hard choices - Paul Momtahan
Optical layer pluggables: the end of hard choices in the metro?
The trend for network operators to transition from integrated interface optics towards compact pluggables, such as XFPs and SFP+ devices, is having a dramatic effect on cutting 100G WDM interface costs, argues Paul Momtahan, Director of Optical Solutions Marketing, at Coriant.
Monitoring, Optical Supervisory Channel, and even Wavelength Selective Switches all evolving to compact pluggables, based on SFP, XFP or other pluggable form factors similar to CFPs. Cutting costs by 30% The first benefit of optical layer pluggables is reduced costs – more specifically capital costs – which can be up to 30% lower than traditional alternatives. Moving to compact pluggables can reduce the cost of each function, just as moving to pluggable optics did for port card interfaces. Secondly, by moving to this disaggregated approach, network operators are free to choose only the functions they need when they need them. In addition, operational cost is reduced by the minimised footprint and the reduced power consumption of this approach, with savings of up to 70% and 50%, respectively. Furthermore, many of the operational benefits of ROADM- based networks, including the auto-balancing of amplifiers and auto-equalisation of channels, are possible with the Pluggable
Over time more advanced optical functions can evolve to compact pluggables including multi-degree ROADM, route & select ROADM, colourless and directionless add/drop, OTDR and Raman amplification. The end for DWDM? The systems-on-a-blade approach will continue to occupy the high-end of the metro ROADM market with advantages in terms of scaling, advanced add/ drop functionality, better performance in terms of reach, and simplified cabling. In long haul, the modular approach will still have advantages where maximum reach can be enabled with the aid of a wide range of amplifier options. Initially targeted at metro network, optical layer pluggables will complement the systems- on-blade approach with a cost-effective, flexible and future-proof solution for fixed WDM and more basic ROADM applications, evolving over time with more advanced functionality enabling more advanced add/ drop options, greater scalability and improved reach.
Optical Layer approach if the appropriate functions are in place. Flexibility A second key benefit is flexibility. This disaggregated approach based on compact pluggables enables a wide range of applications including CWDM, passive fixed DWDM, amplified fixed DWDM, optical line amplifiers and even ROADM, with the set of functions tailored to each network’s requirements. A wide range of topologies, distances and traffic patterns can be supported by combining passive components such as mux/demux filters and band splitters with different amplifier combinations and using EVOAs or WSSs and power monitoring for balancing. Lastly in terms of benefits, optical layer pluggables offer a future-proof solution that maximises investment protection. For example, it may be possible to start with a fixed DWDM network then evolve to a ROADM-based network as traffic patterns and needs evolve.
Paul Momtahan Director of Optical Solutions Marketing, Coriant I nternet video, enterprise cloud, and Data Centre Interconnect (DCI) are driving unprecedented traffic growth and unpredictable traffic patterns in metro networks. At the same time, network operator budgets are constrained in terms of both CapEx and OpEx as this traffic growth has not been matched by corresponding top line revenue growth. This environment has – until now – forced network operators to make hard choices about the following issues: the low start- up cost of fixed WDM or the flexibility and operational savings of ROADM; and the flexibility of a DWDM system with separate modules for each function or the compact footprint and installation simplicity of systems- on-a-blade approaches. However, a new approach to building metro networks is emerging, one that is enabled by the miniaturisation of key optical layer functions into compact pluggables. Moving from integrated interface optics to multi-source agreement (MSA) subsystems to compact pluggables in the form of XFPs, and more recently SFP+, has had a dramatic impact on 10G WDM interface costs and is having a similar impact on 100G WDM, as the latter follows a similar trajectory, evolving from integrated interface optics to CFP and CFP2 pluggables. This same evolution is now starting to impact the optical layer, with fixed gain EDFAs, variable gain EDFAs, EVOAs, Per Channel Optical Power
SONET/SDH SWITCHING
OTN SWITCHING
L2 SWITCHING
TRANS/ MUSPONDERS
Intelligent Services Layer
Coriant 7100 Packet Optical Transport Platform Coriant Innocation Flexible Pluggable Optical Layer
7100 PICO
7100 NANO
Pluggable Passive Components
Pluggable Active Components
BAND MUX/ DEMUX
OPTICAL CHANNEL MONITOR EDFAs
DWDM FILTER
CWDM FILTER
WSS
EVOA
OPTICAL PLUGGABLE
CFP2 LIKE XFP
SFP
PLUGGABLE FILTER
BAND MUX/ DEMUX
The Pluggable Optical Layer enables operators to mix and match different functional components without the need to pay for unwanted or unneeded functionality.
ISSUE 6 | Q1 2016 18
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