[Tutorial] NG-PON2 Technologies. Hirotaka Nakamura NTT Access Network Service Systems Laboratories, NTT Corporation

Transcription

1 [Tutorial] NG-PON2 Technologies Hirotaka Nakamura NTT Access Network Service Systems Laboratories, NTT Corporation

2 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON and NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary - 2 -

3 Number of subscribers [million] 1-1. Broadband subscribers in Japan FTTH users based on 1G-class-PON are rapidly increasing and reached 22 million in June FTTH(Total) M FTTH(NTT) M 10 DSL 6.3 M 5 CATV 6.0 M Year - 3 -

4 1-2. Evolution of optical access network (1) OLT OSU 1 st step (PtoP) OSU OSU OSU 1 st L2SW 2 nd L2SW SSE (Subscriber service edge) To reduce CAPEX (1 st stage L2SW, numbers of OSUs and fibers), photonic aggregation function of PON system replaced the electronic aggregation function of the Layer 2 switch by using power splitter, burst-mode transmission, and dynamic bandwidth allocation (DBA) technologies. Power splitter OLT OSU DBA 2 nd step (PON) 2 nd L2SW SSE Burst transmitter Dynamic bandwidth allocation (DBA) Burst receiver

5 1-2. Evolution of optical access network (2) 2 nd step (PON) Power splitter OLT OSU DBA OSU DBA OSU DBA 2 nd L2SW SSE OSU DBA Photonic aggregator will replace 2 nd stage L2SW to reduce the number of OSUs and the power consumption in the consolidated central office. OLT 3 rd step (NGOA) Power splitter Central office consolidation PA OSU DBA SSE Photonic aggregator (Power splitter or Cyclic AWG) Wide-area photonic aggregation network (Long-reach PON)

6 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON and NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary - 6 -

7 ITU-T Study Group 15 Optical and other transport network infrastructures 2-1. ITU-T & IEEE Liaison IEEE Project Service Interoperability of Ethernet PON (SIEPON) Question 2 Optical systems for fibre access networks G.983 (B-PON) G.984 (G-PON) G.985 (100M-MC) Propose FSAN OAN-WG (Optical Access Network Working Group) IEEE working group CSMA/CD (ETHERNET) 802.3ah EFM Ethernet in the First Mile 1000BASE-PX(GE-PON) G.986 (1G-MC) G.987 (XG-PON) G.988 (OMCI) Technical discussion about B-PON, G-PON, XG-PON, NG-PON2 100BASE-BX(SS) 1000BASE-BX(SS) 802.3av - 10G PHY 10GBASE-PR(10G-EPON) G.989 (NG-PON2) G.Epon (EPON with OMCI) G.Multi (MW-PON) 802.3bk Extended PON Extended GE-PON, 10G- EPON - 7 -

8 Total bandwidth [bit/s] 2-1. Standardization trends of PON system Now 100G 100GbE 40GbE NG-PON2(2015) 10G 1G 1GbE 10GbE 10G-EPON G-PON GE-PON XG-PON SIEPON(2013) IEEE Ethernet IEEE PON ITU-T PON 100M 100BASE-T B-PON 10M 10BASE-T Year - 8 -

9 2-3. Basic concept of PON system UNI ONT ODN Downstream (from OLT) UNI UNI NT DSL ONT Upstream (to OLT) Optical Splitter Optical Fiber OLT SNI Core / Metro Networ k OLT (Optical Line Terminal): Central office equipment of PON ONT (Optical Network Terminal): User side equipment of PON for FTTH (Optical Network Unit): User side equipment of PON for FTTC ODN (Optical Distribution Network): Transmission network between OLT and ONTs/s UNI: User Network Interface SNI: Service Node Interface

10 2-2. User multiplexing and multiple access technologies Down and upstream signals multiplexed by single fiber WDM #1 #2 Downstream signals multiplexed by TDM Downstream Upstream OLT #N Guard time Upstream signals multiplexed by TDM

11 2-2. User multiplexing and multiple access technologies B-PON TDM leased line POTS Ethernet ATM cells Ethernet OLT TDM leased line POTS G-PON and XG-PON Ethernet TDM leased line GEM frame GTC frame Ethernet TDM leased line POTS 125usec (Downstream) OLT POTS GEM: G-PON Encapsulation Method GTC: G-PON Transmission Convergence Ethernet frame can convey TDM and POTS data by some GE-PON and 10G-EPON emulation technologies Ethernet Ethernet frame Ethernet OLT

12 2-2. Ranging/Discovery It is necessary to measure distances/rtts between OLT and s in order to assign upstream bandwidth to s without any collision. (Case of B-PON) OLT (TX) OLT (RX) PLOAM Cell Ranging Grant (PLOAM cell) #n ATM Cell O H Response time of #n ATM Cell O H ATM Cell Ranging cell Response time of #n Round trip time of #n O H O H ATM Cell Raging window ATM Cell The window size is Mb/s = 0.2msec = 20km for one-way O H ATM Cell O H ATM Cell

13 2-2. Dynamic Bandwidth Allocation OLT assigns the bandwidth to each based on its bandwidth requirements. -A -B -C -D 2. Each reports its queue status to OLT. 1. OLT requests the queue status to each. Shared bandwidth Occupied bandwidt h OLT 3. OLT assigns the bandwidth to each.

14 2-3. General scope of G-EPON standard IEEE only covers physical layer and a portion of data Link layer OSI Reference Model Application Presentation Session Transport Network IEEE Layering Diagram Logical Link Control MAC Control Media Access Control (MAC) Reconciliation Gigabit Media Independent Interface (GMII) Physical Coding Sublayer (PCS) Physical Medium Attachment (PMA) OAM MPCP Data Link Physical Physical Medium Dependent (PMD) Medium Dependent Interface (MDI) Medium 14

15 2-3. Position of G-EPON Standard IEEE802.3ah calls Ethernet in the First Mile (EFM). IEEE802.3ah includes not only GE-PON but also optical point-to-point system and metallic transmission system (DSL). IEEE802.2: Logical Link Control IEEE802.3 Ethernet MAC layer IEEE802.4 Token bus MAC layer IEEE802.1: bridging IEEE802.5 Token ring MAC layer IEEE MAN MAC layer IEEE Wireless MAC layer layer 2: Data link layer Physical layer Physical layer Physical layer Physical layer Physical layer layer 1: Physical layer P-MP(EPON) G-EPON access control protocol 10Mb/ s 100Mb/ s 1Gb/s 10 Gb/s ah EFM PMD&P-P Copper Optical P-P system metallic transmission system OAM operation and maintenance function 15

16 2-3. Position of G-EPON Standard G-EPON System consists of both standardized and "out of scope specifications". The "out of scope specifications" help distinction from the other products, but prevent inter-operability between 1G-EPON products. Standardized specifications Basic functionalities for transmission IEEE802.1AE, AF IEEE802.3ah(EFM) Technical specifications are matured. Standardization completed in June G-EPON System OAM (Optional) MAC/MPCP PHY Ops IF DBA/QoS Link Security Sys. Cntrl. Out of scope specifications System functionalities for carrier service provisioning Operation system interface OAM&P, Test, DB-IF. DBA (Dynamic Bandwidth Assignment) Bandwidth control Authentication User/ registration/deregistration System OS Private MIB, Alarm process System configurations Fault recovery, powering, cooling. 16

17 2-3. EPON MAC frame Pre-amble is extended in order to uses as PON header that consists of SPD, LLID, and CRC. LLID distinguishes logically. The other frame structure of GE-PON is the same as GbE. 8Bytes 6Bytes 6Bytes 2Bytes 46~1500Bytes 4Bytes GbE MAC frame Pre-amble/ SFD DA SA Type/ Length Data FCS The first 8 Bytes of EPON MAC frame 2Bytes Reserved Modified 1Byte SP D 2Bytes Reserved 2Bytes LLID 1Byte CRC SPD (Start of Packet Delimiter) shows the MAC frame is used for GE-PON. LLID (Logical Link ID) distinguishes logical connections between OLT and. The first bit of LLID is called ModeBit, which shows Unicast frame for 0 and Broadcast frame for 1. CRC (Cyclic Redundancy Check) is used for confirming consistency of LLID. 17

18 2-3. PHY layer specification for G-EPON PHY layer consists of three sub-layers, PMD, PMA and PCS PMD is newly defined for GE-PON, but PMA and PCS are expanded from the other Giga-bit Ethernet specifications Reconciliation GMII MDI PCS PMA PMD To MAC layer Optical fiber Reconciliation GMII (Gigabit Media Independent Interface) PCS (Physical Coding Sublayer) PMA (Physical Media Attachment) PMD (Physical Medium Dependent) MDI (Medium Dependent Interface) Optical splitter OLT PCS: 8B10B codec (Mandatory), Forward Error Correction (FEC; Optional) PMA: Bit synchronization of burst signals, Group synchronization with 10bit PMD: Power, wavelength and eye pattern of optical signals, ON/OFF time of LD 18

19 2-3. MAC layer specification for G-EPON MAC layer includes MAC sub-layer which is common in all Ethernet interface, and Multi-Point MAC Control sub-layer which is specified for 1G-PON. Each MAC of OLT corresponds to a MAC of a. OAM Multi-Point MAC Control Instance MAC PHY layer Optical fiber Instance means Multi-Point MAC Control Instance Multi-Point Transmissio n Control OAM OAM OAM Instanc e Optical splitter Instanc e Instanc e MAC MAC MAC PHY layer OLT -Multi-point MAC control sub-layer consists of Multi-Point Transmission Control and Multi-Point MAC Control Instance. -The instance and MAC manage the GE-PON system as a point-to-point system. -The control selects an active instance for each Ethernet frame. 19

20 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON and NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary

21 2-4. G-PON Recommendation Basic specifications of G-PON have been completed. ITU-T and FSAN discuss the modifications of G.984 series for the better interoperability and the easier implementation. No. Outline Approval date G G-PON Service requirements Mar (Revised) G G G-PON Interface between OLT- physical layer specifications G-PON Interface between OLT- TC layer specifications Mar Mar Amd2 Mar (Revised) Nov Amd2 G G-PON ONT management control interface regulation G Enhancement band of G-PON G G-PON reach extension Feb (Revised) Jul Amd3 Sep Oct Amd1 Mar Nov Amd1 G G-PON long reach Jul

22 2-4. G.984.2: Physical Layer Specifications Bit rate Items Correction of errors by fiber dispersion optical device overhead of upstream signal ODN Classes (Optical Loss between OLT and ) Specifications Gbit/s for upstream and Gbit/s for downstream Error rate: better than 1E-10 FEC is used only for 2.488Gbit/s FP-LD. No error correction is necessary for DFB-LD. DFB-LD+PIN (APD is also available) 4Bytes (155.52Mbit/s), 8Bytes (622.08Mbit/s) 12Bytes (1.244Gbit/s), 24Bytes (2.488Gbit/s) Class A: 5 20dB Class B: 10 25dB Class B+: 13 28dB Class C: 15 30dB 22

23 2-4. G.984.3: Service accommodation GEM frame encapsulates a service frame identified by Port-ID. GTC frame is a 125ms length frame for downstream, and as for upstream, it carries T-CONT which manages upstream bandwidth. PON T - CONT T - CONT Port Port Port Port Port Port T - CONT Port Port T - CONT Port Identified by - ID GTC GEM Upstream Identified by Alloc - ID Identified by Port - ID 5 th layer And more 4 th layer 3rd layer 2 nd layer T1/E1 TDM Circuit Emulation POTS VoIP GEM frame 1 st layer PON-PHY Data GTC frame TCP+UDP etc. IP Ethernet Video GEM: Gigabit Encapsulation Method GTC: G-PON Transmission Convergence layer T-CONT: Transmission Container 23

24 2-4. Schematic diagram of G-PON TC (GTC) frame 1 PCBd*: Physical Control Block Downstream GTC fram e PCBd* Upstream Bandwidth Map Downstream 125ms Payload (consisting of GEM frames) AllocID Start End AllocID Start End GTC frame GTC frame OLT 128 T-CONT1 ( 1) T-CONT2 ( 2) PLOu PLOAMu PLSu DBRu X Payload X DBRu Y Payload Y Upstream 24

25 2-4. Downstream GTC frame structure PLOAM = Physical Layer OAM provides PON management functionalities, such as ranging, activation, establishment of OMCC and alarm transfer. PSync (4 Bytes) Ident (4 Bytes) PLOAMd (13 Bytes) BIP (1 Byte) PLend (4 Bytes) Plend = Payload Length downstream field specifies the length of the Bandwidth map (sent twice for high reliability) PLend (4 Bytes) Ident field is to indicate larger frame structures Physical Control Block Downstream (PCBd) Upstream Bandwidth Map Payload PLI = Payload Length Indicator is used to find the next header in the stream for delineation. GEM Header Frame GEM Header Frame PTI = Payload Type Indicator is used to indicate the content type of the fragment payload and its appropriate treatment PLI Port ID PTI HEC/TDM CRC/Enet 25

26 2-4. Upstream GTC frame structure GTC upstream frames are made up for each T-CONT. When upstream bandwidth that wants to launch is larger than T- CONT size indicated by the OLT, the upstream signal is divided into some frame fragments. -ID Msg ID Message CRC DBA CRC PLSu = Power Level Sequence field is used for power control measurements by the PLOu PLOAMu PLSu DBRu Payload Physical Layer Overhead GEM Preamble Delimiter BIP -ID Ind Header Ind = Indication field provides real time status report to the OLT Frame GEM Header PLI Port ID PTI Frame Fragment HEC/TDM CRC/Enet 26

27 2-4. Reach extension Reach extension (G.984.6) extends physical reach between OLT and by inserting optical amplifier(s) between OLT and optical splitter. Long reach (G.984.7) increases the difference between s by expanding ranging window UNI UNI R/S R/S ODN S'/R' Mid-Span Extender R'/S' OTL S/R OLT SNI OTL (Optical Trunk Line) means a span between OLT and optical splitter. Mid-span extender consists of one or more optical amplifiers in OTL, and extends the physical length of OTL. Schematic of expanded ranging window for 40km The window size is 450ms. The window size for 20km is 250ms. 27

28 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON and NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary

29 2-5. NG-PON roadmap J. Kani, et al., Next-Generation PON Part I:Technology Roadmap and General Requirements, IEEE Network Mag., pp.43-49,

30 2-5. Technical direction toward next generation PON Both PONs are based on the existing PON technologies, and are upgraded for 10Gbit/s. 10G-EPON can use G-EPON specifications for upstream. Item 10G-EPON(10G symmetric) XG-PON Services Ethernet data Full services (Ether, TDM, POTS) Frame 10G Ethernet frame XGTC/XGEM frame MAC layer Max number of FEC 32,768(Max of LLID) Up: RS(255, 223)Mandatory Down: RS(255, 223)Mandatory 1,024 (Max of -ID) Up: RS(255,239) Option Down: RS(255,223) Mandatory Line rate Up: Gbit/s Down: Gbit/s Up: 2.488Gbit/s Down: 9.953Gbit/s Physica l layer Transmission bandwidth* 1 10Gbit/s for upstream and downstream (64B66B coding) Maximum loss 20 / 24 / 29dB 29 / 31dB Same as the line rate (Scrambled NRZ coding) Optical OLT TX: +2~+5dBm RX(min): -25dBm TX: +2~+6dBm RX: -28~-8dBm level* 2 TX: +4~+9dBm RX(min): -27dBm TX: +2~+7dBm RX: -27.5~-7dBm *1: Including FEC bytes *2: In the case of 29dB optical loss 30

31 2-5. System level EPON standard SIEPON is a system level standard for EPON. G.epon is a new ITU-T Recommendation that is ITU-T version of EPON based on SIEPON Package and adopts OMCI instead of. Common Ethernet services HN management BBF TR-142 (TR-069 for PON) Service model BBF TR-156, 200 (TR-101 for PON) SIEPON G.988(Generic OMCI) PON management ( Ex. OAM) G.987 System Level Specifications Higher layer specifications ( Ex. QoS management) G.986 P2P) (1G- (XG- PON) G.984 (G-PON) 802.3av (10G-EPON) 802.3ah (GE-PON) MAC layer specifications ( Ex. Frame structure) Physical layer specifications ( Ex. Transmission bandwidth) ITU-T Recommendations G.epon IEEE standards 31

32 2-5. Layer structure of G.epon User data: The same layer structure as SIEPON. Management: OMCI is added to SIEPON. No difference regarding MAC control client extension. <User Data> <Management> UNI NNI EMS Data link layer MAC Client OAM Multi-Point MAC Control MAC Reconciliation XGMII and/or GMII OAM Client MAC Contr ol Client OAM functions OMCI MAC control client functions OAM Client functions Provisioning, Alarm, Statistics, Power saving, Protection, etc. Physical layer PCS PMA PMD MDI PH Y ITU-T G.988 IEEE P ( SIEPON) IEEE MAC control extension Described in Annex31C of [IEEE P802.3av]. Definition of the MAC control extension frame payload is reserved for ITU-T, and G.epon defines it. 32

33 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON/NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary

34 3-1. Applications of NGOA Telecom operator Residential NGOA Business M2M Mobile Wireless

35 3-1. Requirements of NGOA Operator reqs. Issues Technical candidates Enhanced application by largescale PON Node consolidation High capacity Long reach High splitting ratio WDM, High speed TDM, OFDM, advanced modulation Optical amplifier, Coherent receiver Multi-services High security WDM, OFDM Bandwidth effectiveness Smooth migration Energy efficiency High reliability Flexible bandwidth assignment Coexistence with legacy systems Incremental upgrade Decrease number of L2SWs & OSUs (= High splitting ratio) Sleep function(/olt) ODN monitoring, Protection for fiber/equipment failure DBA, WDM (tunable) WDM WDM (tunable) TDM (Large-scale DBA) Sleeping algorithm Integrated OTDR WDM (tunable)

36 3-1. TWDM-PON Time and wavelength division multiplexing PON system is primary system for NG-PON k k n-1 n-2 n-k l u1 l u2 l u1 l u2 l u4 l u4 l u4 l u2 l u1 - l un l d1 - l dn Legacy OLT l d1 l d2 l d4 TRx1 TRx2 TRx4 OLT MAC control SNI Bandwidth US:2.5G - 10Gbit/s/ch DS:2.5G - 10Gbit/s/ch Wavelength channels 4 8 Legacy Splitting ratio 64 Transmission distance 40 km Coexistence Legacy PON systems RF-Video system

37 3-1. WDM-overlay - Application requiring high capacity and low latency. - use a dedicated wavelength in both US and DS k k 2-1 l u2 l uk l u1 TRx1 TRx2 TRxm OLT MAC control SNI n-1 n-2 n-k Bandwidth Wavelength channels Splitting ratio Transmission distance Coexistence US:1G - 10Gbit/s/ch DS:1G - 10Gbit/s/ch Tbd Tbd Tbd Legacy PON systems RF-Video system

38 3-1. Coexistence of legacy PONs and NG-PON2 10G class PON are considered to migrate from 1G class PON by WDMA or TDMA technology. NG-PON2 is expected to coexist these PONs. Co-exist by WDMA Co-exist by TDMA NGOA ITU-T G.98x series B-PON 622M/155M G-PON 2.5G/1.2G XG-PON1 10G/2.5G G.epon ITU-T version of SIEPON NG- PON2 IEEE GE-PON 1G/1G Only for 10G/10G 10G-EPON 10G/10G 10G/1G SIEPON System level specifications for EPON

39 3-1. Wavelength allocation ITU-T All the PON systems use O-band for upstream transmission. The current PON systems use S-band and 10G class PON systems use L- band for downstream transmission. RF video service is available for any PON systems In NG-PON2, C-band for US and L-band for DS are discussed. XG-PON1 (2.5Gup / 10Gdown) G-PON Up Up Up Up Down RF Video signal Down B-PON Up Down 10GE-PON (10Gup / 10Gdown) 10GE-PON (1Gup / 10Gdown) Up Up Down Down GE-PON Up Down IEEE Wavelength (nm)

40 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON/NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary

41 3-2. Technical issues of NG-PON2 WDM technology is very suitable for NG-PON2 and following technologies are expected to be cost effectively developed for enhancement of NG-PON2 - Wavelength tunability - Wavelength management - Optical amplifier or coherent detection

42 3-2. Functions by wavelength tunability Function Colorless Incremental upgrade(pay as you grow) Load balancing Advanced power saving (OLT sleep) PON protection Flexible bandwidth assignment Description Eliminates complicated inventory management and improper connections between colored and OLT After installation of s, the total bandwidth can be increased incrementally by installing additional OSUs When the traffic of one OSU has a heavy congestion, some s communicate to other vacant OSUs. When there is less traffic, all s are connected to one OSU and the other OSUs can be forced to sleep When an OSU has failed, can continue its communication to other OSUs by changing its wavelength The optimized wavelength and timeslot are assigned to each in order to improve the usage efficiency of the wavelength and provide the bandwidth according to user demand

43 3-2. Colorless Configuration Modulation speed Tunable LD RSOA Spectrum slicing Injection-lock ~10Gbit/s ~2.5Gbit/s ~1.25Gbit/s ~1.25Gbit/s Loss budget Large Medium Medium Medium Number of wavelength W D M PD LD W D M 32~64 ~32 ~32 ~32 Cost High Medium Low Low PD RSOA W D M PD BLS W D M PD FP-LD BLS: Broadband Light Source, FP-LD: Fabry-Perot Laser Diode

44 3-2. Incremental Upgrades Colorless #1 10 G #2 10 G #3 #4 #5 10 G 10 G 10 G #7 #8 #7 #5 #8 #7#6 #5 #8 #6 #3 #6 #5 #4 #4 #2 #1 #2 #2#1 #4 #3 #3 #1#3 #5 #2 OLT 10 G OSU 10 G OSU 10 G OSU #6 #7 10 G 10 G Power Splitter #7 #1 4 x 4 Splitter 10 G OSU #8 10 G

45 3-2. PON Protection Colorless #1 10 G #2 10 G #3 10 G #8 #7 #4 #4 #2 OLT #4 10 G #8 #6 #3 #3 #1 10 G OSU 10 G OSU #5 10 G #6 #5 #5 #2 10 G OSU #6 #7 10 G 10 G #7 #1 Power Splitter 4 x 4 Splitter 10 G OSU X #8 10 G

46 3-2. Advanced Power Savings(OLT sleep) Colorless #1 10 G #2 #3 #4 #5 #6 #7 10 G 10 G 10 G 10 G 10 G 10 G #8 #8 #7#6 #5 #5 #7 Power Splitter #4 #4 #2 #3 #1 #2 #1 4 x 4 Splitter OLT 10 G OSU 10 G OSU 10 G OSU 10 G OSU Sleep Sleep Sleep #8 10 G

47 3-2. Basic Concept of G.multi New recommendation specifies system requirements, the architecture, and the protocol for multiple wavelength PON systems. Architecture of Multiple Wavelength PON system in G.Multi Multi Wavelength Multi Wavelength OLT Multi Wavelength OLT Splitter or Wavelength Mux/demux Multi Wavelength Multi Wavelength

48 Outline 1. Introduction 2. Standardization about optical access networks - GE-PON - G-PON - 10G-EPON and NG-PON 3. NG-PON2 technologies - Requirements - Technologies - beyond NG-PON2 4. Summary

49 Number of wavelength 3-3. Beyond NG-PON2 WDM (Multi-carrier Technology) G-PON GE-PON TWDM- PON(4-8l) NG-PON2 XG-PON 10G-EPON WDM/xDM-PON (beyond 100 G) NG-PON3? 25G 1G 10G TDM Capacity of single carrier xdm (OFDM?)

50 4. Summary Overview of PON technologies for TDMA-PON systems. - GE-PON, 10G-EPON, and SIEPON standardized in IEEE - G-PON, XG-PON, and G.epon standardized in ITU-T Discussion on NG-PON2 requirements and technologies. - TWDM-PON and WDM-overlay - Wavelength tunability and management - Beyond NG-PON2-50 -

51 Thank you!