Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-02-11
2001-10-16
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06304346
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fault restoration control method and apparatus thereof in a communication network, and in particular to a fault restoration control method suitable for a communication network using an optical cross-connect equipment for changing over from one optical fiber to another by using an optical switch.
Conventionally, in the case where a communication network was to be formed by using an optical fiber as a signal transmission line, an optical-electric signal converter and a line terminal equipment were disposed so as to be associated with each optical fiber in a node equipment for controlling communication. In the case where a transmission line fault such as degradation of characteristics of an optical fiber or breaking of an optical fiber occurred, the line terminal equipment detected that fault and changed the optical fiber over to a protection system.
Furthermore, in recent years, an equipment adapted to change over one optical fiber over to another by using an optical switch and called optical cross-connect equipment is disposed in the node equipment together with the line terminal equipment, and a communication network is formed by using such node equipments.
FIG. 11
is a block diagram showing an example of a communication network using optical cross-connect equipments according to a reference technique.
FIG. 12
is a block diagram showing the configuration of a node equipment.
FIG. 13
is a sequence diagram illustrating restoration operation from a fault in the communication network. With reference to
FIGS. 11 and 12
, N
1
through N
3
denote node equipments, LTE
1
through LTE
3
denote line terminal equipments, OXC
1
through OXC
3
denote optical cross-connect equipments, OF
12
, OF
13
and OF
23
optical fibers,
60
a fault detector,
61
an OXC change-over trigger generator,
62
an OXC change-over control signal transfer section,
63
a communication controller with respect to its own node OXC,
64
a communication controller with respect to other nodes,
65
a change-over route determining section,
66
an optical switch controller,
67
a change-over trigger acceptance section,
68
an other node information collector,
69
an other node OXC change-over request section, and
6
A a communication controller, and
6
B is equipment's own node information sending section.
The communication network shown in
FIG. 11
is formed by interconnecting the three node equipments N
1
through N
3
via the optical fibers OF
12
, OF
13
, and OF
23
serving as signal transmission lines. Although the illustrated communication network has three node equipments, a larger number of node equipments may be disposed and interconnected via optical fibers. As this communication network, any communication network may be used so long as at least two node equipments are interconnected by interconnection between the node equipments or optical cross-connect equipments. Each of the node equipments N
1
through N
3
is formed by a line terminal equipment LTE and an optical cross-connect equipment OXC as shown in FIG.
12
.
The line terminal equipment LTE has a control function of signal transmission between node equipments, and control functions such as commanding the optical cross-connect equipment to change one optical fiber over to another in response to degradation of characteristics of the optical fiber or breaking of the optical fiber. Specifically, the line terminal equipment LTE is formed so as to have the fault detector
60
, the OXC change-over trigger generator
61
, the OXC change-over control signal transfer section
62
, the communication controller
63
with respect to its own node OXC, and the communication controller
64
with respect to other nodes, as shown in FIG.
12
.
The optical cross-connect equipment OXC has a function of conducting a change-over of one optical fiber serving as a transmission line to another by switching an optical switch disposed therein in response to a command given by the line terminal equipment. Specifically, the optical cross-connect equipment OXC is formed so as to have the restoration route determining section
65
, the optical switch controller
66
, the change-over trigger acceptance section
67
, the other node information collector
68
, the other node OXC change-over request section
69
, the communication controller
6
A and equipment's own node sending section
6
B as shown in FIG.
12
.
The configuration of the line terminal equipment LTE and the optical cross-connect equipment OXC shown in
FIG. 12
represents only a configuration required for restoration from a fault. As for functions for the normal signal transmission, functions similar to the reference technique are provided.
It is now assumed in the node equipments configured as described above and a communication network including such node equipments that a node equipment N
1
and a node equipment N
2
transmit and receive a signal via an optical fiber OF
12
interconnecting them and the line terminal equipment LTE
1
included in the node equipment N
1
has detected occurrence of a fault in the optical fiber OF
12
. In this case, the line terminal equipment LTE
1
exchanges control information for restoration from the fault with other node equipments, thereby collects node information of other node equipments, and delivers the collected node information of other node equipments to the optical cross-connect equipment OXC
1
. The optical cross-connect equipment OXC
1
determines a transmission route, changes over the transmission line from the optical fiber OF
12
to another optical fiber, and conducts restoration from the fault.
Such an operation for restoration from a fault will now be described by referring to a sequence shown in FIG.
13
. It is now assumed that a fault has occurred in the optical fiber OF
12
interconnecting the node equipment N
1
and the node equipment N
2
when the node equipment N
1
and the node equipment N
2
are transmitting and receiving signals via the optical fiber OF
12
, and a route is then formed between the node equipment N
1
and the node equipment N
2
as a restoration route via the optical fiber OF
13
, the node equipment N
3
, and the optical fiber OF
23
.
FIG. 13
shows an example in such a case.
(1) Upon detecting the occurrence of a fault in the optical fiber OF
12
, the line terminal equipment LTE
1
in the node equipment N
1
requests the optical cross-connect equipment OXC
1
included in its own node equipment to change over from the optical fiber OF
12
. Upon receiving this request, the optical cross-connect equipment OXC
1
requests the line terminal equipment LTE
1
to collect node information (steps
701
and
702
).
(2) The line terminal equipment LTE
1
requests line terminal equipments of other node equipments, i.e., the line terminal equipments LTE
2
and LTE
3
respectively of the node equipments N
2
and N
3
in this case, to transfer the node information (steps
703
and
704
).
(3) Upon receiving the node information transfer request, the line terminal equipments LTE
2
and LTE
3
respectively of the node equipments N
2
and N
3
collects node information from the optical cross-connect equipments OXC
2
and OXC
3
of its own node equipment and transfer that node information to the line terminal equipment LTE
1
(steps
705
through
710
).
(4) The line terminal equipment LTE
1
delivers the transferred node information of the node equipments N
2
and N
3
to the optical cross-connect equipment OXC
1
included in its own node equipment as answer information. On the basis of each node information thus delivered, the optical cross-connect equipment OXC
1
determines a restoration route thereto. Together with the route information thus determined, the optical cross-connect equipment OXC
1
then transmits a change-over request to the line terminal equipment LTE
1
(steps
711
through
714
).
(5) The line terminal equipment LTE
1
commands the line terminal equipments LTE
2
and LTE
3
respectively of the node equipments N
2
and N
3
to conduct change-over op
Kanetake Tatsuo
Kitajima Shigeki
Sawada Yasushi
Tsushima Hideaki
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Pascal Leslie
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