(Continuation of Questions 16 and 19/15)
Background and justification
Fibre optic networks are being deployed at accelerated rates in
telecommunication systems worldwide. Structural reforms leading to
increased privatization of telecommunications networks create an
operating environment requiring optical networking and
interconnection among different carriers. Simultaneously, there is
occurring a rapid evolution toward a packet-based (IP type)
infrastructure supporting integrated, multi-service networks in
both metropolitan and backbone environments. These developments
are being fuelled by customer demand for ever higher bit rates
data services, high-speed Internet access, and other innovative
services. It leads to a push for higher bit-rate (Terabit/s)
optical transport systems in the intra-office, inter-office and
long distance networks of the various network operators.
Along with the continuation of the plesiochronous digital
hierarchy (PDH) in some networks and the increasing use of the
synchronous digital hierarchy (SDH) worldwide, there is now an
interest by network operators to deploy an optical transport
network (OTN). The OTN utilizes the technologies of time-division
multiplexing (TDM) and wavelength-division multiplexing (WDM) or
optical frequency multiplexing (OFM); new technologies such as
optical time division multiplexing (OTDM) and other techniques
toward an "all optical" networking capability may be
expected in the future. Specifications are needed for physical
layer interfaces of OTDM and WDM systems, including the OTN, to
enable the evolution of the intra-office, inter-office and long
distance networks to support the ubiquitous availability of
next-generation high-bandwidth services. To the greatest extent
possible, these specifications should enable transverse
compatibility in a multi-vendor, multi-network-operator
environment.
The responsibility under this Question includes the following
draft or published Recommendations:
G.664: Optical safety procedures and requirements for
optical transport systems
G.955: Digital line systems based on the 1544 kbit/s
and the 2048 kbit/s hierarchy on optical fibre cables
G.957: Optical interfaces for equipment and systems
relating to the synchronous digital hierarchy
G.691: Optical interfaces for single-channel
STM-64, STM-256 and other SDH systems with optical
amplifiers
G.692: Optical interfaces for multichannel systems with
optical amplifiers
G.959.1: Optical transport network physical layer
interfaces
Question
- What system aspects and physical layer characteristics are
necessary and sufficient to enable longitudinally compatible and
transversely compatible optical systems in intra-office,
inter-office and long distance networks, including evolution to
the OTN?
- What enhancements to existing draft or published
Recommendations and what new Recommendations are necessary to
describe TDM transport systems having bit rates up to or above
40 Gbit/s, as well as their upgrade by WDM techniques?
- What systems and physical layer considerations are necessary
for optical transport systems optimized for packet data
transport, e.g. IP over WDM?
- What systems and physical layer characteristics are necessary
for optical transport systems optimized for metropolitan
networks?
- What modifications are required for existing optical
interface specifications to enable them to be compatible with
applications beyond those specified in ITU-T, e.g. Ethernet?
- What enhancements should be made to existing draft or
published Recommendations to reflect technological developments?
Study items
Study items to be considered include:
- General considerations for optical systems based on the PDH,
SDH, and OTN using several types of single-mode fibre
- Elementary statistical and semi-statistical power budget
approaches
- Optical link and optical interface parameters for SDH systems
to enable transverse compatibility
- Optical frequency plan, including opt. supervisory channel
wavelength range, for WDM systems
- Optical aspects of TDM and WDM systems such as:
- Optical power levels including safety aspects and
automatic gain control
- Dispersion accommodation techniques, mainly passive
- Polarization mode dispersion system penalty
- Optical systems optimized for metropolitan networks
- Modifications to existing optical interface specifications to
enable them to be compatible with applications beyond those
specified in ITU-T, e.g. Ethernet
- Clarification and resolution of technical issues in current
and draft Recommendations
- Specifications to enable transverse compatibility in
single-channel, multichannel, and OTN optical systems
- Descriptive methodology for classifying application code
structures of optical interfaces to be standardized (e.g.
increasingly complicated systems with various dispersion
accommodation techniques, line codes, etc.)
- Characteristics of TDM line systems up to or above 40 Gbit/s
and their upgrade by WDM
- Short-distance systems to bring high-speed services closer to
the local access (with Q.2/15), while interfacing with the
longer-distance OTN systems
- Utilization of optical add-drop multiplexers (OADMs) and
optical cross-connects (OXCs)
- Application of forward error correction (FEC) to terrestrial
optical PDH, SDH and OTN transmission systems (e.g. to enhance
system margin or to relax optical parameter specifications)
- Optical systems utilizing alternative line codes, including
soliton-type techniques (e.g. dispersion-supported RZ or
solitons)
- Use of new types of optical amplifiers with changes in
systems wavelengths and/or power levels
- Additional passive and active dispersion accommodation
techniques
- Enhanced statistical design approaches
- Characteristics of optical systems optimized for data
transport, e.g. IP, SDH, ATM and Ethernet over an OTN
- Availability/reliability aspects of optical systems
Specific tasks
- Revisions to Recommendations G.664, G.955, G.957,
and G.692 (2003)
- Develop draft new Recommendation G.dsn on optical system
design and engineering considerations for single channel and
multichannel terrestrial applications (2003)
- Enhance Recommendations G.959.1 and G.691 (2003)
- Develop additional Recommendations or combine existing
Recommendations from progress on the above study points
Relationships
- Other relevant Questions and Recommendations of SG
15
- ITU-T SG 13 on SDH, OTN, and data-centric
architectures and network performance objectives (e.g., G.8070,
draft G.optperf)
- IEC SC86C on system measurement test methods and on
optical amplifier test methods
- IEEE on optical Ethernet technology
- IETF (e.g. for WG "IP over Optical"
activities)
- OIF – PLL (e.g. on intra-office interfaces and on
CWDM)
- Other national, regional, and multinational fora
and standards bodies, as appropriate
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