CA2354718A1 - Molded optical fiber ferrule and method of making the same - Google Patents
Molded optical fiber ferrule and method of making the same Download PDFInfo
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- CA2354718A1 CA2354718A1 CA 2354718 CA2354718A CA2354718A1 CA 2354718 A1 CA2354718 A1 CA 2354718A1 CA 2354718 CA2354718 CA 2354718 CA 2354718 A CA2354718 A CA 2354718A CA 2354718 A1 CA2354718 A1 CA 2354718A1
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Abstract
This invention provides a fiber optic ferrule and method of forming the same.
The method comprises the steps of: method of forming an optical fiber ferrule on an optical fiber, comprising the steps of: (a)providing a mold, said mold having a cavity; (b) positioning at least one optical fiber to extend through said mold cavity; (c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said filler material contained in said mold cavity with electromagnetic radiation selected to match the electromagnetic radiation absorption characteristics of the material to form a solid ferrule containing said at least one optical fiber.
The method comprises the steps of: method of forming an optical fiber ferrule on an optical fiber, comprising the steps of: (a)providing a mold, said mold having a cavity; (b) positioning at least one optical fiber to extend through said mold cavity; (c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said filler material contained in said mold cavity with electromagnetic radiation selected to match the electromagnetic radiation absorption characteristics of the material to form a solid ferrule containing said at least one optical fiber.
Description
~
itl : MOLDED OPTICAL FIBER FERRULE AND METHOD OF MAKING THE
SAME
The present invention relates to an optical fiber ferrule and a method of forming the same.
BACKGROUND OF THE INVENTION
Fiberoptic cable and components are fast becoming the backbone of the Internet and telecommunications industries. The individual fibers making up these fiberoptic systems are terminated using a connector, pigtail or other component. A pigtail assembly comprises a short length of optical fiber permanently fixed to a component and used to couple power between it and a transmission fiber. Typically, where the fiber pigtail is aligned and attached to a component (such as a wavelength division multiplexer or WDM, dense wavelength division multiplexer or DWDM, switch, filter, laser diode, attenuator, arrayed waveguide, etc.) the fiber is first encapsulated in a glass, ceramic, or metal ferrule or microcapillary. This is done because handling, aligning and adhering stripped fiber is extremely difficult, due to the fact that such stripped fiber may have an outside diameter of approximately 125 microns or less. The addition of a ferrule permits the manufacturer to handle the fiber in a larger protected package.
Packaging the fiber into ferrules is a time consuming task that involves the joining of at least three materials: optical fiber, ferrule, and an adhesive. Typically, first, a very small volume of adhesive is placed at the open end of the ferrule. The adhesive then migrates into the inner channel of the ferrule by capillary effect. The fiber, stripped of its coating, is then inserted through the ferrule. The adhesive is then cured by heat or ultraviolet light (UV). Heat cured epoxies generally require 5 minutes or more in some sort of heating apparatus whereas UV cured materials can be cured in less than a minute by exposure to UV radiation. The next step is to cleave off the excess fiber extending from the end of the ferrule and then polishing the end of the completed assembly to an optical grade finish. For example, U.S. Patent No. 5,815,621 which issued to Sakai et al. shows how a ferrule can be adhesively assembled onto an end of a optical fiber.
There are also a number of prior art references which disclose molding optical fiber ferrules in situ, directly onto an optical fiber, including U.S. Patent No. 4,026,972 issued to Philips et al, U.S. Patent No. 4,292,260.
issued to Cheung; U.S. Patent No. 4,722,584 issued to Kakii et al., and U.S.
Patent No. 5,568,581 issued to Johnson et al. Each of these patents disclose conventional forms of molding, including injection molding, and filling a cavity with an epoxy resin or similar potting compound.
While prior art methods of forming fiber optic ferrules are effective for their intended purpose, the time and cost of forming ferrules using such conventional methods can be prohibitively high. Therefore, what is needed is a way to decrease the time and cost necessary for forming a fiber optic ferrule.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical fiber ferrule and a method of forming such a structure.
In an aspect of the present invention, there is provided a method of forming a ferrule on an optical fiber, comprising the steps of:
(a) providing a mold, said mold having a cavity;
(b) positioning at least one optical fiber to extend, through said mold cavity;
(c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said ~Iler material contained in said mold cavity with electromagnetic radiation of suitable wavelength to form a solid ferrule containing said at least one optical fiber.
In yet another aspect the present invention involves a use of flowable, electromagnetic radiation curable filler material for forming in situ, an optical fiber ferrule, said flowable, electromagnetic radiation curable filler ~
itl : MOLDED OPTICAL FIBER FERRULE AND METHOD OF MAKING THE
SAME
The present invention relates to an optical fiber ferrule and a method of forming the same.
BACKGROUND OF THE INVENTION
Fiberoptic cable and components are fast becoming the backbone of the Internet and telecommunications industries. The individual fibers making up these fiberoptic systems are terminated using a connector, pigtail or other component. A pigtail assembly comprises a short length of optical fiber permanently fixed to a component and used to couple power between it and a transmission fiber. Typically, where the fiber pigtail is aligned and attached to a component (such as a wavelength division multiplexer or WDM, dense wavelength division multiplexer or DWDM, switch, filter, laser diode, attenuator, arrayed waveguide, etc.) the fiber is first encapsulated in a glass, ceramic, or metal ferrule or microcapillary. This is done because handling, aligning and adhering stripped fiber is extremely difficult, due to the fact that such stripped fiber may have an outside diameter of approximately 125 microns or less. The addition of a ferrule permits the manufacturer to handle the fiber in a larger protected package.
Packaging the fiber into ferrules is a time consuming task that involves the joining of at least three materials: optical fiber, ferrule, and an adhesive. Typically, first, a very small volume of adhesive is placed at the open end of the ferrule. The adhesive then migrates into the inner channel of the ferrule by capillary effect. The fiber, stripped of its coating, is then inserted through the ferrule. The adhesive is then cured by heat or ultraviolet light (UV). Heat cured epoxies generally require 5 minutes or more in some sort of heating apparatus whereas UV cured materials can be cured in less than a minute by exposure to UV radiation. The next step is to cleave off the excess fiber extending from the end of the ferrule and then polishing the end of the completed assembly to an optical grade finish. For example, U.S. Patent No. 5,815,621 which issued to Sakai et al. shows how a ferrule can be adhesively assembled onto an end of a optical fiber.
There are also a number of prior art references which disclose molding optical fiber ferrules in situ, directly onto an optical fiber, including U.S. Patent No. 4,026,972 issued to Philips et al, U.S. Patent No. 4,292,260.
issued to Cheung; U.S. Patent No. 4,722,584 issued to Kakii et al., and U.S.
Patent No. 5,568,581 issued to Johnson et al. Each of these patents disclose conventional forms of molding, including injection molding, and filling a cavity with an epoxy resin or similar potting compound.
While prior art methods of forming fiber optic ferrules are effective for their intended purpose, the time and cost of forming ferrules using such conventional methods can be prohibitively high. Therefore, what is needed is a way to decrease the time and cost necessary for forming a fiber optic ferrule.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical fiber ferrule and a method of forming such a structure.
In an aspect of the present invention, there is provided a method of forming a ferrule on an optical fiber, comprising the steps of:
(a) providing a mold, said mold having a cavity;
(b) positioning at least one optical fiber to extend, through said mold cavity;
(c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said ~Iler material contained in said mold cavity with electromagnetic radiation of suitable wavelength to form a solid ferrule containing said at least one optical fiber.
In yet another aspect the present invention involves a use of flowable, electromagnetic radiation curable filler material for forming in situ, an optical fiber ferrule, said flowable, electromagnetic radiation curable filler ~
material being placed into an open mold cavity along with at least one optical fiber which extends through said cavity, said filler material being subjected to electromagnetic radiation of suitable wavelength to cure said filler material to form a ferrule surrounding said at least one optical fiber.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show a preferred embodiment of the present invention and in which:
Figure 1 shows a fiberoptic pigtail assembly in accordance with prior art:
Figures 2a shows a top view of a prior art ferrule;
Figure 2b shows a cross sectional view of the prior art ferrule of Figure 2a;
Figure 3a shows a top view of a mold for forming an optical fiber ferrule in accordance with one embodiment of the present invention;
Figure 3b shows a side cross sectional view of the mold of Figure 3a;
Figure 3c shows a side cross sectional view of an alternative embodiment of the mold with a separate mold tip;
Figure 4 shows a schematic of a molding process in accordance with one embodiment of the present invention;
Figure 5 shows a completed optical fiber ferrule formed by the process shown in Figure 4;
Figures 6a-6c show alternative embodiments of the present invention including a sleeve;
Figures 7a and 7b show a preferred embodiment of the sleeve of Figures 6a-6c;
Figure 8 shows another completed optical fiber ferrule with backfill material at the connector/optical fiber juncture to provide strain relief;
and ~
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show a preferred embodiment of the present invention and in which:
Figure 1 shows a fiberoptic pigtail assembly in accordance with prior art:
Figures 2a shows a top view of a prior art ferrule;
Figure 2b shows a cross sectional view of the prior art ferrule of Figure 2a;
Figure 3a shows a top view of a mold for forming an optical fiber ferrule in accordance with one embodiment of the present invention;
Figure 3b shows a side cross sectional view of the mold of Figure 3a;
Figure 3c shows a side cross sectional view of an alternative embodiment of the mold with a separate mold tip;
Figure 4 shows a schematic of a molding process in accordance with one embodiment of the present invention;
Figure 5 shows a completed optical fiber ferrule formed by the process shown in Figure 4;
Figures 6a-6c show alternative embodiments of the present invention including a sleeve;
Figures 7a and 7b show a preferred embodiment of the sleeve of Figures 6a-6c;
Figure 8 shows another completed optical fiber ferrule with backfill material at the connector/optical fiber juncture to provide strain relief;
and ~
Figures 9a-9j show top views of mold cavities having various physical shapes and configurations for forming optical fiber ferrules containing one or more optical fibers in accordance with various embodiments of the present invention.
Referring to Figure 1, in accordance with the prior art, a pigtail or a short length of optical fiber 10 (comprising an outer buffer layer 13, an inner cladding layer 11, and a core 18) is shown for connection to a component 12, such as a wavelength division multiplexer (WDM), dense wavelength dimension multiplexer (DWDM), switch, filter, laser diode, attenuator, arrayed waveguide, etc. Typically, where the optical fiber 10 is aligned and attached to the component 12, the optical fiber 10 is first fitted into a ferrule 14. This is done because handling, aligning and adhering the optical fiber 10 to form a connection is extremely difficult, especially when the buffer layer 13 on the optical fiber 10 is stripped away, since the inner cladding layer 1.1 may have an outside diameter of only about 125 microns.
The addition of a ferrule 14 permits easier handling of the optical fiber 10.
Referring now to Figures 2a and 2b, an example of a prior art ferrule 14 is shown in top view and in a side cross-sectional view, respectively. The ferrule 14 has a bore 16 so that a stripped optical fiber 10 (i.e. with the buffer layer 13 stripped off so that the inner cladding layer 11 is exposed) can be threaded through the ferrule bore 16. The optical fiber 10 and the stripped portion is typically bonded to the ferrule 14 using an adhesive (not shown). The adhesive is cured to form a bond after the optical fiber 10 is inserted into the ferrule 14. The ferrule 14 is typically formed of glass, ceramic, metal, or plastic. As explained above, the process of assembling the ferrule 14 onto an optical fiber 10 with an adhesive can be a time consuming task.
Now referring to Figures 3a and 3b, there is shown a mold 20 for forming an optical fiber ferrule in accordance with the present invention.
Figure 3a shows a top view of the mold 20. The mold 20 has a cavity 23 with an opening 22 at the bottom of the cavity 23. The opening 22 is appropriately sized to allow a stripped optical fiber 10 (i.e. stripped down to the cladding layer 11 ) to pass through. Advantageously, the mold cavity 23 includes a conical portion 25 which may assist in directing the stripped portion into opening 22.
Still referring to Figures 3a and 3b, preferably, the mold 20 is open at the top. Preferably, when viewed from the top as in Figure 3a, the top opening 27 is not smaller than the cross-sectional area of the mold cavity 23 at any point along the mold 20. Advantageously, this will allow the finished optical ferrule to be released axially from the mold 20 so that the mold 20 need not be split apart or separated into pieces.
Now referring to Figure 3c, in an alternative embodiment of the present invention, the conical portion 25 of the mold 20 can be formed separately from the remainder of the mold so that it can be used to push out a completed ferrule from the mold 20.
Figure 4 shows a schematic of the mold 20 filled with a filler material 24. Prior to filling, however, an end of an optical fiber 10 is stripped down to its cladding layer 11 and placed to extend through the opening 22 at the bottom of the mold 20. To properly position the fiber 10 within the mold 20 (typically parallel with the axis of the mold), a gripping and tensioning device 28, 30 is used to grip the optical fiber 10 and the stripped portion, respectively, on either side of the mold 20 and to provide sufficient tension to straighten out the length of the optical fiber 10 and to locate and maintain the optical fiber 10 and its stripped portion relative to the mold 20. In this embodiment the fiber 10 is placed within mold 20 before the filler material 24.
In an alternative embodiment, the mold 20 may first be filled with a filler material 24 and the optical fiber 10 may be subsequently inserted into the mold 20 and the filler material 24 before the filler material 24 is cured. In this alternative embodiment, the gripping and tensioning device 28, 30 may be applied after the optical fiber 10 (i.e. the stripped down portion) is threaded through the opening 22 of the mold 20. In this ~
Referring to Figure 1, in accordance with the prior art, a pigtail or a short length of optical fiber 10 (comprising an outer buffer layer 13, an inner cladding layer 11, and a core 18) is shown for connection to a component 12, such as a wavelength division multiplexer (WDM), dense wavelength dimension multiplexer (DWDM), switch, filter, laser diode, attenuator, arrayed waveguide, etc. Typically, where the optical fiber 10 is aligned and attached to the component 12, the optical fiber 10 is first fitted into a ferrule 14. This is done because handling, aligning and adhering the optical fiber 10 to form a connection is extremely difficult, especially when the buffer layer 13 on the optical fiber 10 is stripped away, since the inner cladding layer 1.1 may have an outside diameter of only about 125 microns.
The addition of a ferrule 14 permits easier handling of the optical fiber 10.
Referring now to Figures 2a and 2b, an example of a prior art ferrule 14 is shown in top view and in a side cross-sectional view, respectively. The ferrule 14 has a bore 16 so that a stripped optical fiber 10 (i.e. with the buffer layer 13 stripped off so that the inner cladding layer 11 is exposed) can be threaded through the ferrule bore 16. The optical fiber 10 and the stripped portion is typically bonded to the ferrule 14 using an adhesive (not shown). The adhesive is cured to form a bond after the optical fiber 10 is inserted into the ferrule 14. The ferrule 14 is typically formed of glass, ceramic, metal, or plastic. As explained above, the process of assembling the ferrule 14 onto an optical fiber 10 with an adhesive can be a time consuming task.
Now referring to Figures 3a and 3b, there is shown a mold 20 for forming an optical fiber ferrule in accordance with the present invention.
Figure 3a shows a top view of the mold 20. The mold 20 has a cavity 23 with an opening 22 at the bottom of the cavity 23. The opening 22 is appropriately sized to allow a stripped optical fiber 10 (i.e. stripped down to the cladding layer 11 ) to pass through. Advantageously, the mold cavity 23 includes a conical portion 25 which may assist in directing the stripped portion into opening 22.
Still referring to Figures 3a and 3b, preferably, the mold 20 is open at the top. Preferably, when viewed from the top as in Figure 3a, the top opening 27 is not smaller than the cross-sectional area of the mold cavity 23 at any point along the mold 20. Advantageously, this will allow the finished optical ferrule to be released axially from the mold 20 so that the mold 20 need not be split apart or separated into pieces.
Now referring to Figure 3c, in an alternative embodiment of the present invention, the conical portion 25 of the mold 20 can be formed separately from the remainder of the mold so that it can be used to push out a completed ferrule from the mold 20.
Figure 4 shows a schematic of the mold 20 filled with a filler material 24. Prior to filling, however, an end of an optical fiber 10 is stripped down to its cladding layer 11 and placed to extend through the opening 22 at the bottom of the mold 20. To properly position the fiber 10 within the mold 20 (typically parallel with the axis of the mold), a gripping and tensioning device 28, 30 is used to grip the optical fiber 10 and the stripped portion, respectively, on either side of the mold 20 and to provide sufficient tension to straighten out the length of the optical fiber 10 and to locate and maintain the optical fiber 10 and its stripped portion relative to the mold 20. In this embodiment the fiber 10 is placed within mold 20 before the filler material 24.
In an alternative embodiment, the mold 20 may first be filled with a filler material 24 and the optical fiber 10 may be subsequently inserted into the mold 20 and the filler material 24 before the filler material 24 is cured. In this alternative embodiment, the gripping and tensioning device 28, 30 may be applied after the optical fiber 10 (i.e. the stripped down portion) is threaded through the opening 22 of the mold 20. In this ~
alternative method, the stripped down portion of the optical fiber 10 should have sufficient rigidity so that it may be pushed through the uncured filler material.
It will be appreciated that the gripping and tensioning device 28, 30 could also be used to fix fiber axial orientation. That is, during the gripping and tensioning process as described above, one or more fibers could be individually, axially oriented by turning the fiber by manual or automatic means prior to fixing the fibers in place during the curing process.
Once the fiber core 18 is properly positioned, filler material 24 is dispensed into the cavity 23 of the mold 20 by means of a dispenser 26.
The filler material 24 is preferably easily flowable to allow for good structure formation upon curing. Advantageously, the flowable filler material does not require any pressure to evenly and completely fill the mold cavity 23 as, for example, would be required in injection molding or other similar pressure molding processes.
By way of example, and not by way of limitation, the filler material 24 may be acrylate, epoxy, other thermoset material, or thermoplastic. The filler material 24 when cured may have a coefficient of thermal expansion similar to borosilicate glass over -40°C to 85°C. The cured filler material 24 preferably also has a Tg (transition glass) of over 85°C and has high moisture resistance, high chemical durability, and virtually no out gassing.
Once the mold 20 has been filled with filler material 24, and the fiber 10 is located as desired, the filler material 24 may be cured or polymerized to form a solid structure. Curing may be accomplished by exposure to electromagnetic radiation including UV, visible, near-infrared, mid-infrared, far-infrared, or any combination. The wavelengths will be determined by the absorption characteristics of the chosen filler material.
As for the mold 20 itself, the design of the surface dimensions of the mold cavity 23 will reflect the physical dimensions of the required finished part. Also, the mold 20 may preferably have some transparency or conductivity to the energy needed to cure the filler material 24. For example, where electromagnetic radiation is being used to cure the filler material 24, the electromagnetic radiation preferably may be partially transmitted through a transparent or translucent mold 20. The material used to form the mold 20 could be some type of glass or plastic, for example. The mold 20 could also be contained within a stronger housing such as conventional tooling .
steel or aluminum to provide additional physical strength, in which case the electromagnetic radiation can be directed through the top opening 27 or through the transmissive cone.
Now referring to Figure 5, after the filler material 24 has been cured by exposure to an energy source as previously described, the cured, solid ferrule 24a, 24b can be removed from the mold 20. Any excess fiber portion extending from the solid ferrule structure 24a, 24b is then cleaved off and the conical end portion 24b of the ferrule is ground and polished to a smooth flat surface and may have an optical grade finish.
Now referring to Figures 6a and 6b, there is shown another embodiment of the present invention in which a sleeve 40 is used. Figure 6a shows a modified mold 20 which has a ledge 21 formed at the juncture of the main cavity 23 and the conical portion 25. The ledge 21 provides a surface on which a sleeve 40 can be placed prior to inserting an optical cable 10 and filling the cavity 23. When a sleeve 40 is used the electromagnetic radiation to cure the curable filler material 24 is directed into the material from the top and/or bottom unless the sleeve is itself transparent to the wave length used. Figure 6b shows a completed optical fiber ferrule now encased by a sleeve 40. As described above, portion 24b of the ferrule formed by conical portion 25 may then be removed by grinding and polishing. In order to facilitate grinding down to a flat surface, the ledge 21 may be formed slightly away from the juncture and the conical portion 25 so that a standoff 21 a is formed (Figure 6c).
Now referring to Figures 7a and 7b, a preferred embodiment of a sleeve 40a is shown for use in connection with the process described with reference to Figures 6a and 6b. Extending from the sleeve 40a at either end of the sleeve 40a are a plurality of flanges 42. These flanges may be formed, for example, by cutting out appropriate portions of the sleeve 40a.
Advantageously, the cured material will extend into the gaps 43 so that sleeve 40a is better secured in position.
Figure 8 shows another completed optical fiber ferrule formed in accordance with the present invention in which backfill material 44 has been added at the connector/optical fiber juncture to provide strain relief and additional structural support.
In yet another alternative embodiment, a sleeve 40 can be shaped to form a container with a conical portion corresponding to the conical portion 25 of the mold. Such a sleeve/container may contain the filler material 24 without the need for a separate mold 20. In this embodiment, the container acts as the sleeve and the mold at the same time and becomes part of the finished ferrule. Thus, there is no removal of the finished product from a mold 20.
The conical portion of such a container may be formed from a soft plastic material or the like which can be ground and polished as necessary. To facilitate curing by electromagnetic radiation, it will be appreciated that such a sleeve/container may be transparent or translucent.
Alternatively, just the conical portion may be formed from a transparent or translucent soft plastic material and the remainder of the container may be formed from stronger material such as metal. In such a case, the conical portion may be formed separately and dropped into the sleeve so as to form a sleeve/container into which filler material 24 can be placed..
A process has been described above for forming an optical fiber ferrule for a single optical fiber 10. However, it will be appreciated by those skilled in the art that the process can be adopted to deal with a plurality of optical fibers simultaneously. For example, if the component 12 (Figure 1) to which connection will be made is based upon silicon bench technology, such as a waveguide chip or arrayed waveguide, it may be necessary to attach a plurality of optical fibers to the device. This is known in the fiberoptic industry as array/fiber attachment.
Now referring to Figures 9a-9j, instead of a single cylindrical type of mold 20 used for a single fiber (Figures 3a and 3b), the mold cavity 23 could be square, rectangular, hexagonal, etc. Figure 9a shows a mold cavity 23 for a single optical fiber which has a flat surface on an otherwise cylindrical shape. Figure 9b shows how two of the mold cavities shown in Figure 9a may be placed against each other. Similarly, Figure 9c demonstrates how a plurality of ferrules separately formed in individual molds of hexagonal shape can be tightly packed together. Figures 9d and 9e show examples of how two square or rectangular shaped ferrules can be placed adjacent each other.
As shown in Figures 9f-9h, a single mold 23 may also be fashioned to form a ferrule containing a plurality of optical fibers 10. The arrangement may be a linear array as shown in Figure 9f, a circular array as shown in Figure 9g, a square array configuration as shown in Figure 9h, or virtually any other shape.
Figure 9i shows that the optical fiber ferrule formed in accordance with the present invention can be in virtually any shape. As explained earlier, in reference to Figures 3a and 3b, as long as the ferrule can be released from the mold 23 virtually any shape can be obtained.
Finally, Figure 9j shows an optical fiber ferrule formed in accordance with the present invention which contains a plurality of optical fibers bundled closely together along its axis.
While the concept has been described with reference to an example, it will be appreciated by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the following claims all of such changes and modifications that are within the scope of this invention.
It will be appreciated that the gripping and tensioning device 28, 30 could also be used to fix fiber axial orientation. That is, during the gripping and tensioning process as described above, one or more fibers could be individually, axially oriented by turning the fiber by manual or automatic means prior to fixing the fibers in place during the curing process.
Once the fiber core 18 is properly positioned, filler material 24 is dispensed into the cavity 23 of the mold 20 by means of a dispenser 26.
The filler material 24 is preferably easily flowable to allow for good structure formation upon curing. Advantageously, the flowable filler material does not require any pressure to evenly and completely fill the mold cavity 23 as, for example, would be required in injection molding or other similar pressure molding processes.
By way of example, and not by way of limitation, the filler material 24 may be acrylate, epoxy, other thermoset material, or thermoplastic. The filler material 24 when cured may have a coefficient of thermal expansion similar to borosilicate glass over -40°C to 85°C. The cured filler material 24 preferably also has a Tg (transition glass) of over 85°C and has high moisture resistance, high chemical durability, and virtually no out gassing.
Once the mold 20 has been filled with filler material 24, and the fiber 10 is located as desired, the filler material 24 may be cured or polymerized to form a solid structure. Curing may be accomplished by exposure to electromagnetic radiation including UV, visible, near-infrared, mid-infrared, far-infrared, or any combination. The wavelengths will be determined by the absorption characteristics of the chosen filler material.
As for the mold 20 itself, the design of the surface dimensions of the mold cavity 23 will reflect the physical dimensions of the required finished part. Also, the mold 20 may preferably have some transparency or conductivity to the energy needed to cure the filler material 24. For example, where electromagnetic radiation is being used to cure the filler material 24, the electromagnetic radiation preferably may be partially transmitted through a transparent or translucent mold 20. The material used to form the mold 20 could be some type of glass or plastic, for example. The mold 20 could also be contained within a stronger housing such as conventional tooling .
steel or aluminum to provide additional physical strength, in which case the electromagnetic radiation can be directed through the top opening 27 or through the transmissive cone.
Now referring to Figure 5, after the filler material 24 has been cured by exposure to an energy source as previously described, the cured, solid ferrule 24a, 24b can be removed from the mold 20. Any excess fiber portion extending from the solid ferrule structure 24a, 24b is then cleaved off and the conical end portion 24b of the ferrule is ground and polished to a smooth flat surface and may have an optical grade finish.
Now referring to Figures 6a and 6b, there is shown another embodiment of the present invention in which a sleeve 40 is used. Figure 6a shows a modified mold 20 which has a ledge 21 formed at the juncture of the main cavity 23 and the conical portion 25. The ledge 21 provides a surface on which a sleeve 40 can be placed prior to inserting an optical cable 10 and filling the cavity 23. When a sleeve 40 is used the electromagnetic radiation to cure the curable filler material 24 is directed into the material from the top and/or bottom unless the sleeve is itself transparent to the wave length used. Figure 6b shows a completed optical fiber ferrule now encased by a sleeve 40. As described above, portion 24b of the ferrule formed by conical portion 25 may then be removed by grinding and polishing. In order to facilitate grinding down to a flat surface, the ledge 21 may be formed slightly away from the juncture and the conical portion 25 so that a standoff 21 a is formed (Figure 6c).
Now referring to Figures 7a and 7b, a preferred embodiment of a sleeve 40a is shown for use in connection with the process described with reference to Figures 6a and 6b. Extending from the sleeve 40a at either end of the sleeve 40a are a plurality of flanges 42. These flanges may be formed, for example, by cutting out appropriate portions of the sleeve 40a.
Advantageously, the cured material will extend into the gaps 43 so that sleeve 40a is better secured in position.
Figure 8 shows another completed optical fiber ferrule formed in accordance with the present invention in which backfill material 44 has been added at the connector/optical fiber juncture to provide strain relief and additional structural support.
In yet another alternative embodiment, a sleeve 40 can be shaped to form a container with a conical portion corresponding to the conical portion 25 of the mold. Such a sleeve/container may contain the filler material 24 without the need for a separate mold 20. In this embodiment, the container acts as the sleeve and the mold at the same time and becomes part of the finished ferrule. Thus, there is no removal of the finished product from a mold 20.
The conical portion of such a container may be formed from a soft plastic material or the like which can be ground and polished as necessary. To facilitate curing by electromagnetic radiation, it will be appreciated that such a sleeve/container may be transparent or translucent.
Alternatively, just the conical portion may be formed from a transparent or translucent soft plastic material and the remainder of the container may be formed from stronger material such as metal. In such a case, the conical portion may be formed separately and dropped into the sleeve so as to form a sleeve/container into which filler material 24 can be placed..
A process has been described above for forming an optical fiber ferrule for a single optical fiber 10. However, it will be appreciated by those skilled in the art that the process can be adopted to deal with a plurality of optical fibers simultaneously. For example, if the component 12 (Figure 1) to which connection will be made is based upon silicon bench technology, such as a waveguide chip or arrayed waveguide, it may be necessary to attach a plurality of optical fibers to the device. This is known in the fiberoptic industry as array/fiber attachment.
Now referring to Figures 9a-9j, instead of a single cylindrical type of mold 20 used for a single fiber (Figures 3a and 3b), the mold cavity 23 could be square, rectangular, hexagonal, etc. Figure 9a shows a mold cavity 23 for a single optical fiber which has a flat surface on an otherwise cylindrical shape. Figure 9b shows how two of the mold cavities shown in Figure 9a may be placed against each other. Similarly, Figure 9c demonstrates how a plurality of ferrules separately formed in individual molds of hexagonal shape can be tightly packed together. Figures 9d and 9e show examples of how two square or rectangular shaped ferrules can be placed adjacent each other.
As shown in Figures 9f-9h, a single mold 23 may also be fashioned to form a ferrule containing a plurality of optical fibers 10. The arrangement may be a linear array as shown in Figure 9f, a circular array as shown in Figure 9g, a square array configuration as shown in Figure 9h, or virtually any other shape.
Figure 9i shows that the optical fiber ferrule formed in accordance with the present invention can be in virtually any shape. As explained earlier, in reference to Figures 3a and 3b, as long as the ferrule can be released from the mold 23 virtually any shape can be obtained.
Finally, Figure 9j shows an optical fiber ferrule formed in accordance with the present invention which contains a plurality of optical fibers bundled closely together along its axis.
While the concept has been described with reference to an example, it will be appreciated by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the following claims all of such changes and modifications that are within the scope of this invention.
Claims (11)
1. A method of forming an optical fiber ferrule on an optical fiber, comprising the steps of:
(a) providing a mold, said mold having a cavity;
(b) positioning at least one optical fiber to extend through said mold cavity;
(c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said filler material contained in said mold cavity with electromagnetic radiation selected to match the electromagnetic radiation absorption characteristics of the material to form a solid ferrule containing said at least one optical fiber.
(a) providing a mold, said mold having a cavity;
(b) positioning at least one optical fiber to extend through said mold cavity;
(c) placing a flowable electromagnetic radiation curable filler material into said mold cavity; and (d) curing said filler material contained in said mold cavity with electromagnetic radiation selected to match the electromagnetic radiation absorption characteristics of the material to form a solid ferrule containing said at least one optical fiber.
2. The method of claim 1, wherein said mold has an open end and is held with said open end up, so as to contain said flowable filler material.
3. The method of claim 2, wherein said solid ferrule is released from said mold by moving said mold axially away from said optical fiber.
4. The method of claim 1, wherein, process further comprises gripping and tensioning said optical fiber to maintain a desired position within the mold cavity.
5. The method of claim 4, wherein, said process further comprises orienting said optical fiber to maintain a desired axial orientation within the mold cavity.
6. The method of claim 1, further comprising the step of cleaving off excess fiber and polishing an end of said solid connector structure.
7. The method of claim 1, further comprising the step of inserting a sleeve into said mold cavity before step (c), said sleeve generally conforming to the shape of said mold cavity, so that said solid ferrule formed in step (d) is sleeved.
8. The method of claim 7, wherein, said sleeve is selected from the group consisting of metal, glass, ceramic and plastic, and said sleeve comprises at least one flange extending axially from at least one end of the sleeve and said filler material is adjacent said flange.
9. Use of flowable, electromagnetic radiation curable filler material for forming in situ, an optical fiber ferrule, said flowable, electromagnetic radiation curable filler material being placed into an open mold cavity through which at least one optical fiber extends, said filler material being subjected to electromagnetic radiation of suitable wavelength to cure said filler material to form a ferrule surrounding said at least one optical fiber.
10. The method of claim 1 wherein step (b) is performed before step (c).
11. The method of claim 1 wherein step (c) is performed before step (b).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65639800A | 2000-09-06 | 2000-09-06 | |
| US09/656,398 | 2000-09-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2354718A1 true CA2354718A1 (en) | 2002-03-06 |
Family
ID=24632872
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2354718 Abandoned CA2354718A1 (en) | 2000-09-06 | 2001-08-01 | Molded optical fiber ferrule and method of making the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2354718A1 (en) |
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-
2001
- 2001-08-01 CA CA 2354718 patent/CA2354718A1/en not_active Abandoned
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| US8939654B2 (en) | 2012-09-27 | 2015-01-27 | Adc Telecommunications, Inc. | Ruggedized multi-fiber fiber optic connector with sealed dust cap |
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