U.S. patent application number 10/747137 was filed with the patent office on 2004-08-05 for optical node system and switched connection method.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Ibukuro, Sadao, Kuroyanagi, Satoshi, Yoshimura, Junichi.
Application Number | 20040151499 10/747137 |
Document ID | / |
Family ID | 18596280 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040151499 |
Kind Code |
A1 |
Ibukuro, Sadao ; et
al. |
August 5, 2004 |
Optical node system and switched connection method
Abstract
A protection switch is configured for an input optical signal
using an n.times.n optical switch. Furthermore, a signal to be
added and dropped is also configured using an n.times.n optical
switch. Especially, the n.times.n optical switch uses a complete
group switch. Thus, a signal can be output from any input port to
any output port. Therefore, a more extensible NPE can be configured
at an optical signal level, and a switch is simple and less
expensive. As a result, unlike the conventional technology, an NPE
itself can be simple and less expensive.
Inventors: |
Ibukuro, Sadao; (Kawasaki,
JP) ; Yoshimura, Junichi; (Kawasaki, JP) ;
Kuroyanagi, Satoshi; (Kawasaki, JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
18596280 |
Appl. No.: |
10/747137 |
Filed: |
December 30, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10747137 |
Dec 30, 2003 |
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09748863 |
Dec 28, 2000 |
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6697546 |
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Current U.S.
Class: |
398/45 |
Current CPC
Class: |
H04Q 2011/0081 20130101;
H04J 14/0283 20130101; H04J 14/0291 20130101; H04Q 11/0062
20130101; H04Q 2011/0092 20130101; H04J 14/0289 20130101; H04J
14/0297 20130101; H04J 14/0212 20130101; H04J 14/0295 20130101 |
Class at
Publication: |
398/045 |
International
Class: |
H04J 014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2000 |
JP |
2000-078949 |
Claims
What is claimed is:
1. An optical node system, comprising: a first node having a first
switch for switching each of a plurality of optical input channels,
outputting lights from a plurality of optical output channels, and
containing optical switching ports larger in number than the
optical input channels and the optical output channels; and a
second node having a second switch for switching each of a
plurality of optical input channels, outputting lights from a
plurality of optical output channels, and containing optical
switching ports larger in number than the optical input channels
and the optical output channels, wherein: an output port of the
second switch having no optical output channel is connected to an
input port of the first switch; and an output port of the first
switch having no optical output channel is connected to an input
port of the second switch.
2. An optical node system, comprising: a node having a switch
including a plurality of input ports and a plurality of output
ports with the plurality of input ports switchable to any of the
plurality of output ports; said input ports of the switch comprise
at least one port inputting a primary line and a standby line and a
port inputting a signal from another node; and said output ports of
the switch comprise at least one port outputting a primary line and
a standby line and a port outputting a signal to another node.
3. The system according to claim 1, wherein said switch is a
complete group switch.
4. The system according to claim 2, wherein said switch connects
the primary line of said input port is connected to the standby
line of said output port when the primary line of said output port
becomes faulty.
5. The system according to claim 2, wherein said switch has an
AD-DROP function.
6. The system according to claim 3, wherein said complete group
switch is connected to multiple stages.
7. The system according to claim 6, further comprising a
transponder reproducing a signal, wherein a standby network
appliance is connected to said transponder.
8. The system according to claim 6, wherein said complete group
switch comprises (4n+2s).times.(4n+2s) complete group switches
where n is a number of input and ports of an optical node, and s is
any positive integer, said complete group switches are connected
using 2n trunk line input ports, 2n trunk line output ports, 2n add
input ports, 2n drop output ports, and 2s input and output ports,
and a transponder for reproducing a signal is provided in the
input/output ports used for connecting said complete group
switches.
9. The system according to claim 8, further comprising a wavelength
demultiplexer wavelength-demultiplexing a wavelength-multiplexed
signal into signals of respective wavelengths, wherein after
reproducing a signal for each wavelength, the signal is input to
said complete group switch.
10. The system according to claim 9, wherein at least one of
wavelength-multiplexed signals is used for a standby line.
11. An optical node system, comprising: a node having a switch
including a plurality of input ports and a plurality of output
ports with the plurality of input ports switchable to any of the
plurality of output ports; said input ports of the switch comprise
at least one port inputting a primary line and a standby line and a
port inputting a signal from a branch terminal station connected to
a node; and said output ports of the switch comprise at least one
port outputting a primary line and a standby line and a port
outputting a signal to another node.
12. A method of connecting an optical node system, comprising:
providing an optical switch switching each of a plurality of
optical input channels, and outputting a light from a plurality of
optical output channel; providing a node in which an input/input
port of the optical switch comprises, in an input/output unit,
switching ports larger in number than the optical input channels
and the optical output channels; when a node of another network is
connected to the node, output ports of an optical switch of the
node having no optical output channels are connected to an input
port of the optical switch of the node of the other network, and
input ports of an optical switch of the node having no optical
input channels are connected to an output port of the optical
switch of the node or the other network.
13. An optical node system, comprising: a first node having a first
switch for switching each of a plurality of optical input channels,
outputting signals from a plurality of output channels, and
containing switching ports larger in number than the input channels
and the output channels; and a second node having a second switch
for switching each of a plurality of input channels, outputting
signals from a plurality of output channels, and containing
switching ports larger in number than the input channels and the
output channels, wherein: an output port of the second switch
having no output channel is connected to an input port of the first
switch; and an output port of the first switch having no output
channel is connected to an input port of the second switch.
14. A node system, comprising: a node having a switch including a
plurality of input ports and a plurality of output ports with the
plurality of input ports switchable to any of the plurality of
output ports; said input ports of the switch comprise at least one
port inputting a primary line and a standby line and a port
inputting a signal from another node; and said output ports of the
switch comprise at least one port outputting a primary line and a
standby line and a port outputting a signal to another node.
15. A method of connecting a node system, comprising: providing a
switch switching each of a plurality of input channels, and
outputting a signal from a plurality of output channel; providing a
node in which an input/input port of the switch comprises, in an
input/output unit, switching ports larger in number than the input
channels and the output channels; when a node of another network is
connected to the node, output ports of a switch of the node having
no output channels are connected to an input port of the switch of
the node of the other network, and input ports of a switch of the
node having no input channels are connected to an output port of
the switch of the node or the other network.
16. A method of connecting a node system, comprising: providing a
first switch for switching each of a plurality of optical input
channels, outputting lights from a plurality of optical output
channels, and containing optical switching ports larger in number
than the optical input channels and the optical output channels;
providing a second switch for switching each of a plurality of
optical input channels, outputting lights from a plurality of
optical output channels, and containing optical switching ports
larger in number than the optical input channels and the optical
output channels; connecting an output port of the second switch
having no optical output channel to an input port of the first
switch; and connecting an output port of the first switch having no
optical output channel to an input port of the second switch.
17. A method of connecting a node system, comprising: providing a
switch including a plurality of input ports and a plurality of
output ports with the plurality of input ports switchable to any of
the plurality of output ports; inputting to said input ports of the
switch at least one port inputting a primary line and a standby
line and a port inputting a signal from another node; and
outputting to said output ports of the switch at least one port
outputting a primary line and a standby line and a port outputting
a signal to another node.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a node connection structure
and a node structure appropriate for redundancy, and more
specifically to an optical node system and its switched connection
method.
[0003] 2. Description of the Related Art
[0004] Recently, a communications network using optical fiber has
been developed, and put into practical use. A typical trunk path of
an optical communications network is a ring network. Each unit of
the ring network is provided with a signal branch device for
transmitting an optical signal through the ring network to another
network or a signal termination device.
[0005] FIG. 1 shows the configuration showing the concept of a ring
network.
[0006] In FIG. 1, the signal division-multiplexing devices
indicated by characters A through I are also referred to as nodes
for connecting a ring network to one of another network and a
signal termination device. For example, when an optical signal is
input from another network to a node, the optical signal
transmitted through the ring network is multiplexed with an optical
signal input through another network, and transmitted to the ring
network. Each node extracts an optical signal to be dropped from
the optical signals transmitted through the ring network, and
transmits it to another network or a signal termination device.
[0007] The conventional signal division-multiplexing device (node)
extracts an optical signal through a predetermined specific path as
a signal to be dropped from the trunk path, and transmits it to
another network or a signal termination device. An optical signal
transmitted from another network or a signal transmission device
through a predetermined specific path is multiplexed by a signal
division-multiplexing device with a signal transmitted through a
trunk path, and transmitted to the trunk path. Such a signal
division-multiplexing device is referred to as an ADM device
(add/drop multiplexer which gathers signals from branch terminal
stations, etc. or branches signals from a trunk path to transmit
them to the branch terminal stations, etc.).
[0008] An ADM device is designed for redundancy to provide
continuously services even when it becomes faulty. To attain this,
a device referred to as an NPE (network protection equipment for
redundancy of a network) is installed. The function of the NPE is
incorporated into the conventional ADM device, and a protection
switch is switched through a protection path for transmission of a
signal.
[0009] Redundancy includes, in addition to switching a network
between a primary system and a standby system, configuring a system
0 and a system 1 for a switch and an appliance such as an output
sector of a switch, etc., providing redundancy for an appliance,
looping back or retrieving an output signal before or after a fault
of a ring network, etc.
[0010] As described above, the conventional ADM device is designed
to connect a specific input path to a specific output path, but is
not designed to connect all input paths to all output paths.
Therefore, a protection switch has only the minimal switching
function, and cannot correspond to newly extended functions of a
protection switch.
SUMMARY OF THE INVENTION
[0011] The present invention aims at providing an optical node
system having a simple configuration in which functions and
equipment can easily be extended.
[0012] A first optical node system according to the present
invention includes: a first node having a first switch for
switching each of a plurality of optical input channels, outputting
lights from a plurality of optical output channels, and containing
optical switching ports larger in number than the optical input
channels and the optical output channels; and a second node having
a second switch for switching each of a plurality of optical input
channels, outputting lights from a plurality of optical output
channels, and containing optical switching ports larger in number
than the optical input channels and the optical output channels.
With the configuration, an output port of the second switch having
no optical output channel is connected to an input port of the
first switch, and an output port of the first switch having no
optical output channel is connected to an input port of the second
switch.
[0013] The second optical node system according to the present
invention has a node having a switch including a plurality of input
ports and a plurality of output ports with the plurality of input
ports switchable to any of the plurality of output ports. The input
ports of the switch include at least one port inputting a primary
line and a standby line and a port inputting a signal from another
node. The output ports of the switch include at least one port
outputting a primary line and a standby line and a port outputting
a signal to another node.
[0014] With the first optical node system according to the present
invention, nodes can be easily interconnected using a switch, and
the system can be easily extended as necessary in the future.
[0015] With the second optical node system according to the present
invention, a node can be easily configured for redundancy using a
complete group switch of the node. A complete group switch refers
to a switch having a plurality of input ports and a plurality of
output ports, and can switch all the plurality of input ports to
all the output ports. Since a redundancy switch forms a complete
group, and any input can be connected to any output, a considerably
extensible switch can be configured. Especially, a costly and large
redundancy configuration using the conventional ADM device can be
improved into a smaller and less expensive configuration according
to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows the configuration of the concept of a ring
network;
[0017] FIG. 2 shows nodes A and B where n=2;
[0018] FIG. 3 shows an embodiment of the present invention;
[0019] FIG. 4 shows an embodiment of the ONPE according to the
present invention when ADD.multidot.DROP is not performed;
[0020] FIG. 5 shows the basic redundancy configuration according to
an embodiment of the present invention;
[0021] FIG. 6 shows an embodiment of a redundancy configuration on
the ADD side of the optical NPE according to the present
invention;
[0022] FIG. 7 shows another embodiment of a redundancy
configuration of an ADD port in an optical NPE according to the
present invention;
[0023] FIG. 8 shows the relation of monitor levels;
[0024] FIG. 9 shows the details of the relation of a threshold;
[0025] FIG. 10 shows a state in which a monitoring operation can be
performed;
[0026] FIG. 11 is a switch determination table (1) based on the
result of the monitors M.sub.4W and M.sub.5W on the ADD side;
[0027] FIG. 12 is a switch determination table (2) based on the
result of the monitors M.sub.4W and M.sub.5W on the ADD side;
[0028] FIG. 13 is a switch determination table (3) based on the
result of the monitors M.sub.4W and M.sub.5W on the ADD side;
[0029] FIG. 14 is a switch determination table (4) based on the
result of the monitors M.sub.4W and M.sub.5W on the ADD side;
[0030] FIG. 15 is a switch determination table (5) based on the
result of the monitors M.sub.4W and M.sub.5W on the ADD side;
[0031] FIG. 16 shows the configuration of a monitor on the DROP
side;
[0032] FIG. 17 is a switch determination table (1) based on the
detection result of the monitor on the DROP side;
[0033] FIG. 18 is a switch determination table (2) based on the
detection result of the monitor on the DROP side;
[0034] FIG. 19 is a switch determination table (3) based on the
detection result of the monitor on the DROP side;
[0035] FIG. 20 is a switch determination table (4) based on the
detection result of the monitor on the DROP side;
[0036] FIG. 21 is a switch determination table (5) based on the
detection result of the monitor on the DROP side;
[0037] FIG. 22 is a switch determination table (6) based on the
detection result of the monitor on the DROP side;
[0038] FIG. 23 is a switch determination table (7) based on the
detection result of the monitor on the DROP side;
[0039] FIG. 24 is a switch determination table (8) based on the
detection result of the monitor-on the DROP side;
[0040] FIG. 25 is a switch determination table (9) based on the
detection result of the monitor on the DROP side;
[0041] FIG. 26 is a switch determination table (10) based on the
detection result of the monitor on the DROP side;
[0042] FIG. 27 is a switch determination table (11) based on the
detection result of the monitor on the DROP side;
[0043] FIG. 28 is a switch determination table (12) based on the
detection result of the monitor on the DROP side;
[0044] FIG. 29 is a switch determination table (13) based on the
detection result of the monitor on the DROP side;
[0045] FIG. 30 is a switch determination table (14) based on the
detection result of the monitor on the DROP side;
[0046] FIG. 31 is a switch determination table (15) based on the
detection result of the monitor on the DROP side;
[0047] FIG. 32 is a switch determination table (16) based on the
detection result of the monitor on the DROP side;
[0048] FIG. 33 is a switch determination table (17) based on the
detection result of the monitor on the DROP side;
[0049] FIG. 34 is a switch determination table (18) based on the
detection result of the monitor on the DROP side;
[0050] FIG. 35 is a switch determination table (19) based on the
detection result of the monitor on the DROP side;
[0051] FIG. 36 is a switch determination table (20) based on the
detection result of the monitor on the DROP side;
[0052] FIG. 37 is a switch determination table (21) based on the
detection result of the monitor on the DROP side;
[0053] FIG. 38 is a switch determination table (22) based on the
detection result of the monitor on the DROP side;
[0054] FIG. 39 is a switch determination table (23) based on the
detection result of the monitor on the DROP side;
[0055] FIG. 40 is a switch determination table (24) based on the
detection result of the monitor on the DROP side;
[0056] FIG. 41 is a switch determination table (25) based on the
detection result of the monitor on the DROP side;
[0057] FIG. 42 shows an embodiment of the configuration of the
switch realizing the redundancy of an appliance;
[0058] FIG. 43 shows another embodiment of the configuration of the
switch realizing the redundancy of an appliance;
[0059] FIG. 44 shows an embodiment of the configuration of the
protection device to which the configuration shown in FIG. 42 is
practically applied;
[0060] FIG. 45 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 42 is
practically applied;
[0061] FIG. 46 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 42
is practically applied;
[0062] FIG. 47 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 42
is practically applied;
[0063] FIG. 48 shows an embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied;
[0064] FIG. 49 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied;
[0065] FIG. 50 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 43
is practically applied;
[0066] FIG. 51 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 43
is practically applied; and
[0067] FIG. 52 shows the entire network including the embodiments
shown in FIGS. 42 through 51.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] An embodiment of the present invention is applied to a ring
network as shown in FIG. 1. However, the present invention is not
limited to the ring network (shown in FIG. 1).
[0069] In the ring network shown in FIG. 1, a network can be
designed in a redundancy system with high flexibility when a
4n.times.4n complete group switch is installed among input ports to
a node, output ports of ADD ports and the node, and DROP ports
where the number of clockwise or counterclockwise outputs in each
node is n. ADD-DROP refers to a process, in a node connected to the
trunk path, of gathering signals transmitted from a terminal, etc.
outside the trunk path, branching a signal from the trunk path, and
transmitting a signal to a terminal, etc. outside the trunk path. A
complete group switch refers to a switch capable of
switch-connecting a signal input from any input port to any output
port. The control in a redundancy system can be configured by
switch-connecting a complete group switch from the port to which an
input of the primary system is connected to the port to which an
output of the standby system is connected.
[0070] FIG. 2 shows nodes A and B when n=2 with a 4n.times.4n
complete group switch. Since the number n of clockwise outputs is 2
(n=2), for example, the numbers of clockwise, counterclockwise and
DROP port outputs are respectively 2, 2, and 4, that is, a total of
8.
[0071] In this concept, the `MS shared protection ring` and the `MS
shared protection ring (transoceanic application) described in
ITU-T G841 (the Recommendation published by ITU (International
Telecommunication Union) as a worldwide standard) are also based on
n=2. That is, with the configuration shown in FIG. 2, the
protection ring described in the Recommendation by ITU can be
configured. By limiting the switching method corresponding to an
occurrence of a fault to the method of an MS shared protection
ring, an MS shared protection ring can be configured. By limiting
the switching method corresponding to an occurrence of a fault to
the method of an MS shared protection ring (transoceanic
application), an MS shared protection ring (transoceanic
application) can be configured.
[0072] Since a complete group switch is used, a flexibility level
is very high. When a test is conducted as to whether or not a path
can be completely connected, etc. during the production of the
device, a path can be freely set for the test. Any connection is
allowed as long as an input and an output of the 4n.times.4n
complete group switch can be correctly set.
[0073] That is, according to the embodiment shown in FIG. 2, an
AD.multidot.DROP function and a protection function can be
simultaneously realized using a 4n.times.4n complete group
switch.
[0074] ADD ports 1 and 2 in nodes A and B receive signals of user
data and control data transmitted from a signal transmission device
(a user terminal, etc.) and a node of another network. A signal
input from the ADD port 1 is output to a path (A2), (B3) or a DROP
port 1 in the node A. In addition, a signal input from the ADD port
2 is output to a path (A3), (B2), or a DROP port 2 in the node B.
Signals transmitted to the paths (A2), (A3), (B2), and (B3) become
primary signals transmitted through a ring network. In addition to
the signals input from the ADD ports 1 and 2, a part of the signals
of the user data, the control data, etc. input from the paths (A1),
(B2), (B1), and (A2) are input from the ring network. The signals
output from the DROP ports 1 and 2 are transmitted to a signal
termination device such as a user terminal, etc. and a node of
another network such as a router, etc.
[0075] When there are no errors, a signal passes through a node,
adds a signal input from another network of a signal transmission
device, or drops a signal to another network or a signal reception
device.
[0076] For example, a signal passing through the node A and the
node B is input from the path (A1) to the input port of the node A,
output from the output port, and transmitted to the path (A2). When
it is input to the input port of the node B through the path (A2),
it is output from the output port of the node B to the path (A3).
Thus, a through signal is transmitted from the node A to the node
B. Similarly, a through signal from the node B to the node A is
transmitted through, for example, the paths (B1), (B2), and
(B3).
[0077] In the node A, a signal input from the ADD port 1 is output
to the path (B3) or the path (A2). A part of the signals input from
the path (A1) or the path (B2) is output from the DROP port 1.
Similarly, in the node B, a signal input from the ADD port 2 is
output from the path (A3) or the path (B2), and a part of the
signal input from the path (A2) or the path (B1) to the node B is
output to the DROP port 2. Since a complete group switch is used,
the ADD port, A1, and A2 can output a signal to any of the B3, DROP
port, and A1.
[0078] Described below is a case in which an error occurs.
[0079] When a signal cannot be transmitted through the path (A2),
the path (B2), or these two paths due to a line disconnection,
etc., a protection function can be attained by connecting the path
(A1) to the path (B3), by connecting the path (B1) to the path
(A3), or by connecting both of them. That is, a signal cannot be
transmitted in the direction of a line disconnection, but a signal
is transmitted through a loop in a node adjacent to a transmission
path where a line disconnection has arisen, and a bypass transfer
is performed in a ring network, thereby realizing a protection
function. A protection function refers to a function for recovery
from an error using another device or line with the faulty unit
avoided using a method of providing a primary line and a standby
line, or bypassing a signal in a ring circuit.
[0080] With the configuration shown in FIG. 2, a ring network can
be extended. That is, the node A is a node of the first ring
network, and the ring network is connected through the ADD port 1
and the DROP port 1. Similarly, the node B is a node of the second
ring network different from the first ring network, and the second
ring network is connected to the ADD port 2 and the DROP port 2 of
the node B. In this case, the paths (A2) and (B2) connect the nodes
of the different networks, thereby transmitting and receiving
signals between the different networks through the paths (A2) and
(B2). That is, using the switch with the configuration shown in
FIG. 1, nodes of different networks can be interconnected, and the
number of networks can be increased.
[0081] FIG. 3 shows an embodiment of the present invention.
[0082] The case shown in FIG. 3 is described below by referring to
an example of an optical NPE (ONPE) using an optical switch. The
configuration according to the present embodiment can also be
realized using an electric switch.
[0083] According to the present embodiment, the number of lines
input to the ONPE, and the number of lines output from the ONPE are
n, and half of them is used as standby lines. In this case, an NPE
can be configured by a 3n.times.3n complete group switch and a 2:1
selector switch.
[0084] FIG. 3 shows the configuration of the case in which n=2. In
FIG. 3, six ports are used as inputs to, and six ports are used as
outputs from an optical switch (6.times.6 OSW) 10. That is, the
output n in the clockwise or counterclockwise direction in a ring
network is 2, but a 3n.times.3n complete group switch is a
6.times.6 complete group switch. In FIG. 2, there are respectively
four AD.multidot.DROP inputs and outputs. In FIG. 3, there are two
AD.multidot.DROP inputs and output to the clients TE1 and TE2.
Therefore, there are six outputs, that is, four outputs of the ring
network and the clients TE1 and TE2, from the complete group switch
10. Transponders W1 and W2 are signal regenerators provided in the
primary line, and input and output signals from the primary line. A
transponder refers to a device for converting an input optical
signal into an electric signal, regenerating a signal, converting
it into an optical signal, and converting and outputting the
wavelength and the bit rate of a signal. Transponders P1 and P2 are
signal regenerators provided in the standby line, and input and
output a signal from the standby line. A client PCA refers to
protection channel access for transmitting and receiving a signal
for transmission through a protection transmission line when the
primary line is normally used. When the primary line is normally
used, the standby line is not busy. Therefore, low priority
information is transmitted between nodes while the primary line is
not switched to the standby line so that the resources as a
transmission medium in the standby line can be effectively
used.
[0085] The MS shared protection rings and the MS shared protection
ring (transoceanic application) can be used with the above
mentioned configuration.
[0086] That is, a signal transmitted through the primary line is
input to the transponder W1, for example. The signal in the primary
line input from the transponder W1 to the 6.times.6 OSW 10 passes
through the 6.times.6 optical switch (OSW), and is transmitted as
is to the transponder W2, or transmitted to the client TE1
(terminal equipment) or TE2 when there is no error. The signal
input to the transponder W2 is transmitted again to the primary
line of the ring network. A client TE refers to a network client,
transmits and receives a signal carrying information for
communications, etc., and can be a user terminal, etc. A user
terminal transmits and receives data such as a document, an image,
etc. to be transmitted as a signal, and is switched and connected
to a trunk line of a ring network using the 6.times.6 OSW 10 so
that data can be transmitted to a destination user or received from
a source user. Similarly, a signal in the primary line input
through the transponder W2 is transmitted to the transponder W1,
the client TE1, or TE2. As described above, when there are no
error, the signal input from the transponder W2 passes through the
6.times.6 OSW 10, then it is transmitted to the transponder W1, and
transmitted from the transponder W1 to the primary line. The signal
input from the transponder W2 is otherwise input to the input port
of the 6.times.6 OSW 10, the 6.times.6 OSW 10 switches and connects
the signal, and the signal is output from the output port, and is
then transmitted to the client TE1 or TE2. The client TE1 or TE2
can be, for example, a user terminal as described above.
[0087] When there is no error in the primary line, a signal is
transmitted from the clients PCA1 and PCA2 through selectors SEL1
and SEL2 to the standby line to which the transponders P1 and P2
are connected. At this time, the transponders P1 and P2 convert the
input optical signal into an electric signal, regenerate a signal,
etc., convert it into an optical signal again, and then transmits
it to the standby line. The signal transmitted through the standby
line is input to the transponders P1 and P2, and is regenerated as
described above, and switches SW1 and SW2 transmit the signal to
clients PCA1 and PCA2.
[0088] The signal transmitted to the standby line when there is no
error in the primary line cannot be transmitted as a low priority
signal when there occurs an error in the primary line. For example,
when an error occurs on the transponder W2 side, an important
signal transmitted through the primary line to be input from the
transponder W1 to the optical switch (6.times.6 OSW) 10 is switched
and connected by the optical switch (6.times.6 OSW) 10, and is
output to the port to which the selector SEL2 is connected. Since
the signal from the client PCA2 is a low priority signal, the
selector SEL2 determines that the signal in the primary line
containing user data is more important, selects the signal
transmitted from the transponder W1, and transmits it to the
transponder P2. Since an error has occurred on the transponder W2
side, a signal to be transmitted from the transponder W2 is
transmitted from the transponder P2 through the standby line. Then,
a switch SW2 inputs the signal not to the client PCA2, but to the
input port of the optical switch (6.times.6 OSW) 10. The optical
switch (6.times.6 OSW) 10 switches and connects the signal input
from the switch SW2 so that it can be input to the transponder W1
connected to the output port of the optical switch (6.times.6 OSW)
10.
[0089] Using the optical switch (6.times.6 OSW) 10 of a complete
group, A protection switch can be easily configured. Especially,
when there are two upstream and downstream primary lines, two
upstream and downstream standby lines as shown in FIG. 3, and two
clients TE, the optical switch (6.times.6 OSW) 10 can be a
6.times.6 optical switch. Thus, an optical protection switch (ONPE
11) can be configured with a less expensive and simple structure
obtained by adding a switch and a selector to the above mentioned
6.times.6 optical switch.
[0090] FIG. 4 shows an embodiment of the ONPE according to the
present invention when no AD.multidot.DROP is used.
[0091] When no AD.multidot.DROP is used as shown in FIG. 4, a
2n.times.2n switch can be used. Especially, FIG. 4 shows the
configuration where n=2. In FIG. 4, it is assumed that an optical
switch is used, but an electric switch can also be used.
[0092] Normally, when there is no error, the transponder W1 to
which the primary line is connected first regenerates the optical
signal input from the primary line, and inputs it through the line
connected to the input port of an optical switch (4.times.4 OSW)
12. The optical signal input to the optical switch (4.times.4 OSW)
12 passes through the optical switch (4.times.4 OSW) 12, and is
transmitted to the transponder W2 connected to the output port of
the optical switch (4.times.4 OSW) 12, regenerated by the
transponder W2, and transmitted to the primary line. Similarly, the
signal input from the transponder W2 through the primary line is
input to the optical switch 12 through the line connected to the
input port of the optical switch 12, passes through the optical
switch (4.times.4 OSW) 12, and is transmitted to the transponder W1
connected to the output port of the optical switch 12, regenerated,
and then transmitted to the primary line. The signal input from the
transponder P1 of a standby system to an ONPE 13 is normally input
to the client PCA1 through the switch SW1. The signal transmitted
from the client PCA1 is transmitted to the transponder P1 through
the selector SELL. Since there is no error, the clients PCA1 and
PCA2 transmit the low priority data signal to the free standby line
as described above.
[0093] Similarly, in a normal operation, the signal input from the
transponder P2 to the ONPE 13 through the standby line is input to
the client PCA2 through the switch SW2, and the signal transmitted
from the client PCA2 is transmitted to the transponder P2 through
the selector SEL2# and then to the standby line.
[0094] If an error occurs on the transponder W2 side, the signal
input from the transponder W1 to the ONPE 13 through the primary
line is connected to the input port of the optical switch 12,
switched and connected by the optical switch (4.times.4 OSW) 12,
and then output to the selector SEL2. The selector SEL2 switches
the signal from the client PCA2, transmits the signal from the
optical switch (4.times.4 OSW) 12 to the transponder P2, and
transmits the signal through the standby line. In addition, since
there is an error in the transponder W2, the signal from the
transponder W2 is output from the transponder P2 through the
standby line. The signal output from the transponder P2 is
connected to the switch SW2, and input to the switch SW2. Then, it
is input not to the client PCA2, but to the input port of the
optical switch (4.times.4 OSW) 12. The signal is switched and
connected by the optical switch (4.times.4 OSW) 12, transmitted
from the output port of the optical switch 12 to the transponder
W1, regenerated, and then transmitted through the primary line.
[0095] When the transponder W2 normally operates, and the
transponder W1 becomes faulty, the signal from the transponder W2
is transmitted to the transponder P1, and the signal from the
transponder P1 is transmitted to the transponder W2.
[0096] When an error occurs as described above, the signal in the
primary line is transferred to the standby line, and the signal
transmitted and received by the clients PCA1 and PCA2 are discarded
as being insignificant.
[0097] Described below is system based on, but is not limited to, a
submarine optical communications system.
[0098] The configuration of the transponder is the same as the
configuration of the conventional system. Therefore, the redundancy
of the transponder is designed using a span switch. A span switch
is a switch for bypassing the primary line which has become faulty
by switching the signal transmission direction from the primary
line to the standby line from west to east as is in a ring
network.
[0099] FIG. 5 shows the configuration of basic redundancy according
to an embodiment of the present invention.
[0100] FIG. 5 shows an example of configuring the optical NPE
having the AD-DROP configuration using a 4n.times.4n, that is, an
8.times.8 switch.
[0101] The signal input from the transponder W1 on the primary line
side through the primary line is input to a distributor 17-1. The
distributor 17-1 distributes the signal from the transponder W1 to
an optical switch (8.times.8 OSW) 20 developed into systems 0 and 1
for redundancy. When a signal is switched, connected, and passes
through by the optical switch (8.times.8 OSW) 20 of either system 0
or 1, it is output to a selector 18-3. The selector 18-3 selects a
signal output from the optical switch (8.times.8 OSW) 20 of either
system 0 or 1, and outputs the selected signal to the transponder
W2. In this case, a switch to the standby system or an
AD.multidot.DROP process is not performed.
[0102] When the AD-DROP is performed, the signal from the
transponder W1 is transmitted by the optical switch (8.times.8 OSW)
20 to clients TE15-1 and TE15-2. In this case, the client TE has
both systems 0 and 1. A signal transmitted through the optical
switch of the system 0 is received by a device of the system 0
while a signal transmitted through the optical switch of the system
1 is received by a device of the system 1. Signals transmitted from
the clients TE15-1 and TE15-2 are output from the devices of the
system 0 and the system 1 respectively, and output to the optical
switch (8.times.8 OSW) 20 of the system 0 and the optical switch
(8.times.8 OSW) 20 of the system 1 respectively. Then, the signals
are input by the optical switch (8.times.8 OSW) 20 to either
selector 18-1 or 18-3, and transmitted to the transponder W1 or
W2.
[0103] In the normal operation, signals from clients PCA 16-1 and
16-2 are input to the input ports of the optical switch (8.times.8
OSW) 20, switched and connected, transmitted from the output ports
to the transponders P1 and P2 provided in the standby line. The
signals from the transponders P1 and P2 are transmitted to the
clients PCA 16-1 and 16-2. The clients PCA 16-1 and 16-2 are
provided with the devices of the systems 0 and 1. The signals from
the clients PCA1 and PCA2 of the system 0 are input to the optical
switch (8.times.8 OSW) 20 of the system 0, and the signals from the
clients PCA1 and PCA2 of the system 1 are input to the optical
switch (8.times.8 OSW) 20 of the system 1. Selectors 18-2 and 18-4
outputs any of the signals output from the optical switch
(8.times.8 OSW) 20 of the systems 0 and 1 to the transponder P1 or
P2.
[0104] Distributors 17-2 and 17-4 input a signal from the
transponder P1 or P2 to the input port of the optical switch
(8.times.8 OSW) 20 of the system 0 or 1.
[0105] When the transponder W2 becomes faulty, a signal from the
transponder W1 is switched and connected by the optical switch
(8.times.8 OSW) 20, output to the transponder P2 side, and the
signal from the transponder P2 is transmitted to the transponder
W1. In this case, the signals transmitted from the clients PCA 16-1
and 16-2, or the signal to be transmitted to them are discarded.
Thus, the optical switch (8.times.8 OSW) 20 can function as a span
switch.
[0106] Furthermore, since the optical switch (8.times.8 OSW) 20 is
a complete group switch, it can transmit the signals from the
clients TE15-1 and TE15-2 to the transponders W1, W2, P1, and P2.
The configuration is referred to as a ring switch function.
[0107] When both transponders W2 and P2 are faulty and inoperable,
a signal from the transponder W1 can be connected to the
transponder P1 by switch-controlling the optical switch (8.times.8
OSW) 20 for a loop switch function because the entire network is a
ring network.
[0108] In FIG. 5, a reference character `M` denotes a monitor for
detecting whether or not an optical signal is correctly
transmitted, and for detecting a fault in the optical switch
(8.times.8 OSW) 20 of the systems 0 and 1.
[0109] FIG. 6 shows an embodiment of the redundancy configuration
on the ADD side of the optical NPE according to the present
invention.
[0110] With the configuration shown in FIG. 6, a client TE21 is
provided with devices of the systems 0 and 1 each of which outputs
a signal. With the configuration shown in FIG. 6, unlike the
configuration shown in FIG. 5, the signals from the systems 0 and 1
among the signals from the client TE21 are branched and input to
the optical switch (4n.times.4n complete group switch) 20 of the
systems 0 and 1. In the 4n inputs, n inputs are the signals of the
system 0 from the client TE21, and another n inputs are signals to
the add port of the 4n.times.4n complete group switch 20 from the
system 1 of the client TE21. Other 2n inputs are the signals from a
trunk path not shown in the attached drawings. The trunk path
comprises a primary system and a standby system. N output ports are
used as standby system lines, 2n ports are used as standby system
lines, and another 2n ports are used as drop ports.
[0111] Thus, the signal from the client TE21 input to the optical
switch (4n.times.4n complete group switch) 20 is added to the trunk
path, and transmitted to selectors 27 and 28.
[0112] In this case, for example, a signal output from the device
of the system 0 of the client TE21 is switched and connected to be
input to the selector 27, and a signal output from the device of
the system 1 of the client TE21 is switched and connected to be
input to the selector 28. The selector 27 is an exchange of the
systems 0 and 1 in the primary line, and the selector 28 is an
exchange of the systems 0 and 1 in the standby line.
[0113] The selectors 27 and 28 select a signal to be transmitted
from either system 0 or system 1 of the optical switch (4n.times.4n
complete group switch) 20, and outputs the selected signal to
selectors 29 and 30. The selectors 27 and 28 are controlled by a
control circuit not shown in the attached drawings.
[0114] The signals selected by the selectors 27 and 28 are input to
the selectors 29 and 30. The selectors 29 and 30 transmit the
signal from the optical switch (4n.times.4n complete group switch)
20 to a transponder 23 or 24 when the primary line normally
operates. At this time, the selectors 29 and 30 select and output
the signal from a client PCA 22 to input it to the transponder 23
or 24 which is the standby line. The client PCA 22 can transmit a
signal to the transponders 23 and 24. The line connected to either
transponder 23 or 24 can be alternately the primary line and the
standby line. That is, when either of the lines transmits a primary
signal, and the line is not faulty, the signal of the client PCA 22
can be transmitted to the other line.
[0115] The transponders 23 and 24 temporarily convert a received
optical signal into an electric signal, perform a signal
regenerating process, reconvert it into an optical signal, and
output the result to the respective lines. Assuming that the
primary line is connected to the transponder 23, and the standby
line is connected to the transponder 24, a signal from the client
TE21 is output from the transponder 23, and a signal, from the
client PCA 22 is output from the transponder 24.
[0116] If the primary line (line connected to the transponder 23)
or the transponder 23 itself has become faulty, then the optical
switch (4n.times.4n complete group switch) 20 switches and connects
a signal from the client TE21 to output it to the selector 28. The
selector 30 connected to the client PCA 22 and the optical switch
20 inputs the signal from the optical switch (4n.times.4n complete
group switch) 20, not the signal from the client PCA 22, to the
transponder 24, thereby protecting the line against an error. If
the line connected to the transponder 23 or the transponder 23
itself has recovered from an error, the signal from the optical
switch (4n.times.4n complete group switch) 20 remains as is, and
the signal from the client PCA 22 is selected by the selector 29,
and output from the transponder 23.
[0117] Thus, the previous standby line now functions as a primary
line, and the previous primary line which has become faulty
functions as a standby line.
[0118] The signal from the client PCA 22 is transmitted only to the
line connected to the transponder 24. If the transponder 23 has
recovered from an error, the signal from the client TE21 can be
controlled to be transmitted from the transponder 23. This process
is commonly known as a recovery process.
[0119] The selectors 27 and 28 are set such that either system 0 or
system 1 of the optical switch (4n.times.4n complete group switch)
20 can be selected. However, the optical switch (4n.times.4n
complete group switch) 20 is configured for redundancy such that,
for example, if both selectors 27 and 28 select the system 0, and
the system 0 of the optical switch (4n.times.4n complete group
switch) 20 become faulty, then the signal from the system 1 of the
optical switch (4n.times.4n complete group switch) 20 can be
switched and connected for use.
[0120] Furthermore, the client TE21 is also provided with the
systems 0 and 1 for redundancy such that, if the device of the
system 0 has become faulty when the signal of the system 0 is
transmitted to the primary line, then the optical switch
(4n.times.4n complete group switch) 20 switches and connects the
signal from the system 1 of the client TE21 for transmission to the
primary line.
[0121] In FIG. 6, monitors 25 and 26 expressed by `M`, and monitors
expressed by Ms with subscripts obtain information for
determination whether or not it is necessary to switch the primary
line, the standby line, the optical signal, and the system 1 by
measuring the level of the transmitted signal, and control the
selectors 27, 28, 29, 30, etc. The control is performed by the
control circuit not shown in the attached drawings, and described
later in detail.
[0122] FIG. 7 shows another embodiment of the redundancy
configuration of the ADD port in the optical NPE according to the
present invention.
[0123] In the present embodiment, an ADD signal transmitted from
the device of the system 0 of the client TE21 is input to the
optical switch (4n.times.4n complete group switch) 20 of the system
0, and an ADD signal transmitted from the device of the system 1 of
the client TE21 is input to the optical switch (4n.times.4n
complete group switch) 20 of the system 1.
[0124] In the normal operation, the ADD signal transmitted from the
system 0 of the client TE21 passes through the optical switch
(4n.times.4n complete group switch) 20 of the system 0, and is
input to the selector 35, and the ADD signal transmitted from the
system 1 of the client TE21 passes through the optical switch
(4n.times.4n complete group switch) 20 of the system 1, and is
input to the selector 35.
[0125] With this configuration, there arises a room in the number
of ports of the optical switch (4n.times.4n complete group switch)
20. Therefore, for example, 2n ports are used for input both
clockwise and counterclockwise of the primary line, 2n ports are
used for output both clockwise and counterclockwise of the primary
line, and the remaining 2n ports connect ADD or DROP lines.
However, since it is rare that all 2n ports are used for ADD and
DROP lines, the signal from a client PCA 22a can also be processed
by the optical switch (4n.times.4n complete group switch) 20. It is
rare that all 2n ports are used because the number of lines of the
primary lines of the trunk paths for transmitting signals to all
nodes is n clockwise or counterclockwise while the ADD/DROP node is
one of a plurality of nodes, thereby not dropping all lines to the
node or adding it to all lines. In this case, the signal
transmitted from the system 0 of the client PCA 22a is input to the
optical switch (4n.times.4n complete group switch) 20 of the system
0, the signal transmitted from the system 1 of the client PCA 22a
is input to the optical switch (4n.times.4n complete group switch)
20 of the system 1, and each of them is input to a selector 36.
[0126] The control circuit not shown in the attached drawings
determines a signal transmitted from the system 0 of the optical
switch or the system 1 of the optical switch for input to the
transponders 23 and 24 based on the detection result of the
monitors of the optical signals expressed by the Ms with subscripts
as shown in FIG. 7, and controls selectors 35 and 36.
[0127] In the normal operation, a signal from the client TE21 is
transmitted to the primary line, and a signal from the client PCA
22a is transmitted to the standby line. When the primary line
becomes faulty, the signal from the client TE21 is output to the
selector 36 by the optical switch (4n.times.4n complete group
switch) 20, and transmitted to the standby line.
[0128] In this case, the signal of the client PCA 22a is discarded
as an insignificant signal. If the primary line has recovered from
an error, then the signal from the client TE21 is input again to
the transponder 23, and the signal from the client PCA 22a can be
input to the transponder 24, or the signal from the client TE21 is
held as is, and the signal from the client PCA 22a can be input to
the transponder 23.
[0129] Described below is the switch determining process on the ADD
side.
[0130] In the following explanation, the system shown in FIG. 7 is
described, but the case shown in FIG. 6 can also be easily realized
in a practical processing method by one of ordinary skill in the
art.
[0131] The monitors other than the monitors M.sub.4W, M.sub.5W,
M.sub.4P, and M.sub.5P are optical level monitor. The M.sub.4W and
M.sub.4P are signal disconnection monitors for an O/E or an optical
amplifier, M.sub.5W and M.sub.P are the SF and SD bytes of the SDH
(SDH is short for synchronous digital hierarchy which is a standard
of an optical communications network used in Japan, etc. The SF and
SD bytes are contained in the header of the frame forming data
prescribed by the SDH, and to contains the information for monitor
of a system) for detecting a logical sum.
[0132] A package error and a missing package in the transponders 23
and 24 are to be a switch trigger, but are not specifically
discussed here. The determination control to process as a switch
trigger a fault in a package unit forming appliances of the
transponders 23 and 24, or a missing package, that is, no package
of an appliance to be provided with, etc. can be easily realized by
one of ordinary skill in the art only by referring to the present
embodiment.
[0133] An optical level monitor cannot appropriately perform a
determining process using only one threshold. That is, a switch
trigger sensitively reacts with small loss fluctuation of a portion
if there is only one threshold, thereby obtaining an unreasonable
detection result.
[0134] Therefore, according to the present embodiment, two
thresholds are set for the optical level monitor. One threshold is
set for a level (for example, 3 dB down) lower than the optical
level at which an alarm is raised that an input optical level is
low. This value depends on the optical loss deviation or
fluctuation.
[0135] FIG. 8 shows the relationship among monitor levels.
[0136] In FIG. 8, the switch trigger on the reception side of a
transponder includes a certain margin. A high level indicates a
level at which the switch trigger does not work, and a low level
indicates a level at which the switch trigger works without
fail.
[0137] The method of setting the threshold shown in FIG. 8 is an
example. That is, the difference a1 between the transponder input
level in the normal operation and the upper limit of the receiving
side switch trigger issue threshold of the transponder is set to be
equal to the difference a2 between the monitor level in the normal
operation of the optical level monitor Mxxx and the high level
threshold of the Mxxx monitor. Similarly, the difference b1 between
the transponder input level in the normal operation and the lower
limit of the receiving side switch trigger issue threshold of the
transponder is set to be equal to the difference b2 between the
monitor level in the normal operation of the Mxxx monitor and the
low level threshold of the Mxxx monitor. The transponder receiving
side switch trigger issue threshold corresponds to the value
between the Mxxx monitor high level threshold and the Mxxx monitor
low level threshold. When a normal value of the Mxxx monitor level
is larger than the high level threshold of the Mxxx monitor, the
Mxxx monitor does not issues an abnormal status. Since the Mxxx
monitor and the monitor M of the transponder observe the same
optical signal transmitted through a transmission line, the Mxxx
monitor level becomes smaller than a normal value when the
transponder input level becomes smaller than the normal value, and
their reduction values are substantially proportional to each
other. Therefore, when a transponder reception switch trigger
works, and the Mxxx monitor normally operates as an appliance, a
signal informing that an error has occurred is generated.
[0138] FIG. 9 shows the details of the correspondence among
thresholds.
[0139] FIG. 9 shows the relative relation among the monitor
thresholds observed from a certain view point.
[0140] FIG. 10 shows the status of the monitor when a monitor
circuit normally operates. The threshold of each optical level
monitor is not constant, .smallcircle. and .DELTA. simultaneously
exist, and .DELTA. and .times. simultaneously exist. .smallcircle.
indicates that the optical level is higher than the threshold of
the high level. .DELTA. indicates that a light having a level
higher than the threshold of the low level but lower than the high
level has been input. .times. indicates that a light having a level
lower than the low level has been input.
[0141] The switch determination of an important line is described
below. The switch determination and the switch of a selector based
on the switch determination are performed by the control circuit
not shown in FIGS. 6 and 7.
[0142] The monitors M.sub.4W and M.sub.5W of the transponder are
used as a switch trigger. Then, a switching method is determined by
observing an upstream monitor (on the optical switch side).
[0143] FIGS. 11 through 15 show a switch determination table based
on the results detected by the monitors M.sub.4W and M.sub.5W with
the configuration on the ADD side shown in FIG. 7.
[0144] FIG. 11 shows a protection line selected as a transient
status. However, it is more appropriate to reduce wasteful
determination by taking a protection time after a switching
process, and reading a work line replacing a protection line
without a recovery process. In this case, a bi-directional switch
is required.
[0145] When the work line does not replace the protection line, a
switching process is performed by referring to FIGS. 14 and 15.
When the work line can recover from the error, a protection period
is taken for a recovery process.
[0146] First, the status 1 shown in FIG. 11 shows the detection
status of the monitor of the line through which a signal is
transmitted from the device of the system 0 of the client TE21, and
the determining method when the 4n.times.4n complete group switch
20 uses a work line in transmitting a signal from the client TE21
as shown in FIG. 7. FIG. 12 is a switch determination table.
[0147] In FIG. 12, when all monitors M.sub.3W, M.sub.02W, and
M.sub.01 are .smallcircle., that is, when the status 1 shown in
FIG. 10 is entered (the optical level is higher than the threshold
of the high level), the monitors M.sub.3W, M.sub.02W, and M.sub.01
provided in the ONPE normally operate although the switch trigger
works from the monitors M.sub.4W and M.sub.5W of the transponder
23. Therefore, as described in the determination column shown in
FIG. 12, it is determined that the ONPE comprising the 4n.times.4n
complete group switch 20, a 2:1 selectors (switch) 35 and 36
normally operate, but the transmission line between the ONPE and
the transponder 23 is faulty.
[0148] In this case, as described in the column `switch-to target`
of No.1 shown in FIG. 12, the line selection of the 4n.times.4n
complete group switch 20 is set as `protection`, thereby
transferring control to the status 3 shown in FIG. 11. That is, the
4n.times.4n complete group switch 20 outputs the signal of the
system 0 of the client TE21 to the line to which the monitor M02P
is connected. The switch (2:1 selector) 36 transmits it to the
transponder 24, and transmits the signal from the client TE21 to
the protection line.
[0149] When control is transferred to the determination of the
status 3 shown in FIG. 11, and the switch trigger is not applied
from the monitors M.sub.4P and M.sub.5P, the protection line is
normal. Therefore, it transmits the signal from the client TE21 of
the system 0.
[0150] Thus, any of the tables shown in FIGS. 11 through 15 is
selected for detection of a monitor and determination depending on
`work` or `protection` for the line selection of the 4n.times.4n
complete group switch 20 for use in transmitting a primary signal
when the switch trigger occurs from the transponder 23 or the
transponder 24 shown in FIG. 7, and depending on `system 0` or
`system 1` of the 2:1 selectors 35 and 36, the error occurrence
status and the control are read from the corresponding line on each
table from the status of each of the monitors M.sub.01, M.sub.11,
M.sub.02W, M.sub.12W, M.sub.3W, M.sub.02P, M.sub.12P, and M.sub.3P,
and the 4n.times.4n complete group switch 20 and the 2:1 selectors
35 and 36 are controlled to recover from the error. The tables are
actually stored on memory provided in the control circuit as
electronic data such that the control circuit not shown in the
attached drawings can automatically read them, and the control
circuit can refer to them as necessary to control the ONPE.
[0151] Described below is the switch determination on the DROP
side.
[0152] FIG. 16 shows the configuration of the monitor on the DROP
side.
[0153] An M.sub.OW is an output monitor of a transponder 40, and
M.sub.1X, M.sub.2XX, M.sub.3XX, and M.sub.4X (X commonly indicates
the subscript added to the name of the monitors shown in FIG. 16)
are optical level monitors, have two thresholds, and the thresholds
are similarly set.
[0154] The configuration is set such that a work line or a
protection line can be used and the systems 0 and 1 of the
4n.times.4n complete group switch 20 can be switched for recovery
from an error.
[0155] The FERF (far end received failure) stored in the header
portion of the SDH frame of the optical signal from a network
client (client TE, etc.) is used as a switch trigger. The FERF is a
fault detecting byte stored in the SDH frame, and is used for
detecting whether or not a fault has occurred by the client TE
detecting the FERF contained in the header portion of the frame of
the SDH.
[0156] A transponder optical output monitor, a missing transponder,
a failure of a transponder can also be switch triggers, but they
are not described here for simple explanation. When a device is
practically designed, these switch triggers are to be considered,
and they will be easily controlled by one of ordinary skill in the
art.
[0157] The FERFs are retrieved from the headers of the signals
input to transponders 40 and 41 to determine where or not there is
a fault.
[0158] The signals output from the transponders 40 and 41 are input
to an optical switch (4n.times.4n complete group switch) 42 of the
systems 0 and 1. Then, they are dropped by the optical switch 42,
and the signals from the optical switch 42 of the systems 0 and 1
are respectively input to the selectors 43 and 44. Selectors 43 and
44 are controlled by the control circuit not shown in the attached
drawings, a signal input from any of the systems of the optical
switch (4n.times.4n complete group switch) 42 is selected and
output, and input to the device of the system 0 or the system 1 of
the client TE45.
[0159] FIGS. 17 through 41 show switch determination tables.
[0160] The tables shown in FIGS. 17 through 41 can be used as those
shown in FIGS. 11 through 15. For example, assume that the client
TE45 of the system 0 detects a fault, and a switch trigger has
occurred when a signal from the work line is input to the client
TE45 of the system 0 by the 4n.times.4n complete group switch 42.
In this case, in FIG. 17, the status is 1, and the detection and
the determination by the monitor are performed by referring to
FIGS. 18, 19, and 20. For example, when the status of the monitor
is indicated by the number 1 as shown in FIG. 18, it is determined
that there is a fault in the transmission line of the system 0 on
the client TE45 side, the 2:1 selector 44 is connected to the
4n.times.4n complete group switch 42 of the system 0, the FERF
monitor (not shown in the attached drawings) of the client TE45 is
switched to the system 1, and the FERF monitor provided in the
client TE analyzes the header of the frame of the SDH, and detects
the FERF. Control is passed to the status 2 shown in FIG. 17. In
the status 2 shown in FIG. 17, the fault determination and the
destination of the control are determined by referring to FIGS. 21,
22, and 23. At this time, if the fault can be removed as a result
of switching the FERF monitor into the system 1, then the fault
determining process is not performed after the transfer of control
to the status 2 shown in FIG. 17, but the communications are
performed through the device of the system 1 of the client
TE45.
[0161] In other cases, a fault is avoided by the method described
above.
[0162] If all transmission lines between two nodes are faulty in a
ring network, a signal flows through a standby line in the opposite
direction. In this case, if the appliances connected to the primary
line and standby line have become faulty, a significant signal is
dropped. The redundancy is designed for an appliance to prevent the
significant signal from being dropped. That is, if there is a
standby appliance, then there is a small probability that both
primary and standby appliances become faulty even if the primary
appliance has become faulty. Therefore, since it is rare that the
standby appliance is faulty when the primary appliance become
faulty, a missing signal is avoided by switching the primary
appliance to the standby appliance, thereby continuously providing
a service.
[0163] To realize the redundancy of an appliance in the above
mentioned case, nodes are configured as shown in FIGS. 42 and 43.
In a (4n+2s).times.(4n+2s) complete group switch where s is 0 or a
positive integer, primary lines and standby line are connected, and
each switch is connected for a number of stages using ports other
than those for ADD/DROP. As a result, k:1 or k:2 protection
(k=n.times.number of complete group switches) can be realized.
[0164] Thus, by connecting a complete group switch for a number of
stages, the number of trunk lines of a ring network can be
increased.
[0165] FIG. 42 shows an embodiment of the configuration of a switch
realizing the redundancy for an appliance.
[0166] In a (4n+2.times.2).times.(4n+2.times.2) complete group
switch for processing n (n=1, 3, 7, 15, . . . ) input/output ports
for use between nodes, and 2n ADD/DROP ports, four inactive
input/output ports are used for connection of each switch. Thus,
the number of (4n+2.times.2).times.(4n+2.times.2) switches can be
increased, that is, extended.
[0167] In addition, two sets of transponders 51-1 through 52-2 for
redundancy of appliances for transmission and reception are
connected to each of the two input/output ports of a switch 50.
Thus, when the redundancy of an appliance is designed
simultaneously for the east side and the west side, a k:1
protection can be realized. When the redundancy is designed for
only one direction, k:2 protection (k=n.times.number of complete
group switches) can be realized. In the configuration for the
redundancy of an appliance as described above, one extension is
designed toward each of the west and east for k:1 protection, or
two extensions are designed toward the west or the east for k:2
protection.
[0168] That is, when a fault occurs on the east side or the west
side, the transponders 51-1 and 51-2 drop a line which cannot
transmit signals, and output them from nodes. That is, if a fault
occurs in an appliance connected to a line connected to a switch
54, for example, when the appliance is on the east side, then the
signal input from the west side to the switch 54 is output from the
port a, and input to a switch 53. This signal is output from the
port b of the switch 53, and input to the switch 50. This signal is
output from the port of the switch 50 is input to the transponder
51-1 or 51-2, and transmitted by bypassing a faulty device.
Similarly, when there arises a fault with an appliance connected to
a line connected to the switch 53, a bypassing signal is output
from the port b, input to the switch 50, output from the port c,
and input to the transponder 51-1 or 51-2. When the redundancy is
designed toward both east and west, one of the transponders 51-1
and 51-2 is assigned to the east, and the other to the west.
[0169] The transponders 52-1 and 52-2 input signals transmitted
along a redundancy line through the transponder 51-1 or 51-2 in
another node to each switch for recovery to the original line. The
signals output from the transponders 52-1 and 52-2 are sequentially
input to the switches 50, 53, and 54, switched and connected when
they are input to appropriate switches, and recover to the original
line. In this example, a switch refers to a complete group switch
as in the above mentioned embodiment.
[0170] Thus, in the k=n.times.(number of switches) lines, one
redundancy path toward each of the east and west, or two redundancy
paths toward the east or the west can be configured.
[0171] FIG. 43 shows another embodiment of the configuration of the
switch realizing the redundancy appliance.
[0172] In a (4n+2.times.4).times.(4n+2.times.4) complete group
switch for processing n (n=2, 6, 14, . . . ) input/output ports
between nodes, and 2n ADD/DROP ports, 8 inactive input/output ports
are used for connection between switches.
[0173] To each of the four input/output ports of a switch 60, two
sets of transponders 63-1 through 64-4 are connected for redundancy
of appliances. Thus, when one redundancy line for an appliance is
applied toward each of the east and the west, k:2 protection is
realized. When redundancy lines for appliances are simultaneously
applied toward one of the east and the west, k:4 protection
(k=n.times.number of complete group switches) is realized.
[0174] In the present embodiment, the number of lines for
transmission of a signal from each of the switches 60 through 62 to
the transponders 63-1 through 63-4 is increased to four from two in
the embodiment shown in FIG. 42. Furthermore, the number of lines
for transmission of a signal from the transponders 64-1 through
64-4 to the switches 60 through 62 is increased to four from two of
the above mentioned embodiment. Thus, k:j (j is a positive integer)
protection can be realized by designing an improved scale of each
complete group switch and configuring the switch containing a
larger number of lines for the redundancy of an appliance. However,
if the value j is too large, a required complete group switch also
become too large. Therefore, in the present embodiment, the k:2
protection toward each of the west and the east, or the k:4
protection toward either west or east is realized.
[0175] In FIG. 42, n is set to 1, 3, 7, 15, . . . , and n is set to
2, 6, 14, . . . in FIG. 43 because the number of input/output ports
is expressed in the power of 2, but it is not limited to this
expression.
[0176] FIG. 44 shows an embodiment of the configuration of the
protection device to which the configuration shown in FIG. 42 is
practically applied.
[0177] FIG. 44 shows an example of configuring an m:1 (m indicates
the number of wavelengths) protection simultaneously toward the
east and the west of two fiber rings using an 8.times.8 complete
group switch (n=1) and two appliance redundancy
transmission/reception transponders 70. In FIG. 44, the
configuration for AD-DROP is omitted.
[0178] A wavelength multiplexed optical signal to be input to a WDM
(wavelength division multiplexer) 71-1 is demultiplexed into each
wavelength by the WDM 71-1, and input to transponders 74-1 through
74-x. The signals of wavelengths output from the transponders 74-1
through 74-x are respectively input to 8.times.8 switches 73-1
through 73-x. When there is a fault on the east side and a signal
having a wavelength which cannot be transmitted, the signal having
the wavelength is transmitted from a corresponding 8.times.8 switch
to a transponder 70-1. Then, it is input to a WDM 71-2,
wavelength-multiplexed with other signals, and returned to the west
side. A similar process is performed if the west side is faulty
when a signal is transmitted from the east side. When a signal
(signal having a wavelength for a redundancy line) is transmitted
from the west side through a redundancy line, it is
wavelength-demultiplexed by the WDM 71-1, and input to a
transponder 70-2. Then, it is returned to the original line by an
appropriate switch in the 8.times.8 switches 73-1 to 73-x, and
transmitted to the east side. A similar process is performed when a
signal is transmitted from the east side through a redundancy
line.
[0179] FIG. 45 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 42 is
practically applied.
[0180] FIG. 45 shows another example of the configuration of the
m:1 (m=number of wavelengths) protection configured simultaneously
on both east and west sides in a 2 fiber ring system using an n=1,
8.times.8 complete group switch, two appliance redundancy
transmission and reception transponder 70, and a 4.times.4 complete
group switch 80.
[0181] With the configuration shown in FIG. 44, a transponder for
each direction is fixedly assigned, but, in this example, each
transponder can be used in any direction using the 4.times.4
complete group switch 80.
[0182] Other units are the same as those shown in FIG. 44, and the
detailed explanation is omitted here.
[0183] FIG. 46 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 42
is practically applied.
[0184] FIG. 46 shows an example of the configuration of the m:2
(m=number of wavelengths) protection configured on one of the east
and west sides in a 2 fiber ring system using an n=1, 8.times.8
complete group switch, two appliance redundancy transmission and
reception transponder 70, and a 6.times.6 complete group switch
81.
[0185] Each transponder can be used in any direction using the
6.times.6 switch. Therefore, according to the embodiment shown in
FIG. 44, one transmission/reception transponder 70 is used on the
west side, and another transmission/reception transponder 70 is
used on the east side. On the other hand, according to the present
embodiment, a signal output from both transponders 70 can be
switched and connected to either west or east side, and a
redundancy signal input from the west or east side can be returned
to the original line.
[0186] Other configurations are the same as the configurations
shown in FIGS. 44 and 45, and the detailed explanation is omitted
here.
[0187] FIG. 47 shows a further embodiment of the configuration of
the protection device to which the configuration shown in FIG. 42
is practically applied.
[0188] FIG. 47 shows an example of the configuration of the m:1
(m=number of wavelengths) protection configured simultaneously on
both sides only for primary lines or on one of the east and west
sides simultaneously for both primary and standby lines in a 4
fiber ring system using an n=3 (only 2 ports are actually used),
8.times.8 complete group switch, two appliance redundancy
transmission and reception transponder 70, and a 6.times.6 complete
group switch 85.
[0189] Using the 6.times.6 switch 85, each transponder can be used
in either directions.
[0190] In FIG. 47, the transmission line comprises a primary system
and a standby system. In this case, since two
transmission/reception transponders 70 are provided for each of the
transmitting and receiving systems, a pair of redundancy
transmission/reception lines can be provided for either directions
from the transmission/reception transponder 70 when both east and
west sides are to be protected. Therefore, only the primary line
can be provided with a redundancy configuration. When only one of
the east and west sides is configured for redundancy, 2 pairs of
redundancy transmission/reception lines can be provided in one
direction with the configuration shown in FIG. 47. Therefore, both
primary and standby systems can be configured for redundancy.
[0191] Since other configurations are basically the same as those
of the embodiments shown in FIGS. 44, 45, and 46, the detailed
explanation is omitted here.
[0192] FIG. 48 shows the embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied.
[0193] FIG. 48 shows an example of the configuration of the m:2
(m=number of wavelengths) protection configured simultaneously on
both east and west sides in a 2 fiber ring system using an n=2
(only 1 port is actually used), 16.times.16 complete group switch,
and four appliance redundancy transmission and reception
transponder 87.
[0194] In FIG. 48, a wavelength-multiplexed signal input from the
west side is demultiplexed into optical signals having respective
wavelengths by a WDM 88, and input to each transponder 89. In
addition, the wavelength for redundancy line is also demultiplexed,
and input to transponders 87-5 and 87-6. Thus, the demultiplexed
signals of the redundancy line are switched and connected, and
output from a WDM 90. In the signals input from a WDM 91, signals
having wavelengths to be switched and connected for protection are
switched and connected in any of the 16.times.16 switches, and
output to transponders 87-1 and 87-2. The optical signals output
from these transponders are wavelength-multiplexed by a WDM 92, and
output. Since the operations are similarly performed in the
opposite direction, the explanation is omitted here.
[0195] Thus, two redundancy lines can be configured on both east
and west sides for the number of wavelengths by configuring the
protection device as shown in FIG. 48 based on the configuration
shown in FIG. 43.
[0196] FIG. 49 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied.
[0197] FIG. 49 shows an example of the configuration of the m:2
(m=number of wavelengths) protection configured simultaneously on
both east and west sides in a 2 fiber ring system using an n=2
(only 1 port is actually used), 16.times.16 complete group switch,
four appliance redundancy transmission and reception transponder,
and an 8.times.8 complete group switch.
[0198] According to the present embodiment, each transponder can be
used on either directions by using an 8.times.8 switch. Therefore,
the present embodiment is the same as the embodiment shown in FIG.
45 except that the present embodiment has four redundancy lines.
Therefore, the detailed explanation is omitted here.
[0199] FIG. 50 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied.
[0200] FIG. 50 shows an example of the configuration of the m:1
(m=number of wavelengths) protection configured simultaneously on
both east and west sides and for both primary and standby systems
in a 4 fiber ring system using an n=2, 16.times.16 complete group
switch, four appliance redundancy transmission and reception
transponder, and an 8.times.8 complete group switch.
[0201] Using an 8.times.8 switch, each transponder can be used in
either directions. That is, each of transponders 95-1 to 95-4 is
assigned to a redundancy line of the primary and standby systems on
the west and east sides using an 8.times.8 switch, and each of
transponders 95-5 to 95-8 is assigned to a redundancy line of the
primary and standby systems on the west and east sides using an
8.times.8 switch. Thus, an m:1 protection can be provided
simultaneously for primary and standby systems on both west and
east directions.
[0202] FIG. 51 shows another embodiment of the configuration of the
protection device to which the configuration shown in FIG. 43 is
practically applied.
[0203] FIG. 51 shows an example of the configuration of the m:2
(m=number of wavelengths) protection configured only for a primary
system, on both east and west sides, or for both primary and
standby systems in a 4 fiber ring system using an n=2, 16.times.16
complete group switch, four appliance redundancy transmission and
reception transponder, and a 12.times.12 complete group switch.
[0204] Using a 13.times.12 switch, each transponder can be used in
either directions.
[0205] In FIG. 51, bold lines indicate that a two-wavelength
optical signal is input to the 12.times.12 switch, but actually
indicate two 1-wavelength lines.
[0206] In FIG. 51, using a 12.times.12 switch, an m:2 protection
can be configured by allotting transponders 100-1 to 100-4 only for
the primary system on both west and east sides, and by using
transponders 100-5 to 100-8 for input of a signal from both west
and east sides. In addition, when a protection device is configured
simultaneously for both primary and standby systems on either east
or west direction, an m:2 protection device can be configured by
connecting the transponders 100-1 to 100-8 to either west or east
side.
[0207] The above mentioned configurations are not limited to a 2 or
4 fiber rings, but any number of multifiber ring appliance
redundancy can be realized.
[0208] In addition, when an unused port of a (4n+2s).times.(4n+2s)
switch (s=0 or a positive integer) is not only used for the
redundancy of an appliance, but also used as an ADD or DROP port,
for example, a signal from another ring network can be accommodated
in any ring of a multifiber ring.
[0209] In addition, when an unused port of a (4n+2s).times.(4n+2s)
switch (s=0 or a positive integer) is not only used for the
redundancy of an appliance, but also used as a test signal
transmission/reception port, it can be used for a circuit test of
any fiber ring.
[0210] FIG. 52 shows the entire network including the embodiments
shown in FIGS. 42 through 51.
[0211] As shown in FIG. 52, a network has the configuration in
which nodes A through E are connected as a ring through a
transmission line. The configuration of each node is indicated by
the node A.
[0212] For example, each node wavelength-demultiplexes using the
WDM 1 a wavelength multiplexed signal received from the west side
into signals of respective wavelengths. An optical signal of each
wavelength is input to the transponder 1, and a signal is
reproduced. Then, it is input to an m:1 (or m:2, m:4) protection
switch 1 shown in FIGS. 42 through 51. In the protection switch 1,
as described above, the m:1, m:2, or m:4 redundancy appliance is
designed as described above. An optical signal output from the
protection switch 1 is then input to the optical NPE for redundancy
of a line. A signal to be dropped is transmitted to an ADM or a
router. A signal to be added is input from an ADM or a router to an
optical NPE. The optical signal output from the optical NPE is
furthermore, input to an m:1, m:2, or m:4 protection switch 2. The
configurations shown in FIGS. 42 through 51 can be applied to this
protection switch 2. The signal output from the protection switch 2
is input to the transponder 2, a signal is reproduced, and it is
wavelength-multiplexed by the WDM 2 and output.
[0213] A flow of a signal from the east side to the west side is
realized in the same method as the above mentioned process, and the
detailed explanation is omitted here.
[0214] The description of the embodiments according to the present
invention is based on the complete group switch, but these optical
switches can be replaced with electric switches.
[0215] According to the present invention, a protection function is
not incorporated into an ADM device, but a single complete group
switch is used. Therefore, a simple and less expensive
configuration can be provided for realizing and adding an
extensible protection switch.
* * * * *