CN1317098A

CN1317098A - Radially nonuniform and azimuthally asymmetric optical fiber

Info

Publication number: CN1317098A
Application number: CN99810742A
Authority: CN
Inventors: V·A·巴加万吐拉; R·M·霍克
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 1998-09-09
Filing date: 1999-08-20
Publication date: 2001-10-10
Also published as: JP2002524766A; WO2000014581A2; TW455710B; EP1125153A2; KR20010085768A; AU5680599A; ZA995769B; ZA200100472B; BR9913124A; ID28479A; CA2342339A1; WO2000014581A3

Abstract

A single-mode waveguide fiber and a method for manufacturing single-mode or multimode waveguide fibers are disclosed, wherein the waveguide fiber has a core with azimuth and radial asymmetry. This asymmetry provides additional degrees of freedom for forming waveguides with specific properties.

Description

The asymmetric optical fiber of radially nonuniform and azimuthally

Background of invention

The present invention is based on the U.S. Provisional Application of submitting on September 9th, 1,998 60/099,535.We require the priority date of this application.

The present invention relates to a kind of optical fiber and a kind of methods for optical fiber manufacture, the refractive index distribution curve of described optical fiber radially with the position angle two changes of direction.The additional adaptability of giving along azimuthal variation provides such refractive index distribution curve design, promptly with refractive index only radially coordinate direction situation about changing compare, these designs can be satisfied more waveguide fiber performance requirement.

The waveguide fiber that the index distribution of recent development radially changes footpath demonstrates, and can optimize guide properties by regulating this distribution curve.For example with the simple step mode of a kind of ratio more generally mode change refractive index distribution curve, this change allows to select the value of one or more guide properties under the situation of not sacrificing one group of basic characteristic (decay, intensity or bending resistance).

In addition, the asymmetric fiber core refractive index distribution in some position angle (having the distribution of ellipse, triangle or square fibre core geometric configuration such as those) demonstrates, and they can provide the waveguide performance of usefulness, such as keeping or mixed polarized pattern.

Therefore, expectation along the position angle and radially the fiber core refractive index distribution curve of two changes of direction can offer an opportunity make be suitable in telecommunications, signal Processing or sensing system, using, have new or through the waveguide of improvement performance.

In the United States Patent (USP) 3,909,110 of authorizing Marcuse (being called for short ' 110 patents), a kind of multimode waveguide has been described, its fibre core relative bearing is asymmetric.Calculating in ' 110 patents shows, refractive index radially produces Mode Coupling with the cyclical variation meeting of position angle both direction, thereby increases the loss because of being coupled and producing with radial mode of bandwidth, restriction simultaneously.This notion does not extend to single mode waveguide.The scope of patent is also only limited to sinusoidal azimuthal variation in addition, ' 110.

Describe present position angle and radially during asymmetric fibre core, introducing the notion of fibre core sector.A fibre core sector is the part of fibre core, and it is limited by the track that forms first and second radius point of annulus in the waveguide.Two radiuses differ from one another, and are less than or equal to fiber core radius.The residue border of sector is at angle two planes each other, and each plane all comprises the center line of waveguide fiber.Refractive index is meant to have the refractive index difference of two points on this straight line at least along the variation of a straight line in the sector.

Definition

Below definition meets the conventional usage of this area.

-segmented core is a kind of fibre core that has specific refractive index in the layering of preliminary election radius.A particular hierarchical has the first refractive index point and last refractive index point.Radius from the waveguide core line to the first refractive index point position is the inside radius of core region or fibre core layering.Equally, from the waveguide core line to the end the radius of refractive index point position be the external radius of fibre core layering.

-relative index of refraction Δ, it is defined by following formula: Δ=(n ₁ ²-n ₂ ²)/2n ₁ ², wherein, n ₁Be the largest refractive index of refractive index layering 1, and n ₂Be with reference to refractive index, in this application, it is the minimum refractive index of covering.Term " Δ % " is used in this area, and it is 100 * Δ.

-term " refractive index distribution curve " is meant, in the relation between Δ % or refractive index and the radius on the fibre core one selected part.Term " α distribution curve " is meant, satisfies the refractive index distribution curve of following equation:

n(r)=n ₀(1-Δ[r/a] ^α)，

Wherein r is a fiber core radius, the definition of Δ as above, a is the last point of distribution curve, r locates to be chosen as zero first of distribution curve, and α is the index that limits profile shape.Other refractive index distribution curve comprises the step change type refractive index of step change type refractive index, trapezoidal refractive index and band fillet, wherein generally causes owing to alloy spreads in the fast-changing zone of refractive index with fillet.

Summary of the invention

In a first aspect of the present invention, the fibre core of single mode waveguide has a sector at least.In the sector outside more at least refractive index and the sector more at least refractive index different.When the sector just in time is half fibre core, can selects to constitute in the sector part of any arbitrarily, and not lose the accuracy of distribution curve definition.The fiber core refractive index distribution curve changes along at least a portion of a radius, produces radially asymmetric.On the radius of a preliminary election, the fiber core refractive index in the sector is different with the fiber core refractive index outside the sector, thereby provides the position angle asymmetric.

In one embodiment, whole fibre core is a cylinder symmetric, and therefore radius r, position angle φ and the center line height z of being convenient to cylindrical coordinates describes.The preliminary election radius part Δ r that refractive index changes is at 0＜Δ r≤r ₀Scope in, r wherein ₀It is fiber core radius.At least be that different preliminary election radius is in this same scope for two different orientations refractive indexes.

In another embodiment, the preliminary election radius partly is layering Δ r=r2-r1, wherein 0≤r ₁＜r ₂, and r ₂＜r ₀

In another embodiment, refractive index is along any or all change in radius in the sector, and the included angle of described sector is greater than zero degree, but is less than or equal to 180 °.

In another embodiment, the radius part is at 0＜Δ r≤r ₀Scope in, and position angle φ and the height z have any value, as long as coordinate points (r, φ is z) in core region.

In other embodiment of the present invention, stipulated the number of sector and the Angular Dimension and the radius size of sector, and stipulated the funtcional relationship between radius r and the relative index of refraction Δ %.The example of funtcional relationship is the step change type refractive index distribution curve of α distribution curve, step change type and band fillet, and the trapezoidal profile curve.

In other embodiment of the present invention, waveguide has a segmented core and stated number destination sector, has embedded the vitreum with specific size and shape in some zones of sector.Below described and had three and four sectors and embodiment that have particular fiber cored structure and embedded part.In certain embodiments, embedded part itself has the refractive index structures of layering.

In general, the embodiment of first aspect present invention can be single mode or multimode waveguide fiber.

A second aspect of the present invention is a kind of position angle and method of asymmetric waveguide fiber radially made.This method can be used for making single mode or multimode waveguide fiber.

One embodiment of the present of invention may further comprise the steps: change the shape of wire drawing prefabricated rods, then prefabricated stick drawn wire is become a waveguide fiber with round section.Like this, the shape of prefabricated rods just has been transferred to the cylinder symmetric feature that is comprised in the prefabricated rods, specifically has been transferred to the cylinder symmetric feature of fibre core.The shape of wire drawing prefabricated rods can be used such as any method in the methods such as etching, saw, boring or mill and change.

In an embodiment of this method, change prefabricated rods by formation hole or surface gap in prefabricated rods.Prefabricated rods after the change becomes the waveguide fiber with round section through follow-up wire drawing, make the fibre core of circular symmetry become radially or the position angle asymmetric.

Summary of drawings

Figure 1A is a sectional view, shows the present invention and has the waveguide of central core design or an embodiment of prefabricated rods.

Figure 1B is the refractive index distribution curve of obtaining by the 1B cross section of Figure 1A.

Fig. 1 C is the refractive index distribution curve of obtaining by the 1C cross section of Figure 1A.

Fig. 1 D is a sectional view, shows the present invention and has the waveguide of central core design or an embodiment of prefabricated rods.

Fig. 1 E is the refractive index distribution curve of obtaining by the 1E cross section of Fig. 1 D.

Fig. 1 F is the refractive index distribution curve of obtaining by the 1F cross section of Fig. 1 D.

Fig. 1 G is a sectional view, shows the present invention and has the waveguide of embedding core design or an embodiment of prefabricated rods.

Fig. 2 A is a sectional view, shows to have the waveguide that embeds core design or an embodiment of prefabricated rods.

Fig. 2 B is the refractive index distribution curve of obtaining by the 2B cross section of Fig. 2 A.

Fig. 2 C is a sectional view, shows to have the waveguide that embeds core design or an embodiment of prefabricated rods.

Fig. 2 D is the refractive index distribution curve of obtaining by the 2D cross section of Fig. 2 C.

Fig. 2 E is a sectional view, shows to have the waveguide that embeds core design or an embodiment of prefabricated rods.

Fig. 2 F is a sectional view, shows to have the waveguide that embeds core design or an embodiment of prefabricated rods.

Fig. 3 is a sectional view, shows the novel waveguide or the prefabricated rods that contain the hole.

Fig. 4 A and 4B and 4C and 4D are sectional views, show wire drawing after the prefabricated rods profile pass to fibre core.

Fig. 5 A and 5B are sectional views, show the influence of the hole of prefabricated rods to core shape.

Fig. 6 A and 6B and 7A and 7B show the sectional view of preform core and pipe assembly, and the waveguide to obtaining after the assembly wire drawing.

Fig. 8 A and 8B are sectional views, show the segmented core prefabricated rods of fluting, and the waveguide that obtains after the wire drawing.

Detailed description of the present invention

Breach 4 makes that the fibre core 2 of Figure 1A is that the position angle is asymmetric.In this illustrated novel prefabricated rods or waveguide fiber, the material of breach is identical with the material of covering 6.Figure 1B and Fig. 1 C show the vertical cross-section by fibre core respectively, and have provided the azimuthal variation of step change type refractive index distribution curve width.This specific distribution curve is a radial symmetry.

The prefabricated rods of Fig. 1 D or waveguide cores radially with all be asymmetric on the position angle.In this illustrated novel waveguide or prefabricated rods, fibre core is divided into four sectors.Shown in the sector 1F and 1E that obtain by fibre core, sector, two diagonal angles 8 and 10 is the other side's catoptron picture mutually.In Fig. 1 E, label 16 expression 1E sectors are to dependence radially, and it is band fillet step change type distribution curve or α distribution curve.In Fig. 1 F, the distribution curve 18 of 1F sector is the step change type refractive index distribution curve.Clad section 12 and 14 can comprise any material of refractive index less than adjacent core region.That is to say that the situation that the composition of covering generally only is subjected to fibre core cladding structure guided wave situation rather than radiant light to enter waveguide limits.

Fig. 1 G is according to the complicated structure of an example of novel prefabricated rods and waveguide.In this illustrated waveguide, fibre core or fibre core prefabricated rods 20 comprise a segmented core, and this fibre core has center 22 and adjacent annulus 28,24 and 26.Each district all uses corresponding relative index of refraction Δ %, refractive index distribution curve and is characterized by radius 32,34,36,38 and 40 determined zones.For example, center 22 and annulus 24 comprise separately mixes germanite English glass accordingly, and annulus 28 and 26 comprises quartz, and the relative size in each district is referring to accompanying drawing.The vitreum 30 that embeds is with asymmetric introducing fibre core prefabricated rods, and the refractive index of vitreum 30 is general different with its annular layering that is contacted 24 or 26.

Vitreum 30 can form in the following manner, and for example saw or grinding earlier used such as modes such as depositions to be filled in the container with glass then.The luminous energy that each layering 22,28,24,26 and 30 relative index of refraction and size thereof will determine 20 of fibre cores to deliver distributes.Luminous energy distributes on fibre core prefabricated rods or fibre core 20 and has determined the functional characteristic of waveguide.

In another embodiment of novel prefabricated rods or waveguide, shown in Fig. 2 A, fibre core is made of host glass 50, and host glass 50 has the

vitreum

42,44 and 48 of embedding.Vitreum extends in prefabricated rods or the waveguide that obtained by prefabricated stick drawn wire from the beginning to the end.Glass-clad 52 is wrapped in fibre core 50.The refractive index of glass of fiber core 50 is greater than the refractive index of covering 52.Fig. 2 B shows the cross section 2B by an embedded body, and it has the step change type refractive index distribution curve.The size that embeds the sectional area of

vitreum

42,44 and 48 can be identical or different, and glass-clad can have many relative orientations relatively.

The structure of Fig. 2 A is made by following method, promptly to prefabricated rods boring, makes the wall in gained hole smooth, and glass dust or rod are inserted in the hole.Another kind method is, with many bar construction fibre cores, then rod inserted in the holding tube, can use or not use insulating glass rod or glass particle.If these rods are combined, so just do not need holding tube with suitable glass isolated material.Surrounding layer can be deposited on the coupling unit, perhaps be made into a pipe, before the wire drawing or during pipe is collapsed on assembly.

Fig. 2 C shows another embodiment, and it comprises host glass and a plurality of embedding vitreum.Here, the general structure of waveguide 54 is similar to the structure of Fig. 2 A, except each embeds the refractive index distribution curve that vitreum 56,58 and 60 all has a segmented core.Fig. 2 D illustration a segmented core distribution curve, it is the cross section by an embedded body, wherein the center has higher relatively Δ %, coated outside two annuluses 62 and 64.In the figure, the Δ % of first ring 62 is less than second ring 64.Be appreciated that each layering all has a radially dependence of selecting from multiple possibility, such as the step change type distribution curve of α distribution curve or band fillet, and can regulate the relative Δ % of each layering, so that different waveguide functional characteristics to be provided.

The manufacture method of prefabricated rods or waveguide shown in Fig. 2 C manufacture method with prefabricated rods shown in Fig. 2 A or waveguide in fact is identical.

Fig. 2 E and Fig. 2 F show two other embodiment of this prefabricated rods or waveguide type.Embedding vitreum 66,68 and 70 among Fig. 2 E has the cross section of rectangle, and is arranged in the drift angle of equilateral triangle substantially.Also attempted embedding Vitrea other and arranged, such as diameter arrangement along core region.Core region 72 can comprise many kinds of shapes and form very much.In the simple case shown in Fig. 2 E, glass of fiber core 72 is step change type refractive index distribution curves, and presses the leaded light needs, and its refractive index is at least greater than the part of covering 74.

In Fig. 2 F, show a kind of five Vitrea structures of embedding that comprise.Here, four

vitreums

76,78,80 and 82 with diamond-shaped cross-section are made the symmetry layout about circular central core region 84.Clearly, this design can have many kinds to change.For example, embedded

body

76,78,80,82 and 84 refractive index can have the relative index of refraction different with fibre core 86.

As shown in Figure 3, the embedded body 88 in prefabricated rods or the waveguide can be the hole.The waveguide that has elongated hole along major axis can be made by forming elongated hole, for example forms by boring or etching in fibre core or the wire drawing prefabricated rods.The refractive index of glass of fiber core 90 must be different from the refractive index in hole, and asymmetric core region is provided thus.In wire drawing prefabricated rods shown in Figure 3, can be collapsed in the hole, to produce asymmetric fibre core.The shape of core region is decided by the relative viscosity of core material 90 and clad material 92 after collapsing in the hole.By control prefabricated rods in just by the thermograde of the part of wire drawing, can keep to the glass relative viscosity control.Relative viscosity also depends on the composition of fibre core and cladding glass.

Fig. 4 A and Fig. 4 B show the shape 98 that makes prefabricated rods among Fig. 4 A and pass to the core segment 102 of the waveguide 100 that obtains through prefabricated rods 98 wire drawings Fig. 4 B from the clad section 94 of prefabricated rods.When the symmetry of the initial symmetry of preform core and waveguide covering 104 was identical, the transmission shown in Fig. 4 A and Fig. 4 B took place.Shown cylinder symmetric among the figure, because this is and the present prefabricated rods manufacturing symmetry the most compatible with drawing process.Other symmetry also is fine, and for example the shape with prefabricated rods partly passes to the waveguide cores shape, i.e. the net shape stray circle cylindrical symmetry of waveguide.

Fig. 4 C shows the cross section of square segmented core prefabricated rods.After becoming cylindrical waveguide to the prefabricated rods heating and with its wire drawing, the segmented core 106 among Fig. 4 D is got square, because core material generation drag flow, to adapt to the cylindrical surface of covering.

Use similar mode, when the prefabricated stick drawn wire that has fibre core 110, covering 112 and elongated hole 108 in Fig. 5 A becomes cylindrical waveguide, it will produce asymmetric fibre core.But in this case, prefabricated rods is columniform, and core material fills up the hole during can Yin Lasi and is moved.As long as keep the shape of prefabricated rods when prefabricated stick drawn wire is become waveguide, fibre core will inevitably be out of shape, and promptly becomes asymmetric, to fill up the hole.

For example

With the prefabricated rods type shown in the outside vapor deposition process shop drawings 5A.Core region 110 is to mix germanite English, and covering 112 is quartzy.By boring, make hole wall smooth with etching solution then, in prefabricated rods, form hole 108.Prefabricated stick drawn wire is become a waveguide fiber, and its zero-dispersion wavelength is in the operation window of 1500nm, even waveguide generation dispersion shift.Compare with having the dispersion shift waveguide in 7 μ m to 8 mu m ranges of azimuthal symmetry fibre core and mode field diameter, this waveguide has very large mode field diameter 10.4 μ m.

Fig. 6 A and Fig. 6 B show the manufacture method of asymmetric fibre core.Make segmented core prefabricated rods 114,116 and 118 with any method in several known methods, described known method comprises OVD, axial vapor deposition method, plasma deposition processes or modified chemical vapor deposition method.The fibre core prefabricated rods is inserted in the pipe 122, in pipe 122, prefabricated rods is kept in position with spacer rod 120.Spacer rod can be made by quartz, doping quartz etc.If desired, covering 124 can be deposited on the pipe.Now, the wire drawing of prefabricated rods assembly can be become a waveguide fiber, shown in Fig. 6 B, its fibre core 130,132 and 134 is embedded in the glass of fiber core 128, and is wrapped in by glass-clad 126.Can directly carry out wire drawing to the assembly shown in Fig. 6 A.Another kind method is, before wire drawing, with the covering consolidation of deposition.In addition, before the deposition covering, can fully heat, make its surface softening, cause to each other to stick together, thereby form more stable structure, so that in surrounding layer or drawing process, use to pipe, fibre core prefabricated rods and spacer rod assembly.

Method shown in the manufacture method of the asymmetric fibre core shown in Fig. 7 A and Fig. 7 B and Fig. 6 A and Fig. 6 B is closely related.In Fig. 7 A, fibre core is encircled 136 and is being retrained, and ring 136 can make light propagate in step change type refractive index fibre core prefabricated rods 138,140 and 142 better.As mentioned above, can stablize the relative position of fibre core prefabricated rods in ring with spacer rod or glass dust.Can be directly to the assembly wire drawing of fibre core prefabricated rods, selectable isolated material, ring and outsourcing layer, perhaps elder generation is with assembly consolidation, wire drawing then.Fig. 7 B shows resulting waveguide fiber.

Fig. 8 A and 8B show the manufacture method of last routine asymmetric fibre core.In Fig. 8 A, the segmented core of prefabricated rods has center 144, first annulus 146 and second annulus 148.Prefabricated rods is passed through technologies such as grinding and cut, forms groove 152.These grooves can be empty, perhaps fill up material 150, and material 150 is different from the composition of covering 154.To the wire drawing of prefabricated rods assembly, form a waveguide, it has the asymmetric fibre core shown in Fig. 8 B.Here, can perhaps before wire drawing, deposit directly with the assembly wire drawing equally, consolidation or positioning step, so that each parts in the prefabricated rods keep suitable relative positioning.

Although in this announcement with describe specific embodiment of the present invention, the present invention is only limited by the accompanying Claim book.

Claims

1. A single-mode optical fiber having a radially and azimuthally asymmetric core, characterized in that it comprises:

a core region in contact with the surrounding cladding, at least a portion of the core region having a higher refractive index than at least a portion of the cladding;

The centerline of the waveguide is parallel to the length direction of the waveguide, and the waveguide has at least one core sector defined by first and second planes, and the first and second planes intersect a layer of the core area at the periphery, wherein Both the first and second planes contain the centerline and form an included angle φ≤180° at the centerline,

the core refractive index varies along at least a portion Δr of a preselected radius extending outward perpendicular to the centerline; and

The core refractive index at least one point on a predetermined radius within the at least one core sector is different from the core refractive index value at least one point on the preselected radius outside the at least one core sector.

2. A single-mode waveguide as claimed in claim 1, wherein the core region is cylindrical, and points in the core region have cylindrical coordinates, i.e. radius r, azimuth φ and center line height z, and the core The radius of the zone is r=r ₀ , and the preselected radius portion is in the range of 0<Δr≤r ₀ .

3. 2. The single mode waveguide of claim 2, wherein the preselected radius portion is a layer Δr=r ₂ -r ₁ , where 0 ≤ r ₁ <r ₂ and r ₂ <r ₀ .

4. The single-mode waveguide according to claim 2 or 3, wherein the preselected radius portion is along any radius in at least one sector, and the included angle of said at least one sector is 0<φ≤180°.

5. The single-mode waveguide according to claim 2, characterized in that, the preselected radius part Δr is in the range of 0< _Δr≤r0 , the azimuth angle of the radius is in the range of 0<φ≤360°, and the radius is from Any point z on the centerline is drawn.

6. A single-mode waveguide as claimed in claim 2, characterized in that the preselected radius portion is a layer Δr=r ₂ -r ₁ , where 0≤r ₁ <r ₂ , and r ₂ ≤r ₀ , including the The radius azimuth angle is in the range of 0<φ≤360°, and the layered radius is drawn from any point z on the center line.

7. The single-mode waveguide according to claim 2, wherein the fiber core has four sectors of equal volume, which are numbered 1-4 in the counterclockwise azimuth direction, and the boundary surface of each sector is 90° °, and Sector 1 and Sector 3 have a radial change in refractive index defined by the function f(r), while Sector 2 and Sector 4 have a radial change in refractive index defined by the function g(r).

8. 7. The single mode waveguide of claim 7 wherein g(r) is the step index and f(r) is the alpha profile.

9. The single-mode waveguide according to claim 2, wherein the fiber core has 4 sectors of equal volume, the boundary surfaces of each sector are at an angle of 90°, and the refractive index distribution of each sector is The curves each have a central portion with radius _rc and relative index of refraction _Δc and extend between the planes defining the sector,

a first annular region, which is in contact with the central portion, has an outer radius r ₁ , a relative refractive index Δ ₁ , and extends between planes defining the sector,

a second annular region in contact with the first annular region, having an outer radius r ₂ , a relative refractive index Δ ₂ , and extending between planes defining the sector,

a third annular region in contact with the second annular region, having an outer radius r ₃ , a relative refractive index Δ ₃ , and extending between planes defining the sector,

The first volume, which has a constant refractive index, is embedded in the core of the first sector, and part of the first plane defining the sector defines a first part of its surface, while the first, second and third a portion of the annular region defines a second portion of its surface,

The second volume, which has a constant refractive index, is embedded in the core of the first sector, and part of the second plane defining the sector defines the first part of its surface, while the first, second and third A portion of the annular region defines a second portion of its surface, wherein

The remaining three sectors all contain embeddings whose surfaces are defined in a manner corresponding to the volume embedded within the first sector, where the respective relative indices of refraction and radii satisfy the following inequalities:

0≤r _c <r ₁ <r ₂ <r ₃ ≤r ₀ , and Δ _c ≥Δ ₂ >Δ ₁ ≥Δ ₃ .

10. The single-mode waveguide of claim 2, wherein the core has three sectors, each sector comprises a first glass body with a constant refractive index, the first glass body is embedded in a second glass body with a constant refractive index. A glass body in which the refractive index of a first glass is greater than that of a second glass.

11. The single-mode waveguide of claim 10, wherein each first glass body is an elongated body with a long axis parallel to the centerline, wherein the vertical cross-section of the elongated body is selected from the group consisting of: Circles, ellipses and parallelograms.

12. The single mode waveguide of claim 2, wherein the core has three sectors, each sector comprising an elongated glass body having a central portion, a first annular portion and at least one additional annular portion A portion wherein a first annular portion wraps around and contacts the central portion and at least one additional annular portion touches and wraps around the annular portion, each elongated structure having a major axis parallel to the centerline.

13. A single-mode waveguide as claimed in claim 12, wherein the central part is a cylinder with radius r _c and refractive index Δ _c , and the annular part is a tube with outer radii r _i and refractive index Δ _i , where i=1...n, n is the number of annular parts, and Δ _i when i is even is larger than Δ _i when i is odd.

14. The single-mode waveguide of claim 2, wherein the core has four sectors, each sector comprising a first glass body having a relative refractive index _Δ1 embedded in each sector Within the first glass body is an elongated second glass body with a relative refractive index _Δ2 , wherein each elongated body is arranged symmetrically with respect to the center line.

15. A method for manufacturing radially and azimuthally asymmetric single-mode or multimode optical fibers, comprising the steps of:

a) making a single-mode or multimode optical fiber preform, said preform having a major axis, a core and a cladding, wherein any section of the preform perpendicular to the major axis is circular;

b) grinding, sawing or removing peripheral portions of the preform, altering the surface of the preform so that any section of the preform perpendicular to the major axis has substantially the same shape as any other section of the preform perpendicular to the major axis;

c) heating the preform and drawing it along its major axis into a waveguide fiber having a core, a major axis, and at any point on the major axis a circular cross-section perpendicular to the major axis, thereby providing A waveguide core with a modified preform shape is obtained.

16. The method of claim 15, wherein step b) includes the step of forming one or more indentations in the surface of the preform.

17. The method of claim 16, wherein manufacturing step a) includes the step of manufacturing a layered core preform having a central core region and at least one wrapping and contacting the central core region wherein the relative refractive index of the central region is different from that of the annular portion, and at least one or more notches penetrate into the annular portion.

18. A method for manufacturing a radially and azimuthally asymmetric single-mode or multimode waveguide, characterized in that it comprises the steps of:

a) manufacturing an optical fiber preform, said preform having a major axis, a core and a cladding, wherein any section of the preform perpendicular to the major axis is circular;

b) drilling, milling or fabricating one or more elongated axis-extending holes in the waveguide preform;

c) heating the preform and drawing it along its major axis into a waveguide fiber having a core, a major axis, and at any point on the major axis a circular cross-section perpendicular to the major axis, thereby providing A waveguide core with radial and azimuthal asymmetry.

19. A method for manufacturing radially and azimuthally asymmetric single-mode or multimode optical fibers, comprising the steps of:

a) making at least two optical fiber preforms, each preform having a major axis;

b) inserting at least two core preforms into a tube made of cladding glass to form a core preform-tube assembly having a major axis, wherein between the boundaries of the at least two core preforms and the tube Filling holes are formed inside;

c) heating the assembly and drawing it along its major axis into a waveguide fiber having a core, a major axis, and at any point on the major axis a circular cross-section perpendicular to the major axis, thereby providing Waveguide fibers with radially and azimuthally asymmetric cores.

20. The method of claim 19, further comprising the step of inserting cladding glass into interstitial holes formed between at least two core preforms and the tube before step c), wherein the The shape of the cladding glass is selected from the group formed by particles, rods and microspheres.

twenty one. The method of claim 19, wherein step a) of making comprises the step of making a layered core preform comprising a central core region and at least one wrapping and contacting the central core region The annular portion, wherein the relative refractive index of the central region is different from the relative refractive index of the annular portion.

twenty two. A multimode optical fiber having a radially and azimuthally asymmetric core, characterized in that it comprises:

The center line of the waveguide is parallel to the length direction of the waveguide, and the waveguide has four core sectors, each sector is defined by the first and second planes, and the first and second planes are in the periphery with one of the core areas intersecting in layers, where the first and second planes both contain the centerline and form an angle φ≤180° at the centerline,

The core area is cylindrical, and a point on the core area has cylindrical coordinates, that is, radius r, azimuth φ, and centerline height z, and the radius of the core area is r=r ₀ , and the refractive index is along the radius part Δr changes, and Δr is in the range of 0<Δr≤r ₀ , where

The volumes of the four core sectors are equal, and they are numbered 1-4 in the counterclockwise azimuth direction, and the boundary surfaces of each sector form an angle of 90°, and sector 1 and sector 3 have a function f( r) defines a radial variation of the refractive index, while sectors 2 and 4 have a radial variation of the refractive index defined by the function g(r).

twenty three. 22. The waveguide of claim 22 wherein g(r) is the step index and f(r) is the alpha profile.

twenty four. The waveguide according to claim 22, wherein the four core sectors have equal volumes, the boundary surfaces of each sector form an included angle of 90°, and the refractive index profile of each sector has a central portion having radius r _c and relative index of refraction Δ _c extending between the planes delimiting the sector,

25． The waveguide of claim 22, wherein each of the four core sectors includes a first glass body having a relative refractive index Δ ₁ , and embedded in the first glass body of each sector is a thin An elongated second glass body with a relative refractive index _Δ2 , wherein each elongated body is arranged symmetrically with respect to the center line.

26． A multimode optical fiber having a radially and azimuthally asymmetric core, characterized in that it comprises:

The center line of the waveguide is parallel to the length direction of the waveguide, and the waveguide has four core sectors, each sector is defined by the first and second planes, and the first and second planes are in the periphery with one of the core areas layered intersection, wherein both the first and second planes contain the centerline and form an angle φ≤180° at the centerline, where

The core has three sectors, each sector includes a first glass body with a constant refractive index, the first glass body is embedded in a second glass body with a constant refractive index, where the first glass has a higher refractive index than the second glass refractive index.

27． The waveguide of claim 26, wherein each first glass body is an elongated body with a long axis parallel to the centerline, wherein the vertical cross-section of the elongated body is selected from the group consisting of: circular, Ellipse and parallelogram.

28． The waveguide of claim 26, wherein each of the three core sectors comprises an elongated glass body having a central portion, a first annular portion and at least one additional annular portion, wherein the first annular portion wraps and contacting the central portion, and at least one additional annular portion contacting and surrounding the annular portion, each elongated structure having a major axis parallel to the centerline.

29． The waveguide of claim 28, wherein the central portion is a cylinder having a radius r _c and a refractive index Δ _c , and the annular portion is a tube having outer radii r _i and a refractive index Δ _i , where i=1...n, n is the number of annular parts, and Δ _i when i is even is greater than Δ _i when i is odd.