This article originally appeared on fibresystems.org.
WDM NICE 2009 — GMPLS and network automation were one of the key trends being discussed at IIR’s WDM & Next- Generation Optical Networking conference in Nice last week.
GMPLS emerged as a new control plane technology for optical networks almost 10 years ago, but it’s still a roadmap item for most ROADM vendors, according to Geoff Bennett, Infinera’s director of strategic marketing.
The ability to add new capacity quickly is often praised by Infinera’s customers, and to back up its point the vendor parked its GMPLS demo right outside the conference venue.
Service activation is one of the functions that GMPLS can enable, others being network design automation, routing optimization, protection and restoration, and real-time inventory reports showing exactly where equipment and bandwidth are available in the network.
Infinera argues that “you need a digital optical network to fully unlock the economic benefits of an intelligent optical control plane”. In other words, OEO conversions are required at each node, because this zeros the accumulated optical impairments. This removes the need to know about the physics of each optical link, which simplifies the routing algorithms and makes everything possible.
But other vendors disagree. Alcatel-Lucent, for one, appears to be working towards a similar goal of network automation with its “Zero Touch Photonics” concept. In his presentation on Tuesday, WDM product line manager Sam Bucci described several novel features for a ROADM-based network that would enable it to be operated with confidence from a remote operations centre.
A wavelength tracker integrated into the ROADM provides insight into the physical properties of the light. Digital signal processing (DSP) at the receiver eliminates the need for manual adjustments to dispersion compensating modules. The third feature — not yet available — is what the vendor calls “fast adaptable transponders”, which can adjust their optical output to suit the transmission line parameters. And then, of course, the network management software needs to tie it all together.
Not surprisingly given its dominance in the ROADM market, Cisco is also looking to automate ROADM networks using GMPLS — and calls its vision “Zero Touch Flexible Optical Networks”.
“We all agree that the control plane is the best way to drive savings in the network,” said Russ Esmacher, senior product line manager for Cisco’s optical transport business unit, in his presentation on Thursday, but noted that “at the moment GMPLS is photonically ignorant”.
However, it sounds like Cisco is working on this problem. Eschmacher suggested that the network could contain “strategically placed OEO conversions” with each ROADM having one or two OEO transponders available if required.
The GMPLS control plane would also need to be aware that the signal needs cleaning up. “A computation that is needed to determine if OEO is needed is something that a WDM network can do quite easily,” Esmacher claimed.
The other key pieces of Cisco’s solution are full-band tunable optics, which will be available from JDSU this year, and colourless and omni-directional ROADMs, where each port is not tied to a specific wavelength or direction. (Omni-directional is Cisco’s name for a “directionless” ROADM — after all, who wants a “directionless” product?)
Ultimately, this would tie in with Cisco’s vision of IP-over-WDM, which would see WDM optics added to core routers, and the router’s network management system making decisions about which photonic path to take over the WDM network.
However, “zero-touch” appears to be some way in the future. In Alcatel-Lucent’s case, the ROADMs are available now, but for full effect customers will have to wait for the new transponders, which will be introduced at various data rates over the next few years. Cisco did not give a time-scale for its vision.
And new technology always attracts a premium price; lower prices only come with product maturity and wider adoption. As one attendee put it: “When do you expect to have this at a cost level that most of us can afford?”
Reproduced with permission. © Institute of Physics and IOP Publishing Ltd.
