MXPA01002484A - Radially non uniform and azimuthally asymmetric optical waveguide fiber - Google Patents

Abstract

Disclosed is a single mode waveguide fiber and a method of making a single mode or multimode waveguide fiber which has an azimuthally and radially asymmetric core. This asymmetry provides additional degrees of freedom for use in forming a waveguide having particular performance characteristics.

Description

OPTICAL WAVE GUIDE FIBER WITH RADIAL IRREGULARITY AND AZIMUTAL ASYMMETRY BACKGROUND OF THE INVENTION This request is based on provisional application Serial No. 60 / 099,535, filed on 9/9/98, which is claimed as the priority date of this application. The invention relates to an optical waveguide fiber and to a method for making a waveguide fiber, having a refractive index profile that varies in the radial and azimuthal directions. The additional flexibility provided by azimuthal variation provides index profile designs that meet a broader number of waveguide fiber performance requirements than is possible using refractive index variation, only in the direction of radial coordinates . The recent development of waveguide fibers having refractive index profiles that vary in radial direction has shown that the particular properties of the waveguide can be optimized by adjusting this profile. For example, with the variation of the refractive index profile more generally than a simple step, it allows you to select the value of one or more properties of the waveguide without sacrificing a base set of properties that include attenuation, strength, or resistance. to the fold.

In addition, it has been shown that certain refractive index profiles of the azimuthal asymmetric core, such as those with elliptical, triangular or square nuclear geometry, provide useful waveguide properties, such as conservation or mixing of polarization modes. Therefore, it is expected that refractive index profiles that vary in azimuthal and radial directions offer the opportunity to fabricate waveguides that have new or better properties for use in telecommunication systems, signal processing or sensors. In the patent of E.U.A. 3,909,110, Marcuse, ('110 patent) a nucleus of azimuthal asymmetry of a multiple-mode waveguide is described. A calculation in the '110 patent indicates that periodic variations in the index in the radial and azimuthal directions would cause mode coupling, whereby the bandwidth increases, while losses due to coupling with radiation modes are limited. The concept was not extended to include single mode waveguides. Also, the scope of the '110 patent is quite limited, since it only refers to azimuthal and sinusoidal variations. In the description of the present nucleus of azimuthal and radial asymmetry, the concept of core sectors is introduced. A core sector is only a portion of the core that is joined by a point location of first and second radii that form an annular region in the waveguide. Each of the radii is different from each other and is less than or equal to the radius of the nucleus. The remaining boundaries of a sector are two planes oriented at an angle to each other, and each contains the centerline of the waveguide fiber. A change in the refractive index together with a line within a sector means that the refractive index is different between at least two points along the line.

DEFINITIONS The following definitions are in accordance with common usage in the art. A segmented core is a core that has a particular refractive index profile over a preselected radio segment. A particular segment has a first and a last point of refractive index. The radius of the center line of the waveguide to the location of this first point of refractive index is the inner radius of the region or segment of the core. Similarly, the radius of the center waveguide line to the location of the last point of the refractive index is the outer radius of the core segment. The relative index? is defined by the equation,? = (n-i2 -n22) 2n? 2, where ni is the maximum refractive index of the index profile segment 1, and n2 is a reference refractive index that, in this application, it is taken as the minimum refractive index of the coating layer. The term ? %, which is 100 X?, is used in the art.

The term refractive index profile or simply index profile is the relationship between? % or a refractive index and radius on a selected portion of the core. The term a-profile refers to the refractive index profile that follows the equation: n (r) = no (1 -? [R / a] a), where r is the radius of the nucleus,? is defined previously, a is the last point in the profile, r is chosen as 0 in the first point of the profile and a is an exponent that defines the shape of the profile. Other index profiles include a pitch index, a trapezoid index, and a rounded pitch index, where rounding is almost always due to doping diffusion in regions of rapid refractive index change.

BRIEF DESCRIPTION OF THE INVENTION In a first aspect of the invention, a single mode waveguide has a core having at least one sector. The refractive index of at least one point within the sector is different from that of the last point outside the sector. In the case where the sector is just half of the core, the choice of what constitutes a point within the sector can be chosen arbitrarily without any loss of profile definition precision. The changes of the refractive index profile of the core along at least a portion of a radius to provide radial asymmetry. At a pre-selected radius, the refractive index of the core within the sector is different from that outside the sector to provide azimuthal asymmetry.

In one embodiment, the general nucleus has cylindrical symmetry, and accordingly, is described for convenience in cylindrical coordinates, radius r, azimuth angle f and height of the z-center line. The portion of the preselected radius,? R together with the refractive index changes is on the scale 0 < ? r < r0, where r0, is the radius of the nucleus. The preselected radius in which the refractive index is different for at least two different azimuth angle choices is within this same scale. In another embodiment, the preselected radio portion is a segment defined as? R = r2-r ?, where, 0 < n < r2 and r2 < r0 Even in another modality, refractive index changes along any or all of the radii within a sector, in which the sector has included the angle f greater than zero, but less than or equal to 180 °. In another embodiment, the portion of the radius is on the scale 0 < ? r < r0, and the azimuth angle f and the height z have any value, as long as the coordinate point is in the core region. Other embodiments of the invention include those in which the number of sectors and the angular and radial size of the sectors are specified, and the functional relationship between the radius r and the relative index percentage is specified? %. The examples of the functional relationships are the a-profile, the profiles of step index and rounded pitch and the trapezoid profile. Even other embodiments of the invention include waveguides having a segmented core and a specific number of sectors including areas into which glass volumes of a particular size and shape have been incorporated. Three and four modalities of sectors having a particular kernel configuration and built-in portions are described below. In some embodiments, the incorporated portions themselves have a refractive index configuration in segments. In general, the embodiments of this first aspect of the invention may be single-mode or multi-mode waveguide fibers. A second aspect of the invention is a method for making a wave guide fiber of azimuthal and radial asymmetry. The method can be used to make single-mode or multi-mode waveguide fiber. One embodiment of the method includes the steps of modifying the figure of a stretch preform, and then stretching the preform into a waveguide fiber having a circular cross section. Thus, the shape of the preform is transferred to the characteristics of cylindrical symmetry contained within the preform, specifically, the characteristics of the cylindrical symmetry core. The figure of the stretch preform can be modified by any of several methods, such as chemical etching, sawing, drilling or grinding. In one embodiment of the method, the preform is altered with the formation of holes or slits in the surface thereof. The subsequent stretching of the altered preform in a waveguide fiber of circular cross-section causes a circular symmetry core to adopt a radial or azimuthal asymmetry. Even in another embodiment of the method, two or more core preforms are fabricated and inserted into a glass tube to form a preform assembly. The waveguide fiber resulting from the stretching of the preform assembly has the asymmetry of the assembly. The glass particles or separation rods can be incorporated into the tube / core preform assembly.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a cross-sectional view of one embodiment of the waveguide or preform of the invention, having a central core design. Figure 1B is the index profile taken through the section 1 B of figure 1A. Figure 1C is the index profile taken through section 1C of Figure 1A. Figure 1D is a cross-sectional view of a waveguide or preform embodiment of the invention having a central core design. Figure 1E is the index profile taken through section 1E of Figure 1D.

Figure 1 F is the index profile taken through the section 1F of Figure 1 D. Figure 1G is a cross-sectional view of a waveguide or preform embodiment of the invention, having a design of Built-in core Figure 2A is a cross-sectional view of a waveguide or preform embodiment having a built-in core design. Figure 2B is the index profile taken through section 2B of Figure 2A. Figure 2C is a cross-sectional view of a waveguide or preform embodiment having a built-in core design. Figure 2D is the index profile taken through the 2D section of Figure 2C. Figure 2E is a cross-sectional view of a waveguide or preform embodiment having a built-in core design. Figure 2F is a cross-sectional view of a waveguide or preform embodiment having a built-in core design. Figure 3 is a cross-sectional view of the novel waveguide or preform containing voids.

Figures 4A and B, and C and D, illustrate in transverse section the transfer of the outer figure from the preform to the core after stretching. Figures 5A and B illustrate in cross-section the effect in the figure of the core of the holes of the preform. Figures 6A and B, and 7A and B, illustrate a cross section of a preform core and tube assembly, as well as the resultant waveguide after stretching the assembly. Figures 8A and B illustrate a cross section of a core preform in notched segments, as well as the resultant waveguide after stretching.

DETAILED DESCRIPTION OF THE INVENTION The core 2 of Figure 1A is made of azimuthal asymmetry by slits 4. In this illustration of the novel waveguide preform or fiber, the slits comprise the same material as the coating layer 6. The perpendicular sections through the core 1B and 1C are explained in FIGS. 1B and 1C, respectively and show the azimuthal variation in amplitude of the pitch index profile. The particular profile is symmetrical in the radial direction. The preform or waveguide core of Figure 1 D is radial and azimuthal asymmetry. In this illustration of the novel waveguide or preform, the core is divided into four sectors. Each of the two diagonally opposed sectors, 8 and 10, are mirror images of each, as shown by sections 1F and 1E taken through the core. In Figure 1E, the radial dependence of the section 1E is illustrated as 16, a rounded passage or an a-profile. In Figure 1 F, the profile 18 of the section 1F is a step index profile. The coating portions 12 and 14 may comprise any material having a refractive index lower than that of the adjacent core region; that is, the composition of the coating layer in general is limited only by the condition in which the coating structure of the guide core, instead of irradiating light thrown into the waveguide. Figure 1G is an example of a more complex structure in accordance with the novel waveform preform and guide. In this illustration, the waveguide core or core preform 20 comprises a segmented core having a central region 22, and annular attachment regions 28., 24 and 26. Each region is characterized by a respective and relative refractive index?%, An index profile and an area determined by the spokes 32, 34, 36, 38 and 40. For example, the central region 22 and the ring region 24 may comprise respective germanium doped glasses, and annular regions 28 and 26 may include silica and the relative sizes of the areas may be as illustrated. The asymmetry is introduced into the core preform by incorporated glass volumes 30, which generally have a refractive index different from ring segment 24 or 26 contacted by glass volumes 30. Glass volumes 30 can be formed when grinding or cutting with saw, for example, followed by filling the volumes with a glass by any of several means including deposition. The distribution of the light energy carried by the core 20 will be determined by the relative refractive indices and the sizes of the segments 22, 28, 24, 26 and 30. The functional properties of the waveguide are determined by the distribution of energy luminous through the core or core preform 20. In another embodiment of the novel preform or waveguide, the core consists of a matrix glass 50 having incorporated glass volumes 42, 44 and 48, as illustrated in FIG. Figure 2A. The glass volumes extend from one end to the end of the preform or the stretched waveguide of the preform. The coating glass layer 52 surrounds the core 50. The glass refractive index of the core 50 is greater than that of the coating layer 52. The section 2B through one of the incorporated volumes is shown in Figure 2B as a step index profile. The cross-sectional sizes of the incorporated glass volumes 42, 44 and 48 can be the same or different, and various orientations are possible relative to the coating glass layer. The structure of Figure 2A can be made by drilling a preform, smoothing the walls of the resulting holes and filling the orifices with glass powder or sticks. Alternatively, the core may consist of rods which are then inserted into a support tube, with or without the use of rods or sparking glass particles. The need for a support tube can be eliminated by welding the rods by the use of an appropriate glass spacer material. The coating layer can be deposited in the rod-welded assembly or it can be manufactured as a tube that shrinks in the assembly before or during stretching. Another embodiment that includes a matrix glass and a plurality of incorporated glass volumes appears in Figure 2C. Here, the macrostructure of the waveguide 54 is similar to that of Figure 2A, except that the incorporated glass volumes 56, 58 and 60 have a segment refractive index profile. An example of the segment core profile is illustrated in Figure 2D, which is a cross section through one of the embodied volumes wherein a central region with a relatively high% is surrounded by two annular regions 62 and 64. In the illustration the first ring 62 is lower in?% than the second ring 64. It is understood that each of the segments may have a radial dependence selected from a plurality of possibilities, such as an a-profile or a passing profile rounded and the relative?% of the segments can be adjusted to provide different waveguide functional properties.

The methods for making the wave guide or preform of Figure 2C are essentially identical to the method for making the wave guide or preform of Figure 2A. Two additional embodiments of this type of preform or waveguide are illustrated in Figures 2E and 2F. The incorporated glass volumes 66, 68 and 70 in Figure 2E have a rectangular cross section and are placed substantially at the vertices of an equilateral triangle. Other placements of the incorporated glass volumes are contemplated, such as placement along a diameter of the core region. The core region 72 may comprise several figures and compositions. In the simple example illustrated in Figure 2E, the core glass 72 is a pitch index profile and, since it is required to guide light, has a higher refractive index than at least a portion of the facing layer 74. Figure 2F illustrates a configuration comprising cinoc incorporated glass volumes. Here, four glass volumes of diamond cross section 76, 78, 80 and 82 are arranged symmetrically in a circular core region 84. It is clear that numerous variations of this design are possible. For example, the refractive indices of the built-in volumes 76, 78, 80, 82 and 84, each have a different relative index compared to that of the core 86. As shown in Figure 3, the incorporated volumes 88 in a preform or a waveguide can be hollow. A waveguide having elongate voids along the prolonged axis can be made with the formation of elongated voids, for example, by drilling or etching into a core or stretching preform. The glass index of the core 90 is different, by necessity, from the recesses, whereby an asymmetric core region is provided. In the case where Figure 3 represents a stretching preform, the recesses may collapse during the stretching process to produce an asymmetric core. The figure of the core region after the collapse of the voids is determined by the relative viscosity of the core material 90 and the coating layer material 92. The control of the relative viscosity of the glasses is preserved by controlling the gradient of the glass. temperature in the portion of the preform that is stretching. Also, the relative viscosity depends on the composition of the core and the coating glass. Figures 4A and 4B illustrate the transfer of a preform figure, 98 in Figure 4A, from the coating layer portion 94 of the preform to the core portion 102 in Figure 4B of a wave guide 100 stretched from the preform 98. The transfer occurs as shown in Figures 4A and 4B when the initial symmetry of the preform core 96 is the same as the symmetry of the waveguide coating layer 104. The cylindrical symmetry is illustrated because it is the symmetry much more compatible with preform manufacturing and current stretching procedures. Other symmetries are possible, for example, by partial transfer of the figure from the preform to the figure of the waveguide core, that is, the final figure of the waveguide starts from the cylindrical symmetry.

In Figure 4C there is a cross-section of a segment-shaped preform having a square shape. After heating and stretching the preform into a cylindrical waveguide, the segmented core 116 in Figure 4D adopts a square shape by the viscosity flow of the core material which becomes conformable to the cylindrical surface of the coating layer. In an analogous manner, the preform of Figure 5A, having core 110, liner layer 112 and elongated recesses 108, will produce an asymmetric core when stretched in a cylindrical shaped waveguide; however, in this case, the preform is cylindrical and the movement of the core material is due to the filling of the voids during stretching. As long as the shape of the preform is preserved by stretching it in a waveguide, the core must be distorted, that is, become asymmetric, to fill the gaps.

EXAMPLE A preform of the type illustrated in Figure 5A was made using the external vapor deposition process. The core region 110 was silica doped with germanium, and the coating layer 112 was silica. Hollows 108 were formed in the preform by drilling followed by smoothing the hollow walls using a solution for chemical etching. The preform was stretched on a waveguide fiber having the zero dispersion wavelength in the operation window 1500 nm, ie, the waveguide was modified in dispersion. The waveguide had a large mode field diameter of usually 10.4 μm, compared to the mode field diameters in the 7 μm to 8 μm scale for scattered modified waveguides that have a symmetry core azimuthal A method for making an asymmetric core is illustrated in Figures 6A and 6B. The segment core preforms 114, 116 and 118 are fabricated using any of the various known methods, including exterior vapor deposition, axial vapor deposition, plasma deposition or modified chemical vapor deposition. The core preforms are inserted into the tube 122 where they are held in place by spacer rods 120. The rods can be silica, doped silica or the like. If necessary, a coating layer 124 may be deposited on the tube. The preform assembly can now be stretched in a wave guide fiber having cores 130, 132 and 134 incorporated in glass core 128, and may be surrounded by a coating glass layer 126 as shown in Figure 6B. The assembly as illustrated in Figure 6A can be stretched directly. Alternatively, the deposited coating layer can be consolidated before stretching. In addition, prior to coating deposition, the tube, the core preform and the spacer rod assembly can be heated sufficiently to soften the surfaces thereof and cause them to adhere to each other, thereby forming a more stable structure. for use in the coating or stretching process. The method for making an asymmetric core illustrated in Figures 7A and 7B has a close relationship with that illustrated in Figures 6A and 6B. In Figure 7A, the core is joined by the ring 136 which serves to better contain the light propagating in the step index core preforms 138, 140 and 142. As already described, the spacer rods or glass powder they can be used to stabilize the relative positions of the core preforms within the ring. The core preform assembly, the optional spacer material, the ring and the coating material can be stretched directly or first consolidated and then stretched. The resulting waveguide fiber appears in Figures 7B. A final example of a method for forming an asymmetric core is illustrated in Figures 8A and 8B. In Figure 8A, a preform has a core in segments with a central region 144, a first annular region 146 and a second annular region 148. The preform was ground or cut with saw or the like to form notches 152. The notches may be empty or filled with material 150, which is a different material in composition from that of coating layer 154. The preform assembly is stretched to form a waveguide having an asymmetric core, as shown in Figure 8B. Here, once again, the assembly can be stretched directly, or the steps of deposition, consolidation or adhesion can be carried out before stretching to hold the parts of the preform in proper relative registration.

Although the particular embodiments of the invention have been described herein, however, this is limited only by the following claims.

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - A single-mode optical waveguide fiber having a radial and azimuthal asymmetric core comprising: a core region in contact with a surrounding coating layer, at least a portion of the core region having an index of refraction that is greater than the refractive index of at least a portion of the coating layer; said core region has a central line that extends along the length of the waveguide fiber and is divided into at least a first and a second set of diagonally opposed sectors, wherein the first set of diagonally opposed sectors has a radial change in the refractive index defined by a function f (r), and the second set of diagonally opposed sectors have a radial change in the refractive index defined by a function g (r), where f (r) is an a-profile or a rounded-pitch profile and g (r) is a passing profile.

2. The waveguide fiber of a single mode according to claim 1 further characterized in that the respective diagonally opposed sectors are mirror images of each other.

3. The optical waveguide fiber of a single mode according to claim 1 or 2, further characterized in that the respective sectors have an equal volume.

4. - The single-mode optical waveguide fiber according to claim 1, further characterized in that the function g (r) is defined on a scale of radius? Rg and the function f (r) is defined on a scale of radio? rf and? rg? ? rf.

5. The waveguide of a single mode according to claim 2, further characterized in that the core has 4 sectors of equal volume, the planes of union of each sector has an included angle of 90 °, the index profile of The refraction of each sector has a central portion of radius rc and relative index? c, which extends between the planes that join the sector; a first annular region in contact with the central portion, having an outer radius n, relative index? -i, and extending between the pianos joining the sector; a second annular region in contact with the first annular region, having an outer radius, relative index? 2, and extending between the planes joining the sector; a third annular region in contact with the second annular region, having an outer radius r3 relative index? 3, and extending between the planes joining the sector; a first volume of constant refractive index incorporated in the core of the first sector, and joined in a first part of its surface by a part of the first plane joining the sector, and joined in a second part of its surface by a part of the first, second and third ring regions; a second volume of constant refractive index incorporated in the core of the first sector and joined in a first part of its surface by a part of the second plane joining the sector, and joined in a second part of its surface by a part of the first , second and third ring regions, where, each of the three sectors contain built-in volumes that have surfaces joined in a manner corresponding to the volumes incorporated in the first sector, where relative indexes and radii are still missing of equality 0 = rc < n < r2 < rz = r0 and? c > ? 2 > ? i? ?3.

6. The waveguide of a single mode according to claim 2, further characterized in that the core has three sectors, and each sector comprises a volume of a first glass of constant refractive index incorporated in a volume of a second glass of constant refractive index, in which the refractive index of the first glass is greater than the refractive index of the second glass.

7. The waveguide of a single mode according to claim 6, further characterized in that each of the volumes of the first glass is an elongated body having the extended axis aligned in a position parallel to the center line, wherein the perpendicular cross section of the elongate body is selected from the group consisting of a circle, an ellipse and a parallelogram.

8. The single-mode waveguide according to claim 2, further characterized in that the core has three sectors, and each sector contains an elongated glass volume having a central portion, a first annular portion that surrounds and is in contact with the central portion, and at least one additional annular portion in contact with the annular portion that at least surrounds an additional annular portion, wherein the prolonged axis of each of the elongated structures is parallel to the center line.

9. The single-mode waveguide according to claim 8, further characterized in that the central portion is a cylinder having a radius rc and a relative index? C, and the annular regions are tubes having respective outer radii. r and relative index? where i = 1 ... n, and n is the number of annular portions, where? by i = an even number is greater than? ¡by i equal to a non number.

10. A method for producing a single-mode optical waveguide fiber or multiple radial and azimuthal asymmetry mode comprising the steps of: a) manufacturing an optical waveguide fiber preform in a single mode or mode multiple having a prolonged axis, a core and a coating, wherein any cross section of the preform, perpendicular to the prolonged axis, is circular; b) grinding, sawing or otherwise removing the peripheral portions of the preform to alter the surface of the preform, so that any cross section of the preform taken perpendicular to the extended axis has a figure that is essentially the same that the figure of any other cross section of the preform perpendicular to the prolonged axis; c) heating and stretching the preform along the prolonged axis into an optical waveguide fiber having a core, a prolonged axis and a circular cross section perpendicular to the axis extended at any point along the extended axis, to provide a fiber core Optical waveguide guide having the figure of the altered preform

11. The method according to claim 10, further characterized in that step b) includes forming one or more slits in the surface of the preform.

12. The method according to claim 11, further characterized in that the manufacturing step a) includes the step of manufacturing a core preform in segments comprising a central core region and at least one annular portion surrounding and being in contact with the region of the central core, wherein the relative refractive index of the central region is different from the relative refractive index of the annular portion, and one or more slits penetrate at least the annular portion.

13. A method for producing a single-mode waveform or multiple mode of radial and azimuthal asymmetry comprising the steps of: a) manufacturing an optical waveguide fiber preform having a prolonged axis, a core and a coating, wherein any cross section of the preform, perpendicular to the prolonged axis, is circular; b) piercing or grinding or otherwise producing in the waveguide preform one or more holes extending along the prong axis; c) heating and stretching the preform along the prolonged axis in a wave guide fiber having a core, a prolonged axis and a circular cross section perpendicular to the extended axis at any point along the same, to provide a core of radial and azimuthal asymmetry waveguide fiber.

14. - A method for producing a single-mode optical waveguide or multiple mode of radial and azimuth asymmetry comprising the steps of: a) fabricating at least two waveguide fiber core preforms, each with a prolonged axis; b) inserting at least the two core preforms into a lining glass tube to form a core / tube preform assembly having a prolonged axis, wherein the interstitial voids are formed between the limits of at least two core preforms and the inside of the tube; c) heating and stretching the assembly along the extended shaft in a waveguide fiber having a core, a prolonged axis and a circular cross section perpendicular to the elongated shaft at any point along the same, to provide a fiber of waveguide that has a radial and azimuthal asymmetry core.

15. The method according to claim 14, further characterized in that it includes the step, before step c), of inserting into the interstices formed between at least two core preforms and the tube, coating glass having a selected figure from the grconsisting of particles, rods and microspheres.

16. The method according to claim 14 further characterized in that the manufacturing step a) includes the step of manufacturing a core preform in segments comprising a central core region and at least one annular portion that surrounds and is in contact with the central core region, wherein the relative refractive index of the central region is different from the relative refractive index of the annular portion.

17. - A multi-mode optical waveguide fiber having a radial and azimuthal asymmetric core comprising: a core region in contact with a surrounding coating layer, at least a portion of the core region having an index of refraction greater than the index 5 refraction of at least a portion of the coating layer; The waveguide has a central line parallel to the prolonged dimension of the waveguide, and the waveguide has four core sectors, each joined by a first and a second plane, and a segment of the periphery of the waveguide. core region intercepted by the first and second planes, where the

The first and the second planes contain the center line and form an included angle therein f < 180 °, where, the core region is cylindrical in shape and a point in the core region has cylindrical coordinates, radius r, azimuth angle f, and height of the center line z, and the radius of the core region is r = r0, and the refractive index changes along a portion of the radius? r 15 on the 0 scale < ? r < r0, where, the four core sectors have the same * volume numbered consecutively from 1 to 4 in a right azimuth direction, and the delimiting planes of each sector have an included angle of 90 °, and sectors 1 and 3 have a radial change in the refractive index defined by a function f (r), and sectors 2 and 4 have a radial change 20 in the refractive index defined by a function g (r). 18. The waveguide according to claim 17, further characterized in that g (r) is a step index and f (r) is an a-profile.

19. - The waveguide according to claim 17, further characterized in that the four sectors of the core are of equal volume, the planes of union of each sector have an included angle of 90 °, the profile of refractive index of each sector has a central portion of radius rc and relative index? c, which extends between the planes joining the sector; a first annular region in contact with the central portion, having an outer radius n, relative index? -i, and extending between the planes joining the sector; a second annular region in contact with the first annular region, having outer radius r2, relative index? 2, and extending between the planes joining the sector; a third annular region in contact with the second annular region having outside radius r3, relative index 3 3 and extending between the planes connecting the sector; a first volume of constant fraction index incorporated in the core of the first sector and joined in a first part of its surface by a part of the first plane joining the sector, and joined in a second part of its surface by a part of the first , second and third ring regions; a second volume of constant refractive index incorporated in the core of the first sector, and joined in a first part of its surface by a part of the second plane joining the sector, and joined in a second part of its surface by a part of the first, second and third ring regions, where each of the three remaining sectors contains built-in volumes that have surfaces joined in a manner corresponding to the volumes incorporated in the first sector, where relative indexes and radii are still missing of equality, 0 < rc < n < r2 < r3 < ro and? c > ? 2 > ? i? ?3.

20. The waveguide according to claim 17, further characterized in that the four sectors of the core comprise a first volume of glass having relative index? 1, and an elongated volume is incorporated in the first glass volume of each sector. of a second glass having relative index? 2, wherein the respective elongated volumes are placed symmetrically on the center line.

21. A multi-mode optical waveguide fiber having a radial and azimuthal asymmetric core comprising: a core region in contact with a surrounding coating layer, at least a portion of the core region having a refractive index greater than the refractive index of at least a portion of the coating layer; the waveguide has a central line parallel to the prolonged dimension of the waveguide, and the waveguide has four core sectors joined by a first and a second plane, and a segment of the periphery of the core region intercepted by the first and second planes, wherein the first and second planes contain the central line and form an included angle f < 180 °, where, the core reaction is cylindrical in shape and a point in the core region has cylindrical coordinates, radius r, azimuth angle f and center line height z, and the radius of the core region is r = r0 , and the refractive index changes along a portion of radius? r on the scale 0 < ? r < r0) wherein, the core has three sectors, each sector comprises a volume of a first glass of constant refractive index incorporated in volume of a second glass of constant refractive index, in which the refractive index of the first glass is greater to the refractive index of the second glass.

22. The waveguide according to claim 21, further characterized in that each of the first glass volumes is an elongated body having the extended axis aligned in a position parallel to the center line, wherein the perpendicular cross section of the The elongated body is selected from the group consisting of a circle, an ellipse and a parallelogram.

23. The waveguide according to claim 21, further characterized in that the three core sectors contain an elongated glass volume having a central portion, a first annular portion that surrounds and is in contact with the central portion, and at least one additional annular portion in contact with the annular portion surrounding at least one additional annular portion, wherein the prolonged axis of each of the elongated structures is parallel to the center line. 24.-. The waveguide according to claim 23, further characterized in that the central portion is a cylinder having a radius rc and relative index? C and the annular regions are tubes having respective outer radii r and relative index?, Where i = 1 ... n, and n is the number of annular portions where? By i = an even number is greater than? ¡By i equal to a non number.