Key Features:• Sparse Population. User density is usually verylow. Cost of Deployment per user is High• User premises are distributed over a largergeographical area. Fiber length per user ishigh• Generally far from the urban regions. Morefiber required to connect to the metro/corenode as well• OSNR problem due to longer fiber portions infeeder and distribution part.
Standard network architectures:Fig: GPON architecture (ITU-T G.984 standard)With this architecture we cannot reach many users in rural areas asthe span of reach is constrained within 20 Km. Suitable for denserURBAN regions.Courtesy: TELNET
A Step forward towards a Long-ReachUsing GPON Extender (typically an 1:1 Amplifier or regenerator)the span of the network can be increased to 60 Km and can serveas many as 128 users per OLT. Suitable for less dense and sparselydistributed population.Courtesy: TELNET
A Better and Flexible Architecture:GPON extender with multiple branching allows adding splitters and ONUs at alater stage without affecting the total reach or the OSNR at the other ONUs. 256users can be reached.Courtesy: TELNET
Proposed Network architectures:Proposals aboutarchitecture andnetwork elementsAdvantages anddiscussions on theResultsUniversity ofMelbourne.(R.S. Tucker)*• Raman Amplifier & SOA at OLT• Dual wavelength (US-DS)• 1:32 split ratio• Passive Long-Reach Field• 60 Km.• Implementation in Tasmaniaresulted in decrease of COnumbers from 96 to 27University ofMelbourne.(R.S. Tucker)**• Dual-Fiber• EDFA at the CO keeping the feederand distribution section passive• 1:64 split• About 15% less power required intransmission• Reach can be increased byincreasing signal power• Simple upgradability• High bandwidth in upstream anddownstreamUniversity ofCalifornia, Davis.Lei Shi, Avishek Nag #• BER-aware wavelength allocationin WDM PON• Remote Nodes in the Networkwhich contains AWG & EDFA• Average BER per ONU increases• Suitable for LR-PON architectureas BER is one of the mainstreamissues in design of such anetworkK. Kanonakis et. al.(IEEE members)(ACCORDANCE FP7) ++• OFDM-over-WDM/TDM• Use of Back-to-Back Amplifiers• No-amplification required fortransmission of 78 km• Upgradability is easier• Less power, more bandwidth, lessBER
Proposals aboutarchitecture andnetwork elementsAdvantages anddiscussions on theResultsDarren P. Shea et. al.(BT networks) ^^• 1024-split architecture• Use of EDFAs in the backhaulsection of 90 Km• 3-stage splitting in thedistribution section• Very long reach of about 100km• Multi-stage amplificationrequired• Addition of noise anddegradation of OSNR• Non-passive fieldITM, KTH & AtellusAB(Sweden)H.E. Sandstrom et. al.• 3 access nodes in the network• Splice points and splitters forend-users• Using amplifiers and regeneratorsinstead of increasing Cos• Economically possible todistribute access networks inareas with <1 person/km• Laying of fiber besides main-stream roads only for accessnetworks is a better optionC.H. Chang et. al.National University ofTaiwan• OFDM and AWG• BTB amplifiers• Less BER with less Power ascompared to non-OFDMarchitectures• Reach can be increased usingsuch BTB techniques
Key points of these architectures: Amplifiers at the central office Remote node in a network: Upgradability and further reach Back to Back amplifiers OFDM (over WDM/TDM) Fiber deployment along Primary/Main Roads
Genetic Algorithm Based Network Planning:GU Rentao et. al., Beijing, ChinaEvolutionary 2-stage methodThe best locations of splitters are chosenWith the splitter location, the optimal solution for best connectionarrangement is found outLosses have been considered alongside maximum reachGives very good results with error of less than 0.5% even with 256 ONUs
Open Problems:o Use of amplifiers in various stageso Using OFDM in rural areas with fiber deployment alongside Roads onlyo Using Back to back amplifiers in the feedero Dual-fiber architectureo Genetic algorithm approach
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