KR20010088803A - Waveguides having axially varying structure - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to optical waveguide fiber preforms and optical waveguide fibers drawn therefrom, and more particularly, the density and effective refractive index of the cladding layer 42 is altered in a pre-selected axial direction along the waveguide preforms and associated waveguide fibers. It is about inducing. The axial change in the density of the cladding layer 42 is due to the portion of the clad in which the base clad glass differs from the air or glass composition. The axial change in the clad changes the signal mode power distribution, thus changing the important waveguide fiber parameters such as the signal of magnitude and dispersion, the cutoff wavelength and the zero dispersion wavelength. The invention also relates to preforms in which the waveguide fibers are drawn, which preforms light due to the photoparticulate crystal structure of all of the clad layer lengths or segments of the clad layer length.

Description

Waveguides with axially varying structure

Optical waveguide fibers having a cladding layer of regular structure have been discussed. For example, the regular structure of the cladding layer is described by Knight (Knight et al., "All Silica Single Mode Optical Fibers with Photonic Crystal Clads", Optics Letters. V. 21, No. 19, 1 October 1996) and Birks (Birks et al., "Continuous single mode photonic crystal fibers", Optics Letters. V.22, No. 13, 1 July 1997) and the like, may be photonic crystals. Both papers describe single mode fibers with a silica core and a porous silica clad. Pores or voids in the silica cladding layer extend and extend from end to end of the cladding layer. The pores are arranged in a regular hexagonal pattern to produce a cladding layer with light particle crystals. The waveguide fibers are made to be single mode fibers at any wavelength. Another study on waveguide fibers having a cladding layer with porous or pores is described in EP 0810453A1. In the publication, the cladding layer includes elongated pores that act to lower the average refractive index of the cladding layer. The elongated pores are not arranged in a regular pattern so that the light guiding mechanism in the waveguide is refracted at the core-clad boundary.

The limited range of necessary cut-off wavelengths, or the potential absence of any cut-off wavelengths, obtainable in the photoparticle crystal cladding layer has great advantages in single mode waveguide designs. In addition, the relative refractive index difference Δ is useful in view of additional design variations due to the cladding layer containing a certain volume of irregular pores. The volume is controlled by adjusting the air inlet portion of the fiber as described below.

However, none of these designs provide an axial change in relative refractive index. The axial change is useful in single mode fiber designs for the purpose of controlling dispersion. In addition, since the refractive index axis change is due to the change in the cladding layer, new parameters such as pore volume, pore cross section, and pore pattern are available to change the mode power distribution in the waveguide and change important waveguide fiber properties. Let's do it. Combination of axial changes is expected in clad structures with multiple pore index profile designs, which will provide single waveguide fiber properties. The cladding layer combined with the light guide of the light particle crystal and the light guide being refracted is considered to be very useful in waveguide design for dispersion control. Additionally, the present invention includes a cladding layer structure composed of a material that replaces pores that add fluidity to a regular, irregularly distributed, uniform waveguide fiber design.

This application claims this priority based on Provisional Application No. 60 / 100,349, filed on September 15, 98.

The present invention relates to an optical waveguide preform or fiber having a structure that changes in the axial direction. In particular, the novel preform or waveguide exhibits a clad layer refractive index that varies over waveguide length, which is due to a change in clad layer porosity or composition. The present invention includes the novel waveguide preforms and methods of making the fibers.

1A is a cutaway view of a tube having a circular cross section.

1B is a cutaway view of a tube having a hexagonal cross section.

2 is a schematic diagram showing a tube with a segment of reduced dimension.

3 is a schematic view showing a hexagonal tube arranged around a core preform and inserted into a large support tube.

4 is a cutaway view of a waveguide with preformed or core regions and a porous or hybrid cladding layer.

FIG. 5 is a cross-sectional view illustrating a cross section of a waveguide having a porous clad layer in which the core region and the pores are due to gap pores between the clad layer tubes. FIG.

6A and 6B are cross-sectional views showing cross-sections of waveguides having preforms or solid and porous or hybrid clad layers, respectively.

6C, E, and G are graphs showing the core index profile of waveguides with preformed or solid phase cladding layers.

6D, F, and H are graphs showing the core index profile of waveguides with preformed or porous or hybrid clad layers.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The novel waveguide preforms or waveguide fibers of the present invention allow the use of the guiding properties of the cladding layer with lower axial change refractive index than the waveguide core. Waveguide fibers are expected to be performed by structuring the cladding layer so that the guiding acts as photoparticulate crystals with band spacing, and the desired cladding properties can be obtained by changing the clad material composition or distribution.

One embodiment of the present invention changes the cladding layer by including pores of a particular size and shape. In a similar embodiment, a material having a dielectric constant different from that of the base clad glass was included in place of the pores. In other cases, the mode power distribution of the signal light in the waveguide was affected and thus affected the waveguide properties. Core and cladding may vary on new waveguide preforms or fibers, allowing optical waveguide fiber designers more freedom in design.

Interesting embodiments disclosed and described herein include pores or glass filaments extending on the clad layer. Two possible structures of the clad layer are shown in Figs. 1A and 1B which show the cut planes of the tubes with centerline pores 4 and 6, respectively. The material around the pores has a circle 2 in FIG. 1A and a hexagon 8 in FIG. 1B. The contour is selected such that the desired pattern of pores formed by the structure on the clad layer is maintained. The pores 4 and 6 are filled with a material consisting of glass having a dielectric constant different from the surrounding or matrix glass material.

The steps of the method of changing one of the substructures are shown in FIG. Indentation 12 was formed on test tube 10. The indentation produced a confined region 14 on the filament separated by a central pore or region 16 and the central region of the tube was not violated. The combination of the above structures around the core region provides a cladding layer having a change in axis in refractive index. In addition, the structure may be arranged as if the central pores or filaments 18 form a regular arrangement. The regular arrangement may have a pitch of photoparticulate crystals designated for use in the desired wavelength range. Currently, suitable wavelength ranges for telecommunications use are about 600 nm to 2000 nm.

The waveguide preform according to the invention is shown in FIG. 3. In this embodiment, the undercarriage is tubes 20 and 22 with exactly the same hexagonal cuts. The shading difference between the tubes 20 and 22 indicates that a number of substructures can be formed into secondary structures bonded to the clad layer. Intersecting shading may have parts with different substructures, and individual substructures may be combined to form a participant pattern with a larger part area. Such combinations can be made in the embodiment described where the secondary structure is extruded, and combined and made into the desired cut plane area. Extrusion and drawing processes are disclosed and described on US Pat. No. 60 / 094,609, filed Jul. 30, 1998.

The present invention has advantages in the production of novel waveguide preforms and fibers, and dispersion compensating or dispersion control waveguides, and is a method of making waveguide preforms and fibers that vary the design of waveguides.

A first aspect of the invention is an optical waveguide fiber preform consisting of a core glass region and a clad glass layer located on the core glass. For the convenience of the technique, the clad glass layer is described by dividing the segments along the preshaft axis. The density of the clad glass changes the direction called preform axis parallel to the core area, and the clad glass density changes from high to low or from low to high, from segment to segment. That is, each adjacent segment density is not a single function of axial position.

The preform clad layer density can be altered from high to low to low to high in adjacent segments by altering the porosity of the clad layer. In particular, each adjacent segment along the preform axis can intersect a state in which the cladding layer contains pores and no pore distribution in the cladding layer. In a novel preformed embodiment, the pores extend and are arranged in a regular arrangement that may have a spacing, or pitch, between the points corresponding to the pores. The pitch can be selected within a number of different ranges. The preform pitch for use at the optimal telecommunication wavelength was chosen to favor the fibers drawn from the preform, with a range of 0.4 micrometers to 20 micrometers. Typical outer diameter of glass fibers is about 125 μm. Subranges of this range are very effective for the drawn fiber pitch to form optical particle crystals within a range of telecommunication signal wavelengths. However, the inventors have verified that spacing or pitches in the range of tens of microns can be usefully used in the fabrication of waveguides with varying cladding. Although no range above 20 μm is mentioned herein, the inventors are also convinced of the utility of the wider cladding layer-shaped pitch. The upper limit of spacing or pitch is actually a practical limit determined from the cladding layer thickness.

We have found that the pitch as well as the diameter of the extended pores is important in determining the properties of the waveguide fibers drawn from the preform. In one embodiment of the present invention, the ratio of pore diameter to pitch of the extended pore array is about 0.1 to 0.9.

The preformed core glass has a wide range of refractive index profiles. The refractive index profile of a region is the value of the refractive index or the relative index of refraction, Δ, depending on the function of the radial position through the region. Definitions of refractive index profiles, segmented profiles, Δ and α-profiles are shown in known art and US Pat. No. 5,553,185 to Antos et al. Or US Pat. No. 5,748,824 to Smith, et al., Incorporated herein by reference. Thus, the core region of the preform is one of stepped, trapezoidal, sloped or sharp, or α-profiled. In addition, the core region may be segmented into two or more portions, and each portion may be located on the cross profile described above. This core region design, associated with the cladding layer modification, determines the dispersion properties and other performance properties of the waveguide fibers.

The refractive index of base glass materials, such as silica, can be changed by adding dopants such as Germania, alumina, phosphorus, titania, boron, fluorine and equivalents. Can be. Rare land dopants such as erbium, ytterbium, neodymium, tulium, or praseodymium can also be added to form preforms and drawn into optically extending waveguide fibers. have.

In another embodiment of the novel preform, the clad density varies between two values, from segment to segment, part by part along the preform axis. This change, together with the preselected core structure, determines the dispersion control properties of the fiber as described above. In addition, the density is controlled by adjusting the porous volume control of the cladding layer segments. Alternatively the density is controlled by adjusting the volume of dopant glass added to the base clad layer glass. The dopant glass may appear as filaments extending on the clad base glass. The filaments are regularly arranged in the analysis of the arrangement of elongated pores discussed above. The filaments can be manufactured using various processes known in the art, but the filaments are produced by filling with elongated pores. If one skilled in the art wants a filament comprising a cladding layer in contact with light by means of photonic crystals with full band gap, the size and spacing of the filament ranges from about 0.4 μm to 5 μm in pitch, and matrix Each glass must have dielectric constants, and the glass consisting of glass columns falling within this category must be distinguished by three factors.

The filaments filled with a porous cladding layer or cladding layer guide light by refraction at the interface of the core and the clad, and the refractive index of the core is higher than what is considered as the average refractive index of the structured clad layer.

The above-described preforms are made for the purpose of drawing optical waveguide fibers. Accordingly, the present invention includes an optical waveguide drawn from a novel preform.

The invention also relates to a process for producing the novel preforms in which the novel waveguides are drawn. In a first method, core preforms are made by several methods known in the art, including external and axial deposition, and MCVD or plasma deposition techniques. The core portion of the preform is a non-porous solid phase. The intersecting core preforms are tubes with open ends, and nothing changes prior to preform preparation. The tube will collapse during the drawing step to produce a solid glass core region that is homogeneous or doped (when the tube is doped). The majority of glass that is open expanded over the entire length of the tube can be made. Many glass tubes with ends that extend through the tube have been made. The tube is dimensioned at a number of preselected positions and arranged around the centrally located core preform. Each of the reduced dimension tubes is necessarily the same as all other reduced dimension tubes. The tube collapses partially or fully at the reduced dimension position. The reduced arrangement of dimension tubes around the centrally located core preform is a preform with an axial change in clad layer density.

The tube may be circular or three or more polygons. The arrangement of the tubes around the central core preform can be irregular or regular and have a geometry specifically chosen according to the type of signal and wavelength interference, ie refracted or photoparticulate crystals, which is desirable for the core-clad interface. In the case of a clad layer with optical particle crystal properties and full band spacing, the pitch of the regular arrangement of the tubes is largely in accordance with the optical wavelength signal carried out in the waveguide.

Instead of intermittently distributed pores over the entire length of the tube, the tube is made using an outer matrix glass and a glass column contained therein. Each segment of the tube may comprise a glass making powder or glass filament section in the manufacture of the reduced dimension portion, or the filament may be filled into the tube before the dimension reduction is performed. Among the above techniques, filament or powder filling can be used in the process of providing a tube filled with a fill material having a significantly lower softening temperature, for example 20 ° C. or more, than the tube. The opposite case where the column has a higher softening temperature than the tube is possible by placing the column and tube combination in a large tube with a similar softening temperature. When waveguide fibers drawn from the configured preform act as photoparticulate crystals, the dielectric constant difference between the matrix glass and the column glass should be less than three times.

In order to draw preforms made in this way, several means must be provided to support together a part of the preform. In one embodiment of the novel preform, the tube and core preform is placed in a large tube and the large tube collapses onto the tube and core preform combination.

In another embodiment of the preform, the tube and core preforms are inserted and vitrified into layers or soot deposited on chucks and tubes. The insertion onto the chuck can be made by bundling the tube and core preforms prior to the chucking or deposition process. The bunching process may be performed by thermally bonding each part of the preform to each other. Alternative frits may be used to glass solder each of the preforms to one another. Another alternative for bunching is to use straps to hold the preforms together until the chucking process is complete. The strap should be made of a material that can be removed prior to the start of the deposition step or easily baked during the deposition process of the first glass soot layer.

Another aspect of the invention relates to a method of making waveguide fibers from the general form and the novel preforms of certain embodiments described above. Embodiments of the waveguide drawing method from the novel preform include sealing one end of a modified tube surrounding the core preform; And drawing the waveguide fiber from the opposite end. The pores in the modified tubes will be present during the manufacturing phase because they are sealed into the tubes. Unwanted pores and voids between the tubes can be dissipated during the manufacturing step by applying a vacuum to the distal end of the waveguide drawn.

Another embodiment of the method omits the step of sealing one end of the tube surrounding the preform before the drawing step. Altering the cut surface of the tube over its entire length is also omitted. In this embodiment, gas pressure is used for the unsealed tube during the drawing step. Increasing the gas pressure inside the tube does not change or expand the tube opening. Pressure reduction inside the tube reduces or completely seals the opening of the tube during the drawing process. Thus, the density of the waveguide fiber clad layer can change the direction of the axis by changing the gas pressure. The advantage of this embodiment is that the clad density is essential and can be changed continuously from solid glass to glass with a limited maximum porosity, the porosity being dependent only on the number of open tubes and the geometry of the finished waveguide fiber within the clad layer. Together only limited by the minimum wall thickness of the tube. Inert pressure-inducing gases such as nitrogen or helium are preferred. The pores or voids of the unwanted gaps between the tubes depend on the pressure used. Depending on the pore size of the tube relative to the gap pore size, an alternative process is as follows:

All pores collapsed or sealed;

All pores remain open;

The tube pores are closed while the gap pores remain open; or

The gap pores remain closed while the tube pores remain open.

It should be noted that the pressure control allows for the maintenance of the ratio of the species gap pore size to the final tube pore size.

In another embodiment of the method, the preform part is a core preform as described above, the core preform having a clad layer consisting of an array of glass rods arranged around. The arrangement of rods is such that a regular or irregular arrangement of pores is present between or through the rods. By using a vacuum for this preform in the drawing step, the pores between the rods can be changed from a value equal to or less than the original pore cutoff to a minimum cutoff value of 0, thus changing A waveguide having an axial density is manufactured. The same gap change in this cut plane is performed by using gas pressure as used for the open tube described above. Again, the possible density of the cladding layer can be made necessary and constantly varying from the density of the solid glass material to the density of the porous glass material having a porosity limited by the dimension of the preform. The waveguide is made from this. The preform in this example served to close the pores at viscous forces with viscous forces. The pore size can then be varied by changing the pressure used for preforming during the drawing process positively. This is in contrast to the embodiment where the pore size can be changed by changing the pressure negatively.

A particularly useful embodiment of the novel waveguide is that the total dispersion is adjusted from segment to segment of the waveguide. The pre-selected core refractive index profile with a specific pattern of change on the clad layer segment density causes the total dispersion to intersect between positive and negative values. For waveguide fibers with positive total dispersion, short wavelength light travels faster than long wavelength light. The result is that the logarithm of the segment total dispersion over the waveguide fiber total length such as the segment length of the product and the net total dispersion can be equal to the pre-selected target value. For example, the net total dispersion of waveguide fibers can be made to be zero even if the total dispersion of the waveguide is not zero. The novel preforms and other forms of optical waveguides made therefrom are illustrated by the following figures.

Example

Referring to FIG. 3, the waveguide preform silver and the fiber may be prepared as follows. Hexagonal substructures 20 and 22 having openings along the central portion are combined in a cladding layer surrounding core preform 30. The entire combination of concave tubes surrounding the core preform 30 was placed and secured in the tube 28. The details of the illustration represent an infrastructural opening, such as the room 26.

In this embodiment the tubes 20 and 22 have a surface free of indentation. The end of the tube on the FIG. 3 plane is shown unsealed by the embodiment point 26 showing opening.

The tube 28 may settle in this combination before or at the same time as the preform is drawn from the waveguide fibers. In order to ensure proper control of the clad porosity, a pressure above the atmospheric pressure was used in the tube 28 during the drawing step. Starting at atmospheric pressure to a first pressure range and ending at a pressure above pre-determined atmospheric cancer above atmospheric pressure, the infrastructural opening will close due to the activity of viscous forces present during the draw-in phase.

In the second pressure range, first start at a pressure slightly above the highest pressure in the first range pressure and then continue to rise, and there will be an opening in the clad layer after the drawing is finished. The size of the opening is controlled by the degree of pressure used. The pressure used to open the substructure was varied between the first pressure range value and the second pressure range value during the drawing step. Thus, the diameter of the opening varies from zero to a preselected diameter depending on the pressure selected in the second range. The change in pressure used is controlled corresponding to the change in the axis of the cladding layer density or refractive index. That is, the density and average refractive index of the cladding layer are variable along the axial dimension of the waveguide fiber.

Comparative Example 1

Optical waveguide preforms were prepared as described in the above examples except that the ends of the structural tubes were sealed in this comparative example. In addition, the tube was recessed as shown in FIG. 2. Each indentation of the structural tube is present in superimposition with the others on the tube 28. The registration is maintained by the aforementioned tie or other means.

The optical waveguide fibers are drawn from the preform at the opposite end of the sealed end of the infrastructural tube. It may be used in the preform tube 28 at the preform end with a sealed undercarriage tube while being drawn. Thus, for example, modified forms such as sealed and indented tubes have elongated pores and are necessarily arranged in the same pattern as the preformed substructure. The indented portion of the tube is subsequently lowered to form similar clad cuts. The elongated pores have an axis separated from the other by this recessed portion of the clad that has the same cutting plane in succession. The elongated pores are separated from one another on the cutting surface by the side of the substructure. Along with the viscosity drawn on the preform during the drawing process, the vacuum serves to close unwanted gap pores between the infrastructural tubes.

In the embodiment of the preform and waveguide of this comparative example, the core portion of the preform is a combination of a tube having an unfrozen portion and an unsealed end. The viscous force during the drawing process acts to seal the opening on the sealed core tube to produce a rigid glass core with the vacuum used.

Fig. 4 shows the upstream of the waveguide fiber cut surface drawn by the method of the above embodiment. The core region 32 is rigid glass, and the clad region cut surface includes pores 34 in an embodiment that reduces the average refractive index of the clad layer.

It is understood that because the signal waveguide is located in the band gap of the crystal, the size of the pores 34 can be shaped to form light grain crystals that are measured or confine the signal to the core region.

Comparative Example 2

An alternative method is located in a tube whose solid structure is solid and equally large as in Comparative Example 1 above. In this case, however, the substructure is not changed. During the drawing process, the vacuum may be spaced apart in order to leave pores between the substructures, for example, interstitial pores alternately collapse (if vacuum is used) or elongated pores (if vacuum is removed). Is used). The results of this process are shown in FIG. 5 and are drawn from a photograph of the waveguide fiber cladding layer cut surface. The elongated pores 36 present in the cladding layer are sparse between the solid clad glass matrix 38. In the axial direction, the porous portion of the clad is distinguished from the others by the successive similar, non-porous portion of the clad glass.

The effect of the insertion of pores into the cladding layer is illustrated by the two views configured in FIG. 6A shows a cut plane of the nonporous portion of the waveguide fiber. Core or core preform 40 is surrounded by a rigid clad glass layer 42. In FIG. 6B, the core or core preform 44 is surrounded by a porous cladding layer 46. 6A and 6B, 6C and 6D, 6E and 6F, and 6G and 6H correspond to each other and the pairs are drawn from the same preform. The first member of the pairs, i.e., 6a, 6c, 6e, 6g, has a rigid cladding layer while the second member has a porous cladding layer.

The effect of the elongated pores in the porous cladding layer is illustrated by a pair of figures showing the refractive index profile. For example, the stepped index core 48 on FIG. 6C has an index difference relative to the clad layer index 49. FIG. 6C corresponds to the rigid core and clad structure shown in FIG. 6A. In comparison, the index difference between the core index 50 and the porous clad layer average 51 is large as shown in FIG. 6D. The mode power distribution of the signal at one portion of the waveguide by the refractive index profile of FIG. 6C will be broad compared to the distribution of the mode power of the signal propagated in the waveguide region having the refractive index profile of FIG. 6D. It will be appreciated that other properties such as total dispersion, total dispersion slope, cutoff wavelength, zero dispersion wavelength, etc., are also different from other axial portions in the novel waveguide. One suitable structured and drawn preform produces waveguides with such axial changes in waveguide fiber properties. 6C and 6D, 6E and 6F show the relative profile when the core has three segments. The core 52 has a given index profile relative to the clad layer 5. The introduction of the pores into the cladding layer creates a large refractive index difference between the core index 54 and the cladding layer index 56. Again, the relative refractive index differences change the mode power distribution of the signal generated in the waveguide.

The clad index changes in FIGS. 6G and 6H result in a first profile 56 having three distinct annular regions 60, 62 and 64 relative to the clad layer index 57.

In contrast, the core profile 58 relative to the index of the porosity or pore filling the clad layer 59 has only two distinct annular regions 66 and 68.

Potentials associated with the waveguide fibers that cancel out the novel waveguide preform and dispersion are readily illustrated in FIG. 6 (c-h). In addition, adjustment of the mode power distribution provides control of the cutoff wavelength, zero dispersion wavelength, and important waveguide fiber parameters as magnitude and sign of waveguide dispersion, which provides greater fluidity in the use of new waveguides. do.

Although specific embodiments of the invention have been disclosed and described herein, the invention is limited only by the following claims.

Claims (39)

A central core glass having first and second ends, surrounded by a clad glass layer to form an axis shaped preform therebetween; And And a cladding layer comprising a plurality of annular segments extending continuously along the axis, wherein the segments have a pre-selected density that is distinct from the pre-selected density of the segment immediately adjacent to each segment, each segment density Wherein the optical waveguide preforms are higher or lower than both immediately adjacent segments. 2. The optical waveguide preform of claim 1, wherein the segment has a lower pre-selected density than adjacent segments comprising pores. 3. The optical waveguide preform of claim 2, wherein the segment has a higher pre-selected density than adjacent segments comprising pores. 3. The optical waveguide preform of claim 2, wherein the pores have a long dimension extending about an axis of the preform. 4. The optical waveguide preform of claim 3, wherein the pores have a long dimension extending about an axis of the preform. 5. The optical waveguide preform of claim 4, wherein the elongated pores form a regular array. 6. The optical waveguide preform of claim 5, wherein the elongated pores form a regular array. The waveguide fiber of claim 6 or 7, wherein the pitch of the regular array is a waveguide fiber drawn from a pre-selected diameter preform comprising a regular array of elongated pores having a pitch in the range of 0.4 μm to 20 μm. Characterized in an optical waveguide preform. 8. The optical waveguide preform of claim 6 or 7, wherein the elongated pores have a diameter and the ratio of diameter to pitch of the regular array is in the range of 0.1 to 0.9. The method of claim 1, wherein the core glass has a refractive index profile selected from the group consisting of steps, circular steps, trapezoids, circular trapezoids, a-profiles, and segmented profiles, wherein the segments of the segmented profiles are porous layers. Optical waveguide preform, characterized in that it is selected from the group consisting of: step, circular step, trapezoid, annular trapezoid, and a-profile. The dopant of claim 10, wherein the core glass comprises a dopant selected from the group consisting of germania, alumina, phosphorus, titania, boron, and fluorine. An optical waveguide preform comprising a silica glass having. 12. The method of claim 11, wherein the core glass comprises silica doped with a material selected from the group consisting of erbium, ytterbium, neodymium, tulium, and praseodymium. Optical waveguide preforms. The optical waveguide preform of claim 1, wherein the density of the clad layer segments has one of two pre-selected values. The clad glass layer segment of claim 13, wherein the clad glass layer segment having the first value of the two pre-selected densities has a homogeneous first composition, and the clad glass layer segment having the second value of the two pre-selected densities is porous. An optical waveguide preform comprising a first composition. 15. The optical waveguide preform of claim 14, wherein the pores of the clad layer having the second pre-selected density have long dimensions induced along the axis of the preform. 16. The optical waveguide preform of claim 15, wherein the elongated pores form a regular array. 17. The waveguide fiber of claim 16, wherein the pitch of the regular array is waveguide fibers drawn from preforms to have a pre-selected diameter that includes a regular array of elongated pores having a pitch in the range of 0.4 microns to 20 microns. Optical waveguide preforms. The clad glass layer segment of claim 13, wherein the clad glass layer segment having the first value of the two pre-selected densities is a homogeneous first composition having a dielectric constant and the clad glass having the second value of the two pre-selected densities. The layer segment comprises a porous first composition, wherein the pores extend and the long dimension of the pores is oriented along the preform axis, the extended pores are filled with a material having a second dielectric constant, the first and second dielectrics An optical waveguide preform, characterized in that the constant differs by at least three factors. 19. The optical waveguide preform of claim 18, wherein the elongated filled pores form a regular array. 20. The waveguide fiber of claim 19, wherein the pitch of the regular array is a waveguide fiber drawn from the preform to have a pre-selected diameter comprising a regular array of elongated pores having a pitch in the range of 0.4 microns to 20 microns. Optical waveguide preforms. 21. An optical waveguide fiber drawn from the preform of any one of claims 1-7 or 10-20. 21. An optical waveguide fiber drawn from the preform of any one of claims 1-7 or 10-20, wherein the core has a refractive index profile, the segment density is selected to be provided with the core profile, Wherein the total dispersion that varies between positive and negative values depending on the segment density varies between different pre-selected densities, providing a waveguide fiber having a net dispersion equal to the pre-selected value. a) preparing a core preform having a long axis; b) manufacturing a plurality of glass tubes having inner and outer dimensions and long axes; c) forming a reduced number of sections of inner and outer dimensions, N, along the major axis in each of the plurality of glass tubes; And wherein the N reduced dimension sections are spaced apart from each other by a section of the tube, d) aligning the plurality of tubes of step c) in an arrangement surrounding the core preform, wherein the long axis of the core preform is substantially parallel to the long axis of the tube. . The method of claim 23, wherein the tube of step b) has a cut surface selected from the group consisting of circles, triangles, parallelograms, and polygons. 24. The method of claim 23, wherein the arrangement is irregular. 24. The method of claim 23, wherein said arrangement is regular. 24. The method of claim 23, wherein the reduced internal dimension is zero. 24. The method of claim 23 wherein the tube has a first composition and a first dielectric constant, and wherein each section joining the N sections during or before step c) is made of a material having a second composition and a second dielectric constant. Wherein the first dielectric constant is different from the second dielectric constant by at least three factors. 24. The method of claim 23, wherein the tube has a first composition and a first regulation, and wherein the N portions of each section that spatially join the section during or before the step c) have a second composition and a second refractive index. Wherein the first index of refraction is greater than the second index of refraction. The method of claim 23, wherein the method is e) inserting the arrangement of step d) into an outer tube; And f) lowering the outer tube on the array. The method of claim 30, wherein the method further comprises depositing glass soot particles on the outer tube. The method of claim 23, wherein the method is e) bunching the arrangement of tubes so as to remain defined with each other; And f) depositing a glass soot onto said bundle. 33. The method of claim 32, wherein said bunching comprises securing each glass tube and innermost tube to core preforms by means of heating said tubes. 33. The method of claim 32, wherein said bunching comprises fixing each glass tube and innermost tube to a core preform using glass frit. a) preparing a preform by the method of any one of claims 23 to 34; b) sealing one end of the glass tube; c) drawing the waveguide fiber from the opposite preform end of the preform end with the sealed tube; And d) applying a vacuum to the opposite preformed end of the drawn end. a) preparing a core preform; b) manufacturing a plurality of glass rods having a cut surface; c) arranging the plurality of rods in an arrangement surrounding the core preform so as to include the plurality of pores; d) inserting an array of rod and core preforms into the tube to form a draw preform; e) drawing optical waveguide fibers from the drawing preform; And f) applying a varying pressure to the tube in step e). 37. The method of claim 36, wherein the applied pressure varies between atmospheric pressure and pressure below a pre-selected atmospheric pressure. 38. The method of claim 37, wherein the pre-selected pressure is sufficient to at least partially collapse the pores. 38. The method of claim 37, wherein the applied pressure varies between a first pre-selected pressure above atmospheric pressure and a second pre-selected pressure greater than the first pre-selected pressure.