Optical: systems and elements – Optical amplifier – Correction of deleterious effects
Reexamination Certificate
1999-09-28
2001-07-10
Hellner, Mark (Department: 3662)
Optical: systems and elements
Optical amplifier
Correction of deleterious effects
C359S341430, C359S199200
Reexamination Certificate
active
06259554
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to an optical amplifier repeater system which carries out bidirectional optical amplification and repeating of signal light by use of a plurality of repeater stations connected to each other in a multistage fashion.
2. Background Art
Employed for carrying out long-distance transmission in optical communications systems is a technique in which a plurality of repeater stations are connected to each other in a multistage fashion, while each repeater station is provided with an optical amplifier for amplifying the signal light transmitted thereto. In the case where an abnormality such as a break occurs at any location on an optical transmission line in such an optical amplifier repeater system, it is necessary to take steps to stop the operation of the optical amplifiers and remove the abnormality. To this end, it is required that the position where the abnormality has occurred be specified correctly.
Known as techniques for sensing abnormalities in optical amplifier repeater systems are those disclosed in Japanese Patent Application Laid-Open No. Hei 5-130043 and Japanese Patent Application Laid-Open No. Hei 4-324335.
In the optical amplifier repeater system in the former publication, whether signal light has reached an optical amplifier or not is detected, so as to sense abnormalities in its optical transmission line and the like, and the operation of the optical amplifier is stopped if the signal light has not reached there. In the latter optical amplifier repeater system, on the other hand, while the reflected return light of the signal light outputted from an optical amplifier is being monitored, if the quantity of reflected return light is large, then it is determined that the optical transmission line is abnormal, so that the operation of the optical amplifier is stopped.
In the former, while the operations of the repeater stations located downstream from the break point of the optical transmission line are stopped, abnormalities of such a degree that no break is generated thereby cannot be detected.
In the latter, on the other hand, the operations of the repeater stations located upstream from the break point of the optical transmission line are stopped. When the distance from an optical amplifier to the break point is long, reflected return light with a sufficient intensity may not go back to the optical amplifier, whereby it may not be able to detect an abnormality even though there is a break in the optical transmission line.
DISCLOSURE OF THE INVENTION
In view of these problems, it is an object of the present invention to provide an optical amplifier repeater system which can reliably detect abnormalities such as breaks in optical transmission lines and the like.
In order to solve the above-mentioned object, the optical amplifier repeater system in accordance with the present invention is an optical amplifier repeater system comprising a pair of transmission lines and a plurality of repeater stations connected to each other in a multistage fashion, so as to bidirectionally transmit signal light between terminal stations, wherein each of the plurality of repeater stations comprises a pair of optical amplifiers for amplifying the signal light being transmitted, and a monitor apparatus for monitoring a state of the signal light fed into each optical amplifier and stopping, when the signal light fed into one optical amplifier is abnormal, an operation of the optical amplifier and then, after a lapse of a predetermined time, stopping an operation of the other optical amplifier.
In this optical amplifier repeater system, since the state of signal light is monitored, abnormalities are reliably detected in each repeater station, the operation of its optical amplifier is automatically stopped, and then the operation of the optical amplifier on the transmission line for the opposite direction is also stopped, so that the signal light amplification is stopped on the transmission lines for both directions. Since the signal light intensity sent downstream via each transmission line is lowered, the operations of optical amplifiers are similarly stopped in the downstream repeater stations as well. As a consequence, information about occurrence of an abnormality can reliably be transmitted upstream of the location where the abnormality has occurred. Finally, the information about occurrence of the abnormality is reliably transmitted to a terminal station, whereby the transmission of signal light can be stopped.
In the optical repeater system in accordance with the present invention, each of the plurality of repeater stations is provided with a pair of optical amplifiers and a monitor apparatus; the monitor apparatus having a pair of monitor light receivers each receiving predetermined monitor light transmitted from an upstream adjacent repeater station or terminal station, and a pair of monitor light transmitters each adding predetermined information to the monitor light received by the monitor light receivers and transmitting the resulting light to a downstream adjacent repeater station or terminal station; the monitor apparatus monitoring states of the signal light and monitor light transmitted through each of the transmission lines and adding, when both of the signal light and monitor light transmitted through at least one of the transmission lines are abnormal, information indicative of an abnormal condition to the monitor light transmitted to the downstream side of both of the transmission lines.
In this optical amplifier repeater system, both of the signal light and monitor light transmitted through each transmission line are monitored at the repeater stations. If an abnormality occurs in the transmission line, then both of the signal light and monitor light exhibit a transmission failure. Since an abnormality occurs in only one of the signal light and monitor light due to the other causes, e.g., due to an abnormality in an optical amplifier in an upstream repeater station or an abnormality in the monitor light transmitter, abnormalities in the transmission lines can be solely distinguished therefrom, so as to be determined accurately. In case of an abnormality in a transmission line, its information is added to the monitor light and is transmitted to a downstream repeater station. In the downstream repeater station, information about the opposite transmission line is added to the monitor light transmitted from its upstream repeater station, and the resulting light is outputted therefrom. Each terminal station can obtain information about the abnormality in the transmission line.
In the case where both of the signal light and monitor light fed into one of the optical amplifiers are abnormal, the monitor apparatus stops the operation of this optical amplifier, then stops the operation of the other optical amplifier after a lapse of a predetermined time, and causes the monitor light outputted to the transmission line opposite to the transmission line in which the abnormality has occurred to be set to a state where the monitor apparatus in the downstream repeater station determines that the monitor light is abnormal.
In such a configuration, the signal light amplification in both transmission lines can automatically be stopped when an abnormality is detected in a transmission line. For example, if an optical connector of the unbroken one of the transmission lines is removed therefrom by any chance, high-output signal light can be prevented from unnecessarily emitting from the detached portion, whereby safety in operations can be improved.
Preferably, after a lapse of a predetermined time since the monitor light has been set to a state where the monitor apparatus in the downstream repeater station determines that the monitor light is abnormal, the monitor apparatus returns the monitor light to a state where the monitor apparatus in the downstream repeater station determines that the monitor light is normal. As a consequence, the transmission of information by the monitor light is established even after the signal light is
Nishimura Masayuki
Shigematsu Masayuki
Hellner Mark
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
LandOfFree
Optical amplifier repeater system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical amplifier repeater system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical amplifier repeater system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2542014