(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0105692 A1
`(43) Pub. Date:
`Aug. 8, 2002
`Lauder et al.
`
`US 20020105692A1
`
`(54) HIERARCHICAL WDM IN CLIENT-SERVER
`ARCHITECTURE
`
`(52) Us. 01. .......................................... .. 359/124; 359/119
`
`(76) Inventors: Richard Lauder, Maroubra (AU); Ross
`Halgren, Collaroy Plateau (AU)
`
`(57)
`
`ABSTRACT
`
`Correspondence Address:
`CHRISTIE, PARKER & HALE, LLP
`350 WEST COLORADO BOULEVARD
`SUITE 500
`PASADENA, CA 91105 (US)
`
`(21) Appl. No.:
`
`09/779,185
`
`(22) Filed:
`
`Feb. 7, 2001
`
`Publication Classi?cation
`
`(51) Int. Cl.7 ......................... .. H04B 10/20; H04J 14/00;
`H04] 14/02
`
`An optical ring network comprising; a plurality of network
`elements including a core network elernent interfacing the
`ring network with an external core network, and at least one
`ring network elernent; wherein the core network element
`includes a ?rst CWDM unit, a ?rst DWDM unit and
`switching rneans arranged to cross connect any wavelength
`channel within or between wavelength bands on the ring
`network or between the ring network and the core network,
`and wherein the ring network elements each include, a
`second CWDM unit and a second DWDM unit, the second
`CWDM unit being arranged to add/drop at least a ?rst
`wavelength band at said ring network element from and to
`the second DWDM unit and to express other wavelength
`bands onto the neXt network elernent
`
`IO
`
`\N
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-1
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 1 0f 14
`
`US 2002/0105692 A1
`
`1 band 1
`
`/
`
`IA
`
`Figura 1
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-2
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 2 0f 14
`
`US 2002/0105692 A1
`
`To Core Network
`
`10
`
`Core Hub
`
`Figure 2
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-3
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 3 0f 14
`
`US 2002/0105692 A1
`
`To Core Network
`
`Core Hub
`
`7L Band 1
`
`r/O
`
`A Band 2
`
`A Band 4
`
`7* 8am‘ 5
`
`Figure 3
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-4
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 4 0f 14
`
`US 2002/0105692 A1
`
`To Core Network
`
`TlTlTlTlTlTlTlTl
`
`I 3 1
`Matrix Switch
`
`Metro
`Hub2
`
`in
`
`Metro
`HubS
`
`n
`
`Metro
`Hub4
`
`A
`
`Metro
`HubS
`
`A
`
`Metro
`Hub?
`
`it
`
`Metro
`Hub7
`
`A
`
`Metro
`HubB
`
`1
`
`Core Hub
`A A
`
`A. Band 1
`
`mandz
`
`V
`
`lBandS M20
`
`V
`
`7 1m‘
`
`V
`
`lBand5
`
`183MB
`
`lBandT
`
`1Band8
`
`p/zz
`
`1
`
`V
`
`"
`
`V
`
`Figure 4
`
`!
`
`i
`
`V
`
`V
`
`\
`
`\
`
`\
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-5
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 5 0f 14
`
`US 2002/0105692 A1
`
`Cust0mer(s)
`
`Line Interface Cards
`
`A, 1+ l 5
`
`Channel Switch
`
`N q
`
`I
`
`Trunk Interface Cards N Ll I2
`
`I
`DWDM MUX/DEMUX A, q 10
`
`CWDM
`
`N Q06)
`
`Hub Bypass Switch
`
`a’ (400 5,‘
`
`Figure 5
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-6
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 6 0f 14
`
`US 2002/0105692 A1
`
`(Hg
`
`End-Customer's
`Equipment
`
`Line Interface Connections
`
`Interfaces
`
`Trunk
`Interfaces
`
`(H1 TODWDMJ‘Xt N Hr N H N H N
`
`Figure 6
`
`Figure 7A
`
`Figure 7B
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-7
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 7 0f 14
`
`US 2002/0105692 A1
`
`.
`
`I
`
`702,, 70247019; 702% 70%“
`i
`/
`/
`\-1\F//rJ></\mc
`RX
`TX
`70%},
`
`70850 70% 70st mt
`Rosa/Kb)
`702k YORQXTTX-JJYM
`
`702A
`
`‘a e
`gg ggg 7094 3
`0mg 510%
`Non-interieaved
`
`Figure 8A
`
`7ock7m> 70%1 70% 705%
`70% mo 70% (‘533
`_
`gntedeaved
`
`Figure 3B
`
`To management/ring
`
`
`
`8000p Common traffic
`
`Common traffic
`
`Figure 9
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-8
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 8 0f 14
`
`US 2002/0105692 A1
`
`OQtion 1:
`
`CB d
`
`\'
`
`cm»,
`Hub 1f4GO=L (J Hub2
`
`ll
`0:00;
`j “gjnmi-liubj‘ J
`
`f L-Band
`‘wool
`C HLib4 I
`
`I
`
`\
`
`W‘ m 11W I W ‘M
`W WWW Wrxlliiilllilwnmumnu i
`Rx
`i
`\w‘”
`qolb
`Tx
`W WW
`4‘ ‘M
`W ‘i
`mot Wt 133%- mm “ Cw”? 61cm qoqol
`hc
`‘106:,
`
`Ogt'
`2:
`0,531
`
`was
`
`‘Wk 0102a
`
`area 9,06 “@106 ‘"04.
`
`(#LXIbZ‘ jHubS imp;
`(Hum /yHub2\ (ITubB [f?um (JHutn
`/W W WWW ml JHllill’l'iilwlW i
`\I WWI‘ 1 M
`‘i‘
`T
`UH
`T
`1‘
`t
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`‘am
`ggqfizb “H20
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`qizb m4, m3
`
`mm Wk ‘WM ‘MB ‘met Wk 0120K C1205
`
`FCHubi
`’!
`Hill! l
`1"
`6212A
`
`[/Hubg fHt‘mvfHubz CHub8 (/Hub4 (Hubs {M74
`iliU ‘9 w ‘VTTWWWWZWWWW\
`4‘
`max mt, ‘mi, my
`
`Q1225 "Q20
`
`Figure 10
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-9
`
`

`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-10
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 10 0f 14
`
`US 2002/0105692 A1
`
`20: 5
`
`7k. bands 1,2,3
`
`gut
`
`210
`
`1, band 1
`
`//
`
`213
`
`Figure 11
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-11
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 11 0f 14
`
`US 2002/0105692 A1
`
`# To Core Network
`
`20‘
`
`Core Hub
`
`226
`
`1 Band 1
`
`J
`
`7» Band 8
`
`228
`
`Metro
`Hub 1
`
`1 Band 2
`
`236
`
`Metfo
`Hub 8
`
`222
`
`1 Band 2
`
`240
`
`242
`
`234
`
`A Band 1
`
`l
`
`2
`
`1 Band
`2
`
`Metro
`Hub 3
`
`1 Band 1
`
`224
`
`1. Band 5
`
`Metro
`Hub 6
`
`1. Band 1
`
`Metro
`Hub 4
`
`230
`
`232
`
`238
`
`Metro
`Hub 5
`
`220
`
`Figure 12
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-12
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 12 0f 14
`
`US 2002/0105692 A1
`
`‘[0 Core MM
`
`2m
`
`Figure 13
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-13
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 13 of 14
`
`US 2002/0105692 A1
`
`20!
`
`Core Network
`
`Functional Model
`Metro TX to CoreRX -
`
`,
`
`.
`
`..
`
`(Reverse for Care Tx to Metro Rx)
`
`Modulators
`
`308
`
`1.13am] l
`
`3 ‘ 0
`
`Metro Hub M Core Hub
`Switch within ll-Band
`Switch within 8: between )u-Bands
`
`Figure: 14
`
`31%
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-14
`
`

`
`Patent Application Publication
`
`Aug. 8, 2002 Sheet 14 0f 14
`
`US 2002/0105692 A1
`
`3 S IL (502m 30%
`
`T r“
`_’ Y ‘_
`
`-" 'X' —'
`
`.J'
`
`. . . . . . . . . . . .
`
`. . . . . . . . . . ..
`
`2021
`
`30!
`
`/
`2H9
`
`3 (‘f
`
`Figure 15
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-15
`
`

`
`US 2002/0105692 A1
`
`Aug. 8, 2002
`
`HIERARCHICAL WDM IN CLIENT-SERVER
`ARCHITECTURE
`
`FIELD OF THE INVENTION
`
`[0001] The present invention relates broadly to an optical
`ring network and to a method of providing Hierarchical
`Wavelength Division Multiplexing in a client-server archi
`tecture in an optical ring netWork.
`
`BACKGROUND OF THE INVENTION
`[0002] Traditionally enterprise voice and data netWorks in
`eg a metro area have developed around peer-peer oriented
`services, ring architectures and time division multiplexing
`(TDM) and time division sWitching (TDS) technologies.
`[0003] Peer-peer oriented services requirernents occurred
`since the traf?c that stayed Within the metro area was much
`greater than the traf?c Which Was destined for a remote
`metro area. Telephone Services and Storage Area NetWork
`Services are examples of such services.
`
`[0004] Ring architectures have evolved as a Way of offer
`ing path protection for high speed shared services in a metro
`area.
`
`[0005] Since TDM and TDS technologies could be easily
`integrated into loW cost Very Large Scale Integrated (VLSI)
`devices, this in the past enabled distributed access and
`sWitching betWeen any channels on a TDM ring netWork
`(such as a SONET/SDH ring). Such distributed access and
`sWitching technologies Were well matched to the peer-peer
`service orientation, since if tWo hubs on a metro ring needed
`to communicate, they could do so Without relying on cen
`tralised sWitching at a core hub.
`
`[0006] HoWever, With the emergence of optical netWorks
`as potential technology to deal With the vast amount of data
`to be carried in future netWorks, this traditional approach
`proves no longer to be effective. This is largely due to the
`cost and space required for eg a 128x128 optical cross
`connect sWitch in a 128 Wavelength ring.
`
`SUMMARY OF THE INVENTION
`[0007] Throughout the speci?cation the folloWing abbre
`viations Will be used:
`
`[0008] HWDM: Hierarchical Wavelength Division
`Multiplexing
`
`[0009] CWDM: Coarse Wavelength Division Multi
`plexing
`
`[0010] DWDM: Dense Wavelength Division Multi
`plexing
`
`[0011] The present invention seeks to provide an alterna
`tive optical ring netWork and a method of providing HWDM
`in a client-server architecture in an optical ring netWork
`Which can provide a more ?exible and cost effective solu
`tion.
`
`[0012] In accordance With a ?rst aspect of the present
`invention there is provided an optical ring netWork corn
`prising a plurality of network elements including a core
`netWork elernent interfacing the ring netWork With an exter
`nal core netWork, and at least one ring netWork elernent;
`Wherein the core netWork element includes a ?rst CWDM
`
`unit, a ?rst DWDM unit and sWitching rneans arranged to
`cross connect any Wavelength channel Within or betWeen
`Wavelength bands on the ring netWork or betWeen the ring
`netWork and the core netWork, and Wherein the ring network
`elements each include a second CWDM unit and a second
`DWDM unit, the second CWDM unit being arranged to
`add/drop at least a ?rst Wavelength band at said ring netWork
`element from and to the second DWDM unit and to express
`other Wavelength bands onto the next netWork elernent.
`
`[0013] Accordingly, the invention can provide an optical
`ring netWork With high scalability provided by the ability to
`scale to a larger number of Wavelengths at an individual ring
`netWork elernent Without impact upon other ring network
`elements by activating additional Wavelengths Within each
`CWDM Wavelength band. Additionally, it is possible to
`increase the number of ring network elements through the
`addition of CWDM Wavelength bands, again Without impact
`upon the existing ring network elements.
`
`[0014] Preferably, the second DWDM unit includes a
`dense Wavelength division dernultiplexing unit, a dense
`Wavelength division multiplexing unit and a connector
`means disposed therebetWeen and arranged, in use, in a
`manner such that Wavelength channels Within said ?rst
`Wavelength band are either dropped at the ring netWork
`element or expressed onto the next netWork element, and
`such that other Wavelength channels Within said ?rst Wave
`length band are added.
`
`[0015] Advantageously, the connector means is further
`arranged in a manner such that, in use, it is recon?gurable to
`selectively express, drop, or add a particular Wavelength
`channel Within said ?rst Wavelength band.
`
`[0016] The connector means may comprise n 2x2 optical
`sWitches or a single 2n><2n optical sWitch, Where n is the siZe
`of the dense Wavelength dernultiplexer and rnultiplexer
`units.
`
`[0017] In accordance With a second aspect of the present
`invention there is provided a ring netWork element for use in
`an optical ring netWork having a core netWork elernent
`interfacing the ring netWork With an external core netWork,
`the ring netWork elernent comprising a CWDM unit and a
`DWDM unit, the CWDM unit being arranged to add/drop at
`least a ?rst Wavelength band at said ring netWork element
`from and to the DWDM unit and to express other Wave
`length bands onto the next netWork elernent.
`
`[0018] Preferably, the DWDM unit includes a dense Wave
`length division dernultiplexing unit, a dense Wavelength
`division multiplexing unit and a connector means disposed
`therebetWeen and arranged, in use, in a manner such that
`Wavelength channels Within said ?rst Wavelength band are
`either dropped at the ring netWork element or expressed onto
`the next netWork element, and such that other Wavelength
`channels Within said ?rst Wavelength band are added.
`
`[0019] Advantageously, the connector means is further
`arranged in a manner such that, in use, it is recon?gurable to
`selectively express, drop, or add a particular Wavelength
`channel Within said ?rst Wavelength band.
`
`[0020] The connector means may comprise n 2x2 optical
`sWitches or a single 2n><2n optical sWitch, Where n is the siZe
`of the dense Wavelength dernultiplexer and rnultiplexer
`units.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-16
`
`

`
`US 2002/0105692 A1
`
`Aug. 8, 2002
`
`[0021] In accordance With a third aspect of the present
`invention there is provided a method of providing HWDM
`in an optical ring netWork comprising a plurality of netWork
`elements including a core netWork element interfacing the
`ring netWork With an external core netWork, and at least one
`ring netWork element; the method comprising the steps of
`utilising CWDM and DWDM techniques at the core net
`Work element to cross connect any Wavelength channel
`Within or betWeen Wavelength bands on the ring netWork or
`betWeen the ring netWork and the core netWork, and utilising
`CWDM techniques at each ring netWork element to add/
`drop at least a ?rst Wavelength band at said ring netWork
`element and to express other Wavelength bands onto the next
`netWork element
`
`[0022] Preferably, the method further comprises the step
`of utilising DWDM techniques at the ring netWork elements
`to drop certain Wavelength channels Within said ?rst Wave
`length band at the ring netWork element, to express other
`Wavelength channels Within said ?rst Wavelength band on to
`the next netWork element, and to add Wavelength channels
`Within said ?rst Wavelength band from the netWork element.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0023] Preferred forms of the present invention Will noW
`be described, by Way of example only, With reference to the
`accompanying draWings.
`[0024] FIG. 1 is a schematic draWing illustrating the
`connectivity of a metro ring embodying the present inven
`tion.
`
`[0025] FIG. 2 is a schematic draWing illustrating the
`physical representation of a metro ring of FIG. 1.
`
`[0026] FIG. 3 is a schematic draWing illustrating the
`logical connectivity of the metro ring of FIG. 1.
`
`[0027] FIG. 4 is a schematic draWing illustrating the
`logical connectivity of the metro ring of FIG. 1 in an
`alternative form.
`
`[0028] FIG. 5 Optical units Within metro hub embodying
`the present invention.
`
`[0029] FIG. 6 Line interface, channel sWitch, and trunk
`interface cards embodying the present invention.
`
`[0030] FIG. 7 Possible DWDM Con?gurations embody
`ing the present invention.
`[0031] FIG. 8 DWDM Wavelength maps—interleaved
`and non-interleaved embodying the present invention.
`
`[0032] FIG. 9 CWDM interfaces embodying the present
`invention.
`
`[0033] FIG. 10 CWDM band allocation embodying the
`present invention.
`
`[0034] FIG. 11 is a schematic draWing illustrating the
`connectivity of another metro ring embodying the present
`invention.
`
`[0035] FIG. 12 is a schematic draWing illustrating the
`logical connectivity of the metro ring of FIG. 11.
`
`[0036] FIG. 13 is a schematic draWing illustrating the
`logical connectivity of the metro ring of FIG. 11 in an
`alternative form.
`
`[0037] FIG. 14 is a schematic draWing illustrating the
`functional layers of sWitching, multiplexing and transmis
`sion for a particular metro to core hub connection in the
`metro ring of FIG. 11, representative of a method of
`providing HWDM in a client-solver architecture, embody
`ing the present invention.
`
`[0038] FIG. 15 is a schematic draWing illustrating a detail
`of one functional layer of FIG. 14.
`
`DETAILED DESCRIPTION OF THE
`EMBODIMENTS
`
`[0039] In the preferred embodiment described an optical
`ring netWork is provided Which exhibits high scalability
`provided by the ability to scale a larger number of Wave
`lengths at a ring netWork element Without impact on other
`ring netWork elements by activating additional Wavelengths
`Within a CWDM Wavelength band. Additionally, it is pos
`sible to increase the number of ring netWork elements
`through the addition of CWDM Wavelength bands, again
`Without impact on the existing ring netWork elements.
`
`[0040] FIG. 1 shoWs a schematic of an optical metro ring
`netWork 10 Wherein each metro hub eg 12 includes a
`CWDM unit 14 and a DWDM unit 16. Each CWDM unit
`eg 14 is a band-pass ?lter that Will drop eg a single
`Wavelength band and has a transit path that Will express
`through all other Wavelengths. The core hub 13 contains a
`CWDM unit 15, a DWDM unit 17 and a sWitch 19 for cross
`connecting any Wavelength channel eg 21 Within or
`betWeen Wavelength bands eg 20, 22 on the metro ring
`netWork 10 or, additionally, betWeen the metro Ad ring
`netWork 10 and an external core netWork (not shoWn).
`
`[0041] The system disclosed is scalable in tWo Ways. First,
`the activation of Wavelengths Within each CWDM band
`enables the capacity of each individual metro hub to be
`increased Without affecting other metro hubs. Second, the
`addition of further CWDM Wavelength bands alloWs further
`metro hubs to be added Without impacting the existing metro
`hubs. Thus the scalability of such a system is restricted only
`be physical limitations, such as eg the bandWidth of the
`express ?lters, the total available Wavelength range, and
`limitations on hoW closely Wavelength channels may be
`spaced Within each CWDM Wavelength band.
`
`[0042] In FIG. 2 the metro ring netWork 10 (expanded to
`more metro hubs) is shoWn in a physical representation, and
`FIG. 3 shoWs it’s logical connectivity. Each Wavelength
`band eg 20 in FIGS. 2 and 3 is transmitted both Ways
`around the netWork to enable full 1+1 protection.
`
`[0043] The metro ring netWork 10 is further represented in
`FIG. 4 as a client server architecture. As can be seen the
`sWitching required to maintain connectivity betWeen bands,
`eg 20, 22 is contained at the core hub 13. SWitching at the
`metro hubs may be used for channel protection or time-of
`day multiplexing and provisioning bandWidth on demand,
`but is not required to perform the transmission function.
`
`[0044] FIG. 5 is a block diagram that shoWs schematically
`the major units that comprise a metro hub eg 14 in the
`metro ring netWork 10 (FIGS. 1 to
`FIG. 5 shoWs the
`logical layout for the different units the optical signal passes
`through. Each of these units is discussed in the folloWing
`paragraphs.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-17
`
`

`
`US 2002/0105692 A1
`
`Aug. 8, 2002
`
`[0045] FIG. 6 is a block diagram that shows schematically
`the con?guration of the Line Interface Cards 416, Channel
`Switch 414 and Trunk Interface cards 412 in a metro hub
`con?gured for use in the metro ring netWork 10 (FIGS. 1 to
`4). Each Line Interface Card 416 provides a duplex connec
`tion to a Customer Equipment Unit 418, and is connected to
`a single Trunk Interface Card 412 according to the con?gu
`ration of the Channel SWitch 414. In the hub con?guration
`shoWn in FIG. 6, the hub is capable of providing M:N
`channel protection, in Which M+N Trunk Interface Cards
`412 are provided to connect only N Line Interface Cards
`416. Thus up to M trunk failures can be restored by
`sWitching the corresponding Line Interface Cards 416 to an
`unused Trunk Interface Card 412 by recon?guring the
`Channel SWitch 414.
`
`[0046] Each Trunk Interface Card 412 requires a suitable
`single-frequency DWDM laser for transmission of the trunk
`signal into the netWork via the DWDM MUX/DEMUX Unit
`410, the CWDM Unit 406, the Management MUX/DEMUX
`Unit 402 and the Hub Bypass SWitch 400. Depending upon
`factors such as, e.g., the channel bit-rate and the maximum
`transmission distance, this laser may be a relatively loW-cost
`device, such as a directly modulated, temperature-stabilised
`distributed feedback (DFB) semiconductor laser. Alterna
`tively the laser may be a more costly, higher-performance
`device, such as a DFB semiconductor laser incorporating an
`integrated external electro-absorption modulator (DFB-EA),
`and active Wavelength stabilisation, in order to achieve
`higher bit-rate, longer transmission distance, or more closely
`spaced DWDM channels. In a further alternative embodi
`ment, the DWDM laser source may be provided separately
`from the modulator. as Will be described later With reference
`to FIG. 14.
`
`[0047] As shoWn in FIG. 6, each Trunk Interface Card 412
`is connected by a pair of ?bres to the DWDM MUX/
`DEMUX Unit 410 (FIG. 5). Each ?bre connecting a Trunk
`Interface Card 412 to the DWDM Unit 410 carries a single
`Wavelength in one direction. Half of these Wavelengths Will
`carry data transmitted from the hub and half Will carry data
`to be received at the hub. An exemplary embodiment is
`described here, in Which there are 16 full-duplex channels at
`each hub comprising 16 transmitted (TX) Wavelengths and
`16 received (Rx) Wavelengths, ie a total of 32 different
`Wavelengths. HoWever, it Will be appreciated that a greater
`or smaller number of channels could be accommodated
`Without departure from the scope of the present invention.
`The DWDM Unit 410 receives the 16 TX channels from the
`Trunk Interface Cards 412 and multiplexes them onto a
`single ?bre. It also receives the 16 Rx channels on a single
`?bre from the CWDM Unit 406 and demultiplexes them to
`the 16 Rx ?bres connected to the Trunk Interface Cards 412.
`
`[0048] Advantageously, the hub may comprise additional
`Trunk Interface Cards 412 to provide a number of protection
`channels per direction. In this con?guration, M:N channel
`protection is supported, Where N=16 for the exemplary
`embodiment, and M is the number of additional Trunk
`Interface Cards 412 provided.
`
`[0049] Turning noW to FIGS. 7A and 7B, Which shoW
`schematically tWo exemplary embodiments of the DWDM
`MUX/DEMUX Unit 410. In the ?rst exemplary embodi
`ment, FIG. 7A, the DWDM MUX/DEMUX Unit 410 com
`prises internally separate optical multiplexing means 606
`
`and demultiplexing means 608, and comprises externally a
`unidirectional input ?bre 600 and a unidirectional output
`?bre 602. In the second exemplary embodiment, FIG. 7B,
`the DWDM MUX/DEMUX Unit 410 comprises internally a
`single optical multiplexing and demultiplexing means 610,
`and comprises externally a single bi-directional input/output
`?bre 604 In either embodiment the optical multiplexing and
`demultiplexing means may be, eg a free-space diffraction
`grating based device, or a planar lightWave circuit based
`device such as an arrayed Waveguide grating. It Will be
`appreciated that other embodiments of the DWDM MUX/
`DEMUX Unit 410, and other optical multiplexing and
`demultiplexing means, may be employed Without departing
`from the scope of the present invention.
`[0050] The DWDM Wavelength Map is the allocation of
`Tx and Rx channels to speci?c Wavelengths for transmission
`on one or more ?bres in the optical ring netWork. FIGS. 8A
`and 8B shoW schematically tWo exemplary embodiments of
`a DWDM Wavelength Map in Which there are eight Rx
`channels, 702a-h and 706a-h, and eight Tx channels, 704a-h
`and 708a-h. It Will be appreciated that different numbers of
`Tx and Rx channels, and other DWDM Wavelength Maps
`may be employed Without departing from the scope of the
`present invention.
`[0051] The exemplary embodiment shoWn in FIG. 8A is
`referred to as a non-interleaved Wavelength map, because
`the Rx Wavelengths 702a-h occupy a Wavelength band that
`is disjoint from the Wavelength band occupied by the Tx
`Wavelengths 704a-h. The exemplary embodiment shoWn in
`FIG. 8B is referred to as an interleaved Wavelength map,
`because the Rx Wavelengths 706a-h alternate With the Tx
`Wavelengths 708a-h Within the same Wavelength band. It
`Will be appreciated that other Wavelength maps may be
`constructed by combining bands comprising different num
`bers of interleaved and non-interleaved Wavelengths Without
`departing from the scope of the present invention.
`[0052] A non-interleaved Wavelength map may be used to
`simplify netWork operation and management, and relax
`tolerances on components to reduce costs, by grouping Rx
`Wavelengths 702a-h and Tx Wavelengths 704a-h so that they
`may easily be separated from each other, eg for routing or
`ampli?cation, by simply using a coarse optical ?lter. An
`interleaved Wavelength map may be used to enable Rx
`Wavelengths 706a-h and Tx Wavelengths 708a-h in a single
`?bre to be packed more closely together, thus increasing the
`total capacity of the netWork. This increase in packing
`density is achieved because crosstalk may occur, eg at
`?lters and in transmission, betWeen closely-spaced Wave
`lengths that are propagating in the same direction, hoWever
`crosstalk is minimal betWeen Wavelengths propagating in
`opposite directions. Thus interleaving alloWs the spacing
`betWeen Wavelengths propagating in one direction to be
`Wide enough to minimise crosstalk (eg 50 GHZ), Whereas
`the spacing betWeen adjacent counterpropagating channels
`is reduced to half this value (eg 25 GHZ), effectively
`doubling the capacity of the ?bre.
`[0053] Advantageously, interleaved and non-interleaved
`Wavelength mapping techniques may be employed in a
`single netWork in order to obtain the bene?ts of simpli?ed
`operation and management, reduced costs, higher capacity,
`or a trade-off amongst these, as required.
`[0054] The CWDM Unit 406 adds/drops the appropriate
`Wavelength blocks for the hub and passes all other express
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-18
`
`

`
`US 2002/0105692 A1
`
`Aug. 8, 2002
`
`traf?c by the hub. FIG. 9 shows schematically the logical
`connections to, from and Within the CWDM Unit 406. The
`CWDM Unit 406 has tWo trunk ?bre connections 800a,
`800b to the optical ?bre ring via the Hub Bypass SWitch 400
`(FIG. 5). These tWo trunk ?bres 800a, 800b correspond to
`the tWo directions around the ring. Note that signals propa
`gate bi-directionally on each of these ?bres 800a, 800b, and
`that one direction around the ring corresponds to a primary
`path, and the other to a secondary path to provide protection.
`Therefore in a minimal con?guration, only one transmission
`?bre is required betWeen each pair of adjacent hubs. The
`netWork is therefore able to provide bi-directional transmis
`sion and protection on a ring comprising single ?bre con
`nections.
`[0055] The CWDM Unit 406 also has tWo ?bre connec
`tions 802a, 802b to the DWDM MUX/DEMUX Unit 410
`(FIG. 5), optionally via a Fibre Protection SWitch 408. One
`function of the CWDM Unit 406 is to demultiplex blocks of
`Wavelengths received on the trunk ?bre connections 800a,
`800b and transfer them to the hub via the ?bre connections
`802a, 802b. A second function of the CWDM Unit 406 is to
`accept blocks of Wavelengths transmitted by the hub via the
`?bre connections 802a, 802b and multiplex them onto the
`trunk ?bre connections 800a, 800b. A third function of the
`CWDM Unit 406 is to pass all trunk Wavelengths received
`on the trunk ?bre connections 800a, 800b Which are not
`demultiplexed at the hub across to the opposite trunk ?bre
`connection 800b, 800a via the Express Traf?c path 804.
`Advantageously, the CWDM Unit 406 should provide high
`isolation, i.e. signals destined for the hub traf?c ?bres 802a,
`802b should not appear in the Express Traf?c path 804 and
`vice versa, and should have loW insertion loss, i.e. ring traf?c
`passing betWeen the trunk ?bres 800a, 800b via the Express
`Traf?c path 804 should experience minimum attenuation.
`[0056] The allocation of the Wavelength bands that are
`added and dropped by the CWDM Unit 406 (FIG. 5)
`determines the logical connectivity of the netWork and the
`number of channels allocated to the hubs. A number of
`exemplary CWDM Band Allocation schemes are noW dis
`closed. These exemplary schemes are based on using the
`conventional transmission band, referred to as “C-Band”,
`Which spans the Wavelength range from around 1530 nm to
`1560 nm, or additionally using the long-Wavelength trans
`mission band, referred to as “L-Band”, Which spans the
`Wavelength range from around 1580 nm to 1610 nm. In
`these exemplary allocation schemes the Wavelength spacing
`is assumed to be 50 GHZ (approximately 0.4 nm). It is
`further assumed that each hub comprises 16 Trunk Interface
`Cards 412 (FIG. 5) and 16 Line Interface Cards 416 (FIG.
`2), and thus requires 16 Tx Wavelengths and 16 Rx Wave
`lengths. It Will be appreciated that other transmission bands,
`alternative Wavelength spacings, and hubs With different
`numbers of Trunk Interface Cards 412 (FIG. 5) and Line
`Interface Cards 416 (FIG. 5), may be employed Without
`departing from the scope of the present invention.
`[0057] The CWDM Band Allocation determines the num
`ber of hubs that can transmit and receive on a single ?bre
`ring. The options available include:
`[0058] using C-Band;
`[0059] using C+L-Bands;
`[0060] using a single continuous Wavelength band
`comprising both Tx Wavelengths and Rx Wave
`lengths;
`
`[0061] using separate Wavelength bands comprising
`Tx Wavelengths and Rx Wavelengths;
`
`[0062] If C-Band only is used then tWo hubs may be
`accommodated on a single ?bre. If C+L-Bands are used then
`four hubs may be accommodated on a single ?bre. If
`additional hubs are required, then further Tx and Rx chan
`nels can be provided using the same Wavelengths Within the
`C- and L-bands transmitted on additional ?bres. It Will be
`appreciated that, although in the example presented here 16
`Tx channels and 16 Rx channels are provided at each hub,
`there is a trade-off betWeen the number of hubs supported,
`the number of Tx and Rx channels per hub, and the number
`of ?bres required.
`
`[0063] FIGS. 10A-C illustrates schematically three exem
`plary allocation schemes based on the use of C+L-Bands to
`support four hubs. In FIG. 10A each hub is allocated a
`single continuous Wavelength band 900a-a' comprising both
`Tx Wavelengths and Rx Wavelengths. Within each CWDM
`Band 900a-a' the shorter Wavelengths are allocated to Rx
`channels 902a-a' and the longer Wavelengths are allocated to
`Tx channels 904a-a'. The CWDM Bands 900a-a' are sepa
`rated by Guard Bands 906a-c Which alloW for the ?nite
`roll-off rate at the edges of the CWDM Band ?lters to
`minimise crosstalk betWeen bands.
`
`[0064] In FIG. 10B each hub is allocated a Wavelength
`band 908a-a' Within the C-Band for Rx Wavelengths and a
`Wavelength band 910a-a' Within the L-Band for Tx Wave
`lengths. The CWDM Bands 908a-d, 910a-a' are separated by
`Guard Bands 912a-g Which alloW for the ?nite roll-off rate
`at the edges of the CWDM Band ?lters to minimise crosstalk
`betWeen bands.
`
`[0065] In FIG. 10C each hub is allocated tWo separate
`Wavelength bands Within either the C-Band or L-Band for
`Tx Wavelengths and Rx Wavelengths. Hub 1 and Hub 2 are
`allocated one band each 914a, 914b Within the C-Band for
`Rx Wavelengths, and another band 916a, 916b Within the
`C-Band for Tx Wavelengths. Hub 3 and Hub 4 are allocated
`one band each 918a, 918b Within the L-Band for Rx
`Wavelengths, and another band 920a, 920b Within the
`L-Band for Tx Wavelengths. The CWDM Bands 914a, 914b,
`916a, 916b, 918a, 918b, 920a, 920b are separated by Guard
`Bands 922a-g Which alloW for the ?nite roll-off rate at the
`edges of the CWDM Band ?lters to minimise crosstalk
`betWeen bands.
`
`[0066] With any of these exemplary allocation schemes,
`the total number of channels may be increased by deploying
`additional hubs and a corresponding number of additional
`?bres.
`[0067] The Hub Bypass SWitch 400 (FIG. 5) physically
`connects the ring to the hub and is also used to sWitch the
`hub out of the ring While still passing ring traffic.
`
`[0068] In FIG. 11, the addition of a recon?gurable optical
`add/drop multiplexer (ROADM) to a metro ring netWork
`201 con?guration in another preferred embodiment is shoWn
`in a logical con?guration. In place of a terminal DWDM unit
`at the metro hubs eg 209 (compare FIG. 1), there are tWo
`such mux/demux units 202, 210, connected by a connector
`unit 211. This enables a Wavelength channel Within a par
`ticular band to be expressed on to the next node using this
`band. This therefore alloWs more than one node to use the
`same CWDM band, in FIG. 11 hubs 209 and 213. This
`
`Petitioner Ciena Corp. et al.
`Exhibit 1018-19
`
`

`
`US 2002/0105692 A1
`
`Aug. 8, 2002
`
`enables the HWDM system to be much more ?exible and
`scalable. In conjunction With loW-cost optical add/drop
`multiplexers used Where only a single duplex channel is
`required to be dropped then a system that meets the com
`bined need for loW-up front cost and ?exible scalability to
`high capacity is being provided.
`[0069] FIG. 12 shoWs the logical connection of the metro
`ring netWork 201 (expanded to more, metro hubs). The
`metro ring netWork 201 includes metro hubs 220 and 222,
`each of Which use individual Wavelength bands 224, 226,
`With no other metro hub using those same respective bands
`224, 226. Furthermore, the metro ring netWork 201 com
`prises tWo groups of metro hubs, Wherein each group of
`metro hubs uses the same Wavelength band but different
`Wavelength channels Within those bands.
`
`[0070] More