CN105259612A - Low-loss coupling method of photonic crystal fiber and common single-mode fiber - Google Patents

Abstract

Disclosed in the invention is a low-loss coupling method of a photonic crystal fiber and a common single-mode fiber. The coupling method comprises the following steps: (1), determining a tapering parameter and carrying out counter tapering on a photonic crystal fiber; and (2), after counter tapering of the photonic crystal fiber, coupling or connecting a common single-mode fiber and the photonic crystal fiber. According to the invention, the low-loss coupling method is suitable for low-loss coupling between various photonic crystal fibers and common single-mode fibers; and a good effect can be realized under the circumstances that mode fields of the photonic crystal fibers and common single-mode fibers do not match perfectly.

Description

A kind of photonic crystal fiber and general single mode fiber low-loss coupling process

Technical field

The present invention relates to fiber-optic coupling method field, specifically a kind of photonic crystal fiber and general single mode fiber low-loss coupling process.

Background technology

Photonic crystal fiber (PCF, PhotonicCrystalFiber), be also called porous optical fiber (HF) or microstructured optical fibers (MOF), it has the airport structure of periodic arrangement, and flexible structure is variable.Compared with traditional fiber, it has dispersion-tunable, and nonlinear characteristic is adjustable, can realize the advantages such as endless single mode characteristic, may be used for the fields such as super continuous spectrums generation, optical soliton communication, has become the focus of research.The low loss welding technology of photonic crystal fiber and general single mode fiber is the key technical problem that photonic crystal fiber moves towards practical.Therefore, the low loss welding how realizing photonic crystal fiber and general single mode fiber becomes one of study hotspot in recent years.

1999, the first time welding such as Bennett PCF and general single mode fiber (SMF), Chinese scholars proposed the multiple welding process about two type optical fibers thereafter, as PCF airport is collapsed, adds transition optical fiber, draws cone etc. to PCF.These methods all also exist certain defect, as PCF collapses airport method, compare the degree of collapsing being difficult to accurately control airport; Add transition optical fiber, generally can introduce the coupling of more than twice, cause total splice loss, splice attenuation higher; Cone is drawn to PCF, then easily destroys the structure of PCF.

Summary of the invention

The object of this invention is to provide a kind of photonic crystal fiber and general single mode fiber low-loss coupling process, to solve prior art photonic crystal fiber and the larger problem of general single mode fiber coupling loss.

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

Photonic crystal fiber and general single mode fiber low-loss coupling process, is characterized in that: comprise the following steps:

(1), first determine to draw cone ratio A;

(2), set the photonic crystal fiber diameter before drawing cone as D ₀, draw the photonic crystal fiber external diameter after cone to be D ₁, then have:

$A=\frac{D_1}{D_0},$

Wherein draw the photonic crystal fiber diameter D before cone ₀for known parameter, after A determines, just can calculate the photonic crystal fiber outer diameter D after drawing cone ₁=D ₀* A, draws the length L of cone can free setting;

(3) according to step (2) parameters obtained, reverse drawing cone is carried out to photonic crystal fiber;

(4), after reverse drawing cone being carried out to photonic crystal fiber, general single mode fiber is coupled with photonic crystal fiber or is connected.

Described photonic crystal fiber and general single mode fiber low-loss coupling process, is characterized in that: in step (1), can according to but be not limited to the mode field diameter MFD of PCF _pCFwith the mode field diameter MFD of SMF _sMFdetermine A:

$A=\frac{{\mathrm{MFD}}_{SMF}}{{\mathrm{MFD}}_{PCF}}.$

Advantage of the present invention is:

(1) fiber-optic coupling method of the present invention, has good versatility, is applicable to the coupling between the general single mode fiber of plurality of specifications and photonic crystal fiber.

(2) when general single mode fiber and photonic crystal fiber mould field severe mismatch, good coupling effect can be obtained.

(3) step of the present invention is simple, and optical coupling efficiency is high.

Accompanying drawing explanation

Fig. 1 is photonic crystal fiber positive view in the present invention.

Fig. 2 is that the present invention draws cone parameter declaration figure.

Fig. 3 is the realistic model schematic diagram that the present invention sets up.

Embodiment

Photonic crystal fiber and general single mode fiber low-loss coupling process, comprise the following steps:

(1), first determine to draw cone ratio A;

(2), as shown in Figure 2, if draw the photonic crystal fiber diameter before cone to be D ₀, draw the photonic crystal fiber external diameter after cone to be D ₁, then have:

$A=\frac{D_1}{D_0},$

Wherein draw the photonic crystal fiber diameter D before cone ₀for known parameter, after A determines, just can calculate the photonic crystal fiber outer diameter D after drawing cone ₁=D ₀* A, draws the length L of cone can free setting;

(3) according to step (2) parameters obtained, reverse drawing cone is carried out to photonic crystal fiber;

(4), after reverse drawing cone being carried out to photonic crystal fiber, general single mode fiber is coupled with photonic crystal fiber or is connected.

As shown in Figure 3, in step (1), can according to but be not limited to the mode field diameter MFD of PCF _pCFwith the mode field diameter MFD of SMF _sMFdetermine A:

$A=\frac{{\mathrm{MFD}}_{SMF}}{{\mathrm{MFD}}_{PCF}}.$

Specific embodiment:

Choose PCF as shown in Figure 1, its parameter is: cladding diameter D is 125 μm, and airport diameter d is 1.8 μm, and airport spacing is 2.5 μm, and mode field diameter MFD is 2.4 μm.Single-mode fiber is SMF-28, and mode field diameter is 10.4 μm.Because two kinds of fibre-optic mode field diameter differences are comparatively large, cause two kinds of coupling fiber losses larger.If only consider the loss that model field unbalance causes, the coupling loss theoretical value of two kinds of optical fiber is 7.17dB.The computing formula of the coupling loss α caused by model field unbalance is as follows, wherein ω _pCFand ω _sMFrepresent the spot size of PCF and SMF respectively:

$\mathrm{\α}=-10\lg \[{\left(\frac{2{\mathrm{\ω}}_{PCF}{\mathrm{\ω}}_{SMF}}{{\mathrm{\ω}}_{PCF}^2+{\mathrm{\ω}}_{SMF}^2}\right)}^2\].$

The present invention is a kind of method that photonic crystal fiber is coupled with general single mode fiber, and step is as follows:

(1) A is determined, MFD according to the mode field diameter (MFD, modefielddiameters) of PCF and SMF _sMF=10.4 μm, MFD _pCF=2.4 μm:

$A=\frac{{\mathrm{MFD}}_{SMF}}{{\mathrm{MFD}}_{PCF}}\≈4.3$

D ₀＝125μm，D ₁＝D ₀*A＝541.67μm。Choose L=2000 μm.

(2) according to (1) parameters obtained, reverse drawing cone is carried out to photonic crystal fiber.

(3), after reverse drawing cone being carried out to photonic crystal fiber, general single mode fiber is coupled with photonic crystal fiber or is connected.

After adopting above coupling process, PCF and SMF-28 coupling loss is 0.21dB, considerably reduces the coupling loss of two kinds of optical fiber.

Claims (2)

1. photonic crystal fiber and general single mode fiber low-loss coupling process, is characterized in that: comprise the following steps:

(1), first determine to draw cone ratio A;

(2), set the photonic crystal fiber diameter before drawing cone as D ₀, draw the photonic crystal fiber external diameter after cone to be D ₁, then have:

$A=\frac{D_1}{D_0},$

Wherein draw the photonic crystal fiber diameter D before cone ₀for known parameter, after A determines, just can calculate the photonic crystal fiber outer diameter D after drawing cone ₁=D ₀* A, draws the length L of cone can free setting;

(3) according to step (2) parameters obtained, reverse drawing cone is carried out to photonic crystal fiber;

(4), after reverse drawing cone being carried out to photonic crystal fiber, general single mode fiber is coupled with photonic crystal fiber or is connected.

2. photonic crystal fiber according to claim 1 and general single mode fiber low-loss coupling process, is characterized in that: in step (1), can according to but be not limited to the mode field diameter MFD of PCF _pCFwith the mode field diameter MFD of SMF _sMFdetermine A:

$A=\frac{{\mathrm{MFD}}_{SMF}}{{\mathrm{MFD}}_{PCF}}.$