CN107329204A - A kind of single mode transport method based on mode cutoff in photon band gap - Google Patents
A kind of single mode transport method based on mode cutoff in photon band gap Download PDFInfo
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- CN107329204A CN107329204A CN201710719524.XA CN201710719524A CN107329204A CN 107329204 A CN107329204 A CN 107329204A CN 201710719524 A CN201710719524 A CN 201710719524A CN 107329204 A CN107329204 A CN 107329204A
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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
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
- G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
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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
- G02B6/032—Optical fibres with cladding with or without a coating with non solid core or cladding
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- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
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Abstract
The invention discloses a kind of single mode transport method based on mode cutoff in photon band gap, belong to optical fiber transmission sensing technical field.Described transmission method, according to the relation curve of the effective refractive index of each pattern and wavelength in optical fiber, determines the cut-off wave band of single mode；By structure parameter optimizing, increase the bandwidth of single mode transport wave band, realize the single mode transport under different operating wavelength.The single mode transport service band and the selection of bandwidth that the method provided by the present invention is determined are more flexible, can improve single mode transport applicability by structure optimization, it is adaptable to short distance, the application scenario higher to pattern requirement.
Description
Technical field
The present invention relates to a kind of method that single mode transport is realized in hollow core photonic bandgap fiber, belong to optical fiber transmission sensing
Technical field.
Background technology
Hollow core photonic bandgap fiber is a kind of novel optical fiber based on photonic band gap effects, by silica and air
Hole periodic arrangement constitutes the 2 D photon crystal material that limitation is produced to light wave, and defect is then introduced in aperiodic materials,
Light wave is set to be propagated in defect, this is a kind of low-index material (air) that is based at high index of refraction background material (silica)
In two-dimensional and periodic arrangement formed by microstructured optical fibers.This principle causes photon band-gap optical fiber with the uniqueness in structure
It is such as low to the susceptibility of temperature, electromagnetic field, space radiation environmental factor with numerous characteristics different from traditional fiber, it is right
Bend-insensitive etc..Therefore, hollow core photonic bandgap fiber has larger potential advantages in the fields such as optical fibre gyro, is considered as
It is the preferred optical fiber of optical fibre gyro of future generation.
The pattern of optical fiber represents the optical field distribution that can be stabilized in a fiber.The propagation of light field in a fiber meets
Helmholtz equation, with reference to its field boundary condition, can solve the discrete particular solution of equation, each particular solution is just allowed to
A kind of pattern propagated in a fiber.It is different from common phase step type optical fiber, due to the complexity of optical fiber structure, hollow core photonic bandgap
Optical fiber realizes single mode transport in the absence of a simple single mode condition, the shadow of the mode characteristic of optical fiber by many structural parameters
Ring, therefore generally there are a variety of higher order modes.Realize that single mode transport generally requires extremely complex design, for drawing process
It is required that it is very high, and inevitably there is certain error in fiber draw process between preferable single mode design,
Capillary defect and covering that the glass-air interface of optical fiber inwall is present and fibre core air column physical dimension it is uneven, all
Light beam can be caused to inspire higher order mode in communication process.
Application of the presence of higher order mode to hollow core photonic bandgap fiber generates the limitation of highly significant, Fibre Optical Sensor,
The fields such as optical-fibre communications, optical fiber laser are required for obtaining preferable beam quality, make flashlight stable in single basic mode
Transmission.In addition for optical fibre gyro, phase is different between the high-order mode of two ways of optical signals and basic mode in fiber optic loop, between pattern
The subwave that interference is produced may bring measurement error to high-precision optical fiber gyro.Therefore in order to optimize hollow core photonic bandgap fiber
Transmitting beam quality and improve optical fiber applicability, it is desirable to provide a kind of practicable for drawing process, hollow light
Subband pbg fiber single mode transport method.
The content of the invention
The invention aims to solve in existing hollow core photonic bandgap fiber, there is more higher order mode, it is impossible to full
Enough the problem of the application scenario higher to fiber mode characteristic requirements, propose a kind of based on mode cutoff in photon band gap
Single mode transport method.Described single mode transport method is realized especially by following steps：
The first step, according to the relation curve of the effective refractive index of each pattern and wavelength in optical fiber, by core mode be divided into
Few two groups, one of which is basic mode, and remaining is high-order mode；
Second step, is emulated to basic mode, determines the cut-off wave of the wave band that high-order mode is all ended by band gap, i.e. single mode
Section.
3rd step, structure parameter optimizing increases the bandwidth of single mode transport wave band, realizes that the single mode under different operating wavelength is passed
It is defeated.The mode characteristic curve of basic mode is reduced to a horizontal linear, then the bandwidth of λ of single mode transport wave bandSIt is expressed as：
λS=Δ neff/|k|
Wherein, k is the slope of band gap left side edge, Δ neffIt is effective between cut-off wave strong point and basic mode for second order mode
Mode refractive index is poor.
By in the range of 1.2~2 increase clad material refractive index, adjustment dutycycle d/ Λ 0.962 to 0.979 it
Between, increase the bandwidth of single mode transport wave band.Single mode transport service band is moved by changing covering chamfering.
The advantage of the invention is that：
(1) propose the method that single mode transport is realized in hollow core photonic bandgap fiber, it is adaptable to short distance, to pattern will
Ask higher application scenario；
(2) selection of service band and bandwidth is more flexible；
(3) single mode transport applicability can be improved by structure optimization.
Brief description of the drawings
Fig. 1 is 7 core photon band-gap optical fiber simulation model schematic diagrames；
Fig. 2 is 7 core photon band-gap optical fiber structural parameters schematic diagrames；
Fig. 3 is the graph of a relation of 7 core photon band-gap optical fiber pattern effective refractive indexs and wavelength；
Fig. 4 is corresponding mode pattern simulation result；
Fig. 5 is can to realize single mode transport in the single mode transport method based on mode cutoff in photon band gap of the invention
Wave band schematic diagram；
Fig. 6 is the pattern relative intensity that optical fiber is obtained in 1550-1555nm wave bands and 1425-1430nm wave band measurements respectively
With the graph of a relation of group delay；
Fig. 7 is the mode pattern that optical fiber measurement is obtained；
Fig. 8 is graph of a relation of the bandwidth with clad material refractive index of single mode transport wave band in the present invention；
Fig. 9 is graph of a relation of the bandwidth with optical fiber dutycycle of single mode transport wave band in the present invention；
Figure 10 is the graph of a relation of the bandwidth chamfering relative with covering airport of single mode transport wave band in the present invention；
Figure 11 is the graph of a relation of single mode transport operation wavelength chamfering relative with covering airport in the present invention；
Figure 12 is the relative chamfering d of regulation in embodimentCSingle mode transport region when/d is 0.63.
Embodiment
Below in conjunction with accompanying drawing and example, the present invention is described in further detail.
The present invention is a kind of single mode transport method based on mode cutoff in photon band gap, with 7 core photon band gap light
Exemplified by fibre, fiber model is as shown in Figure 1.As a kind of microstructured optical fibers, the composition of hollow core photonic bandgap fiber is complex, deposits
In many kinds of structural parameters, mainly include covering airport periods lambda, air bore dia d, air Hole chamfering dCIt is empty with first layer
Stomata chamfering dpWith d`C, fibre core chamfering rc, fibre core ring thickness th、tpWith core diameter RCDeng as shown in Figure 2.
The properties such as the mode distributions of hollow core photonic bandgap fiber are directly related with optical fiber structure, are illustrated in figure 3 in optical fiber
Each pattern b~I effective refractive index and the relation curve of wavelength, Fig. 4 is corresponding mode pattern.Because fibre core is nonideal
Difference in dodecagon, therefore mode simulation result and circular ideal fibre core, but still can be by the electric field side in mould field section
It is divided into three groups to judgment model type, and by core mode：It is basic mode LP respectively01, second order mode LP11And three rank moulds (b-d)
LP21(e-f)；There are three relatively stable surface modes (g-I) on the left of band gap in addition.
The detailed simulation result enlarged drawing of dashed rectangle part is as shown in figure 5, different higher order modes is by photonic band in Fig. 3
Wavelength when gap is ended is different, namely with different cut-off characteristicses, wherein in about 1.392~1.430 mu m wavebands, high-order mode
Formula (more than second order mode) is all ended by band gap and basic mode can stablize transmission, therefore can realize light using the wave band in theory
Fine quasi- single mode transport.
To optical fiber 1550-1555nm wave bands and 1425-1430nm wave bands enter row mode measurement, the relative intensity of pattern with
The relation curve of group delay is as shown in fig. 6, corresponding mode pattern is as shown in Figure 7.Can be according to each height when group delay is smaller
The shape of rank mould pattern is apparent from the corresponding pattern of each spike：(b)LP01、(c-e)LP11And (f-g) LP21, experiment
As a result it is coincide with mode simulation result.By the contrast of relative intensity-group delay relation curve, in 1430nm wave band high-orders
Pattern is by strong suppression, and measurement result is only capable of decompositing a second mode, and relative intensity and the high-order of 1550nm wave bands
Mould is compared to about 20dB is reduced, so being strongly inhibited in the wave band higher order mode, mode suppression is than up to 60dB, it is possible to achieve
The quasi- single mode transport of hollow core photonic bandgap fiber.
For single mode transport method of the present invention based on mode cutoff in photon band gap, key parameter is single mode transport
The bandwidth of wave band, increase bandwidth can improve the applicability of single mode transport design.Single mode transport wave band is by basic mode and second order mode
Cutoff wavelength is determined, therefore the property that maximum factor is optical fiber photon band gap is influenceed on single mode transport wave band.Photon band gap
Property is related to the cladding structure parameter of optical fiber, mainly includes clad material refractive index n, optical fiber dutycycle d/ Λ and covering air
Hole chamfering dC.Said structure parameter is optimized, increases the single mode transport band of optical fiber, optical fiber is met required wave band
Quasi- single mode transport.
Because the mode characteristic curve of band gap edge basic mode has the very high linearity, and slope is smaller, in order to fixed
Influence of the analysis optical fiber parameter in amount ground to single mode transport wave band, a horizontal linear is reduced to by the mode characteristic curve of basic mode,
The then bandwidth of λ of single mode transport wave bandSIt can be expressed as：
λ S=Δs neff/ | k | (1)
Wherein k is the slope of band gap left side edge, Δ neffThe effective mould for being second order mode between cut-off wave strong point and basic mode
Formula refringence.
A. clad material refractive index optimizes
The core mode of hollow core photonic bandgap fiber has small part Energy distribution in cladding structure, therefore clad material
Refractive index n can have certain influence on mode characteristic.When n brings up to 2 from 1.2, single mode transport band λSChange such as
Shown in Fig. 8.As a result show, the bandwidth of single mode transport wave band increases with the increase of refractive index.Hollow core photonic bandgap fiber mould
During type initial parameter n=1.445, λSAbout 36.5nm；λ during refractive index n=1.62SAbout 48.5nm, improves 33%, and works as n
When=2, λSUp to 104.3nm, about the 2.9 of initial configuration times.Therefore, increase clad material refractive index can be significantly expanded list
Mould transmits band.
B. dutycycle optimizes
The ratio d/ Λ of hollow core photonic bandgap fiber covering air bore dia and pitch-row, or be that dutycycle is fiber design
During a very important parameter, the size of dutycycle directly affects the distribution of the bandwidth and pattern of band gap.Work as duty
Than d/ Λ from 0.94 to 0.99 change when, single mode transport band λSVariation tendency it is as shown in Figure 9.As a result show, when accounting for
When sky is than increase, the bandwidth of λ of single mode transport wave bandSIt is gradually reduced, but when d/ Λ are between 0.962 to 0.979, λSAlmost protect
Hold constant, be only reduced to 35.8nm from 37.2nm；λ when d/ Λ continue to increaseSIt is greatly reduced, during d/ Λ=0.99, bandwidth subtracts
As low as 21.2nm.
C. covering air Hole chamfering optimizes
In order to calculate influence of the covering air Hole chamfering to single mode transport wave band, chamfering diameter and airport are used during emulation
Diameter ratio dC/ d characterizes chamfering angle size, works as dCWhen/d changes between 0.2 to 0.8, single mode transport band λSChange
Trend is as shown in Figure 10.As a result show to work as dCSingle mode transport band gradually increases after/d is more than 0.3, but band in calculating process
Wide excursion only has 8nm, is respectively equivalent to λ when dutycycle and refraction index changingSThe 31% of excursion and 9%, therefore
The change of covering air Hole chamfering is relatively small for the influence of single mode transport band.
But when covering chamfering changes, large range of movement can spectrally occur for photon band gap.As shown in figure 11, with
The gradually increase of chamfering, higher order mode cutoff wavelength λmTowards the movement of long wave length direction, from dC1.34um during/d=0.2 is arrived
dC1.65um during/d=0.8.Therefore change covering chamfering can be assign as the method for adjustment for moving single mode transport service band.
The present invention is a kind of single mode transport method based on mode cutoff in photon band gap, using on the left of photon band gap
The single mode transport wave band of presence, transmits basic mode and high-order mode is strongly inhibited, it is achieved thereby that the list in service band
Mould is transmitted, and by selecting appropriate Refractive Index of Material, dutycycle and covering chamfering, can neatly realize hollow core photonic bandgap light
The fine single mode transport under different bandwidth, different-waveband.
Embodiment：The operation wavelength of optical fibre gyro application is generally 1530nm wave bands, more than bandwidth 30nm, it is therefore desirable to adjust
Whole optical fiber structure makes it at least realize single mode transport in 1530 ± 15nm wave band.Mode cutoff is based on according to the present invention
Single mode transport method, on the basis of existing fiber, keep other specification constant, by covering airport with respect to chamfering dC/ d is improved
To 0.63, the structural parameters of optical fiber are as shown in table 1.Now the basic mode of optical fiber and the mode characteristic curve and single mode of second order mode are passed
Defeated region as shown in figure 12, wherein can realize quasi- single mode transport in 1499-1545nm wave bands, meets optical fibre gyro and applies need
Ask.
Table 1 is the relative chamfering d of regulationCThe structural parameters of single-mode transmission optical fiber when/d is 0.63
Due to the multi-mode feature of hollow core photonic bandgap fiber, the existing design method for realizing single mode transport has especially multiple
Miscellaneous structure design, the requirement to drawing process is very high.Single mode of the present invention based on mode cutoff in photon band gap is passed
Transmission method, can be on the basis of existing 7 core photon band-gap optical fiber, by the adjustment to optical fiber structure parameter, in single mode transport
Wave band makes all higher order modes be effectively suppressed, and realizes quasi- single mode transport.Drawing process need not be changed, and optical fiber structure is existing
Real feasible, the Light source line width such as the optical fibre gyro that is particularly suitable for use in is narrower and has the applied field of high requirement to optical fiber transmission quality
Close.
Claims (2)
1. a kind of single mode transport method based on mode cutoff in photon band gap, it is characterised in that：
Described single mode transport method is realized especially by following steps：
The first step, according to the relation curve of the effective refractive index of each pattern and wavelength in optical fiber, is divided at least two by core mode
Group, one of which is basic mode, and remaining is high-order mode；
Second step, is emulated to basic mode, determines the cut-off wave band of the wave band that high-order mode is all ended by band gap, i.e. single mode；
3rd step, structure parameter optimizing increases the bandwidth of single mode transport wave band, realizes the single mode transport under different operating wavelength；
The mode characteristic curve of basic mode is reduced to a horizontal linear, then the bandwidth of λ of single mode transport wave bandSIt is expressed as：
λS=Δ neff/|k|
Wherein, k is the slope of band gap left side edge, Δ neffFor effective model of the second order mode between cut-off wave strong point and basic mode
Refringence.
2. a kind of single mode transport method based on mode cutoff in photon band gap according to claim 1, its feature
It is：Shown structure parameter optimizing includes：
It is 1.2~2 to adjust clad material refractive index, and dutycycle d/ Λ are between 0.962 to 0.979 for adjustment, change covering chamfering
Mobile single mode transport service band.
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Citations (5)
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|---|---|---|---|---|
| JP2004233686A (en) * | 2003-01-30 | 2004-08-19 | Mitsubishi Cable Ind Ltd | Light transmission method |
| CN101414026A (en) * | 2008-10-30 | 2009-04-22 | 北京航空航天大学 | High non-linear single polarization single-mould photonic crystal fiber |
| US7873251B2 (en) * | 2003-08-01 | 2011-01-18 | Bayya Shyam S | Photonic band gap germanate glass fibers |
| JP2011170173A (en) * | 2010-02-19 | 2011-09-01 | Nippon Telegr & Teleph Corp <Ntt> | Photonic band gap fiber |
| CN105954830A (en) * | 2016-01-28 | 2016-09-21 | 合肥工业大学 | Broadband single polarization single-mode photonic crystal fiber |
-
2017
- 2017-08-21 CN CN201710719524.XA patent/CN107329204B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004233686A (en) * | 2003-01-30 | 2004-08-19 | Mitsubishi Cable Ind Ltd | Light transmission method |
| US7873251B2 (en) * | 2003-08-01 | 2011-01-18 | Bayya Shyam S | Photonic band gap germanate glass fibers |
| CN101414026A (en) * | 2008-10-30 | 2009-04-22 | 北京航空航天大学 | High non-linear single polarization single-mould photonic crystal fiber |
| JP2011170173A (en) * | 2010-02-19 | 2011-09-01 | Nippon Telegr & Teleph Corp <Ntt> | Photonic band gap fiber |
| CN105954830A (en) * | 2016-01-28 | 2016-09-21 | 合肥工业大学 | Broadband single polarization single-mode photonic crystal fiber |
Non-Patent Citations (2)
| Title |
|---|
| K. SAITOH ET AL.: "Air-core photonic band-gap fibers:the impact of surface modes", 《OPTICS EXPRESS》 * |
| 张虎 等: "基于正方形格子的空芯光子带隙光纤的模式特性和泄漏损耗", 《物理学报》 * |
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