Connector assemblies for optical fiber light cables

A connector assembly includes buffer material surrounding the optical fibers at one end of an optical fiber light cable and a ferrule crimped onto the buffer material 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 may be used to prevent light from a light source from striking selected areas of the polished end of the connector assembly including particularly the buffer material and, if desired, a surrounding ferrule to reduce heat build-up in the connector assembly so that more light energy can be transmitted through the light cable without overheating.

BACKGROUND OF THE INVENTION 
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. 
A fiber optic light emitting panel generally of this type is disclosed in 
applicant's aforementioned copending U.S. application Ser. No. 171,844 now 
U.S. Pat. No. 4,885,663. Also, as further disclosed in such copending 
application, 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. 
SUMMARY OF THE INVENTION 
According to the present invention, a connector assembly is provided at an 
end of an optical fiber light cable to serve as an interface between a 
light source and the light cable. The connector assembly includes a buffer 
material surrounding the end portions of the optical cable fibers and a 
ferrule that is crimped onto the buffer material to pack the end portions 
substantially solid. 
Further in accordance with the invention, the connector assembly may be 
heated during crimping to cause the optical cable fibers to be deformed to 
a desired cross-sectional shape so that they are packed more solid. 
Still further in accordance with the invention, the optical cable fibers 
may be made of plastic and the connector assembly heat treated before 
crimping to preshrink the optical cable fibers to provide a higher 
operating temperature limit. 
Also according to the invention, the polished end of the connector assembly 
may be coated with a suitable coating that reflects certain wavelengths of 
light. Moreover, different types of shielding may be positioned relative 
to the polished end of the connector assembly to prevent light from 
striking selected areas of such polished end including particularly the 
buffer material and, if desired, a surrounding ferrule to reduce heat 
build-up in the connector assembly while still permitting light to be 
focused onto the optical cable fiber ends so that more light energy can be 
transmitted through the light cable without overheating. 
To the accomplishment of the foregoing and related ends, the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims, the following description and the annexed 
drawings setting forth in detail certain illustrative embodiments of the 
invention, these being indicative, however, of but several of the various 
ways in which the principles of the invention may be employed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in detail to the drawings, and initially to FIGS. 1 and 2, 
there are schematically shown two different panel assemblies 1 and 1' in 
accordance with this invention each including one or more light emitting 
panels 2, 2' having light cables 3 at one or both ends to transmit light 
from a remote light source 4 to the 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 4 and the optical fiber ends. The panel 
assembly 1 shown in FIG. 1 includes a single light emitting panel 2, with 
an optical cable 3 and connector assembly 5 at one end thereof, whereas 
the panel assembly 1' shown in FIG. 2 includes two light emitting panels 
2, 2' interconnected together by means of an optical cable 3' and having 
another optical cable 3 connected to the panel 2 with a connector assembly 
5 and light source 4 at the outermost end thereof. 
Each light emitting panel 2 (or 2') may be made of one or more layers 10 of 
optical fibers 11 which may be woven into a sheet or mat in the manner 
disclosed, for example, in U.S. Pat. No. 4,234,907 granted to Maurice 
Daniel on Nov. 18, 1980, the disclosure of which is incorporated herein by 
reference. In the example shown in FIG. 3 of the present application, the 
light emitting panel 2 consists of one woven optical fiber layer 10, 
whereas in the example shown in FIG. 5, the panel consists of two such 
layers 10, 10'. Preferably, the optical fibers 11 of each layer are woven 
only in the warp direction, with fill threads 12 woven in the weft 
direction. However, it should be understood that the fill threads 12 could 
also be optical fibers if desired. The weft threads are the threads 
usually carried by the shuttle of a weaving loom, whereas the warp threads 
extend lengthwise of the loom, crossed by the weft threads. 
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. 
To cause light to be emitted from each light emitting panel 2, the external 
surface of the optical fibers 11 may be disrupted as by bending the 
optical fibers 11 at a plurality of discrete locations along their lengths 
as schematically shown in FIGS. 3 and 5 such that the angle of each bend 
15 approximately exceeds the angle of internal reflection so that a 
portion of the light will be emitted at each bend 15. 
The uniformity of illumination of each light emitting panel 2 may be varied 
by varying the shape of the optical fiber disruptions or bends 15 and/or 
the spacing between such disruptions or bends as by varying the pattern 
and tightness of the weave or by varying the proportion of optical fibers 
11 to other material in the weave. The illumination can, for example, be 
increased by placing the disruptions or bends 15 closer together or by 
making the weave progressively tighter as the distance from the light 
source 4 increases. Using fill threads 12 having different coefficients of 
friction will also help to control the tightness of the weave, in that the 
higher the coefficient of friction, the tighter it is possible to weave 
the optical fibers 11. Also, a plurality of fill threads 12 may be used as 
further schematically shown in FIGS. 3-5 to provide more surface points 
for increased friction, and to reduce the thickness of each individual 
fill thread and thus the thickness of the panel 2 while still achieving 
substantially the same rigidity provided by a thicker fill thread. 
The optical fibers 11 at one or both ends of each panel 2 may be 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 4 to one or more 
light emitting panels 2. At the outermost end of the optical cable 3 is 
the connector assembly 5 which, as shown in greater detail in FIGS. 6 and 
7, may consist 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. Alternatively, the ferrule 17 itself may be made out 
of a suitable buffer material, thus eliminating the need for a separate 
buffer. 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. 14-21 show additional 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. 14-21 differ from that shown in FIG. 5 
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 the light source 4) 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. 14 and 15, 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. 14 and 15, the 
shielding material may be positioned a slight distance away from the 
polished end of the connector assembly as schematically shown in FIGS. 
16-21 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. 16 and 17, 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 not 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. 18 and 19, 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. 20 and 21, 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 58 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. 
The light source 4 may be of any suitable type including any of the types 
disclosed in applicant's copending U.S. application Ser. No. 125,323, 
filed Nov. 24, 1987, now U.S. Pat. No. 4,897,771, dated Jan. 30, 1990, 
which is also incorporated herein by reference. If desired, such light 
source 4 may be epoxied directly to the polished end 19 of the connector 
assembly 5 or to the window or filter 20 interposed therebetween. 
A cross-sectional view of one form of light emitting panel 2 in accordance 
with this invention is schematically shown in FIG. 2 wherein a transparent 
coating 25 having a different refractive index than the core material of 
the optical fibers 11 is applied to selected light emitting areas of the 
panel to cause changes in the attenuation of light being emitted from the 
panel. Preferably, the coating 25 is only applied to the outer surfaces of 
the disruptions or bends 15 on one or both sides of each optical fiber 
layer 10. This increases the overall optical efficiency of the panel 2 by 
causing attenuation changes only where the light normally escapes from the 
disruptions or bends 15 of the woven optical fiber panel 2. 
In the example shown in FIG. 2, suitable coatings 25, 25' are applied to 
the outer surfaces of the optical fiber disruptions or bends 15 on both 
sides of the panel 2. One method of applying such coatings to selected 
bend areas of the woven optical fibers 11 is to use the same or different 
carrier members 26, 27 to laminate the coatings to opposite sides of the 
optical fiber panel. The material of the carrier members 26, 27 may vary 
depending on the particular application. For example, carrier member 26 
may be made of a clear plastic film having a suitable coating 25 on one 
side only for coating one side of the panel 2, whereas the other carrier 
member 27 may have a coating 25' on one side for coating the other side of 
the panel and a highly reflective film 28 on the other side. Such a 
reflective film carrier member 27 also acts as a back reflector to 
redirect the light that is emitted from the other side back through the 
panel and out through the one side. Also, the carrier member may be the 
coating itself. For example, a Teflon film may be used both as the carrier 
and coating. 
The amount of attenuation at a particular disruption or bend 15 may be 
controlled by changing the amount of surface area of the bend 15 which is 
covered by the coating 25, 25'. This may be determined, for example, by 
the type of press rolls and amount of pressure used to apply the carrier 
members 26, 27 to the optical fiber layer 10 during the laminating 
process. For example, a higher pressure applied to the carrier members 26, 
27 by press rolls 29, 30 (see FIG. 8) having a softer rubber sleeve will 
produce a greater coated area. Also, by varying the pressure of the press 
rolls 29, 30 as the laminating proceeds along the length of each panel, 
one can gradually increase or decrease the coated area on the optical 
fiber bends 15 to adjust the uniformity of light output from such bends. 
The areas of the optical fibers 11 not in direct contact with the coatings 
25, 25' are encapsulated by air. By changing the index of refraction of 
the coatings 25, 25' relative to the index of refraction of air, one can 
change the ratio of attenuation between a coated and non-coated area of 
the optical fiber panel 2. Such coatings 25, 25' may be a solid, liquid or 
gas. 
If it is desired to emit light substantially only from one side of the 
panel 2, a higher index of refraction coating 25 may be applied to the 
outer surface of the bends 15 on one side of the panel 2, and a lower 
index of refraction coating 25' applied to the outer surface of the bends 
15 on the other side of the panel. The lower index coating substantially 
reduces the amount of light emitted from the other side of the panel, 
which in turn substantially reduces the percentage of light that has to be 
reflected back through the panel. The net result is that the overall 
optical efficiency of the panel is increased because absorption and 
scattering losses due to back reflection of light are lowered. 
When the optical fiber panel 2' contains multiple optical fiber layers 10, 
10' as shown in FIG. 5, a carrier member 31 having the same or different 
index of refraction coatings 32, 33 on opposite sides thereof may also be 
laminated between the optical fiber layers 10, 10' so that the respective 
coatings 32, 33 will contact the outer surfaces of the bends 15 on the 
inwardly facing sides of the optical fiber layers. 
If desired, carriers 26, 27, 31 may be a resin or epoxy-coated film which 
may be heat or radiation cured upon assembly. Also, one of the carriers 35 
may be a metal back reflector 36, or metal inserts 37 may be inserted into 
the panel 38 so that the panel can be bent or formed to a particular shape 
as schematically shown in FIG. 9. 
These various carriers 26, 27, 31 may also be used as a support to hold the 
weave spacing and pattern in position. Furthermore, such carriers may be 
used as a top coat for the woven optical fiber panel 2 to provide 
protection for the panel from hazardous environments. This would make the 
panel assembly 1 particularly suitable for use in certain medical or 
dental applications where it is necessary to clean or sterilize the 
assembly after each use. 
Carrier 26 (shown in FIGS. 3 and 5) may also be a prismatic or lenticular 
film to redirect exit light ray angles for a particular application. 
Alternatively, carrier 26 may be a glass or plastic filter that absorbs or 
reflects certain frequencies of light. Likewise, carrier 26 may be a 
diffuser or transreflector which diffuses light emitted from the woven 
optical fiber panel 2 and reflects ambient light. This type of assembly 1 
could be used to back light a liquid crystal display, where ambient light 
is used for viewing when available and the optical fiber panel 2 is used 
as a back light during low ambient levels. 
FIG. 8 schematically shows a laminating system for making light emitting 
panels of the type disclosed herein using a loom 40 for weaving one or 
more layers 10 of optical fiber material 11. As the optical fiber layer 10 
comes off the loom 40, one or both surfaces of the optical fiber layer 10 
may be coated with a coating 25, 25' having the same or different 
refractive indexes using suitable carriers 26, 27. Also, a suitable back 
reflector 28 may be applied to the exterior of carrier 27, and a clear 
film or diffuser 42 may be applied to the exterior of carrier 26. Suitable 
heaters 44 may be used to apply heat to opposite sides of the panel 
material, and the carriers 26, 27 may be sealed around the periphery 43, 
43' of each panel 2, 2' to provide a protective barrier for each panel 2, 
2' as schematically shown in FIGS. 1 and 2. 
In lieu of using permanent carriers 26, 27 for applying the coating 
material 25, 25', a non-permanent carrier such as a roller 45, 45' may be 
used to coat the outer surface of the bends 15 of a woven optical fiber 
panel 46 with a suitable coating 47, 47' after the weaving process, as 
schematically shown in FIG. 10. A non-permanent carrier is anything that 
applies a coating 47, 47' to selected areas of the optical fiber panel 46 
and does not become part of the final assembly. The roll pressure and 
roller surface type can be controlled to control the size, shape and 
location of the coated areas 47, 47' on the optical fiber bends 15. Also, 
if desired, a coating with a high vapor pressure or a heat or radiation 
durable coating may be used as the coating material to decrease panel 
assembly time due to the fast cure rate of the coating material. 
Regardless of which method is used to apply the coating to selected normal 
light emitting areas of the optical fiber panels, impurities may be added 
to the coating to cause increased attenuation or diffusion of light. Also, 
the added impurities may be used to absorb or reflect predetermined 
frequencies of radiation. Moreover, the coating may if desired be used to 
completely or partially dissolve the outer sheath or cladding that 
surrounds the light transmitting core portion of each optical fiber. 
Such light emitting panel assemblies may be used for different 
applications, including back lighting, photo therapy treatment, and light 
curing of adhesives and the like. Typical back lighting applications would 
be back lighting liquid crystal displays or transparencies and the like. 
Such woven optical fiber panels in accordance with this invention can be 
laminated directly to or inserted behind a liquid crystal display. For 
smaller liquid crystal displays, a light emitting diode may be epoxied to 
a cable end of the panel assembly to provide adequate back light and as 
much as 100,000 hours life. For larger panels, incandescent bulbs, arc 
lamps, the sun, or other light sources may be used. 
To facilitate use of such light emitting panel assemblies for phototherapy, 
the panels may be formed in the shape of a pad, belt, collar, blanket, 
strap, or other such shape. FIG. 11 schematically shows a panel 2 in the 
shape of a pad 50, whereas FIG. 12 schematically shows a panel 2 in the 
shape of a belt 51. In either case, the panel 2 may be placed in direct 
contact or near a patient such as a newborn baby to provide photo therapy 
treatment for jaundice or the like. Presently, such treatment is 
administered using banks of fluorescent lights or single incandescent 
reflector lamps. Jaundice is dissipated by light in approximately the 
450-500 nanometer range. Placing the light emitting panel 2 in direct 
contact with the patient as shown in FIGS. 11 and 12 causes a greater 
percentage of light, at a higher intensity, to be transmitted to the 
patient. Undesired wavelengths of light may be filtered out at the light 
source to produce a cold light emitting panel free of harmful infrared or 
ultraviolet radiation. Also, electrical energy is removed from the 
treatment area because of the fiber optic light cable 3 which permits use 
of a remote light source 4 such as an incandescent lamp, arc lamp, or the 
like. If a tungsten halogen lamp is used, the halogens may be adjusted 
such that the lamp emits a greater percentage of radiation in the 
treatment frequency range. 
Another example of how the light emitting panels of the present invention 
may be used is in the radiation curing or light curing of adhesives or 
epoxies and the like. Light cured adhesives are used in a variety of 
applications, including aerospace, dental, photography, circuit board, and 
electronic component manufacture. With the proper light source, the woven 
fiber optic panels of the present invention will produce high intensity 
uniform light to any desired area. Higher intensity light produces faster 
curing times to greater depths. Also, uniform light output produces even 
curing over an entire surface or object and reduces internal stress. The 
light emitting panels may be fabricated such that they are flexible and 
can conform to the surface or part being cured, and can be fabricated such 
that they are an internal part of an assembly that is self curing or can 
be used in curing. The remote light source also allows the use of the 
light emitting panels of the present invention in dangerous or 
inaccessible locations, or where electricity, heat, EMI or RFI are 
problems. 
Although the invention has been shown and described with respect to certain 
preferred embodiments, it is obvious that equivalent alterations and 
modifications will occur to others skilled in the art upon the reading and 
understanding of the specification. The present invention includes all 
such equivalent alterations and modifications, and is limited only by the 
scope of the claims.