Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
2000-10-27
2003-05-20
Feild, Lynn D. (Department: 2839)
Optical waveguides
Accessories
External retainer/clamp
C385S049000, C385S114000
Reexamination Certificate
active
06567603
ABSTRACT:
TECHNICAL FIELD
This invention relates to optical interconnection apparatus (optical circuit board) for mutually connecting optical component, parts and/or devices used in optical communications or optical information processing, such as optical components, optical circuit packs and optical circuit devices, and also to fabrication process thereof.
BACKGROUND ART
To permit optical interconnections between plural optical components in an optical circuit pack or optical interconnections between plural optical circuit packs or between optical circuit devices on each of which optical packs are mounted, these optical components, optical circuit packs and optical circuit devices are provided at terminals thereof with optical connectors to interconnect them together via optical fibers. As these optical fibers have to be arranged with loose in this case, it is a current circumstance that, on an optical circuit pack or inside and/or on a back side of an optical circuit devices, intricately routed lines of the optical fibers extend overlapping one another in the form of a bird's nest and hence occupy a large space. For an optical interconnection process which is complex and requires a large space as described above, a proposal has been made, as a simple process anywhere routing of optical fibers on a two-dimensional plane as desired, to use a sheet or substrate with a pressure-sensitive adhesive coated thereon and to hold optical fibers in place by the pressure-sensitive adhesive as disclosed in JP 2,574,611 B.
Incidentally, the optical interconnection apparatus disclosed in JP 2,574,611 B is obtained in such a way that upon its fabrication, optical fibers are located by a pressure-sensitive adhesive, which is coated on a 25-200 &mgr;m thick, flexible polymer film substrate (base layer) made of “Mylar” or “Kapton” or on fiber jackets, to form a routing pattern and the routing pattern is then covered with the same material as the material used for the substrate, whereby a protective layer is formed. This process is however accompanied by problems in that as optical fibers so located increase in number and the optical fibers increase more overlapped portions (cross-over routing) in the routing pattern so formed, the resulting routing layer of the optical fibers becomes thicker and, because the tacky surface with which the optical fibers are in contact becomes smaller at the overlapped portions of the optical fibers, the protective layer cannot be arranged evenly. There is a further problem in that at the overlapped portions of the optical fibers in the routing pattern, the fixing force by the pressure-sensitive adhesive becomes weaker and the optical fibers are allowed to move, thereby resulting in displacements in the routing pattern (a loss in the intactness of the routing pattern). Moreover, general optical fibers range from 125 to 250 &mgr;m in diameter so that at an overlapped area of three optical fibers, for example, the routing layer of the optical fibers becomes as thick as 375 to 750 &mgr;m. An increase in the overlapped portions of optical fibers in a routing pattern develops lifted portions (air pockets) in a protective layer around optical fibers underneath the protective layer, so that a problem arises in the reliability against temperatures and humidities and in addition, the optical circuit board becomes extremely weak to breakage which may be caused by deformation such as bending. Moreover, the optical interconnection apparatus fabricated by this process includes polymer substrates, which do not have stretchability despite their flexibility, above and below a layer formed of the optical fibers and the pressure-sensitive adhesive and having a thickness of from several hundreds micrometers to several millimeters, and is thus accompanied by a still further problem that the optical interconnection apparatus is provided with reduced flexibility despite the need for high flexibility. The optical interconnection apparatus disclosed in Japanese Patent No. 2,574,611 B is provided at portions thereof, which are adapted for interconnections, with extended tabs. Extension of these tabs, however, results in the occupation of a greater space by the interconnecting portions and also leads to complication in the fabrication of the optical interconnection apparatus.
On the other hand, U.S. Pat. No. 5,292,390 discloses a process for filling a layer of routed optical fibers with a thermoplastic polyurethane to hold the optical fibers in place and also to protect the optical fibers. The problem of a reduction in flexibility, however, remains still unresolved in this process because “Kapton” films, which have low stretchability although their flexibility is high, are used as a substrate for an adhesive layer and a substrate for a thermoplastic polyurethane layer, said layers serving to hold the optical fibers in place, and the layer routing optical fibers also remain held between these films after the fabrication of an optical interconnection apparatus. Further, the polyurethane layer has stiffness despite its flexibility and therefore, stress tends to be applied to optical fibers held in place and protected by it and tends to result in an optical loss. There is accordingly a problem in protecting the optical fibers and holding them in place.
JP 10-68853 A, on the other hand, discloses to fabricate an optical interconnection apparatus by locating optical fibers between laminates, in each of which a film substrate and an adhesive layer are provided with a layer having compressibility, and holding the resulting optical fiber routing layer between the laminate. The layers having compressibility in that invention, however, are arranged to reduce pressures which may be applied to the optical fibers during the fabrication of the optical interconnection apparatus. The film substrates remain in the laminate layers between which the routed optical fibers are held on both sides. The problem of a reduction in the flexibility of an optical interconnection apparatus, therefore, remains still unresolved. Further, as a material which makes up the layers having compressibility, polytetrafluoroethylene, polyethylene, polyurethane foam or the like is used. Since these materials still retain stiffness despite their thermoplastic property, a problem exists in the protection and holding of optical fibers as in the patent referred to in the above.
As has been described above, the conventional optical interconnection apparatus with optical fibers located or routed by making use of flexible substrates is provided on both sides of the two-dimensionally routed optical fibers with film substrates of “Mylar” or “Kapton”. Therefore, such film substrates are arranged on both sides of the optical fiber routing layer of several hundreds micrometers to several millimeters in thickness, and are exposed as surface layers. This optical fiber routing part hence has substantially reduced flexibility, and for optical interconnections, arrangement of extended tabs is needed. As adhesive layers include only on both sides of several hundreds micrometers to several millimeters, there is a problem in the fixed placement and protection of optical fibers. The optical fibers tend to loose the intactness of their pattern, resulting in a substantial optical loss. Therefore it cannot be used as an optical interconnection apparatus. When there is not much space for the arrangement of the optical interconnection apparatus upon interconnection of optical components themselves on an optical circuit pack or interconnection of optical circuit packs together, the optical interconnection apparatus cannot be used due to insufficient flexibility and bendability.
To connect and accommodate a number of optical fibers within a limited space, an optical interconnection apparatus such as an optical circuit board is an effective and indispensable part. A further increase in the number of optical fibers to be routed makes it difficult to route and accommodate all the optical fibers on one plane of a substrate because, if one attempts to route and accomm
Arishima Koichi
Hirayama Mamoru
Kawase Ritsu
Kobayashi Tatsushi
Sukegawa Ken
Feild Lynn D.
Hyeon Hae Moon
McDermott & Will & Emery
Tomoegawa Paper Co. Ltd.
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