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`US 20(120105692A1
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0105692 A1
`
`Lauder ct al.
`(43) Pub. Date:
`Aug. 8, 2002
`
`[54)
`
`l-llERARCi-IICAL WDM 1N CLIENT-SERVER
`ARCHI'I‘EC’I‘U RE
`
`(53) US. Cl.
`
`.
`
`.
`
`.
`
`359!124: 359-1“)
`
`(75)
`
`lnvenlnrs: Richard lander. Marouhra (AU); Russ
`Hnlgren, (Tullarny Plateau (AU)
`
`(57')
`
`ABSTRACT
`
`Correspondence Address:
`CHRISTIE, PARKER 3-: HALE, [I]1
`.350 WEST COLORADO BOULEVARD
`SUITE Sill?
`PASADENA. CA 91105 (US)
`
`[2]) App]. NILE
`
`[19!779,185
`
`(32)
`
`l-'i|cd_'
`
`Feb. “I. 290!
`
`Pulillcatiun Classification
`
`[51)
`
`Int. (.‘l.7 ........................... H0413 19.120; 1104.!
`I [04.]
`
`[4.300;
`| 4.302
`
`An eplical ring ne1wnrk comprising; a pluraliiyr of network
`elements including a core network element interfacing the
`ring nelwork with an exlernai cure neiwork. and al least one
`ring nclwork elemenl; wherein [he core network elemenl
`includes a
`first
`(TWDM unil.
`a
`['Irsl DWDM unil and
`switching means arranged In ernss cenneet any wavelcnglh
`channel wilhin or helween wavelengih hands on [he ring
`network or helween [he ring network and [he cure ne1w0rk,
`and wherein [he ring nelwurk elements each include. a
`second (‘WDM unit and a second DWDM unii. the second
`(‘WDM unil being arranged in adclr'dmp al
`leasl a
`lirsl
`wavelength hand a! said ring nelwork elemenl from and [0
`the second DWDM unil and In express ulher wavelenglh
`hands (min Ihe nexl network element
`
`IO
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 1
`Exhibit 1018, Page 1
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 1 of 14
`
`US 2(Nl2l0105692 A1
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 2
`Exhibit 1018, Page 2
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 2 of 14
`
`US 2(Nl2l0105692 A1
`
`To Core Nelwom
`
`
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 3
`Exhibit 1018, Page 3
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 3 of 14
`
`US 2(Nl2l0105692 A1
`
`To Cora Network
`
`Gore Hub
`
`r/w
`
`1. Band 8
`
`Malta
`
`2L Band 7
`
`Metro
`Hub 7
`
`7L Band 1
`
`Metro
`
`1 Band 2
`
`20
`
`2L Band 3
`
`7» Band 6
`
`3:3:
`
`3. Band 4
`
`1 Band 5
`
`Metro
`Hub 4
`
`Figure 3
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 4
`Exhibit 1018, Page 4
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 4 of 14
`
`US 2002111105692 A1
`
`ToCoceNem-uk
`
`Figure 4
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 5
`Exhibit 1018, Page 5
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 5 of 14
`
`US 2(Nl2l0105692 A1
`
`
`
`
`
`
`
`
`
`ME)
`cm
`
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`(HO
`
` HOG
`
`Hub Bypass Switch
`
`two as
`
`Figure 5
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 6
`Exhibit 1018, Page 6
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 6 0f 14
`
`US 2002111105692 A1
`
`{HQ
`
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`Endemicmer's
`Equipment
`
`Line Into-rinse Connections
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`
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`Figure 6
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`mom i
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`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 7
`Exhibit 1018, Page 7
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 7 0f 14
`
`US 200230105692 A1
`
`you 7:024:le 702k 70%“
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`8m
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`
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`m5 Common traffic
`
`3000..
`Common traffic
`
`Figure 9
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 8
`Exhibit 1018, Page 8
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 8 0f 14
`
`US 200210105692 A1
`
`
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 9
`Exhibit 1018, Page 9
`
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`
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`
`'
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 9 0f 14
`
`US 2002;0105692 A1
`
`Figure 10A
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`Ogtion 1:
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 10
`Exhibit 1018, Page 10
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 10 of 14
`
`US 2(NlZl0105692 A1
`
`20:
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 11
`Exhibit 1018, Page 11
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 11 of 14
`
`US 2(Nl2l0105692 A1
`
`To Care Netwk
`
`29‘
`
`
`
`Figure 12
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 12
`Exhibit 1018, Page 12
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 12 of 14
`
`US 2002111105692 A1
`
`{H}
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`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 13
`Exhibit 1018, Page 13
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 13 of 14
`
`US 2002211105692 A1
`
`Core Network
`
`201
`
`;
`
`Functional Model
`MetroTx to Core Rx
`
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`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 14
`Exhibit 1018, Page 14
`
`

`

`Patent Application Publication
`
`Aug. 8, 2002 Sheet 14 0f 14
`
`US 2(N]2{0105692 A1
`
`.2031
`
`309
`
`Figure 15
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 15
`Exhibit 1018, Page 15
`
`

`

`US 200210105692 A1
`
`Aug. 8, 2002
`
`HIERARCHICA]. WDM 1N 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 0]" THE. INVEN'HUN
`
`‘l‘raditionally enterprise voice and data networks in
`[0002]
`e.g. a metro area have developed around peer-peer oriented
`services, ring architectures and time division multiplexing
`(‘I‘DM‘J and time division switching ('l‘DS) technologies.
`
`Peer~peer oriented services requirements occurred
`[0003]
`since the tralfic that stayed within the metro area was much
`greater than the traffic which was destined for a remote
`metro area. 'I‘elephonc 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 TD!“ and TDS technologies could he easily
`integrated into low cost Very Large Scale Integrated {VLSU
`devices,
`this in the past enabled distributed access and
`switching between any channels on a TDM ring network
`(such as a SONETISDII ring). Such distributed access and
`switching technologies were well matched to the peer—peer
`service orientation, since iftwo 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 e.g. a [28x128 optical cross-
`connect switch in a 128 wavelength ring.
`SUMMARY OF THE INVENTION
`
`[0001'] Throughout the specification the following abhre~
`vialions will be used:
`
`“WUM: Hierarchical Wavelength Division
`[0008]
`Multiplexing
`
`(.‘WDM: Coarse Wavelength Division Multi-
`[0009]
`plexing
`
`])W[)M: Dense Wavelength Division Multi-
`[0010]
`plexing
`
`[0011] The present invention seeks to provide an alterna—
`tive optical ring network and a method of providing l-[WDM
`in a client-server architecture in an optical ring network
`which can provide a more flexible and cost eflective solu-
`tion.
`
`In accordance with a lirst aspect of the present
`[0012]
`invention there is provided an optical ring network cont-
`prising a plurality of network elements including a core
`network element interfacing the ring network with an exter-
`nal core network, and at least one ring network clement;
`wherein the core network element includes a lirst CWDM
`
`unit, a lirst DWDM unit and switching means arranged to
`cross connect an)’ 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
`addr'drop at least a first wavelength band at said ring network
`element from and to the second DWDM unit and to express
`other wavelength bands onto the next network element.
`
`[0013] Accordingly, the invention can provide an optical
`ring network with high scalability provided by the ability to
`scale to a larger number ol‘ wavelengths at an individual ring
`network element without impact upon other ring network
`elements by activating additional wavelengths within each
`(TWDM wavelength band. Additionally,
`it
`is possible to
`increase the number of rittg network elements through the
`addition ofCWI)M wavelength bands, again without impact
`upon the existing ring network elements.
`
`includes a
`the second DWDM unit
`[0014] Preferably,
`dense wavelength division demuItiplexing unit, a dense
`wachength division multiplexing unit and a connector
`means disposed therebeIWeen and arranged,
`in use,
`in a
`manner such that wavelength channels within said first
`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 first wave—
`length band are added.
`
`the connector means is further
`[0015] Advantageously,
`arranged in a manner such that, in use, it is reconfigurable to
`selectively express, drop, or add a particular wavelength
`channel within said first wavelength hand.
`[0016] The connector means may comprise 11 2x2 optical
`switches ora single 2n><2n optical switch, where n is the size
`of the dense wavelength demultiplcxer and multiplexer
`uniLs.
`
`in accordance with a second aspect of the present
`[0017]
`invention there is provided a ring network element for use in
`an optical ring network having a core network element
`interfacing the ring network with an external core network,
`the ring network element comprising a CWDM unit and a
`l)Wl)M unit. the (WDM unit being arranged to addfdrop at
`least a lirst wavelength hand at said ring network element
`from and to the DWDM unit and to express other wave-
`length bands onto the next network element.
`
`[0018] Preferably, the DWDM unit includes a dense wave-
`length division demultiplexing 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 first Wavelength hand are
`either dropped at the ring network element or expressed onto
`the next network element, and such that other wavelength
`channeLs within said first wavelength band are added.
`
`the connector means is further
`[0019] Advantageously,
`arranged in a manner such that, in use. it is reconfigurable to
`selectively express, drop. or add a particular wavelength
`channel within said first wavelength hand,
`
`[0020] The connector means may comprise n 2x2 optical
`switches or a single 2nx2n optical switch, where n is the sire
`of the dense wavelength demultiplexer and multiplexer
`units.
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 16
`Exhibit 1018, Page 16
`
`

`

`US 200210105692 A1
`
`Aug. 8, 2002
`
`In accordance with a third aspect of the present
`[0021]
`invention there is provided a method of providing l-IWDM
`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-l
`drop at least a first 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
`ot‘utilising DWDM techniques at the ring network elements
`to drop certain wavelength channels within said lirst wave-
`length band at the ring network element.
`to express other
`wavelength channels within said first wavelength band on to
`the next network element, and to add wavelength channels
`within said first wavelength hand 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.
`
`is a schematic drawing illustrating the
`I
`:0024] FIG.
`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. l.
`
`: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 tnelro 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 Configurations embody—
`ing the present invention.
`
`:0031] FIG. 8 IJWDM 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.
`
`[2 is a schematic drawing illustrating the
`:0035] FIG.
`logical connectivity of the metro ring of FIG. 11.
`
`[3 is a schematic drawing illustrating the
`[0036] FIG.
`logical connectivity of the metro ring of FIG. 11 in an
`alternative form.
`
`[4 is a schematic drawing illustrating the
`[0037] FIG.
`functional layers of switching. multiplexing and transmis—
`sion for a particular metro to core huh connection in the
`metro ring of FIG. 11, representative of a method of
`providing llWl)M 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. [4.
`
`DETAILED DESCRIPTION OF THE
`EMBODIMENTS
`
`In the preferred embodiment described an optical
`[0039]
`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. Ntditionally, 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 elemean.
`
`[0040] FIG. 1 show a schematic of an optical metro ring
`network 10 wherein each metro hub e.g. 12 includes a
`(‘WDM unit 14 and a DWDM unit 16. Each CWDM unit
`e.g. 14 is a band-pass filter that will drop e.g. 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 [or cross
`connecting any wavelength channel cg. 21 within or
`between wavelength bands eg. 20, 22 on the metro ring
`network 10 or, additionally, between the metro Ad ring
`network Ill and an external core network (not shown}.
`
`[0041] The system diselosed is scalable in two ways. First,
`the activation of wavelengths within each (.‘WIJM band
`enables the capacity of each individual metro hub to be
`increased without affecting other metro hubs. Second. the
`addition of further C'WDM 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 e.g. the bandwidth of the
`express filters.
`the total available wavelength range. and
`limitations on how closely wavelength channels may be
`spaced within each CWDM wavelength band.
`
`in FIG. 2 the metro ring network 10 (expanded to
`[0042]
`more metro hubs} is shown in a physical representation, and
`FIG. 3 shows it's logical connectivity. Each wavelength
`band cg. 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,
`c.g. 20, 22 is contained at the core hub 13. Switching at the
`metro hubs may he 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 e.g. 14 in the
`metro ring network 10 (FIGS.
`1
`to 4)). 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.
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 17
`Exhibit 1018, Page 17
`
`

`

`US 200210105692 A1
`
`DJ
`
`Aug. 8, 2002
`
`[0045] FIG. 6 is a block diagram that shows schematically
`the conliguration ol' the Line Interface Cards 416, Channel
`Switch 414 and Trunk Interface cards 412 in a metro hub
`configured 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 configu-
`ration oi" the Channel Switch 414. In the hub configuration
`shown in FIG. 6, the huh is capable of providing M:N
`channel protection,
`in which M+N 'l'runk 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 Linc Interface (.‘ards 416 to an
`unused Trunk Interface Card 412 by reconfiguring the
`Channel Switch 414.
`
`[0046] Each Trunk Interface (.‘ard 412 requires a suitable
`single—frequency DWIJM laser for transmission of the trunk
`signal into the network via the DWDM MUXJDEMUX Unit
`410, the (.‘WDM Unit 406, the Management MUXDEMUX
`Unit 402 and the Hub Bypass Switch 400. Depending upon
`factors such as, c.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
`distributch feedback (D1713) semiconductor laser. Alterna-
`tively the laser may he a more costly, higher—performance
`device, such as a DFB semiconductor laser incorporating an
`integrated external clectro—absorption modulator (DFB—EA),
`and active wavelength stabilisation.
`in order to achieve
`higher hit-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 1“1G. 14.
`
`[0047] Asshown in FIG. 6, each'I‘runk Interface Card 412
`is connected by a pair of fibres to the DWDM MUXJ'
`DEMUX Unit 410 (FIG. 5). Each fibre connecting a Trunk
`Interface (Tard 412 to the IJWIJM Unit 410 carries a single
`wavelength in one direction. Ilalf oflhese wavelengths will
`carry data transmitted from the hub and half will carry data
`to he received at
`the hub. An exemplary embodiment is
`described here, in which there are 16 full-duplex channels at
`each huh comprising 16 transmitted (‘l'x) wavelengths and
`16 received (Rx) wavelengths. Le. a total of 32 different
`wavelengths. However, it will be appreciated that a greater
`or smaller number ot‘ channels could be accommodated
`witltout depanure from the scope of the present invention.
`The DW1)M Unit 410 receives the 16 '1‘): channels from the
`Trunk Interface Cards 412 and multiplexes them onto a
`single fibre. It also receives the 16 Rx channels on a single
`fibre from the (‘WDM Unit 406 and dcmultiplexes them to
`the 16 Rx fibres 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 configuration, M:N channel
`protection is supported, where anb for the exemplary
`embodiment. and M is the number of additional Trunk
`Interface Cards 412 provided.
`
`[0049] Turning now to FIGS. 7A and 73, which show
`schematically two exemplary embodiments of tlte l)WI)M
`MUXIDEMUX Unit 410. In the first exemplary embodi-
`ment, FIG. TA, the DWDM MUXJDEMUX Unit 410 com‘
`prises internally separate optical multiplexing means 606
`
`and demultiplexing means 608, and comprises externally a
`unidirectional
`input fibre 601} and a unidirectional output
`fibre 602. In the second excmplary embodiment, FIG. TB,
`the DWDM MUXJ‘DEMUX Unit 410 comprises internally a
`single optical multiplexing and demulliplexing means 610,
`and comprises externally a single bi-directional input/output
`libre 604 in either embodiment the optical multiplexing and
`demultiplexing means may be, cg. a free-space diffraction
`grating based device, or a planar liglttwave circuit based
`device such as an arrayed waveguide grating.
`It will be
`appreciated that other embodiments of the DWDM MUX-t'
`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
`rl‘x and Rx channels to specific wavelengths for transmission
`on one or more fibres in the optical ring network. FIGS. 8A
`and 3B show schematically two exemplary embodiments of
`a DWDM Wavelength Map in which there are eight Rx
`channels, 7020—6 and 706n—i'r, and eight Tx channcls, 7040—6
`and 708n—h. ll will he appreciated that different numbers of
`'l'x and Rx chanttets. 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
`relcrrcd to as a non-interleaved wavelcngth map, because
`the Rx wavelengths '.I"l]2(.'-.t’.I occupy a wavelength band that
`is disjoint from the wavelength hand occupied by the Tar
`wavelengths 704mb. the exemplary embodiment shown in
`FIG. 8B is referred to as an interleaved wavelength map,
`because the Rx wavelengths 7060-1: alternate with the Tx
`wavelengths 708(1—6 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 invenlion.
`[0052] A non—interleaved wavelength map may he used to
`simplify network operation and management, and relax
`tolerances on components to reduce costs, by grouping Rx
`wavelengths 702ml: and '1‘): wavelengths 704ml: so that they
`may easily be separated from each other, e.g for routing or
`amplification, by simply using a coarse optical
`filter. An
`interleaved wavelength map may be used to enable Rx
`wavelengths 706ml! and '1'): wavelengths 708ml: in a single
`fibre 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, e.g. at
`filters 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 (e.g. fill (it [7,), whereas
`the spacing between adjacent cou nterpropagating channels
`is reduced to half this value (cg. 25 GHZ), effectively
`doubling the capacity of the fibre.
`[0053] mlvanlageously,
`interleaved and nonminlcrleavcd
`wavelength tnapping techniques may be employed in a
`single network in order to obtain the benefits of simplified
`operation and management. reduced costs, higher capacity.
`or a trade-off amongst these, as required.
`[0054] The CWTJM Unit 406 addsr'drops the appropriate
`wavelength blocks for the hub and passes all other express
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 18
`Exhibit 1018, Page 18
`
`

`

`US 200210105692 A1
`
`Aug. 8, 2002
`
`trafllc 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 fibre connections 800m
`8005 to the optical fibre ring via the Hub Bypass Switch 400
`(FIG. 5). These two trunk fibres 800a, 8004‘) correspond to
`the two directions around the ring. Note that signals propa-
`gate bi-direL1ionaIly on each of these fibres 800a. 801"). 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 configuration. only one transmission
`libre 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 fibre con-
`nections.
`
`[0055] The (TWIJM Unit 406 also has two fibre connec-
`tions 802a. 802th to the DWDM MUXJDEMUX 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 libre connections 800a,
`8005 and transfer them to the hub via the fibre connections
`802a, 802.5. A second function of the CWDM Unit 406 is to
`accept blocks of wavelengths transmitted by the hub via the
`fibre connections 802a. 8021; and multiplex them onto the
`trunk fibre connections 800a, 8013!). A third function of the
`CWDM Unit 406 is to pass all trunk wavelengths received
`on the trunk fibre connections 500a, 8001') which are not
`demultiplexed at the ltub across to the opposite trunk fibre
`connection 8001). 800a via tlte Express 'l‘raflic path 804.
`Advantageously, the C'WDM Unit 406 should provide high
`isolation, i.c. signals destined for the hub traffic [ibrcs 802a.
`802th should not appear in the Express 'l‘raflic path 804 and
`vice versa. and should have low insertion loss. i.c. ring trallic
`passing between the trunk fibres 300a, 1300!: via the Express
`Traffic 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 lland Allocation schemes are now dis-
`closed. These exemplary schemes are based on using the
`conventional transmission band. referred to as "C-llartd".
`which spans the wavelength range from around 1530 nm to
`1560 nm, or additionally using the long-wavelength trans-
`mission band, referred to as "I.-I-land“, which spans the
`wavelength range from around |580 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 assu med that each hub comprises 16 Trunk Interface
`Cards 4I2 (FIG. 5) and 16 Line Interface Cards 416 (FIG.
`2}, and thus requires l6 '1‘): wavelengths and 16 Rx wave—
`lengths. II will be appreciated that other transmission bands,
`alternative wavelength spacings, and hubs with difierent
`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 (TWDM Band Allocation determines the num-
`ber of hubs that can transmit and receive on a single libre
`ring. The options available include:
`using C—Band;
`[0053]
`using C+I _~I'Iand.s:
`[0059]
`using a single continuous wavelength band
`[0060]
`comprising both T): wavelengths and Rx wave-
`lengths;
`
`using separate wavelength bands comprising
`[0061]
`Tx wavelengths and Rx wavelengths;
`
`ll’ C-Band only is used then two hubs may be
`[0062]
`accommodated on a single libre. 1f C+I .—Ilands are used then
`four hubs may be accommodated on a single libre.
`If
`additional hubs are required. then litrther 'l'x and Rx chan-
`nels can be provided using the same wavelengths within the
`(‘- and 1,-bands transmitted on additional fibres. It will be
`appreciated that. although in the example presented here I6
`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'l'x and Rx channels per hub. and the number
`of fibres required.
`
`[0063] FIGS. 10A-C illustrates schematically three exem-
`plary allocation schemes based on the use of (i+[,—llands to
`support four hubs. In FIG. 1011 each hub is allocated a
`single continuous wavelength band 90tlrr~d comprising both
`T): wavelengths and Rx wavelengths. Within each C'WDM
`Band 900rr-d the shorter wavelengths are allocated to Rx
`channels 902n-d and the longer wavelengths are allocated to
`TX channels 904041. The (TWIJM [lands Willa—d are sepa-
`rated by Guard Bands 906rr-c which allow for the linite
`roll-off rate at
`the edges of the CWDM Band litters to
`minimise crosstalk between bands.
`
`In FIG. 1013 each hub is allocated a wavelength
`[0064]
`band 908n-d within the C-Band for Rx wavelengths and a
`wavelength band 910a-(t‘ within the L-Band for Tx wave-
`lengths. 'Ihe [WDM Bands 908a-d. 910n-ri are separated by
`Guard Bands 912mg which allow for the finite roll-off rate
`at the edgesofthc CWIJM Band filters to minimise crosstalk
`between bands.
`
`In FIG. 10C each hub is allocated two separate
`[0065]
`wavelength bands within either the C-lland or L-Band for
`T): wavelengths and Rx wavelengths. Huh I and lluh 2 are
`allocated one band each 914m 914!) within the C—Band for
`Rx wavelengths. and another band 9161?. 916?) within the
`C-Band for T3: wavelengths. Hub 3 and Hub 4 are allocated
`one hand each 918a, 9181‘) within the L-Band for For
`wavelengths, and another band 9200. 920i: within the
`L-Band for Tx wavelengths. The CWDM Bands 914d. 914b,
`9160. 916b, 918a. 9183:. 9200. 92033 are separated by Guard
`Bands 922mg which allow for the finite roll-off rate at the
`edges of the (TWOM lland filters 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
`libres.
`
`[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 Irathc.
`
`In FIG. 11, the addition of a reconfigurable optical
`[0068]
`addrdrop multiplexer (ROADM) to a metro ring network
`201 configuration in another preferred embodiment is shown
`in a logical configuration. In place of a terminal DWDM unit
`at the metro hubs cg. 209 (compare FIG. I), there are two
`such ntuxr’demux units 202. 210. connected by a connector
`unit 211. This enables a wavelength channel within a par-
`ticular band to he expressed on to the next node using this
`band. This therefore aIIoWs more than one node to use the
`same CWDM band,
`in FIG. 11 hubs 209 and 213. This
`
`JDS UNIPHASE CORPORATION
`JDS UNIPHASE CORPORATION
`Exhibit 1018, Page 19
`Exhibit 1018, Page 19
`
`

`

`US 200210105692 A1
`
`Aug. 8, 2002
`
`enables the llWDM system to be much more flexible and
`scalable.
`In conjunction with low—cost optical addidrop
`multiplexers used where only a single duplex channel
`is
`required to be dropped then a system tltat meets the com-
`bined need for low-up front cost and llexible 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 hands 224. 226,
`with no other metro hub using those same respective bands
`224, 226. Furthermore, the metro ring ne