CN109061799B - Mode converter based on fine core fiber Bragg grating - Google Patents

Mode converter based on fine core fiber Bragg grating Download PDF

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CN109061799B
CN109061799B CN201810947750.8A CN201810947750A CN109061799B CN 109061799 B CN109061799 B CN 109061799B CN 201810947750 A CN201810947750 A CN 201810947750A CN 109061799 B CN109061799 B CN 109061799B
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fiber
mode
core
fine
core fiber
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CN109061799A (en
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杨杭洲
张攀
丁相梓
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Northwestern University
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/14—Mode converters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
    • G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/124—Geodesic lenses or integrated gratings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12083—Constructional arrangements
    • G02B2006/12107—Grating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12133—Functions
    • G02B2006/12152—Mode converter

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Optical Communication System (AREA)

Abstract

A mode converter based on a fine core fiber Bragg grating is characterized in that a first single mode fiber, a first fine core fiber and a second fine core fiber are spliced in sequence, the diameter of the first single mode fiber is larger than that of the first fine core fiber and that of the second fine core fiber, and Bragg gratings are engraved on the fiber core of the second fine core fiber. The invention adopts the first single mode fiber, the first thin core fiber and the second thin core fiber which are spliced in sequence, and the fiber core of the second thin core fiber is inscribed with the Bragg grating, thereby realizing LP01And LP11The mode converter has the advantages of simple manufacture, low cost, low mode crosstalk and small insertion loss, and can be used as a mode converter based on the thin-core fiber Bragg grating in a long-distance low-loss transmission mode division multiplexing system.

Description

Mode converter based on fine core fiber Bragg grating
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a mode converter based on a fine-core fiber Bragg grating.
Background
With the rapid development of computers and the continuous rise of emerging industries such as big data, cloud computing, internet of things, mobile internet and the like, the data communication traffic volume is exponentially increased. Due to the influence of the nonlinear effect of single-mode fibers and the requirement for the signal-to-noise ratio of signal transmission in high-speed optical transmission systems, the transmission capacity of single-mode fibers using wavelength division multiplexing technology is rapidly approaching the shannon limit. In order to solve the limitation of the application of the single-mode optical fiber in the fields of communication, sensing and the like, a mode division multiplexing technology with huge transmission capacity potential is developed.
The mode division multiplexing technology is one of the most promising methods for greatly increasing the optical communication capacity, and is considered as the second revolution in the field of optical fiber communication. Mode control is a prerequisite and key to the modulo division multiplexing technique. The connotation of mode control includes key technologies such as mode excitation and mode conversion. The mode conversion is applied to a mode multiplexing front end, a mode demultiplexing rear end and a mode division multiplexing optical network data switching core node of a mode division multiplexing optical fiber communication system, and is the key of mode division multiplexing and mode switching.
For the mode division multiplexing technique, mode conversion is often required. The conversion from the fundamental mode to the high-order mode is used as a mode excitation form, mainly exists in the mode excitation and the mode multiplexing of a sending end, and converts the fundamental mode bearing different information to a few-mode optical fiber or a high-order mode of a multimode optical fiber, thereby solving the problem of a mode division multiplexing optical fiber communication system source; the conversion from the high-order mode to the basic mode is mainly in the mode demultiplexing of the receiving end, and the high-order mode multiplexed together is demodulated into the basic mode, thereby solving the problem of the mode division multiplexing space demodulation.
The current common method for mode conversion in a mode division multiplexing system is a free space optical mode conversion technology based on a phase disc; a phase-matched fiber grating method; a periodic perturbation method by a mechanical external force, and a spatial light modulator method. The method can realize the conversion from the basic mode to the high-order mode, but the complexity of the method is high. In the mode conversion process, the insertion loss and the mode crosstalk of the mode converter are reduced, the mode multiplexing and demultiplexing efficiency is improved, and the simplification of the mode converter becomes a key problem in a mode division multiplexing system.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the disadvantages of the existing mode converters, and to provide a mode converter based on fine core fiber bragg grating, which has reasonable design, low mode crosstalk and small insertion loss, and can be used in a long-distance low-loss transmission mode division multiplexing system.
The technical scheme for solving the technical problems is as follows: a mode converter based on a fine core fiber Bragg grating is characterized in that a first single mode fiber, a first fine core fiber and a second fine core fiber are spliced in sequence, the diameter of the first single mode fiber is larger than that of the first fine core fiber and that of the second fine core fiber, and Bragg gratings are engraved on the fiber core of the second fine core fiber.
As a preferable technical scheme, the first single-mode fiber is an SMF-28 fiber, and the diameter of the fiber core is 9 mu m.
As a preferable technical scheme, the core diameter of the second fine-core optical fiber is 4.2 μm.
As a preferable technical scheme, the core diameter of the first fine-core optical fiber is 2 μm or 4 μm or 8 μm.
As a preferable technical solution, the center wavelength of the fiber bragg grating is 1310 nm.
The invention has the following beneficial effects:
the invention adopts the first single mode fiber, the first thin core fiber and the second thin core fiber which are spliced in sequence, and the fiber core of the second thin core fiber is inscribed with the Bragg grating, thereby realizing LP01And LP11The mode converter has the advantages of simple manufacture, low cost, low mode crosstalk and small insertion loss, and can be used as a mode converter based on the thin-core fiber Bragg grating in a long-distance low-loss transmission mode division multiplexing system.
Drawings
Fig. 1 is a schematic structural view of the present invention.
FIG. 2 is a schematic representation of a mode converter LP based on a fine core fiber Bragg grating01Self-coupled mode, LP01And LP11Mutual coupling mode, LP11Reflection spectrum from coupled mode.
FIG. 3 is a schematic representation of a mode converter LP based on a fine core fiber Bragg grating01Self coupled mode reflectance spectra.
FIG. 4 is a schematic representation of a mode converter LP based on a fine core fiber Bragg grating11Self coupled mode reflectance spectra.
Detailed Description
The present invention will be described in further detail below with reference to the drawings and examples, but the present invention is not limited to the embodiments described below.
Example 1
In fig. 1, the mode converter based on the fine core fiber bragg grating of the present embodiment is formed by connecting a first single mode fiber 1, a first fine core fiber 2, and a second fine core fiber 3.
The first single-mode fiber 1, the first thin-core fiber 2 and the second thin-core fiber 3 are spliced in sequence through an electric arc welding machine, the first single-mode fiber 1 is an SMF-28 fiber, the fiber core diameter of the first single-mode fiber 1 is 9 micrometers, the fiber core diameter of the first thin-core fiber 2 is 4 micrometers, the fiber core diameter of the second thin-core fiber 3 is 4.2 micrometers, a Bragg grating 4 is inscribed on the second thin-core fiber 3 through a femtosecond laser, the central wavelength of the Bragg grating 4 is 1310nm, and the cladding diameters of the first single-mode fiber, the first thin-core fiber and the second thin-core fiber are 125 micrometers.
Example 2
The first single-mode fiber, the first thin-core fiber and the second thin-core fiber are spliced in sequence through an electric arc welding machine, the first single-mode fiber is an SMF-28 fiber, the diameter of a fiber core of the first single-mode fiber 1 is 9 micrometers, the diameter of a fiber core of the first thin-core fiber 2 is 2 micrometers, the diameter of a fiber core of the second thin-core fiber 3 is 4.2 micrometers, a Bragg grating 4 is engraved on the second thin-core fiber 3 through a femtosecond laser, the central wavelength of the Bragg grating 4 is nm, and the cladding diameters of the first single-mode fiber, the first thin-core fiber 1310 and the second thin-core fiber are 125 micrometers.
Example 3
The first single-mode fiber, the first fine-core fiber and the second fine-core fiber are spliced in sequence through an electric arc welding machine, the first single-mode fiber is an SMF-28 fiber, the diameter of a fiber core of the first single-mode fiber 1 is 9 mu m, the diameter of a fiber core of the first fine-core fiber 2 is 8 mu m, the diameter of a fiber core of the second fine-core fiber 3 is 4.2 mu m, the second fine-core fiber 3 is provided with a fiber Bragg grating 4 through a femtosecond laser, the central wavelength of the fiber Bragg grating 4 is 1310nm, and the cladding diameters of the first single-mode fiber, the first fine-core fiber and the second fine-core fiber are 125 mu m.
The working principle of the invention is as follows:
after the incident light enters the first single mode fiber 1, LP is generated in the fiber core of the first single mode fiber 101Fundamental mode, due to mismatch of the first single mode fiber 1 and the first fine core fiber core, part of LP01The fundamental mode is transmitted into the cladding of the first thin-core optical fiber to be excited to generate LP11High order mode, LP can be realized by changing the size of the core diameter of the first fine-core optical fiber01And LP11Energy modulation of both polarization modes to achieve LP01And LP11Conversion of two polarization modes. LP01And LP11The two polarization modes are coupled and self-coupled after being reflected by the Bragg grating in the fiber core of the second thin-core optical fiberAnd finally outputting an interference spectrum by interference.
In order to verify the beneficial effects of the present invention, the inventor respectively performed test experiments on the mode converter based on the thin core fiber bragg grating spliced with the first thin core fiber with the fiber core diameters of 2 μm, 4 μm and 8 μm, and the test conditions were as follows:
first, test instrument
Broadband light source, spectrum analyzer, circulator.
Second, experimental design and result analysis
1. Establishing a test system
And respectively connecting the first single-mode optical fiber in the mode converter based on the fine-core fiber Bragg grating with a circulator through an optical fiber, wherein the circulator is respectively connected with a broadband light source and a spectrum analyzer through the optical fiber, and the test system is established.
2. Test method
A first single mode fiber of the mode converter based on the fine core fiber Bragg grating is connected with a circulator through an optical fiber, and the circulator is respectively connected with a broadband light source and a spectrum analyzer through the optical fiber. Broadband light emitted by the broadband light source is transmitted into the mode converter based on the fine-core fiber Bragg grating through the circulator, transmitted light is reflected through the Bragg grating in the fiber core of the second fine-core fiber in the mode converter structure based on the fine-core fiber Bragg grating, and a reflection spectrum is generated on the spectrum analyzer through the circulator. Based on the test method, the inventor tests the mode conversion performance of the mode converter based on the fine core fiber Bragg grating, wherein the diameters of the first fine core fiber cores of the mode converter based on the fine core fiber Bragg grating are respectively 2 micrometers, 4 micrometers and 8 micrometers. Finally, the diameters of the first fine-core fiber cores are 2 μm, 4 μm and 8 μm respectively, and the LP generated by the mode converter based on the fine-core fiber Bragg grating01Self-coupled mode, LP01And LP11Mutual coupling mode, LP11The energy reflection spectrum of the self-coupled mode can be separately obtained.
3. Results and analysis of the experiments
FIG. 2 shows LP for the first fine-core fiber with core diameters of 2 μm, 4 μm, and 8 μm, respectively01Self-coupled mode, LP01And LP11Mutual coupling mode, LP11An energy reflectance spectrum from coupled mode; FIG. 3 shows LP for the first fine-core fiber with core diameters of 2 μm, 4 μm, and 8 μm, respectively01Self-coupled energy reflectance spectra; FIG. 4 shows LP for the first fine-core fiber with core diameters of 2 μm, 4 μm, and 8 μm, respectively11From the energy reflection spectrum of the self-coupling, it can be seen from a comparison of FIG. 3 with FIG. 4 that LP increases with the core diameter of the first fine-core fiber11The intensity of the mode resulting from self-coupling is reduced, while LP01The intensity of the mode obtained by self-coupling is increased, and the LP can be realized by changing the core diameter of the first thin-core optical fiber through the combination and comparison of reflection spectrums01And LP11Conversion of the two polarization modes.
By combining the above experimental results, it can be found that the mode converter based on the fine core fiber bragg grating of the present invention can realize LP01And LP11The invention is an all-fiber structure, has the advantages of simple manufacture, low cost, low mode crosstalk and small insertion loss, and can be used as a mode converter in a long-distance low-loss transmission mode division multiplexing system.

Claims (2)

1. A mode converter based on a fine core fiber bragg grating, characterized by: the fiber core of the first thin core fiber (3) is inscribed with a Bragg grating (4);
the first single-mode fiber (1) is an SMF-28 fiber, and the diameter of a fiber core is 9 mu m.
2. The fine core fiber bragg grating based mode converter of claim 1, wherein: the core diameter of the first fine-core optical fiber (2) is 2 mu m or 4 mu m or 8 mu m.
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Citations (2)

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CN103852428A (en) * 2014-03-12 2014-06-11 西安石油大学 Humidity sensor based on multimode fiber core and fiber grating and preparation method of humidity sensor
US9810840B2 (en) * 2016-01-06 2017-11-07 Elenion Technologies Llc Integrated on-chip polarizer
CN205427234U (en) * 2016-01-11 2016-08-03 中国工程物理研究院激光聚变研究中心 Mould field adapter and fiber laser
CN105841840B (en) * 2016-03-30 2018-10-26 东北大学 It is a kind of to measure density of hydrogen and the fibre optical sensor of temperature simultaneously
CN205940607U (en) * 2016-04-26 2017-02-08 哈尔滨理工大学 Temperature and refracting index sensor based on multimode fiber intermode interference and FBG
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5048913A (en) * 1989-12-26 1991-09-17 United Technologies Corporation Optical waveguide embedded transverse spatial mode discrimination filter
CN104950393A (en) * 2015-07-02 2015-09-30 龙岩学院 Mode converter based on asymmetrical Bragg grating

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