Method of deactivating working fiber resources in optical ring networks
Contents
1. 2 networks or continental networks where traffic is largely concentrated on East West spans and little if any traffic is transmitted along North South spans In these networks the fiber capacity on North South spans is not efficiently utilized and in many instances may not be needed for traffic carrying purposes In addition to this ineffective use of fibers the accommo dation of multiple fibers between nodes necessitates at each node the installation of connection equipment for each fiber However duplicating this equipment for each fiber may also prove to have a considerable impact on the system cost particularly on spans where the fiber capacity is underuti lized Therefore it would be desirable to use the existing working fiber capacity more efficiently in optical ring net works or alternatively deactivate underutilized fibers and associated equipment so that they can be removed or re provisioned for use in other network configurations SUMMARY OF THE INVENTION The present invention provides a method of deactivating working fiber resources in an existing optical ring network or system for a cost effective and efficient allocation of the fiber resources available in the ring network The invention can be applied to deactivate physical working fibers as well as working channels or wavelengths provisioned on a physi cal working fiber The term fiber is therefore used to denote both a physical fiber and a channel or wavelength pr2. rected around the network 10 access to the protection fiber 134 is locked out and the DCW traffic is manually switched on the protection fiber 134 As a result the working fiber 136 can be removed or re provisioned According to the invention the LWO U mode should preferably be defined to automatically disable any alarm activated when optics equipment is removed or re provisioned For example the LWO U mode should be defined to automati cally disable circuit pack missing alarms which may be activated when the working fiber 136 or its connecting equipment is removed While the invention has been described above with ref erence to a particular network topology further modifica tions and improvements to support other network configu rations which will occur to those skilled in the art may be made within the purview of the appended claims without departing from the scope of the invention in its broader aspect In the first embodiment the invention has been described above in relation to a BLSR network configuration formed of a series of interworking rings It is understood that for this particular embodiment the invention could alternatively be used in relation to BLSR network configurations with dif ferent ring arrangements For example the invention could apply to a BLSR network configuration which consists of a single ring In this case the nodes forming the BLSR network would not need to provide matched node support With
3. adjacent ring 104 and the sec ondary node 114 Outbound traffic directed from ring 104 to ring 102 is similarly transmitted using the same DCW routing and path selection technique For clarity the manner in which this is performed will now be described only in relation to traffic going from ring 102 to 104 The outbound traffic going from ring 102 to 104 is transmitted as a primary transmission from the primary node 118 via tributary connections to the primary node 126 of the ring 104 In addition the outbound traffic is also dropped on the working fiber 136 for transmission to the associated secondary gateway node 114 From the secondary node 114 the outbound traffic is then passed across tributary connec tions to the node 120 and subsequently forwarded therefrom as a secondary transmission to node 126 via the working fiber 178 At node 126 a service selector not shown bridges the primary transmission through If a failure occurs interrupting or corrupting the primary transmission the selector can alternatively bridge the secondary transmission through to complete the outbound transmission As is well known the provisioning of primary and sec ondary nodes in the rings 102 104 is not unique In the network 100 a node provisioned as a primary node such as the nodes 118 126 for a particular outbound transmission may also be provisioned as a secondary node for other outbound transmissions In the same fashion a node provi s
4. also applies to the deactivation of underutilized working fibers and equip ment in the East West fiber spans 50 52 54 and 56 FIG 2 illustrates as an example the network 10 of FIG 1 where the working fibers 86 88 of span 62 and 63 the working fiber 90 of span 64 and their respective connecting equipment not shown have been deactivated and removed Despite removing the working fibers 86 88 and 90 however the spans 62 64 are still equipped with the protection fibers 74 76 78 80 and can still provide full ring protection if necessary According to the invention other North South working fiber deactivation scenarios to improve bandwidth efficiency and contain costs in the network 10 are possible For example the working fiber 92 present in the North South span 65 could also be deactivated Similarly the working fiber 82 present on the North South span 60 could also be deactivated Generally the working fiber capacity present in the North South spans 60 61 62 63 64 and 65 can all be completely deactivated if underutilized For the purpose of example the following description is restricted to the deac tivation of the working fiber 86 in the North South span 62 However it is understood that this description also applies to the deactivation of any other working fiber in any span on this ring network 10 In order to deactivate the working fiber 86 and associated connecting equipment the working traffic scheduled at nodes 14 2
5. respect to the second embodiment it is to be understood that on spans where working fibers are to be removed the invention is not restricted to maintaining working connections for DCW traffic across these spans There may be situations where it is desirable to maintain different connections for different traffic It is understood 10 15 20 25 30 35 40 45 50 55 60 65 10 that the invention as described in this particular embodiment could also apply to these situations For example the invention could also be used to maintain a protection con nection for drop and continue on protection DCP traffic which could be present on spans where working fibers are to be removed In this particular example the span and ring traffic would still be rerouted around the network and the span and ring lockouts described above would still be required to prevent the working fiber to be deactivated from being protected However the persistent manual switch described above as directing DCW traffic onto a protection fiber would not be required as the DCP is already routed onto the protection fiber We claim 1 A method of deactivating a first fiber interconnecting first node and a second node in an optical ring network where the first interconnecting fiber defines a working path for traffic between the first and second nodes and where a second interconnecting fiber defines a protection path for protecting traffic between t
6. scheduled for trans mission on the first interconnecting fiber to another working path defined in the optical ring network between the first and second nodes routing a second portion of the traffic scheduled for transmission on the first interconnecting fiber to the protection path defined between the first and second nodes by the second interconnecting fiber locking out access to the second interconnecting fiber to prevent the first interconnecting fiber from being pro tected by the second interconnecting fiber deactivating the first interconnecting fiber 18 The method of claim 17 wherein the first portion of the traffic scheduled consists of span and ring traffic and wherein the second portion of the traffic scheduled for transmission on the first interconnecting fiber consists of drop and con tinue on working DCW traffic 19 The method of claim 17 wherein the first portion of the traffic scheduled consists of span and ring traffic and wherein the second portion of the traffic scheduled for transmission on the first interconnecting fiber consists of drop and con tinue on protection DCP traffic 20 The method of claim 17 wherein locking out access to the second interconnecting fiber to prevent the first inter 5 10 15 20 25 30 35 40 45 50 55 60 65 12 connecting fiber from being protected by the second inter connecting fiber comprises applying a lockout of working span on the secon
7. 0 to be transmitted on the North South span 62 is rerouted away from the under utilized working fiber 86 In addition access to the protection fiber 74 is locked out to prevent the span 62 from completing any switch to the protection fiber 74 as the working fiber 86 or connecting equipment is deactivated To re route traffic away and lock out access to the working fiber 86 a new INM mode hereinafter referred to as the working optics removed WOR mode is defined and applied at each node 14 20 terminating the working fiber 86 to be deactivated When operating in this mode the nodes 14 20 redirect working traffic away from the North South fiber span 62 More specifically when the WOR mode is enabled the traffic scheduled to transmit on the working fiber 86 and terminating at nodes 14 20 referred to as span traffic or passing through the nodes 14 20 referred to as ring traffic is instead rerouted around the network 10 for transmission on one or more alternate paths interconnecting the nodes 14 20 For example the span and ring traffic originally sched uled at node 14 to be transmitted to node 20 via the fiber 86 could instead be rerouted through the nodes 12 and 18 via the working fibers 30 84 and 42 The manner in which span and ring traffic can be rerouted between the nodes 14 and 20 on paths other than the fiber 86 would be obvious to a person skilled in the art and is not described here in any detail In addition to re routing tr
8. 19 YJg14 93810 19 US 6 529 298 B1 Sheet 2 of 4 Mar 4 2003 U S Patent S Old J M LL el 9NIY 51 1899 N USIA ONOAS Oy oe YHOMLIN i ysig zz 02 gi g 3815 931044 93 0 y 53915 ININYOM TWNOILIIYIC 18 US 6 529 298 B1 Sheet 3 of 4 Mar 4 2003 U S Patent Ol 001 YHOM LIN ysig 9300 AYMILY9 pol INIY YILNI AYYNIHd 9519 ONOJJS SNOLLIANNOD SIOON AYMILVS 93 1 5 cOL 5519 15913 3813 931094 19 0119391 19 938915 ONDIYOM 934178 US 6 529 298 B1 Sheet 4 of 4 Mar 4 2003 U S Patent 5 001 J M YHOMIAN ysa N 01 201 18 ONODIS ONIY 1 189 44dld 112410 4 43814 A TYNOILJJY10 18 US 6 529 298 B1 1 METHOD OF DEACTIVATING WORKING FIBER RESOURCES IN OPTICAL RING NETWORKS FIELD OF THE INVENTION This invention relates generally to optical ring networks and more particularly to a method of deactivating working fiber resources in optical ring networks BACKGROUND ART Today s optical transport networks employ a number of different topologies to satisfy increasing demands for net work simplicit
9. R network 100 is also formed of a series of interconnected BLSR rings FIG 3 only shows two complete BLSR rings 102 104 and for the purpose of example only these two rings 102 104 will now be described The first ring 102 is formed of a plurality of nodes 112 114 116 118 only four shown interconnected with bidi rectional East West fiber spans 150 154 and North South fiber spans 152 156 157 The East West fiber spans 150 154 each consists of a working fiber 130 140 full line and a protection fiber 132 138 dotted line The span 150 interconnects node 112 with node 114 while the span 154 interconnects node 116 with node 118 Similarly to the spans 150 154 the North South fiber spans 152 156 157 each consists of a working fiber 136 144 146 full line and a protection fiber 134 142 148 dotted line The span 152 interconnects node 114 with node 118 while the spans 156 157 interconnect node 112 with 116 Between these nodes US 6 529 298 B1 7 112 116 the span 157 provides North South connectivity for traffic circulating in ring 102 while the span 156 provides connectivity for traffic circulating in an adjacent ring not shown Similarly the second ring 104 is formed of a plurality nodes 120 122 124 126 only four shown interconnected with bidirectional East West spans 180 184 and North South spans 182 186 187 The East West spans 180 184 each consists of a working fiber 162 174 full line and a prot
10. The method of claim 33 wherein the BLSR network consists of multiple interconnected optical rings 35 The method of claim 33 wherein the BLSR network consists of a single optical ring 36 A method of routing traffic between a first and a second node in an optical network where the first and second US 6 529 298 B1 13 nodes are interconnected with a first and second fiber each defining a respective working path and a protection path the optical network being formed of a plurality of nodes inter connected with at least one fiber which define multiple working paths and protection paths in the optical network the method comprising at each of the first and second nodes scheduling traffic for transmission to the corresponding one of the first and second nodes routing the traffic scheduled from the first node to the second node via the first interconnecting fiber 14 if the first interconnecting fiber is to be removed re routing the traffic scheduled via another working path defined in the optical network between the first and second nodes and locking access to the second interconnecting fiber at the first and second nodes to prevent the first interconnect ing fiber from being protected by the second intercon necting fiber UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT 6 529 298 Page of 1 DATED March 4 2003 INVENTOR S Peter W Phelps et al It is certified that error appea
11. a United States Patent Phelps et al US006529298B1 10 Patent No 45 Date of Patent US 6 529 298 1 Mar 4 2003 54 75 73 21 22 51 52 58 56 METHOD OF DEACTIVATING WORKING FIBER RESOURCES IN OPTICAL RING NETWORKS Inventors Assignee Notice Appl No Filed Int US Field of Search Peter W Phelps Nepean CA Evert E Deboer Nepean CA Robert Caporuscio Montreal CA Johnny Leung Kirkland CA Paul Charron St Lambert CA Louis R Pare St Bruno CA Joseph Olajubu Essex GB Nortel Networks Limited St Laurent CA Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 0 days 09 471 138 Dec 23 1999 H04B 10 08 359 110 359 119 359 110 119 359 173 References Cited U S PATENT DOCUMENTS 5 717 796 BI DIRECTIONA WORKING FIBE 2 1998 Clendening 359 119 lt FIRST BLSR RING 5 903 370 A 5 1999 Johnson 359 119 6 046 832 A 4 2000 Fishman 359 119 6 052 210 4 2000 Nathan 359 119 6 222 653 4 2001 Asahi 359 110 6 295 146 9 2001 Nathan etal 359 119 cited by examiner Primary Examiner Kinfe Michael Negash 57 ABSTRACT The present invention provides a method of deactivating working fibers in an existing optical ring network or sy
12. affic the nodes 14 20 also each lock out access to the protection fiber 74 For this two lockouts are applied at each node 14 20 a lockout of 10 15 20 25 30 35 40 45 50 55 60 65 6 working span and a lockout of working ring Despite the absence of any traffic on the working fiber 86 because of the re routing these lockouts are necessary to prevent the fiber span 62 from completing a span or ring switch to the protection fiber 74 when the working fiber 86 or connecting equipment is deactivated However these lockouts will not preempt ring protection switches in force on the span 62 and as such the protection fiber 74 can still provide full ring protection capabilities to traffic elsewhere on the ring 11 when necessary By enabling the WOR mode in the nodes 14 20 traffic to transmit on the working fiber 86 is rerouted around the network 10 on alternate paths and access to the protection fiber 74 is locked out so that the working fiber 86 and associated equipment can be deactivated Once deactivated the fiber 86 can then be disconnected and can be removed or re provisioned Similarly the connecting equipment associ ated with the fiber 86 which typically includes circuit packs can be also be removed or re provisioned for use in alter native network configurations According to the invention the WOR mode should pref erably be defined to automatically disable any alarm acti vated in relati
13. ber spans 60 61 Between these nodes 12 18 the span 61 provides North South connectivity for traffic circulating in ring 11 while the span 60 provides connectivity for traffic circulating in an adjacent ring not shown Similarly node 14 is intercon nected with node 20 via a second pair of North South fiber spans 62 63 and node 16 is interconnected with node 22 with a third pair of North South fiber spans 64 65 where each span provides North South connectivity for a particular ring Each North South fiber span 60 61 62 63 64 and 65 consists of a working fiber 82 84 86 88 90 92 full line and a protection fiber 70 72 74 76 78 80 dotted line In the BLSR network 10 the bidirectional working and protections fibers described above with respect to the East West fiber spans 50 52 54 56 and the North South fiber spans 60 61 62 63 64 65 each consists of a pair of unidirectional physical fibers or channels Therefore on each span 50 52 54 56 60 61 62 63 64 65 four unidirectional physical fibers or channels are used It is to be understood that this is merely an example If necessary the BLSR network 10 could be designed with a different con figuration to meet different capacity demands For example the BLSR network could be designed with additional physi 10 15 20 25 40 45 50 55 60 65 4 cal fibers or wavelengths on each span 50 52 54 56 60 61 62 63 64 65 to meet highe
14. d inter connecting fiber to prevent the first interconnecting fiber from being protected by a span switch and applying a lockout of working ring to prevent the first interconnecting fiber from being protected by a ring switch 21 The method of claim 20 wherein routing a second portion of the traffic scheduled for transmission on the first interconnecting fiber to the protection path defined between the first and second nodes by the second interconnecting fiber comprises applying a manual switch to direct the DCW traffic scheduled for transmission on the first interconnecting fiber to the second interconnecting fiber 22 The method of claim 21 wherein the DCW traffic scheduled for transmission on the first interconnecting fiber is directed to the second interconnecting fiber when the second interconnecting fiber is not used in a ring protection request 23 The method of claim 18 wherein locking out access to the second interconnecting fiber to prevent the first inter connecting fiber from being protected by the second inter connecting fiber is done when no protection switch is in effect in the optical ring network 24 The method of claim 18 wherein locking out access to the second interconnecting fiber to prevent the first inter connecting fiber from being protected by the second inter connecting fiber is done when the first interconnecting fiber does not carry any span or ring traffic 25 The method of claim 17 further comprising r
15. ection fiber 160 172 dotted line The span 180 inter connects node 120 with node 122 while the span 184 interconnects node 126 with node 124 Similarly to the spans 180 184 the North South fiber spans 182 186 187 each consists of a working fiber 178 170 168 full line and a protection fiber 176 164 166 dotted line The span 182 interconnects node 120 with node 126 while the spans 170 and 168 interconnect node 122 with node 124 Similarly to the spans 156 157 interconnecting node 112 with node 116 in the first ring 102 the span 186 provides North South connectivity for traffic circulating in ring 104 while the span 187 provides connectivity for traffic circulating in an adja cent ring not shown In the network 100 the rings 102 104 are interconnected via tributary connections established between node 114 and node 120 and between node 118 and node 126 Each of these nodes 114 118 120 126 has a plurality of tributary inter faces able to support interconnections with an adjacent ring These interconnections provide the necessary support for inter ring traffic In order to protect inter ring traffic the nodes 118 and 126 are configured as primary inter ring gateway nodes and the nodes 114 120 are provisioned as secondary inter ring gateway nodes For outbound traffic going from ring 102 to ring 104 DCW routing is employed within the primary gateway node 118 in ring 102 to pass the exiting traffic simultaneously to both the
16. emoving the first interconnecting fiber 26 The method of claim 17 further comprising provi sioning the first interconnecting fiber for use in another optical network 27 The method of claim 17 wherein the first and second nodes are each connected to the first interconnecting fiber with respective fiber connecting equipment the method further comprising deactivating at each of the first and second nodes the corresponding fiber connecting equipment 28 The method of claim 27 further comprising removing at each of the first and second nodes the corresponding fiber connecting equipment 29 The method of claim 28 further comprising disabling at each of the first and second nodes fiber connecting equipment missing alarms associated with the correspond ing fiber connecting equipment 30 The method of claim 28 wherein the fiber connecting equipment at each of the first and second nodes comprises line circuit packs 31 The method of claim 27 further comprising provi sioning at each of the first and second nodes the correspond ing fiber connecting equipment for use in another optical network 32 The method of claim 21 wherein locking access to the first interconnecting fiber and applying a manual switch to direct the DCW traffic scheduled to the second intercon necting fiber is done with a network management tool 33 The method of claim 17 wherein the optical ring network is a bidirectional line switched ring BLSR net work 34
17. he first and second nodes the optical ring network being formed of a plurality of nodes interconnected with multiple fibers which define multiple working paths and protection paths the method comprising at each of the first and second nodes routing the traffic scheduled for transmission on the first interconnecting fiber via another working path defined in the optical network between the first and second nodes locking out access to the second fiber interconnecting the first and second node to prevent the first interconnect ing fiber from being protected by the second intercon necting fiber and deactivating the first interconnecting fiber 2 The method of claim 1 wherein locking out access to the second fiber interconnecting the first and second node to prevent the first interconnecting fiber from being protected by the second interconnecting fiber comprises applying a lockout of working span on the second inter connecting fiber to prevent the first interconnecting fiber from being protected by a span switch and applying a lockout of working ring to prevent the first interconnecting fiber from being protected by a ring switch 3 The method of claim 1 wherein locking out access to the second fiber interconnecting the first and second node to prevent the first interconnecting fiber from being protected by the second interconnecting fiber does not preempt ring protection switches in the optical ring network 4 The method of c
18. ic around the network 100 on alternate paths On the North South spans 152 182 the working fibers 136 178 present normally carry DCW traffic between the primary nodes 118 126 and the secondary nodes 114 120 However with the exception of DCW traffic these fibers 136 178 are typically underutilized or unused According to another embodiment of the invention these fibers 136 178 can also be deactivated from the spans 152 182 FIG 4 illustrates as an example the network 100 of FIG 3 where the working fibers 136 178 normally responsible for DCW traffic on the North South spans 152 182 have been deactivated and removed The method by which the fiber 178 is deactivated is identical to the manner in which the fiber 136 is deactivated and will now be described below only in relation to the deactivation of the fiber 136 However it is to be understood that the following descrip tion also applies to the deactivation of the fiber 178 In order to deactivate the working fiber 136 traffic other than DCW traffic is redirected away from the fiber 136 In addition a channel connection is provisioned on the pro tection fiber 134 by means of a persistent user manual protection switch to place the DCW on the protection fiber 134 and maintain the necessary DCW traffic connectivity across the span 152 For this a new INM mode hereinafter referred to as the lockout of working unequipped LWO U mode is defined and applied at each node 114 118 ter
19. in at each of the first and second nodes the corresponding fiber connecting equipment comprises line circuit packs 12 The method of claim 9 further comprising provision ing at each of the first and second nodes the corresponding fiber connecting equipment for use in another optical net work 13 The method of claim 1 wherein locking out access to the second fiber interconnecting the first and second node to prevent the first interconnecting fiber from being protected by the second interconnecting fiber is done with a network management tool 14 The method of claim 1 wherein the optical ring network is a bidirectional line switched ring BLSR net work 15 The method of claim 14 wherein the BLSR network consists of multiple interconnected optical rings 16 The method of claim 14 wherein the BLSR network consists of a single optical ring 17 A method of deactivating a first fiber interconnecting a first node and a second node in an optical ring network where the first interconnecting fiber defines a working path for traffic between the first and second nodes and where a second interconnecting fiber defines a protection path for protecting traffic between the first and second nodes the optical ring network being formed of a plurality of nodes interconnected with multiple fibers which define multiple working paths and protection paths the method comprising at each of the first and second nodes routing a first portion of the traffic
20. ioned as a secondary node may also be provisioned as a primary node Further a primary node on one ring may feed either a primary or secondary node on an adjacent ring This is also true of secondary nodes More specifically a sec ondary node on one ring may forward its transmissions to 10 15 20 25 30 35 40 45 50 55 60 65 8 either a primary or secondary node on an adjacent ring For the purpose of example however it is hereinafter assumed that the nodes 114 118 120 126 are connected as shown in FIG 3 and that only the nodes 118 and 126 are configured as primary nodes while only the nodes 114 120 are config ured as secondary nodes As in most ring configurations traffic in the network 100 is typically concentrated on the East West fiber spans 150 154 180 184 With the exception of DCW traffic on the spans 152 182 the North South spans 152 156 157 182 186 187 may have little or no traffic According to the invention it is also possible to improve bandwidth efficiency on the North South spans 156 157 186 187 and also on the spans 152 182 despite the presence of DCW traffic by deactivating working fibers which are normally underuti lized or unused On the North South spans 156 157 186 187 there is no DCW traffic and the working fibers 144 146 170 can be deactivated as previously described i e by enabling a WOR mode at each terminating node 112 116 122 124 and rerouting traff
21. laim 1 wherein locking out access to the second fiber interconnecting the first and second node to prevent the first interconnecting fiber from being protected by the second interconnecting fiber is done when no pro tection switches is in effect in the optical ring network 5 The method of claim 1 wherein locking out access to the second fiber interconnecting the first and second node to prevent the first interconnecting fiber from being protected by the second interconnecting fiber is done when the first interconnecting fiber does not carry any span or ring traffic 6 The method of claim 1 further comprising removing the first interconnecting fiber 7 The method of claim 1 further comprising provisioning the first interconnecting fiber for use in another optical network 8 The method of claim 1 wherein the first and second nodes are each connected to the first interconnecting fiber with respective fiber connecting equipment the method US 6 529 298 B1 11 further comprising deactivating at each of the first and second nodes the corresponding fiber connecting equipment 9 The method of claim 8 further comprising removing at each of the first and second nodes the corresponding fiber connecting equipment 10 The method of claim 9 further comprising disabling at each of the first and second nodes fiber connecting equip ment missing alarms associated with the corresponding fiber connecting equipment 11 The method of claim 9 where
22. minating the fiber 136 to be removed When operating in this mode the nodes 114 118 are provisioned to direct traffic away from the fiber 136 and around the ring 102 More specifically when the LWO U mode is activated the span and ring traffic other than DWC traffic is routed around the ring 102 on alternate paths interconnecting the nodes 114 118 The manner in which this particular traffic is routed around the network 100 on alternate paths would also be obvious to a person skilled in the art and is not described here In addition the nodes 114 118 each locks out access to the protection fiber 134 on the span 152 with a lockout of working span and a lockout of working ring According to the invention these span and ring lockouts respectively prevent the fiber span 152 from completing a span and ring switch of the span and ring traffic other than DCW traffic to the protection fiber 134 when the working fiber 136 or connecting equipment is deactivated and causes a signal fail or signal degrade condition on the span 152 These lockouts will not however preempt ring protection switches in force US 6 529 298 B1 9 on the span 152 and as such the protection fiber 134 can still provide full ring protection capabilities to traffic elsewhere on the ring 102 when necessary With respect to the DWC traffic the nodes 114 118 provision a channel connection on the protection fiber 134 to maintain the necessary DCW traffic connectivity acro
23. n FIG 3 is a diagram of a conventional four fiber matched node BLSR network featuring a plurality of working fibers and FIG 4 is a diagram of the four fiber matched node BLSR network of FIG 3 with a reduced plurality of working fibers according to another preferred embodiment of the invention DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a method of deactivating working fiber resources in an existing optical ring network US 6 529 298 B1 3 or system for a cost effective and efficient allocation of the fiber resources available in the ring network The invention applies to the deactivation of physical working fibers as well as working channels or wavelengths For clarity and generality the term fiber as used in the description of the preferred embodiments provided below denotes a physical fiber or a channel wavelength provisioned on a physical fiber The invention can be used in any optical network or system for optimizing the use of fiber equipment and con nections available on spans where traffic is low or non existent According to the invention the traffic present on underutilized fibers is re routed making these fibers unused and unnecessary for traffic carrying purposes The unused working fibers and associated equipment are then de activated and can be removed or alternatively re provisioned for use in other network configurations In a preferred embodiment the invention is
24. ning these underutilized fibers and terminating equipment may not be justified To obtain better bandwidth efficiency and contain costs it is possible to deactivate underutilized working fibers and associated connecting optics equipment present therein According to the invention the deactivated fibers and asso ciated equipment can be then removed or alternatively re provisioned for use in other network configurations For example if there is little or no traffic on the North South spans 60 61 62 63 64 65 it is possible to remove some or all of the working fibers 82 84 86 88 90 92 with their respective optics equipment Alternatively it is possible to maintain and re provision underutilized working fibers and equipment for use in other network configurations Re provisioning underutilized fibers and associated equip US 6 529 298 B1 5 ment would maximize the full capacity of the equipment bay by not leaving any slots vacant therein which could other wise be used for other purposes in the same or other network configurations According to the invention it is also possible to deactivate underutilized working fibers and equipment that may be present in the East West fiber spans 50 52 54 56 For the purpose of example the following description is restricted to the deactivation of North South working fibers 82 84 86 88 90 92 in the North South spans 60 61 62 63 64 65 It is understood however that this description
25. o reduce service failures In conven tional unidirectional and bidirectional ring systems for example multiple fibers are commonly installed to achieve transmit and receive operations Additional fibers are also installed to protect the working fibers in the event of a link span failure Current ring protection schemes include dedi cated protection 1 protection fiber for each fiber or 1 1 protection which can be used in both path switched and line switched configurations In optical ring networks some spans that interconnect nodes are not required to carry working traffic This is either because there is no requirement for traffic or because there is too much capacity available and it cannot all be efficiently used This is particularly true for dense wavelength division multiplex DWDM systems where the number of channels or wavelengths available on some spans can very well exceed the transport capacity required Currently all spans separating adjacent nodes in a ring configuration have to be fiber equipped because of the protection usage that is necessary on a ring configuration However this requirement only makes use of protection fibers On spans where traffic is low or non existent the working fibers present may never be used As a result the fiber capacity available in some optical ring networks may be underutilized This is particularly true for long distance 10 15 20 25 30 40 45 50 55 60 65
26. on to missing equipment For example the WOR mode should be defined to automatically disable circuit pack missing alarms which may be activated when the fiber connecting equipment is removed Further in the preferred embodiment it should not be possible to activate the WOR mode when working channel connections are provisioned across the fiber span 62 In the preferred embodiment of the invention described above working channel connections cannot be provisioned on the fiber span 62 while the WOR mode is in effect This is because when the WOR mode is enabled the nodes 14 20 prevent access to the underutilized fiber 86 so that as noted above the fiber 86 can be deactivated However by pre venting access to the fiber 86 working channel connections cannot be established across the fiber span 62 There may be situations where it is desirable to deactivate underutilized working fibers on some spans yet still retain the ability to provision channel connections across these spans For example in matched node network configurations equipped with drop and continue on working DCW traffic connectivity it is often desirable to remove underutilized working fibers yet preserve the ability to provision channel connections on spans where DCW connectivity is necessary An example of a conventional matched node BLSR network which supports DCW traffic is shown in FIG 3 and is generally denoted by 100 Similarly to the BLSR network 10 of FIG 1 the BLS
27. ovi sioned on a physical fiber According to the invention when a working fiber between any two nodes in an existing ring network is underutilized the traffic scheduled for transmission thereon is re routed around the network away from the fiber As a result the fiber and associated connecting equipment thus become unused and unnecessary for traffic carrying purposes and can then be deactivated Advantageously the present invention eliminates the need for working fibers and associated optics equipment on spans where traffic is low or non existent and can provide fiber and equipment capacity savings of up to fifty percent on each span while retaining full protection usage According to the invention the unused fibers and equipment can be removed or alternatively be re provisioned to provide a cost effective and efficient allocation of the resources available in the network Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a diagram of a conventional four fiber bidirec tional line switched ring BLSR network featuring a plu rality of working fibers FIG 2 is a diagram of the four fiber BLSR network of FIG 1 with a reduced plurality of working fibers according to a preferred embodiment of the inventio
28. r channel capacity requirements Conversely a two fiber BLSR configuration could be used where each span 50 52 54 56 60 61 62 63 64 65 is implemented using a single bidirectional fiber for both working and protection bandwidth In the following descrip tion and for the purpose of example only the BLSR network 10 is assumed to be a four fiber network In the BLSR network 10 traffic is typically routed with standard network management applications such as the well known integrated network management INM For the purpose of example it is hereinafter assumed that the network management application used in the BLSR network 10 to route traffic is INM INM provides the necessary functionality to route traffic around the BLSR network 10 In the absence of failures INM manages the routing of working traffic between the nodes 12 14 16 18 20 22 along the East West working fiber 30 32 42 44 and the North South working fibers 82 84 86 88 90 92 present in the network 10 As is conventional a localized controller present at each node 12 14 16 18 20 22 supports the protection capabilities of span and ring switches redirecting traffic around failures In the event of a failure or degradation of a working fiber the nodes 12 14 16 18 20 22 can enter a span switching mode to redirect traffic away from the fault and prevent a service outage In this mode the interrupted traffic is redirected from the defective working fiber on
29. rs in the above identified patent and that said Letters Patent is hereby corrected as shown below Column 12 Line 6 after the word applying a semicolon has been inserted it should be deleted Signed and Sealed this Twenty eighth Day of October 2003 JAMES E ROGAN Director of the United States Patent and Trademark Office
30. ss the span 152 More specifically a user invoked manual switch is permanently applied at the nodes 114 118 to position the DCW traffic on the protection fiber 134 In order to redirect DCW traffic on the protection fiber 134 the manual switch preempts the span and ring lockouts described above It will be recalled that these lockouts prevent automatic switch access to the protection fiber 134 However they are not designed to preempt user requests Because the manual switch is applied as a user request the manual switch can override the span and ring lockouts and place the DCW traffic onto the protection fiber 134 despite the presence of the span and ring lockouts Similarly to the span and ring lockouts however this persistent manual switch will not preempt any ring protec tion switches from using the span 152 As a result the protection fiber 134 can still provide full ring protection capabilities to traffic elsewhere on the ring 102 but will also accommodate the DCW traffic when not used for ring protection This is because the manual switch is a special persistent manual switch that recurs after being preempted by a ring protection switch Therefore by placing the DCW traffic on the protection fiber 134 the working fiber 136 can thus be deactivated for removal and the necessary DCW connectivity on the span 152 maintained With the LWO U mode activated at the nodes 114 118 the span and ring traffic except the DCW traffic is redi
31. stem for a cost effective and efficient allocation of the fiber resources available in the ring network When a working fiber is underutilized in an existing ring network the traffic scheduled for transmission thereon is re routed around the network away from the fiber and lockouts are applied to prevent the fiber to be removed from being protected The fiber and associated connecting equipment thus become unused and unnecessary for traffic carrying purposes and can then be deactivated By eliminating the need for working fibers and associated optics equipment on spans where traffic is low or non existent the invention can provide fiber capacity savings of up to fifty percent on each span while retaining full protection usage According to the invention the unused fibers and equipment can be removed or alter natively be re provisioned for use in other network configu rations to provide a cost effective and efficient allocation of the resources available in the network 36 Claims 4 Drawing Sheets BLSR i NETWORK SECOND BLSR RING 10 US 6 529 298 B1 Sheet 1 of 4 Mar 4 2003 U S Patent el eek ae See _ 5198 0 0935 cg 98 S bl LL 5518 159 l 1 i l 4 M N ie nea 81 09 78 919 NOLLIALOYd WNOLLSSHIG
32. to a protection fiber available between the affected nodes 12 14 16 18 20 22 thereby maintaining service for all terminating span through ring traffic If a fault affects an entire fiber span between any two adjacent nodes 12 14 16 18 20 22 e g a node failure or a cable cut of both working and protection fibers in the fiber span the affected traffic can be re directed around the network 10 by ring protection switching In the BLSR network 10 all fiber spans 50 52 54 56 60 61 62 63 64 65 separating adjacent nodes 12 14 16 18 20 22 have to be fiber equipped because of the protection usage that is necessary on a ring protection switch However this requirement only makes use of the protection fibers 34 36 38 40 70 72 74 76 78 80 If there are fiber spans 50 52 54 56 60 61 62 63 64 65 in the network 10 where traffic is light the working fibers in these spans 50 52 54 56 60 61 62 63 64 65 may be under utilized and in some cases unused In optical ring networks such as the BLSR network 10 it is quite common that traffic is concentrated on East West fiber spans with little or no traffic transmitted along North South spans In such networks the working fiber bandwidth available on these North South spans is not efficiently utilized and in many instances may not even be needed for traffic carrying purposes Because of this the capital investment incurred in installing and maintai
33. used in a bidirectional line switched ring BLSR network An example of a conventional four fiber BLSR optical network with which the invention can be used is shown in FIG 1 generally denoted by 10 The BLSR network 10 consists of multiple rings interconnected at common nodes 12 14 16 18 20 22 connected to form a series of interworking rings For the purpose of example FIG 1 only shows two com plete rings where a first ring 11 is formed of nodes 12 14 18 20 and a second ring 13 is formed of nodes 14 16 20 22 The nodes 12 14 16 18 20 22 are interconnected with a number of bidirectional East West and North South fiber spans which can provide working and protection transport between the nodes 12 14 16 18 20 22 More specifically the nodes 12 14 16 are interconnected with bidirectional East West fiber spans 50 52 where each East West fiber span 50 52 consists of bidirectional working fiber 30 32 shown as a full line and a bidirectional protection fiber 34 36 shown as a dotted line Similarly the nodes 18 20 22 are interconnected with bidirectional East West fiber spans 54 56 each formed of a bidirectional working fiber 42 44 full line and a bidirectional protection fiber 38 40 dotted line The nodes 12 14 16 are respectively interconnected with the nodes 18 20 22 with a number of North South fiber spans More specifically node 12 is interconnected with node 18 with a first pair of North South fi
34. y cost containment bandwidth efficiency and survivability Common network topologies include point to point terminal configurations linear add drop multiplexer configurations and ring configurations Of all these different topologies ring configurations are often the preferred net work configuration for applications requiring high transport capacity In optical ring networks the bandwidth available in each fiber interconnecting nodes can be allocated in various ways to meet different capacity demands In some ring configurations the bandwidth available for transport can be provisioned as a single optical transmission path However in the vast majority of ring configurations the bandwidth is partitioned into channels or wavelengths to increase capac ity In optical ring networks as in other optical configurations it is common to use the term fiber generally to denote traffic carrying capacity As such in addition to denote physical fibers the term fiber can also be used to denote single channels or wavelengths in a physical fiber For clarity and unless stated otherwise the term fiber as applied generally to optical networks is hereinafter used to denote both a physical fiber and a single channel or wavelength within a physical fiber In addition to providing large capacity optical ring sys tems are also designed with redundant equipment to have other attributes such as for example bidirectionality and or increased reliability t
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