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, … § § describe the functions of the components present in a PON based network § 2 explain the basic properties of a passive optical network correctly use basic PON terminology
Table of Contents 1. Optical fiber fundamentals 2. GPON fundamentals 3. PON standardisation 3
1 4 Optical Fiber Fundamentals
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 5
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 6
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 7
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 245 um 125 um 8 – 62. 5 um Core 8 Cladding Coating
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 cladding acceptance cone core 9
Hit me baby one more time Atoms have a core with circling electrons o 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 ray of light Electron is disturbed and reaches a higher energy level : energy is lost = absorption 10
The world of wavelengths Light is transported as a wave. o The length of the wave determines the type of light (infrared, ultraviolet, …) 11
Attenuation as function of wavelength 2. 0 0, 85 µ band 1, 30 µ band 1, 55 µ band Attenuation (d. B/Km) 1. 8 1. 6 1. 4 1. 2 1. 0 0. 8 0. 6 0. 4 0. 2 0. 0 0. 8 0. 9 1. 0 1. 1 1. 2 1. 3 1. 4 Wavelength (microns) 12 1. 5 1. 6 1. 7 1. 8
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 Tx Electrical 13 Amplifier Optical Rx Optical Electrical
Transceiver Definition: • a transmitter and a receiver in a single housing Practical implementation: • transceivers typically come as SFP • Small-Form-factor Pluggable unit Tx Rx 14
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 15
Fiber interconnections permanent joint SPLICE 0. 3 d. B 0. 1 d. B Terminal A Terminal B CONNECTOR demountable joint Interconnect fibers in a low-loss manner • is a permanent bond needed ? – splice ! • is an easily demountable connection desired ? – connector ! 16
Joining fibers – Fiber alignment bad alignment good alignment • cores are not centered • big power loss 17 • cores are centered • small power loss
Joining fibers – Fiber orientation straight physical contact angular physical contact • lots of back reflection • some back reflection • (big) return loss • (small) return loss 18
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 Shouldn’t be mixed 19 Theoretical loss: 0. 3 d. B
Connectors - Couplers SC/UPC SC/APC Couplers 20 ST/APC
Joining fibers – Splices Fusion splicer 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 Theoretical loss: • using an electric arc 0. 1 d. B typical case used to enclose fiber optic splices in an outside plant environment 21
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 l 1 l 2 l 3 l 1 l 2 l 1 l 3 3. 5 d. B insertion loss 22
Optical wavelength splitters Wavelength Division Multiplexing … • enables the combining of … o multiple wavelengths o into one single fiber Depending on the design, an optical wavelength splitter … • typically provides … o a small to medium loss o to the signals passed through it l 1 l 2 0. 3 d. B loss insertion loss 23
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 24
PON deployment scenarios – FTTx FTTEx FTTCab ONU ADSL ( < 6 KM ) XNT < 8 Mbit/s Central Office OLT FTTH/B FTTC ONU ADSL/VDSL ( < 1 KM ) XNT < 26 Mbit/s Network ONU VDSL ( < 300 M ) < 52 Mbit/s XNT ONT 25
2 26 GPON fundamentals
Two Basic FTTH technologies Point-to-Point Customer Premises Equipment (CPE) Receive (P 2 P) Aggregation x 4 Transmit 1: 1 Point-to-Multi-Point used in GPON Upstream Optical Network Terminal (ONT) Splitter 1310 (P 2 MP) Optical Line Terminal (OLT) 1490 Downstream LESS SPACE, LESS FIBRES, LESS DUCT SIZE 27 1: 64 to 1: 128 Subscribers
Definition - Feeders, Distribution, Drops POP Feeders (primary) 3 Active 28 – 5 Distribution (secondary) m -3 k 2 km Passive Drops Access Point <100 m Active
PON properties PON – Passive Optical Network • passive components o splitters + WDM-device • star topology o p 2 mp – point to multipoint No Equipment Ranging distance • 60 km maximum logical reach • 20 km differential distance Split-ratio • Minimum 64 subscribers (or more) 29 PON No Power
PON lambdas Voice and data over a single fiber • two wavelengths in opposite directions Video • one wavelength in downstream direction P-OLT Data path 1490 nm 1310 nm Splitters 2500 Mb/s 1250 Mb/s Video path V-OLT 1550 nm Line rate flexibility 30
Splitter - Types Type 1: FBT – Fused Biconic Taper -Two fibers fused to create a split - Typical fusion of 2, 3 or 4 fibres - Splits in cascade 31 Type 2: PLC – Planar Lightwave Circuit - Built into glass waveguides - Solid state - No mechanical parts - Compact -Splits: 1 x 4, 1 x 8, 1 x 16, 1 x 32 -Splits: 2 x 4, 2 x 8, etc
Splitter – Size 3 M 32
Splitters – Example SPLICED CONNECTORISED -- Cheap -- Maintenance free -- Skilled technician -- Flexible -- Patch cords included -- Easy to replace 3 M Available in various splice trays and terminals 33 3 M Available with factory terminated pigtails
Optical power budget Distance depends on loss in different components: § 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 34 PON
Data transceiver specifications (class B+) P (d. B) +5. 0 +1. 5 – (-27) – (0. 5) = 28 d. B path penalty: 0. 5 d. B -8. 0 0. 30 d. B/km Tx level Downstream budget: 1490 nm +1. 5 -27. 0 Rx level P (d. B) Tx level Rx level 0. 42 d. B/km +0. 5 path penalty: 0. 5 d. B -8. 0 -28. 0 35 +5. 0 1310 nm Upstream budget: +0. 5 – (-28) – (0. 5) = 28 d. B
Optical power budget – Data Example: • budget: 28 d. B • 16 way splitter loss: 13. 8 d. B • connector+splicing loss: 3 d. B (theoretical. 12 d. B) (24*0. 1 d. B + 2*0. 3 d. B) • aging: 1 d. B • attenuation: o 0. 30 d. B/km – downstream o 0. 42 d. B/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 36
Data transceiver specifications (class C+) P (d. B) +7. 0 +3 – (-30) – (1) = 32 d. B path penalty: 1 d. B (*) -8. 0 0. 30 d. B/km Tx level Downstream budget: 1490 nm +3. 0 -30. 0 Rx level (**) P (d. B) Tx level Rx level 0. 42 d. B/km +0. 5 path penalty: 0. 5 d. B -12. 0 +5. 0 Upstream budget: +0. 5 – (-32) – (0. 5) = 32 d. B 1310 nm -32. 0 (*) Accounts for DS dispersion effects up to 60 km reach (**) ONT sensitivity in C+ mode with FEC 37
Video transceiver specifications P (d. B) +18. 5 Downstream budget: 1550 nm +18. 5 – (-4. 9) = 23. 4 Tx level 38 -4. 9 Rx level
Optical power budget – Video Example: • • • budget: 23. 4 d. B 16 way splitter loss: 13. 8 d. B (theoretical. 12 d. B) connector+splicing loss: 3 d. B (24*0. 1 d. B + 2*0. 3 d. B) aging: 1 d. B attenuation: o 0. 25 d. B/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 39
Splitter – Optical Budget Example: Splitter 1 x 8 3. 5 d. Bm Input Fiber 40 Output Fiber
Maximum range per splitter - configuration splitting ITU-T G. 984 Standard 20 km 14 km 1: 16 Eric 1: 2 1: 8 1: 4 30 km 38 km 41 10 km 21 km 15 km 1 : 16 1: 32 14 km 1 : 32 1: 64 worst case 1 : 64 21 km best case 30 km 23 km 1: 8 38 km 30 km
GPON protocol layers and formats GEM – GPON Encapsulation Method • Ethernet + TDM ATM – Asynchronous Transfer Mode [AAL 2] + Ethernet + TDM POTS/VF VG OLT BAS 42 optical (TDM/TDMA) [AAL 5] + Ethernet ONT Ethernet
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) 43
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 44
Distance ranging – Why? 20 km 15 km deliberately putting equalization delay in for the purpose of avoiding collisions 45
Distance ranging explained ? t 1 distance Rangi ng_ G ran Δt _G ing (Δ Ack _ ant r t) ? = (t 2 – t 1 -Δt)/2 Assume this is 75 μs Cfiber = 200. 000 km/s g Ran t 2 time 46 t () ? = 15 km
GPON frame format ATM-segment (option) GEM-segment downstream frame – 125 us ONU 1 ONU 2 ONU 3 ONU 4 ONU 5 upstream frame – 125 us PCB 47 ATM-cell GEM-packet
DOWNSTREAM : Continuous mode operation downstream frame Tx continuous mode Tx Rx continuous mode Rx Downstream – there’s always a signal • even when there’s no user data to pass through • except when the laser is administratively turned of 48
GPON frame format – Downstream ATM-segment (option) GEM-segment Physical Control Block Psynch Ident PLOAMd 4 bytes BIP 13 bytes 49 PLend US BW Map 4 bytes 1 byte PLend 4 bytes N*8 bytes
GPON frame format – Downstream (cont. ) Physical Control Block N*8 bytes Psynch Ident PLOAMd BIP PLend Alloc. ID Flag SStart SStop CRC 12 bits 2 bytes … US BW Map Alloc. ID … CRC 1 byte Entry for ONT#1 50 PLend Entry for ONT#N
GPON frame format – Downstream (cont. ) 3 entries US BW Map ONT 1 slot 75 slot 240 ONT 2 slot 280 slot 400 ONT 3 slot 430 slot 550 Alloc. ID Start Stop 550 time upstream packet timing slot times: 75 51 guard time 240 280 400 430
UPSTREAM : Burst mode operation upstream frame Rx burst mode Rx Tx burst mode Tx 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 52
GPON frame format – Upstream ONU 1 ONU 2 ONU 3 Header ONU 4 Payload PLOu DBRu Physical layer overhead 53 PLOAMu Physical layer OAM Dynamic bandwidth report ONU 5
GEM encapsulation GEM = GPON Encapsulation Method TDM GEM header PLI Port. ID PTI CRC payload L bytes 12 bits 3 bits 13 bits L bytes GEM allows for MACDA MACSA • point-to-point emulation • payload fragmentation (efficiency) GEM allows native TDM transport • E 1/T 1, E 3/T 3 raw format 54 Type/ Length Ethernet Payload FCS
3 55 PON standardization
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 56
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 PON 57
ITU-T G. 984. x framework Voice/Data/Video C/M application … … Ethernet G. 984. 4 OMCI PLOAM G. 984. 3 GTC TC adaptation sublayer Embedded OAM Framing sublayer PON-PHY G. 984. 2 PMD G. 984. 1 General characteristics 58
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 ** 59
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% 2: N splitter PON 1 LT PON 2 protection 60
www. alcatel-lucent. com 61
A 62 Considerations
Trends towards next generation PON near future today (5 years from now ? ) far future (10 years from now ? ? ) time 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 - 10 G coexistence via WDM overlay 63
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 2 H 2008 § White Paper on NG-PON migration: due mid 2009 • NGN 1: coexistence scenarios • NGN 2: disruptive approaches § Physical layer specs of pure 10 G solution are expected to be similar to 10 G-EPON PHY specs (wavelength, ODN loss budget, Tx power, Rx sensitivity) 64
B 65 PON Evolution
Pushing the envelope of PON now Moving up Capacity, Reach & Split Capacity NGA 2 DWDM OFDM, CDM 2011 -2012 Demo Oct 09 NGA 1 XG-PON 1, 2 DS: 10 G US: 2. 5, 5, 10 G 2010 WDM overlay in enhancement band GPON C+ GPON B+ GPON 66 Will likely require change in OSP GPON mid-span extender >2010 Lab today § Coexistence § Preservation of OSP (power splitters)
Readiness for Next Generation PON: It is all about Capacity, Reach & Split 1 Extended 10 Gb/s PON 2010 -2011 § More bandwidth for FTTB and backhaul Gb/s RE § Increased split ratio 2. 5 RE § More bandwidth and symmetry per subscriber 10 Gb/s GPON B+ Today Reach Split 2 GPON C+ 2009 3 Extended GPON 2009 20 km 30 km 60 km 32 64 128 Less dense areas addressed and central office consolidation 67
Upgrade for 10 G GPON WDM to split GPON from 10 Gb/s GPON Wavelength overlay in both uplink and downlink No changes to OSP, including fiber and splitter GPON 10 Gb/s on different wavelengths (up and down) XGPON up GPON down CATV 1260 -1280 1290 -1330 1480 -1500 1550 -1560 68 | Presentation Title | Month 2008 XGPON down 1575 -1580 (in nm)
C 69 G. 984. 5 overview
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 à Reserved bands are referred to as the “enhancement band” (EB) à Applications for the EB include video and NGA services à Wavelengths in the EB may be used for downstream as well as upstream services Guard band for US UP 1260 1280 1300 Guard band for DS Reserved 1320 1340 1360 1380 1400 1420 Guard band for DS DOWN 1440 1460 1480 1500 1520 1540 1560 1580 (1625) Basic band Enhancement band (option 1 -1: 1415 -1450 nm – non-low-waterpeak fibers) (option 1 -2: 1400 -1450 nm – low-waterpeak fibers) 70 Enhancement band (option 2: 1530 -1580 or 1625 nm (option 3: 1550 -1560 nm – video distribution)
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 à WBF is used to obtain the required isolation outside of the guard band à 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 Guard band for DS Basic Band 1440 1460 1480 1500 1520 1540 X/S (d. B) λ 3 y 2 λ 4’ Λ 5’ λ 5 y 1 λ 4 Basic Band 1440 71 1460 1480 1500 1520 1540 λ 6
ITU-T G. 984. 5: reference diagram GPON OLT NGA ONT Splitter NGA OLT … WDM 1 GPON/NGA GPON/(Video) coupler (could be replaced by 3: N splitter) GPON ONT Video-OLT RX TX 72 WDM (NGA) TX = Optical Transmitter RX = Optical Receiver V-RX – Video Receiver WBF-V = WBF for blocking the interference to V-RX WDM (NGA) = WDM filter in ONT/OLT to combine/isolate wavelengths of (NGA) GPON upstream/downstream (and isolate video signal) WDM 1 = WDM filter (in CO) to combine/isolate the wavelengths of (NGA) GPON (and combine the video signals) WDM (NGA) WBF (NGA) ONT TX WBF WDM (NGA) RX RX WBF-V RX-V TX (NGA) ONT + RF video
Скачать презентацию PON Passive Optical Networking Objective At the
TAC03049-HO09-I1 7-GPON_Tech.ppt