Multimode optical fiber suitable for vehicle-mounted optical communication system

Abstract

The invention relates to a multimode optical fiber suitable for a vehicle-mounted optical communication system, which comprises a core layer and a cladding, the core layer comprises a main core layer and an auxiliary core layer coated outside the main core layer, the radius of the main core layer is 21.0-26.0 mu m, the refractive index profile of the main core layer is in gradient refractive index distribution, alpha is 1.80-2.20, the maximum relative refractive index difference value n1 of the main core layer is 0.5%-0.6%, the radius of the auxiliary core layer is 35-40 mu m, and the thickness of the auxiliary core layer is 0.5-0.8 mm. The refractive index section of the auxiliary core layer is an oblique line, the included angle A between the oblique line and the transverse axis is 50-85, the minimum relative refractive index difference n2 of the auxiliary core layer is-0.30%-0.40%, the cladding layer is divided into a sunken inner cladding layer and an outer cladding layer from inside to outside in sequence, the radius of the sunken inner cladding layer is 90-100 micrometers, the relative refractive index difference n3 of the sunken inner cladding layer is-0.9%-1.1%, the outer cladding layer is a pure silicon dioxide glass layer, and the thickness of the pure silicon dioxide glass layer is 1-10 micrometers. And the radius of the outer cladding layer is 62.5 microns. The double-window high-bandwidth optical fiber can meet the double-window high-bandwidth requirements of 850nm and 980nm at the same time, has the characteristics of low loss, low macrobend loss and high temperature resistance, and is suitable for a vehicle-mounted optical communication system.

Description

TECHNICAL FIELD

[0001] The present application relates to a multimode optical fiber suitable for a vehicle-mounted optical communication system, and belongs to the technical field of optical communication. BACKGROUND

[0002] At present, the global automobile industry is undergoing the most profound change in a century. The electric and intelligent technologies of automobiles are developing rapidly. The large number of electronic components and the super large capacity of batteries make the design of electromagnetic shielding of the whole vehicle more and more complex. At the same time, the use of a large number of in-vehicle and out-vehicle cameras, various radars, vehicle-mounted artificial intelligence and other applications will increase the data communication rate in the vehicle to 10, 25, 50 Gbps or even higher. Therefore, the traditional carrier of automobile communication, copper wire, cannot support the demand of vehicle-mounted high-speed communication. The quartz optical fiber with the advantages of high bandwidth, low loss, no crosstalk, no electromagnetic interference, small size and low weight, etc. begins to enter the automobile field and opens a new round of "optical replacing copper" in the automobile industry.

[0003] The communication window of the conventional multimode optical fiber is generally 850 nm, and the bandwidth optimization is also for the 850 nm window. However, according to the recommendation of IEEE 802.3cz, the window of vehicle-mounted optical communication is 850 nm and 980 nm. The existing conventional multimode optical fiber cannot meet the bandwidth requirements of 850 nm and 980 nm at the same time. Generally, there are two ways to improve the bandwidth of the optical fiber. One is to accurately control the flow meter to make the cross-sectional profile of the optical fiber more smooth, reduce the intermodal dispersion of the optical fiber, and thus improve the bandwidth. The other is to reduce the doping concentration of germanium in the core layer to improve the material dispersion of the optical fiber, reduce the chromatic dispersion, and further improve the bandwidth of the optical fiber. Patent PCT / CN2019 / 082239 discloses a method for improving the bandwidth of a multimode optical fiber. By increasing the phosphorus concentration in the optical fiber and reducing the germanium concentration, the dispersion of the optical fiber is reduced and the bandwidth is improved. However, the above-mentioned method for manufacturing the optical fiber introduces a new dopant P element, which increases the control difficulty of actual production, and the optical fiber is designed and optimized for the bandwidth of 850 nm and 950 nm, and does not consider the bandwidth of 980 nm. SUMMARY

[0004] For the convenience of introducing the content of the present application, some terms are defined as follows: Relative refractive index difference of each layer of the optical fiber defined by the following equation: , wherein n i is the refractive index of the core, and n c is the refractive index of the cladding, i.e. the refractive index of pure silica.

[0005] The technical problem solved by the present application is to provide a multimode optical fiber suitable for a vehicle-mounted optical communication system, which can simultaneously meet the bandwidth requirements of 850 nm and 980 nm and satisfy the demand of vehicle-mounted communication double-window communication.

[0006] The technical scheme adopted by the present application to solve the above-mentioned problems is: comprising a core layer and a cladding layer, characterized in that the core layer comprises a main core layer and an auxiliary core layer covering the outside of the main core layer, the radius of the main core layer is 21.0-26.0 μm, the refractive index profile of the main core layer is a graded refractive index distribution, the refractive index distribution index α is 1.80-2.20, the maximum relative refractive index difference Δn1 of the main core layer is 0.5%-0.6%, and the minimum relative refractive index difference is 0, the radius of the auxiliary core layer is 35-40 μm, the refractive index profile of the auxiliary core layer is a straight line, which extends downward from the edge of the main core layer, the included angle A between the straight line and the horizontal axis is 50º-85º, the minimum relative refractive index difference Δn2 of the auxiliary core layer is-0.30%--0.40%, the cladding layer is sequentially divided into a sunken inner cladding layer and an outer cladding layer from the inside, the radius of the sunken inner cladding layer is 90-100 μm, and the relative refractive index difference Δn3 is-0.9%--1.1%, and the outer cladding layer is a pure silica glass layer, and the radius of the outer cladding layer is 62.5 μm.

[0007] According to the above scheme, the relative refractive index difference inside the sunken inner cladding layer is in a stepwise decreasing manner.

[0008] According to the above scheme, the relative refractive index difference inside the sunken inner cladding layer is in a two-step stepwise decreasing manner, comprising a first step layer and a second step layer, the relative refractive index difference Δn3.1 of the first step layer is-0.5%--0.6%, and the single-side radial thickness is 2 µm-4 µm, and the relative refractive index difference Δn3.2 of the second step layer is-0.7%--0.8%, and the single-side radial thickness is 2 µm-4 µm.

[0009] According to the above scheme, the included angle A between the refractive index profile of the auxiliary core layer and the horizontal axis is 55º-80º.

[0010] According to the above scheme, the core layer is a fluorine and germanium co-doped silica glass layer, and the sunken inner cladding layer is a fluorine-doped silica glass layer.

[0011] According to the above scheme, the effective mode bandwidth of the optical fiber at a wavelength of 850 nm is ≥2000 MHz·km.

[0012] According to the above scheme, the effective mode bandwidth of the optical fiber at a wavelength of 980 nm is ≥1500 MHz·km.

[0013] According to the above scheme, the optical fiber has a loss of ≤2.3 dB / km at a wavelength of 850 nm and a loss of ≤1.5 dB / km at a wavelength of 980 nm.

[0014] According to the above scheme, the macro-bending loss of the optical fiber is 2 turns of radius 15 mm ≤0.1 dB / km @ 850 nm, 2 turns of radius 15 mm ≤0.24 dB / km @ 980 nm, 2 turns of radius 7.5 mm ≤0.2 dB / km @ 850 nm, and 2 turns of radius 7.5 mm ≤0.4 dB / km @ 980 nm.

[0015] According to the above scheme, the typical value of the fusion loss of the optical fiber is 0.1 dB.

[0016] The present application has the following advantages: 1. The auxiliary core layer with a refractive index profile of a straight line is provided, and the core layer with a relatively lower refractive index is introduced at the edge of the core layer, so that the delay at the edge of the core layer can be appropriately accelerated, the delay slowing down of 980 nm at the edge of the core layer is relatively offset, the bandwidth of the 980 nm window is optimized, the multimode optical fiber can meet the dual-window high-bandwidth requirements of 850 nm (effective mode bandwidth ≥2000 MHz·km) and 980 nm (effective mode bandwidth ≥1500 MHz·km) at the same time, and has low loss, low macro-bending loss and high-temperature resistance, and is suitable for vehicle-mounted optical communication systems. 2. The stepped design is adopted for the lower inner cladding of the present application, including a first stepped layer and a second stepped layer. The multi-stage stepped lower inner cladding structure, especially the introduction of the first and second stepped layers, can effectively modulate the light field. When the Gaussian distribution light field from the VCSEL laser passes through the optical fiber, the two precisely controlled refractive index steps will introduce specific mode coupling and interference, so as to scatter and redistribute the concentrated light power, and realize the homogenization of the light spot. This is very important for the uniform distribution of light intensity of the optical splitter in the multimode PON network, and can meet the application requirements of the multimode optical splitter. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of the relative refractive index difference profile of an embodiment of the present application.

[0018] Figure 2 is a schematic diagram of the radial cross-sectional structure of an embodiment of the present application.

[0019] Figure 3 、 Figure 4 are columnar comparison diagrams of the light field distribution of the homogenization effect of the light spot of the ordinary multimode optical fiber and the multimode optical fiber of the present application, respectively.

[0020] Figure 5 is a comparison diagram of the dual-window bandwidth of the multimode optical fiber of the present application and the dual-window bandwidth of the ordinary multimode optical fiber.

[0021] Figure 6 is a schematic diagram of the application of the multimode optical fiber in the vehicle-mounted PON network communication architecture. DETAILED DESCRIPTION

[0022] The application will be further described below in conjunction with the embodiments and the accompanying drawings.

[0023] The multimode optical fiber of the application comprises a core layer and a cladding layer, the core layer comprises a main core layer 1 and an auxiliary core layer 2 covering the outside of the main core layer, the radius of the main core layer is 21.0-26.0 μm, the refractive index profile of the main core layer is a graded refractive index distribution, the refractive index distribution index α is 1.80-2.20, the maximum relative refractive index difference Δn1 of the main core layer is 0.5%-0.6%, and the minimum relative refractive index difference is 0, the radius of the auxiliary core layer is 35-40 μm, the refractive index profile of the auxiliary core layer is a straight line, which extends downward from the edge of the main core layer, the included angle A between the straight line and the horizontal axis is 50º-85º, the minimum relative refractive index difference Δn2 of the auxiliary core layer is -0.30%--0.40%, the cladding layer is sequentially divided into a sunken inner cladding layer 3 and an outer cladding layer 4 from the inside, the radius of the sunken inner cladding layer is 90-100 μm, and the relative refractive index difference Δn3 is -0.9%--1.1%, the relative refractive index difference inside the sunken inner cladding layer is in a two-step ladder decreasing shape, comprising a first step layer and a second step layer, and the outer cladding layer is a pure silica glass layer, and the radius of the outer cladding layer is 62.5 μm.

[0024] Table 1 is the structure parameters and performance test parameters of the five embodiments of the application.

[0025] Table 1

[0026] The application scenario of the vehicle-mounted optical fiber of the application includes: network structure: the vehicle-mounted network adopts a PON architecture, mainly including a domain controller (OLT) located at the upstream, a splitter located at the middle stream, and various terminal devices such as a camera, a laser radar, and a millimeter wave radar (ONU) located at the downstream. The multimode optical fiber of the application is used as a transmission medium to connect the domain controller and the splitter, and the splitter and each sensor terminal. The multimode optical fiber of the application has a high bandwidth at 850 nm and 980 nm, and supports a data communication demand of up to 10 Gbps, 25 Gbps or even higher in the vehicle. Since the optical fiber of the application has a specific multi-step ladder-shaped sunken inner cladding layer structure, it can realize spot homogenization through mode coupling, ensure that the light intensity can be uniformly distributed to each sensor (ONU) after passing through the splitter, and thus meet the stringent requirements of the multimode PON network on light power distribution.

Claims

1. A multimode optical fiber suitable for vehicle-mounted optical communication systems, comprising a core layer and a cladding layer, characterized in that... The core layer comprises a main core layer and an auxiliary core layer covering it. The main core layer has a radius of 21.0~26.0 μm, and its refractive index profile exhibits a graded refractive index distribution with a refractive index distribution index α of 1.80~2.

20. The maximum relative refractive index difference Δn1 of the main core layer is 0.5%~0.6%, and the minimum relative refractive index difference is 0. The auxiliary core layer has a radius of 35~40 μm, and its refractive index profile is a diagonal line extending from the main core layer. The edge extends downwards at an angle A of 50º to 85º with the horizontal axis. The minimum relative refractive index difference Δn2 of the auxiliary core layer is -0.30% to -0.40%. The cladding is divided into a recessed inner cladding and an outer cladding from the inside out. The radius of the recessed inner cladding is 90 to 100 μm, and the relative refractive index difference Δn3 is -0.9% to -1.1%. The outer cladding is a pure silica glass layer with a radius of 62.5 μm.

2. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1, characterized in that... The relative refractive index difference inside the recessed inner cladding decreases in a stepwise manner.

3. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 2, characterized in that... The relative refractive index difference inside the recessed inner cladding exhibits a two-step decreasing pattern, comprising a first step layer and a second step layer. The relative refractive index difference Δn3.1 of the first step layer is -0.5% to -0.6%, and the radial thickness on one side is 2µm to 4µm. The relative refractive index difference Δn3.2 of the second step layer is -0.7% to -0.8%, and the radial thickness on one side is 2µm to 4µm.

4. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1 or 2, characterized in that... The angle A between the refractive index profile of the auxiliary core layer and the horizontal axis is 55º~80º.

5. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1 or 2, characterized in that... The core layer is a fluorine- and germanium-doped silica glass layer, and the recessed inner cladding is a fluorine-doped silica glass layer.

6. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1 or 2, characterized in that... The optical fiber has an effective mode bandwidth of ≥2000MHz·km at a wavelength of 850nm.

7. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1, characterized in that... The optical fiber has an effective mode bandwidth of ≥1500MHz·km at a wavelength of 980nm.

8. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1 or 2, characterized in that... The optical fiber has a loss of ≤2.3dB / km at a wavelength of 850nm and a loss of ≤1.5dB / km at a wavelength of 980nm.

9. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1 or 2, characterized in that... The macrobending loss of the optical fiber is ≤0.1dB / km@850nm for 2 turns with a radius of 15mm, ≤0.24dB / km@980nm for 2 turns with a radius of 15mm, ≤0.2dB / km@850nm for 2 turns with a radius of 7.5mm, and ≤0.4dB / km@980nm for 2 turns with a radius of 7.5mm.

10. The multimode optical fiber suitable for vehicle-mounted optical communication systems according to claim 1, characterized in that... The typical value for the splice loss of the optical fiber is 0.1 dB.

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