Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SYSTElvl A,ND..METROD FORIM:USINGWAILLENCir-lS IN AN
FTYCAII.M.3VORK
BACKGROUND OF 'THE INVENTIM4
Wavelength Division Multiplexing (WDM) is a method by which single-
mode optical fibers are nsed to carry multiple light waves of clifferent
frequencies.
ta In a WDM network many Wavelengths are combined in a single fiber, thus
increasing the carrying Capacity of the fiber. Signals are assigned to
specific
frequencies of light (wavelengths) within a frequency band, This multiplexing
of
optical wavelengths is analogous to the way radio stations broadcast on
different
wavelengths as to not interfere with each other. Because each channel is
transtained
;s on a different wavelength, a desired channel may be selected using a
tuner. WDM
channels (wavelengths) are selected in a similar manner. in a WDM network, all
wavelengths are transmitted through a fiber, and decaultiplexed at a receiving
end.
The fiber's capacity is an agercgate of the transmitted wavelengths, each
wavelength
having its own dedicated bandwidth.
20 Dense Wavelength Division Multiplexing (DVVDM) is a Arom network in
which wavelengths are spaced more closely than in a coarse WDM network. This
provides for a greater overall capacity of the fiber.
WPM may be used with dedicated protection techniques such as a
Unidirectional Path Switched Ring (UPSR) in a Synchronous Optical Network
25 (SONET). Such u dedicated protection technicitte Uses dual counter-
rotating rings
that fonti hi-directional connections between the nodes of the network. A
fully
protected bi-directional connection between any two nodes may be established
and
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dedicated to a particular wiwelcngth. A working wavelength travels in one
direction, and a protection wavelength travels in the Opposite direction. The
working wavelength typically takes a shorter path between the two nodes while
the
protection 'wavelength takes a longer path. The frequent:), ofthe working and
protection WIIvniCrigth$ may be identical, as they travel in opposite
directions. Every
section of the duel counter-rotating rings ate oceupied by either the working
wavelength or the protection wavelength (a section may be defined as the
fibers
directly connecting two nodes within a ring). Therefore, the working
wavelength
and the protection wavelength cannot be used to establish any additional
connections
le between any other two nodes. Additional connections require the use of
additional
wavelengths.
It should be noted that WDM equipment within a given WDM node can only
support a finite number of wavelengths; therefore, there is often an economic
benefit
associated with limiting the nuttaVr of wavelengths used when designing a WIWI
is network_
SUMMARY OF THE IN VENTION
An embodiment of the present invention includes a network, or
corresponding method, with at least four network nodes that are each coupled
to at
2a least three network paths. At least two of the at least three network
paths couple the
network nodes. The network also includes at least two siab-nerworks that each
include at least two of the network nodes and use at least one wavelength in
common with the other sub-network.
Another embodiment of the present invention includes a network, or
2s corresponding method, with (i) at least one network node coupled to at
least four
network paths and (ii) at least two sub-networks each including the at least
one
network node and using al le= one wavelength in common.
BRIEF DESCRIPTION OF TUE DRAWINGS
The foregoing and other objects, features and advantages of the invention
win be apparent from the following more particular description of preferred
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embodiments of the invention, as illustrated in the accompanying drawings in
which
like reference diameters refer to the Same parts throughout the different
views. The
diawing s are not necessarily to scale, emphasis instead being placed upon
ilinsnating the principles of the invention.
FIG. 1 is a logical view of a reconfigurable. 2-degree1 optical. add/drop node
according to an embodiment of the present invention;
FIG_ 2 is a logical view of a ieconfigurable. 3-degree, optical, add/drop node
according to an embodiment of the present invention;
FIG. 3 is a physical perspective of a reconfigurable, 2-degree. optical,
ip
add/drop node;
F10. 4 is a physical perspective of a reconfigurable, 3-degree. optical.
add/drop node;
FIG. 5 is a network diagram of a multi-ring design using 2-ciegree nodes and
3-dcgree nodes;
FIG. 6 is a block diagram of a drop unit according to an embodiment of the
present invention;
FIG. 7 is a block diagram of an add unit =cording to an embodiment of the
present invention;
FIG. 8 is a block diagram of a 2-degree node with two, reconfigurable,
optical interfaces.
FIG. 9 is a block diagram of a 3-degree node with three, reconfigurable,
optical interfaces;
FIG, 10 is a block diagram of a 4-degree node with four, reeonfigurable,
optical interfaces,
21 FIG. 11 is a network diagram of a single ring network design
utilizing 2-
degree nodes;
FIG. 12 is a network diagram of a single ring network design inilizing 2-
degree nodes where a fully protected hi-directional connection is established
between nodes C and F;
PIG. 13 is a network diagram of a network where nodes B, C. 13, and F (torn
FIG. 12 are replaced with 3-degree nodes;
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FIG. 14 is a network diagram of a network where nodes 13. C, 0, and F from
FIG. 12 are replaced with 4-degree nodes;
FIGS. 15-18 are network diagrams illustrating how mu degree nodes may
be added to an existing, single ring, Dwr)m network to mare additional sub-
3 network rings that reduce the munher of wavelengths used for
communications in
The network.
DETAILED DESCRIPTION OF TI-LE INVENTION
A description of preferred embodiments of the invention follows.
30 ACCOrdin8 to some embodiments of the present invention, a total number
at
wavelengths used in a wpm network may be reduced by designing a network using
multi-degree noricts that form multiple stib-networks. Isolated sub-networks
that do
not share common network paths may reuse the mune wavelengths used for
communications within the other sub-networks.
15 An embodiment of the present invention includes a network, or
corresponding method. with at least four network nodes that are each coupled
to at
least three network paths. Al least two of the at least three network paths
couple the
network nodes. The network also includes at least two sub-network that each
include at least two of the network nodes and use at least one wavelength in
ar common with the other sub-network.
The sub-networks may use at least one wavelength, in ;addition to the at least
one wavelength in common. that supports conmannications between the nodes of
different sub-networks. The sub-networks may be ring networks, mesh networks,
or
a combination thereof
as The network may include at least four network paths that couple the
network
nodes and define a third sub-network, Additional sub-networks may be defined
with
an addition of an even nomber of network paths. The network paths may
themselves
include multiple network nodes or sub-networks.
The network nodes may be reconfigurable; that is, they may be used tin,
so selectively reconfigure the optical interconnections associated with the
network
paths_ 'This reconfiguration may be in the optical domain and may be achieved
through the use a RccoiZgurable Optical Add/Drop Multiplexers (ROADMs).
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Additiowilly, the nodes of the network may include add/drop ports alai are
used for
adding or dropping wavelengths to and from the network.
A network path carries a data stream between network nodes and may be a
single fiber for ti-directional traffic or multiple fibers for hi-directional
S communications.
Details of the network embodiments described above are presented below in
reference To FIGS. $ and 13-18. FIGS. 1-4 and 6-12 illustrate embodiments of
nodes, add/drop multiplexeis, and network protection techniques (e_g.,
lJnictircetional Path Switched Ring (1../PSR)) useful for understanding
aspects of the
)3 present invention.
F La. 1 illustrates a logical view of a reconfigurable, 2,-degree, optical,
add/drop node 100 according to an embodiment of the present invention. The
node
100 includes two reeonfigurable optical interfaces (ROW- The ROls are labeled
Eltst 110 and West 120 in FIG. 1. F.ach ROI. includes a =hi-wavelength input
port
)5 130a. 130b and a multi-wavelength output port 1404, 140b. According to
one
embodixttent, the multi-wavelength parts nansport multiple wavelengths over
single
fibers I50a, 1501} and 160; 160b by using wavelength division multiplexing
(WDM) techniques.
According to an embodiment of the present invention, add and drop ports
io (not shown) are associated with each ROI. Multiple wavelengths may be
dropped
at a given ROI. When wavelengths are dropped, each dropped wavelength is
placed
on an. individual fiber 170; 170b. It should be appreciated that the single
line 170a,
170b in FIG, 1 used to show drops may represent multiple individual fibers.
When
wavelengths are added, each added 'wavelength is received on an individual
fiber
Ig0a, 180h_ It should be appreciated that the single line 180a, 1110b in FIG.
1 used
to show adds may represent multiple individual fibers.
A wavelength (%) arriving On the multi-wavelength input port 130a. 130b of
a given ROI 110,120 may be directed to either the associated drop poll 170;
170b
or may be passed-through TO the multi-wavelength output port 140b, 140a of the
ao other ROI 120,110, Pass-through channels / 904,19013 are illustrated in
FIG. 1 by
the dashed lines. Because the node in FIG. 1 has two ROls, it may be referred
to as
a 2-degree node (i.e.,
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FIG. 2 illustrates a logical view of a 3-degree node (i.e.. K=3) 200. ROIs
210, 220, and 230 arc labeled East, West. and North, respectively. For this
node
200, a wavelength (A) artivin8 on she multi-wavelength input port of a µ'ivcn
ROI
may be directed to either the associated drop port or may be passed-through to
the
S mu-wavelength output ports of either of she two other ROIs, as indicated
in FIG.
2.
FIG. 3 illustrates a physical perspective of a node 300. The node 300
includes two ROls 310, 320. The node 300 may be impletnensed as the node 100
shown in FIG. 1. As shown, add units 311 and 321 may he used to add
wavelengths
to multi-wavacrtgth output ports. At a given ROT 310, these Wavelengths can
come
from either the add ports or front the drop unit 522 of she other ROI 320, as
indicated. Drop units 312 and 322 may be used TO drop wavelengths to
individual
fibers of an associated drop port. A-1a given 13.01 310, these wavelengths may
come
from the multi-wavelength input port associated with The given ROI 310.
13 FIG. 4 illustrates a physical perspective of a node 400. The node 400
includes three ROIs 410, 420, and 430. The node 400 may he implemented as she
node 200 shown in FIG. 2 and operate in a similar manner as the 2-degree node
300
described in reference to FIG. i
FIG. 5 illustrates a multi-ring design 500 using 2-degree nodes and 3-degree
nodes, Nodes A 510 and C 510 sire 2-degree nodes. Nodes B $20 and D 540 arc 3-
degree nodes. As shown, there are three distinct rings, referred to as Ring 1
550,
Ring 2 560, and Ring 3 570, Ring 1 includes nodes A, 13. C. and D. Ring 2
includes
nodes A, B. and D. Ring 3 includes nodes B, C and D. The rings 550, 560, 570
share some common paths (or ring sections). For instance, Ring 2 and Ring 3
share
a path between nodes 13 and D. According so one embodiment, this implies that
the
wavelengths used within Ring 2 must be different from she wavelengths used
within
Ring 3. since all the wavelengths of both of these rings are placed on she
same path
580 (i.e.. fiber that runs between nodes B and r)). According to one aspect of
this
embodiment, this assumes the use of a dedicated fiber optical protection
technique
Stleb. 145 LTPSR.
FIG. 6 illustnnes a drop unit 600 according, to an embodiment of the present
invention. The drop unit 600 may he implemented as One of she drop units
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illustrated in FIGS. 3 and 4. The optical directivity element 610 may be used
to
direct wavelengths (MXIP) arriving via a fiber 605 on the multi-wavelength
input
port 607 to its various multi-wavelength output ports 615. This may be
achieved
through the utilization of apical switches, optical couplers. or other
appropriate
s technologies (not shown). The wavelengths exiting the lower multi-
wavelength
output port 617 of the optical directivity element 610 are sent to a wpm de-
multiplexer 620, The WM/ de-multiplexer 620 de-multiplexes the WDIV1 signal
into its individual wavelengths (S).DP/ - SIDPN) and directs each wavelength
to a
specific individual fiber. fiecause there are N possible wavelengths carried
within
ie the multi-wavelength parts, the dc-multiplexer 620 supports up in N
"drop" fibers
630, Wavelengths (WOE/ ¨ ?MORK 1) that arc not dropped may be directed via
output fibers 640 to one or more of the other multi-wavelength output ports
615 on
the drop unit 600.
FIG. 7 illustrates an add unit 700 according to an embodiment of the present
invention. The add unit 700 may be implemented as one of the add units
illustrated
in FIGS. 3 and 4. A set of WDM de-multiplexers 710 (such its an Arrayed
Waveguide Grating (AWG)) arc used to de-multiplex the wavelengths (M1J14/ ¨
MXI.F'K) arriving on multi-wavelength input ports 705 into individual
wavelengths
XN). The wavelengths are then sent to a set off,/ K-to-1 optical switches 720,
ra In some embodiments, there is one switeh associated with each of The N
wavelengths. Therefore, the source of a given wavelength OR a multi-wavelength
output port 750 of a WI)M multiplexer (MT.JX) 740 can come from any of the le.-
1
multi-wavelength input ports 705 or from the individual single wavelength add
ports
707. as shown, Once the switches select a given wavelength, the selected
25 wavelengths can be "power balanced" via the set of N adjustable
attenuators 730.
FIG. 8 illustrates a 2-clegree node 800 with two ROls 81 0a, 81 Ob. each
including both an add unit 820a, 820b and a drop unit 830a, 8301).
FIG. 9 illustrates a 3-degree node 900 with three ROls 910a, 91 Ob, 910c,
each including both an add Unit 920a, 920b, 920c and a drop unit 930e. 930b,
930c.
FIG. 10 illustrates a 4-degree node 1000 with four ROIs 1010; 1010b,
1010e, 1010d, each including both an add unit 1020a. I020b, 1020cõ 1020d and a
drop unit 1Q30; 1030b, 1030e, 10304.
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FIG, II illustrates a single nag network design 1100 utilizing 2-degree nodes
1110a-f. Tic network 1100 includes dual "counter-rointing" rings 1105a, 1105b,
Dual counter rotating rings are used in dedicated protection techniques such
tts
UPSR. A bi-directional connection between two nodes (e.g., nodes 1110a and
FIG. 12 shows an example network having working and protection
WDM equipment within a given WDM node can only support a futile
number a wavelengths (e.g., 4 wavelengths, 3 wavelengths, or 12 wavelengths,
25 bidireetiOnal counections between ever) pair of nodes (e.g., using UPSR
protection).
As illustrated in Table 1 below, a total of fifteen wavelengths are needed to
establish
all the connections.
Connection Wavelength Number Ring
A-14--
A 1 main Outer Ring
A-C X 2 Main Outer Ring
A-D 1 Main Outer Ring
A-E X 4 Math Outer Ring
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A-F X 5 Main Outer Ring
B-C X 6 Main Outer Ring
B-I) X 7 Main Outer Ring
B-E X 8 Main Outer Ring
A-F X 9 Main Outer Ring
C-D X 10 Ivtairs Outer Ring
CE X 11 Main outer Ring
X 12 Main Outer Ring
D-F X 13 Main outer Ring
D-F X 14 Main Outer Ring
E-F. - _______________________
X 15 Main Outer Ring
Table 1
FIG. 13 illustrates a network 1300 where nodes B, C. D. and F flora FIG. 12
are replaced with 3-clegrec nodes. In this embodiment, two "isolated" 11lb-
rings are
formed: Sub-Ring 1310 and Sub Ring3 1330. These sub-rings may be referred to
s as -hiulated sub-rirt8S" because they share no common ring sections.
Another sub-
ring, Sub-Ring 2 1320, is also formed. In FIG. 13, Sub-Ring 3 1330 includes
the
sub-ring fonued by nodes A. B, and C; Sub-Ring 1 1310 includes the sub-ring
formed by nodes ID, B. and F; and Sub-Ring 2 1320 includes she sub-ring formed
by
nodes B, C, D, and F. Sub-rings that arc isolated from 013C another (e.g. Sub-
Rings
1 and 3) may use the same wavelengths to establish connections between the
nodes
of their associated sub-rings. For ingranCe, in FIG. 13 a connection may be
established between nodes D and E on Sub-Ring 11310 using wavelength number I
(Al), while this same wavelength number 1 (41) can simultaneously be used to
establish a connection between nodes A and B on Sub-Ring 3 1.330.
Aq an rxtimpIe of hew the number of wavelengths may be reduced by
utilizing the four 3-degree nodes. suppose that a network such as she network
1300
shown in FIG. 13 is used so establish folly protected bidirectional
connections
between every pair of nodes (e.g., using UPSR protection). As illustnned in
Table 2
below, a total of twelve wavelengths may he used to establish all the
connections.
Therefore, three wavelern,,,tlis are saved by using the 3-degree nodes shown
in FIG.
13 (as compared to using only 2-degree nodes). In this example, Sub-Ring 1 and
Sub-Ring 3 use three wavelengths in common, namely wavelength numbers 1, 2,
aria 3.
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Connection Wavelength NOMber Ring
A-B X 1. Sub-Ring 3
A-C X 2 Sub Ring 3
¨,---
A-D X 4 Main Outer Ring
A-E X 5 IViain Outer Ring
A-F X 6 Main OW= Ring
13-C X 3 Sub-Ring 3
B-D X 7 MairiZwer Ring
.13-E A 8 Main 01;icr Ring
B-F X 9 Main Outer Ring
C-D A10
Main Outzr Ring
C-13 All Main Outer Ring
C-F X12 Main Outer Ring
D-B X 1 Sub-Ring 1
D-F X 2 Sub-Ring
_______________________________________________ -
E-F X 3Sub-Ring 1
'Lit-707-- ¨
Sub-Ring 1 1310 and Sub-Ring 3 1330 may 0Se the same wavelengths for
communications between their nodes because they are isolated from each other
(e.g.,
s wavelength number 1 (X1) is used for communications between both nodes A
and B,
and D and E). Sub-Ring 2 1320 may not use thc same wavelengths as Sub-Ring I
1310 or Sub-Ring 3 1330 because Sub-Ring 2 1320 ShaZeS network paTINin
common with Sub-Ring 1 1310 and Sub-Ring 3 1330 (e.g., the paths between nodes
B end C, and the paths between nodes D and F), instead, Sub-Ring 2 1320 must
use
is wavelengths that arc not used by either Sub-Ring 33310 or Sub-Ring 3
1330 (e.g.,
wavelength number 7 (X7) is used for communications between nodes 13 and D).
Communications berwcen nodes of clilYerent sub-rings coniuninications along
a
main atm ting 1340) must use wavelengths that are not used by any of the sub
rings (e.g., wavelength number 4 (14) is used for communications between nodes
A
13 and D),
FIG. 14 illustrates a network 1400 where nodes B. C. I), and F from FIG. 12
are replaced with 4-degree nodes with the extra degrees used to create two
additional
links using ber pairs dimmed from node B to node C and from node 1) to node F.
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In this embcxliment, three -isolated" 51k-ritle5 ;Ire formed: Sub-Ring 1 1410,
Sub-
Ring 2 1420, and Sub-Ring 31430. In FM. 14, Sub-Ring 3 1430 includes the sub-
ring formed by nodes A, B, and C using vertical fiber paths T .and V. Sub-king
2
1420 includes a sub-ring formed by nodes B. C. D. and F using vertical fiber
paths
s W and X. Sub-Ring I 1410 includes a sub-ring formed by nodes E. and F
using
vcrticel fiber paths Y and Z.
LU1 exarnple of how the number or wavelengths may be reduced by
utilizing the four 4-clegroe nodes. suppoge that a network such as the
zuttwork 1400
shown in FIG. 14 .S used To establish fully protected bidirectional
connections
to between every pair of nodes (e.g., using MISR protection). As
illustrated in Table 3
below, a total of nine wavelengths may be used to establish all the
connections.
Therefore, six wavelengths are saved by using the 4-degree nodes shown in FIG.
14
(.4$ Compared to using only 2-degree nodes). In this example. Sub-Ring 1. Sub-
Ring
2, and Sub-Ring 3 use three wavelengths in common, namely wavelength numbers
15 1, 2, and 3.
Connection Wavelength Number Ring
A-B 1 Sub-Ring 3
A-C ;c. 2 Sub-Ring 3
A-D 13 Main Outer Ring
A-E 6 Main Outer Ring
A-14 A 7 Main Outer Ring
D-C 13 Sub-Ring 3
13-D A 1 Sub-Ring 2
13-E 18 Main Outer Ring
B-F 12 Sub-Ring 2
C-C) 13 Sub-Ring 2
C-F 19 Main Outer Ring
C-F 14 Sub-Ring 2
D-E 11 Sub-Ring I
D-F A 2 Sub-Ring 1
Sub-Ring-1
____________________ ¨
Table 3
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Because each sub-ring is isolated from the other sub-rings, the same
wavelengths may be used in each of the sub-rings (e.g, wavelength number 1
Q.1)
may be used for communications berween nodes A and B. nodes B and D, and nodes
D and E). Sub-Ring 2 1420 uses tui additional wavelength because it includes
foot
s nodes (e.g., wavelength number 4 (X.4) may be used for communications
between
nodes C and F). It should be noted that ?A can be reused in sub-ring 3 in
order to
transport additional traffic between two nodes on sub-ring 3. Similarly, A.4
can he
reused in 5;b-ring] in order to transport additional 'traffic between two
nodes on
sub-ring 1. Communications between nodes of different sub-rings must use
to wavelengths that are not used by any of the sub-rings (e.g., wavelength
number
(KS) is used for communications between nodes A and E).
Additional isolated sub-networks may be created by adding To the network
1400 an even number ot paths that couple at least two of the mufti-degree
nodes.
For example, in FIG. 14, an additional isolated sub-ring may be created with
an
15 addition of two paths that couple any two of the 4-degiee nodes. Both of
the newly
coupled nodes thug become 6-degree nodes.
FIGS_ 15-18 illustrate how multi-degree nodes may be added to an existing,
single ring, DWDIvt network to create additional sub-ring networks to reduce
the
number of wavelengths needed for communications in the network.
20 rio. 15 is an illustration of an exisTing, single ring, Dw-Dm network
1500
cOntAining nodes A-L. Many wavelengths are needed for communications between
the nodes_ A thick dashed line illustrates an exemplary ring 1510 within the
network.
FIQ. 16 illustrates a designation 1610, 1620, 1630 and 1640 of nodes C. F.
25 and K. respectively. in Ring 1 that arc replaced with 4-degree nodes
FIG. 17 illustrateT.,anaddition of."eut-throlighbers= 1710,- 1-720 rola= tiug
The new 4-degree nodes C, E, 1, and K. Two fiber pairs may be used for each
cut-
Tluougli to prevent wavelength blocking by creating isolated sub-networks. The
addirion of the cut-throughs creates three, new, isolated sub-network rings
1730.
39 1740, 1750.
FIG. 18 is a perspective of the resulting DWDM network that contains a Total
of four rings. Rings 1-3 1730. 1740, 1750 are The newly created rings, while
Ring 4
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1510 is the original. Network traffic may be routed so that each demand
traverses
only one ring. This reduces the number of wavelengths that are needed for
communications in the network.
In the description above, for purposes of explanation, specific nomenclature
is
set forth to provide a thorough understanding of the embodiments of the
present
invention. However, it will be apparent to one skilled in the art that
specific details in
the description may not be required to practice the embodiments of the present
invention. In other instances, well-known components are shown in block
diagram
form to avoid obscuring embodiments of the present invention unnecessarily.
In the foregoing specification, embodiments of the invention have been
described with reference to specific exemplary embodiments thereof. The scope
of the
claims should not be limited by particular embodiments set forth herein, but
should be
construed in a manner consistent with the specification as a whole. The
specification
and drawings are, accordingly, to be regarded in an illustrative rather than
restrictive
sense.
While this invention has been particularly shown and described with
references to preferred embodiments thereof, it will be understood by those
skilled in
the art that various changes in form and details may be made therein without
departing from the scope of the invention encompassed by the appended claims.
