Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
2002-06-24
2004-07-06
Lee, John R. (Department: 2881)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
C385S100000, C385S109000, C385S113000, C385S115000, C385S123000, C385S126000, C385S127000
Reexamination Certificate
active
06760528
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin coated optical fiber for an optical fiber cord, the resin coated optical fiber having superior connector insertion characteristics and low temperature characteristics when the resin coated optical fiber is used for an optical fiber cord.
2. Description of Related Art
As a resin coated optical fiber used for an optical fiber cord, conventionally, a resin coated optical fiber formed by coating a coating layer formed of a thermoplastic resin such as nylon
12
around a reinforcing resin coated optical fiber having an outer diameter of 0.4 to 0.5 mm so that the resin coated optical fiber has an outer diameter of 0.9 mm, is used. The reinforcing resin coated optical fiber is formed by coating a reinforcing layer such as silicone resin, UV curable resin, or the like, around a bare optical fiber having an outer diameter of 125 &mgr;m.
The above resin coated optical fiber, in particular, a thermoplastic resin coated optical fiber is formed to an optical fiber cord by longitudinally providing a tensile fiber composed of an aramid fiber and the like along the thermoplastic resin coated optical fiber, and providing an outer jacket composed of a resin such as polyvinyl chloride, nylon, or the like.
When one optical fiber cord is connected to another optical fiber cord, a connector is generally used. Various connectors having different structures are known. Among these, an “SC connector” will be explained as an example.
An SC connector is generally composed of two plugs which respectively fix one end of the first optical fiber cord and one end of the second optical fiber cord, which the cords are connected to each other, and an adaptor for engaging both plugs.
FIGS. 5A
to
5
C are schematic views of a state in which the end of the optical fiber cord is engaged in the plug of the above-described SC connector. Optical fiber cord
10
and plug
30
are shown in
FIGS. 5A
to
5
C.
Plug
30
is composed of plug frame
32
, spring
33
, stop ring
34
, caulking ring
35
, caulking ring
36
, rubber hood
37
, and housing
38
.
Outer jacket
12
and tensile fiber
14
of optical fiber cord
10
are peeled a predetermined length from the end of optical fiber cord
10
, so that the predetermined distance of thermoplastic resin coated optical fiber
16
is exposed. Furthermore, tensile fiber
14
is pressed and closely fitted using caulking ring
35
and the outer jacket
12
is pressed and closely fitted using caulking ring
36
.
In thermoplastic resin coated optical fiber
16
, the reinforcing layer and the coating layer are peeled a predetermined length from the end (not shown) so as to expose the bare optical fiber, and the bare optical fiber is inserted into ferrule
20
. Furthermore, receiving member
21
is provided around ferrule
20
. Receiving member
21
is provided between ferrule
20
and stop ring
34
. Spring
33
for pushing ferrule
20
toward the connection part of the connector to be connected the other connector is received by receiving member
21
.
When the connector is not engaged to the other connector, as shown in
FIG. 5A
, the end surface
22
of ferrule
20
is pushed by spring
33
toward the connection part of the connector to be connected the other connecter, so that a predetermined length of the end portion of ferrule
20
protrudes from housing
38
.
Furthermore, when the connector is engaged to the other connector, as shown in
FIG. 5B
, the end surface
22
of ferrule
20
(i.e., the first ferrule of the first plug) is pushed by the end surface of the second ferrule of the second plug (not shown) and is pushed toward an insertion port of plug
30
. Then, spring
33
is contracted by receiving member
21
, and the end surfaces of the first and second ferrules are pushed and closely contacted with each other by elasticity of spring
33
, so that the connectors are satisfactorily engaged and this state is maintained. The length of ferrule
20
pushed toward the insertion port of plug
30
when the connectors are engaged is normally approximately 0.5 mm.
When the first and second optical fiber cords are connected to the connectors as described above, if thermoplastic resin coated optical fiber
16
has low flexural rigidity, as shown in
FIG. 5C
, ferrule
20
is pushed and subsequently thermoplastic resin coated optical fiber
16
, which is placed behind ferrule
20
, is bent. As a result, loss increases. In order to prevent thermoplastic resin coated optical fiber
16
from bending, flexural rigidity of the thermoplastic resin coated optical fiber used for the optical fiber cord is generally determined to be 18 to 25 N·mm
2
.
In recent years, in order to actualize high speed drawing of the optical fiber and to improve productivity, as the above-described reinforcing resin coated optical fiber having an outer diameter of 0.25 mm is generally used. The reinforcing resin coated optical fiber is formed by coating the bare optical fiber with the reinforcing layer composed of a UV curable resin which can make the reinforcing layer thin and fast curing.
When the above reinforcing resin coated optical fiber having small diameter is used for the thermoplastic resin coated optical fiber having an outer diameter of 0.9 mm, there are some problems as follows.
(1) The thickness of the coating layer becomes thick. When the thremoplastic resin coated optical fiber is exposed to low temperatures, the amount of shrinkage of the coating layer increases. Accordingly, a slight bend is generated in the optical fiber, and then, loss increases.
(2) If a soft material is used for the coating layer of the thermoplastic resin coated optical fiber in order to prevent variation of loss under low temperatures, when the optical fiber cord manufactured from the thermoplastic resin coated optical fiber made by using the soft material is connected to the other optical fiber cord with the connector as described above, the peeled part of thermoplastic resin coated optical fiber
16
placed behind ferrule
20
, tends to bend as shown in
FIG. 5C
, and therefore, loss may increase.
BRIEF SUMMARY OF THE INVENTION
In light of the above problems, an object of the present invention is to provide a thermoplastic resin coated optical fiber which prevents loss from increasing when the optical fiber cord is connected to another optical fiber cord using a connector or when exposed to low temperatures, and exhibits superior transmission characteristics, even if a reinforcing resin coated optical fiber having the outer diameter of 0.25 mm is used as a starting material for the thermoplastic resin coated optical fiber for an optical fiber cord.
The above object is solved by the following aspect of the present invention.
An aspect of the present invention is that a thermoplastic resin coated optical fiber having an outer diameter of 0.81 to 0.99 mm, comprising a reinforcing resin coated optical fiber having an outer diameter of 0.225 to 0.275 mm, wherein a coating layer is provided around the reinforcing resin coated optical fiber, and a flexural rigidity of the thermoplastic resin coated optical fiber is 5.5 to 7.5 N·mm
2
.
According to the above aspect, an optical fiber cord obtained by sequentially providing a tensile fiber and the outer jacket around the thermoplastic resin coated optical fiber prevents loss from increasing when two optical fiber cords are connected to each other using a connector. Furthermore, loss is prevented from increasing under low temperatures.
Furthermore, according to the above aspect, the thermoplastic resin coated optical fiber has sufficient transmission characteristics. At the same time, the outer diameter of the reinforcing resin coated optical fiber used for the thermoplastic resin coated optical fiber is more slender than that of a conventional optical fiber, and is formed by high-speed drawing, and therefore, productivity of the thermoplastic resin coated optical fiber is improved.
The coating layer may comprise a thermoplastic resin having a bending elastic modulus of 200 to 350 MPa
Ohas{acute over (h)}i Keiji
Simomichi Tsuyoshi
Bell Boyd & Lloyd LLC
El-Shammaa Mary
Fujikura Ltd.
Lee John R.
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