Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-08-04
2001-11-27
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06323973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for optical transmission and a method therefor, for transmitting an amplified light signal via a transmission path. In particular the invention relates to an apparatus for optical transmission and a method therefor, where release to the surroundings of a high output light signal is prevented in the case where a connector for connecting an optical fiber becomes disconnected or the optical fiber becomes damaged.
2. Description of the Related Art
For example, with image distribution systems such as optical CATV systems, in order to provide a service to several thousand subscribers with a single system, it is required to branch a high output light signal of a high optical power level into a plurality to transmit to the respective subscribers. To obtain such a high output light signal, in general an optical amplifier or the like is used.
With a system for handling such a high output light signal, then for example, in a case such as where a connector connecting between an output port outputting a light signal and a transmission path becomes disconnected, there is the possibility of the high output light signal being released to the surroundings. To prevent this release of the high output light signal, conventionally countermeasures are adopted such as having a construction where for example the Fresnel reflection light generated at the end face of the opened output port due to disconnection of the connector is detected, and the amplifying operation of the optical amplifier is controlled to stop or attenuate the light output so that the high output light signal is not released to the surroundings.
As a conventional apparatus incorporating such a function to control the operation of an optical amplifier at the time of detecting the occurrence of an abnormality, to prevent the release to the surroundings of the high output light signal, there is for example the disclosures of Japanese Unexamined Patent Publications Nos. 60-101503, 5-291667, 5-291669, and 6/244805.
However, with systems such as with an image distribution system wherein light signals from a single optical amplifier are multiply branched and used, then for example, at the time of enlargement of the circuit, the terminator attached to the unused port is removed, and the additional circuit connected. In such a case, with the conventional technique, the reflected light at the end face of the output port which has been opened by removing the terminator is detected, and the amplifying operation of the optical amplifier is controlled to stop or attenuate the light output. Consequently, there is the problem that all of the circuits which receive the light signals from the amplifier are shut-off (normal light signal output is shut-off).
In order to solve the abovementioned problem at the time of circuit enlargement, then for example, a measure has been previously adopted which adjusts the detection level of the reflection light so that if only one or two ports are opened, the amplifying operation of the optical amplifier is not limited. If this measure is adopted however, there is the problem that in the case where only one or two ports are opened, high output light signals are released from the opened port.
Furthermore, in the case of the conventional technique where the reflected light is detected, to thereby judge the occurrence of an abnormality in the transmission path, then for example, when an optical fiber is damaged close to a subscriber, the reflected light is attenuated due to the loss between the output port and the damage point, and hence detection of the reflected light becomes difficult. On the other hand, when an optical fiber is damaged close to an output port, detection of the reflected light becomes difficult depending on how this is cut (for example when the breakage is at an incline etc.). Due to this situation where the necessary detection function for the reflected light does not operate normally, a high output light signal is released from the damaged point.
SUMMARY OF THE INVENTION
The present invention addresses the above problems, with the object of providing an apparatus for optical transmission which can accurately detect the opening of an output port or fracture of an optical fiber, or the like, and then corresponding to the output port, restrain release to the surroundings of high output light signals.
Accordingly with the present invention, as shown in
FIG. 1
, with an optical transmission apparatus which includes a light signal generating device
1
for generating an amplified light signal, and an output port
2
connected to an end of a transmission path, and which sends the light signal via the output port
2
to the transmission path, the construction comprises; an abnormality judgment device
3
for judging if an abnormality has occurred in the transmission path connected to the output port
2
, based on a rising signal which passes through the output port
2
and is transmitted towards the light signal generating device
1
, and a light shut-off device
4
for shutting off a light signal transmitted between the light signal generating device
1
and the output port
2
when an abnormality in the transmission path is judged by the abnormality judgment device
3
.
With such a construction, if an abnormality such as disconnection of a connector or fracture of the optical fiber occurs in a transmission path with one end connected to the output port
2
, the condition of the rising signal transmitted from the transmission path via the output port
2
towards the light signal generating device
1
changes. For example, in the case where the light signal transmitted from the other end of the transmission path is used as the rising signal, then a rising signal detected by the abnormality judgment device
3
at normal times is not detected when an abnormality occurs. Furthermore for example, in the case where the reflected light from the open end is used as the rising signal, then a rising signal which is not detected by the abnormality judgment device
3
at normal times is detected when an abnormality occurs. When, based on this change in the rising signal, the occurrence of an abnormality in the transmission path is judged by the abnormality judgment device
3
, then the amplified high output light signal transmitted from the light signal generating device
1
to the output port
2
is shut-off by the light shut-off device
4
.
Consequently, the release to the surroundings of high output light signals from an open end or from a damaged point can be prevented, without limiting the operation of the light signal generating device.
In
FIG. 1
, the construction is shown where the abnormality judgment device
3
detects a rising signal on the light signal generating device
1
side of the light shut-off device
4
. However the basic construction of the present invention may be such that the rising signal is detected on the output port
2
side of the light shut-off device
4
. Moreover, the construction is shown where the light signal is used as the rising signal. However, as shown in
FIG. 2
, an electric signal transmitted from the other end of the transmission path may be used as the rising signal.
In the abovementioned optical transmission apparatus the construction may be such that a branching device for branching the light signal from the light signal generating device
1
into a plurality of light signals is included, and the output ports
2
are multiply provided corresponding to the respective branch ports of the branching device, the abnormality judgment device
3
judges if an abnormality has occurred in the transmission path connected to the respective output ports
2
based on respective rising signals passing through the respective output ports
2
, and the light shut-off device
4
shuts off light signals transmitted between the corresponding output ports
2
and the branch ports only with respect to the transmission path judged to be abnormal by the abnormality judgment device
3
.
With
Fujitsu Limited
Pascal Leslie
Phan Hanh
Staas & Halsey , LLP
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