CN103645535A - High double-refraction terahertz optical fiber - Google Patents
High double-refraction terahertz optical fiber Download PDFInfo
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- CN103645535A CN103645535A CN201310667064.2A CN201310667064A CN103645535A CN 103645535 A CN103645535 A CN 103645535A CN 201310667064 A CN201310667064 A CN 201310667064A CN 103645535 A CN103645535 A CN 103645535A
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Abstract
The invention discloses a terahertz optical fiber comprising layered media (1) and a medium round tube (3). The terahertz optical fiber is characterized in that the layered media (1) are arranged in the medium round tube (3) with the same interval in two directions, a diamond-shaped cross structure is formed by the layered media (1) in two directions at the center of the medium round tube (3), an acute angle theta formed by the cross connection of the two directions is larger than or equal to 40 degrees and is less than or equal to 70 degrees, four air holes (4) are formed by the diamond-shaped cross structure and the medium round tube (3), the layered media (1) are fixed on the medium round tube (3), the layered media (1) at the diamond-shaped cross structure part and an air layer (2) are a fiber core, and the layered media (1) outside the diamond-shaped cross structure part, the air layer (2), the medium round tube (3) and the air holes (4) are a cladding layer. The whole body of the terahertz optical fiber is a total internal reflection structure. The fiber is suitable for terahertz wave transmission and has the advantages of low loss and high double-refraction rate.
Description
Technical field
The present invention relates to fiber optic communication field, relate in particular to the optical fiber of transmission THz wave.
Background technology
Terahertz (Terahertz, THz) typically refers to the electromagnetic wave of frequency within the scope of 0. 1 ~ 10 THz, the microwave of its wave band in electromagnetic wave spectrum and infrared between.THz radiation is in a lot of fields, as communication, sensing, imaging, spectroscopy and medical science have the potentiality of application.In recent years, increasing seminar has both at home and abroad carried out the research of low-loss THz waveguide, and because material has very strong absorption to THz ripple, reducing material absorption loss is the emphasis that people study THz waveguide, existing optical fiber is designed with sub-wavelength optical fiber, porous optical fiber and hollow optic fibre etc.Its main thought is that core mode energy is more distributed in air, thereby effectively reduces material absorption loss.
Because high birefringence optical fiber has important application in fields such as optical signal detecting and processing, increasing seminar has both at home and abroad carried out the research of low-loss high birefringence THz waveguide recently.Haibin Chen etc. has proposed a kind of high birefringence THz porous optical fiber, in its fibre core and fibre core, airport shape is ellipse, therefore optical fiber has high birefringent characteristic, but in this fibre core and fibre core, the non-circular of airport prepared and brought difficulty [Haibin Chen to optical fiber, et al., " Squeezed lattice elliptical-hole terahertz fiber with high birefringence, " Applied Optics, 2009
48(20): 3943].Given this, document [Daru Chen, et al., " Highly birefringent terahertz fibers based on super-vell structure, " Journal of lightwave technology, 2010,
28(12): 1858] a kind of new high birefringence THz porous optical fiber with hyperelement structure has been proposed, the dumbbell shape being comprised of circular airport or rhombus type structural unit are that optical fiber has been introduced high birefringence characteristic, and each airport is circle, is beneficial to fibre-optical drawing.Document [S. Atakaramians, et al., " THz porous fibers:design, fabrication and experimental characterization, " Opt. Express, 2009,
17(16): 14053] disclose a kind of high birefringence porous optical fiber based on rectangular opening structure, its birefringence can reach 0.012.Document [Fu Xiaoxia etc., " for low-loss, the high birefringence optical fiber research of THz wave transmission, " Acta Physica Sinica, 2011,
60(7): 074222] its structure is transformed and optimized, the characteristic that improved its birefringence.But the high birefringence THz optical fiber that above institute has proposed can be summed up as porous optical fiber, and the air of all take outside porous fibre core is covering, so its THz wave transfer characteristic is subject to the interference of fibre core external environment, and inconvenience contacts, wayward.Document [M. Cho, et al., " Highly birefringent terahertz polarization maintaining plastic photonic crystal fibers, " Opt. Express, 2008,
16(1): 7] proposed the high birefringence Hz optical fiber that fibre core is comprised of two real plugs, THz wave transfer characteristic is not subject to external interference, and its birefringence can reach 0.021.But fibre core guided modes is mainly to transmit in host material, and its absorption loss cannot reduce.
Summary of the invention
For above deficiency, the invention provides a kind of high birefringence THz ripple microstructured optical fibers that can realize low-loss, broadband and avoid external disturbance.
Technical scheme of the present invention is: a kind of high birefringence Hz optical fiber, comprise layered medium and medium pipe, layered medium is arranged in medium pipe so that both direction is equally spaced respectively, and the layered medium of both direction is formed centrally diamond crossing structure in medium pipe, the scope that described both direction intersects formed acute angle theta is: 40
o≤ θ≤70
o; Described diamond crossing structure and described medium pipe form four airports; Layered medium is fixed on medium pipe; The layered medium of described diamond crossing structure division and air layer are fibre core, and layered medium (1), air layer and medium pipe and airport beyond described orthohormbic structure are covering.
The layered medium cycle of arranging is Λ, and dielectric layer width is d, and medium pipe interior diameter is D, and thickness is D
1.
If the dielectric layer cycle of arranging is that Λ is constant, its width d reduces to reduce fibre core air fill factor, curve factor f
1thereby, reach the object that reduces material absorption loss, but width d is narrow, can increase manufacture difficulty, also can reduce f simultaneously
1with f
2between poor, increase limitation loss, therefore require dielectric layer width d>=10 μ m here.
For guaranteeing that fibre core basic mode is effectively limited in fibre core, require f
1with f
2ratio lower than 0.9.
For obtaining the optical fiber of low-loss high birefringence value, require 40
o≤ θ≤70
o.
Technique effect of the present invention is: fibre core air fill factor, curve factor can be expressed as f
1=(Λ-d)
2/ Λ
2, the air fill factor, curve factor of covering laminate areas of dielectric is f
2=(Λ-d)/Λ, f
1<f
2, fibre core guided modes can effectively be strapped in fibre core, and the variation of optical fiber external environment does not exert an influence to the transmission of THz ripple, is convenient to application in practice.Airport in fibre core and fibre core is parallelogram, and fibre core basic mode has high birefringence characteristic.Because fibre core is porous, core mode energy can more be distributed in airport, effectively reduces absorption loss, can realize the transmission of THz wavelength distance in addition.Outer thicker medium pipe can stable fiber structure, is convenient to optical fiber fabrication.
Accompanying drawing explanation
Fig. 1 is high birefringence optical fiber structural representation of the present invention;
Fig. 2 is that the birefringence of Fig. 1 embodiment is with the change curve of angle theta;
Fig. 3 is that the absorption loss of Fig. 1 embodiment is with the change curve of angle theta;
Fig. 4 is that the limitation loss of Fig. 1 embodiment is with the change curve of angle theta;
Fig. 5 is that the birefringence of Fig. 1 embodiment is with the change curve of frequency;
Fig. 6 is that the absorption loss of Fig. 1 embodiment is with the change curve of frequency;
Fig. 7 is that the limitation loss of Fig. 1 embodiment is with the change curve of frequency;
Fig. 8 is that the birefringence of Fig. 1 embodiment is with the change curve of periods lambda;
Fig. 9 is that the absorption loss of Fig. 1 embodiment is with the change curve of periods lambda;
Figure 10 is that the limitation loss of Fig. 1 embodiment is with the change curve of periods lambda;
Figure 11 is the x polarization mode electric field strength distribution plan of Fig. 1 embodiment;
Figure 12 is the y polarization mode electric field strength distribution plan of Fig. 1 embodiment.
Embodiment
Fig. 1 has provided the cross sectional representation of porous optical fiber of the present invention, optical fiber comprises fibre core and covering, layered medium 1 and the air layer 2 of periodic distribution are alternately arranged, arragement direction becomes θ/2 jiao with x axle, in the identical structure of arranging about the axisymmetric position of x, and form rock-steady structure by the medium pipe 3 in outside.Intersection is as the fibre core of optical fiber, and medium pipe 3 and four large airports 4 in the layered medium 1 beyond intersection, air layer 2, outside are fibre cladding, and integral body is total internal reflection structure.Fibre core air fill factor, curve factor can be expressed as f
1=(Λ-d)
2/ Λ
2, the air fill factor, curve factor of covering laminate areas of dielectric is f
2=(Λ-d)/Λ, f
1<f
2, fibre core guided modes can effectively be strapped in fibre core.
In airport, fill air, refractive index is n
air=1.0, the host material of optical fiber is elected teflon as, its refractive index n=1.5, and material absorption loss is elected 130dB/m as.
The absorption loss of basic mode is expressed as:
Wherein, Sz is the Poynting vector of z direction, and subscript x and total represent respectively material area and overall area.
Embodiment mono-:
The structure of porous doped core optical fiber as shown in Figure 1, during the teflon width=20 μ m of stratiform, periods lambda=60 μ m, tetrafluoroethene pipe interior diameter is D=1400 μ m, tetrafluoroethene circular tube thickness is D
1=200 μ m.
Fig. 2 has provided the change curve of birefringence with angle theta, as can be seen from Figure, and when θ is 90
otime, birefringence is 0, along with diminishing of θ angle, birefringence starts to increase, when θ=30
otime, birefringence can reach 0.072, the reason that causes high birefringence is that the ratio of x polarization mode energy in material that diminish with θ angle increases and the ratio of y polarization mode energy in material reduces, this characteristic also causes the increase of x polarization mode absorption loss and the reduction of y polarization mode absorption loss, as shown in Figure 3.Fig. 4 has provided the limitation loss of two polarization modes with the variation of angle theta, and along with the reduction of θ, the limitation loss of x polarization mode changes little, and close to zero loss, the limitation loss of y polarization mode increases, even if but be 30 at θ
otime, the limitation loss of y polarization mode is only just 0.0000027dB/cm, this value is much smaller than the magnitude of absorption loss, little on total losses impact.Two polarization modes can be effectively limited in fibre core.
Because the reduction of x polarization mode absorption loss with θ increases, for obtaining low-loss birefringence fiber, require θ>=40 here
o.Birefringence reduces along with the increase of θ, for obtaining the optical fiber with high birefringence, requires θ≤70 here
o.
Fixed angle θ=40
o, with the variation of frequency as shown in Figure 5, within the scope of 0.5-1.6THz, birefringence remains on 10 in birefringence
-2magnitude.Fig. 6 has shown the variation of absorption loss with frequency, increase along with frequency, the absorption loss of two polarization modes all increases, this is the reason increasing gradually due to the distribution of fibre core basic mode energy in material, at 1.6THz place, x polarization mode absorption loss is 0.74dB/cm, and y polarization mode absorption loss is 0.57dB/cm.Fig. 7 has shown the variation of limitation loss with frequency, for x polarization mode, its limitation loss is almost close to zero loss, and for y polarization mode, only in frequency, be less than the place of 0.7THz, its limitation loss just can increase gradually, therefore within the scope of 0.7-1.6THz, THz ripple can be in this optical fiber low-loss transmission, and there is high birefringence characteristic.
Fixed angle θ=40
o, frequency is 1THz, and Fig. 8 has provided the change curve of birefringence with the periods lambda of arranging, and along with the increase of Λ, birefringence numerical value first increases, and increases to after maximal value and declines gradually, even if but at μ m place, Λ=110, birefringence value still can reach 0.62.The teflon width d of stratiform is constant, and Λ increases, present air fill factor, curve factor f
1increase, thereby absorption loss can reduce.Fig. 9 has provided the change curve of absorption loss with the periods lambda of arranging, and along with the increase of Λ, the absorption loss of two polarization modes all decreases.Figure 10 has provided the change curve of limitation loss with the periods lambda of arranging, and for x polarization mode, the ratio of its mould energy in material is relatively many, so its limitation loss changes hardly, and limitation loss is far below absorption loss, little on total losses impact.For y polarization mode, along with the increase of the periods lambda of arranging, its limitation loss increases gradually, and at μ m place, Λ=110, the limitation loss of y polarization mode is 0.00132dB/cm, still than little two orders of magnitude of limitation loss.
For keeping fibre core basic mode to there is low limitation loss, require Λ≤110 μ m here, in addition for guaranteeing that fibre core basic mode has low absorption loss, requires Λ >=60 μ m.
μ m periods lambda=60, the teflon width=20 μ m of stratiform, angle θ=40
owhen frequency is 1THz, the electric field strength distribution plan of x polarization mode and y polarization mode is respectively by shown in Figure 11 and Figure 12, the distribution proportion of x polarization mode energy in material is higher than y polarization mode as can be seen from Figure, therefore can obtain high birefraction, x polarization mode and y polarization mode are effectively limited in fiber core and are transmitted simultaneously, and THz ripple transmits and is not subject to external environmental interference in optical fiber, and this point is better than porous optical fiber.
Above-mentioned accompanying drawing is only explanatory view, protection scope of the present invention is not formed to restriction.Should be understood that this embodiment just in order to demonstrate the invention, but not limit the scope of the invention by any way.
Claims (5)
1. a high birefringence Hz optical fiber, comprise layered medium (1) and medium pipe (3), it is characterized in that, layered medium (1) is arranged in medium pipe (3) so that both direction is equally spaced respectively, and the layered medium of both direction (1) is formed centrally diamond crossing structure in medium pipe (3), the scope that described both direction intersects formed acute angle theta is: 40
o≤ θ≤70
o; Described diamond crossing structure and described medium pipe (3) form four airports (4); Layered medium (1) is fixed on medium pipe (3); The layered medium of described diamond crossing structure division (1) and air layer (2) are fibre core, and layered medium (1), air layer (2) and medium pipe (3) and airport (4) beyond described orthohormbic structure are covering.
2. a kind of high birefringence Hz optical fiber according to claim 1, is characterized in that: the width d >=10 μ m of described layered medium (1).
3. a kind of high birefringence Hz optical fiber according to claim 1, is characterized in that: described shape medium (1) periods lambda of arranging should be: 60 μ m≤Λ≤110 μ m.
4. a kind of high birefringence Hz optical fiber according to claim 1, is characterized in that: require f
1/ f
2≤ 0.9, wherein, fibre core air fill factor, curve factor is f
1=(Λ-d)
2/ Λ
2, the air fill factor, curve factor of covering laminate areas of dielectric is f
2=(Λ-d)/Λ, f
1<f
2, the layered medium cycle of arranging is Λ, layered medium layer width is d.
5. a kind of high birefringence Hz optical fiber according to claim 1, is characterized in that: described layered medium quantity on both direction is identical.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109143462A (en) * | 2018-10-12 | 2019-01-04 | 西安邮电大学 | A kind of high birefringence dung beetle shape fibre core photonic crystal fiber |
| CN110361813A (en) * | 2019-08-16 | 2019-10-22 | 江西师范大学 | A kind of twin-core Hz optical fiber coupler |
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Patent Citations (8)
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| WO2004046777A1 (en) * | 2002-11-21 | 2004-06-03 | Cactus Fiber Pty Ltd | Microstructured polymer signal guiding element |
| US20080025680A1 (en) * | 2006-07-27 | 2008-01-31 | National Taiwan University | Plastic waveguide for terahertz wave |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109143462A (en) * | 2018-10-12 | 2019-01-04 | 西安邮电大学 | A kind of high birefringence dung beetle shape fibre core photonic crystal fiber |
| CN110361813A (en) * | 2019-08-16 | 2019-10-22 | 江西师范大学 | A kind of twin-core Hz optical fiber coupler |
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