Optical waveguides – Optical transmission cable – Loose tube type
Reexamination Certificate
2002-09-03
2004-04-27
Patel, Tulsidas C. (Department: 2839)
Optical waveguides
Optical transmission cable
Loose tube type
Reexamination Certificate
active
06728455
ABSTRACT:
BACKGROUND OF THE INVENTION
Conventionally, in order to make it possible for a home or an office to receive and transmit high-speed broad band information like ultra high speed data, FTTH (Fiber to the home) i.e. an access line optical fiber cable extended from a telephone company is dropped down to a subscriber's home such as a building, a house of the general public via an optical fiber cable core wire, and an optical fiber drop cable has been used as a suitable means for wiring. In short, the optical fiber drop cable (an outdoor cable) is a cable used when dropping an optical fiber down from a utility pole into the home.
As a related optical fiber drop cable known is as shown in FIG.
1
. The optical fiber drop cable
101
comprises an optical element portion
109
and a support wire portion
113
, and an optical fiber tape core wire
103
for example of 0.25 mm diameter and steel wires
105
as tension bodies disposed on both sides of the optical fiber tape core wire for example of 0.4 mm diameter are covered with a thermoplastic resin
107
such as a PVC, a flame-retarded polyolefin to form the optical element portion, and a steel wire
111
as tension body for example of 1.2 mm diameter is covered with the thermoplastic resin
107
such as a PVC, a flame-retarded polyolefin to form the support wire portion. These portions are paralleled one another and are continuously or intermittently fixed together at a thin neck portion.
When a cable is anchored on a utility pole or a building/a house of the general public, it is anchored by means of the support wire portion
113
as a messenger wire after separating the support wire portion
113
from the optical element portion
109
utilizing the thin neck portion.
Taking out the optical fiber tape core wire
103
by tearing off the optical element portion
109
right and left utilizing notch portions
117
which is provided at the central part of the optical element portion, one end of the optical fiber tape core wire is connected to some other fiber within a closure disposed on the utility pole and the other end is connected to a connection box or an OE converter disposed in or out of the house.
SUMMARY OF THE INVENTION
1. Flexible Plastic Material
The conventional optical fiber drop cable
101
described above is liable to an accident by lightning strike, for example, burning of indoor equipments. Therefore, the accident may be avoided either by cutting off the conventional optical fiber drop cable
101
within the connection box disposed on the walls of the building and the house of general public in order not to drop the optical fiber drop cable directly into the house, or by cutting off only the steel wire
105
in the optical element portion
109
using a specific tool in order to drop the cable without the steel wire into the house. Besides, the support wire portion
113
has little problem because it will be cut off when the cable is anchored on the utility pole or under eaves of the house of the general public.
According to the present invention, an optical fiber drop cable, which protects an accident by lightning strike and also has low cost, and a manufacturing method thereof can be provided.
According to the first technical aspect of the present invention, an optical fiber drop cable
1
comprising: an optical element portion
9
where an optical fiber core wire
3
and at least one pair of first tension bodies
5
,
5
disposed parallel on both sides of the optical fiber core wire are covered with a cable sheath; and a cable support wire portion
15
where a second tension body
11
is covered with a sheath
13
, wherein both of the portions are fixed together continuously or intermittently, and said first tension bodies are composed of a plastic material. The tensile elastic modulus of said plastic material is preferably between 10000-50000 N/mm
2
. Further, a cross section of said first tension bodies is preferably noncircular.
According to the second technical aspect of the present invention, a manufacturing method of the optical element portion
9
of the optical fiber drop cable
1
, wherein said optical element portion is fixed to the cable support portion
15
along the primary axis of said cable, and said optical element portion includes first tension bodies
5
,
5
comprising a flexible plastic material
37
and an optical fiber core wire
3
,
29
all of which are covered with a cable sheath
7
consisting of a resin
39
, comprises the steps of: (i) running said optical fiber core wire
29
in the prescribed direction; (ii) extruding said flexible plastic material
37
synchronizing with the running of said optical fiber core wire; and (iii) extruding said resin
39
synchronizing with the running of said optical fiber core wire
29
, said flexible plastic material contacting said resin before the plastic material solidifies.
2. Molding of an Electrically Nonconductive Material
Generally, with regard to the optical fiber drop cable
101
having weak adhesion between the tension bodies
105
and the cable sheath
107
, there have been such problems that troubles like increase in optical transmission loss or breakdown of the optical fiber core wire
103
might occur when bending, squeezing, etc. were applied, most likely when thermal hysteresis such as heat cycle were additionally applied.
Thus, the adhesion (drawing force) between the tension bodies
105
within the optical element portion
109
and the cable sheath
107
is a necessary item for the characteristics of the optical fiber drop cable. However, when the optical fiber drop cable
101
is manufactured by extrusion molding, simple plain extrusion molding of the electrically nonconductive material such as glass fiber, aramid fiber, FRP being used for the tension bodies
105
within the optical element portion
109
together with the support wire
111
, the optical fiber core wire
103
, etc. cannot provide suitable adhesion. Therefore, conventionally, an adhesive layer is interposed between the tension bodies
105
and the cable sheath
107
so as to increase adhesion described above, resulting in high cost because of increased manufacturing processes.
According to the present invention, the adhesion between the tension bodies within the optical element portion and the cable sheath is enhanced without interposing the adhesive layer. Moreover, the optical fiber drop cable can be provided with increased anti-torsion characteristics and ability to protect the increase in optical transmission loss.
According to the third technical aspect of the present invention, an optical drop cable
201
comprising: an optical element portion
207
having an optical fiber core wire
205
and a pair of first tension bodies
213
,
213
, each of said first tension bodies being disposed substantially parallel along the primary axis of said cable on both sides of said optical fiber core wire intervening between them, said pair of the first tension bodies and said optical fiber core wire are covered with a cable sheath
203
; and a cable support wire portion
211
, including a second tension body
217
covered with a sheath
219
, said optical element portion
207
and said cable support wire portion
211
being fixed together along the primary axis of said optical fiber drop cable
201
, wherein said first tension bodies are composed of an electrically nonconductive material and a circumference thereof is formed into a rugged shape.
REFERENCES:
patent: 4971419 (1990-11-01), Gartside et al.
patent: 5050957 (1991-09-01), Hamilton et al.
patent: 5155304 (1992-10-01), Gossett et al.
patent: 5448670 (1995-09-01), Blew et al.
patent: 62-94807 (1987-05-01), None
patent: 2000-171673 (2000-06-01), None
patent: 2001-83385 (2001-03-01), None
Y. Nakatsuii, et al., Proceedings of the 1997 IECE General Conference, B-10-20, pp. 529, “Studies on Optical Cable for Residentical Premises and Office Buildings,” Mar. 24-27, 1997 (with partial English translation).
M. Kusakari, et al., Proceedings of the 1997 Communications Society Conference of IEICE, B-10-22, pp. 321, “Development
Kobayashi Kazunaga
Kusakari Masahiro
Ohashi Keiji
Tanaka Shimei
Fujikura Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Tulsidas C.
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