The single mode single polarization photonic crystal fiber of the oval mixing air of a kind of circle hole array
Affiliated technical field
Present patent application relates to a kind of single mode single polarization photonic crystal fiber structure, is specifically related to the single mode single polarization photonic crystal fiber of the oval mixing air of a kind of circle hole array, can be widely used in the fields such as nonlinear optics, optical communication, sensing.
Background technology
[1J.C.Knight since Britain scientific worker in 1996 develops article one photonic crystal fiber, et al, Opt.Lett.1996,21 (19): 1547~1549.], photonic crystal fiber with its structural design flexibly, have extensive concern and a further investigation [1 that the incomparable characteristics such as outstanding advantages of ordinary optic fibre have obtained the scientific worker; 2J.C.Knight, et al, Science, 1998,282:1476~1478; 3P.St.J.Russell, Science, 2003,299:358~362.], and so that photonic crystal fiber is widely used in the fields such as nonlinear optics, optical communication, sensing, application prospect is unusually wide.In recent years, by reasonably changing the Design of Photonic Crystal Fiber structure, can in certain bandwidth range, successfully realize the running of single mode list polarization.The single mode single polarization photonic crystal fiber can effectively be eliminated polarization mode dispersion and polarization mode coupling, has obtained close attention and widespread use in various fields such as high-capacity optical fiber laser, sensing, optical communications.Correlative study group has studied the single mode single polarization photonic crystal fiber in succession, realized in the 50nm bandwidth that near the 1550nm wave band single mode list polarization uses [4Daniel A.Nolan, et al, Opt.Lett.2004,29 (16): 1855~1857.], the 220nm bandwidth range is realized single polarization running [5J.R.Folkenberg et al.Opt.Lett.2005 near wavelength 727nm, 30 (12): 1446~1448.], realized single mode list polarization running [6Jian Ju in 1300nm wave band 84.7nm bandwidth and 1550nm wave band 103.5nm bandwidth range, et al.J.Lightwave Technol.2006,24 (2): 825~830.], realized single mode list polarization running [the 7Fangdi Zhang et al.J.LightwaveTechnol.2007 from the 460nm bandwidth, 25 (5): 1184~1189.], realized single mode list polarization running [the 8Ming-Yang Chen etal.J.Lightwave Technol.2010 of 560nm bandwidth, 28 (10): 1443~1446.], realized single mode list polarization running [the 9Dora Juan Juan Hu of 250nm bandwidth, et al.Appl.Opt.2009,48 (20): 4038~4043.], it is 120nm[10Kunimasa Saitoh et al that low-loss single-mode list polarization uses bandwidth, IEEE Photonics Technology Letters, 2003,15 (10): 1384~1386.], studied single mode list polarization running [the 11Hongjun Zheng et al.Optical Engineering of 600nm bandwidth, 2011,50 (12), 125003-1~6.].This paper has proposed a kind of novel circle, the photonic crystal fiber of oval airport mixing dot matrix covering, purpose is to realize the characteristics such as the running of single mode list polarization, dispersion flattene, negative dispersion of wide bandwidth more, support thereby provide theoretical for photonic crystal Transmission Fibers and related device thereof etc. are practical, to remedy single-mode single-polarization cable in the previous literature research aspect the wide bandwidth more and do not relate to the deficiency of the aspects such as dispersion; And adopt full Vector Finite-Element Method and perfect matching layer boundary Conditions the characteristic such as single polarization of the single mode single polarization photonic crystal fiber that proposes, dispersion flattene, negative dispersion with the lambda1-wavelength situation of change.
The utility model content
Present patent application has proposed the single mode single polarization photonic crystal fiber of the oval mixing air of a kind of circle hole array, realized the more single mode list polarization running of wide bandwidth, dispersion flattene, thereby provide support for fibre optic polarizer, photonic crystal Transmission Fibers etc. are practical, to replenish above-mentioned literature research aspect the bandwidth and do not relate to the deficiency of the aspects such as dispersion; And the various characteristics of the single mode single polarization photonic crystal fiber that proposes and various parameter have been provided with the incident wavelength Changing Pattern.
Present patent application solves the technical scheme that its technical matters adopts:
The single mode single polarization photonic crystal fiber xsect that present patent application proposes is comprised of pure silicon dioxide matrix and circle, oval airport dot matrix on the whole, the optical fiber inner cladding is quadrate array by circular airport to be arranged, and surrounding layer is hexagonal array by three layers of oval airport and arranges.The oval airport dot matrix of covering hexagonal lattice has guaranteed that the limitation loss of x polarization mode is enough little so that optical fiber has the single mode birefringent characteristic, has increased the limitation loss of y polarization mode, makes the y polarization mode obtain enough decay, thereby realizes that single mode list polarization uses.The circular airport dot matrix of inner cladding makes optical fiber have lower dispersion.
The beneficial effect of present patent application is:
Realized the utilization of wide bandwidth single mode list polarization; In lambda1-wavelength 1.193 μ m to 1.384 mu m ranges, this optical fiber presents wide bandwidth, color dispersion plainness characteristic and larger birefringent characteristic, makes it have broad prospect of application in fields such as light transmission.This optical fiber has the negative dispersion zone of 500nm scope, can be used for the dispersion compensation of conventional fiber L-band.
Description of drawings
Fig. 1 is the cross sectional representation of present patent application photonic crystal fiber.
The Electric Field Distribution of x and y polarization mode when Fig. 2 is lambda1-wavelength 1.550 μ m, arrow represents the polarization direction; Lateral arrows characterizes x polarization mode electric field (a), and vertically arrow characterizes y polarization mode electric field (b).
Shown in Figure 3 is that the effective refractive index of single mode single polarization photonic crystal fiber and mode birefringence are with the variation of lambda1-wavelength.Solid line with small circle and blockage among Fig. 3 (a) represents respectively the effective refractive index of x and y polarization mode with the variation of lambda1-wavelength, represents that with little leg-of-mutton solid line mode birefringence (being effective refractive index poor of y and x polarization mode) is with the variation of lambda1-wavelength among Fig. 3 (b).
Shown in Figure 4 is that limitation loss and difference thereof are with the variation of lambda1-wavelength.Among Fig. 4 (a) with the solid line of small circle and blockage be respectively the limitation loss of x and y polarization mode with the variation of lambda1-wavelength, adopt semilog coordinate among the figure; Among Fig. 4 (b) solid line be the limitation loss difference of y polarization mode and x polarization mode with the variation of lambda1-wavelength, the limitation loss difference adopts semilog coordinate among the figure.
Shown in Figure 5 is that the dispersion of single mode single polarization photonic crystal fiber is with the variation of lambda1-wavelength.
Embodiment
Below in conjunction with accompanying drawing and enforcement present patent application is further specified.
Fig. 1 is the cross sectional representation of single mode single polarization photonic crystal fiber.Formed with oval airport by pure silicon dioxide matrix and circle on this optical fiber integrally.The optical fiber inner cladding is quadrate array by circular airport to be arranged, and surrounding layer is hexagonal array by three layers of oval airport and arranges.The oval airport dot matrix of covering hexagonal lattice has guaranteed that the limitation loss of x polarization mode is enough little so that optical fiber has the single mode birefringent characteristic, has increased the limitation loss of y polarization mode, makes the y polarization mode obtain enough decay, thereby realizes that single mode list polarization uses.The circular airport dot matrix of inner cladding makes optical fiber have lower dispersion.Gray area is pure silicon dioxide among the figure, circle and the ellipse representation airport of white, peripheral solid-line rectangle region representation perfect matching layer border.The radius a=0.45 μ m of circular airport, circular airport be spaced apart Λ 1=1.0 μ m.Large oval airport is expressed as respectively a and b along the radius of x and y axle, airport be spaced apart Λ 2=1.8 μ m, oval ratio is η=b/a=2.Wherein, a=0.45, b=2a=0.9 μ m.The refractive index of silicon dioxide and airport is respectively 1.45 and 1.The Characteristics of modes of transmission electromagnetic field can change by shape and the space distribution that changes these airports in optical fiber.
The Electric Field Distribution of x and y polarization mode when Fig. 2 is lambda1-wavelength 1.550 μ m, arrow represents the polarization direction; Lateral arrows represents x polarization mode (a), and vertically arrow represents y polarization mode (b).As seen from Figure 2, the electric field of two polarization modes is symmetrical about fiber optic hub x axle and y axle, and x polarization mode electric field is obviously much smaller to the expansion of covering than y polarization mode electric field to the expansion of covering.This limitation loss that shows the y polarization mode is more much bigger than the limitation loss of x polarization mode.At this moment, mode birefringence is 1.458 * 10
-2, clap the long 0.106mm that is; The limitation loss of x and y polarization mode is respectively 3.10 * 10
-4DB/km and 1.721dB/km.If calculate according to present general communication system emission power 0dBm, span 80km, incident light transmits 80km in this optical fiber after, the power attenuation of x polarization mode is to-2.48 * 10
-3DBm, the power attenuation of y polarization mode is to-137.680dBm, and the real background noise of the sensitive detection parts such as routine spectra instrument is-60dBm about, like this, the x polarization mode can be detected and amplify, and the y polarization mode is attenuated in Optical Fiber Transmission, thereby realizes that single mode list polarization uses; The numerical aperture of x polarization mode is 0.447, and effectively mode field area is 3.066 μ m
2, nonlinear factor is 34.373W
-1/ km.When lambda1-wavelength increased, the y polarization mode will be attenuated in the shorter distance of this Optical Fiber Transmission; This optical fiber can be widely used in the different optical fibre devices.
Fig. 3 is that single mode single polarization photonic crystal fiber effective refractive index and mode birefringence are along with the variation of lambda1-wavelength.The effective refractive index that represents respectively x and y polarization mode among Fig. 3 (a) with the solid line of small circle and blockage represents that with the solid line of triangle mode birefringence (being the absolute value of difference of the effective refractive index of y and x polarization mode) is with the variation of lambda1-wavelength among Fig. 3 (b).Fig. 3 can obtain, and the effective refractive index of the x of this optical fiber and y polarization mode reduces and increases with lambda1-wavelength; The effective refractive index of x polarization mode reduces to be reduced to be increased to 1.256 by 1.409 with wavelength by 1.284 effective refractive indexs that are increased to 1.413, y polarization mode with wavelength; Corresponding same lambda1-wavelength, the effective refractive index of y polarization mode is less than the effective refractive index of x polarization mode, and the absolute value of both differences (being mode birefringence) increases with the increase near linear of lambda1-wavelength.
Shown in Figure 4 is that limitation loss and difference thereof are with the variation of lambda1-wavelength.Among Fig. 4 (a) with the solid line of small circle and blockage be respectively the limitation loss of x and y polarization mode with the variation of lambda1-wavelength, adopt semilog coordinate among the figure; Among Fig. 4 (b) with the solid line of triangle be the limitation loss difference of y polarization mode and x polarization mode with the variation of lambda1-wavelength, the limitation loss difference adopts semilog coordinate among the figure.Can be got by Fig. 4, the limitation loss of x and y polarization mode increases sharply with the lambda1-wavelength increase; The limitation loss of x polarization mode increases by 3.854 * 10 with wavelength
-7DB/km rapidly increases to 1.757 * 104dB/km, and the limitation loss of y polarization mode increases by 8.951 * 10 with wavelength
-7DB/km rapidly increases to 1.806 * 10
7DB/km.Corresponding same lambda1-wavelength, the limitation loss of y polarization mode is obviously larger than the limitation loss of x polarization mode; In lambda1-wavelength 1.1 μ m to 2 mu m ranges, the difference of the limitation loss of the limitation loss of y polarization mode and x polarization mode is approximate index with the increase of lambda1-wavelength and increases sharply, corresponding loss difference 5.097 * 10 during by lambda1-wavelength 1.1 μ m
-7DB/km is when being increased to lambda1-wavelength 2.5 μ m corresponding 1.804 * 10
7DB/km.This shows that when lambda1-wavelength was slightly smaller than optical fiber Air hole dimension, airport hinders incident light to be strengthened to the effect of covering expansion, and the limitation loss of optical fiber reduces; When lambda1-wavelength was a bit larger tham optical fiber Air hole dimension, incident light was strengthened to the diffraction of covering by airport, and airport hinders incident light to be weakened to the effect in the covering expansion, and the limitation loss of optical fiber increases; Simultaneously, the oval airport array of y direction has increased the loss of y polarization mode effectively, and the y polarization mode is attenuated than x polarization mode is easier, thereby realizes that in this optical fiber single mode list polarization uses.According to the theory that single mode list polarization uses, can make lambda1-wavelength realize that from inherent this optical fiber of 1.55 μ m to 2.5 mu m ranges single mode list polarization uses.
Shown in Figure 5 is that the dispersion of single mode single polarization photonic crystal fiber is with the variation of lambda1-wavelength.Fig. 5 dotted line is material dispersion, and dot-and-dash line is waveguide dispersion, and solid line is the total dispersion of single mode single polarization photonic crystal fiber.The color dispersion plainness characteristic of optical fiber is the much-talked-about topic that present optical communication system and device research worker thereof need to make great efforts exploratory development.Fig. 5 can find out that material dispersion increases approximately linear with lambda1-wavelength and increases, and waveguide dispersion increases with wavelength in lambda1-wavelength 1.1 μ m to 2.5 mu m ranges and reduces rapidly; This dispersion profile has caused this optical fiber total dispersion color dispersion plainness characteristic and interior Negative Dispersion Properties in a big way in having occurred in a big way.Dispersion values at 1.193 μ m places is 83.482ps/ (kmnm), has dispersion maximal value 85.477ps/ (kmnm) at 1.286 μ m place optical fiber, and the dispersion values at 1.384 μ m places is 83.480ps/ (kmnm); As seen, this optical fiber is 2.039ps/ (kmnm) from the dispersion flattene degree (maximal value and minimum value is poor in the research wavelength band) in 1.193 μ m to 1.384 mu m ranges, be better than document [12 gardens gold brightness, marquis Lantian, Zhou Guiyao etc., photoelectron laser, 2008,19 (8): 1007-1010] the dispersion flattene degree 9ps/ (kmnm) in 0.83 μ m to 1.02 mu m range, than document [13 weekly assemblies are beautiful, Zhang Xia, Jiang Gao etc. photoelectron laser, 2009,20 (1): 28-31] the dispersion flattene degree 1.8ps/ (kmnm) in 1.480 μ m to 1.620 mu m ranges is slightly poor, and the 190nm of the dispersion flattene scope 191nm of this optical fiber and document [12] is almost identical, the 140nm and document [14T.Yamamoto, the H.Kubota that are better than document [13], S.Kawanishi, M.Tanaka, andS.Yamaguchi, Opt.Express, 2003,11 (13): 1537-1540] 100nm.This wide bandwidth, color dispersion plainness characteristic are so that this optical fiber has significant application value in communication system.When lambda1-wavelength during greater than 2.015 μ m total dispersion be negative value; When lambda1-wavelength was 2.5 μ m, total dispersion reached-125.1417ps/ (kmnm).This shows that this optical fiber can be used for the dispersion compensation of conventional fiber L-band.
In a word, the photonic crystals optical fiber structure of present patent application proposition is the effective scheme of realizing that wide bandwidth, dispersion flattened single mode list polarization use.When lambda1-wavelength 1.550 μ m, mode birefringence is 1.458 * 10
-2, clap the long 0.106mm that is; The limitation loss of x and y polarization mode is respectively 3.10 * 10
-4DB/km and 1.721dB/km compare two kinds of polarization mode loss situations, and the y polarization mode can be attenuated in very short optical fiber, thereby realize that single mode list polarization uses.Result of study shows that the novel single mode single polarization photonic crystal fiber of proposition can realize in the relative broad range of incident light 950nm that single mode list polarization uses.In lambda1-wavelength 1.193 μ m to 1.384 mu m ranges, this optical fiber presents wide band dispersion flat characteristic and birefringent characteristic, makes it have broad prospect of application in fields such as super continuous spectrums generation, burst transmissions.This optical fiber has the negative dispersion zone of 500nm scope, can be used for the dispersion compensation of conventional fiber L-band.