CN100386656C - Pyrometric cone type polarization maintaining optical fiber device and wide-band polarization maintaining optical fiber shunt - Google Patents

Abstract

The present invention discloses the characteristics of a class of fusible cone type polarization maintaining optical fiber devices. The ratio of the short axis and the long axis of the cross section of the coupling region of the class of devices is between one to point nine-five and one to one point four. The device has high polarization isolation, and simultaneously improves the reliability of the device a lot. The operating temperature range of the device is enlarged from negative forty DEG to positive eighty-five DEG. The present invention also discloses a wideband polarization maintaining optical fiber splitter which comprises the fusible cone type polarization maintaining optical fiber devices.

Description

Melting cone type polarization maintaining optical fibre device and broadband polarization maintaining optical fibre shunt

Technical field

The present invention relates to a class melting cone type polarization maintaining optical fibre device; The invention still further relates to a kind of broadband polarization maintaining optical fibre shunt.

Background technology

Polarization maintaining optical fibre has a region of high stress radially, is radially forming asymmetricly like this, makes this type optical fiber have the ability that polarization keeps.Therefore, the orientation in this high-attraction district and symmetry will have a strong impact on the characteristic of polarization maintaining optical fibre.When making device with polarization maintaining optical fibre; at first peel two polarization maintaining optical fibres off protective seam in the molten zone of drawing of needs; and by shown in Figure 1; need to guarantee molten zone of drawing parallel tangent; its xsect as shown in Figure 2; therefore before not having molten drawing, the ratio of minor axis of xsect (a) and major axis (b) is 1: 2.But when carrying out fused biconical taper, in general, control to device coupled zone shape of cross section has special requirement, make every effort to not destroy the distribution in the high-attraction district of original fiber, make the unaffected or influence of the linear polarization polarisation of light isolation that passes through the coupled zone of transmission seldom, consider that polarization has less accessory loss that is caused by the optical fiber coupling or acceptable than lower added loss in the coupled zone simultaneously again.Only in this way, the light of propagating in an optical fiber is coupled into another root optical fiber with just understanding low-loss.

A lot of scholars in this field have carried out research over a long time.The minor axis (a) of U.S. Pat 5420949 disclosed device xsects and the ratio of major axis (b) are between 1: 1.85 to 1: 1.95, and as shown in Figure 3, the cross section of device obviously is " dumbbell shape ".Press minor axis (a) and the such proportionate relationship of major axis (b), mutual melting degree also between the polarization maintaining optical fibre: not really strong, and owing to adopt the heating source of relatively lower temp to draw awl mostly, thereby generally be not to melt together veritably between two polarization maintaining optical fibres of coupled zone, but because heating and stretching just make two optical fiber stick together.Therefore above-mentioned device has following several characteristics, and first by just sticking together between optical fiber, so be not a firm structure from structure; Second because before not drawing awl, distance between core and the core is distant, that realizes certain splitting ratio draws awl length long, the degree of light field expansion is bigger in the coupled zone, air and fibre cladding have formed an effective waveguide interface, therefore, in case outside environment changes (as water inlet), the optical property of device changes at once, i.e. variation to external world is quite responsive; The 3rd because the device cross sectional shape is " dumbbell shape ", by encapsulating material may cause to reverse gravitation bigger, thereby also have influence on other optical property of device; The 4th is owing to adopt low temperature directly to draw awl technology, may exist microfracture not improve at former optical fiber surface, the molten physical strength in district of drawing is reduced, and. make aqueous vapor very fast by the speed that these microfractures are penetrated into the coupled zone, thereby the life-span that finally causes device: shorten " Long term splitting ratio drifts in Singlemode fused fiber opticsplitters " that people such as IC.V.Cry deliver greatly, pp746-757, NFOEC conference, June 18-22,1995, Boston, MA].In a word, though this class device polarization isolation the most at the beginning may be higher, stability in time is relatively poor relatively, and working temperature is usually only in 0 ℃ to+70 ℃ scope.Therefore, the long-term reliability of device is subjected to bigger influence.

In addition, U.S. Pat 4798436 discloses common shunt and can produce the shunt with wide wavelength characteristic by the technology that " prestretching " reaches " knotting ".And for the polarization maintaining optical fibre shunt, because polarization maintaining optical fibre necessary parallel placement in the coupled zone before molten drawing, so can not " prestretching " can not " tie a knot " again, so just be difficult to realize the characteristic of wide wavelength work by the technology of routine.

Summary of the invention

One of purpose of the present invention is the above-mentioned deficiency at prior art, proposes a kind of polarization isolation height, operating temperature range is big, long-term reliability is good melting cone type polarization maintaining optical fibre device.

Two of purpose of the present invention is to propose a kind of broadband polarization maintaining optical fibre shunt with wide wavelength characteristic.

One of to achieve these goals, the melting cone type polarization maintaining optical fibre device that the present invention proposes, the ratio of its coupled zone xsect minor axis and major axis are between 1: 0.95 to 1: 1.4, and the stress area of coupled zone xsect is oval.

Above-mentioned molten silver-colored type polarization maintaining optical fibre device coupled zone preferably comprises the optical fiber more than two or two, and wherein at least one is polarization maintaining optical fibre; Most preferably three optical fiber are polarization maintaining optical fibre.

This device has following several characteristics, and the firstth, owing to draw awl district's optical fiber to be merged fully, formed a twin-core fiber, so be a very firm structure from structure; Second because before not drawing awl, distance between core and the core is very close, that realizes certain splitting ratio draws awl length shorter relatively, the degree of light field expansion is smaller in the coupled zone, and coupling is concentrated and occurred in core district central authorities, and air and fibre cladding also do not form an effective waveguide interface, therefore, in case outside environment changes (as water inlet), the optical property of device is almost constant, and promptly variation to external world is quite insensitive; The 3rd because the device cross sectional shape almost is " round ", by encapsulating material may cause to reverse gravitation just very little, thereby minimum to other optical property influence of device; The 4th is owing to adopt high temperature to melt earlier, low temperature draws the technology of awl, may exist microfracture to improve at former optical fiber surface also may remove, the molten physical strength in district of drawing is increased, and the speed that makes aqueous vapor penetrate into the coupled zone slows down greatly, thereby makes the anti-aqueous vapor ability of device strengthen greatly.In a word, this class device is except that having higher polarization isolation, and device stability in time is than higher, and working temperature also expands in-40 ℃ to+80 ℃ scopes.Therefore, the long-term reliability of device is greatly improved.

Above-mentioned melting cone type polarization maintaining optical fibre device does not have special feature on making.With two optical fiber; wherein at least one is polarization maintaining optical fibre; according to arranging as shown in Figure 1; wherein L ' is the length that optical fiber is peeled off protective seam; its length does not generally wait at 10 to 70 millimeters; and L guarantees two optical fiber tangent length mutually; its length is generally between 8 millimeters to 65 millimeters; and utilize heating-up temperature near or the oxyhydrogen flame that equals the optical fiber fusing point heat this zone; make the ratio of the minor axis of its xsect and major axis 1: 0.95 to 1: 1.4 between generally between several seconds to a few minutes heat time heating time.And to multifiber, for example make by the molten device that pulls into of three polarization maintaining optical fibres, wherein be the situation of a polarization maintaining optical fibre at least, its preparation and technological process are identical.

In order to realize two of foregoing invention purpose, the broadband polarization maintaining optical fibre shunt that the present invention proposes comprises the melting cone type polarization maintaining optical fibre device that above-mentioned three optical fiber are polarization maintaining optical fibre.

With respect to prior art, the present invention is fused together two polarization maintaining optical fibres fully, and making the minor axis (a) of device xsect and the ratio of major axis (b) is between 1: 0.95 to 1: 1.4, and the xsect that makes original two optical fiber is the spitting image of a twin-core polarization maintaining optical fibre.The stress area of device of the present invention coupled zone xsect is oval, is guaranteeing that device has higher polarization and isolates, and the reliability of device improves a lot simultaneously.Particularly make its operating temperature range be extended to-40 ℃ to+85 ℃.The broadband polarization maintaining optical fibre shunt that adopts technical scheme of the present invention to make, its added losses generally about 0.2dB, bandwidth of operation can reach+/-40nm, maximum beam split ratio less than+/-2%, and polarization extinction ratio all keeps greater than more than the 18dB in bandwidth.

Description of drawings

Fig. 1 is 1X2 or the vertical synoptic diagram of 2X2 polarization maintaining optical fibre device before molten drawing in the prior art.

Fig. 2 is 1X2 or the cross sectional representation of 2X2 polarization maintaining optical fibre device before molten drawing in the prior art, is illustrated as panda type polarization-preserving fiber.

Fig. 3 is the cross sectional representation of 1X2 or 2X2 polarization maintaining optical fibre device coupled zone in the prior art.

Fig. 4 is that 1X2 of the present invention or 2X2 polarization maintaining optical fibre device use technology of the present invention to draw the cross sectional representation of coupled zone, awl back.

Fig. 5 is 1X3 of the present invention, 2X3, the vertical synoptic diagram of 3X3 polarization maintaining optical fibre device before fused biconical taper.

Fig. 6 is 1X3 of the present invention, and 2X3,3X3 polarization maintaining optical fibre device draw the cross sectional representation of coupled zone, awl back with technology of the present invention.

Fig. 7 is 1X2 of the present invention, 50: 50 broadband polarization maintaining optical fibre shunt basic structure synoptic diagram.

Fig. 8 is 1X2 of the present invention, 50: 50 broadband polarization maintaining optical fibre shunt polarization spectrum bandwidth characteristic figure.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in further detail.

Embodiment 1

With two optical fiber; wherein at least one is polarization maintaining optical fibre; be ready to by arrangement shown in Figure 1; wherein L ' is the length that optical fiber is peeled off protective seam; its length does not generally wait at 10 to 70 millimeters; and L guarantees two optical fiber tangent length mutually; its length is generally between 8 millimeters to 65 millimeters; and utilize heating-up temperature near or the oxyhydrogen flame that equals the optical fiber melting point heat this zone; heat time heating time is generally between several seconds to a few minutes; make the ratio of the minor axis (a) of its xsect and major axis (b) between 1: 0.95 to 1: 1.4; the stress area of coupled zone xsect is oval, and the xsect that makes original two optical fiber is the spitting image of a twin-core polarization maintaining optical fibre (as shown in Figure 4).

This device has higher polarization isolates, and reliability improves a lot simultaneously.Particularly make its operating temperature range be extended to-40 ℃ to+85 ℃.

Embodiment 2

Making is by the molten device that pulls into of three polarization maintaining optical fibres, at first three optical fiber located by mode as shown in Figure 5, and draws according to embodiment 1 described technology is molten, makes the xsect of original three optical fiber resemble very much one three core polarization maintaining optical fibre (as shown in Figure 6) equally.

Embodiment 3

Three polarization maintaining optical fibres are by arranging the device that melting and pulling becomes as shown in Figure 3, and when linearly polarized light during from the slow axis input of port 2, so at output port 4,5, the Output optical power of 6 (see figure 5)s satisfies

$P_{5S}\left(\mathrm{\λ}\right)={\cos }^2(\sqrt{2}\·\underset{0}{\overset{L}{\∫}}{C}_S\left(\mathrm{\λ}\right)\mathrm{dz})$

$P_{4S}\left(\mathrm{\λ}\right)=P_{6S}\left(\mathrm{\λ}\right)=\frac{1}{2}{\sin }^2(\sqrt{2}\·\underset{0}{\overset{L}{\∫}}{C}_S\left(\mathrm{\λ}\right)\mathrm{dz})$

Wherein Cs (λ) is linearly polarized light coupling coefficient between adjacent fiber on slow axis the time, and L is effective coupling length of coupled zone.The broadband splitter that can produce polarization maintaining optical fibre equally according to document " ' 1x3 Linear Array Singlemode PibreCouplers ', Electronics Letters, V01.28, No.25,1992, pp2330-2332. ".Suitable equally when being positioned on the fast axle as linear polarization optical fiber here.

On manufacture craft, by as Fig. 6 that fiber orientation is good, the slow axis of polarization maintaining optical fibre is perpendicular to the plane of three optical fiber formations earlier, and the center section of three optical fiber all has one section naked fine part of peelling off coat, the middle body of this naked fine part is closely close, form a parallel zone.With wavelength is λ ₀Linearly polarized light inject (can be positioned on slow axis or fast axle is gone up s) from port 2, output port 4,5,6 insert photo-detector, monitor the output power of each output port in real time, use three polarization maintaining optical fibres of high temperature heating source fusion presumptive area then, crossfade into Fig. 5 until its xsect from Fig. 4, at last with the heating source melting zone that stretches, reach minimum until the output power of port 5, almost can reach zero usually.Cut away port one then, 3 and 5, form the broadband splitter (as shown in Figure 7) that an appearance looks like a 1X2.

This broadband splitter polarization spectrum bandwidth characteristic as shown in Figure 8.

Claims (3)

1. melting cone type polarization maintaining optical fibre device, it is characterized in that: the coupled zone comprises the optical fiber more than two or two, wherein at least one is polarization maintaining optical fibre, and the ratio of coupled zone xsect minor axis and major axis is between 1: 0.95 to 1: 1.4, and the stress area of coupled zone xsect is oval.

2. melting cone type polarization maintaining optical fibre device according to claim 1 is characterized in that the coupled zone comprises three optical fiber and three optical fiber are polarization maintaining optical fibre.

3. a broadband polarization maintaining optical fibre shunt is characterized in that comprising the described melting cone type polarization maintaining optical fibre of claim 2 device.

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