CN112684538A - Square core optical fiber - Google Patents
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- CN112684538A CN112684538A CN202011607035.3A CN202011607035A CN112684538A CN 112684538 A CN112684538 A CN 112684538A CN 202011607035 A CN202011607035 A CN 202011607035A CN 112684538 A CN112684538 A CN 112684538A
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Abstract
The invention relates to a square core optical fiber, which comprises a core layer and a cladding layer, and is characterized in that the radial cross section of the core layer is rectangular, the length a of the rectangle is 9-400 mu m, the width b of the core layer is 3-400 mu m, the length-width ratio a/b of the rectangle is 1-12, and the relative refractive index difference delta 1 of the core layer is 0-2.2%. The invention has the beneficial effects that: the rectangular fiber core can improve the mode field matching and coupling efficiency between the optical fiber and the on-chip rectangular waveguide, and improve the mode division multiplexing performance of a few-mode and multi-mode optical fiber transmission system; the invention can be well matched with the mode of the output end of the semiconductor laser, can improve the coupling efficiency, and is widely applied to optical fiber beam combiner components of the semiconductor laser and the like. The length-width ratio and the core-spun ratio of the fiber core are easy to control, the attenuation of the optical fiber is reduced, and the fiber core has great advantages in meeting different application requirements.
Description
Technical Field
The invention relates to a square-core optical fiber, and belongs to the technical field of optical fibers.
Background
The optical fiber communication has the characteristics of large transmission capacity, long transmission distance, high transmission rate and the like, and is widely applied to optical communication networks such as long-distance trunk networks, metropolitan area networks, access networks and the like. The number of optical communication network users and new services of network data are continuously increasing driven by the demand of broadband data transmission services developing at a high speed. To meet the increasing demand for network capacity, optical communication systems employ various multiplexing techniques of optical signals in optical fibers, including Wavelength Division Multiplexing (WDM), Polarization Division Multiplexing (PDM), Frequency Division Multiplexing (FDM), and Time Division Multiplexing (TDM). However, the multiplexing technology of these dimensions is approaching the limit of transmission capacity, and the current optical communication system based on the common single mode optical fiber cannot meet the continuously increasing network capacity demand.
Space Division Multiplexing (SDM) technology, which is a novel optical multiplexing technology, is considered as a next-generation communication technology that solves the capacity problem of future optical communication systems. Space division multiplexing multiplexes multiple channels using spatial degrees of freedom of multiple conduction modes in a few-mode fiber, a multimode fiber, or a multi-core fiber, with the aim of improving the transmission capacity of a single-mode fiber. Among them, the implementation of spatial multiplexing using few-mode or multi-mode optical fibers is called Mode Division Multiplexing (MDM). In few-mode optical fiber and multi-mode optical fiber, linear polarization mode (LP mode) is mostly adopted for mode division multiplexing, under the ideal condition, all modes are mutually orthogonal and can be used as independent channels, and through carrying out multi-dimensional multiplexing with the traditional time, wavelength, polarization and multilevel modulation format, the transmission capacity of the system can be greatly increased. The difficulty of the few-mode and multi-mode optical fiber transmission system lies in the excitation of each mode, and the adoption of a planar optical waveguide (PLC) mode excitation method has the advantages of high integration level, high mode conversion efficiency, low insertion loss, mature planar optical waveguide technology, easy mass production, suitability for mode excitation and multiplexing and demultiplexing of a novel few-mode and multi-mode optical communication system, and wide application of a communication system built by combining a PLC device and a common single-mode optical fiber in each field of life. However, due to the limitation of the processing technology, the PLC and the silicon-based optoelectronic device with similar structure must be designed into a rectangular waveguide structure, and the supportable mode is a transverse electromagnetic mode (TEM mode).
However, both the conventional few-mode fiber and the conventional multimode fiber are designed into circular fiber cores to support the LP mode, but the fiber with the circular fiber core and the on-chip rectangular waveguide have the problem of mode field shape mismatch. In the single mode case, this problem is not significant, only affecting the connection loss, and not causing modal crosstalk. However, under the condition of few modes or multiple modes, severe mode field mismatch exists between the TEM mode of the on-chip rectangular waveguide and the high-order mode of the LP mode in the round core fiber, so that severe mode crosstalk and huge loss occur when the on-chip rectangular waveguide is connected with the round core fiber, and the performance of a few-mode or multi-mode optical communication system is seriously affected.
In addition, in the field of laser energy transmission, high-power semiconductor lasers are rapidly developed under the continuous push of laser processing application, have high output power and high brightness, and become the focus of attention of all countries in the world. Compared with other lasers, the semiconductor laser has many obvious advantages, and can be directly used in laser manufacturing fields such as laser welding, cladding, surface treatment and the like. Semiconductor laser optical fiber energy beam combination subassembly can high-efficient the output power who promotes semiconductor laser, compares with other semiconductor laser beam combination systems, and it has high efficiency, low cost, simple structure's advantage, is one of the latest hot spot in the present semiconductor laser beam combination research field. However, the optical fiber in the semiconductor laser optical fiber energy beam combining component is generally a traditional optical fiber, the fiber core structure of the traditional optical fiber is circular, the mode matching with the output end of the semiconductor laser is not good, the coupling efficiency is difficult to improve, and the application range of the semiconductor laser is limited.
Patent CN107132612A proposes a rectangular core optical fiber, which includes a fiber core with a rectangular cross section, a ravine layer with a rectangular cross section boundary, a refractive index buffer layer with a rectangular cross section boundary, and an outer cladding layer, where an absolute value of a refractive index difference between the outer cladding layer and the fiber core is less than 0.0005, and a long side length of the fiber core is 2 times a short side length, and the optical fiber has a larger fundamental mode field area under bending conditions, and a refractive index of the ravine layer is the smallest in each medium, so that a high-order mold in the fiber core has a larger transmission loss, and the fundamental mode transmission performance is better.
Disclosure of Invention
For convenience in describing the present disclosure, the following terms are defined:
length-width ratio of core: a/b is the ratio of the length a to the width b of the square core.
Radius of each layer of the optical fiber: ri is the distance from the outer edge of the ith layer of the fiber to the center of the fiber.
Core-spun ratio: B/A is the ratio of the diameter of the inner cladding of the optical fiber B to the diagonal A of the square core layer, wherein A is (a)2+b2)1/2，B＝2r2。
Relative refractive index difference: Δ i ═ (i th layer refractive index ni — outer cladding refractive index n 4)/outer cladding refractive index n4 × 100%, the relative refractive index difference of the layers with respect to the outer cladding.
The technical problem to be solved by the present invention is to provide a square core optical fiber for overcoming the above-mentioned shortcomings of the prior art, which can improve the mode field matching and coupling efficiency between the optical fiber and the on-chip rectangular waveguide, and improve the mode division multiplexing performance of few-mode and multi-mode optical fiber transmission systems.
The technical scheme adopted by the invention for solving the problems is as follows: the light-emitting diode comprises a core layer and a cladding layer, and is characterized in that the radial section of the core layer is rectangular (rectangular or square), the length a of the rectangle is 9-400 mu m, the width b of the core layer is 3-400 mu m, the length-width ratio a/b of the rectangle is 1-12, and the relative refractive index difference delta 1 of the core layer is 0-2.2%.
According to the scheme, the cladding comprises an inner cladding, an intermediate cladding and an outer cladding from inside to outside, the inner cladding is tightly wrapped on the periphery of the core layer, the inner boundary of the inner cladding is rectangular, the relative refractive index difference delta 2 of the inner cladding is-1.5% -0%, delta 2 is less than delta 1, and the core-cladding ratio B/A of the outer diameter of the inner cladding to the diagonal line of the core layer is 1.1-5.0.
According to the scheme, the middle cladding layer is coated on the periphery of the inner cladding layer, the relative refractive index difference delta 3 is-0.8% -0%, delta 2 is not less than delta 3 and not more than delta 4, and the outer cladding layer is a pure silicon dioxide layer or a fluorine-doped silicon dioxide layer.
According to the scheme, the attenuation of the optical fiber at the wavelength of 1550nm is 0.006 dB/m-0.012 dB/m.
According to the scheme, the radius r3 of the intermediate cladding is 20-450 μm, and the radius r4 of the outer cladding is 50-500 μm.
According to the scheme, the resin coating layer is coated outside the outer coating layer, and the resin coating layer comprises an inner coating layer and an outer coating layer.
The invention has the beneficial effects that: the rectangular fiber core can improve the mode field matching and coupling efficiency between the optical fiber and the on-chip rectangular waveguide, and improve the mode division multiplexing performance of a few-mode and multi-mode optical fiber transmission system; the invention can be well matched with the mode of the output end of the semiconductor laser, can improve the coupling efficiency, and is widely applied to optical fiber beam combiner components of the semiconductor laser and the like. The length-width ratio and the core-spun ratio of the fiber core are easy to control, the attenuation of the optical fiber is reduced, and the fiber core has great advantages in meeting different application requirements.
Drawings
FIG. 1 is a schematic radial structure of an optical fiber of the present invention.
FIG. 2 is a schematic diagram of the aspect ratio and core-clad ratio of an optical fiber of the present invention
FIG. 3 is a cross-sectional view of the refractive index of the optical fiber of the present invention.
FIG. 4 is a cross-sectional view of the refractive index of one embodiment of the present invention.
Fig. 5 is a cross-sectional view of the refractive index according to another embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples.
A first embodiment is shown in fig. 4, which is a square core optical fiber comprising a core layer 1, an inner cladding layer 2, an intermediate cladding layer 3, an outer cladding layer 4, and inner and outer resin-coated cladding layers 5 and 6; the core layer is rectangular (rectangle or square), the relative refractive index difference delta 1 of the core layer is 0% -0.3%, the length-width ratio a/b of the core layer is 2.0-3.0, the length a of the core layer is 16-30 mu m, the width b of the core layer is 5-15 mu m, the core layer is composed of silicon dioxide prepared by PCVD, and the silicon dioxide can be pure silicon dioxide, or is doped with germanium or fluorine, or is simultaneously doped with germanium and fluorine, or is doped with alkali metal added to one or two of germanium and fluorine; the inner cladding layer is coated on the core layer, the inner boundary of the inner cladding layer is rectangular, the relative refractive index difference delta 2 of the inner cladding layer is less than delta 1, delta 2 is-0.3% -0%, the core-spun ratio B/A of the outer diameter of the inner cladding layer and the diagonal line of the core layer is 2.0-3.0, the inner cladding layer is composed of silicon dioxide prepared by PCVD, and the silicon dioxide is doped with fluorine or fluorine and alkali metal; the intermediate cladding is coated on the inner cladding, the relative refractive index difference delta 3 of the intermediate cladding is between delta 2 and delta 4 (delta 3 is more than or equal to delta 2 and less than or equal to delta 4), delta 3 is-0.3% -0%, and the intermediate cladding is made of silicon dioxide prepared by PCVD, and the silicon dioxide is doped with fluorine; the outer cladding layer is coated on the middle cladding layer, the relative refractive index difference delta 4 of the outer cladding layer is more than or equal to delta 3, the outer cladding layer is made of pure silicon dioxide or fluorine-doped silicon dioxide, and the diameter of the outer cladding layer is 125 mu m. The inner coating layer and the outer coating layer are made of ultraviolet curing polymer resin which can be polyacrylic resin, polyimide or epoxy resin, the outer diameter of the inner coating layer is 194 mu m, and the outer diameter of the outer coating layer is 244 mu m. The attenuation of the square core optical fiber prepared by the embodiment is 0.006 dB/m-0.012 dB/m at the 1550nm wavelength, the length-width ratio and the core-wrapping ratio can be flexibly controlled, the mode field matching can be improved, the coupling efficiency can be improved, and the square core optical fiber has great advantages in meeting different application requirements of mode division multiplexing and semiconductor lasers. The specific parameters of a section of fiber in this example are shown in tables 1 and 2.
TABLE 1 optical fiber parameters of the first embodiment
TABLE 2 first embodiment fiber parameters
The second embodiment is shown in FIG. 5, and is different from the first embodiment in that the relative refractive index difference Δ 1 of the core layer is 0.3% -0.8%, the length-width ratio a/b of the core layer is 5.0-10.0, the length a of the core layer is 50-75 μm, the width b of the core layer is 5-15 μm, the core layer is composed of silica prepared by PCVD, and the silica is doped with germanium or simultaneously doped with germanium and fluorine or alkali metal; the inner cladding layer is coated on the core layer, the inner boundary of the inner cladding layer is rectangular, the relative refractive index difference delta 2 of the inner cladding layer is less than delta 1, delta 2 is-0.2% -0%, the core-spun ratio B/A of the outer diameter of the inner cladding layer and the diagonal line of the core layer is 3.0-5.0, the inner cladding layer is composed of silicon dioxide prepared by PCVD, and the silicon dioxide is doped with fluorine or fluorine and alkali metal; the intermediate cladding is coated on the inner cladding, the relative refractive index difference delta 3 is between delta 2 and delta 4 (delta 3 is more than or equal to delta 2 and less than or equal to delta 4), delta 3 is-0.2% -0%, and the intermediate cladding is made of silicon dioxide prepared by PCVD, and the silicon dioxide is doped with fluorine; the outer cladding layer is coated on the middle cladding layer, the relative refractive index difference delta 4 is more than or equal to delta 3, delta 4 is-0.2% -0%, the outer cladding layer is made of pure silicon dioxide or fluorine-doped silicon dioxide, and the diameter of the outer cladding layer is 125 microns. The square core optical fiber prepared by the embodiment has the wavelength of 1550nm ranging from 0.008dB/m to 0.020 dB/m. The specific parameters of a section of fiber in this example are shown in tables 3 and 4.
TABLE 3 fiber parameters of the second embodiment
TABLE 4 second embodiment fiber parameters
Claims (6)
1. A square core optical fiber comprises a core layer and a cladding layer, and is characterized in that the radial cross section of the core layer is rectangular, the length a of the rectangle is 9-400 mu m, the width b of the core layer is 3-400 mu m, the length-width ratio a/b of the rectangle is 1-12, and the relative refractive index difference delta 1 of the core layer is 0% -2.2%.
2. The square core optical fiber of claim 1, wherein said cladding comprises, from inside to outside, an inner cladding, an intermediate cladding and an outer cladding, said inner cladding being tightly wrapped around the core, and having a rectangular inner boundary, the relative refractive index difference Δ 2 of the inner cladding being-1.5% to 0%, and Δ 2 < Δ 1, and the cladding ratio B/a of the outer diameter of the inner cladding to the diagonal of the core being 1.1 to 5.0.
3. The square-core optical fiber of claim 2, wherein said intermediate cladding layer is coated on the outer periphery of the inner cladding layer, has a relative refractive index difference Δ 3 of-0.8% to 0% and Δ 2 ≤ Δ 3 ≤ Δ 4, and said outer cladding layer is a pure silica layer or a fluorine-doped silica layer.
4. The square-core optical fiber of claim 3, wherein said intermediate cladding radius r3 is 20 μm to 450 μm and said outer cladding radius r4 is 50 μm to 500 μm.
5. The square core optical fiber according to claim 1 or 2, wherein the optical fiber has an attenuation of 0.006dB/m to 0.012dB/m at a wavelength of 1550 nm.
6. A square core optical fiber according to claim 2 or 3, wherein a resin coating layer is coated on the outside of the outer clad layer, said resin coating layer comprising an inner coating layer and an outer coating layer.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114236674A (en) * | 2021-12-27 | 2022-03-25 | 江苏亨通光纤科技有限公司 | Ultrahigh-strength thin-diameter bending-resistant optical fiber |
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| CN109445019A (en) * | 2018-11-02 | 2019-03-08 | 北京大学 | A kind of rectangle core structure optical fiber |
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2020
- 2020-12-30 CN CN202011607035.3A patent/CN112684538B/en active Active
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| JP2009168914A (en) * | 2008-01-11 | 2009-07-30 | Mitsubishi Cable Ind Ltd | Optical fiber and method for manufacturing the same |
| JP2009169110A (en) * | 2008-01-16 | 2009-07-30 | Mitsubishi Cable Ind Ltd | Optical fiber |
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| CN107678086A (en) * | 2017-08-31 | 2018-02-09 | 北京航天控制仪器研究所 | A kind of optical fiber for realizing that Gauss beam reshaping is one-dimensional flat top beam |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114236674A (en) * | 2021-12-27 | 2022-03-25 | 江苏亨通光纤科技有限公司 | Ultrahigh-strength thin-diameter bending-resistant optical fiber |
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