Optical: systems and elements – Optical amplifier – Optical fiber
Reexamination Certificate
2000-11-29
2003-09-02
Black, Thomas G. (Department: 3663)
Optical: systems and elements
Optical amplifier
Optical fiber
Reexamination Certificate
active
06614588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical amplifier for repeating optical signals in an optical fiber system.
2. Description of the Related Art
FIG. 1
is a schematic diagram showing the configuration of a conventional optical fiber repeating and transmitting system, as disclosed, for example, in the Patent Application Laid-Open No. 5-268167.
FIG. 2
is a schematic diagram showing the detailed configuration of each of the optical amplifiers therein. In
FIG. 1
, reference numerals
1
a
to
1
c
denote a plurality of optical amplifiers provided in series, numerals
2
a
to
2
d
denote power feeding lines,
3
a
to
3
d
and
4
a
to
4
d
all denote optical fibers,
5
denotes a constant-current power supply for providing a constant current to the power feeding line
2
a
, and numerals
6
a
and
6
b
denote optical transmission terminal devices, respectively provided at the transmission end and the reception end of the transmission system.
As shown above, in the transmission lines
3
a
to
3
d
and
4
a
to
4
d
connecting the optical transmission terminal devices
6
a
and
6
b
, a plurality of optical amplifiers
1
a
to
1
c
are provided in series, and the power feeding to each of these optical amplifiers
1
a
to
1
c
is carried out normally by a constant-current power feeding method, in which a constant direct current is fed by a constant-current power supply provided in the above transmission end or the reception end of the transmission system by way of the power feeding lines
2
a
to
2
d.
In
FIG. 2
, numeral
1
a
denotes an optical amplifier,
2
a
and
2
b
denote power feeding lines,
3
a
,
3
b
,
4
a
and
4
b
denote optical fibers, numerals
11
and
12
denote optical repeater circuits for amplifying and repeating optical signals,
13
and
14
denote bypass circuits, which are connected respectively to the optical repeater circuits
11
and
12
in parallel for controlling the amount of current for driving the optical repeater circuits
11
and
12
(hereinafter referred to just as “drive current”), numeral
15
denotes a constant-current power supply connected to the optical repeater circuits
12
and the bypass circuit
14
in series, and numeral
16
denotes a constant-voltage diode connected in parallel to these repeater circuits
11
and
12
, the bypass circuits
13
and
14
, and the constant-current power supply
15
.
Next, the operation of the conventional optical amplifier is now explained as follows.
The up-link optical signal input through the optical fiber
3
a
is amplified and repeated at the optical repeater circuit
12
and is output to the optical fiber
3
b
, whereas the down-link optical signal input through the optical fiber
4
b
is amplified and repeated at the optical repeater circuit
11
and is output to the optical fiber
4
a.
On the other hand, the-optical repeater circuit
11
and the optical repeater circuit
12
are connected to each other in series, and in each of the optical repeater circuits
11
and
12
, the bypass circuits
13
and
14
for allowing all or one part of the fed current to pass through are connected in parallel respectively. Due to this, the current input through the power feeding line
2
a
is branched to the optical repeater circuit
11
and the bypass circuit
13
, and also branched to the optical repeater circuit
12
and the bypass circuit
14
.
To the optical repeater circuit
11
and the bypass circuit
14
, the constant-current power supply
15
is further connected in series, so as to limit the maximum current flowing into the optical repeater circuits
11
and
12
. To each of these optical repeater circuits
11
and
12
, the bypass circuits
13
and
14
and also the constant-current power supply
15
, the constant-voltage diode
16
is connected in parallel. This constant-voltage diode
16
bypasses the excess current when an excessive amount of current is flown into the power feeding line
2
a
, thereby to implement a stable operation thereof.
As the conventional optical amplifier is constructed as explained above, the operating state of the optical repeater circuits
11
and
12
is controlled to keep constant even when the current fed to the optical amplifier
1
a
is fluctuated, and due to this, the operating state of these optical repeater circuits
11
and
12
cannot be changed from outside. Subsequently, there has been such a problem that when a malfunction occurs to one of the optical amplifiers due to the long-term use of a transmission system, the output level of other normal state optical amplifiers cannot be changed and so on.
SUMMARY OF THE INVENTION
The present invention has been proposed to solve the problems aforementioned, and it is an object of the present invention to provide an optical amplifier which is capable of setting the output level of the optical repeater circuits therein in accordance with the amount of current fed to the optical amplifier.
In order to achieve the above objects, the optical amplifier according to a first aspect of the present invention is constructed such that it comprises: a bypass circuit for controlling the amount of the drive current of the optical repeater circuit on the basis of a setting signal, a voltage limitter circuit that is connected to the optical repeater means in parallel and limits the voltage applied to the optical repeater means, and a current detection means, which is connected in series to a parallel circuit composed of the optical repeater means and the voltage limitter circuit, detects the current amount fed to the parallel circuit, and generates a setting signal to the bypass circuit in accordance with the amount of the fed current thus detected.
Due to this construction, the current detection means generates a setting signal in accordance with the detected amount of the fed current, while the bypass circuit controls the amount of the drive current of the optical repeater circuit on the basis of the thus generated setting signal, so that such an effect that the output level of the optical repeater circuit can be controlled in accordance with the amount of the current fed to the device can be obtained.
Further, due to this construction, since not only the amount of current flown into the optical repeater, but that flown into the voltage limitter circuit can also be detected, total amount of the fed current can be accurately counted, so that a setting signal in accordance with the amount of the fed current can be generated efficiently.
Still further, due to this construction, an excess amount of current can be bypassed, so that a stable operation can be implemented.
The optical amplifier according to another aspect of the present invention further comprises a current limitter circuit, which is connected in series to the optical repeater means for limiting the current flowing into the optical repeater means.
Due to this construction, the maximum current flown into the optical repeater circuit can be suppressed, so that an unstable operation can be prevented.
The optical amplifier according to further aspect of the present invention is constructed such that current detection means further comprises a current detecting section for detecting the fed current, and a filtering section for smoothing a detection signal detected by the current detecting section.
Due to this construction, a fluctuation of the detection signal of the fed current can be smoothed, so that such an effect is obtained that a setting signal can be generated efficiently in accordance with the amount of the fed current.
The optical amplifier according to further aspect of the present invention is constructed such that the current detection means further comprises a current detecting section for detecting the fed current, an impedance converter for converting a detection signal detected by the current detecting section to a voltage signal of low impedance, and a current generating section for generating a current amount setting signal to the bypass circuit in accordance with the voltage thus converte
Akiba Shigeyuki
Edagawa Noboru
Horiuchi Yukio
Matsushita Kiwami
Suzuki Masatoshi
Birch & Stewart Kolasch & Birch, LLP
Black Thomas G.
Hughes Deandra M.
Mitsubishi Denki & Kabushiki Kaisha
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