CN104216043A - Photonic crystal fiber polarization splitter - Google Patents

Abstract

The invention discloses a polarization splitter based on dual-core photonic crystal fibers. Dual-core photonic crystal fibers of the splitter comprise quartz background material and round and elliptical air holes and are arranged in a hybrid structure of a right-angled lattice, a rectangular lattice and a right-angled lattice; a dual-core is composed of elliptical holes and round air holes around the elliptical holes; a long axis (short axis) of the central elliptical air hole is perpendicular to long axes (short axes) of the elliptical air holes on two sides. Such structure enables birefraction effect of the dual-core photonic crystal fibers to be more intense, separation of X and Y polarized beams is favored, and the performance of the splitter is improved. The splitter has the advantages that the features such as small length, high extinction ratio and large bandwidth are achieved in a balanced manner, and important theoretical guidance is provided for miniaturization, ultrahigh-capacity and ultrahigh-bandwidth development of an optical communication system.

Description

Photonic crystal fiber polarization beam apparatus

Technical field

The present invention relates to polarization beam apparatus field, specifically a kind of polarization beam apparatus based on double-core photonic crystal fiber.

Background technology

Polarization beam apparatus is the device two of light beam orthogonal polarization modes being carried out being separated, and is widely used in the communication systems such as optical communication, light sensing and Photoelectric Detection.At present, optical communication system just towards vast capacity and microminiaturized future development, and can not meet these demands for development based on the polarization beam apparatus of traditional fiber.In recent years, the photonic crystal fiber (PCF) with superior optical characteristics causes the great attention of people, and structure provides new method for design double-core photonic crystal fiber flexibly, also provides new approach for developing high-performance polarization beam apparatus.Such as, document " Polarization splitter based on photonic crystal fibers " reports the double-core photonic crystal fiber polarization beam apparatus that a kind of length is 1.7mm, bandwidth of operation is 40nm, and performance is obviously better than conventional polarization beam splitter.Thereafter, there is again the photonic crystal fiber polarization beam apparatus of other structures, document " Polarization splitter in three-core photonic crystal fibers " reports a kind of three core photonic crystal fiber polarization beam apparatus, and is studied its performance; Document " A novel approach for designing photonic crystal fiber splitters with polarization independent propagation characteristics " proposes the double-core photonic crystal fiber polarization beam apparatus of full oval structure; Document " Polarization splitter based on a square-lattice photonic crystal fiber " devises the double-core photonic crystal fiber polarization beam apparatus that length is 20mm, bandwidth is 90nm square lattice structure; Document " A novel polarization splitter based on dual-core hybrid photonic crystal fibers " and document " Ultrabroadband polarization splitter based on three-core photonic crystal fibers " then pass through the method design of covering or fibre core doping mixing twin-core PCF polarization beam apparatus.But above-mentioned polarization beam apparatus or length long, or bandwidth range is narrower, poor-performing.

Summary of the invention

The object of this invention is to provide a kind of double-core photonic crystal fiber polarization beam apparatus, to improve the performance of existing fiber polarization beam apparatus.

In order to achieve the above object, the technical solution adopted in the present invention is:

A kind of photonic crystal fiber polarization beam apparatus, it is characterized in that: the double-core photonic crystal fiber forming polarization beam apparatus adopts the structure of equilateral triangle lattice-rectangle lattice-equilateral triangle lattice airport mixing arrangement, this construction comprise circular airport and oval airport are formed, the diameter of all circular airports is D, and the airport spacing of equilateral triangle arrangement is Λ ₁, airport level and the vertical spacing of rectangular configuration arrangement are respectively Λ ₂and Λ ₃, wherein Λ ₁=Λ ₂, the twin-core of photonic crystal fiber and fibre core A and fibre core B are made up of oval airport and round airport around thereof.

The oval airport in both sides is symmetrical about the minor axis of the oval airport in center, and the major axis of the major axis of the oval airport in center or minor axis and its both sides ellipse airport or minor axis vertical, the long diameter D being d, d and numerically equaling circular airport of all oval airport minor axises, major axis is long is respectively d ₁, d ₂and d ₃, the center distance of the oval airport in both sides is 4 Λ ₂.

The present invention devises a kind of high-performance double-core photonic crystal fiber polarization beam apparatus, at D=d=1 μm, Λ ₁=Λ ₂=1.1 μm, Λ ₃=1.7 μm, η ₁=d ₁/ d=1.4, η ₂=d ₃under/d=1.7 structural parameters, polarization beam apparatus has extremely short length (119.1 μm) and high extinction ratio (118.7dB), the bandwidth that simultaneously extinction ratio is greater than 20dB reaches 180nm (1453nm-1633nm), can cover S+C+L communication band completely.The characteristic of the short length of polarization beam apparatus balanced realization of the present invention, high delustring, broader bandwidth, the development of, vast capacity microminiaturized to optical communication system and ultra high bandwidth has important theory directive significance.

Accompanying drawing explanation

Fig. 1 is the single core structure radial cross-section of the present invention.

Fig. 2 is 1.55 mum wavelength place η in the present invention ₁schematic diagram is affected on CL and CLR.

Fig. 3 is 1.55 mum wavelength place η in the present invention ₂schematic diagram is affected on CL and CLR.

Fig. 4 is 1.55 mum wavelength place Λ in the present invention ₁schematic diagram is affected on CL and CLR.

Fig. 5 is 1.55 mum wavelength place Λ in the present invention ₃schematic diagram is affected on CL and CLR.

Fig. 6 is specific embodiment of the invention D=d=1 μm, Λ ₁=Λ ₂=1.1 μm, Λ ₃=1.7 μm, η ₁=d ₁/ d=1.4, η ₂=d ₃under/d=1.7 condition, coupling length is with the variation relation figure of wavelength.

Fig. 7 is specific embodiment of the invention D=d=1 μm, Λ ₁=Λ ₂=1.1 μm, Λ ₃=1.7 μm, η ₁=d ₁/ d=1.4, η ₂=d ₃under/d=1.7 condition, in fibre core A, normalized power is with the variation relation figure of transmission range.

Fig. 8 is specific embodiment of the invention D=d=1 μm, Λ ₁=Λ ₂=1.1 μm, Λ ₃=1.7 μm, η ₁=d ₁/ d=1.4, η ₂=d ₃under/d=1.7 condition, extinction ratio is with wavelength variations graph of a relation.

Embodiment

As shown in Figure 1, a kind of double-core photonic crystal fiber polarization beam apparatus, include two fibre cores of pure quartzy background 1, the double-core photonic crystal fiber forming polarization beam apparatus adopts the structure of equilateral triangle lattice 1-rectangle lattice 2-equilateral triangle lattice 3 airport mixing arrangement, this construction comprise circular airport and oval airport are formed, the diameter of wherein all circular airports 5 is D, and the airport spacing of equilateral triangle arrangement is Λ ₁, airport level and the vertical spacing of rectangular configuration arrangement are respectively Λ ₂and Λ ₃, the twin-core (i.e. fibre core A and fibre core B) of photonic crystal fiber is made up of its oval airport (6,7 and 8) and round airport around thereof.In addition, oval airport 6 is positioned at the geometric center of this structure, the major axis (minor axis) of oval airport 6 is vertical with the major axis (minor axis) of 8 with oval airport 7, oval airport 7 and oval airport 8 symmetrical about the minor axis of oval airport 6, and the minor axis of oval airport 6,7 and 8 length is d (numerically equaling the diameter D of circular airport), major axis is long is respectively d ₁, d ₂and d ₃, oval airport 7 and 8 center distance is 4 Λ ₂.This structure makes double-core photonic crystal fiber birefringence effect more strong, is conducive to X with Y polarized light and is separated, improve beam splitter performance.Getting airport refractive index is 1, and the refractive index of quartz is obtained by document " Interspecimen Comparison of the Refractive Index of Fused Silica ".

In a specific embodiment, get D=d=1 μm, Λ ₁=Λ ₂=1.1 μm, Λ ₃=1.7 μm, η ₁=d ₁/ d=1.4, η ₂=d ₃the performance of/d=1.7 to photonic crystal fiber beam splitter of the present invention calculates.

Fig. 2-Fig. 6 by X, Y polarization direction coupling length formula (formula 1 and formula 2) and definition coupling length formula (formula 3) obtain:

1, the coupling length formula of X, Y polarization direction

$L_x=\frac{\mathrm{\π}}{{\mathrm{\β}}_x^e-{\mathrm{\β}}_x^o}=\frac{\mathrm{\λ}}{2(n_x^e-n_x^o)}$ (formula 1)

$L_y=\frac{\mathrm{\π}}{{\mathrm{\β}}_y^e-{\mathrm{\β}}_y^o}=\frac{\mathrm{\λ}}{2(n_y^e-n_y^o)}$ (formula 2)

2, coupling length formula is defined

$\mathrm{CLR}=\frac{L_y}{L_x}=\frac{m}{n}$ (formula 3)

Fig. 7 is obtained by the normalized power formula (formula 4 and formula 5) of X, Y polarized light:

${\mathrm{NP}}_x=\frac{P_{x-\mathrm{out}}}{P_{\mathrm{in}}}={\cos }^2\left(\frac{\mathrm{\πL}}{2L_x}\right)$ (formula 4)

${\mathrm{NP}}_y=\frac{P_{y-\mathrm{out}}}{P_{\mathrm{in}}}={\cos }^2\left(\frac{\mathrm{\πL}}{2L_y}\right)$ (formula 5)

Fig. 8 is obtained by extinction ratio (Extinction Ratio, the ER) formula (formula 6) in fibre core A:

$\mathrm{ER}=10{\log }_{10}\left(\frac{P_{x-\mathrm{out}}}{P_{y-\mathrm{out}}}\right)$ (formula 6)

The foregoing is only one embodiment of the present invention, it not whole or unique embodiment, the conversion of those of ordinary skill in the art by reading instructions of the present invention to any equivalence that technical solution of the present invention is taked, is claim of the present invention and contains.

Claims (2)

1. a photonic crystal fiber polarization beam apparatus, it is characterized in that: the double-core photonic crystal fiber forming polarization beam apparatus adopts the structure of equilateral triangle lattice-rectangle lattice-equilateral triangle lattice airport mixing arrangement, this construction comprise circular airport and oval airport are formed, the diameter of all circular airports is D, and the airport spacing of equilateral triangle arrangement is Λ ₁, airport level and the vertical spacing of rectangular configuration arrangement are respectively Λ ₂and Λ ₃, wherein Λ ₁=Λ ₂, the twin-core of photonic crystal fiber and fibre core A and fibre core B are made up of oval airport and round airport around thereof.

2. photonic crystal fiber polarization beam apparatus according to claim 1, it is characterized in that: the oval airport in both sides is symmetrical about the minor axis of the oval airport in center, and the major axis of the major axis of the oval airport in center or minor axis and its both sides ellipse airport or minor axis vertical, all oval airport minor axises are long is d, d numerically equals the diameter D of circular airport, and major axis is long is respectively d ₁, d ₂and d ₃, the center distance of the oval airport in both sides is 4 Λ ₂.