1. An Overview of PON Technologies
Pu-Chen Mao
3/21/2011

2. Outline
Background
G-PON
EPON
NG-PON
Future Studies
References

3. Background (1/3) Access technologies Wireless Copper
802.11, , etc.
Low cost deployment
Insufficient capacity for high bandwidth (revenue) applications such as IPTV
Copper
DSL
Point-to-point architecture allows unshared bandwidth
Limited distance due to noise
Cost of deployment only slightly less than an all-fiber approach

4. Background (2/3) Fiber Low noise Long reach Topology Tree
More cost effective
Point-to-point
Dedicated fiber plant from CO to subscriber
Ring
Fault tolerant

5. Background (3/3) Shared fiber architectures Active Ethernet PON
Signals split by electronic equipment
PON
Signals replicated passively by splitter
Higher reliability due to no electronic equipment in outside plant
Signal format transparency
Can be more flexibly upgraded
Requires no electric power source

6. G-PON
Specified by ITU-T G.984 series
Began in FSAN consortium in 2001

7. G-PON Layers

8. G-PON Transmission Convergence (GTC) Layer
Performs adaptation to the physical-medium-dependent (PMD) layer
Adaption methods
ATM
G-PON encapsulation method (GEM)
Preferred method
Ethernet adaptation
TDM adaptation
MAC function
Coordinates interleaving upstream traffic from individual ONUs

9. GTC Layer Control functions
Defines protocols & procedures for registering & performance monitoring of ONUs
Configuration of transport features
FEC
Encryption
Bandwidth allocation

10. GTC Layer GTC framing sub-layer Downstream frame format 125 us
8 KHz signal for ONU reference clock
Physical Control Block (PCBd)
Framing, PHY operations, PLOAM fields
Message-based protocol for PMD & GTC mgmt.
Bandwidth map field for upstream transmission allocation
Payload follows PCBd

11. GTC Layer GTC framing sub-layer Upstream frame format
Same as downstream 125 us
Physical layer overhead (PLOu) field
Preamble & delimiter configurable by OLT
Dynamic bandwidth report (DBRu) field for DBA traffic queuing reports from ONUs
PLOAM identical to downstream frame
DBRu & PLOAM are optional, requested by OLT

12. GTC Layer GTC TC adaption sub-layer GEM
Protocol independent connection-oriented encapsulation for variable-sized packets
Virtual connection unit: GEM port
5 byte header
Port ID & frame size
Frames may be fragmented
G.984 specifies transport of Ethernet & TDM over GEM

13. GTC Layer
T-cont
Each T-cont aggregates one type of traffic out of 5 classes
Composed of multiple virtual port connections

14. Upstream Bandwidth Allocation
Static method
Dynamic Method (DBA)
Status reporting DBA
ONU reports via DBRu field
Non-status reporting DBA
T-cont utilization monitored by OLT

15. GTC Control Plane Operated via PLOAM message protocol and embedded OAM
Management functions
PMD layer management
Upstream config, PHY monitoring, generate stats
GTC layer management
Framing, requesting PLOAM / DBRu, etc.
ONU activation
Activate ONU, ranging protocol, optical power tuning
Encryption management
AES, key exchange procedure

16. G-PON Management
G specifies the ONT management and control interface (OMCI)
OMCI
ONU management information base
ONT mgmt. control channel protocol (OMCC)
Conveys MIB info between ONU & OLT
Models equipment configuration, port types, and service types
QoS

17. EPON
Ethernet sub-layers

18. EPON 1 Gb/s bidirectional links 1490 nm downstream 1310 nm upstream
1550 nm reserved for extensions
802.3ah EPON
Minimum 1:16 split ratio
Up to 1:64 commercially available
802.3 similarities
Standard inter frame gap (IPG)
Uses same MAC
Multi-Point Control Protocol (MPCP) for P2MP connectivity
Uses standard Ethernet packets in MAC sub-layer
Modified preamble

19. EPON Downstream

20. EPON Upstream

21. EPON ONU Registration MPCP handshake OLT broadcasts GATE message
Unregistered ONUs respond with REPORT and REGISTER_REQ
OLT approves and replies with REGISTER
ONU responds with REGISTER_ACK

22. EPON Operation
OLT controls ONU transmission windows with GATE messages
ONU responds queue status with REPORT
OLT calculates transmission window length using DBA
Synchronized to PON clock with 16 ns resolution counter in MPCP messages
OLT and ONU exchange timestamps to measure RTT for upstream scheduling

23. EPON Frame Downstream preamble Upstream preamble FEC Encryption
Logical link ID field specifies the destination ONU
ONU filters frames by LLID
ONU receives unique LLID assigned by OLT
Special value of LLID reserved for broadcast
Upstream preamble
LLID marks the source ONU
Ensure preamble field integrity by CRC
One ONU may have multiple LLIDs (virtual ONU)
FEC
Based on RS(255,239)
Frames encoded separately, parity bytes appended to end
Encryption
AES-based

24. EPON Management Link layer management OAM OAM using SNMP
OLT remotely manages attached ONUs
Remote link monitoring
OAM
Established after discovery process
Maintained by periodic messages
Remote failures conveyed in flags of OAM msgs.
OAM using SNMP

25. NG-PON
Next-generation PON technologies to extend current bandwidth to 10 Gb/s
XG-PON by ITU-T
10GE-PON by IEEE 802.3av

26. NG-PON Direction

27. 10 Gb/s PON

28. 10 Gb/s PONs Similarities of XG-PON & 10GE-PON
L-band downstream 1575 – 1580 nm
O-minus band upstream 1260 – 1280
Mandatory FEC
RS(255, 223)
Video overlay 1550 – 1560 nm

29. 10 Gb/s PONs Uniqueness 10GE-PON XG-PON
Conflict in EPON 1260 – 1360 nm and 1260 – 1280 nm band used
Share overlapping spectrum using TDMA
XG-PON
32-bit word aligned framing
XGEM extension
PLOAM, DBRu, bandwidth allocation, ranging functions as clients to XGEM system, with XGEM becoming the main protocol

30. Future Studies
System architecture, specifications of XG-PON and 10GE-PON
Long-reach PON
DBA comparison for EPON, GPON, and next-generation PON

31. References
[1] Effenberger, F., et al., “An introduction to PON technologies,” IEEE Communications Magazine, Vol. 45, Issue: 3, 2007 [2] Effenberger, F., et al., “Standardization trends and prospective views on the next generation of broadband optical access systems,” IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010 [3] Paul E. Green Jr., “Fiber to The Home: The New Empowerment”, Wiley, 2006