Market Spotlight: ROADMs

Operators need more efficient networks as they grapple with the cost of transporting ever-growing volumes of traffic, and are exploring all the different ways they can move traffic around their networks without breaking their capital and operating expenditure budgets.

The photonic layer is of particular interest to network planners. By using more advanced DWDM and Reconfigurable Optical Add/Drop Multiplexer (ROADM) technologies, operators expect the optical layer to make the greatest contribution toward the reduction of transport costs.

"ROADMs are widely deployed in metro and long-haul networks globally," says Sterling Perrin, senior analyst at Heavy Reading. "But what's been deployed so far has limited flexibility."

Add operational overload to limited flexibility. Since they only take fixed wavelengths, traditional ROADMs cannot exploit tunable transponders. If a transponder needs to be re-tuned, a service engineer must first unplug it and insert it into a new ROADM port. None of this helps carriers achieve their operational efficiency goals.

ROADMs are also limited in the number of "directions" to which an added wavelength can be routed -- that is, the number of connected nodes to which that added wavelength can be sent.

"Operators want ROADMs to do more of what they're good at," says Perrin. "They'd like an optical network that is fully flexible, with add/drop nodes operated in an automated fashion."

And it seems that demand for flexible ROADMs might be about to ramp: During the past decade, operators have focused on networking flexibility at the electrical layers, but these are now burdened. "It starts at the IP routers at Layer 3. Operators are now looking at how they can push traffic down the OSI stack to transport bits less expensively," says the Heavy Reading man.

There are several ways this can be done: Traffic can be moved to layer two, utilizing Sonet/SDH and Ethernet; to layer one, where Optical Transport Network (OTN) technology can be deployed; or to layer zero, the optical layer.

The problem with the optical layer is that it's the least flexible in terms of switching traffic rapidly, says the Heavy Reading man. "Innovation is needed to make the optical layer more useful in taking on some of these previous electrical layer functions -– that's all in flux right now."

New capabilities
So operators are looking to the system vendors -- and the component companies that make the Wavelength Selective Switch (WSS) modules at the heart of ROADMs -- to deliver new capabilities. The operators want Colorless and Directionless ROADMs -- designs that are fully automated in wavelength and direction -- as well as WSSs with higher port counts (or degrees).

They also want non-blocking Contentionless ROADMs that allow similar-wavelength lightpaths from different nodes to be dropped without wavelength contention. (See Verizon: Give Us More Flexible ROADMs for 100G.)

Another attribute on the carrier wish list is Gridless to accommodate future lightpaths above 100 Gbit/s. Operators want to ensure that the ROADMs they deploy will be more flexible in terms of bandwidth, allowing them to accommodate 400Gbit/s or 1 Tbit/s transmissions that are too "wide" to fit within today's 50 GHz channels.

"The hold-up has been the technology [progressing] to a point needed to create architectures that are colorless, directionless, contentionless, and gridless," says Perrin. And the delay isn't limited to the WSS elements, but also to Control Plane software and alternative technologies, such as 3D MEMS (microelectromechanical systems). "It even includes coherent technology, which is another way of making the optical layer more flexible," adds Perrin. (See Operators Hang Big Hopes on ROADMs.)

"3D MEMS is a new trend," says the analyst. A decade ago vendors were looking at the technology to create optical cross-connects. Now, lower port-count versions are appearing that could be used at the add/drop while working with WSSs.

"The advantage of 3D MEMs is that it reduces the number of WSSs needed," says Perrin, who cites 3D MEMS firms such as Calient Technologies Inc. and CrossFiber Inc. . (See Calient Gets Ambitious With Optical Switching.)

What's really needed? Cost reduction
The half-dozen leading ROADM vendors interviewed by Light Reading all acknowledged the need for colorless and directionless features. They are less clear about a timescale for contentionless ROADMs as they're unsure about carrier demand, and some question whether gridless ROADMs will ever be deployed.

For all involved -– the operators and the vendors -– cost is the biggest hurdle. Market demand is largely met by existing, lower-degree, modest ROADMs, and while operators generally want greater functionality, high initial costs mean advanced ROADM shipment volumes during the next five years will be limited. That, in turn, makes cost reduction from the supply side a significant challenge.

"I've talked to several operators, and they are gung-ho on making the optical layer more flexible," says Perrin, who reiterates that the carriers want a meshed switching layer that takes on more of the electrical layer's burden. "It will never do all the electrical layer's functions, but the more [bits it can transport] the less expensive it is to transport those bits," he notes. "That’s the fundamental driver."

The current technology hold-ups, and the operator/supplier discussions, mean it will be about two years before next-generation ROADMs are deployed, predicts Perrin.

So what are the vendors doing to meet the major operators' needs and shorten that time to market? Light Reading spoke with the following companies about their ROADM platform offerings and strategies:

On the following pages, each of these companies outlines its ROADM portfolio and provides feedback on market demand and the need for new capabilities.

Here’s a hyperlinked contents list:

— Roy Rubenstein, editor of Gazettabyte, special to Light Reading

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obaut 12/5/2012 | 4:18:52 PM
re: Market Spotlight: ROADMs

It often seems that, more than technology capabilities, it is the must-do situations of the market conditions that cause any new technologies to be adopted.

This flexible/dynamic/adaptive packet-optical networking R&D has gone on for a well over a decade, with only modest incremental/linear improvements in commercial technologies since the introduction of WDM.

What does it take this time for us to see another break through, similar to WDM itself?

At least by IBSG's data, the cross point in the SP's revenue and cost per bps curves (with revenues per bps decreasing faster than costs with present generation of technologies) is estimated to happen in 2012 -- see the lower slide "SP Economics" on page 12 at:


This breakpoint in ca. 2012, after which building IP backbone networks with current generation of technologies is to turn unprofitable, is sooner than than the typical 3 years or so of new SP technology platform development cycle allows.

Thus the question: does any of the SP tech vendors have an un-announced break through technology in their labs, to be launched on the market 'just-in-time' before the business case for upgrading networks with current generation (non-packet-aware layer 1/0 transport) turns negative?

To a degree such delayed launch might be understandable, given the high R&D&T cost of SP tech platforms to be amortized.

In any case, the question of restoring a profitable business case for carrying Internet traffic will be about a technological break through comparable to WDM (or original packet-switched services) itself, not simply linear extension of the present gen of WDM.

In essence, the benefits of more feature-rich optical domain switching (trying to make the optics perform the functions previously done in digital domain, eg DXC) will be offset by increasing the cost per bps of optical networking.

Instead, what seems to be needed is some type of NEW capability, at what ever existing or new layers or dimensions, not mere tradeoffs such as more efficient optical capacity usage at the expense of more costly capacity per bps.

spc_markl 12/5/2012 | 4:18:51 PM
re: Market Spotlight: ROADMs

Big changes in technology in the public network have come because of aberrations.  It seems like there is one big one every decade.  In the 1970's, there was the unusual situation of the Bell companies forecefully insisting to AT&T that they needed digital CO switches.  In the 1980s, it was the divestiture of AT&T, resulting in massive spending on long-haul fiber optics in order for MCI and Sprint to catch up to AT&T.  In the 1990s, it was the fact that Sprint desperately needed four-fiber, bi-directional rings, and because that capability was not available on 10G at that time, it enabled the creation of Ciena.  In this past decade, it was the FCC changing the rules on unbundling fiber, which led to the unprecedented level of spending on FTTP by Verizon (Of course, we have argued it was more about FTTB than FTTH.)  There will likely be another large aberration in the coming decade, but it obviously cannot be predicted, and it may have nothing to do directly with the technology itself.

Mark Lutkowitz, Teleccom Pragmatics

spc_markl 12/5/2012 | 4:18:50 PM
re: Market Spotlight: ROADMs


You make some valid points.  Really, the Internet as a whole could be considered an aberration -- nobody anticipated the impact on networks in advance.


opticalwatcher 12/5/2012 | 4:18:50 PM
re: Market Spotlight: ROADMs

Mark, that's an interesting way to look at it.

Would you include in the abberation list the massive increases in cloud computing and datacenters, driven on the consumer level by the Amazons, Googles, Netflixes, and Facebooks, and all kinds of remote data/computing happening on the business level,

or maybe the sudden growth in smartphones, and the resulting growth of data on the network?

Certainly all the COs and Clearwire are spending billions on backhaul and to upgrade the core to keep up with it.

obaut 12/5/2012 | 4:18:48 PM
re: Market Spotlight: ROADMs

Regarding the point that googles, facebooks etc consumer/entertainment oriented (over the top) services being the main drivers for Internet traffic growth, one should really now pay attention to the traffic growth and SP revenue/cost data in the presentation linked within my previous post: Will the billions to be spent in IP/optical broadband access / backhaul / core be recoved?

Consumer income development (which may stay basically flat for sometime) does not allow the network SPs to get much more revenue, even for new/premium services. Corporate IT budgest are not looking much more promising either.

What will happen when/if the more rapidly declining SP revenue/bit curve crosses the cost/bit curve?

It appears that the incremental developments in optical switches will not give but, at most, a short lived extension of time until the costs of SP networks cannot be covered with revenues achievable. IP routing costs do not seem to be decreasing either, with IPv6, Internet fragmentation etc complicating the routing further. Further still, the stream oriented, delay/jitter intolerant nature of major bandwidth demanding applications (IPTV, video etc. multimedia) do necessitate minimizing any type of packet level switching/buffering in the network, which factor conventionally would cause the (optical) network transport capacity to have low average utilization for any type of traffic--high revenue or low.

Any ideas what the solution could be?

spc_markl 12/5/2012 | 4:18:46 PM
re: Market Spotlight: ROADMs

A robust US economy.  For example, eliminate the capital gains tax and there will likely be a boom like we have never seen before.


neyo 12/5/2012 | 4:18:35 PM
re: Market Spotlight: ROADMs

All above companies are vendors who want to sell their wares. 

But does the carrier really need a colorless, directionless, contentionless, gridless ROADM ? and for what ? for OPEX reduction ? There is hardly a case for opex reduction. Wavelengths don't change their color, direction over time and therefore even contentionless is out of question. Gridless, maybe. But if the current network design itself does not support higher capacity, the carrier can simply deploy a new platform altogether.

So its all about wavelength restoration - to survive multiple simultaneous fiber cuts in the network. Can't we just manually restore some wavelengths in case of such a rare emergency? Is there a need for a colorless, directionless, blah, blah investment? 

The survey results from light reading for CDC ROADMS. 



spc_markl 12/5/2012 | 4:18:34 PM
re: Market Spotlight: ROADMs

The idea that vendors' equipment offerings can lead to OPEX savings has been overhyped for years.


spc_markl 12/5/2012 | 4:18:33 PM
re: Market Spotlight: ROADMs


The assumption that I am making is that increased investment will lead to greater employment, which will mean more spending by consumers here.


paolo.franzoi 12/5/2012 | 4:18:33 PM
re: Market Spotlight: ROADMs


So, the thing is that carriers are much more in control than is portrayed.  Suppose they do NOT lower the price of consumer Internet service.  The presentation assumes that this will continue but in fact it is not written in stone.  What can be said (I think for sure) is that consumers want to use a larger percentage of the bandwidth they have already paid for.  The carriers are countering with bandwidth caps, which are likely to become more meaningful over time.  I think this is the basic flaw here.



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