The document provides an overview of Passive Optical Networking (PON) and GPON fundamentals. It begins with the objectives of the course and describes the basic components and properties of a PON network, including optical fibers, splitters, transmitters, receivers, and wavelength usage. It then focuses on GPON specifics such as downstream and upstream data transmission using time-division multiple access, the 125us frame format, and how bandwidth allocation maps are used to assign timeslots to different ONTs.

1. PON
Passive Optical Networking

2. 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. 3
Table of Contents
1. Optical fiber fundamentals
2. GPON fundamentals
3. PON standardisation

4. 4
Optical Fiber Fundamentals
1

5. 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. 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. 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. 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 um125 um
Cladding
Core
Coating
245 um

9. 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. 10
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
Electron is disturbed and reaches a
higher energy level : energy is lost
= absorption
ray of light

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

12. 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)
1.7
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
band
1,30
band
1,55
band
0.0

13. 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
Tx RxAmplifier
Electrical ElectricalOptical Optical

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

15. 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. 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 dB0.3 dB
0.1 dB 0.1 dB 0.1 dB 0.1 dB 0.1 dB

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

18. 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. 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
Shouldn’t be mixed

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

21. 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. 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
λ1
λ1
λ1
λ2
λ2
λ3
λ3
3.5 dB
insertion loss

23. 23
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
0.3 dB loss
λ1
λ2
λ1
λ2
insertion loss

24. 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. 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. 26
GPON fundamentals
2

27. 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. 28
Definition - Feeders, Distribution, Drops
Access Point
Feeders
(primary)
Distribution
(secondary)
DropsPOP
Active
Active
Passive

29. 29
PON properties
PON – Passive Optical Network
• passive components
o splitters + WDM-device
• star topology
o 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. 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
Line rate flexibility
2500 Mb/s
1250 Mb/s
V-OLT
P-OLT

31. 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. 32
Splitters – Example
Available in various splice
trays and terminals
Available with factory
terminated pigtails
CONNECTORISEDSPLICED
-- Flexible
-- Patch cords included
-- Easy to replace
-- Cheap
-- Maintenance free
-- Skilled technician
3M3M

33. 33
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
PON
Distance depends on loss in different components:

34. 34
Splitter – Optical Budget
Example:
Splitter 1 x 8
Input
Fiber
Output
Fiber
3.5dB
3.5dB
3.5dB
Optical Splitters Loss [dB]
Splitter 1 x 64 20.1
Splitter 1 x 32 17.4
Splitter 1 x 16 13.8
Splitter 1 x 8 10.5
Splitter 1 x 4 7.0

35. 35
Data transceiver specifications (class B+)
+5.0
P (dBm)
+1.5
+5.0
P (dBm)
+0.5
-8.0
P (dBm)
-27.0
-8.0
P (dBm)
-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. 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:
o 0.30 dB/km – downstream
o 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. 37
Data transceiver specifications (class C+)
+7.0
P (dBm)
+3.0
+5.0
P (dBm)
+0.5
-8.0
P (dBm)
-30.0
(**)
-12.0
P (dBm)
-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. 38
Video transceiver specifications
+18.5
P (dBm) P (dBm)
-4.9
1550 nm
Downstream budget:
+18.5 – (-4.9) = 23.4 dB
Tx level
Rx level

39. 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:
o 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. 40
Eric
Maximum range per splitter - configuration
1:64
1:8
1:16
1:32
38 km
30 km
21 km
14 km
1:2
1:4
splitting best
case
worst
case
1 : 64 14 km 10 km
1 : 32 21 km 15 km
1 : 16 30 km 23 km
1 : 8 38 km 30 km
ITU-T G.984
Standard
B+ Laser

41. 41
GPON protocol layers and formats
GEM – GPON Encapsulation Method
• Ethernet + TDM
ATM – Asynchronous Transfer Mode
VG
optical (TDM/TDMA)
Ethernet[AAL5] + Ethernet
[AAL2] + Ethernet + TDM POTS/VF
OLT
ONT
BAS

42. 42
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. 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. 44
Distance ranging – Why?
deliberately putting equalization delay in
for the purpose of avoiding collisions
20 km
20 km
15 km

45. 45
Distance ranging explained
time
distance
t1
t2
?
t
= (t2 – t1- t)/2
Assume this is 75 µs
Cfiber = 200.000 km/s
?
? = 15km

46. 46
GPON frame format
ATM-segment (option)
downstream frame – 125 us
GEM-segment
upstream frame – 125 us
ONU1 ONU2 ONU3 ONU4 ONU5
PCB GEM-packetATM-cell

47. 47
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
Tx Rx
continuous mode Tx continuous mode Rx

48. 48
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

49. 49
GPON frame format – Downstream (cont.)
Psynch Ident PLOAMd BIP PLend PLend US BW Map
Physical Control Block
N*8 bytes
… AllocID … CRCAllocID Flag SStart SStop CRC
12 bits 12 bits 2 bytes 2 bytes 1 byte
Entry for ONT#1 Entry for ONT#N

50. 50
GPON frame format – Downstream (cont.)
US BW Map
3 entries
ONT1 slot 75 slot 240
AllocID Start Stop
ONT2 slot 280 slot 400
AllocID Start Stop
ONT3 slot 430 slot 550
AllocID Start Stop
upstream packet timing
guard timeguard time
75 240 280 400 430 550slot times: time

51. 51
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

52. 52
GPON frame format – Upstream
ONU1 ONU2 ONU3 ONU4 ONU5
Header Payload
PLOu PLOAMu DBRu
Physical
layer
overhead
Physical
layer
OAM
Dynamic
bandwidth
report

53. 53
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 bits12 bits 3 bits
TDM
Ethernet PayloadMACDA MACSA
Type/
Length
FCS
GEM header
GEM encapsulation
payload
L bytes
payloadCRCPTIPortIDPLI
L bytes

54. 54
PON standardization
3

55. 55
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. 56
PON
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

57. 57
ITU-T G.984.x framework
Ethernet
TC adaptation sublayer
Framing sublayer
PON-PHY
C/M application
PLOAMOMCI
Voice/Data/Video
Embedded OAM
…
…
G.984.3 GTC
G.984.2 PMD
G.984.1 General characteristics
G.984.4 OMCI

58. 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. 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%
protection
PON 1
PON 2
2:N splitter
LT

60. 60
www.alcatel-lucent.comwww.alcatel-lucent.com

61. 61
Considerations
A

62. 62
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 ??)

63. 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 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)

64. 64
PON Evolution
B

65. 65
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

66. 66
Readiness for Next Generation PON:
It is all about Capacity, Reach & Split
Less dense areas addressed and central office consolidation
10
Gb/s
2.5
Gb/s
Reach 20km 30 km 60 km
Split 32 64 128
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

67. 6767 | 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
1260
-1280
1290
-1330
1480
-1500
1550
-1560
1575
-1580
λλλλ
(in nm)
GPON up GPON downXGPON up XGPON downCATV
GPON
10 Gb/s
GPON

68. 68
G.984.5 overview
C

69. 69
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 13601340132013001280
UP
14601440142014001380
Reserved
15201480 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

70. 70
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
14601440 15201480 1500 1540
Basic Band
Guard band for DS Guard band for DS
14601440 15201480 1500 1540
Basic Band
X/S (dB)
y2
y1
λ4’
λ4
Λ5’
λ5

71. 71
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)
RXWBF
TX
WDM
(NGA)
RXWBF
RX-VWBF-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)