U.S. patent application number 10/089112 was filed with the patent office on 2006-01-26 for connection of an add/drop node.
Invention is credited to Dag Bonnedal, Lars Egnell, Ola Hulten, Bengt Johansson, Frederik Liden, Fredrik Lindgren.
Application Number | 20060018593 10/089112 |
Document ID | / |
Family ID | 20417197 |
Filed Date | 2006-01-26 |
United States Patent
Application |
20060018593 |
Kind Code |
A1 |
Egnell; Lars ; et
al. |
January 26, 2006 |
CONNECTION OF AN ADD/DROP NODE
Abstract
An add/drop node of an optical WDN-network which has two fiber
paths for light of a plurality of channels propagating in opposite
directions comprises two add/drop modules (231, 23r) for each of
the channels. All the modules are identically constructed. Each
module comprises an add device (251, 25r) for adding light to one
of the paths and a drop device (27r, 271) for deflecting a portion
of light from a second one of the paths. A module comprises a house
(41) enclosing the add device and the drop device. A first fixed
connector (53, 73) is attached to the house for connection in the
first path and to a an optical fiber (45, 65) which extends freely
from the house and has a first free connector (43, 63) at its free
end to be attached to the fixed connector of a neighbouring
add/drop module for continuing the first path through the
considered add/drop module to the neighbouring module. In the same
way a second fixed connector is attached to the house for
connection in the second path and to a second optical fiber which
extends freely from the house and has a second free connector at
its free end to be attached to the fixed second connector of a
neighbouring add/drop module for continuing the second path through
the considered add/drop module to the neighbouring module.
Inventors: |
Egnell; Lars; (Stockholm,
SE) ; Johansson; Bengt; (Stockholm, SE) ;
Liden; Frederik; (Stockholm, SE) ; Lindgren;
Fredrik; (Stockholm, SE) ; Bonnedal; Dag;
(Stockholm, SE) ; Hulten; Ola; (Stockholm,
SE) |
Correspondence
Address: |
AKA CHAN LLP / CISCO
900 LAFAYETTE STREET
SUITE 710
SANTA CLARA
CA
95050
US
|
Family ID: |
20417197 |
Appl. No.: |
10/089112 |
Filed: |
September 27, 2000 |
PCT Filed: |
September 27, 2000 |
PCT NO: |
PCT/SE00/01877 |
371 Date: |
June 26, 2002 |
Current U.S.
Class: |
385/24 |
Current CPC
Class: |
H04J 14/0201 20130101;
G02B 6/4454 20130101; H04J 14/0219 20130101 |
Class at
Publication: |
385/024 |
International
Class: |
G02B 6/28 20060101
G02B006/28 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 1999 |
SE |
9903521-4 |
Claims
1. (canceled)
2. An add/drop node to be connected in an optical WDM-network, the
network including two optical fiber paths for letting light of a
plurality of channels propagate in opposite directions in the
network, characterized by two add/drop modules for each of the
channels, each add/drop module comprising an add device for adding
light to a first one of the two optical fiber paths and a drop
device for deflecting a portion of light from a second one of the
two optical fiber paths different from the first one and all
add/drop modules having the same construction, and in that the
add/drop modules are arranged in two sets, the add/drop modules of
a first one of the two sets having their add devices connected in
the first one of the two optical fiber paths and their drop devices
connected in the second one of the two optical fiber paths and the
add/drop modules of a second one of the two sets different from the
first one having their add devices connected in the second one of
the two optical fiber paths and their drop devices connected in the
first one of the two optical fiber paths.
3. An add/drop node according to claim 2, characterized in that in
each of the two sets the add/drop modules are placed at the sides
of each other, and that for two adjacent add/drop modules an output
of the add device in a first one of the two adjacent add/drop
modules is connected to an input of the add device in a second one
of the two adjacent add/drop modules.
4. An add/drop node according to claim 2, characterized in that in
each of the two sets the add/drop modules are placed at the sides
of each other, and that for two adjacent add/drop modules an output
of the drop device in a first one of the two adjacent add/drop
modules is connected to an input of the drop device in a second one
of the two adjacent add/drop modules.
5. An add/drop node according to claim 2, characterized in that in
each of the two sets the add/drop modules are placed at the sides
of each other to form inner add/drop modules and two end add/drop
modules in each set, the end add/drop modules having an add/drop
module of the set on only one side, and that for one of the two end
add/drop modules of a first one of the two sets its drop device has
an output connected to an input of the add device of one of the two
end add/drop modules in a second one of the two sets and that for
said one of the two end add/drop modules of the second one of the
two sets its drop device has an output connected to an input of the
add device of said one of the two end add/drop modules in the first
one of the two sets.
6. An add/drop node according to claim 2, characterized in that
each add/drop module comprises a housing enclosing the add device
and the drop device of the add/drop module, a first fixed connector
attached to the housing for connection in the first one of the two
optical fiber paths and a first optical fiber extending freely from
the housing and having a first free connector at its free end to be
attached to the fixed connector of a neighboring add/drop module
for continuing the first path through the considered add/drop
module to the neighboring module, and a second fixed connector
attached to the housing for connection in the second one of the two
optical fiber paths and a second optical fiber extending freely
from the housing and having a second free connector at its free end
to be attached to the fixed second connector of a neighboring
add/drop module for continuing the second path through the
considered add/drop module to the neighboring module.
7. An add/drop node according to claim 6, characterized in that the
house includes two winding cores around which excessive fiber
lengths connecting devices and connectors of the add/drop module
can be wound.
8. (canceled)
9. An add/drop node according to claim 3, characterized in that in
each of the two sets the add/drop modules are placed at the sides
of each other to form inner add/drop modules and two end add/drop
modules in each set, the end add/drop modules having an add/drop
module of the set on only one side, and that for one of the two end
add/drop modules of a first one of the two sets its drop device has
an output connected to an input of the add device of one of the two
end add/drop modules in a second one of the two sets and that for
said one of the two end add/drop modules of the second one of the
two sets its drop device has an output connected to an input of the
add device of said one of the two end add/drop modules in the first
one of the two sets.
10. An add/drop node according to claim 4, characterized in that in
each of the two sets the add/drop modules are placed at the sides
of each other to form inner add/drop modules and two end add/drop
modules in each set, the end add/drop modules having an add/drop
module of the set on only one side, and that for one of the two end
add/drop modules of a first one of the two sets its drop device has
an output connected to an input of the add device of one of the two
end add/drop modules in a second one of the two sets and that for
said one of the two end add/drop modules of the second one of the
two sets its drop device has an output connected to an input of the
add device of said one of the two end add/drop modules in the first
one of the two sets.
11. (canceled)
12. An add/drop node according to claim 3, characterized in that
each add/drop module comprises a housing enclosing the add device
and the drop device of the add/drop module, a first fixed connector
attached to the housing for connection in the first one of the two
optical fiber paths and a first optical fiber extending freely from
the housing and having a first free connector at its free end to be
attached to the fixed connector of a neighboring add/drop module
for continuing the first path through the considered add/drop
module to the neighboring module, and a second fixed connector
attached to the housing for connection in the second one of the two
optical fiber paths and a second optical fiber extending freely
from the housing and having a second free connector at its free end
to be attached to the fixed second connector of a neighboring
add/drop module for continuing the second path through the
considered add/drop module to the neighboring module.
13. An add/drop node according to claim 4, characterized in that
each add/drop module comprises a housing enclosing the add device
and the drop device of the add/drop module, a first fixed connector
attached to the housing for connection in the first one of the two
optical fiber paths and a first optical fiber extending freely from
the housing and having a first free connector at its free end to be
attached to the fixed connector of a neighboring add/drop module
for containing the first path through the considered add/drop
module to the neighboring module, and a second fixed connector
attached to the housing for connection in the second one of the two
optical fiber paths and a second optical fiber extending freely
from the housing and having a second free connector at its free end
to be attached to the fixed second connector of a neighboring
add/drop module for continuing the second path through the
considered add/drop module to the neighboring module.
14. An add/drop node according to claim 5, characterized in that
each add/drop module comprises a housing enclosing the add device
and the drop device of the add/drop module, a first fixed connector
attached to the housing for connection in the first one of the two
optical fiber paths and a first optical fiber extending freely from
the housing and having a first free connector at its free end to be
attached to the fixed connector of a neighboring add/drop module
for continuing the first path through the considered add/drop
module to the neighboring module, and a second fixed connector
attached to the housing for connection in the second one of the two
optical fiber paths and a second optical fiber extending freely
from the housing and having a second free connector at its free end
to be attached to the fixed second connector of a neighboring
add/drop module for continuing the second path through the
considered add/drop module to the neighboring module.
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
23. (canceled)
24. (canceled)
25. (canceled)
26. (canceled)
27. (canceled)
28. (canceled)
29. (canceled)
30. (canceled)
31. (canceled)
32. (canceled)
33. (canceled)
34. (canceled)
35. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to an add/drop node of an
optical WDM-network, in particular to the connection of an add/drop
node to two paths of the network carrying light in opposite
directions, and to a network including such an add/drop node.
BACKGROUND
[0002] Optical networks using WDM (Wavelength Division
Multiplexing) are now proposed to be built more and more. In such
networks a plurality of add/drop nodes are connected and simple
devices should be provided for connecting the nodes to the network.
For example, when an existing node is expanded to be capable of
receiving and transmitting in another wavelength band the manual
work required therefor should be minimized. An optical network
having add/drop nodes is for example disclosed in U.S. Pat. No.
5,754,545.
SUMMARY OF THE INVENTION
[0003] It is an object of the invention to provide an add/drop node
for an optical WDM-network having a simple way of connecting the
node to circulating fiber paths of the network.
[0004] It is another object of the invention to provide an optical
WDM-network having an add/drop node built to allow a simple way of
connecting the node to parallel fiber paths of the network.
[0005] Thus generally, an add/drop node is intended to be connected
in an optical WDM-network. The network has two parallel fiber paths
allowing light of a plurality of wavelength channels to propagate
in opposite directions. The add/drop node comprises two add/drop
modules for each of the channels. All the modules are identically
constructed and most of their connections are very similar to each
other allowing a simple mounting and connection of the components
of the node and also a simple rearrangement for changing wavelength
channels and for adding/deleting wavelength channels used in the
network. Each module comprises an add device for adding light to a
first one of the paths and a drop device for deflecting a portion
of light from a second one of the paths. The add device and the
drop device of a module are enclosed by comprises a house, the
houses of the modules being placed in a single row, at the sides of
each other and for instance mounted in a rack. A first fixed
connector is attached to the house of a module for connection in
the first path and to a an optical fiber which extends freely from
the house and has a first free connector at its free end to be
attached to the fixed connector of a neighbouring add/drop module
for continuing the first path through the considered add/drop
module to the neighbouring module. In the same way a second fixed
connector is attached to the house for connection in the second
path and to a second optical fiber which extends freely from the
house and has a second free connector at its free end to be
attached to the fixed second connector of a neighbouring add/drop
module for continuing the second path through the considered
add/drop module to the neighbouring module,
[0006] More particularly, in the add/drop node two add/drop modules
are provided for each of the channels of light propagating in the
network. Each add/drop module has an add device or light combiner
for adding light to one of the two optical fiber paths and it has
also a drop device for deflecting a portion of light from the other
optical fiber path. Furthermore, all the add/drop modules have the
same construction. The add/drop modules can then be arranged in two
sets, so that the add/drop modules of a first set have their add
devices connected in one fiber path and their drop devices
connected in the other fiber path. Also, the add/drop modules of
the second set then have their add devices connected in the other
fiber path and their drop devices connected in said one fiber
path.
[0007] In at least each of the two sets the add/drop modules are
placed at the sides of each other and then inner modules and two
end modules are obtained in each set. For two adjacent or
neighbouring add/drop modules of a set an output of the add device
in a first one of the two adjacent add/drop modules can be
connected to an input of the add device in a second one of the two
adjacent add/drop modules. In the same way, for two adjacent
add/drop modules an output of the drop device in a first one of the
two adjacent add/drop modules can be connected to an input of the
drop device in a second one of the two adjacent add/drop modules.
For one of the end add/drop modules comprised in a first set its
drop device can have an output connected to an input of the add
device of one of the two end add/drop modules in the other, second
set. Similarly, for said one end add/drop module of the second set
its drop device can have an output connected to an input of the add
device of said one end add/drop module in the first set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention will now be described by way of a non-limiting
embodiment with reference to the accompanying drawings, in
which
[0009] FIG. 1 is a block diagram of an optical network having a
ring architecture and a hub node and four client nodes,
[0010] FIG. 2 is a schematic picture of the connection lines of an
add/drop module used in the nodes of the network,
[0011] FIG. 3 is a view from the side of the inside of a house of
an add/drop module,
[0012] FIG. 4 is a front view of a plurality of add/drop modules
mounted in a rack,
[0013] FIG. 5 is a block diagram schematically showing the
connections of add/drop modules of the nodes,
[0014] FIG. 6 is a block diagram showing in a somewhat more
realistic way the connections of add/drop modules of the nodes,
and
[0015] FIG. 7 is a perspective view showing the inside of a house
of an add/drop module.
DETAILED DESCRIPTION
[0016] In FIG. 1 a block diagram of an optical fiber WDM-network
having a ring configuration is shown. Thus two optical fiber paths
1e, 1w pass in a basically uninterrupted way all around the
network, one fiber path 1e carrying light propagating in the east
direction and the other fiber path 1w carrying light propagating in
the west direction.
[0017] The network includes a hub node 2 and in the embodiment
shown four client nodes 3, called Client 1, 2, 3 and 4, the nodes
being connected to the two basic fiber paths 1e, 1w for adding and
dropping light from the fibers. A client node n receives and
transmits information in a narrow wavelength band, also called
channel, around a single wavelength .lamda..sub.n, n=1, 2, . . .
The hub node 2 can receive and transmit information in all
channels, i.e. on all wavelengths .lamda..sub.n, n=1, 2, . . . For
each client node 3, the hub node 2 is connected to an electrical
client portion 5. Such an electrical client portion 5 comprises an
electrooptic converter or optical transmitter 7 converting
electrical signals to optical signals and an optoelectric converter
or optical receiver 9 for receiving optical signals converting the
received signals to electrical signals. The electrical client
portion 5 is through optical fibers connected to an optical client
portion 11 in the hub node 2. The optical client portion 11 has
optical connectors for receiving the optical fibers extending from
the respective electrical client portion.
[0018] The optical client portion 11 comprises an optical
receiver-transmitter combination 13, 15 for transmission, the
receiver 13 of the combination receiving the light signal from the
transmitter 7 of the electrical client portion 5 providing its
output signal to the transmitter 15 of the pair, which provides a
well-defined light signal in the narrow wavelength band used for
the respective client. The optical transmitter 15 is coupled to an
optical connector for providing its output signal on an optical
fiber to add/drop modules as will be described hereinafter.
[0019] The optical client portion 11 also comprises an optical
receiver-transmitter combination for receiving, the combination
comprising two optical receivers 17e, 17w connected to receive
light from the add/drop modules through optical fibers and optical
connectors, one receiver 17e being used for receiving light
propagating in the network, in the appropriate fiber, in an east
direction and another receiver 17w being used for receiving light
propagating in the west direction in the ring network. The outputs
of the two optical receivers 17e, 17w are connected to inputs of a
combining element or optical multiplexer 19 which combines the
received signals to provide them to a transmitter 21, the output
terminal of which is through the respective connector and a fiber
length connected to the receiver 9 in the electrical client portion
5.
[0020] Furthermore, the hub node 2 includes a plurality of add/drop
modules 231, 23r, one pair of such add/drop modules being provided
for each client node 3 in the network. In such a pair one module
231 is adapted to transmit in a left direction from the hub node
and to receive from the same left direction. The other module 23r
of a pair is adapted to transmit in and to receive from the right
direction from the hub node. Each add/drop module is connected in
the two ring-shaped fiber paths 1e, 1w of the network. A left
add/drop module 231 comprises one add device 251 connected in the
fiber ring path 1w and one drop device 271 connected in the other
fiber ring path 1e. The add device 251 is through fiber pieces, a
50/50 splitting coupler 29 (only one is shown in the drawing) and
the respective connector connected to the transmitter 15 in the
optical client portion 11 for the appropriate client node. The drop
device 271 is through a fiber and the respective connector
connected to the receiver 17e in the optical client portion 11 for
the same client node.
[0021] In the same way, the right add/drop module 23r in the pair
comprises one add device 25r connected in the fiber ring path 1e
and one drop device 27r connected in the other fiber ring path 1w.
The add device 25r is through fiber pieces, the respective
splitting coupler 29 and the respective connector connected to the
transmitter 15 in the optical client portion 11 for the client
node. The drop device 27r is through a fiber and the respective
connector connected to the receiver 17w in the optical client
portion 11 for the client node.
[0022] The add devices 251, 25r contain some coupling or combining
element and if required a notch filter blocking light of the
wavelength band or channel for which the add/drop module is
designed. The optional filter will then stop only light of said
wavelength band propagating in the respective fiber ring path 1w,
1e before light of the same wavelength band is added in the
combining element. The drop devices 271, 27r contain in the same
way some splitting and filtering element for tapping off only light
of the wavelength band or channel for which the add/drop module is
designed.
[0023] It appears that all add/drop nodes 231, 23r have the same
basic design and functions and can thus all be given the same
physical shape as will be discussed hereinafter.
[0024] The two fiber ring paths 1e, 1w are connected to the hub
node 2 on a left side of the hub node and on a right side of the
node. At each such side a monitor module 311, 31r can be arranged
which is thus connected in the two ring paths. A monitor module
311, 31r comprises an add coupler 331, 33r for adding e.g. some
control signal and a tap 351, 35r for tapping off some small
portion of the incoming light power, e.g. 1%.
[0025] The schematic diagram of FIG. 2 illustrates the functions of
an add/drop module 231, 23r. The module comprises a house indicated
at 41. Light from one 1e of two ring paths of the network enters
the module at a connector 43 attached to a fiber piece 45 extending
loosely outside the house 41. The fiber piece 45 has a thick
protective sleeve and is inside the house at 47 welded to an end of
an optical fiber 49 having a standard thin protective sleeve. The
optical fiber piece 49 is at its opposite end connected to one of
the two inputs of the add device 251, 25r. The output of the add
device is connected to a fiber piece 51, which in turn is connected
to a connector 53 attached to the house 41. The connector 53 should
be connected in the same ring path 1e as the input connector 43.
The other input of the add device is through a fiber piece 55
connected a connector 57 attached to the house 41. The connector 43
thus receives light from the ring path 1e to make it continue to
the fiber 45, through the weld 47, the fiber piece 49, the add
device 251, 25r, the fiber piece 51 to the connector 53. The output
connector 53 lets the light continue along the ring path 1e. Light
from an optical client portion 11 enters the module at the
connector 57, continues through the fiber 55 to the add device 251,
25r, in which the light is added to that propagating along the ring
path 1e.
[0026] Furthermore, in the module 231, 23r there is a set of
connected fiber pieces, which is parallel to that described and is
connected in the other ring path 1w of the network but in which
instead of the add device 25r, 251 the drop device 271, 27r is
connected. Thus a connector 63 is to be connected to the other ring
path and is attached to an end of a well protected fiber piece 65
extending partly outside the house 41, the other end being
connected through a weld 67 to a standard fiber piece 69. This
fiber piece is in turn connected to one of the two outputs of the
drop device 271, 27r. The input of the drop device is connected to
fiber piece 71 which receives light from a connector 73 attached to
the house 41. The connector 73 should be connected in the
respective ring path 1w. The other output of the drop device 271,
27r is connected to an end of a fiber piece 75 which has its other
end connected to a connector 77 attached to the house 41. This
connector is through a fiber attached to a respective receiver 17w
(17e) in the optical client portion 11. Light from the ring path 1w
enters the module at the connector 73, continues through the fiber
71, the drop device 271, 27r, the fiber 69, the weld 67, the thick
fiber 65 to the loose connector 63, which in turn is connected in
the respective ring path 1w of the network. Some light of a
specific wavelength band is tapped off in the drop device 271, 27r
and continues through the fiber 75 to the connector 77 and
therefrom to the respective optical client portion 11.
[0027] The physical layout of the interior of an add/drop module
house 41 is shown in FIG. 3. The module house 41 comprises a
substantially flat portion from which various walls stand out. The
walls all have the same height and connect to a basically flat lid,
not shown, which is mounted over the house 41. The walls form two
circular winding cores 81 having a sufficiently large diameter,
e.g. about 50 mm, allowing that fibers can be wound around them and
not being subjected to too small bending radii (too large
curvatures). The two winding cores 81 are placed at some distance
of each other allowing that fibers can pass therebetween. By
arranging two such cores the fiber pieces used can be allowed to
have some extra length allowing them to be comfortably handled and
to again be spliced to the devices in the case of fiber breaks or
bad splices and also, the direction of the fiber pieces at the
places where they are connected to the devices can be selected to
be the proper one not using too small bends, by placing the fibers
for instance in a configuration similar to the figure eight around
the two cores 81. Inside the walls forming the winding cores
through-holes 83 may be arranged for an easy handling of the module
house. The add devices 251, 25r and the drop devices 271, 27r can
be attached between outstanding walls 85 at the top of the
house.
[0028] At the lower edge of the house 41 devices are provided for
attaching the house to a rack, the attaching devices comprising a
notch 87 at the rear side and a snap device 89 at the front side. A
channel 91 is formed at the front top side of the house 41 to allow
fibers connecting the module to the associated optical client
portion to be held therein.
[0029] FIG. 4 is a front view of the add/drop modules 231, 23r and
the monitor modules 311, 31r mounted in a rack, the loosely
extending fiber pieces 45, 65 not being visible in this figure. By
comparing FIG. 4 to FIG. 1 it is seen that the connection of all
left add/drop modules 231 is as indicated in FIG. 3, the extending
fiber pieces 45 being inserted in the mating connectors 53, 73 in
the adjacent module at the left side of the respective module. This
connection is illustrated in the schematic view of FIG. 6, see also
FIG. 5. Thus, in FIG. 5 the same basic connection as in FIG. 1 is
illustrated, where, in the right modules 23r the add devices and
the drop devices have changed places with each other. Then a cross
coupling must be made between the group of left modules 231 and the
group of right modules 23r and between the right group and the
right monitor module 31r as compared to the straight schematic
connection of modules shown in FIG. 1. The same connection of the
modules is illustrated in FIG. 6 in which the connections between
the add/drop modules using loosely extending fiber pieces is shown.
From this figure it appears clearly that all add/drop modules 231,
23r can have an identical construction, only the tapping-off
devices and filters being special to the channel for which the
respective module is designed. The cross coupling is made in the
middle of the assembly of add/drop modules, between the left and
right modules. Such a cross connection can be made by connecting
the loose fiber pieces 101 having optical connectors at each end in
a cross configuration or a particular cross connecting module can
be used. Such a module has the same exterior design as the other
modules but has inside just the optical fibers connected
cross-wise. In FIG. 4 a multitude of add/drop modules 231, 23r are
illustrated. However, only a portion of the add/drop modules may be
active ones, constructed as described above. At the side of the
active modules dummy modules are inserted having the same exterior
layout but without the connectors and the loosely extending fibers.
The dummy modules are used for just filling up the space between
the active modules and the monitor modules.
[0030] The two monitor modules 311, 31r both have the same exterior
connectors and interior devices as each other but have not the same
interior connection lines. The necessary connections appear clearly
from FIG. 1.
[0031] The client nodes 3 in the network have the same basic design
as the hub node 2 but are designed to receive and transmit in only
one wavelength band. The same kind of add/drop modules as described
above can for example be used.
[0032] In other network ring architectures the client nodes can
receive and transmit in more than one wavelength band. Then the
client nodes can have the same structure as the hub node 2.
* * * * *