metal film. At the same time, the thickness of the retained cladding in the film is relatively thin. While maintaining the low crosstalk characteristics, the cores can be closer to each other, meeting the requirements of high core density and low inter-core crosstalk for multi-core optical fibers; there are no requirements for the specific parameters of each core, and it can provide high-density and low-crosstalk characteristics in the case of the same type of core without increasing the complexity of devices and systems.

Description

Technical Field

[0001] The present invention relates to the technical field of special optical fibers, and particularly to a multi-core optical fiber structure with an isolation film that achieves high density and low crosstalk performance. Background Art

[0002] Multi-core optical fibers are the basis for high-capacity optical fiber communication and optical fiber sensing. A multi-core optical fiber accommodates more than one core in the same optical fiber, significantly improving the multiplexing density of a single optical fiber, which is an important development direction of special optical fibers. Inter-core crosstalk is a key indicator of multi-core optical fibers, which shows the degree of mutual influence between the cores of multi-core optical fibers. For applications where each core transmits independently, crosstalk between cores will increase the signal error rate, reduce the transmission quality and transmission distance of the signal. Therefore, special structural designs are required for multi-core optical fibers to control and reduce inter-core crosstalk.

[0003] Currently, the common methods for controlling inter-core crosstalk are mainly divided into three categories: increasing the core distance, trench assistance, and core differentiation. When the cores gradually approach each other, the mode field supported by one core will overlap with the regions where other cores are located, thereby affecting the mode fields transmitted in other cores. The closer the cores are to each other and the higher the degree of mode field overlap, the faster the power exchange occurs between the cores. Therefore, increasing the core distance and using trenches to assist in restricting the mode field are both effective means for controlling inter-core crosstalk.

[0004] To reduce crosstalk by increasing the core distance, it is usually necessary to ensure that the core distance is greater than 4-5 times the core radius, which is about 20-25 μm for conventional single-mode cores. If the core is a few-mode or multi-mode optical fiber, the expansion of the mode field is more serious, and the core distance will further increase. Trench assistance utilizes the characteristic that the refractive index of fluorine-doped quartz is slightly lower than that of pure quartz. Through the transmission characteristics of light in multi-layer media, the light field can be better confined within the trench range, reducing the influence on the regions where other cores are located. The width of the fluorine-doped quartz trench is 2-5 μm, and there is usually a pure quartz ring between the trench and the core. This method increases the actual core area while reducing crosstalk, and still results in a relatively large core distance of about 18 μm at the same crosstalk level.

[0005] Heterogeneous cores can cause mismatch between overlapping mode fields, suppressing the degree of power exchange, thereby reducing the occurrence degree of crosstalk. When the core differences are large enough, even if the cores are close to each other, the proportion of the exchanged power can be as low as less than 1%, which is a good means to reduce the core distance and increase the core density while controlling crosstalk.

[0006] At present, while reducing crosstalk, low-crosstalk multi-core optical fibers will increase the distance between the cores to varying degrees, restricting the core density; the heterogeneous core solution can better meet the high-density requirements, but the core heterogeneity leads to differences in the mode fields supported by each core, increasing the difficulty of the composition of functional devices and systems. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-core optical fiber structure with an isolation film that has a good isolation effect on the core modes outside the metal isolation film, meets the requirements of high core density and low inter-core crosstalk of multi-core optical fibers, so as to solve at least one of the technical problems existing in the above-mentioned background technology.

[0008] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A multi-core optical fiber structure with an isolation film provided by the present invention includes a common cladding and at least one core uniformly wrapped in the common cladding.

[0010] Two adjacent cores are isolated from each other by coating an isolation film on the outside of one of the cores or both cores, and there is a remaining cladding between the isolation film and the core.

[0011] Preferably, the material for making the isolation film is a metal material.

[0012] Preferably, the material for making the isolation film is gold.

[0013] Preferably, the thickness of the remaining cladding is less than the radius of the core.

[0014] Preferably, the thickness of the isolation film is less than the thickness of the remaining cladding.

[0015] Preferably, the remaining cladding and the common cladding are made of the same material.

[0016] Preferably, the refractive index of the core is higher than that of the common cladding, and the difference between the refractive index of the core and that of the common cladding is 0.005.

[0017] Preferably, the diameter of the core is 8 μm.

[0018] Preferably, the thickness of the remaining cladding is 0.99 μm.

[0019] Preferably, the thickness of the isolation film is 0.01 μm.

[0020] Advantages of the present invention: The metal isolation film is coated around the fiber core, which has a good isolation effect on the core modes outside the metal film. At the same time, the remaining cladding thickness in the film is relatively thin, and the cores can be closer to each other while maintaining the low crosstalk characteristic, meeting the requirements of high core density and low inter-core crosstalk for multi-core optical fibers; there are no requirements for the specific parameters of each core, and it can provide high-density and low-crosstalk characteristics in the case of the same type of core, without increasing the complexity of the device and system.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description, and these will become apparent from the following description or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic cross-sectional view of the multi-core optical fiber structure with an isolation film according to Embodiment 1 of the present invention.

[0024] Figure 2 It is a schematic cross-sectional view of the multi-core optical fiber structure with an isolation film according to Embodiment 2 of the present invention.

[0025] Figure 3 It is a schematic cross-sectional view of the multi-core optical fiber structure with an isolation film according to Embodiment 3 of the present invention.

[0026] Wherein: 1 - common cladding; 2 - core; 3 - isolation film; 4 - remaining cladding. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described through the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0028] Those skilled in the art of the present technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the present invention belongs. It should also be understood that terms defined in general dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as such here.

[0029] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or their groups.

[0030] In the description of this patent, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this patent and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this patent.

[0031] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled", "set" should be understood in a broad sense. For example, it can be fixedly connected and set, or detachably connected and set, or integrally connected and set. For those of ordinary skill in the art, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0032] For the convenience of understanding the present invention, the present invention will be further explained below with reference to the accompanying drawings in specific embodiments, and the specific embodiments do not constitute a limitation to the embodiments of the present invention.

[0033] Those skilled in the art should understand that the drawings are only schematic diagrams of the embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0034] Embodiment 1

[0035] As Figure 1 shown, Embodiment 1 of the present invention provides a multi-core optical fiber structure with an isolation film, including a common cladding 1 and at least one core 2 uniformly wrapped in the common cladding 1. Adjacent cores 2 are isolated from each other by coating an isolation film 3 on the outer side of one of the cores 2, and there is a remaining cladding 4 between the isolation film 3 and the core 2.

[0036] This optical fiber is a longitudinally uniform cylindrical structure, composed of two mutually separated cores in the middle, a metal isolation film surrounding the right core, a remaining cladding between the right core and the metal isolation film, and a common cladding outside the two cores. The structure described in this embodiment is applicable to the case where the refractive index of the common cladding is lower than that of the core, and the refractive index of the remaining cladding is lower than that of the core.

[0037] The parameters of the two cores are exactly the same. The materials of the reserved cladding and the common cladding are the same, with the same refractive index. The material of the metal isolation film is gold.

[0038] In Embodiment 1 of the present invention, the key parameters can be selected as follows: the diameters of the two cores are both 8 μm, the refractive index difference from the common cladding is 0.005, the thickness of the reserved cladding is 0.99 μm, the thickness of the gold thin isolation film is 0.01 μm, and the center distance between the two cores is 10 μm. At this time, the minimum edge distance between the two cores is only 2 μm.

[0039] Embodiment 2

[0040] As Figure 2 shown, Embodiment 2 of the present invention provides a multi-core optical fiber structure with an isolation film, including a common cladding 1 and at least one core 2 uniformly wrapped in the common cladding 1. Two adjacent cores 2 are isolated from each other by covering an isolation film 3 on the outside, and there is a reserved cladding 4 between the isolation film 3 and the core 2.

[0041] The optical fiber described in Embodiment 2 of the present invention is a longitudinally uniform cylindrical structure, which is composed of two mutually separated cores in the middle, metal isolation films provided on both cores, a reserved cladding provided between the core and the metal isolation film, and a common cladding outside the two cores. The structure described in this embodiment is applicable to the case where the refractive index of the common cladding is lower than that of the core, and the refractive index of the reserved cladding is lower than that of the core.

[0042] The parameters of the two cores are exactly the same. The materials of the reserved cladding and the common cladding are the same, with the same refractive index. The material of the metal isolation film is gold.

[0043] In Embodiment 2 of the present invention, the key parameters can be selected as follows: the diameters of the two cores are both 8 μm, the refractive index difference from the common cladding is 0.005, the thicknesses of the two reserved claddings are both 0.99 μm, the thicknesses of the gold isolation films are both 0.01 μm, and the center distance between the two cores is 10 μm. At this time, the edges of the two metal isolation films are adjacent.

[0044] Embodiment 3

[0045] As Figure 3 shown, Embodiment 3 of the present invention provides a multi-core optical fiber structure with an isolation film, including a common cladding 1 and at least one core 2 uniformly wrapped in the common cladding 1. Two adjacent cores 2 are isolated from each other by covering an isolation film 3 on the outside of one of the cores 2 or both of the cores 2, and there is a reserved cladding 4 between the isolation film 3 and the core 2.

[0046] The optical fiber described in Embodiment 2 of the present invention has a longitudinally uniform cylindrical structure. The number of cores is 9, with one core located on the central axis of the common cladding, and the other 8 cores evenly surrounding the core located on the central axis of the common cladding. The structure described in this embodiment is applicable to the case where the refractive index of the common cladding is lower than that of the core, and the refractive index of the remaining cladding is lower than that of the core.

[0047] In Embodiment 3 of the present invention, an isolation film is coated on the core located on the central axis, and there is a remaining cladding between the isolation film and the core. Among the other 8 cores evenly arranged around the core on the central axis, an isolation film is provided for every other core, and there is a remaining cladding between the isolation film and the core.

[0048] The parameters of the 9 cores are exactly the same. The material and refractive index of the remaining cladding are the same as those of the common cladding. The material of the metal isolation film is gold.

[0049] In Embodiment 3 of the present invention, the key parameters can be selected as follows: the diameter of each core is 8 μm, the refractive index difference from the common cladding is 0.005. Except for the central core, the other 8 cores are evenly distributed on a circle with a radius of 12 μm from the center, and the center distance between the cores on the circle is 9.18 μm. The thickness of the gold isolation film is 0.01 μm, and it is adjacent to the edge of the adjacent core.

[0050] In summary, for the optical fiber structure described in the embodiments of the present invention, an extremely thin metal isolation film is surrounded outside one or more cores, and a certain thickness of cladding is retained between the metal isolation film and the core. The core regions separated by the metal isolation film are closely adjacent or have only a small interval. Among them, the metal isolation film can be selected within a relatively wide range. In addition to the preferred gold, other materials such as silver, copper, platinum, etc. can also be selected. The mode of surrounding the core with the metal isolation film has a good isolation effect on the core. At the same time, the thickness of the remaining cladding in the isolation film is relatively thin. Therefore, the cores can be close to each other while maintaining the low crosstalk characteristic, meeting the requirements of high core density and low inter-core crosstalk for multi-core optical fibers. The core structure described in the embodiments of the present invention has no requirements for the specific parameters of each core, and can provide high-density and low-crosstalk characteristics in the case of the same type of core, without affecting the complexity of the device and system.

[0051] Those of ordinary skill in the art can understand that the components in the device in the embodiments of the present invention can be distributed in the device according to the description of the embodiments, or can be correspondingly changed and located in one or more devices different from the present embodiment. The components of the above embodiments can be combined into one component, or further split into multiple sub-components.

[0052] As described above, it is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A multi-core optical fiber structure with an isolation film, comprising a common cladding (1) and at least two cores (2) uniformly wrapped in the common cladding (1), characterized in that: Two adjacent cores (2) are isolated from each other by coating an isolation film (3) on the outer side of one of the cores (2) or both cores (2), and there is a remaining cladding (4) between the isolation film (3) and the core (2); the material of the isolation film is a metal material; wherein, the material of the isolation film is gold; the thickness of the remaining cladding is less than the radius of the core; the thickness of the isolation film is less than the thickness of the remaining cladding; the material of the remaining cladding is the same as that of the common cladding; the refractive index of the core is higher than that of the common cladding, the refractive index of the remaining cladding is lower than that of the core, and the difference between the refractive index of the core and the refractive index of the common cladding is 0.

005.

2. The multi-core optical fiber structure with a separator film according to claim 1, characterized in that: The diameter of the core is 8 μm.

3. The multi-core optical fiber structure with a separator film according to claim 2, wherein: The thickness of the remaining cladding is 0.99 μm.

4. The multi-core optical fiber structure with a separator film according to claim 2, wherein: The thickness of the isolation film is 0.01 μm.

Images