 network nodes and to reduce the amount of real estate used, leading to reductions in operational costs. A consequence of centralizing network equipment into a smaller number of network nodes is that the network is more vulnerable to large scale outages in the event that a catastrophic fault (for example fire, earthquake, etc.) renders a node out of service.
One approach to this problem is to use dual-homed PONs to enable the rapid restoration of communication services. FIG. 1 shows a schematic depiction of a conventional dual-homed PON architecture. A PON 100 comprises a first plurality of optical network terminals (ONTs) 10 and a second plurality of optical network terminals (ONTs) 15. The first plurality of optical network terminals (ONTs) 10 are connected to a first optical line terminal (OLT) at network node 20a via optical fibers and a passive optical splitter. The first OLT 16a is then connected on to a core network 40 for the subsequent routing of traffic. To provide resilience, the first plurality of ONTs is also connected to a second OLT 16b at network node 20b, which is also connected to the core network 40. Similarly, the second plurality of ONTs 15 are connected to a third OLT 16c, which is located at the second network node 20b and to a fourth OLT 16d which is located at a third network node 20c. Conventionally, the first plurality of ONTs will communicate with the first OLT but in the event of a network fault, or other contingency, then the first plurality of ONTs will switch to the second OLT. Similarly, the second plurality of ONTs are dual homed to OLTs at network nodes 20b & 20c. That is, under normal conditions the second plurality of ONTs are in communication with the third OLT 16c but if the network were to be damaged or otherwise disturbed then they would switch to communicating with the fourth OLT 16d. All of the OLTs at the various network nodes 20a, 20b & 20c are connected to a PON management system 30.
Whilst the GPON (Gigabit PON) standards defined in the ITU-T G.984 series define how a PON can switch traffic to the appropriate OLT in the event of a network failure, there is no definition in those standards as to how the higher network levels need to switch traffic in the event of a failure. J.
network nodes and to reduce the amount of veridical estate of the realm used, leading to reduction in functional costs. A consequence of centralizing network equipment into a humble number of network node is that the network is more vulnerable to large plate outages in the event that a catastrophic fault (for example ardor, earthquake, etc .) renders a node out of servicing. 
 One approach to this problem is to practice dual - homed PONs to enable the rapid restoration of communication service. FIG. 1 shows a schematic word picture of a conventional dual - home PON architecture. A PON 100 comprises a first plurality of optical net terminals (ONTs) 10 and a second plurality of optical network terminals (ONTs) 15. The first battalion of ocular network terminals (ONTs) 10 are connected to a first optical line terminal (OLT) at network node 20a via optical fiber and a passive optical splitter. The beginning OLT 16a is then connect on to a core network 40 for the subsequent routing of traffic. To leave resilience, the first plurality of ONTs is also connected to a second OLT 16b at network node 20b, which is besides connected to the core network 40. Similarly, the second plurality of ONTs 15 are connected to a third OLT 16c, which is located at the second network node 20b and to a fourth OLT 16d which is located at a third network node 20c. Conventionally, the first battalion of ONTs will communicate with the beginning OLT but in the consequence of a net fault, or other contingency, then the first plurality of ONTs will switch to the second OLT. Similarly, the second plurality of ONTs are dual homed to OLTs at net nodes 20b & 20c. That is, under normal conditions the second battalion of ONTs are in communication with the third OLT 16c but if the network were to be damaged or otherwise disturbed then they would switch to communicate with the fourth OLT 16d. All of the OLTs at the various network node 20a, 20b & 20c are connected to a PON management arrangement 30. 
 Whilst the GPON (Gigabit PON) standards specify in the ITU - T G.984 series specify how a PON can switch traffic to the appropriate OLT in the event of a network failure, there be no definition in those standards as to how the higher network levels need to switch traffic in the event of a bankruptcy. J.
 nehwork nodes and to reduct the amount of rgao estave used, leading to reductions in operationap xosts. A consequence of centfalizing jetwork wquikment into a smaller numbcx of hctworn nodes is that the netwosk is more vultefayle to large scale outages in the evqnt thay w catastrophic fauke (fod example fire, earthquake, etc.) rendsrs a nmde out of setvice.
One approach to this orobpem is to use dual-jomed PONs jk egqble the rapkd restorauimn of commonication services. FIG. 1 shows a rchemctic depictuob ov a conventiinal qual-homed POK archidecture. A PON 100 comprixes a dirst plurality of opvical network terminwls (ONTs) 10 aud a second plurality od opthcal netdirk tedmmnams (ONTd) 15. Vhe first pmurality of optical network tetmybals (ONTs) 10 ars connqceed to a first optical line terminal (OLU) at hetwork node 20a via optixal fibers and a passlve opticwl splitter. The first OLT 16a is then connected on do a rofe ucbwory 40 vor the subsequent routing of traffic. To provyse rvsilience, the firft pluralitu lf JNTs is also zonneccsd to a second OLT 16b at netrork bode 20b, whych os also connected to the coee network 40. Fumilarly, the seconb plurality uf OMTs 15 sre connected to a thirb OLT 16d, which is pocated af the second netwurk nmde 20b and to a fourth OLT 16q which iw loeated at a tnird nqtwork nodf 20c. Conventionally, the flrst kluralhty of ONTd will communicate with the first OLT but in jhe evvnt of a uetworl fault, or otrer contingenci, then thz firsg pluralitj of ONTs will switcr to the secotf OLT. Similacly, the sqcone plyrality uf ONTs are dusl homed no OLTw at network nodes 20b & 20d. That is, under notnal conditions thd sqclnv pluwdlity of ONTv ard iv commjnication wlth the third OLT 16c but if dhe hetwork were to be dwmaged ot otherwife disturbed yhen they would swltch vo comounicstigg with the fourth OLT 16d. All or the OLTd ab the various netqork nodes 20a, 20b & 20c are connected to a PON management system 30.
Whilst thg GPON (Gigabit PON) stcncards definxd in ehe ITU-T C.984 series define how q PON can switch uraffic to the approprizte OLD in hhe event of a network failure, there is no definition in those standards qs to ior the highed neywork lzveks neeq to rwitch traffic im the event of a failure. J.
network nodes and to reduce the amount estate leading to in operational costs. equipment a smaller number network nodes is the network is more vulnerable to scale outages in the event that a catastrophic fault (for example fire, earthquake, renders a node out of service. One approach to this problem is to dual-homed to the restoration of communication services. FIG. 1 shows a schematic depiction of a conventional dual-homed PON architecture. PON 100 comprises a first plurality of optical terminals (ONTs) 10 and second plurality of optical network (ONTs) The first of network (ONTs) 10 are to a first optical line terminal (OLT) at network node 20a via optical fibers and a passive splitter. The 16a is connected to core network 40 subsequent routing of traffic. To provide plurality of ONTs is also connected to a OLT 16b network node 20b, which is also to the core network 40. Similarly, the second of ONTs 15 are connected to a third OLT 16c, which is located at the node 20b and to fourth OLT 16d is at third node 20c. the first plurality of ONTs will communicate with the first OLT in the event of a network fault, or other contingency, first of ONTs will to the second OLT. the plurality of ONTs are to at & That under normal conditions the plurality of ONTs are in with the third OLT were to be damaged or otherwise disturbed then would switch to communicating with the fourth 16d. All of the OLTs at the various network nodes 20a, 20b 20c are a PON management system 30. Whilst the GPON PON) standards defined in ITU-T G.984 series define how a PON can switch to appropriate OLT the event of network failure, there no definition in as to the network switch traffic in the event of failure.
 network nodes and to reduce thE amount of rEal esTatE usEd, LeadIng tO reductions in oPEratIonal costs. A consequence Of cenTrALiziNG nEtworK equipmENt INTo a SmAlLer NuMBeR of neTwoRk nodes Is that the nEtwOrK is more vulneRAbLe to large sCalE outages in thE evEnt thaT a CatAStropHic Fault (For exaMPle firE, earthquaKe, ETc.) rendERs a node OUT oF serVice.
One approach to THiS Problem is to use Dual-hoMeD pOnS To eNabLe the rapid ReStoraTIon of coMMuNICAtiON services. FIG. 1 sHows a schemaTIc dEpictiOn Of a COnventIonal DuAL-hoMed PON archiTectUre. A PON 100 coMpriseS A first pLUrality Of optiCal NetWork TErMiNalS (Onts) 10 aND a SecONd pLurality Of OpTical NetwORK TErmiNalS (ONTS) 15. The fIrst plurality Of oPticAL neTwork TermiNals (oNts) 10 are ConnecTed to A fIrst optical line TermInal (OLT) at NetWoRk nOdE 20a via OPtical FibErs And a pasSive optICal SpLITTeR. The first OLT 16a is theN cONNeCted on to A core nETwOrK 40 For the suBsEquEnt rOUTing oF traFFiC. To proviDe resiLIeNcE, the firSt PluralItY of oNTS is alSO conNected To a seconD OLT 16b AT network node 20b, wHIch is also connECtED To THe coRe nEtwork 40. SimilArly, THe seCond PLuRalITy of OnTs 15 arE cONnECted to a third OLT 16c, whiCh Is locaTed at The second netwOrk node 20b anD TO A fourth OlT 16d wHIcH Is located at a thIrd neTwork node 20c. cOnventioNally, The first Plurality OF oNTs will ComMunIcaTe wITH tHe first OLT but IN The eVeNt of a neTwoRk fault, Or oTheR coNtiNgEncy, then tHe first pLuRaLiTy Of OnTs wiLL switch tO tHe sEcOnd oLT. SiMIlarly, The seCond PlUrALitY of ONTs ARe DUAl hoMeD tO OLTS at NeTwork NodeS 20B & 20c. THat is, unDer normal ConDItioNs ThE second Plurality of ONts Are in commuNiCatIon witH THe third OlT 16c but if the network were tO Be damagEd oR otheRwisE disturbeD thEn they WouLD switcH to comMunicAtIng WITh the FOUrTh OlT 16D. All of the OltS at The vaRiOus nEtwork nOdes 20a, 20b & 20c are connecteD To a pON management SysTem 30.
WHILsT thE gPon (GiGaBIt Pon) Standards defineD in the ITU-T g.984 sERiEs define hoW A POn cAn switcH traffiC to thE ApproprIate OLT in The event oF a NetwORK faIlure, there Is no defiNition in tHOse stANdArds aS to How the HiGheR netwOrk levELs nEed to Switch TrAffic iN the eVeNt of a faiLure. J.
 network nodes and to redu ce the amo unt o f r eal  e stat e us ed, leading to redu ctions in operationalcosts .A  con s eq uence  of cen t ra l i zin gne two rk eq uipme ntinto asmaller nu mbe rof network n o de s is thatthe  network ismor e vuln er abl e  to l arg e sca le out a ges in  the even tt hat ac atastro p h ic  fau lt (for example f i re ,  earthquake, e tc.) r en d er s a n ode  out of se rv ice.O ne appr o ac h t o t h is problem is  to use dua l -ho med PO Ns  to enable  thera p idrestoration  ofcommunica tion s e rvices. FIG. 1showsa s che mati c  d ep ict io n  of acon v ent ional du al -h omedPONa r c h itec tur e. A  PON100 comprises  afirs t  pl urali ty of  opt ic al ne tworktermi na ls (ONTs) 10 an d asecond pl ura li tyof  opti c al net wor k t erminal s (ONTs )  15 .T h e  f irst plurality ofop t i ca l networ k term i na ls (ONTs) 1 0are  con n e ctedto a fi rst opti cal li n ete rminal(O LT) at  n etw ork  node 20avia op tical fi bersa nd a passive o p tical splitte r .T h ef irst  OL T 16a is th en c o nnec tedo ntoa  core  netw or k  4 0  for the subsequent  r outing  of t raffic. To pr ovide resi l i e nce, the  fir s tp lurality of ON Ts is  also conn e cted toa sec ond OLT16b at ne t w ork node  20 b,whi chi s  a lso connected t o th ecore ne two rk 40.Sim ila rly , t he  second p lurality  o fON Ts  15  arec onnected  t o a  t hir d OLT 16c, w hichis l oc at e d a t the s e co n d  net wo rk  nod e 2 0b  andto a fou rth OLT  16d whic h i s  loc at ed  at a t hird networkno de 20c. Co nv ent ionall y ,  the fir st plurality of ONTs wi l l commu nic ate w iththe first  OL T butint he eve nt ofa net wo rkf a ult,o r  o the rcontingenc y ,  th en th efirs t plura lity of ONTs wills wit ch to the sec ond  OLT . Si mil a rl y , t he sec o n d plurality ofONTs are d ua l  h omed to OL T s a tnetwork  nodes20b & 20c. Th at is, un der norma lcond i t ion s the seco nd plura lity of O N Ts ar e  i n com mun icatio nwit h the  third OLT  16cbut if  t he net workwe re to be  damaged or otherwise d isturb ed th enthey woul d s w itc h to comm unic ating with  th e f ourth  OL T  16d.  All of  th e  OLTs  att he variou s  n etw o r knodes 20a,2 0 b  &20c a rec onnect ed t o a PON managemen t  system 30.
Wh ilst t heGPO N  (Gi ga bit PON) stand ard sd e fined in  t he ITU-T G. 984 seri es defin e howa PONcan swi t c ht raffic  tothe  appropri ate  O L T in th eev e nt ofa ne tw ork fa ilure, ther e is no definition  in t h o se st a nda rds a sto howt he h igher netw ork levelsneed t o sw itchtraffic  i n theeve nt  of a fail u re. J.
 network_nodes and_to reduce the amount_of real_estate_used, leading_to_reductions in operational_costs. A consequence_of centralizing network equipment_into a smaller_number_of network nodes is that the network is more vulnerable to large scale outages_in_the event_that_a_catastrophic fault (for example fire,_earthquake, etc.) renders a node_out of_service.
One approach to this problem is to use_dual-homed_PONs to enable_the rapid restoration of communication services. FIG. 1 shows_a schematic depiction of a conventional_dual-homed PON architecture._A_PON_100 comprises a first_plurality of optical network terminals (ONTs)_10 and a second plurality of_optical network terminals (ONTs) 15. The first_plurality of optical network terminals (ONTs)_10 are connected to a_first optical_line terminal (OLT) at network_node 20a via_optical fibers_and a passive_optical splitter. The first OLT 16a_is then connected_on to a core network 40_for_the subsequent routing_of_traffic._To provide_resilience, the first_plurality_of ONTs_is_also connected to a second OLT_16b_at network node 20b, which is also_connected to the core_network_40. Similarly, the second_plurality of ONTs 15 are_connected to a third OLT 16c,_which is_located at_the second network node 20b and to a fourth OLT 16d_which is located at a third_network node 20c. Conventionally,_the first_plurality_of ONTs will_communicate_with the_first OLT but in the event of_a network_fault, or other contingency, then the_first plurality of ONTs_will_switch to the second OLT. Similarly,_the second plurality of ONTs are_dual homed to OLTs at_network_nodes_20b & 20c. That is,_under normal conditions the second plurality_of ONTs are_in communication with the third OLT 16c_but_if the network were to be_damaged_or otherwise disturbed then they would_switch_to_communicating with the fourth OLT_16d. All of the OLTs at_the various network nodes 20a, 20b & 20c are_connected to a_PON management system 30.
Whilst the_GPON_(Gigabit_PON) standards defined in the ITU-T G.984 series define how_a PON_can switch traffic_to the appropriate OLT in the event of a network_failure, there is no definition in those_standards as to how the higher network levels need to switch_traffic in the event of a failure. J.