Connector assemblies for optical fiber light cables

Abstract: A connector assembly (5, 5′) includes buffer material (16, 16′) surrounding the optical fibers (11, 11′) at one end of an optical fiber light cable (3) and a ferrule (17, 17′) crimped onto the buffer material (16, 16′) which squeezes the buffer material and packs the optical fiber ends substantially solid. During the crimping operation, the buffer material protects the optical fibers from the ferrule while permitting the optical fibers to be deformed to a desired cross-sectional shape, for example, to that of a polygon so they are packed more solid. Different types of shielding (46, 48, 50, 55) may be used to prevent light from a light source from striking selected areas of the polished end of the connector assembly (5′) including particularly the buffer material (16′) and, if desired, a surrounding ferrule (17′) to reduce heat build-up in the connector assembly (5′) so that more light energy can be transmitted through the light cable (3) without overheating.

Description: This application relates to certain improvements in connector assemblies which serve as an interface between a light source and the ends of optical fiber light cables for transmitting light through the cables, for example, to light emitting panel assemblies including one or more panels made of woven optical fibers. Light is caused to be emitted from the panel by disrupting the surface of the optical fibers in the panel area as by scratching or otherwise deforming as by bending the optical fibers at a plurality of discrete locations along their length such that the angle of bend approximately exceeds the angle of internal reflection. The percentage of light emitted from each bend is proportional to the bend radius and arc length. By controlling the weave spacing and pattern of the woven optical fibers, one can control the shape and radius of the bends at any location on a woven panel to thereby control the desired light output pattern from the panel. The optical fibers can be coated with a material having a refractive index that will cause a change in the attenuation of the optical fibers in the light emitting portion of the panel to increase the optical efficiency of the panel. The amount of attenuation can be varied by varying the index of refraction and thickness of the applied coating. In applications where the coating is applied to the entire length of the fibers in the light emitting portion of the panel, or such light emitting portion is completely encapsulated in such a coating, attenuation changes will occur over the entire light emitting portion. In other applications where increased optical efficiency is desired, it would be desirable to cause attenuation changes only at selected areas of the panel from which light is normally emitted. FR-A-2 097 419 discloses a connector assembly comprising a bundle of optical fibers surrounded at one end by a buffer or ferrule, and a shield for preventing light from a light source from striking selected areas of the end face of the connector assembly. A connector assembly according to the present invention is defined in claim 1. In an embodiment of the invention, the shield comprises a plate overlying the end face of the buffer material. The plate has an opening permitting light to pass through the plate onto the end face of the optical fiber bundle and is supported independently of the connector assembly and located in front of the end face of the optical fiber bundle in spaced relation therefrom to allow air flow between the plate and end face. In an embodiment of the invention, the shield comprises a cap that fits over the one end of the optical fiber bundle. The cap has an outer end wall that prevents the light from striking the end face of the buffer material, and an opening in the outer end wall that permits the light to strike the end face of the optical fiber bundle. The outer end wall of the cap is spaced forwardly of the end face of the connector assembly, and slots are provided in the sides of the cap to permit air flow between the outer end wall and the end face of the connector assembly. In the annexed drawings: Figure 1 is an enlarged schematic longitudinal section through a connector assembly which has been included to aid understanding of the invention; Figure 2 is a transverse section through the connector assembly of Fig 1 taken generally on the plane of the line 2-2 thereof; Figure 3 is an enlarged fragmentary transverse section through the connector assembly of Fig 1 schematically showing the end portions of the optical fibers deformed to the shape of a polygon to permit such end portions to be packed more solid; Figures 4, 6, 8 and 10 are enlarged schematic longitudinal sections through forms of connector assemblies in accordance with this invention; and Figures 5. 7, 9 and 11 are end views of the respective connector assemblies shown in Figs 4, 6, 8 and 10. Referring now in detail to the drawings, and intially to Figs 1 and 2, there are schematically shown a light cable 3 to transmit light from a remote light source to a light emitting panel. At the outermost end of the optical cable 3 is a connector assembly 5 which serves as an interface between the light source and the optical fiber ends. Each optical fiber 11 may be made from one or more optical fiber strands each including a light transmitting core portion of a suitable transparent material and an outer sheath or cladding of a second transparent material having a relatively lower index of refraction than the core material to assist in preventing the escape of light along its length. The core material can be made of either glass or plastic or a multi-strand filament having the desired optical characteristics. The index of refraction of the outer sheath material is less than that of the core material, whereby substantially total reflection is obtained at the sheath-core interface, as well known in the art. The optical fibers 11 are brought together and bundled to form either a ribbon cable or a round cable 3 as desired to transmit light from the remote light source to one or more light emitting panels. At the outermost end of the optical cable 3 is the connector assembly 5 which, as shown in Figs. 1 and 2, consists of a buffer material 16 surrounding the gathered optical fibers 11 and a ferrule 17 crimped onto the buffer material which squeezes the buffer material and packs the optical fiber ends 18 substantially solid. The buffer material 16 may be made of any suitable material such as Teflon that will protect the optical fibers 11 from the ferrule 17 during the crimping operation. The buffer material desirably has a low refractive index so that it does not cause high attenuation on the surface of the optical fibers 11 contacted thereby. If desired, the connector assembly 5 may be heated during the crimping operation to soften the buffer material 16 or optical fibers 11 to permit them to be deformed to the desired cross-sectional shape, for example, to that of a polygon, so that the compacted ends of the optical fibers are packed more solid as schematically shown in Fig. 13. After crimping, the cable end 19 may be cut off and polished to the desired finish. Both the ferrule 17 and buffer material 16 may have a lip or flange thereon to provide a locating point or surface thereon. Also, if the optical fibers 11 are made of plastic, the connector assembly 5 may be heat treated to preshrink the optical fibers 11 before polishing to produce a higher operating temperature limit. After polishing, the polished end 19 of the connector assembly 5 may be coated with a suitable coating that reflects certain wavelengths of light. Also, a window or filter 20 may be adhesively bonded to the polished end 19 of the connector assembly 5. Figs. 4-11 show connector assemblies in accordance with this invention which are generally similar in construction to the connector assembly 5 previously described. Accordingly, the same reference numerals followed by prime symbols are used to designate like parts. However, the connector assemblies shown in Figs. 4-11 differ from that shown in Fig. 1 in that different types of shielding are used to prevent light from striking selected areas of the polished ends of the connector assemblies including particularly the buffer material and, if desired, the ferrule to reduce heat build-up in the connector assemblies while still permitting light (from a light source) to be focused onto the optical fiber ends so that more light energy can be transmitted through the optical fibers without overheating. In the embodiment shown in Figs. 4 and 5 the shielding material comprises a reflective coating or disc 46 applied to the outer end of the buffer material 16', and, if desired, to the ferrule 17' as well to reflect light from the light source 4 away from these areas while still allowing light to be focused onto the polished ends of the optical fibers 11. Where the shielding material 46 is a disc, the disc may be glued, fastened or otherwise attached directly to the buffer material 16' and, if desired, the ferrule 17' to cover same while a central opening 47 in the disc allows the light to be focused onto the ends of the optical fibers 11. The disc 46 may be made, for example, of Mylar or other suitable plastic having an adhesive surface on its inner face for attachment to the buffer material and a silver or other mirror-like coating on its outer surface for reflecting light. Alternatively, instead of positioning the shielding material in direct contact with the buffer material as shown in Figs. 4 and 5 the shielding material may be positioned a slight distance away from the polished end of the connector assembly as schematically shown in Figs. 6-11 to provide an air space therebetween to promote air flow for cooling purposes. Also, spacing the shielding material away from the polished end of the connector assembly has the further advantage of preventing the shielding material from acting as an insulator and/or transferring heat from the shielding material to the connector assembly. In each instance, an annular opening through the shielding material allows light from the light source to strike the ends of the optical fibers, but not the buffer material and ferrule. In the embodiment shown in Figs. 6 and 7, the shielding material comprises a plate 48 supported independently of the connector assembly 5', positioned to allow light to pass through an annular opening 49 therein and strike the ends of the optical fibers 11' but not the buffer material 16' and ferrule 17'. Because there is no direct contact between the plate 48 and connector assembly 5', the plate 48 may be made of a material such as black anodized aluminum that absorbs the light that would otherwise strike the outer end of the buffer material and ferrule, or have a reflective surface that reflects such light. In Figs. 8 and 9 the shielding material is in the form of an annular plate 50 which is mechanically fastened to the buffer material 16' using stand-offs 51 to position the plate in front of the polished cable end. The plate 50 is desirably made of a material that reflects the light from the light source away from the outer end of the buffer material and ferrule, whereas a central opening 52 in the plate in alignment with the optical fiber ends permits the light from the light source to strike such optical fiber ends. In Figs. 10 and 11 the shielding material is in the form of a cap 55 that fits over the polished connector end. The cap includes a reflective outer end wall 56 that is desirably spaced a slight distance from the polished connector end, with slots 56' in the sides of the cap to allow air to pass between the cap end wall 56 and connector end for cooling purposes. The cap end wall 56 has a central opening 57 therein of a size which allows light from the light source to be focused onto the ends of the optical fibers 11' but not on the buffer material and ferrule. Light from the light source striking the cap end wall 56 will be reflected away from the outer end of the buffer material and ferrule.

Claims: A connector assembly (5') comprising a bundle of optical fibers (11') made of plastic, buffer means (16) surrounding one end of the optical fiber bundle, ferrule means (17) crimped onto the buffer means (16) to squeeze the buffer means around said one end and deform the optical fiber bundle at the end face to a desired cross-sectional shape thereby to pack the optical fibers solid at the end face, said buffer means (16) and said ferrule means (17) terminating at the end face of said optical fiber bundle (11'), and shielding means (46, 48, 50, 55) for preventing light from a light source from striking selected areas of an end face of the connector assembly (5') in particular the buffer to reduce heat build-up in the connector assembly (5') so that more light energy can be transmitted through the optical fibers without overheating. The connector assembly of claim 1 wherein said shielding means comprises a plate (48) overlying the end face of the buffer means (16'), the plate (48) having an opening (49) permitting light to pass through the plate (48) onto the end face of the optical fiber bundle, the plate (48) being supported independently of the connector assembly (5') and located in front of the end face of the optical fiber bundle in spaced relation therefrom to allow air flow between the plate and end face. The connector assembly of claim 1 wherein the shielding means comprises a cap (55) that fits over the one end of the optical fiber bundle, the cap (55) having an outer end wall (56) that prevents the light from striking the end face of the buffer means (16'), and an opening (57) in the outer end wall (56) that permits the light to strike the end face of the optical fiber bundle, the outer end wall (56) of the cap (55) being spaced forwardly of the end face of the connector assembly (5'), and slots (56') in the sides of the cap (55) to permit air flow between the outer end wall (56) and the end face of the connector assembly (5').

Inventors: PARKER JEFFERY R, PARKER, JEFFERY R.
Applicants: LUMITEX INC, LUMITEX INC.
Application year: 1990
Main classification: G02B6
IPC codes: G02B6, F21V8