CN104076433A - Optical fiber mode separator - Google Patents
Optical fiber mode separator Download PDFInfo
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- CN104076433A CN104076433A CN201310692492.0A CN201310692492A CN104076433A CN 104076433 A CN104076433 A CN 104076433A CN 201310692492 A CN201310692492 A CN 201310692492A CN 104076433 A CN104076433 A CN 104076433A
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Abstract
The invention discloses an optical fiber mode separator. An optical fiber is composed of host materials and three fiber cores, wherein center lines of the fiber cores form a straight line, the center distances between the middle fiber core and the side fiber cores are the same, and refractive index distribution and fiber core dimensions of the fiber cores are the same. The optical fiber structure with the three fiber cores is adopted, therefore, coupling length difference among different modes is increased, the modes can be separated effectively, and clutter among different modes can be inhibited effectively. The optical fiber mode separator is used in a serial connection mode, and capable of effectively separating a plurality of different modes. Optical fiber parameters are identical completely, and therefore, difficult manufacturing and effect of parameter errors on coupling performance of optical fibers are avoided when the fiber cores different in dimensions are adopted.
Description
Technical field
The present invention relates to fiber optic communication field, be specifically divided into and there is the mode splitter separating between implementation pattern.
Background technology
In recent years, space division multiplexing has caused people's interest widely.SDM system adopts multi-core fiber or multimode optical fiber to realize.While wherein adopting multimode optical fiber, be to realize mould by different mode (comprising different polarization modes) to divide multiplexing.Due to multiple different different information of pattern load, therefore, mould divides the multiplexing transmission capacity that can effectively improve optical fiber.
In mould division multiplexing system, both needed different mode to be synthesized to an optical fiber, also need to different patterns effectively be separated at receiving end.Need pattern bundling device at transmitting terminal, and need mode splitter at receiving end.Adopt discrete component, as grating can implementation pattern separation, but increased the complicacy of system.The simple case of the mode splitter based on optical fiber structure is the Twin-Core Fiber Coupler that adopts symmetrical structure, utilizes the difference of different mode coupling length, by selecting the object that suitable parameter just can implementation pattern separation.Owing to will making the coupling length of different mode meet specific multiple relation, the bandwidth of the separation vessel that this method obtains is narrower.Use with the same pattern bundling device that also can be used as of twin-core fiber of less fundamental mode optical fibre coupling based on single-mode fiber; its shortcoming is that the basic mode of single-mode fiber and the high-order mode of less fundamental mode optical fibre are coupled based on index matching; owing to being difficult to realize Broadband Matching; its bandwidth of operation is generally all narrower; and [Few-mode optical fiber for mode-division multiplexing (less fundamental mode optical fibre divides multiplexing for mould) can be coupled between different mode
opt. Fiber Technol., 2011,
17(5): 490-494].
Summary of the invention
For prior art deficiency, the object of this invention is to provide and a kind ofly there is wideband operation characteristic and effectively avoid the novel mode splitter being coupled between pattern.
Technical scheme of the present invention is: a kind of fiber mode separation vessel, comprise three fibre cores and covering, and described covering is made up of host material; In line, middle fibre core is identical with the centre distance of both sides fibre core for the line of centres of described three fibre cores, and the diameter of identical, described three fibre cores of index distribution of described three fibre cores is identical, the normalized frequency of described three fibre cores
vmeet
v>2.405,
, wherein
afor fiber core radius, λ is operation wavelength,
n corefor fiber core refractive index,
n cladfor cladding index.
As a further improvement on the present invention, the refractive index of described three fibre cores
arefractive index with covering
n claddifference meet:
n core-
n clad>0.008.
As a further improvement on the present invention, the centre distance of described middle fibre core and both sides fibre core
dmeet:
d>2
a+ 3 μ m.
As a further improvement on the present invention, the refractive index of described three fibre cores
arefractive index with covering
n claddifference meet:
n core-
n clad>0.01, the normalized frequency of described fibre core
vmeet
v>3.832.
Technique effect of the present invention is: adopt the optical fiber structure of three fibre cores, increase the coupling length difference between different mode, effective separation of implementation pattern, and effective mixed the disturbing between suppression mode.After series connection, use, can realize the effective separation to multiple different modes.Fiber core parameter is identical, while having avoided employing different size fibre core, and the impact on coupling fiber performance of the difficulty of making and parameter error.
Brief description of the drawings
Fig. 1 is the cross sectional representation of a kind of embodiment of the present invention;
Fig. 2 is the connecting curve of different mode in twin-core fiber;
Fig. 3 is the connecting curve of different mode in the optical fiber shown in Fig. 1;
Fig. 4 inputs LP from the first fibre core 2 in the optical fiber shown in Fig. 1
02after mould, in the field strength distribution of different transmission range place optical fiber;
Fig. 5 is that structure shown in Fig. 1 is for separating of LP
02when mould, the output energy of the 3rd fibre core 4 is with wavelength variations curve;
When Fig. 6 is normalized frequency V=4.8, core centre spacing d=18 μ m, a) for fibre core and cladding index poor be the connecting curve of 0.01 different mode; B) for fibre core and cladding index poor be the connecting curve of 0.012 different mode.
Wherein, 1 host material, 2. the first fibre core, 3. the second fibre core, 4. the 3rd fibre core.
Embodiment
Figure 1 shows that the xsect signal of optical fiber of the present invention, comprise host material 1, the first fibre core 2, the second fibre core 3 and the 3rd fibre core 4, in line, the second fibre core 3 is identical with the centre distance of the first fibre core 2 and the 3rd fibre core 4 respectively for the first fibre core 2, the second fibre core 3 and the 3rd fibre core 4 lines of centres.Index distribution, the core size of the first fibre core 2, the second fibre core 3 and the 3rd fibre core 4 are identical.The normalized frequency of three fibre cores
vmeet
v>2.405.Here,
, wherein
afor fiber core radius, λ is operation wavelength,
n corefor fiber core refractive index,
n cladfor cladding index.
If input light only comprises two kinds of patterns, i.e. basic mode and a high-order mode, inputs light beam from the first fibre core 2, and high-order mode, after coupling, is exported from the 3rd fibre core 4, and basic mode is retained in the first fibre core 2, thus the object that implementation pattern separates.If comprise multiple patterns in input light, light is from the first fibre core 2 input, and the pattern (pattern that coupling length is the shortest) of high-order will be exported from the 3rd fibre core 4, and other pattern is stayed the first fibre core 2.If desired all patterns are separated, can, by the light of exporting from the first fibre core 2 again through mode splitter, isolate next high-order mode.Finally all patterns all can be separated through separating for several times.
In theory, the function that adopts symmetrical twin-core fiber also can implementation pattern to separate.There is different coupling lengths based on different mode, select suitable optical fiber parameter, can make different patterns from different fibre core output, thereby realize the object of beam splitting.Fig. 2 is the connecting curve of the different mode of twin-core fiber, and while input from a side fibre core by light, the pattern energy in opposite side fibre core is with the change curve of transmission range.As seen from the figure, optical fiber basic mode coupling length is the longest, and mode order is higher, and its coupling length is shorter, as LP
02the coupling length of mould is longer than LP
11mould.The pattern that order is high is more easily coupled, and therefore the shorter reason of coupling length is: its mould field distribution of pattern that order is higher is more expanded to covering, by theory of fiber, overlapping region between pattern is larger, its coupling coefficient is larger, and therefore, its coupling length is also just shorter.
If LP
02the coupling length of mould is significantly shorter than LP
11mould, obviously LP
11the coupling length of mould is shorter than LP
01mould.Therefore, getting fiber lengths is LP
02the coupling length of mould,, if containing LP
01mould, LP
11mould, LP
02the light beam of mould is inputted from a fibre core, LP
02mould will be exported from another fibre core, and LP
01mould, LP
11mould is because coupling length is long, energy still in the fibre core of input, thereby, just can realize LP
02the separation of mould.If the coupling length difference between pattern is large not, easily there is the mixing between pattern, make the increase of crosstalking of output mode, thereby affect extraction and the reduction of information.For example, LP shown in Fig. 2
01mould, LP
11mould, LP
02mould, LP
21coupling length ratio between mould is: 12.25:2.04:1.14:1.The difference of rear three kinds of wavelength is less.
Obviously, described fibre core is non-single-mode fiber, except transmission basic mode is LP
01beyond mould, at least can transmit LP
11mould, should have according to mode characteristic: normalized frequency
v>2.405.Separate LP if realize
02mould, its normalized frequency
v>3.832.Be illustrated in figure 3 the connecting curve of different mode in optical fiber shown in the present.While input from the first fibre core 2 by light, the pattern energy in the 3rd fibre core 4 is with the change curve of transmission range.As seen from the figure, after twin-core structure becomes three-core structure, it is large that the coupling length difference between different mode obviously becomes.LP shown in Fig. 2
01mould, LP
11mould, LP
21coupling length ratio between mould, LP02 mould is: 26:3.44:1.476:1.Can understand so this variation.Three-core structure can be thought add a fibre core at the center of twin-core structure again and obtain.And it is shorter for coupling length, it is the larger pattern in overlapping region between pattern, increase after a fibre core, the overlapping meeting of pattern between two adjacent fibre cores is larger, thereby more easily produce strong coupling, therefore, can be very fast first through the second fibre core 3 from the light of a side fibre core input, then be coupled long opposite side fibre core.And the pattern of growing for coupling length in twin-core structure has increased after a fibre core, its coupling length reduces DeGrain.Adopt three-core structure can effectively increase the difference of the coupling length between different mode, thereby it is more easy that pattern is separated.As seen from Figure 3, the LP of the first fibre core 2
02mould transmits through a segment distance, will be coupled with the second fibre core 3, then after being coupled with the 3rd fibre core 4, be transferred to the 3rd fibre core 4.If through this segment distance transmission, other pattern is all difficult to be coupled to the 3rd fibre core 4, getting fiber lengths is LP
02mould is coupled to the coupling length of the 3rd fibre core 4 from the first fibre core 2, in the time that input light is inputted from the first fibre core 2, and just can be by LP
02mould is separated.
Fig. 5 provides structure shown in Fig. 1 for separating of LP
02when mould, the output energy of the 3rd fibre core 4 is with wavelength variations curve.As seen from the figure, LP
02mould can all can be exported within the scope of wider bandwidth in low-loss, and LP
01mould, LP
11the energy of mould is all very low.Be LP
02mould can effectively be separated, and other pattern crosstalk very little.
Fig. 6 provides normalized frequency V, d is identical for core centre spacing, and fibre core is from the poor different situation of cladding index, and light is during from a side fibre core input, the energy trace of opposite side fibre core.As seen from the figure, when fibre core and cladding index poor when larger, the energy conversion of high-order mode is higher, the coupling length difference between different mode is larger simultaneously.This be because, in the situation that normalized frequency V is identical, fibre core and cladding index are poor larger, the effective refractive index difference between pattern is also larger, is also that the energy distribution difference of different mode in covering is also larger.This just causes the further increase of the difference of coupling length between different mode.Therefore, adopt larger fibre core and the poor performance of mode splitter that can make of cladding index more excellent.
Obviously, optical fiber of the present invention can be used as pattern bundling device equally.Be about to need synthetic light respectively from the input of both sides fibre core, the short pattern of coupling length, after coupling, arrives opposite side fibre core, converges rear output with another light beam.When pattern is closed bundle, should first synthesize the pattern that coupling length is grown, the more synthetic shorter pattern of coupling length.The final Shu Guang that closes that obtains multiple patterns.
Embodiment mono-:
Below in conjunction with brief description of the drawings the preferred embodiments of the present invention.As shown in Figure 1, the present embodiment is realized LP
02mould and LP
01mould, LP
11separation between mould.Matrix material of optic fibre 1 is pure quartz, and the radius of three fibre cores is 6.15 μ m, and the refringence of fibre core and covering is 0.012.The centre distance of adjacent fibre core is 22 μ m.Light is inputted from the first fibre core 2, LP
02mould is exported from the 3rd fibre core 4, and other pattern is exported from the first fibre core 2.Its coupling length curve as shown in Figure 3.Visible, LP
02mode coupling length is far smaller than the coupling length of another two patterns.Getting fiber lengths is 33.5 mm.The energy of the different mode that the 3rd fibre core 4 is exported as shown in Figure 4.Visible, within the scope of 1.48-1.515 mum wavelength, LP
02the output power of mould is all greater than-1 dB, and the energy of another two patterns is all less than-30 dB, and therefore, the 3rd fibre core 4 is exportable has the low LP crosstalking
02mould.
Above-mentioned accompanying drawing is only explanatory view, protection scope of the present invention is not formed to restriction.
Claims (4)
1. a fiber mode separation vessel, comprises three fibre cores and covering, and described covering is made up of host material; It is characterized in that: in line, middle fibre core is identical with the centre distance of both sides fibre core for the line of centres of described three fibre cores, the diameter of identical, described three fibre cores of index distribution of described three fibre cores is identical, the normalized frequency of described three fibre cores
vmeet
v>2.405,
, wherein
afor fiber core radius, λ is operation wavelength,
n corefor fiber core refractive index,
n cladfor cladding index.
2. a kind of fiber mode separation vessel according to claim 1, is characterized in that the refractive index of described three fibre cores
arefractive index with covering
n claddifference meet:
n core-
n clad>0.008.
3. a kind of fiber mode separation vessel according to claim 1, is characterized in that, the centre distance of middle fibre core and both sides fibre core
dmeet:
d>2
a+ 3 μ m.
4. a kind of fiber mode separation vessel according to claim 1, is characterized in that the refractive index of described three fibre cores
arefractive index with covering
n claddifference meet:
n core-
n clad>0.01, the normalized frequency of described fibre core
vmeet
v>3.832.
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| CN104076433B CN104076433B (en) | 2017-05-31 |
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Cited By (6)
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| CN106019475A (en) * | 2016-07-28 | 2016-10-12 | 江苏大学 | Few-mode fiber device |
| CN106304419A (en) * | 2016-08-15 | 2017-01-04 | 上海交通大学 | The wireless forward pass system of digital optical transmission based on multi-core fiber |
| CN106461857A (en) * | 2015-03-13 | 2017-02-22 | 株式会社藤仓 | Optical fiber and method for manufacturing optical fiber |
| CN108964765A (en) * | 2017-05-19 | 2018-12-07 | 吕婧菲 | A kind of multimode fibre transmitting device |
| CN112162355A (en) * | 2020-09-18 | 2021-01-01 | 北京交通大学 | Optical fiber mode selection coupler based on symmetrical double-core few-mode optical fiber |
| WO2021214976A1 (en) * | 2020-04-24 | 2021-10-28 | 日本電信電話株式会社 | Intermode loss difference compensator |
Family Cites Families (4)
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| US6538807B2 (en) * | 2000-09-07 | 2003-03-25 | Sumitomo Electric Industries, Ltd. | Amplification optical fiber, fiber optic amplifier, optical transmitter, and optical communication system |
| US7412142B2 (en) * | 2006-05-19 | 2008-08-12 | Corning Incorporated | Optical fiber with plurality of air holes and stress rods |
| CN101339269B (en) * | 2008-08-12 | 2010-06-02 | 江苏大学 | Optical fibre wavelength-division multiplex device |
| WO2012046696A1 (en) * | 2010-10-05 | 2012-04-12 | 株式会社フジクラ | Polarization-maintaining optical fiber |
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| CN106461857A (en) * | 2015-03-13 | 2017-02-22 | 株式会社藤仓 | Optical fiber and method for manufacturing optical fiber |
| CN106461857B (en) * | 2015-03-13 | 2019-10-01 | 株式会社藤仓 | The manufacturing method of optical fiber and optical fiber |
| CN106019475A (en) * | 2016-07-28 | 2016-10-12 | 江苏大学 | Few-mode fiber device |
| WO2018018666A1 (en) * | 2016-07-28 | 2018-02-01 | 江苏大学 | Few-mode fibre device |
| CN106019475B (en) * | 2016-07-28 | 2019-04-02 | 江苏大学 | A kind of less fundamental mode optical fibre device |
| CN106304419A (en) * | 2016-08-15 | 2017-01-04 | 上海交通大学 | The wireless forward pass system of digital optical transmission based on multi-core fiber |
| CN106304419B (en) * | 2016-08-15 | 2020-06-12 | 上海交通大学 | Wireless forward transmission system for digital optical transmission based on multi-core optical fiber |
| CN108964765A (en) * | 2017-05-19 | 2018-12-07 | 吕婧菲 | A kind of multimode fibre transmitting device |
| CN108964765B (en) * | 2017-05-19 | 2021-05-28 | 吕婧菲 | Multimode optical fiber transmission device |
| WO2021214976A1 (en) * | 2020-04-24 | 2021-10-28 | 日本電信電話株式会社 | Intermode loss difference compensator |
| JP7359296B2 (en) | 2020-04-24 | 2023-10-11 | 日本電信電話株式会社 | Intermode loss difference compensator |
| CN112162355A (en) * | 2020-09-18 | 2021-01-01 | 北京交通大学 | Optical fiber mode selection coupler based on symmetrical double-core few-mode optical fiber |
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| CN104076433B (en) | 2017-05-31 |
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