PON Passive Optical Networking Objective At the end

PON Passive Optical Networking

Objective At the end of the course, you’ll be able to … understand how fibers work, and explain which components are used in an optical relay system internal reflection, transmitter, amplifier, receiver, splitter, … explain the basic properties of a passive optical network describe the functions of the components present in a PON based network correctly use basic PON terminology

3 Table of Contents Optical fiber fundamentals GPON fundamentals PON standardisation

4 Optical Fiber Fundamentals 1

5 Advantages of fiber Extremely high bandwidth Smaller-diameter, lighter-weight cables Lack of crosstalk between parallel fibers Immunity to inductive interference High-quality transmission Low installation and operating costs No Interference Large capacity

6 Optical fiber structure Core thin glass center of the fiber where the light travels Cladding outer optical material surrounding the core that reflects the light back into the core Coating plastic coating that protects the fiber from damage and moisture

7 Optical fiber classification glass glass core – glass cladding lowest attenuation most widely used plastic plastic core – plastic cladding highest attenuation pioneered for use in automotive industry plastic-clad silica glass core – plastic cladding intermediate attenuation

8 Optical fiber types G.651 – MMF – Multi-mode fiber large(r) core: 50-62.5 microns in diameter transmit infrared light (wavelength = 850 to 1,300 nm) light-emitting diodes G.652 – SMF – Single mode fiber small core: 8-10 microns in diameter transmit laser light (wavelength = 1,200 to 1,600 nm) laser diodes 8 – 62.5 um 125 um Cladding Core Coating 245 um

9 Total internal reflection Concept light travels through the core constantly bouncing from the cladding Distance a light wave can travel great distances because the cladding does not absorb light from the core Signal degradation mostly due to impurities in the glass core cladding acceptance cone

10 Hit me baby one more time Atoms have a core with circling electrons What happens when a light photon bumps into an electron ? Electron is disturbed but falls back onto it’s original level : energy is released into a certain direction = scattering Electron is disturbed and reaches a higher energy level : energy is lost = absorption ray of light

11 The world of wavelengths Light is transported as a wave. The length of the wave determines the type of light (infrared, ultraviolet, …)

12 Attenuation as function of wavelength 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.8 Wavelength (microns) 2.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Attenuation (dB/Km) 0,85 µ band 1,30 µ band 1,55 µ band 0.0

13 Fiber optic relay system Optical transmitter produces and encodes the light signal Optical amplifier may be necessary to boost the light signal (for long distances) Optical receiver receives and decodes the light signal Optical fiber conducts the light signals over a distance

14 Transceiver Definition: a transmitter and a receiver in a single housing Practical implementation: transceivers typically come as SFP Small-Form-factor Pluggable unit

15 Lightwave modulation Digital light intensity does change in an on/off fashion NRZ - non return to zero 0 - weak optical signal 1 - strong optical signal Analog light intensity changes continuously

16 Fiber interconnections Interconnect fibers in a low-loss manner is a permanent bond needed ? – splice ! is an easily demountable connection desired ? – connector ! Terminal A Terminal B permanent joint demountable joint SPLICE CONNECTOR 0.3 dB 0.3 dB 0.1 dB 0.1 dB 0.1 dB 0.1 dB 0.1 dB

17 Joining fibers – Fiber alignment bad alignment cores are not centered big power loss good alignment cores are centered small power loss

18 angular physical contact some back reflection (small) return loss straight physical contact lots of back reflection (big) return loss Joining fibers – Fiber orientation

19 Joining fibers – Connectors Properties good alignment/correct orientation present at the termination point of the fiber always introduce some loss Connector types amount of mating cycles LC, FC, SC, … Color code APC – green PC – blue Theoretical loss: 0.3 dB

20 Connectors - Couplers SC/UPC SC/APC ST/APC Couplers

21 Joining fibers – Splices Mechanical splicing aligning and orienting the fibers, then clamp the fibers in place Fusion splicing aligning and orienting the fibers, then fuse (melt) the fibers using an electric arc typical case used to enclose fiber optic splices in an outside plant environment Theoretical loss: 0.1 dB Fusion splicer

22 Optical power splitters Optical splitters … typically divide an optical signal … from a single input into multiple (e.g. two) identical output signals and generally provide a small optical loss to the signal passed through it l1 l1 3.5 dB insertion loss Passive

23 Optical wavelength splitters Wavelength Division Multiplexing … enables the combining of … multiple wavelengths into one single fiber Depending on the design, an optical wavelength splitter … typically provides … a small to medium loss to the signals passed through it 0.3 dB loss insertion loss Passive

24 PON benefits purely passive fiber plant low maintenance costs and high reliability shares feeder fiber over multiple users less fibers needed, less ports needed at CO fiber is virtually not limiting the bandwidth much higher bandwidth x distance than copper networks fiber’s bandwidth can be further exploited by WDM or equipment upgrade installed fiber infrastructure is future-proof PON offers bundled services over a single fiber triple play – voice / data / video

25 PON deployment scenarios – FTTx OLT Network ONU ADSL ( < 6 KM ) < 8 Mbit/s FTTEx ONU ADSL/VDSL ( < 1 KM ) < 26 Mbit/s FTTCab VDSL ( < 300 M ) < 52 Mbit/s FTTC ONT FTTH/B Central Office XNT XNT XNT ONU

26 GPON fundamentals 2

27 Aggregation Transmit Receive Customer Premises Equipment (CPE) (P2P) Point-to-Point 1:1 Two Basic FTTH technologies x4 (P2MP) Point-to-Multi-Point used in GPON 1:64 to 1:128 Splitter Optical Line Terminal (OLT) Downstream Upstream Optical Network Terminal (ONT) 1490 1310 Subscribers LESS SPACE, LESS FIBRES, LESS DUCT SIZE

28 Definition - Feeders, Distribution, Drops 2 - 3 km 3 – 5 km <100 m Access Point Feeders (primary) Distribution (secondary) Drops POP Active Active Passive

29 PON properties PON – Passive Optical Network passive components splitters + WDM-device star topology p2mp – point to multipoint Ranging distance 60 km maximum logical reach 20 km differential distance Split-ratio Minimum 64 subscribers (or more) PON No Equipment No Power

30 PON lambdas Voice and data over a single fiber two wavelengths in opposite directions Video one wavelength in downstream direction Splitters 1490 nm 1310 nm Data path 1550 nm Video path V-OLT P-OLT

31 Splitter - Types PLC – Planar Lightwave Circuit - Built into glass waveguides - Solid state - No mechanical parts - Compact Splits: 1x4, 1x8, 1x16, 1x32 Splits: 2x4, 2x8, etc FBT – Fused Biconic Taper Two fibers fused to create a split Typical fusion of 2, 3 or 4 fibres Splits in cascade Type 1: FBT Type 2: PLC

32 Splitter – Size 3M

33 Splitters – Example Available in various splice trays and terminals Available with factory terminated pigtails CONNECTORISED SPLICED - Flexible - Patch cords included - Easy to replace - Cheap - Maintenance free - Skilled technician 3M 3M

34 Optical power budget loss in splitters cascaded splitter can be used e.g. 1:4 splitter followed by 1:8 splitter or vice versa so a one-step 1:32 splitter can be used loss in WDM coupler loss per km fiber loss in connectors loss in splices Distance depends on loss in different components:

35 Data transceiver specifications (class B+) +5.0 P (dB) +1.5 +5.0 P (dB) +0.5 -8.0 P (dB) -27.0 -8.0 P (dB) -28.0 1490 nm 1310 nm path penalty: 0.5 dB path penalty: 0.5 dB Downstream budget: +1.5 – (-27) – (0.5) = 28 dB Upstream budget: +0.5 – (-28) – (0.5) = 28 dB Tx level Tx level Rx level Rx level 0.30 dB/km 0.42 dB/km

36 Optical power budget – Data Example: budget: 28 dB 16 way splitter loss: 13.8 dB (theoretical. 12dB) connector+splicing loss: 3 dB (24*0.1 dB + 2*0.3 dB) aging: 1 dB attenuation: 0.30 dB/km – downstream 0.42 dB/km – upstream Distance: (28 – 13.8 – 3 – 1) / 0.42 = 10.2 / 0.42 = 24.28 km Interpretation: for a 1:16 split, the max distance of an ONT is 24 km

37 Data transceiver specifications (class C+) +7.0 P (dB) +3.0 +5.0 P (dB) +0.5 -8.0 P (dB) -30.0 (**) -12.0 P (dB) -32.0 1490 nm 1310 nm path penalty: 1 dB (*) path penalty: 0.5 dB Downstream budget: +3 – (-30) – (1) = 32 dB Upstream budget: +0.5 – (-32) – (0.5) = 32 dB Tx level Tx level Rx level Rx level 0.30 dB/km 0.42 dB/km (*) Accounts for DS dispersion effects up to 60km reach (**) ONT sensitivity in C+ mode with FEC

38 Video transceiver specifications +18.5 P (dB) P (dB) -4.9 1550 nm Downstream budget: +18.5 – (-4.9) = 23.4 Tx level Rx level

39 Optical power budget – Video Example: budget: 23.4 dB 16 way splitter loss: 13.8 dB (theoretical. 12dB) connector+splicing loss: 3 dB (24*0.1 dB + 2*0.3 dB) aging: 1 dB attenuation: 0.25 dB/km - downstream Distance: (23.4 – 13.8 – 3 – 1)/0.25 = 22.4 km Interpretation: for a 1:16 split, the max distance of an ONT is 22.4 km

40 Splitter – Optical Budget Example: Splitter 1 x 8 Input Fiber Output Fiber 3.5dBm 3.5dBm 3.5dBm

41 Eric Maximum range per splitter - configuration 38 km 30 km 21 km 14 km ITU-T G.984 Standard 20 km

42 GPON protocol layers and formats GEM – GPON Encapsulation Method Ethernet + TDM ATM – Asynchronous Transfer Mode VG Ethernet [AAL5] + Ethernet [AAL2] + Ethernet + TDM POTS/VF OLT ONT BAS

43 Data Transmission : DOWNSTREAM Standardized by ITU-T in G.984.x recommendation Communication between P-OLT and ONT Downstream : broadcast traffic – use encryption for security (AES) ?

44 Data Transmission : UPSTREAM ONTs are located at different distances from Central Office Upstream : same wavelength + same fiber Use Time Division Multiple Access (TDMA) How ? Distance OLT – ONT has to be measured Timeslots are allocated according to distance ONTs only send upstream according to granted timeslot

45 Distance ranging – Why? deliberately putting equalization delay in for the purpose of avoiding collisions

46 Distance ranging explained time distance Ranging_Grant() t1 t2 ? Δt Ranging_Grant_Ack(Δt) = (t2 – t1-Δt)/2 Assume this is 75 μs Cfiber = 200.000 km/s ? ? = 15km     

47 GPON frame format ATM-segment (option) downstream frame – 125 us GEM-segment upstream frame – 125 us ONU1 ONU2 ONU3 ONU4 ONU5 PCB GEM-packet ATM-cell

48 DOWNSTREAM : Continuous mode operation Downstream – there’s always a signal even when there’s no user data to pass through except when the laser is administratively turned of downstream frame

49 GPON frame format – Downstream ATM-segment (option) GEM-segment Psynch Ident PLOAMd BIP PLend PLend US BW Map Physical Control Block 4 bytes 4 bytes 13 bytes 4 bytes 4 bytes N*8 bytes 1 byte

50 GPON frame format – Downstream (cont.) Psynch Ident PLOAMd BIP PLend PLend US BW Map Physical Control Block N*8 bytes … AllocID Flag SStart SStop CRC 12 bits 12 bits 2 bytes 2 bytes 1 byte Entry for ONT#1 Entry for ONT#N

51 GPON frame format – Downstream (cont.) US BW Map 3 entries upstream packet timing 75 240 280 400 430 550 slot times: time

52 UPSTREAM : Burst mode operation Upstream – there’s only a signal when an ONT needs to send when no ONT has info to send, there’s no light on the fiber at all between 2 consecutive bursts, a guard time is needed: 26 ns upstream frame Rx Tx burst mode Rx burst mode Tx

53 GPON frame format – Upstream ONU1 ONU2 ONU3 ONU4 ONU5 Header Payload PLOu PLOAMu DBRu Physical layer overhead Physical layer OAM Dynamic bandwidth report

54 GEM = GPON Encapsulation Method GEM allows for point-to-point emulation payload fragmentation (efficiency) GEM allows native TDM transport E1/T1, E3/T3 raw format 12 bits 13 bits 12 bits 3 bits TDM GEM header GEM encapsulation payload CRC PTI PortID PLI L bytes

55 PON standardization 3

56 ITU-T standards for GPON G.984.1 – GPON service requirements specifies line rate configurations and service capabilities G.984.2 – GPON physical medium specifies transceiver characteristics per line rate and per ODN class including burst overhead for each upstream line rate G.984.3 – GPON transmission convergence specifies transmission convergence protocol, physical layer OAM, ranging mechanism G.984.4 – GPON ONT management control interface based on OMCI for BPON, taking GPONs packet mode into account phased approach to achieve interop (FSAN) Alcatel-Lucent was the first GPON supplier to disclose its OMCI implementation details

57 OMCI – ONT Management Control Interface a method to manage ONTs from the OLT this includes configuration, fault and performance management each ONT and the OLT has it’s own OMCI channel bandwidth is allocated at PON creation time protocol? the OMCI protocol

58 ITU-T G.984.x framework Ethernet TC adaptation sublayer Framing sublayer PON-PHY C/M application PLOAM OMCI Voice/Data/Video Embedded OAM … … G.984.3 GTC G.984.2 PMD G.984.1 General characteristics G.984.4 OMCI

59 Redundancy ITU-T G.984.1 specifies 3 types of redundancy between OLT and ONT Type A : spare fiber, no additional LTs or ONTs Type B : redundancy to the splitter : redundant LTs and feeder fibers to the first splitter Type C: redundancy through the entire path: redundant LTs, fibers, splitters, ONTs ** Separate geographical paths required for two feeders to avoid simultaneous fiber cuts **

60 PON Feeder Redundancy Alcatel-Lucent currently implements partial Type B redundancy (Type B-) 1+1 redundant feeder fibers from the LT PON to the optical splitter Fiber-only protection: redundant fiber can be used in case the other one fails ** Separate geographical paths required for two feeders to avoid simultaneous fiber cuts ** No redundant LTs - no protection against HW & SW failures on the LT Reduces LT capacity by 50% protection

61 www.alcatel-lucent.com www.alcatel-lucent.com

62 Considerations A

63 Trends towards next generation PON GPON enhancements - wavelength blocking filter - optical parameter monitoring - midspan extender box - Class C++ optics - OTDR integration WDM-PON - TDM PON per wavelength - wavelength per customer - dynamic wavelength switching - low cost WDM optics Migration GPON  NG-PON on same ODN - capacity increase by wavelength stacking - coexistence via electrical modulation multiplexing - 10G coexistence via WDM overlay time today near future (5 years from now ?) far future (10 years from now ??)

64 Status of ongoing standards activities on NG-PON : FSAN / ITU-T GPON enhancements amendments on wavelength spces : G.984.5 (new) optical parameter monitoring : G.984.2 Amnd. 2 (new) midspan extender box : G.984.re (draft) OTDR integration : input from ALU planned for 2H2008 White Paper on NG-PON migration: due mid 2009 NGN1: coexistence scenarios NGN2: disruptive approaches Physical layer specs of pure 10G solution are expected to be similar to 10G-EPON PHY specs (wavelength, ODN loss budget, Tx power, Rx sensitivity)

65 PON Evolution B

66 Pushing the envelope of PON now Moving up Capacity, Reach & Split GPON C+ GPON mid-span extender GPON B+ XG-PON 1,2 DS: 10G US: 2.5, 5, 10G WDM overlay in enhancement band NGA 1 GPON DWDM OFDM, CDM NGA 2 Capacity 2010 >2010 Lab today 2011-2012 Demo Oct 09 Coexistence Preservation of OSP (power splitters) Will likely require change in OSP

67 Readiness for Next Generation PON: It is all about Capacity, Reach & Split Less dense areas addressed and central office consolidation GPON B+ Today GPON C+ 2009 Extended GPON 2009 10 Gb/s PON 2010-2011 Extended 10 Gb/s PON 1 2 3 More bandwidth for FTTB and backhaul Increased split ratio More bandwidth and symmetry per subscriber RE RE

68 68 | Presentation Title | Month 2008 Upgrade for 10G GPON Wavelength overlay in both uplink and downlink GPON 10 Gb/s GPON No changes to OSP, including fiber and splitter 10 Gb/s on different wavelengths (up and down) WDM to split GPON from 10 Gb/s GPON GPON 10 Gb/s GPON

69 G.984.5 overview C

70 ITU-T G.984.5 for co-existence of future PON technologies Purpose: define wavelength ranges for additional service signal to be overlaid via WDM Reserved bands are referred to as the “enhancement band” (EB) Applications for the EB include video and NGA services Wavelengths in the EB may be used for downstream as well as upstream services 1260 1360 1340 1320 1300 1280 UP 1460 1440 1420 1400 1380 Reserved 1520 1480 1500 1540 1560 DOWN Basic band 1580 (1625) Enhancement band (option 1-1: 1415-1450 nm – non-low-waterpeak fibers) (option 1-2: 1400-1450 nm – low-waterpeak fibers) Enhancement band (option 2: 1530-1580 or 1625 nm (option 3: 1550-1560 nm – video distribution) Guard band for US Guard band for DS Guard band for DS

71 ITU-T G.984.5 for co-existence of future PON technologies Wavelength Blocking Filter (WBF) for ONT to minimize effect of interference signals from NGA wavelengths WBF is used to obtain the required isolation outside of the guard band G.984.5 specifies the “X/S” tolerance mask, where X= optical power of interference signal at ONT I/f and S= optical power of Basic Band signal λ3 λ6

72 ITU-T G.984.5: reference diagram Splitter WDM1 GPON/NGA GPON/(Video) coupler GPON OLT Video-OLT NGA ONT … NGA OLT GPON ONT (could be replaced by 3:N splitter) TX WDM (NGA) RX TX WDM (NGA) RX WBF TX WDM (NGA) RX WBF RX-V WBF-V (NGA) ONT (NGA) ONT + RF video TX = Optical Transmitter RX = Optical Receiver V-RX – Video Receiver WBF-V = WBF for blocking the inter-ference to V-RX WDM (NGA) = WDM filter in ONT/OLT to combine/isolate wavelengths of (NGA) GPON upstream/downstream (and isolate video signal) WDM1 = WDM filter (in CO) to combine/isolate the wavelengths of (NGA) GPON (and combine the video signals)