Multi-mode and single-mode multi-core composite communication optical fiber

Abstract

The utility model discloses a multi-mode and single-mode multi-core composite communication optical fiber, which comprises a multi-mode fiber core, a plurality of single-mode fiber cores and a wrapping layer, the wrapping layer wraps the outer sides of the multi-mode fiber core and the single-mode fiber cores, and the single-mode fiber cores are uniformly distributed at intervals around a circle where the center of the multi-mode fiber core is located. The multi-mode fiber core comprises step type refractive index profile distribution or gradient type refractive index profile distribution, the refractive index difference between the multi-mode fiber core and the cladding is # imgabs0 # and # imgabs1 #, the refractive index difference between the single-mode fiber core and the cladding is # imgabs2 # and # imgabs3 #, # imgabs4 # is the refractive index of the cladding, # imgabs5 # is the refractive index of the multi-mode fiber core, and # imgabs6 # is the refractive index of the single-mode fiber core. The manufacturing method comprises the following steps: manufacturing a preform by using an MCVD (modified chemical vapor deposition) process, manufacturing a germanium-doped core rod by using a VAD (vapor deposition) process, and drawing optical fibers. Through the mode, the multi-mode and single-mode multi-core composite communication optical fiber can be used as a multi-mode optical fiber and a multi-core single-mode optical fiber at the same time, the application scene is expanded, and the service life is long.

Description

Technical Field

[0001] The utility model relates to the field of optical fibers, in particular to a multi-mode, single-mode multi-core composite communication optical fiber. Background Art

[0002] At present, the key developments in space division multiplexing are multi-core fiber (MCF) and mode division multiplexing (MDM). Mode division multiplexing is further divided into linear polarization mode (LP) mode division multiplexing in few-mode fiber (FMF) and orbital angular momentum (OAM) mode division multiplexing.

[0003] An optical fiber that can accommodate multiple optical waveguide cores in one optical fiber. It can be divided into two types; one is a fiber with fewer cores, a larger distance between cores, and smaller optical field coupling between cores. The crosstalk interference between cores is small, and this type of MCF is called weak coupling MFC; the other type is a fiber with more cores, a smaller distance between cores, and stronger optical field coupling between cores. The crosstalk interference between cores is large, and this type of MCF is called strong coupling MFC. Strong coupling MFC needs to adopt a similar mode multiplexing method to eliminate the crosstalk interference between cores. It should be pointed out that each core in a multi-core optical fiber can also be used as a few-mode optical fiber to realize mode division multiplexing. In other words, the two can be combined to realize N*M parallel transmission channels combining M-core MCF and N-mode FMF. Summary of the invention

[0004] The main technical problem solved by the utility model is to provide a multi-mode, single-mode multi-core composite communication optical fiber, which can be used as a multi-mode optical fiber and a multi-core single-mode optical fiber at the same time, thereby expanding the application scenarios and extending the service life.

[0005] In order to solve the above technical problems, a technical solution adopted by the utility model is: to provide a multi-mode, single-mode multi-core composite communication optical fiber, including a multi-mode fiber core, a plurality of single-mode fiber cores and a cladding, wherein the cladding is coated on the outside of the multi-mode fiber core and the single-mode fiber core, and the single-mode fiber cores are evenly distributed around the circle where the center of the multi-mode fiber core is located, and the multi-mode fiber core includes a step-type refractive index profile distribution or a gradient-type refractive index profile distribution, and the refractive index difference between the multi-mode fiber core and the cladding is , , the refractive index difference between the single-mode core and the cladding is , ,in is the cladding refractive index, is the multimode core refractive index, is the single-mode fiber core refractive index.

[0006] In a preferred embodiment of the present invention, the core diameter of the single-mode fiber core is smaller than the core diameter of the multi-mode fiber core.

[0007] In a preferred embodiment of the present invention, the core diameter of the single-mode fiber core is 8.3 μm, the core diameter of the multi-mode fiber core is 50 μm, and the diameter of the cladding is 125 μm.

[0008] In a preferred embodiment of the present invention, the number of the single-mode fiber cores is 6.

[0009] In order to solve the above technical problems, another technical solution adopted by the utility model is: to provide a preparation process of a multi-mode, single-mode multi-core composite communication optical fiber, characterized in that it includes the following steps:

[0010] a. Make preform rods by using MCVD process: Place the quartz substrate tube on the glass lathe and rotate it. Use ultra-pure oxygen as carrier gas to enter the quartz substrate tube together with saturated steam of SiCl4 and GeCl4. The outer wall of the quartz substrate tube is heated by hydrogen-oxygen flame at a temperature of 1400-1600℃. The gas phase material in the tube undergoes oxidation reaction at high temperature through heat conduction. The generated oxide forms a porous glass dust deposition layer on the inner wall of the tube downstream of the high temperature zone. When the high temperature zone of the next wave of hydrogen-oxygen flame passes through this place, the glass dust is Sintering into a uniform transparent glass layer deposited on the inner wall, the hydrogen-oxygen torch slowly moves from left to right once to form a corresponding deposition layer, and then quickly returns to the original position to perform a second deposition, and repeats this process until the required deposition is completed; the quartz substrate tube will serve as the outer cladding part, and the deposition layer will be deposited layer by layer from the cladding to the fiber core. When the deposition is completed, there is still a small hole in the center, and the preform enters the shrinking stage, the raw material gas flow is stopped, and the flame temperature rises to about 1800℃, and the quartz tube is shrunk to form a solid optical fiber preform;

[0011] b. Use VAD process to make germanium-doped core rod: Purified air is introduced into the reaction vessel, and the exhaust pump on the reaction vessel is working to ensure the internal pressure is stable. The quartz rod after the deposition starts is lifted upward, and the starting target rod is lifted vertically. The oxide glass is deposited on the lower end of the target rod, so that the deposition surface is always kept in a certain position. The core and cladding materials are deposited on the rod at the same time. Finally, the porous mother material is dehydrated in a separate process and sintered into a transparent germanium-doped core rod;

[0012] c. Drawing the optical fiber preform obtained in step a into a 50 mm preform, drilling holes at the positions corresponding to the single-mode optical fiber cores, and then inserting the germanium-doped core rod obtained in step b into the holes;

[0013] d. Fiber drawing process: Insert the fiber preform into the drawing furnace for high-temperature drawing at 2200℃ to form the optical fiber. After the optical fiber is drawn, plastic resin is directly coated on the drawing tower to protect the optical fiber.

[0014] In a preferred embodiment of the present invention, the reaction formula of the oxidation reaction of the gas phase material in the tube at high temperature in step a is: SiCl4+O2→SiO2+2Cl2↑; GeCl4+O2→GeO2+2Cl2↑.

[0015] In a preferred embodiment of the present invention, the chlorine gas generated by the reaction during the deposition process in step a and the gas phase material that has not reacted completely are discharged from the outlet of the quartz substrate tube for waste gas neutralization treatment.

[0016] In a preferred embodiment of the present invention, the refractive index profile in step a is controlled by adjusting the flow rate of the carrier gas of each raw material composition using a mass flow controller.

[0017] In a preferred embodiment of the present invention, in step b, three deposition torches are used simultaneously to deposit the germanium-doped fiber core to improve deposition efficiency, and the position deviation of the deposition end should be controlled within an accuracy of 50 μm.

[0018] In a preferred embodiment of the utility model, in order to reduce the microbending loss of the optical fiber in step d, the coating is usually divided into two layers, the coating diameter is 242±5µm, and the coating is divided into inner and outer layers. The inner coating diameter is 180-190µm, and the inner coating needs to use a coating with a low Young's modulus to improve the anti-microbending performance of the optical fiber, and the Young's modulus of the inner coating is 0.5-2MPa; the outer coating uses a coating with a higher Young's modulus to increase the mechanical and environmental protection performance of the optical fiber, and the Young's modulus of the outer coating should be greater than 600MPa, and UV-curable acrylic resin is used as the coating material.

[0019] The beneficial effects of the utility model are as follows: the multi-mode, single-mode multi-core composite communication optical fiber of the utility model can be used as a multi-mode optical fiber and a multi-core single-mode optical fiber at the same time, and can directly replace the equipment applicable to the new single-mode and multi-mode dual-purpose communication optical fiber without replacing the optical fiber and rewiring, and has a long service life, and is suitable for the mutual updating and replacement of single-mode and multi-mode equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0021] Figure 1 It is a structural schematic diagram of a preferred embodiment of the multi-mode and single-mode multi-core composite communication optical fiber of the utility model;

[0022] Figure 2It is the refractive index profile distribution diagram of multi-mode and single-mode multi-core composite communication optical fiber;

[0023] Figure 3 It is a process flow chart for preparing multi-mode and single-mode multi-core composite communication optical fiber;

[0024] Figure 4 is a schematic diagram of the MCVD process;

[0025] Figure 5 It is a schematic diagram of the VAD process;

[0026] Figure 6 This is the curve of the change of the refractive index of SiO2 due to doping;

[0027] The components in the accompanying drawings are marked as follows: 1. multi-mode fiber core, 2. single-mode fiber core, 3. cladding. DETAILED DESCRIPTION

[0028] The technical scheme in the embodiment of the utility model will be described clearly and completely below. The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification, so that people familiar with this technology can understand and read them, and are not used to limit the limiting conditions that can be implemented in the utility model, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect that can be produced by the utility model and the purpose that can be achieved, should still fall within the scope that the technical content disclosed in the utility model can cover. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on quoted in this specification are only for the convenience of narration, and are not used to limit the scope that can be implemented. The change or adjustment of the relative relationship, without substantial change of the technical content, should also be regarded as the scope that can be implemented in the utility model.

[0029] See also Figures 1 to 6 A multi-mode, single-mode multi-core composite communication optical fiber, comprising a multi-mode core 1, a plurality of single-mode cores 2 and a cladding 3, wherein the cladding 3 is coated on the outside of the multi-mode core 1 and the single-mode core 2, and the single-mode cores 2 are evenly distributed around the circle where the center of the multi-mode core 1 is located. The number of single-mode cores 2 is 6. The multi-core single-mode optical fiber structure in the utility model is a typical six-core structure, but is not limited to a six-core structure.

[0030] The refractive index difference between the multimode core 1 and the cladding 3 is , The core diameter of the multimode fiber core 1 is 50 μm, and the diameter of the cladding 3 is 125 μm. The multimode fiber core 1 includes a step-type refractive index profile distribution or a gradient-type refractive index profile distribution, and the gradient-type refractive index profile curve is a parabola.

[0031] The refractive index difference between the single-mode core 2 and the cladding 3 is , The core diameter of the single-mode fiber core 2 is 8.3 μm, and when the operating wavelength is 1310 nm, the mode field diameter is 8.6-9.2 μm; the cut-off wavelength is 1260 nm; and the zero dispersion wavelength is 1300-1324 nm.

[0032] The above is the cladding refractive index, is the multimode core refractive index, is the single-mode fiber core refractive index.

[0033] A preparation process of a multi-mode, single-mode multi-core composite communication optical fiber, comprising the following steps:

[0034] Optical fiber preform:

[0035] The process of optical fiber is more complicated, but it also needs to start with the preparation of conventional optical fiber preform rods. The first step is to use MCVD or PCVD process to make preform rods, the second step is to use VAD process to make germanium-doped glass core rods, the third step is to melt and shrink the preform rods into 50mm preform rods, and six holes are punched at the position of the single-mode optical fiber core wire. The fourth step is to insert the germanium-doped core rod into the holes, and the fifth step is to draw the preform rod as a whole to form an optical fiber. The process flow is as follows: Figure 3 shown.

[0036] Preform production process

[0037] The optical fiber preform can be made by the common MCVD process or PCVD process. Figure 5 The MCVD process shown is described as follows:

[0038] MCVD is a classic optical fiber preform manufacturing method developed by AT&T Bell Labs in 1974. It is an in-tube vapor deposition process. The process is as follows: a quartz substrate tube is placed on a glass lathe and rotated. Ultrapure oxygen is used as a carrier gas through a bubble bottle (bubble) containing pure chemical raw materials such as SiCl4 and GeCl4. O2 is used as a carrier gas to bring the saturated vapor of SiCl4 and GeCl4 into the quartz substrate tube. When the outer wall of the quartz substrate tube is heated by an oxyhydrogen flame at a temperature of 1400-1600oC, the gas phase material in the tube undergoes an oxidation reaction at high temperature through heat conduction. The reaction formula is:

[0039] SiCl4+O4→SiO2+2Cl2↑

[0040] GeCl4+O2→GeO2+2Cl2↑

[0041] The generated oxides such as SiO2 and GeO2 form a porous glass dust deposition layer on the inner wall of the tube downstream of the high-temperature zone. When the high-temperature zone of the next wave of hydrogen-oxygen flame passes through this place, the glass dust is sintered into a uniform transparent glass layer deposited on the inner wall (such as Figure 6 As shown in the figure, the oxyhydrogen torch moves slowly from left to right to form a corresponding deposition layer, then quickly returns to its original position to perform a second deposition, and repeats this process until the prescribed deposition is completed.

[0042] The chlorine gas produced by the reaction and the gaseous materials that have not reacted completely are discharged from the outlet of the quartz substrate tube for waste gas neutralization treatment. The quartz substrate tube will serve as the outer cladding part. The deposition layer is deposited layer by layer from the cladding to the core. In the matrix of silica, its refractive index can be changed by a small amount of doping. Doping GeO2 helps to increase the refractive index.

[0043] In the matrix of silicon dioxide, its refractive index can be changed by a small amount of doping. Figure 6 It shows the refractive index of doped silica as a function of the doping amount. As can be seen from the figure, doping with GeO2 and P2O5 helps to increase the refractive index, while doping with fluorine reduces the refractive index. For example, the refractive index of pure silica as the cladding is 1.458, and the refractive index of the core doped with three percent GeO2 increases to 1.463, which is the refractive index profile of the G.652 matched single-mode optical fiber.

[0044] 2. Germanium-doped core rod manufacturing process

[0045] Using VAD process to make germanium-doped core rod: VAD is a fiber preform manufacturing technology developed by Japan's NTT Lab in 1997 to avoid patent disputes with Corning. Its principle is the same as that of OVD, which is also to generate oxide glass by flame hydrolysis. However, there are two main differences from OVD: first, the starting target rod is lifted vertically, and the oxide glass is deposited at the lower end of the target rod; second, the core and cladding materials are deposited on the rod at the same time, and the formation of the refractive index profile of the preform is achieved through the temperature distribution of the deposition part, the position and angle of the hydrogen-oxygen flame torch, and the control of the gas flow density of the raw gas.

[0046] In principle, the porous mother material of the preform formed by VAD deposition can be lifted up to achieve dehydration, sintering, and even direct drawing into fibers. Such a continuous optical fiber forming process with unlimited manufacturing length is potentially possible. However, in practice, the porous mother material is usually still dehydrated and sintered in separate processes to form an optical fiber preform.

[0047] The molding process of VAD method is as follows Figure 5As shown, after the deposition starts, the quartz rod is lifted upward so that the deposition surface is always kept at a certain position. The entire reaction is carried out in a container. The stability of the flame is ensured by constant exhaust. When making a germanium-doped fiber core preform rod for optical fiber, three deposition torches are used to deposit the germanium-doped fiber core at the same time to improve the deposition efficiency. Finally, the prepared porous mother material is dehydrated in a separate process and sintered into a transparent quartz preform rod.

[0048] The process principles of VAD and OVD are the same, except that the lateral side deposition of OVD is changed to axial end deposition. Therefore, some process principles of OVD are also basically applicable to VAD. However, due to the characteristics of VAD end deposition, its process control is more stringent than OVD. The key to VAD is that the process conditions must be strictly controlled, including precise control of the raw material flow rate, the exhaust gas flow rate, the flame temperature, the surface temperature and rotation speed of the deposited body, and the position of the end of the deposited body, so as to achieve the production of a uniform and stable preform rod matrix. Slight fluctuations in the position of the deposited end of the deposited body will cause changes in the outer diameter and refractive index profile of the matrix. Therefore, the position deviation of the deposited end should be controlled within an accuracy of 50μm. This can be controlled by the positioning signal given by the video camera. The structural design of the torch is also one of the keys in the VAD process. The flow rate of multiple material flows in the torch, the stable state of the flame and the hydrolysis reaction in the spatial distribution are of great importance to the final preform rod. The change in the doping amount of GeO2 has been discussed in detail in the previous section of the MCVD process and will not be repeated here.

[0049] The glass preform is inserted into a drawing furnace for high-temperature drawing at 2200°C to form an optical fiber. The drawing tension is set to 30-45g. The optical fiber formed by these processing parameters is less susceptible to the stress induced by drawing, which is unfavorable to the optical transmission properties of the optical fiber (including waveguide propagation performance). After the optical fiber is drawn and formed, a plastic resin is directly coated on the drawing tower to protect the optical fiber. In order to reduce the microbending loss of the optical fiber, it is usually coated in two layers, with a coating diameter of 242±5µm, and the coating is divided into inner and outer layers. The inner coating diameter is 180-190µm, and the inner coating needs to use a coating with a low Young's modulus to improve the microbending resistance of the optical fiber. The Young's modulus of the inner coating is 0.5-2MPa, and the outer coating uses a coating with a higher Young's modulus to increase the mechanical and environmental protection performance of the optical fiber. The Young's modulus of the outer coating should be greater than 600MPa.

[0050] UV-curable acrylic resin is generally used as the coating material.

[0051] Different from the prior art, the multi-mode, single-mode multi-core composite communication optical fiber of the utility model can be used as a multi-mode optical fiber and a multi-core single-mode optical fiber at the same time, which expands the application scenarios and prolongs the service life.

[0052] The above schematically describes the present invention and its implementation methods, which are not restrictive. The drawings show only one implementation method of the present invention, and the actual structure is not limited thereto. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A multi-mode, single-mode multi-core composite communication optical fiber, characterized in that: The invention comprises a multimode fiber core, a plurality of single-mode fiber cores and a cladding, wherein the cladding is coated on the outside of the multimode fiber core and the single-mode fiber core, the single-mode fiber cores are evenly distributed around the circle where the center of the multimode fiber core is located, the multimode fiber core comprises a step-type refractive index profile distribution or a gradient-type refractive index profile distribution, and the refractive index difference between the multimode fiber core and the cladding is , , the refractive index difference between the single-mode core and the cladding is , ,in is the cladding refractive index, is the multimode core refractive index, is the single-mode fiber core refractive index.

2. The multi-mode, single-mode multi-core composite communication optical fiber according to claim 1, characterized in that: The core diameter of the single-mode fiber core is smaller than the core diameter of the multi-mode fiber core.

3. The multi-mode, single-mode multi-core composite communication optical fiber according to claim 2, characterized in that: The core diameter of the single-mode fiber core is 8.3 μm, the core diameter of the multi-mode fiber core is 50 μm, and the diameter of the cladding is 125 μm.

4. The multi-mode, single-mode multi-core composite communication optical fiber according to claim 3, characterized in that: The number of the single-mode fiber cores is 6.

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