Optical waveguides – With optical coupler – Plural
Reexamination Certificate
1999-09-27
2001-07-31
Dang, Hung Xuan (Department: 2873)
Optical waveguides
With optical coupler
Plural
C385S015000
Reexamination Certificate
active
06269204
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method and system for monitoring (or supervising) of optical transmission lines, and more particularly to a method and system for monitoring of optical transmission lines suitable for an optical network system for performing transmission between a first terminal device (e.g., a central office) and a plurality of second terminal devices (e.g., subscriber terminals).
2. Description of the Related Art
Referring to
FIG. 1
, there is shown a conventional system for monitoring of optical transmission lines. This system includes a first optical fiber transmission line
2
, N second optical fiber transmission lines
4
(#
1
) to
4
(#N) (N is an integer greater than 1), and a branching section
6
for optically connecting the first optical fiber transmission line
2
and the second optical fiber transmission lines
4
(#
1
) to
4
(#N). The branching section
6
is provided by an optical star coupler, for example.
A first terminal device
8
is optically connected to an open end of the first optical fiber transmission line
2
, i.e., an end of the first optical fiber transmission line
2
opposite to the branching section
6
. N second terminal devices
10
(#
1
) to
10
(#N) are optically connected to open ends of the second optical fiber transmission lines
4
(#
1
) to
4
(#N), respectively. For example, the first terminal device
8
is a central office in an optical fiber network system, and the second terminal devices
10
(#
1
) to
10
(#N) are subscriber terminals in the optical fiber network system. Between the first terminal device
8
and each of the second terminal devices
10
(#
1
) to
10
(#N), one-way or two-way communication or transmission using an optical signal having a wavelength &lgr;1 is carried out.
N monitor devices (or supervisory devices)
14
(#
1
) to
14
(#N) are provided in a monitor area (or supervisory area)
12
, so as to detect an abnormality such as a break in each of the second optical fiber transmission lines
4
(#
1
) to
4
(#N). The monitor devices
14
(#
1
) to
14
(#N) are optically connected to the second optical fiber transmission lines
4
(#
1
) to
4
(#N) by WDM (wavelength division multiplexing) couplers
16
, respectively. The monitor devices
14
(#
1
) to
14
(#N) perform OTDR (optical time domain reflectometry), for example, using monitor light (or supervisory light) having a wavelength &lgr;2 to locate abnormal points in the second optical fiber transmission lines
4
(#
1
) to
4
(#N), respectively, or to measure loss characteristics of the second optical fiber transmission lines
4
(#
1
) to
4
(#N), respectively.
In the conventional system shown in
FIG. 1
, the branching section
6
is included in the monitor area
12
where the monitor devices
14
(#
1
) to
14
(#N) are provided. Accordingly, many optical fibers are present in the monitor area
12
, so that the wiring of the optical fibers in the monitor area
12
is complicated. Further, the plural monitor devices
14
(#
1
) to
14
(#N) respectively corresponding to the second optical fiber transmission lines
4
(#
1
) to
4
(#N) are required.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and system which can monitor (or supervise) a plurality of optical fiber transmission lines in a network by using a single monitor device.
In accordance with a first aspect of the present invention, there is provided a system comprising a first optical fiber transmission line; a plurality of second optical fiber transmission lines; a branching section for optically connecting the first optical fiber transmission line and the plurality of second optical fiber transmission lines; a monitor device (or supervisory device) optically connected to the first optical fiber transmission line; and a plurality of reflecting sections respectively provided in the vicinity of open ends of the plurality of second optical fiber transmission lines. The monitor device outputs monitor light (or supervisory light) through the first optical fiber transmission line and the branching section to each of the second optical fiber transmission lines. The reflecting sections reflect the monitor light to thereby generate identification optical signals having different patterns for respectively identifying the second optical fiber transmission lines.
With this configuration, each reflecting section generates the identification optical signal having the pattern for identifying the corresponding second optical fiber transmission line. Accordingly, the monitor device can identify an abnormal one of the second optical fiber transmission lines according to the presence or absence of the corresponding identification optical signal, for example, and can also locate an abnormal point in this abnormal second optical fiber transmission line identified above by applying OTDR. Thus, the plural second optical fiber transmission lines can be monitored by the single monitor device according to the present invention.
In accordance with a second aspect of the present invention, there is provided a system comprising a first optical fiber transmission line; a plurality of second optical fiber transmission lines; a branching section for optically connecting the first optical fiber transmission line and the plurality of second optical fiber transmission lines; a monitor device optically connected to the first optical fiber transmission line; a first terminal device optically connected to an open end of the first optical fiber transmission line; and a plurality of second terminal devices optically connected to open ends of the plurality of second optical fiber transmission lines, respectively. The second terminal devices generate identification signals for respectively identifying the second optical fiber transmission lines. The monitor device detects an abnormality in each of the second optical fiber transmission lines according to the corresponding identification signal.
In accordance with a third aspect of the present invention, there is provided a system comprising a first optical fiber transmission line; a plurality of second optical fiber transmission lines; a branching section for optically connecting the first optical fiber transmission line and the plurality of second optical fiber transmission lines; a monitor device optically connected to the first optical fiber transmission line; and a plurality of external modulation units optically connected to the plurality of second optical fiber transmission lines in the vicinity of open ends of the second optical fiber transmission lines, respectively. The monitor device outputs monitor light through the first optical fiber transmission line and the branching section to each of the second optical fiber transmission lines. The external modulation units modulate the monitor light according to identification signals for respectively identifying the second optical fiber transmission lines to thereby generate identification optical signals, respectively.
In accordance with a fourth aspect of the present invention, there is provided a system comprising a first optical fiber transmission line; N second optical fiber transmission lines (N is an integer greater than 1); a branching section for optically connecting the first optical fiber transmission line and the plurality of second optical fiber transmission lines; a
1
×N optical switch having a first port and N second ports, the second ports being optically connected to the second optical fiber transmission lines, respectively, in the vicinity of the branching section, the first port being selectively connected to one of the second ports; and a monitor device optically connected to the first port of the
1
×N optical switch for outputting monitor light to each of the second optical fiber transmission lines.
In accordance with a fifth aspect of the present invention, there is
Dang Hung Xuan
Fujitsu Limited
Staas & Halsey , LLP
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