Abstract:
A burner module for delivering a flow of chemical reactants to a combustion site of a chemical vapor deposition process includes a plurality of substantially planar layers. The substantially planar layers are arranged in a generally parallel and fixed relationship and define an inlet, an outlet and a passage fluidly connecting the inlet and outlet. At least one of the layers is a distribution layer having a plurality of apertures therethrough and fluidly communicating with the passage. The plurality of apertures collectively define a non-uniform pattern arranged and configured to improve the uniformity of a flow out through the outlet. Burner adapter and assembly embodiments are also included.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to burner devices, and, more particularly, to burner assemblies, modules and adapters for producing an inorganic soot.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is known to form various articles, such as crucibles, tubing, lenses, and optical waveguides, by reacting a precursor in the flame of a burner to produce a soot and then depositing the soot on a receptor surface. This process is particularly useful for the formation of optical waveguide preforms made from doped and undoped silica soot, including planar waveguides and waveguide fibers.  
           [0003]    The waveguide formation process generally involves reacting a silicon-containing precursor in a burner flame generated by a combustible gas, such as a mixture of methane and oxygen, and depositing the silica soot on an appropriately shaped receptor surface. In this process, silicon-containing materials typically are vaporized at a location remote from the burner. The vaporized raw materials are transported to the burner by a carrier gas. There, they are volatilized and hydrolyzed to produce soot particles. The soot particles then collect on the receptor surface. The receptor surface may be a flat substrate in the case of planar waveguide fabrication, a rotating starting rod (bait tube) in the case of vapor axial deposition (VAD) for waveguide fiber fabrication, or a rotating mandrel in the case of outside vapor deposition (OVD) for waveguide fiber fabrication.  
           [0004]    Numerous burner designs have been developed for use in vapor delivery precursor processes, and at least one liquid delivery precursor process has been contemplated. Whether the precursor is delivered to the burner in vapor form or liquid form, it is important that the burner receives a distributed, even stream of precursor. This consideration is particularly important during waveguide manufacture to form accurate refractive index profiles.  
         SUMMARY OF THE INVENTION  
         [0005]    According to embodiments of the present invention, a burner module for delivering a flow of chemical reactants to a combustion site of a chemical vapor deposition process includes a plurality of substantially planar layers. The burner modules are generally rectangular is shape such that they may be arranged in side-by-side orientation. The substantially planar layers of the burner module are arranged in a generally parallel and fixed relationship and define an inlet, an outlet and a passage fluidly connecting the inlet and the outlet. At least one of the layers is a distribution layer having a plurality of apertures therethrough and fluidly communicating with the passage. The plurality of apertures collectively define a non-uniform pattern arranged and configured to improve the uniformity of a flow out through the outlet.  
           [0006]    According to further embodiments of the present invention, a burner mounting adapter for use with a manifold having a mount surface and first and second fluid supply openings in the mount surface and distributed at different locations along a length of the manifold includes an adapter body. A first inlet aperture, a first outlet aperture and a first connecting passage fluidly connecting the first inlet and outlet apertures are defined in the adapter body. A second inlet aperture, a second outlet aperture and a second connecting passage fluidly connecting the second inlet and outlet apertures are defined in the adapter body. The first and second inlet apertures are arranged and configured to align with the first and second fluid supply openings, respectively, when the burner mounting adapter is mounted on the mount surface of the manifold. The first and second passages extend transversely of the manifold length when the burner mounting adapter is mounted on the mount surface of the manifold. Thus, it should be recognized that the burner mounting adapter connects the macro scale of the manifold to the micro scale of the burner face.  
           [0007]    According to further embodiments of the present invention, a burner module for use with a manifold having a mount surface and first and second fluid supply openings in the mount surface and distributed at different locations along a length of the manifold includes a burner mounting adapter. The burner mounting adapter includes an adapter body. A first inlet aperture, a first outlet aperture and a first connecting passage fluidly connecting the first inlet and outlet apertures are defined in the adapter body. A second inlet aperture, a second outlet aperture and a second connecting passage fluidly connecting the second inlet and outlet apertures are defined in the adapter body. The first and second inlet apertures are arranged and configured to align with the first and second fluid supply openings, respectively, when the burner mounting adapter is mounted on the mount surface of the manifold. The first and second passages extend transversely of the manifold length when the burner mounting adapter is mounted on the mount surface of the manifold. A burner face layer overlies the adapter body and the distribution layers. The burner face layer includes at least first and second burner apertures fluidly communicating with the first and second outlet apertures of the adapter body, respectively.  
           [0008]    According to further embodiments of the present invention, a burner assembly for delivering a flow of chemical reactants to a combustion site of a chemical vapor deposition process includes a manifold and a burner module. The manifold includes a mount surface with first and second fluid supply openings distributed at different locations along a length of the manifold. The burner module includes a burner mounting adapter including an adapter body. A first inlet aperture, a first outlet aperture and a first connecting passage fluidly connecting the first inlet and outlet apertures are defined in the adapter body. A second inlet aperture, a second outlet aperture and a second connecting passage fluidly connecting the second inlet and outlet apertures are defined in the adapter body. The first and second inlet apertures are arranged and configured to align with the first and second fluid supply openings, respectively, when the burner mounting adapter is mounted on the mount surface of the manifold. The first and second passages extend transversely of the manifold length when the burner mounting adapter is mounted on the mount surface of the manifold. A burner face layer overlies the adapter body. The burner face layer includes at least first and second burner apertures fluidly communicating with the first and second outlet apertures of the adapter body, respectively.  
           [0009]    According to further embodiments of the present invention, a burner module for delivering a flow of chemical reactants to a combustion site of a chemical vapor deposition process includes a burner face layer and a reflective layer covering the burner face layer.  
           [0010]    Further features, advantages and details of the present invention will be appreciated by those of ordinary skill in the art from a reading of the Figs. and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a burner assembly according to embodiments of the present invention;  
         [0012]    [0012]FIG. 2 is a partial exploded, perspective view of the burner assembly of FIG. 1;  
         [0013]    [0013]FIG. 3 is a top plan view of the burner assembly of FIG. 1;  
         [0014]    [0014]FIG. 4 is an exploded, perspective view of the burner assembly of FIG. 1;  
         [0015]    [0015]FIG. 5 is a side view of the burner assembly of FIG. 1;  
         [0016]    [0016]FIG. 6 is a top plan view of a manifold forming a part of the burner assembly of FIG. 1;  
         [0017]    [0017]FIG. 7 is a top plan view of a manifold interface adapter layer forming a part of the burner assembly of FIG. 1;  
         [0018]    [0018]FIG. 8 is a top plan view of a convergence adapter layer forming a part of the burner assembly of FIG. 1;  
         [0019]    [0019]FIG. 9 is a top plan view of a burner interface layer forming a part of the burner assembly of FIG. 1;  
         [0020]    [0020]FIG. 10 is a top plan view of an adapter interface layer forming a part of the burner assembly of FIG. 1;  
         [0021]    [0021]FIG. 11 is a top plan view of a plenum layer forming a part of the burner assembly of FIG. 1;  
         [0022]    [0022]FIG. 12 is a top plan view of a distribution layer forming a part of the burner assembly of FIG. 1 with enlarged details;  
         [0023]    [0023]FIG. 13 is a top plan view of a further plenum layer forming a part of the burner assembly of FIG. 1;  
         [0024]    [0024]FIG. 14 is a top plan view of a further distribution layer forming a part of the burner assembly of FIG. 1 with enlarged details;  
         [0025]    [0025]FIG. 15 is a top plan view of a burner face layer forming a part of the burner assembly of FIG. 1;  
         [0026]    [0026]FIG. 16 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  16 - 16  of FIG. 3;  
         [0027]    [0027]FIG. 17 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  17 - 17  of FIG. 5;  
         [0028]    [0028]FIG. 18 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  18 - 18  of FIG. 3;  
         [0029]    [0029]FIG. 19 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  19 - 19  of FIG. 5;  
         [0030]    [0030]FIG. 20 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  20 - 20  of FIG. 3;  
         [0031]    [0031]FIG. 21 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  21 - 21  of FIG. 5;  
         [0032]    [0032]FIG. 22 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  22 - 22  of FIG. 3;  
         [0033]    [0033]FIG. 23 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  23 - 23  of FIG. 5;  
         [0034]    [0034]FIG. 24 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  24 - 24  of FIG. 3;  
         [0035]    [0035]FIG. 25 is a cross-sectional view of the burner assembly of FIG. 1 taken along the line  25 - 25  of FIG. 5;  
         [0036]    [0036]FIG. 26 is a schematic view of a burner system including the burner assembly of FIG. 1;  
         [0037]    [0037]FIG. 27 is a top plan view of a distribution layer according to alternative embodiments of the present invention with enlarged details;  
         [0038]    [0038]FIG. 28 is a top plan view of a distribution layer according to further alternative embodiments of the present invention with enlarged details;  
         [0039]    [0039]FIG. 29 is a top plan view of a distribution layer according to further alternative embodiments of the present invention with enlarged details; and  
         [0040]    [0040]FIG. 30 is a top plan view of a distribution layer according to further alternative embodiments of the present invention with enlarged details.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]    The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
         [0042]    With reference to FIGS.  1 - 5  and  26 , a burner assembly  10  according to preferred embodiments of the present invention is shown therein. The burner assembly  10  includes a block-shaped manifold  100  and a plurality of rectangular-shaped burner modules  50  mounted on the surface of the manifold  100  by means of fasteners (preferably threaded bolts)  40 . Each module  50  includes a mounting adapter  200  and a burner  300 . With reference to FIG. 26, the burner assembly  10  may form a part of a burner system  11  operable to provide a flame  20  which may be used to apply a soot deposit  35  onto a bait rod  30  or other suitable substrate (e.g., a glass core cane). In particular, the burner assembly  10  may be used to form a soot preform  33  which may be subsequently consolidated to form a glass preform, from which an optical waveguide fiber may be drawn.  
         [0043]    Turning to the manifold  100  in greater detail, the manifold  100  is preferably formed from a unitary block of metal (e.g., steel or aluminum), ceramic or other suitable material. However, the manifold  100  may be assembled from multiple discrete members. The manifold  100  has a top face  102  and opposed side faces  104  and  106 . For the purposes of description, the manifold  100  has a lengthwise axis A-A (FIGS. 1 and 3), a lateral axis B-B (see FIGS. 1 and 3), and a vertical axis C-C (see FIG. 5); however, it will be appreciated that the manifold  100  and the burner assembly  10 , although preferable to be mounted as such, may be positioned such that the axis C-C is not vertically oriented. The manifold  100  as illustrated is adapted to hold up to five modules  50 . Many manifolds may be mounted adjacent to each other along the axis A-A such that large soot preforms may be manufactured. As shown in FIG. 2, a pair of opposed, threaded mounting bores  108  are formed in the top face  102  for each module  50 . However, as will be appreciated from the description herein, the manifold  100  may be modified to hold more or fewer of the modules  50 . Additionally, as discussed below, fewer of the modules  50  may be mounted on the manifold  100  than the manifold  100  is adapted to hold.  
         [0044]    As shown in FIGS. 1 and 5, five sets of inlet openings  110 ,  120 ,  130 ,  140 ,  150  are formed in the side face  104  and are distributed along the length of the manifold  100 . The set  110  includes inlet openings  110 A,  110 B,  110 C,  110 D,  110 E spaced apart along the height and distributed along the length of the manifold  100 . Similarly, the sets  120 ,  130 ,  140 , and  150  include inlet openings  120 A- 120 E,  130 A- 130 E,  140 A- 140 E, and  150 A- 150 E, respectively, which are arranged in the same manner as the inlet openings  110 A- 110 E.  
         [0045]    As shown in FIG. 6, five sets of supply openings  112 ,  122 ,  132 ,  142 ,  152  are formed in the top face  102  and are distributed along the length of the manifold  100 . The set  112  includes supply openings  112 A,  112 B,  112 C,  112 D,  112 E spaced apart along the height and distributed along the length of the manifold  100 . Similarly, the sets  122 ,  132 ,  142 , and  152  include supply openings  122 A- 122 E,  132 A- 132 E,  142 A- 142 E, and  152 A- 152 E, respectively, which are arranged in the same manner as the supply openings  112 A- 112 E. The supply openings are preferably spaced apart from between about 5 mm and 19 mm from the adjacent supply openings of the same set. High temperature elastomer O-rings, such as made from Viton, may be provided about each supply opening.  
         [0046]    As shown in FIGS.  16 - 25 , five sets of passages  114 A-E,  124 A-E,  134 A-E,  144 A-E,  154 A-E are formed in the manifold  100  and extend laterally and vertically through the manifold  100  to fluidly connect the sets of inlet openings  110 ,  120 ,  130 ,  140 , and  150  to the sets of supply openings  112 ,  122 ,  132 ,  142 , and  152 , respectively. More particularly, each set of passages includes five passages, each joining one of the inlet openings with a respective one of the supply openings. For example, one set includes passages  114 A,  114 B,  114 C,  114 D, and  114 E connecting the openings  110 A and  112 A, the openings  110 B and  112 B, the openings  110 C and  112 C, the openings  110 D and  112 D, and the openings  110 E and  112 E, respectively. Similarly, the remaining four sets of passages each include five passages  124 A- 124 E,  134 A- 134 E,  144 A- 144 E, and  154 A- 154 E, respectively. In similar fashion to the passages  114 A- 114 E, the passages  124 A- 124 E connect each of the inlet openings  120 A- 120 E to the corresponding supply openings  122 A- 122 E, the passages  134 A- 134 E connect each of the inlet openings  130 A- 130 E to the corresponding supply openings  132 A- 132 E, the passages  144 A- 144 E connect each of the inlet openings  140 A- 140 E to the corresponding supply openings  142 A- 142 E, and the passages  154 A- 154 E connect each of the inlet openings  150 A- 150 E to the corresponding supply openings  152 A- 152 E.  
         [0047]    As best illustrated in FIGS. 1 and 2, the modules  50  may be substantially identically formed. Accordingly, only one of the modules  50  will be described in detail hereinbelow. As noted above, each module  50  includes an adapter  200  and a burner  300 .  
         [0048]    With reference to FIGS. 4 and 7- 9 , the mounting adapter  200  includes a manifold interface adapter layer  210  (FIGS. 4 and 7), a convergence adapter layer  230  (FIGS. 4 and 8), and a burner interface layer  240  (FIGS. 4 and 9). The layers  210 ,  230 ,  240  are stacked as illustrated. In the manufacturing process, the layers  210 ,  230 ,  240  are preferably fused or anodically bonded to one another.  
         [0049]    With reference to FIG. 7, the adapter layer  210  includes apertures  212 A,  212 B,  212 C,  212 D,  212 E and  218  extending fully through its thickness. The layer  210  is preferably between about 2 mm and 4 mm thick. The layer  210  is mounted on the top face  102  of the manifold  100  such that the apertures  212 A,  212 B,  212 C,  212 D,  212 E align with the supply openings  112 A,  112 B,  112 C,  112 D,  112 E (FIG. 6), respectively, to provide fluid communication therethrough. The openings  218  align with the bores  108  and are adapted to receive the bolts  40  therethrough. Preferably, the layer  210  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  210  is formed of PYREX® material manufactured by Corning Incorporated of Corning, N.Y.  
         [0050]    With reference to FIG. 8, the adapter layer  230  of mounting adapter  200  (FIGS. 1, 2) includes laterally extending slots  232 A,  232 B,  232 D,  232 E, an aperture  232 C and apertures  238  extending fully through its thickness. The layer  230  preferably has a thickness of between about 2 mm and 4 mm. The slots  232 A,  232 B,  232 D,  232 E each extend transversely (i.e., along the direction parallel to the lateral axis B-B) along the length of the adapter layer  230 . The layer  230  is mounted on the layer  210  such that the apertures  212 A align and connect with the slots  232 A adjacent the outer ends thereof (see FIG. 16), the apertures  212 B align and connect with the slots  232 B adjacent the outer ends thereof (see FIG. 18), the aperture  212 C aligns and connects with the aperture  232 C (see FIG. 20), the apertures  212 D align and connect with the apertures  232 D adjacent the outer ends thereof (see FIG. 22), and the apertures  212 E align and connect with the apertures  232 E adjacent the outer ends thereof (see FIG. 24). Preferably, the slots  232 A each have a length of between about 14 mm and 15 mm, the slots  232 B each have a length of between about 20 mm and 21 mm, the slots  232 D each have a length of between about 8 mm and 9 mm, and the slots  232 E each have a length of between about 27 mm and 28 mm. Preferably, the layer  230  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  230  is formed of silicon.  
         [0051]    With reference to FIG. 9, the adapter layer  240  includes apertures  242 A,  242 B,  242 C,  242 D,  242 E and  248  extending fully through its thickness. Preferably, the layer  240  has a thickness of between about 2 mm and 4 mm. The layer  240  is mounted on the layer  230  such that the apertures  242 A mate with the slots  232 A adjacent the inner ends thereof (see FIG. 16), the apertures  242 B mate with the slots  232 B adjacent the inner ends thereof (see FIG. 18), the aperture  242 C (see FIG. 20) mates with the aperture  232 C, the apertures  242 D mate with the slots  232 D adjacent the inner ends thereof (see FIG. 22), and the apertures  242 E mate with the slots  232 E adjacent the inner ends thereof (see FIG. 24). The diameters and shapes of the apertures  242 A- 242 E are substantially the same as the diameters and shapes of the apertures  312 A- 312 E discussed below. The apertures  242 A- 242 E may be smaller than and/or differently shaped than the apertures  212 A- 212 E. Preferably, the layer  240  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  240  is formed of PYREX®.  
         [0052]    Turning to the burner  300  in more detail as shown in FIG. 4, the burner  300  includes an adapter interface layer  310 , a plenum layer  320 , a distribution layer  330 , a plenum layer  340 , a distribution layer  350 , a plenum layer  360 , and a burner face layer  370 . The layers  310 ,  320 ,  330 ,  340 ,  350 ,  360 ,  370  are stacked similarly as is illustrated for the adapter  200 . The layers  310 ,  320 ,  330 ,  340 ,  350 ,  360 ,  370  are preferably fused or anodically bonded to one another and to the adapter layer  240 .  
         [0053]    With reference to FIG. 10, the interface layer  310  includes apertures  312 A,  312 B,  312 C,  312 D,  312 E extending fully through the thickness thereof. Preferably, the layer  310  has a thickness of between about 400 microns and 500 microns. The layer  310  is mounted on the adapter layer  240  such that the apertures  312 A,  312 B,  312 C,  312 D,  312 E align and seal with the apertures  240 A,  240 B,  240 C,  240 D,  240 E, respectively, to provide a passage and fluid communication therethrough. Preferably, the layer  310  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  310  is formed of silicon.  
         [0054]    With reference to FIG. 11, the plenum layer  320  includes longitudinally extending slots  322 A,  322 B,  322 C,  322 D,  322 E extending fully through the thickness thereof. Preferably, the thickness of the layer  320  is between about 1 and 5 mm, and more preferably, between about 2 and 4 mm. The layer  320  is mounted to the layer  310  such that the slots  322 A,  322 B,  322 C,  322 D,  322 E mate and align with the apertures  312 A,  312 B,  312 C,  312 D,  312 E, respectively. Preferably, each of the apertures  312 A,  312 B,  312 C,  312 D,  312 E enters the respective slot at locations along each slot  322 A,  322 B,  322 C,  322 D,  322 E. Preferably, each slot  322 A- 322 E has a width (i.e., extending parallel to the lateral axis B-B) of between about 650 and 1000 microns. The lateral distance between adjacent ones of the slots  322 A- 322 E is preferably between about 100 and 1000 microns, and more preferably, between about 350 and 500 microns. Preferably, the layer  320  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  320  is formed of PYREX®.  
         [0055]    With reference to FIG. 12, a first distribution layer  330  includes sets of apertures  332 A,  332 B,  332 C,  332 D,  332 E. Each set of apertures  332 A,  332 B,  332 C,  332 D,  332 E includes a plurality of apertures defining a selected pattern. Each set  332 A,  332 B,  332 C,  332 D,  332 E in this embodiment is preferably substantially identical and includes a uniform array of apertures. The apertures  334 E (forming a part of the set  332 E) and the apertures  334 B (forming a part of the set  332 B) as shown in the enlargement of FIG. 12 are exemplary. Preferably, the apertures of the sets (including the apertures  334 B and  334 E) are circular and each have a diameter of between about 5 and 300 microns, and more preferably, between about 50 and 200 microns. Preferably, adjacent ones of the apertures are spaced apart from one another a distance of between about 75 microns and 80 microns. Preferably, the thickness of the distribution layer  330  is between about 300 and 700 microns, and more preferably, between about 400 and 550 microns. Preferably, the layer  330  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  330  is formed of silicon.  
         [0056]    With reference to FIG. 13, the plenum layer  340  includes longitudinally extending slots  342 A,  342 B,  342 C,  342 D,  342 E extending through the thickness thereof. Preferably, the layer  340  has a thickness of between about 1 and 5 mm, and more preferably, between about 2 and 4 mm. The layer  340  is mounted on the layer  330  such that the slots  342 A,  342 B,  342 C,  342 D,  342 E mate and align with the sets of apertures  332 A,  332 B,  332 C,  332 D,  332 E, respectively. Preferably, all the sets of apertures  332 A,  332 B,  332 C,  332 D,  332 E, empty into the slots  342 A,  342 B,  342 C,  342 D,  342 E in operation. Preferably, each slot  342 A- 342 E has a width of between about 650 and 1000 microns. The lateral distance between adjacent ones of the slots  342 A- 342 E is preferably between about 100 and 1000 microns, and more preferably, between about 350 and 500 microns. Preferably, the layer  340  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  340  is formed of PYREX®.  
         [0057]    With reference to FIG. 14, a second distribution layer  350  includes sets of apertures  352 A,  352 B,  352 C,  352 D,  352 E. Each set of apertures  352 A,  352 B,  352 C,  352 D,  352 E includes a plurality of apertures defining a selected pattern. In this embodiment, each set  352 A,  352 B,  352 C,  352 D,  352 E is preferably substantially identical and includes a uniform array of apertures. The apertures  354 E (forming parts of the set  352 E) and the apertures  354 B (forming parts of the set  352 B) as shown in the enlargements of FIG. 14 are exemplary. Preferably, the apertures of the sets  352 A,  352 B,  352 C,  352 D,  352 E (including the apertures  354 B and  354 E) are preferably circular and each have a diameter of between about 5 and 300 microns, and more preferably, between about 50 and 200 microns. Preferably, the average diameter of the apertures of the distribution layer  350  is less than the average diameter of the apertures of the distribution layer  330 . Preferably, adjacent ones of the apertures of the sets  352 A- 352 E are spaced apart from one another a distance of between about 70 and 80 microns. Preferably, the thickness of the layer  350  is between about 300 and 700 microns, and more preferably, between about 400 and 550 microns. Preferably, the layer  350  is formed of glass, silicon, silicon carbide, borosilicate glass, polycrystalline silica, ceramic, plastic, or photodefinable metal. More preferably, the layer  350  is formed of silicon.  
         [0058]    With reference to FIG. 13, the plenum layer  360  is substantially identical to the layer  340 . The longitudinally extending slots of the layer  360  correspond to the longitudinally extending slots  342 A,  342 B,  342 C,  342 D,  342 E and overlie the sets of apertures  352 A,  352 B,  352 C,  352 D,  352 E, respectively, of the layer  350 .  
         [0059]    With reference to FIG. 15, the burner face layer  370  includes rows  372 A,  372 B,  372 C,  372 D,  372 E of apertures. More particularly, each of the rows  372 A includes a plurality of apertures  374 A, each of the rows  372 B includes a plurality of apertures  374 B, the row  372 C includes a plurality of apertures  372 C, each of the rows  372 D includes a plurality of apertures  374 D, and each of the rows  372 E includes a plurality of apertures  374 E. The apertures  374 A,  374 B,  374 C,  374 D,  374 E are preferably circular as illustrated. Preferably, the diameters of the apertures  374 A,  374 B,  374 C,  374 D,  374 E are in the range of between about 100 and 2000 microns, and more preferably, between about 300 and 1000 microns. The diameters may be different in different rows as is illustrated. According to some embodiments, the diameters of the apertures  374 A- 374 E are smaller than the diameters of apertures of the distribution layers  330 ,  350  along the same flow path. Preferably, adjacent ones of the apertures  374 A,  374 B,  374 C,  374 D,  374 E are spaced apart from adjacent apertures in the same row by a distance of between about 164 and 342 microns. Preferably, the apertures  374 A,  374 B,  374 C,  374 D,  374 E are spaced apart from apertures in adjacent rows by a distance of between about 675 and 750 microns. The burner face layer  370  is mounted on the layer  360  such that the rows  372 A,  372 B,  372 C,  372 D,  372 E overlie the slots of the layer  360  corresponding to the slots  342 A,  342 B,  342 C,  342 D,  342 E, respectively.  
         [0060]    The adapter  200  includes a pair of opposed mounting portions or tabs  202  (see FIGS. 1, 4 and  20 ) extending laterally (i.e., transversely to the length of the manifold  100 ) beyond the burner  300 . The tabs  202  each include portions of the layers  210 ,  230 ,  240  and include the apertures  218 ,  238 ,  248  (FIGS.  7 - 9 ). Preferably, the tabs  202  extend laterally beyond the burner  300  a distance W 3  (FIG. 3) of between about 20 and 30 mm; more preferably between about 25 and 27 mm. The module  50  may be fastened to the top face  102  of the manifold by inserting the bolts  40  through the tabs  202  as illustrated in FIG. 1. In this manner, the tabs  202  provide a secure and convenient means for attaching the module  50  to the top face  102  of the manifold  100 .  
         [0061]    While the adapter  200  and the burner  300  have each been illustrated and described having a certain number of layers, additional layers may be provided. For example, the burner  300  may include additional distribution layers (i.e., formed similarly to the distribution layers  330 ,  350 ) and/or additional plenum layers (i.e., formed similarly to the plenum layers  320 ,  340 ,  360 ). Preferably, any additional distribution layers are alternatingly interleaved with one or more additional plenum layers.  
         [0062]    The passages of the manifold  100  and the slots and apertures of the adapter  200  and the burner  300  provide fluid flow paths (gas or liquid) from the inlet openings (e.g., the openings  110 A,  110 B,  110 C,  110 D,  110 E shown in FIG. 5) to the burner face layers  370  (FIG. 4) of the burner modules  50 . Each of the flow paths is fluidly isolated from the others. The passages and flow paths associated with each of the burner modules  50  and the sets  110 ,  120 ,  130 ,  140 ,  150  are substantially identical except for their locations along the length of the manifold  100 ; accordingly, the passages and flow paths associated with the set  110  and the left endmost burner module  50  (as viewed in FIG. 5) are exemplary and will be described hereinafter.  
         [0063]    With reference to FIG. 26, supplies  70 A,  70 B,  70 C,  70 D,  70 E of burner fluids are fluidly connected to the inlet openings  110 A,  110 B,  110 C,  110 D,  110 E, respectively. The burner fluids may include process materials such as glass precursors, combustion fuels, carriers and facilitators. The burner fluids may be supplied as gases and/or liquids. Each fluid supply may be pressurized by suitable means. For example, one or more of the fluids may be supplied from a pre-pressurized vessel regulated using a regulator and/or a mass flow controller and/or using a pump, bubbler or vaporizer. Preferably, each supply is pressurized at the respective inlet opening  110 A,  110 B,  110 C,  110 D,  110 E to a pressure of between about 10 and 100 psi gage.  
         [0064]    Burner fluid supplies may also be fluidly connected to each of the sets of inlet openings  120 ,  130 ,  140 ,  150  for which a corresponding module  50  is mounted on the manifold  100 . For clarity, these connections are not illustrated in FIG. 26.  
         [0065]    As discussed in more detail below, the fluid supplied to the inlet  110 A will exit the burner assembly  10  from the burner face layer apertures  374 A, the fluid supplied to the inlet  110 B will exit through the apertures  374 B, the fluid supplied to the inlet  110 C will exit through the apertures  374 C, the fluid supplied to the inlet  110 D will exit through the apertures  374 D, and the fluid supplied to the inlet  110 E will exit through the apertures  374 E. The burner fluids preferably include O 2 , N 2 , CH 4 , H 2 , CO, SiCl 4 , GeCl 4 , OMCTS, CF 4 , SF 6 , SiF 4 , POCl 3 , ER(FOD), AlCl 3 , and/or TICS. According to some preferred embodiments, the fluid supplied to the inlet  110 A is a CH 4 /O 2  premix, the fluid supplied to the inlet  110 B is O 2 , the fluid supplied to the inlet  110 C is SiCl 4 , GeCl 4 , and O 2 , the fluid supplied to the inlet  110 D is O 2 , and the fluid supplied to the inlet  110 E is O 2  or, optionally, nothing.  
         [0066]    With reference to FIGS.  7 - 16  and  17 , the fluid supplied to the inlet  110 A flows through the passage  114 A, the supply openings  112 A, the apertures  212 A and into the transverse slots  230 A. The slots  230 A direct the fluid flow inwardly (i.e., convergently) to the apertures  242 A. The fluid flows through the apertures  242 A, through the apertures  312 A and into the longitudinal slots  322 A. The slots  322 A serve as plenums from which the fluid then flows into and through the respective sets of apertures  332 A. The fluid exiting the apertures  332 A then flows into the slots  340 A (which, likewise, serve as plenums), through the respective sets of apertures  252 A and into the longitudinal slots  362 A (which, likewise, serve as plenums). From the slots  362 A, the fluid finally flows out of the burner assembly  10  through respective ones of the rows of apertures  372 A of the burner face layer  370 .  
         [0067]    In the foregoing manner, the flow of the burner fluid introduced at the inlet  110 A may be supplied to the burner face layer  370  without requiring special accommodation. The transverse slots  232 A allow the use of relatively widely spaced apart supply openings  112 A on the top face  102  of the manifold  100  while providing relatively closely spaced burner face apertures  372 A. Accordingly, the openings  112 A may be formed using conventional techniques while nonetheless providing a flame of the desired, relatively narrow width.  
         [0068]    The construction of the burner assembly  10  as well as the configurations of the burner modules  50  may allow for convenient and selective shaping of the profile of the overall soot flame  21  (see FIG. 26). The length of the soot flame  21  may be adjusted by mounting more or fewer of the modules  50  on the manifold  100 . The profile of the flame  21  may also be adjusted by mounting modules  50  of different configurations on the manifold  100 . For example, it may be desirable to provide modules  50  adapted to provide larger flames  20  at the outer ends of the manifold  100  to provide a more uniform flame  21  along the full length of the burner assembly  10 . The bolts  40  and tabs  202  may allow for secure, convenient, non-destructive, repeatable removal and remounting of the modules  50 .  
         [0069]    Moreover, the flow of the burner fluid introduced at the inlet  110 A may be supplied to the burner face layer  370  in an evenly distributed manner. The plenums provided by the longitudinal slots  322 A,  340 A,  360 A and the patterned sets of apertures  332 A,  352 A, as well as the rows of apertures  372 A, serve to equalize the flow of the fluid along the length of the burner module  50  so that the rate and pressure of the flow from the apertures  372 A is more uniform. As a result, a more uniform flame and distribution of glass precursors may be provided.  
         [0070]    With reference to FIGS.  1 - 15 ,  18  and  19 , the pressurized fluid supplied to the inlet  110 B is directed to the rows of apertures  372 B and conditioned or distributed in substantially the same manner as described above with respect to the pressurized fluid supplied to the inlet  110 A. More particularly, the fluid supplied to the inlet  110 B will flow through the passages  114 B, the openings  112 B, the apertures  212 B, the transverse slots  232 B, the apertures  242 B, the apertures  312 B, the longitudinal slots  322 B, the sets of apertures  332 B, the longitudinal slots  342 B, the sets of apertures  352 B, the longitudinal slots of the layer  360  corresponding to the slots  342 B, and the rows of apertures  372 B.  
         [0071]    With reference to FIGS.  7 - 15 ,  20  and  21 , the pressurized fluid supplied to the inlet  110 C is directed to the rows of apertures  372 C and conditioned or distributed in substantially the same manner as described above with respect to the pressurized fluid supplied to the inlet  110 A. More particularly, the fluid supplied to the inlet  110 C will flow through the passage  114 C, the opening  112 C, the aperture  212 C, the aperture  232 C, the aperture  242 C, the aperture  312 C, the longitudinal slot  322 C, the set of apertures  332 C, the longitudinal slot  342 C, the set of apertures  352 C, the longitudinal slot of the layer  360  corresponding to the slot  342 C, and the row of apertures  372 C.  
         [0072]    With reference to FIGS.  7 - 15 ,  22  and  23 , the pressurized fluid supplied to the inlet  110 D is directed to the rows of apertures  372 D and conditioned or distributed in substantially the same manner as described above with respect to the pressurized fluid supplied to the inlet  110 A. More particularly, the fluid supplied to the inlet  110 D will flow through the passages  114 D, the openings  112 D, the apertures  212 D, the transverse slots  232 D, the apertures  242 D, the apertures  312 D, the longitudinal slots  322 D, the sets of apertures  332 D, the longitudinal slots  342 D, the apertures  352 D, the longitudinal slots of the layer  360  corresponding to the slots  342 D, and the rows of apertures  372 D.  
         [0073]    With reference to FIGS.  7 - 15 ,  24  and  25 , the pressurized fluid supplied to the inlet  110 E is directed to the rows of apertures  372 E and conditioned or distributed in substantially the same manner as described above with respect to the pressurized fluid supplied to the inlet  110 A. More particularly, the fluid supplied to the inlet  110 E will flow through the passages  114 E, the openings  112 E, the apertures  212 E, the transverse slots  232 E, the apertures  242 E, the apertures  312 E, the longitudinal slots  322 E, the apertures  332 E, the longitudinal slots  342 E, the sets of apertures  352 E, the longitudinal slots of the layer  360  corresponding to the slots  342 E, and the rows of apertures  372 E.  
         [0074]    Preferably, each of the slots  322 A- 322 E (FIG. 11), the sets of apertures  332 A- 332 E (FIG. 12), the slots  342 A- 342 E (FIG. 13), the sets of apertures  352 A- 352 E (FIG. 14), and the rows of apertures  372 A- 372 E (FIG. 15) has a length of between about 20 and 23 mm.  
         [0075]    Preferably, each of the layers  210 ,  230 ,  240  of the adapter  200  has substantially the same length L (FIG. 3) and width W 1  (FIG. 3). Preferably, the length L is greater than the width W 1 . Preferably, the length L is between about 25 and 26 mm.  
         [0076]    Preferably, each of the layers  310 ,  320 ,  330 ,  340 ,  350 ,  360 ,  370  of the burner  300  (FIG. 4) has substantially the same width and length. Preferably, the length of the burner layers is substantially the same as the length L (FIG. 3) of the adapter  200 . Preferably, the width W 2  (FIG. 3) of the burner layers is between about 50 and 60 mm. Preferably, the apertures formed in the distribution layers  330 ,  350  are formed therein by micromachining. Suitable devices for micromachining such apertures in the layers  330 ,  350  include an Inductively Coupled Plasma Etch Machine, Model Number  601 E, available from ALCATEL.  
         [0077]    Preferably, the manifold  100 , the adapter  200 , and the burner  300  are arranged and configured such that the back pressure present at any given one of the inlets  110 A- 110 E,  120 A- 120 E,  130 A- 130 E,  140 A- 140 E,  150 A- 150 E is no more than 25 psi when a process gas is flowed through the corresponding one of the burner modules  50  and exits through the associated apertures in the burner face layer at a flow rate of 50 slpm (standard liters per minute) of O 2  or less.  
         [0078]    According to certain preferred embodiments of the present invention, the outer surface of the burner face layer  370  may be covered by a reflective layer. The reflective layer may be a thermally deposited oxide layer. Alternatively, the reflective layer may be a metal reflective layer, such as an evaporatively deposited gold layer.  
         [0079]    According to further embodiments of the invention, the patterns of the apertures of the distribution layers may be modified to selectively control the distribution of flow of the burner fluids through the module  50 . For example, either or both of the distribution layers  330 ,  350  of the module  50  may be replaced with modified distribution layers  330 ′ and  350 ′, respectively, as shown in FIG. 27. Each of the sets of apertures  332 A′,  332 B′,  332 D′,  332 E′ of the distribution layers  330 ′,  350 ′ have non-uniform patterns of apertures. For example, the sets  332 B′ have apertures  334 B′ of a first size and apertures  333 B′ of a second, smaller size. Additionally, some of the sets of apertures  332 A′,  332 B′,  332 C′,  332 D′,  332 E′ have different patterns of apertures from one another.  
         [0080]    With reference to FIG. 28, alternative distribution layers  330 ″ and  350 ″ as shown therein may be substituted for the distribution layers  330  and  350 , respectively, of the module  50 . Further alternative distribution layers which may be used in place of the distribution layers  330 ,  340  are shown in FIG. 29 (distribution layers  330 ′″,  350 ′″) and FIG. 30 (distribution layers  330 ″″,  350 ″″).  
         [0081]    The patterns of apertures provided in the distribution layer may be further selected such that one of the distribution layers has at least first and second sets of apertures of a first non-uniform pattern and a second non-uniform pattern, respectively, and another of the distribution layers has third and fourth sets of apertures of third and fourth non-uniform patterns in fluid communication with the first and second sets of apertures, respectively. For example, the distribution layer  330  may be replaced with the distribution layer  330 ′ (FIG. 27) and the distribution layer  350  may be replaced with the distribution layer  350 ″ (FIG. 28). In this case, each of the two non-uniformly patterned set of apertures  332 B′ fluidly communicates with a respective one of the two non-uniformly patterned sets of apertures  352 B″ of the layer  350 ″.  
         [0082]    Moreover, as illustrated by the exemplary embodiment just described, the first and second non-uniform patterns of apertures in a common distribution layer may be different from one another, and the third and fourth non-uniform patterns in a second, common distribution layer may be different from one another. In the described embodiment, the non-uniform patterns of the sets of apertures  332 B′ differ from the non-uniform patterns of the sets of apertures  332 E′ while the non-uniform patterns of the sets of apertures  352 B″ and  352 E″ differ from the patterns of the sets of apertures  332 B″ and  332 E″, respectively. Such non-uniform patterns in the distribution layer(s) help to make the resulting burner flame emanating from the burner face more uniform across the length thereof. This results in more uniform soot generation and deposition.  
         [0083]    The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the invention.