CN102279437A

CN102279437A - Mixed light guide elliptical double-core photonic crystal fiber

Info

Publication number: CN102279437A
Application number: CN 201110126975
Authority: CN
Inventors: 刘敏; 董传培
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2011-05-16
Filing date: 2011-05-16
Publication date: 2011-12-14

Abstract

The invention discloses a mixed light guide elliptical double-core photonic crystal fiber. A covering of the fiber is arranged in the form of triangular lattice. The fiber comprises high-refractive-index columns (1), a small air hole (2), a background material (3), a large air hole (4), a fiber core A (5) and a fiber core B (6), and is characterized in that: a plurality of high-refractive-index columns (1) parallel with the central line of the fiber are distributed at equal intervals on both sides of the central point of a fiber section along the axis x direction; the effective refractive rates n2 of the high-refractive-index columns (1) are 1.59-1.65; two high-refractive-index columns (1) are removed from both sides of the central point, so that two elliptical fiber cores, i.e., the fiber core A (5) and the fiber core B (6) are formed; all air hole gaps lambda are 3.0-4.0 mum; the diameter d1 of the large air hole (4) is 2.0-3.0 mum; the diameter d of the small air hole (2) is 2.0-2.5 mum; the effective refractive indexes nair of all holes are 1; and the effective refractive index ns of the background material (3) is 1.45. In a light splitter made of the fiber, the problem that the splitting ratio, the length of the beam splitter and the bandwidth cannot be considered simultaneously is solved effectively.

Description

The oval double-core photonic crystal fiber of a kind of mixed light-guiding

Technical field

The invention belongs to the optical fiber technology field, particularly a kind of oval double-core photonic crystal fiber that is used for polarization beam apparatus with mixed light-guiding mechanism.

Background technology

Photonic crystal fiber (Photonic Crystal Fibers, PCFs) be a research field of quietly rising in recent years, not only having important theoretical research is worth, and has an actual application value widely, owing to dirigibility and unique optical property of structural design, since coming out, just caused last century Mo the extensive concern of Chinese scholars.Because the dirigibility of photonic crystal fiber design, by selecting suitable fibre core and cladding structure, can design total internal reflection double-core photonic crystal fiber, band gap type double-core photonic crystal fiber and based on the mixed type double-core photonic crystal fiber of total internal reflection and band gap effect.The circular double-core photonic crystal fiber of common total internal reflection is used to make that the fiber lengths of polarization beam apparatus is long, and splitting ratio is low, and bandwidth range is narrow; It is long that the circular double-core photonic crystal fiber of band gap type is used to make the fiber lengths of polarization beam apparatus, the splitting ratio height, and bandwidth range is narrow, and the optical fiber parameter that designs is many, is not easy to manufacture and design.All there is the problem that can't take into account simultaneously between splitting ratio, polarization beam apparatus length and the bandwidth in above-mentioned two kinds of optical fiber that are used to make polarization beam apparatus.

Summary of the invention

Purpose of the present invention is exactly in order to overcome above-mentioned the deficiencies in the prior art, to solve the problem that can't take into account simultaneously between splitting ratio, polarization beam apparatus length and the bandwidth, providing a kind of mixed light-guiding oval double-core photonic crystal fiber.

The oval double-core photonic crystal fiber of a kind of mixed light-guiding involved in the present invention comprises high index of refraction post 1, spilehole 2, background material 3, gross blow hole 4, fibre core A5, fibre core B6; It is characterized in that: two edge x direction of principal axis at optical fiber kernel of section point equidistantly distribute some and the high index of refraction post 1 fiber optic hub line parallel, the effective refractive index n of high index of refraction post 1 ₂Be 1.59～1.65, respectively remove two high index of refraction posts 1 on the both sides of central point and form two oval fibre cores, be fibre core A5 and fibre core B6, the pore covering is made of 4 gross blow holes 4 and some spileholes 2, all pore spacings and the spacing Λ between the high index of refraction post 1 are 3.0 μ m～4.0 μ m, the diameter d of gross blow hole 4 ₁Be 2.0 μ m～3.0 μ m, the diameter d of spilehole 2 is 2.0 μ m～2.5 μ m, and 4 gross blow holes 4 are distributed in around fibre core A5 and the fibre core B6 effective refractive index n of spilehole 2 and gross blow hole 4 _AirBe 1, background material 3 is silex glass material or polymer material, its effective refractive index n _sBe 1.45.

The size that the present invention can conveniently regulate coupling length by gross blow hole diameter and pitch of holes in the oval double-core photonic crystal fiber of change mixed light-guiding; Can conveniently regulate the position of bandgap range and maximum value by the effective refractive index that changes high index of refraction column diameter and high index of refraction post, effectively solve the problem that to take into account simultaneously between splitting ratio, polarization beam apparatus length and the bandwidth.Twin-core fiber of the present invention has novel coupled characteristic, has maximum value.The present invention has less design parameter, is convenient to design and manufacturing.

Description of drawings

Fig. 1 is the cross sectional representation of the oval double-core photonic crystal fiber of mixed light-guiding of the present invention;

Wherein, 1 is the high index of refraction post, and 2 is spilehole, and 3 is background material, and 4 is gross blow hole, and 5 is oval fibre core A, and 6 is oval fibre core B.

Fig. 2 is the mould field pattern of Fig. 1 example;

Fig. 3 is different d in Fig. 1 example ₁The variation relation of coupling length under the condition;

Fig. 4 is the variation relation of coupling length under the different d conditions in Fig. 1 example;

Fig. 5 is different n in Fig. 1 example ₂The variation relation of coupling length under the condition;

Fig. 6 is the variation relation of coupling length under the different Λ conditions in Fig. 1 example;

Fig. 7 is the coupling length curve of photonic crystal fiber through obtaining after the parameter optimization in Fig. 1 example;

Fig. 8 is that the normalized energy of making polarization beam apparatus after the parameter of optimizing structure in Fig. 1 example distributes;

Fig. 9 (schemes a) and cross-talk (figure b) through the splitting ratio of making beam splitter after the parameter of optimizing structure in Fig. 1 example;

Embodiment

The present invention is further described as follows below in conjunction with drawings and Examples:

Fig. 1 is the cross sectional representation of the oval double-core photonic crystal fiber of mixed light-guiding of the present invention.As shown in Figure 1: the optical fiber background material is the silex glass material, the dielectric material of high index of refraction post for mixing, and its structural parameters are Λ=4 μ m, d/ Λ=0.5, n ₂=1.65, n _s=1.45, n _Air=1.0, d ₁=3 μ m.

The mould field distribution of mixed light-guiding double-core photonic crystal fiber as shown in Figure 2, as wavelength X=1.55 μ m, red arrow is represented the direction of electric field, wherein the energy overwhelming majority concentrates in the oval fibre core.Can know that by twin-core fiber owing to Mode Coupling evokes the even pattern and the asymmetrical strange pattern of symmetry, shown in the figure is strange pattern on the y-polarization direction.

What Fig. 3 represented is to change the gross blow hole diameter d ₁The time, make d ₁=2 μ m, d ₁=2.5 μ m, d ₁Coupling length during=3 μ m concerns with wavelength change, as can be seen from the figure, and d ₁Not not simultaneously, bandgap range does not change, and there is maximum value in the variation tendency unanimity of coupling length, presents dull ascendant trend in the left side of maximum value, presents dull downtrending on the right side of maximum value.

Shown in Figure 4 is when changing the diameter d of spilehole diameter and high index of refraction post, to make d=2 μ m, d=2.25 μ m, its coupling length of d=2.5 μ m concerns with wavelength change, as can be seen from the figure, change spilehole and high index of refraction column diameter d, the photon band gap scope can change.Along with d increase, bandgap range narrow down and hypsochromic shift moving, maximum value can move to short wavelength's direction, and maximum value is increasing.

Change the effective refractive index n of high index of refraction post ₂, make n ₂=1.59, n ₂=1.62, n ₂=1.65, its coupling length as shown in Figure 5.As can be seen from the figure, the effective refractive index of high index of refraction post has tangible influence to photon band gap, along with n ₂Increase, bandgap range broadens and moves to long wavelength's direction, the maximum point of coupling length also moves to long wavelength's direction, and coupling length shortens, coupling effect strengthens, maximum value reduces gradually.

Change the pitch of holes people, make Λ=3 μ m, Λ=3.5 μ m, Λ=4 μ m, coupling length are with the wavelength change relation as shown in Figure 6.When pitch of holes Λ increased, the band gap position of mixed light-guiding double-core photonic crystal fiber remained unchanged, but coupling length increases gradually along with the increase of Λ.

As the above analysis, as the diameter d=2 μ m of the diameter and the spilehole of high index of refraction post, gross blow hole d ₁=3 μ m, pitch of holes Λ=3 μ m, n ₂=1.65, n _s=1.45, n _Air=1.0 o'clock, the coupling length minimum, the coupling length of the parameter of optimizing structure as shown in Figure 7: the coupling length on the y-polarization direction is 450 μ m to the maximum, has the shortest coupling length.

Fig. 8 makes an embodiment of polarization beam apparatus for the optimize structure double-core photonic crystal fiber of parameter of utilization of the present invention, its normalized energy distributes as shown in Figure 8: as can be seen from the figure, when fiber lengths L=5.2mm, the energy among the fibre core A is all transferred among the fibre core B.

Fig. 9 is for being the embodiment of beam splitter of the optical fiber fabrication of the present invention of 5.2mm with length, and its splitting ratio is shown in Fig. 9 (a): as can be seen from the figure, at wavelength X=1.55 μ m, ER _A=-27.93115dB, λ=1.524 μ m～1.578 μ m reaches splitting ratio ER in the bandwidth range of 54nm _A＜-20dB.At wavelength X=1.54 μ m, ER _B=-35.73558dB, wavelength coverage reaches the interior splitting ratio ER of bandwidth range of 60nm from λ=1.515 μ m～1.575 μ m _B＜-20dB, wherein wavelength coverage reaches splitting ratio ER in the bandwidth range of 31nm from λ=1.527 μ m～1.558 μ m _B＜-30dB.The polarization cross-talk shown in Fig. 9 (b), when λ=1.55 μ m, CT _x=35.74485dB; At wavelength X=1.54 μ m, CT _y=27.925668dB.

The foregoing description shows the coupled characteristic that utilizes mixed light-guiding double-core photonic crystal fiber novelty of the present invention, the polarization beam apparatus of making, its length is 5.2mm, splitting ratio is to the maximum-35.73558dB, have good beam splitting effect, and have big splitting ratio broadband effects.

Claims

1. the oval double-core photonic crystal fiber of mixed light-guiding comprises high index of refraction post (1), spilehole (2), background material (3), gross blow hole (4), fibre core A (5), fibre core B (6); It is characterized in that: two edge x direction of principal axis at optical fiber kernel of section point equidistantly distribute some and high index of refraction post (1) the fiber optic hub line parallel, the effective refractive index n of high index of refraction post (1) ₂Be 1.59～1.65, respectively remove two high index of refraction posts (1) on the both sides of central point and form two oval fibre cores, be fibre core A (5) and fibre core B (6), the pore covering is made of 4 gross blow holes (4) and some spileholes (2), spacing Λ between all pore spacings and the high index of refraction post (1) is 3.0 μ m～4.0 μ m, the diameter d of gross blow hole (4) ₁Be 2.0 μ m～3.0 μ m, the diameter d of spilehole (2) is 2.0 μ m～2.5 μ m, and 4 gross blow holes (4) are distributed in fibre core A (5) and fibre core B (6) on every side, the effective refractive index n of spilehole (2) and gross blow hole (4) _AirBe 1, background material 3 is silex glass material or polymer material, its effective refractive index n _sBe 1.45.