Communications: electrical – Condition responsive indicating system – With particular coupling link
Reexamination Certificate
2002-03-27
2003-11-04
Trieu, Van (Department: 2632)
Communications: electrical
Condition responsive indicating system
With particular coupling link
C340S506000, C340S511000
Reexamination Certificate
active
06642845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal transmitter and a signal quality monitoring device which are preferably incorporated into an apparatus that monitors signal quality of a received signal and notifies an alarm representing the monitored signal quality to a external apparatus or an apparatus that uses such a alarm as information to switch communication lines (as a switching trigger) More specifically, the present invention relates to a signal quality device that is used for a synchronous network, such as SDH (Synchronous Digital Hierarchy) and SONET (Synchronous Optical NETwork defined by Bellcore and spread in North America).
2. Description of the Related Art
FIG. 6
of the accompanying drawings schematically shows an example of a synchronous network (ring network) in conformity with SDH and SONET. Synchronous network
100
is formed by a plurality of signal transmitters (nodes) A, B, C and D connected in a ring through optical paths (optical fibers)
103
. Each of nodes A, B, C and D includes a higher-group apparatus
101
and a lower-group apparatus
102
, which are mainly communicably connected by an electric line (e.g., a coaxial cable)
104
.
Higher-group apparatus
101
byte-multiplexes a lower-group signal received from lower-group apparatus
102
to create higher-group signals suitable to be transmitted over ring network
100
(among nodes A, B, C and D), and then sent the created higher-group signals out to ring network
100
. On the other hand, higher-group apparatus
101
demultiplexes lower-group signals that have been multiplexed into higher-group signals and sends the demultiplexed lower-group signals to lower-group apparatus
102
. Lower-group apparatus
102
sends higher-group apparatus
101
lower-group signals that are communicated over a nonillustrated lower-group-side network, and sends the lower-group-side network lower-group signals that have been received from higher-group apparatus
101
.
As a result, it is possible to add (lower-group) signals already served over the lower-group network to a higher-group signal communicated over ring network
100
in higher-group apparatus
101
, and to drop lower-group signal that is to be sent to lower-group apparatus
102
and to be communicated over the lower-group network from a higher-group signal at higher-group apparatus
101
.
In technology of SONET, assuming that a lower-group signal is OC-12 frame (Optical carrier at level 12; an optical transmission frame of approximately 622 Mb/s), a higher-group signal is OC-48 frame (an optical transmission frame of approximately 2.4 Gb/s) in which four OC-12 frames are multiplexed; and assuming that a lower-group signal is OC-48 frame, a higher-group signal is OC-192 frame (an optical transmission frame of approximately 10 Gb/s) in which four OC-48 frames are multiplexed.
Ring network
100
in conformity with SDH and SONET applies technology of APS (Automatic Path Switch) in which signal transmission paths are automatically switched based on a signal quality of a signal transmitted through optical path
103
.
For example, higher-group apparatus
101
of one node of the four nodes in
FIG. 6
(e.g., node A) transmits two signals identical in contents in two directions of WEST and EAST, respectively. If the transmission signals deteriorate over time and optical path
103
has a problem, higher-group apparatus
101
on the receiver-side node D obtains a quality of each of the transmission signals (a grade of an alarm in accordance with the quality) and selects one of the two transmission signals which is of better quality.
In order to realize the above-mentioned performance, each of nodes A, B, C, and D included in ring network
100
has a function to monitor a quality of a received signal by issuing an alarm and a function for APS. Assuming that an alarm that is issued in accordance with low quality of a signal takes two different grades (importance) each of nodes A, B, C, and D comprises an EAST-side receiving section
111
E as a signal monitoring device
200
, which includes alarm producing/canceling sections
111
a
and
111
b
each for each of the two grade of low quality and a PC (personal computer)
111
c
, and a WEST-side receiving section
111
W identical in configuration with EAST-side receiving section
111
E (signal quality monitoring device
200
). In addition to the two receiving sections
111
E and
111
W, each nodes comprises an EAST-side transmitting section
112
E including an APS section
113
, a WEST-side transmitting section
112
W including an APS section
114
, and another APS section
115
, as shown in
FIG. 7
of the accompanying drawings. Thicker lines and thinner lines in
FIG. 7
respectively represent communication lines for transmission signals transmitted over ring network
100
and communication lines for alarms and control signals.
In receiving section
111
E (signal quality monitoring device
200
), alarm producing/canceling circuit
111
a
discriminates whether a received signal (signal input (
1
)) is in a corresponding grade of low quality and, when the received signal stays in the corresponding grade for a predetermined producing time period, produces continuous output of an alarm corresponding to the grade of low quality. In the meanwhile, when it is discriminated that the received signal stays off the grade of low quality for a predetermined canceling time period, alarm producing/canceling circuit
111
a
cancels the continuous output of the alarm.
In the same manner, the other alarm producing/canceling circuit
111
b
discriminates whether one and the same received signal (signal input (
1
)) is in a grade of low quality higher than the grade that are discriminated in alarm producing/canceling circuit
111
a
and, when the received signal stays in the higher grade for another predetermined producing time period, produces continuous output of a higher-grade alarm corresponding to the higher grade of low quality. In the meanwhile, when it is discriminated that the received signal stays off the higher grade of low quality for a predetermined canceling time period, alarm producing/canceling circuit
111
b
cancels the continuous output of the higher-grade alarm. The lower- and higher-grade alarms will be described in detail later, and coincident outputs of the lower- and higher-grade alarms are not produced.
PC
111
c
receives results of producing/canceling continuous output of the lower- and the higher-grade alarms from alarm producing/canceling circuits
111
a
and
111
b
respectively, and then notifies the received results with respect to states of the alarms to a terminal (not shown in drawings) for system maintenance and provides each of APS sections
113
,
114
, and
115
with the states of the alarms as APS triggers. Receiving section
111
W performs discrimination, and producing/canceling of output of alarms and then provides APS sections
113
,
114
, and
115
with APS triggers in the same manner performed by receiving section
111
E.
Each of APS sections (a receiving signal selector)
113
,
114
and
115
receives two signals, which are identical in contents and which are received via EAST direction and WEST direction (i.e., a signal input (
1
) and a signal input (
2
)), respectively, and selects (switches) either one of the signal inputs (
1
) and (
2
) based on a APS trigger received from PC
111
c
of receiving section
111
E or
111
W. One of the two signal input (
1
) and (
2
) is previously defied as a “work” and the other as a “protection”. If the both signal inputs (
1
) and (
2
) stay off the corresponding grades of low quality thereby no alarm is output, APS sections
113
,
114
, and
115
select a signal input defined as the “work” (in other words, a switching operation to the “work” signal input is carried out). This switching operation is realized by software executed by a CPU.
Hereinafter, operations performed in each of nodes A through D having the above-mentioned configuration will now be described, assuming the signal input (
1
) (hereinafter
Fujitsu Limited
Katten Muchin Zavis & Rosenman
Trieu Van
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