Starting from the current photonic infrastructures the paper illustrates the evolution of the backbone transport network in order to face the continuous bandwidth request for the coming multimedia services both in fixed and mobile services

1. The optical backbone evolution in the TLC operator
infrastructures
Ovidio Michelangeli
Wind Telecomunicazioni S.p.A,
Via C.G.Viola 48 Rome - Italy,
ovidio.michelangeli@mail.wind.it
Abstract: Start ing from the current photonic infrastructures, the paper illustrates the evolution of the backbone
transport network in order to face the continuous bandwidth request for the coming multimedia services both in fixed
and mobile services.
Keywords: ROADM , Backbone Transport Network,
1. Introduction
The continued growth in high-speed Internet applications will drive the backbone transport network migration for many
TLC operators in the coming years. The existing infrastructures are not more efficient to support the traffic demand due
to the fixed and mobile broadband services. The technological platform in the core are moving toward next generation
network based on packet switching rather than circuit switching and the traffic behaviour changes from the traditional
voice traffic (constant) to Internet traffic (instantaneous with large peak ).It is becoming mandatory for the TLC
operators to develop and implement transport solutions for high bit rate pipes (10G, 40G) delivering minimal cost per
transported bit and able to assure the highest network availability.
2. Wind Backbone Transport Network
WIND is a Global telecommunication operator providing integrated fixed, internet and mobile telecommunications
solutions in Italy. WIND is also equipped with an extensive national fiber network and an IP national Backbone. Wind
backbone Infrastructure consists of 19.100 Km of optical fibre :13.053 km are installed on ENEL / TERNA power lines
( 24 f.o. cables, G.652); 6024 Km are installed on the Railways lines as shown in Fig. 1 where 4319 Km are 72 f.o.
cables , G652 type while 1705 Km are on 4 F.O cables , G652 type.
The fibre cables on power lines are installed according the following techniques:
? WRAPPED: optical fibre wrapped around the ground wire or phase conductor
? OPGW: optical fibre inside the ground wire
Figure 3 : ROADM with GMPLS control planes Railway and Power lines
The WIND transport network consists of a meshed layer of Broadband Cross Connect (BB-XC) with control plane
functionalities Errore. L'origine riferimento non è stata trovata. Errore. L'origine riferimento non è stata

2. trovata. and SDH rings (at STM-16 and STM-64 level) distributed in a hierarchical architecture (local, regional,
national and Super backbone)
The DWDM systems (able to carry up to 32/64/96x10Gbits channels), are mainly used along the sections with lack of
fibre and to transport high capacity and long-distance traffic in a cost-effective way.
At the moment WIND is providing IP data connectivity to the IP network basing on the architecture IP over SDH over
DWDM where national SDH backbone is mainly based on a mesh network with restoration (Fig.2).
Figure 3 : ROADM with GMPLS control plane
3. Drivers to migrate the backbone transport network
TLC Carriers and service providers are once again rushing to upgrade their optical transmission infrastructure to be
better prepared for today’ competitive environment. New high-bandwidth multimedia services, business and storage
s
connectivity, and mobile 3G backhaul networks contribute to this race.
TLC Carriers are looking for an evolutionary approach to introduce new multimedia services, while maximising
revenues from legacy services and existing equipment and lowering the life cycle cost of their networks. This position
calls for new technological solution able to offer scalability, flexibility, and lower total cost-of-ownership. Traditional
fixed DWDM networks address the need for increased capacity and fibre relief but bring no flexibility. Provisioning,
maintaining, and deploying such networks are complex affairs that require multiple manual operations and frequent re-
engineering of the network, which results in high total cost-of-ownership. New technologies targeted at reducing overall
costs and increasing flexibility in the network are becoming available such as the automatically switched optical
network (ASON) platforms and ROADM.
4. Technologies Evolution
The key element for the future transport network is the ROADM. It enable cost-effective, simplified setup and
reconfiguration of optical connections via software control and provide automated power balancing. Automation of
optical power balancing is also a key feature of the new generation of ROADM and DWDM networks, eliminating the
need for manual, error-prone tuning of wavelength-level optical power, retuning as components age, and use of fixed
attenuation. The first deployments of ROADM was flexible but not dynamic and reconfigurable. Now are available
network based on deployment of reconfigurable optical add/drop multiplexer (ROADM) technology, controlled end-to-
end by GMPLS. The GMPLS control plane (Fig.3) enables bandwidth-based guaranteed services, priority-based
bandwidth allocation, and pre-emption services across dissimilar networks.

3. Figure 3 : ROADM with GMPLS control plane
5. New Transport network Architecture
Many TLC operators are evaluating different transport network architecture to meet the mentioned requirements. The
current network architecture (Fig.6) are based on IP over meshed network and the “IP over DWDM” solution (Fig.7)
due to reduced number of equipment/layers in the network (BB-XC nodes and the relative interfaces in the meshed
network).The idea for many TLC carriers is to build a new complementary network solution focused to transport mainly
high capacity IP traffic (10G, future 40G) and transparent lambda (2,5G, 10G..), that mandatory grants characteristics of
reliability and recovery on the transport layer at same or better level than the IPoSDHoDWDM. The new solutions
based on IP over DWDM provides savings in CAPEX and OPEX due to reduced number of new equipment/layers in
the network. Therefore the more adequate solution should be based on a WDM layer with mesh topology and providing
directly, in the optical domain, functions before available only in the SDH layer such as simple provisioning, restoration
and performance monitoring.ROADM technology should be the more cost effective solution able to realise an
intelligent DWDM layer instead of the more expensive OXC based on MEMS.
IP
ROADM
ROADM
WDM ROADM ROADM
ROADM
Figure 4. IP over WDM architecture
6. Conclusion
The all-optical core vision is becoming a reality. Optical Intelligent networks are viable and w see a gradual
ill
expansion in the operator backbone transport network in the coming years. The ROADM technologies with
GMPLS/ASON technique can meet the TLC Carriers expectation in terms of flexibility and OPEX/CAPEX saving.
7. References
[1] Ovidio Michelangeli, “Choosing between OEO and OOO solutions in the core and making a business case for DWDM in the MAN at the
edge level” Optical Switching Summit 30-31January 2002.
[2] E.Mannie et al.,”Generalized Multi- protocol label Switching (GMPLS) architecture “ Internet Draft <draft -ietf-ccamp-gmpls-architecture-
05.txt>, Mar.2003
[3] Ovidio Michelangeli , Evolving WIND’ Transmission Core Network towards an intelligent meshed network based on GMPLS/ASON.
s
IIR conference “Evolving SDH to support data srvices.London 3oth March- 1st April
[4] Ovidio Michelangeli;Alberto Mittoni;”Inserimento di reti ottiche magliate nella rete di backbone” Riva del Garda –Fotonica 2003
[5] Ronen Mikdashi, WSS ROADMs provide the flexibility of the future-today. Lightwave Europe September, 2007
[6] Authors’list, “Hollow Fibers Integrated with Single Walled Carbon Nanotubes: Bandgap Modification and Chemical Sensing Capability”,
Sensors and Actuators B, xxx (2007) xxx– xxx
[7] A. W.Snyder, J. D. Love, “Optical Waveguide Theory” 1983 Chapman and Hall, New York.
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