Optical waveguides – Optical transmission cable – Tightly confined
Reexamination Certificate
1998-01-30
2001-02-27
Lee, John D. (Department: 2874)
Optical waveguides
Optical transmission cable
Tightly confined
C385S100000, C385S114000
Reexamination Certificate
active
06195489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber cord with a small diameter suitable for high-density assembly of wirings between central office equipments, central office optical wirings, or the like, a ribbon cord using the same, and a ribbon cord branch line using the same.
2. Description of the Related Art
The request for higher density assembly of the central office equipments has been increased according to the spread of optical fiber construction in the subscriber's system. In order to satisfy such a request, an optical fiber cord with a small diameter, which is to be used as wirings in or between central office equipments, etc., has been needed.
The optical fiber cord with a small diameter according to a first related art is constructed such that a yarn made of aramid fiber, glass fiber, carbon fiber, etc. are provided longitudinally along a UV curable resin coated optical fiber of a diameter of 250 &mgr;m and then ultraviolet curing resin is coated thereon and cured. A fiber-reinforced covering layer which is formed by distributing reinforcing fibers integrally into the ultraviolet curing resin is then provided. In general, the optical fiber cord having the above configuration has a finished diameter of about 0.5 to 1 mm.
However, in the optical fiber cord according to the first related art, the reinforcing fiber serving as a tension member has been formed like a yarn. Since the yarn has not been tight, a packing factor (ratio of true volume to bulk volume) of the reinforcing fiber in the fiber-reinforced covering layer has not been able to be increased more than 50 volumetric %, so that it has been impossible to be accomplished sufficiently high reinforcement per unit cross section of covering layer. Accordingly, it has been difficult to be accomplished sufficiently high reinforcement in case of making covering layer be smaller in thickness. For example, in the prior art, it has been impossible to fabricate the optical fiber cord with an extremely small diameter of about 250 &mgr;m as the finished diameter.
Hence, it may be considered to increase a packing factor of the fiber-reinforced covering layer by applying monofilament aramid fibers to the optical fiber cord according to the first related art. However, it has been difficult to form such aramid fiber as a monofilament. Since the result ant monofilament is thus inferior to the yarn in characteristic, the sufficiently high reinforcement effect has not been able to be expected.
Otherwise, it is sufficiently possible to employ monofilament glass fibers in the optical fiber cord according to the first related art. However, since such monofilament lacks flexibility, the monofilament has not been satisfied in reliability due to the breakdown during operation.
FIG. 1
is a schematic lateral sectional view showing an optical fiber cord with a small diameter according to a second related art.
The optical fiber cord according to the second related art is constructed such that a yarn
103
made of aramid fiber, glass fiber, etc. are provided longitudinally as a tension member around a UV curable resin coated optical fiber
102
and then a covering layer
104
made of ultraviolet curing resin, etc. is coated thereon and integrally cured.
However, in the optical fiber cord according to the second related art, the reinforcing fiber serving as tension member has been formed like a yarn. Therefore, a rate of the yarn
103
occupied in the covering layer
104
has not been able to be increased more than 50 volumetric %. For this reason, since it has been impossible to be accomplished high reinforcement per unit cross section of covering layer in case of making the covering layer e smaller in thickness, it has been difficult to reduce the finished outer diameter less than 0.5 mm.
In addition, a ribbon cord which is constructed by arranging a plurality of the optical fiber cords in parallel and forming integrally by a matrix material has not been made small in thickness and width similarly, so that such ribbon cord has not satisfied the request for higher density assembly of the central office optical wirings.
Moreover, in the ribbon cord employing the optical fiber cord according to the second related art, the yarn
103
serving as the tension member is provided around the UV curable resin coated optical fiber
102
. Because of the presence of the yarn
103
provided between adjacent UV curable resin coated optical fibers
102
, it has been difficult to expose top ends of the UV curable resin coated optical fibers
102
by removing the matrix material and the covering layer
104
together. There has been such a disadvantage that, since a dimensional discrepancy because of the intervention of the yarn
103
resides between the ribbon cord employing the optical fiber cord according to the second related art and the ordinary optical fiber ribbon, it is impossible to collectively splice them.
SUMMARY OF THE INVENTION
The present invention has been made in light of the above circumstances, and it is an object of the present invention to provide an optical fiber cord which is able to have an extremely small diameter of less than 500 &mgr;m, preferably about 250 &mgr;m as a finished diameter, for example, by enhancing its reinforcement effect sufficiently.
It is another object of the present invention to provide a ribbon cord from which a matrix material and a covering layer together with tension members can be collectively removed and which can be collectively spliced to ordinary optical fiber ribbons when the ribbon cord is formed by using the optical fiber cords, and a ribbon cord branch line formed with the use of the ribbon cord.
In order to achieve the above objects, according to an aspect of the present invention, there is provided an optical fiber cord comprising:
a UV curable resin coated optical fiber;
a plurality of monofilaments provided on the UV curable resin coated optical fiber along a longitudinal direction; and
a resin covering layer formed on a resultant structure.
In the preferred embodiment of the present invention, an outer diameter of the UV curable resin coated optical fiber is set in a range of 120 &mgr;m to 200 &mgr;m (preferably a range of 123 &mgr;m to 127 &mgr;m), an outer diameter of the metal monofilament is set in a range of 20 &mgr;m to 50 &mgr;m, and a finished diameter is set in a range of 190 &mgr;m to 300 &mgr;m (preferably a range of 230 &mgr;m to 270 &mgr;m).
According to another aspect of the present invention, there is provided an optical fiber cord comprising:
a UV curable resin coated optical fiber;
metal monofilaments provided longitudinally on an outer periphery of the UV curable resin coated optical fiber; and
a resin covering layer provided integrally with the UV curable resin coated optical fiber so as to surround the metal monofilaments.
In the preferred embodiments of the present invention, the metal monofilaments are formed by metal wires each of which has a diameter of 20 &mgr;m to 50 &mgr;m and elastic modulus in tension of more than 10,000 kg/mm
2
and less than 50,000 kg/mm
2
. Preferably an enamel thin film with a thickness of 2 to 3 &mgr;m is coated on a surface of the metal monofilament. Preferably a packing factor of the metal monofilaments in the resin covering layer is set to 10 to 80 volumetric %. Preferably the resin covering layer is formed by coating ultraviolet curing resin and then curing the ultraviolet curing resin. Preferably a thickness of the resin covering layer is set substantially equal to an outer diameter of the metal monofilament.
According to still another aspect of the present invention, there is provided an optical fiber cord which is characterized by providing a plurality of tension wires on a UV curable resin coated optical fiber longitudinally and then covering a resultant structure with a covering layer integrally so as to have a rectangular sectional shape; and
wherein the plurality of tension wires are provided in the covering layer on a pair of parallel-opposing surface sides and no tension
Hayano Tetsuo
Ino Etsuo
Ishida Katuyoshi
Kobayashi Kazunaga
Oohashi Keiji
Fujikura Ltd.
Kang Juliana
Lee John D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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