CN111796359A - Double-core optical fiber mode converter - Google Patents

Double-core optical fiber mode converter Download PDF

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Publication number
CN111796359A
CN111796359A CN202010761401.4A CN202010761401A CN111796359A CN 111796359 A CN111796359 A CN 111796359A CN 202010761401 A CN202010761401 A CN 202010761401A CN 111796359 A CN111796359 A CN 111796359A
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China
Prior art keywords
fiber
core
mode
optical fiber
period
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CN202010761401.4A
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Chinese (zh)
Inventor
毕卫红
田朋飞
金娃
付广伟
付兴虎
刘强
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Yanshan University
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Yanshan 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02042—Multicore optical fibres
    • 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Optical Integrated Circuits (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

The invention discloses a double-core optical fiber mode converter, which converts a fiber core fundamental mode LP01To the higher order mode LP21Or LP02The conversion comprises a non-coaxial double-core optical fiber, wherein the radiuses and refractive indexes of two fiber cores of the non-coaxial double-core optical fiber are different, and a section of long-period grating with the grating period of lambada is engraved on one of the fiber cores, so that the conversion from a fundamental mode to a high-order mode can be realized.

Description

Double-core optical fiber mode converter
Technical Field
The invention relates to a double-core optical fiber mode converter, belonging to the technical field of optical fibers.
Background
At present, the mode division multiplexing system receives wide attention because it can overcome the limit of single mode fiber transmission capacity, realize fiber transmission with larger capacity, and meet the increasing communication demand of people. Based onThe mode division multiplexing system of the few-mode optical fiber mainly uses different optical fiber modes in the few-mode optical fiber as transmission channels to simultaneously transmit multiple signals so as to increase the transmission capacity. The mode converter converts a fiber core fundamental mode (LP01) transmitted in a single-mode optical fiber into a fiber core high-order mode transmitted in a few-mode optical fiber, is a key device in a mode division multiplexing system, and is realized mainly by a spatial light modulator method, a phase plate method, a photon lantern method, a long-period grating method and the like. For example, in 2015, the Kanshikuan of Beijing post and telecommunication university realizes LP by using methods such as spatial frequency spectrum matching01To LP22And (4) switching modes. Phase plate method, as 2011, Ryf.R. subject group achieved LP using 4 sets of phase plates, respectively01Axial LP11a、LP11b、LP21a、LP21b(ii) a For example, Long period fiber grating method, Bang B et al, 2014, of Tianjin Ministry of Japan, also proposed the adoption of CO in two-mode fiber2The laser inscribes the long-period fiber grating to realize the conversion of the LP01 mode to the LP11 mode.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a dual-core optical fiber mode converter with high conversion efficiency and high mode purity.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a dual-core optical fiber mode converter for converting the fiber core fundamental mode LP01To the higher order mode LP21Or LP02And conversion, including a non-coaxial dual-core fiber, wherein the two fiber cores of the non-coaxial dual-core fiber have different radiuses and refractive indexes, and one fiber core is engraved with a long-period grating with the grating period of Λ, and the phase matching conditions are as follows:
λ＝(nmn-n01)Λ，
wherein: lambda is the wavelength and takes 1550 nm;
Λ is the grating period;
nmna high order mode effective index;
n01is the fundamental mode effective index.
The technical scheme of the invention is further improved as follows: what is needed isOne core radius of the non-coaxial double-core optical fiber is 4 mu m, the refractive index is 1.454, the other core radius is 12 mu m, the refractive index is 1.455, a grating with the period of 1593 is written, the central distance of the two cores is 22 mu m, and the core fundamental mode LP is realized01To the higher order mode LP21The conversion of (1).
The technical scheme of the invention is further improved as follows: one fiber core of the non-coaxial double-core optical fiber has the radius of 4 mu m, the refractive index is 1.454, the other fiber core has the radius of 12 mu m, the refractive index is 1.455, gratings with the period of 1373 are engraved, the distance between the centers of the two fiber cores is 17 mu m, and the fiber core fundamental mode LP is realized01To the higher order mode LP02The conversion of (1).
The technical scheme of the invention is further improved as follows: the preparation method comprises the following steps:
s1, placing the non-coaxial double-core optical fiber on a three-dimensional displacement rotating platform, and after two ends of the non-coaxial double-core optical fiber are respectively connected with a single-mode tail fiber, connecting one end of the non-coaxial double-core optical fiber with a broadband light source and connecting one end of the non-coaxial double-core optical fiber with a spectrum analyzer;
s2, by controlling CO2The energy of the laser, the periodic template and the scanning speed introduce periodic change on the surface of the fiber core, and a section of long-period grating is inscribed.
Due to the adoption of the technical scheme, the invention has the technical progress that:
the invention can make the fiber core fundamental mode LP01To the higher order mode LP21Or LP02The conversion structure is simple, the conversion efficiency is high, the purity of the obtained high-order mode is high, the bandwidth is wide, the insertion loss is small, the high-order mode and the fundamental mode are transmitted in different fiber cores, the application is convenient, and the method has great application potential in a mode division multiplexing system.
Drawings
FIG. 1 is a schematic view of a non-coaxial dual core optical fiber of the present invention;
FIG. 2 is a schematic diagram of a dual-core fiber grating according to the present invention;
FIG. 3 is an LP of the present invention01And LP21A dispersion map;
FIG. 4 is an LP of the present invention01-LP21A mode conversion simulation process diagram;
FIG. 5 is the present inventionInvention LP01-LP21A graph of mode conversion efficiency;
FIG. 6 shows an LP according to the present invention01-LP21A mode conversion bandwidth map;
FIG. 7 shows an LP according to the present invention01And LP02A dispersion map;
FIG. 8 is an LP of the present invention01-LP02A mode conversion simulation process diagram;
FIG. 9 shows an LP of the present invention01-LP02A graph of mode conversion efficiency;
FIG. 10 shows an LP of the present invention01-LP02A mode conversion bandwidth map;
FIG. 11 is a schematic diagram of a modular multiplexing system of the present invention;
FIG. 12 is a schematic view of the structure of a production apparatus of the present invention;
fig. 13 is a schematic structural diagram of an application device of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples:
as shown in FIG. 1, a dual core fiber mode converter couples the core fundamental mode LP01To the higher order mode LP21Or LP02And converting, including a non-coaxial dual-core fiber, wherein the two cores of the non-coaxial dual-core fiber have different radiuses and refractive indexes, and a long-period grating with a grating period of Λ is written on one of the cores, the grating diagram is shown in fig. 2, and the phase matching conditions are as follows:
λ＝(nmn-n01)Λ，
wherein: lambda is the wavelength and takes 1550 nm;
Λ is the grating period;
nmna high order mode effective index;
n01is the fundamental mode effective index.
The core fundamental mode LP can be realized when the double-core optical fiber has the following parameters01To the higher order mode LP21One core with a radius of 4 μm and a refractive index of 1.454, can only transmit LP01A mode; the other core radius is 12 mum, refractive index 1.455, and writing a grating with period 1593, four (LP) can be transmitted01、LP11、LP21、LP02) Mode, two core centers are 22 μm apart. The influence of each parameter on the performance of the converter is analyzed in a simulation mode, and the test result is shown in FIGS. 3-6. According to the simulation result, a fiber core fundamental mode LP01To the higher order mode LP21The highest conversion efficiency can reach 99%, and the bandwidth with the conversion efficiency more than 90% is 14 nm.
The core fundamental mode LP can be realized when the double-core optical fiber has the following parameters01To the higher order mode LP02One core with a radius of 4 μm and a refractive index of 1.454, can only transmit LP01A mode; the other core, with a radius of 12 μm, a refractive index of 1.455, and written with a grating with a period 1373, is able to transmit four (LP01, LP11, LP21, LP02) modes, with a distance of 17 μm between the two core centers. The influence of each parameter on the performance of the converter is analyzed in a simulation mode, and the test result is shown in FIGS. 7-10. According to the simulation result, a fiber core fundamental mode LP01To the higher order mode LP02The highest conversion efficiency can reach 96%, and the 3dB bandwidth is 21 nm.
As shown in fig. 12, the preparation method is as follows:
s1, placing the non-coaxial double-core optical fiber on a three-dimensional displacement rotating platform, and after two ends of the non-coaxial double-core optical fiber are respectively connected with a single-mode tail fiber, connecting one end of the non-coaxial double-core optical fiber with a broadband light source and connecting one end of the non-coaxial double-core optical fiber with a spectrum analyzer;
s2, by controlling CO2The energy of the laser, the periodic template and the scanning speed introduce periodic change on the surface of the fiber core, and a section of long-period grating is inscribed.
As shown in FIG. 13, after the etching is finished, one end of the dual-core fiber converter is connected with the tunable light source, and the other end can observe the conversion effect at the PC end through the CCD (LP can be observed)21、LP02Mode field).
As shown in fig. 11, the mode converter is an important component in the analog-to-digital multiplexing system. When the dual-core optical fiber mode converter is applied, one end of the dual-core optical fiber mode converter is connected with an information light source, and the other end of the dual-core optical fiber mode converter is connected with a mode multiplexer.

Claims (4)

1. A dual-core fiber mode converter, comprising: LP of the fundamental mode of the fiber core01To the higher order mode LP21Or LP02And conversion, including a non-coaxial dual-core fiber, wherein the two fiber cores of the non-coaxial dual-core fiber have different radiuses and refractive indexes, and one fiber core is engraved with a long-period grating with the grating period of Λ, and the phase matching conditions are as follows:
λ＝(nmn-n01)Λ，
wherein: lambda is the wavelength and takes 1550 nm;
Λ is the grating period;
nmna high order mode effective index;
n01is the fundamental mode effective index.
2. A dual core fiber mode converter according to claim 1, wherein: one fiber core of the non-coaxial double-core optical fiber has the radius of 4 mu m, the refractive index is 1.454, the other fiber core has the radius of 12 mu m, the refractive index is 1.455, a grating with the period of 1593 is written, the central distance of the two fiber cores is 22 mu m, and the fiber core fundamental mode LP is realized01To the higher order mode LP21The conversion of (1).
3. A dual core fiber mode converter according to claim 1, wherein: one fiber core of the non-coaxial double-core optical fiber has the radius of 4 mu m, the refractive index is 1.454, the other fiber core has the radius of 12 mu m, the refractive index is 1.455, gratings with the period of 1373 are engraved, the distance between the centers of the two fiber cores is 17 mu m, and the fiber core fundamental mode LP is realized01To the higher order mode LP02The conversion of (1).
4. A dual core fiber mode converter according to claim 1, wherein: the preparation method comprises the following steps:
s1, placing the non-coaxial double-core optical fiber on a three-dimensional displacement rotating platform, and after two ends of the non-coaxial double-core optical fiber are respectively connected with a single-mode tail fiber, connecting one end of the non-coaxial double-core optical fiber with a broadband light source and connecting one end of the non-coaxial double-core optical fiber with a spectrum analyzer;
s2, by controlling CO2The energy of the laser, the periodic template and the scanning speed introduce periodic change on the surface of the fiber core, and a section of long-period grating is inscribed.
CN202010761401.4A 2020-07-31 2020-07-31 Double-core optical fiber mode converter Pending CN111796359A (en)

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Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4748687A (en) * 1984-09-25 1988-05-31 Siemens Aktiengesellschaft Narrow band laser transmitter
US20040042726A1 (en) * 2002-06-07 2004-03-04 Cidra Corporation Tunable optical filter having large diameter optical waveguide with bragg grating and being configured for reducing the bulk modulus of compressibility thereof
US20040258357A1 (en) * 2003-06-20 2004-12-23 Alcatel Optical filter
CN102625919A (en) * 2009-09-14 2012-08-01 Ipg光子公司 Multimode fiber
CN203838366U (en) * 2013-12-16 2014-09-17 国家电网公司 Broadband optical fiber mode converter
CN104345380A (en) * 2014-08-07 2015-02-11 江苏大学 Two-mode optical fiber
CN105022117A (en) * 2015-07-23 2015-11-04 江苏大学 Double-core fiber based long-period FBG mode-field converter
US20170003219A1 (en) * 2013-03-15 2017-01-05 Ofs Fitel, Llc Optical sensor having fiduciary marks detected by backscattered light
CN107272115A (en) * 2017-08-14 2017-10-20 江苏法尔胜光电科技有限公司 A kind of pattern multiplexer/demultiplexer based on three core fibres
CN109613646A (en) * 2019-01-18 2019-04-12 厦门大学 A kind of different core twin-core fiber of transmission spectrum existing characteristics wavelength
CN209746179U (en) * 2019-01-07 2019-12-06 云南大学 novel high-efficiency multi-mode converter

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4748687A (en) * 1984-09-25 1988-05-31 Siemens Aktiengesellschaft Narrow band laser transmitter
US20040042726A1 (en) * 2002-06-07 2004-03-04 Cidra Corporation Tunable optical filter having large diameter optical waveguide with bragg grating and being configured for reducing the bulk modulus of compressibility thereof
US20040258357A1 (en) * 2003-06-20 2004-12-23 Alcatel Optical filter
FR2856482B1 (en) * 2003-06-20 2005-11-11 Cit Alcatel OPTICAL FILTER
CN102625919A (en) * 2009-09-14 2012-08-01 Ipg光子公司 Multimode fiber
US20170003219A1 (en) * 2013-03-15 2017-01-05 Ofs Fitel, Llc Optical sensor having fiduciary marks detected by backscattered light
CN203838366U (en) * 2013-12-16 2014-09-17 国家电网公司 Broadband optical fiber mode converter
CN104345380A (en) * 2014-08-07 2015-02-11 江苏大学 Two-mode optical fiber
CN105022117A (en) * 2015-07-23 2015-11-04 江苏大学 Double-core fiber based long-period FBG mode-field converter
CN107272115A (en) * 2017-08-14 2017-10-20 江苏法尔胜光电科技有限公司 A kind of pattern multiplexer/demultiplexer based on three core fibres
CN209746179U (en) * 2019-01-07 2019-12-06 云南大学 novel high-efficiency multi-mode converter
CN109613646A (en) * 2019-01-18 2019-04-12 厦门大学 A kind of different core twin-core fiber of transmission spectrum existing characteristics wavelength

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