Recent Developments in PON Systems
Standards in ITU-T
Dave Faulkner
Q2/15 Rapporteur
dave.faulkner@bt.com
Contents
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The Role of the ITU in Standardization
ITU-PON Access System
Fixed Access Timelines
Fiber Access Systems
B-PON
G-PON
Recent Updates to B-PON and G-PON standards
Outlook
Conclusions
The Role of the ITU in Standardization
• The International Telecommunication Union (www.itu.int),
– headquartered in Geneva, Switzerland,
– within United Nations System
– governments and the private sector members coordinate global
telecom networks and services.
– ITU-T Recommendations, such as G.982 (PON), G.983.x (BroadbandPON) and G.984.x (Gigabit-PON) are agreed by consensus and
provide a framework for the implementation.
– Question 2 on “Optical systems for fiber access networks” is the focus
of activity for PON systems in the ITU
• From an operator's perspective, cost reduction is the key
motivator for standards
– Interoperability and second sourcing are also important for a de-risking
the investment.
• From a vendor's perspective it is the assurance that
products will satisfy the needs of a world-wide market.
ITU-PON Access System
Fixed Access Timelines
Fixed
Access Timelines
1.00E+07
10G
1.00E+06
1G
kbit/s
1.00E+05
100M
1.00E+04
Bit 10M
Rate
1M
1.00E+03
Investment/loss Region.
10 GBE
Early introduction
1 GBE
Of competitive
10 G-PON
technology
G-PON
100 M VDSL2 DP
for premium
20 M VDSL2 Cab
services
18 M ADSL2plus
8M ADSL
WDM/PON
WDM/PON
VDSL Plateau?
ADSL Plateau?
Profitable Region
“Cash Cow”
Technology ‘uncompetitive’
Migration to new technology
or loss of market share
100k
1.00E+02
56k modem
10k
1.00E+01
1k
1.00E+00
1990
1995
2000
2005
2010
2015
Year
Source: “Next generation Broadband in Europe: The Need for Speed” Heavy
Reading Report, Vol. 3 No 5 March 2005
See Notes
2020
Fiber Access SystemsBT Perspective
• Fiber to the premises (P2P, from CO)
–
–
–
–
Existing deployment for businesses over 3km and 2 Mbit/s
Incremental deployment has high cost and long ‘lead’ times
Churn leads to stranded assets
Duct network insufficient for ubiquitous coverage
• While copper stays in place
• Fiber to the cabinet/VDSL2
–
–
–
–
In BT trials
Reuse of copper offers lower CapEx than FTTP
OpEx costs under investigation in trials
Capacity is reach dependent
• Subtended MSANs or Fiber could solve this
• CO fed fibers are most likely to be used
• Fiber to the premises (PON)
– G-PON (e.g. 2.4/1.2 Gbit/s), favoured for limited use in 21CN
– Lower CapEx and OpEx than (P2P) if deployed over whole areas
– PON/OLT can act as a traffic concentrator (QoS, possible)
Active Optical Networks (P2P from COs/Cabs)
- an alternative to PON
• AONs deployed in parts of Europe by CLECs, approx
500k subscribers
• P2P can give more capacity than shared access systems
– Better future-proofing
• Upgrades
– Only affect one customer
– Require no changes to external plant
• Shared access systems seem to date quickly
– E.g. Cable systems are difficult to upgrade, outside plant needs changing
– Shared access not needed with SDV (no broadcasting needed now)
• Service and Network Management is a concern for
operators/standards
– Except SDH when used for direct connection to customers
– G.985 adds limited network management functionality to Ethernet over fiber
B-PON
• Broadband passive optical network
–
–
–
based upon 53 byte ATM cells with mini-cells in transmission
convergence (TC) layer
Downstream ‘grants’ control the sending of upstream cells
Rates up to 620 Mbit/s symmetrical
•
and 1240/622 asymmetrical have been standardised
• Transport capability
–
–
–
native ATM
TDM (T1/E1) by circuit emulation
Ethernet by emulation
• Business or home
– 32 way split (some systems 64 way)
– multi-casting possible
• Standardised in G983.x series in ITU
Business Drivers for PON
Business
factors
Economical and
reliable products
Competition
with CATV
providers
Competition
with CLEC’s
ADSL
Competition with
Long Haul
operators
B-PON Requirements
ITU-T
Recommendation
International standards compliances and
multi-vendor interoperability
G.983.1
G.983.2
Video signal overlay with 3-waves
multiplexing
G.983.3
G.983.3amend1
DBA (Dynamic Bandwidth Assignment) to G.983.4
improve transmission efficiency of
G.983.7
upstream signals
Access line protection and survivability
G.983.5
G.983.6
Enhanced OMCI (ONT Management and
Control Interface) for new services
G.983.2amemd2
Adding 622Mb/s upstream
Adding 1.2Gb/s downstream and security
G.983.1amend1
G.983.1amend2
Broadband PON Frame Format
Downstream Frame = 56 cells of 53 bytes
PLOAM ATM
Cell 1 Cell 1
ATM PLOAM ATM
Cell 27 Cell 2 Cell 27
ATM
Cell 54
Physical layer operations and maintenance (PLOAM) cells
give grants to upstream ONUs.
Maximum rate of 1/100ms. Each contains 27 grants
Upstream Frame = 53 cells per frame (aligned by ranging)
ATM
Cell 1
ATM
Cell 2
ATM
Cell 3
3 overhead bytes for guard time, preamble and delimiter
ATM
Cell 53
ONU Management and Control Interface
• A management channel between OLT and
ONU
– Part of the baseband signal
– Carried in the PLOAM cells
• Physical layer operations and maintenance
– Accessible by the Network Operator via the element
manager on the OLT
– Allows the PON and services to be configured and
managed
• Authentication, configuration and fault mangnet
• Service management POTS, Video on demand,
WLAN,VLAN, Ethernet
– etc
Dynamic Bandwidth Allocation
• A powerful conditional access mechanism
– allows queues at the customer-ends of the PON to
be served according to the priority assigned to the
traffic flow
– ranging from TDM circuit emulation through to best
effort (using spare capacity).
– also offers 'concentration on the fly',
• statistical gain for packet-based services
– likely to become increasingly important as users of IP
begin to expect QoS-based services on congested
networks
• Allows bursts close to the maximum PON rate
• Good for high speed packet transmission
B-PON Interoperability Events
Where
When
Host
Functionality
Makuhari,
Japan
March 9-11, NTT/FSAN meeting TC layer with Ethernet
2004
Geneva,
Switzerland
June 2-4,
2004
ITU ‘All Star
Workshop’
TC Layer with Ethernet
San Ramon,
CA, USA
Sept 27,
2004
SBC/FSAN
meeting
TC Layer with Ethernet
Voice and fax services via
GR-303
Chicago, USA
June 7-9,
2005
TIA/ITU,
SUPERCOMM
TC Layer with Ethernet
Voice service via GR-303
H-D IPTV and optical RF
Video
G.983.3 Enhancement Band
• Downstream bands for B-PON
–
1490 (basic band) , 1550 (enhancement band)
• New laser was required for 1480-1500 nm band
• Enhanced services in 1539-1565 nm band
–
e.g. for broadcast services
• 1260-1360 nm upstream band retained
• Blocking filters and/or triplexer needed for ONT’s
– To receive additional service wavelength(s)
– e.g.
1480
Receive
1500
1539 1550
-1.5
Accept
-20
Reject
-30 dBm
1565
ITU-PON Showcase at SUPERCOMM
G-PON
• Gigabit Passive Optical Networks
– Higher capacities possible than B-PON
– More efficient transmission of IP/Ethernet Cells
– Same Optical Distribution Network
Service Requirements for G-PON.
Items
Target descriptions
Services and QoS Full Services
performances
(e.g. 10/100Base-T, Voice, Leased lines)
Bit rates
1.25Gb/s symmetric and higher
Asymmetric with 155Mb/s & 622Mb/s upstream
Physical reach
Max 20 km and Max 10 km
Logical reach
Max 60 km (for ranging protocol)
Max 64 in physical layer
Max 128 in TC layer
Branches
Wavelength
allocation
Downstream: 1480 – 1500nm (Video overlay is
Upstream:
1260 – 1360nm considered.)
ODN classes
Class A, B and C; same as B-PON requirements
Physical Layer Specifications for G-PON
Item
Specification
1.244Gbit/s and 2.488Gbit/s symmetric
2.4/1.2Gbit/s emerging as most popular rates
Bit rates
155.52Mbit/s and 622.04Mbit/s only for upstream
Error rate: Better than 1.0E-10
Dispersion and Up to 10km : FP-LD without FEC
error correction Up to 20km : DFB-LD or FP-LD with FEC
Optical device LD*1 + PIN (APD*2 is available)
Upstream
12Bytes (1.244Gbit/s), 24Bytes (2.488Gbit/s)
Overhead
Key Differences Between Gigabit- PONs
Item
MAC
Layer
PHY
Layer
FSAN / ITU-T G-PON
IEEE GE-PON
Service
Full services (Ether, TDM, POTS)
Ethernet data
Frame
GEM frame
Ethernet frame
Distance
10 / 20 km (Logical: 60 km)
10 / 20 km
Branches
64 (Logical: 128)
16 or over
Bit rate
Up : 155M, 622M, 1.25Gbit/s
Down : 1.25G, 2.5Gbit/s
1.25Gbit/s (Up and Down)
Bandwidth
Same as above (NRZ coding)
1Gbit/s (8B10B coding)
Opt. Loss
15 / 20 / 25dB
15 / 20dB
Wave-length
Down : 1480-1500nm
Up : 1260-1360nm
Same
(Available to video signals overlay)
Upstream
burst timing
Guard : 25.6ns
Preamble : 35.2ns (Typical)
Delimiter : 16.0ns (Typical)
Laser turn on / off :
512ns (Max)
AGC setting and CDR lock :
400ns (Max)
Recent Updates to B-PON standards
• Nov 2004
• G. 983.1 Revised. ‘Broadband Optical Access Systems Based On Passive
Optical Networks (PON)’
– Includes two previous Amendments, A Corrigendum, and Implementers’ guide
• G.983.2 Amendment 2, ‘B-PON ONT Management and Control Interface
(OMCI) support for Video Return Path’,
– Facilitates the use of set-top boxes originally designed for cable networks
• May 2005
• G.983.2 Revised ‘B-PON ONT Management and Control Interface (OMCI)’.
– All documents on OMCI have been merged into this revision, G.983.2 and G.983.6 through
to G.983.10 plus the Amendments 1 and 2 and Implementers’ guide.
– New functionality includes mechanized loop testing for telephony and ‘last gasp’ reporting
• G.983.3 Amendment 2, “A broadband optical access system with increased
service capability by wavelength allocation”
– Industry best practice optical budgets for the 622/155 B-PON system
•
•
28dB Optical Distribution Networks for B-PON
27dB with Analog video service
• G.983.1 Amendment 1 on Protocol Implementation Conformance Statements
(PICS) for the OLT and ONT.
– To show that the devices conform with G.983.1 at the transmission convergence layer
Recent Updates to G-PON standards
• May 2005
• G.984.3 Amendment 1 to G-PON Transmission Convergence
Layer.
– Peak Information Rate and Sustained Information Rate parameters are
now included and are analogous to ATM for alternative cell lengths
such as Ethernet packets.
– Multicast services may now be supported over GEM (e.g. IPTV).
– (GEM is the generic encapsulation mode use at in the transmission
convergence layer)
• G.984.4 Amendment 1 “Gigabit-capable Passive Optical
Networks (G-PON): ONT Management and Control Interface
specification”.
– Proposes management features on G-PON in support of Ethernet and
IPTV service such as the IEEE802.1p priority mapper, GEM traffic
descriptor, and support of multicast connection.
Outlook
• Capacity doubling every year!
– 1000-fold increase in 10 years.
– depends upon investment in new infrastructure,
– Varies between country, region and location
• Dependent on the economics and national strategy.
• Can the life of G-PON be extended?
– Bursting to 1Gbit/s could buy 3 years (to 2016)
• Upgrades
– With the addition of new wavelengths and/or new fiber
– Faster TDM-10Gbit/s
– WDM/PON
Conclusions
• The B-PON and G-PON series of standards are largely
complete
– B-PON has reached maturity with up to eight vendors with
interoperable OLT and/or ONU.
– The FSAN/Interoperability Task Group promotes standards
conformance and interoperability among vendors.
• Recommendations in the G.984.x series detail G-PON, the
latest generation of PON technology.
– Increasing capacity to Gigabit levels satisfies customer demands for
capacity in the range 100 Mbit/s (dedicated) and 1 Gbit/s (shared)
– G-PON maintains the same optical distribution network, wavelength
plan as B-PON
• offers more efficient IP and Ethernet handling
• Next step is G-PON interoperability
• The enhancement band is used by some operators to transport
analog cable TV
– In the future, as TV moves from RF-analogue to digital-in-band the
enhancement band is expected to be used for two-way interactive
digital services.