Everything old is new again
Stephen M. Hardy
Editorial Director & Associate Publisher
One of our cover stories this month, “All-optical-switch market revives…again,” illustrates an interesting trend we’ve noticed over the past six months. One by one, technologies that made a splash during the bubble’s high tide, then appeared to drown when the tidal wave hit, have begun to bob on the surface.
Photonic switches at one time were hailed as the linchpins of the future all-optical network, which appeared to be just around the corner as the current century dawned. Meghan Fuller describes in this month’s article how that dream hasn’t quite died in some minds. She also relates relatively new applications such as test and measurement where all-optical switches provide an attractive technology option.
Even within the photonic-switching arena itself, technologies that were once thought passé have found new life. 2D MEMS architectures, while popular at first during the original photonic-network excitement, were subsequently derided as less efficient and bulkier than the 3D designs that followed them. However, I heard from a systems vendor at OFC/NFOEC earlier this year that 2D MEMS technology could provide the cornerstone of wavelength-selective switches at the heart of future reconfigurable optical add/drop multiplexers (ROADMs).
But all-optical switches aren’t the only bubble technologies making a comeback. We described last month how planar-lightwave-circuit (PLC) technology has moved beyond arrayed-waveguide gratings for multiplexers/demultiplexers into a variety of applications, particularly fiber to the premises (see “PLC development gets active,” May 2005, front page). The original promise of the technology involved integration at the wafer level, and that promise has come closer to reality. We’re seeing transceivers based on the technology as well as external-cavity lasers.
Meanwhile, the advent of 40-Gbit/sec transmission networks finally appears at hand. Deutsche Telekom’s recent contract awards to Marconi and Siemens clearly had this line speed in mind. Meanwhile, carriers in the States, such as MCI, have staged several demonstrations and regard 40 Gbits/sec as a potential match for their requirements as soon as the price comes down.
One bubble technology that has established a beachhead on the market finds itself having to defend its position is tunable lasers. Meghan reports in another article this month (page 11) that while tunable devices have secured a niche for themselves as a sparing alternative, SFP transceivers threaten to erode that foothold due to their low cost. Meanwhile, unlike PLCs and photonic switches, tunable lasers have not progressed very far along the path toward integration within systems that make use of their attributes in the field. We heard a lot about using tunability to reconfigure networks when the technology first appeared-and hearing about it for the most part remains as far as that evolution has progressed. In fact, the 2D MEMS devices or liquid-crystal switches right now appear to be a better bet for ROADM applications. That doesn’t mean tunable devices have no place in reconfigurable networks; for example, they certainly appear to provide a smart way to perform wavelength conversion and, as Meghan’s article explains, they don’t face competition from SFPs everywhere in the network.
Perhaps tunable technology merely awaits the introduction of the sort of catalysts that the other bubble babies have enjoyed. These include the time for technology maturation to catch up with initial promise. This factor clearly appears to play a role in the more widespread use of PLCs. Another driver is the ability to match the technology to a more appropriate application than originally envisioned. By “appropriate” I mean from a customer requirement perspective. It turned out that carriers didn’t need photonic switches as quickly as originally expected. However, test equipment vendors and their customers who could profit from automating their lab structures can benefit from all-optical switches today. Finally, the market may just have to catch up to a technology that was too far ahead of its time. Photonic switches for carrier networks represent one example of this phenomenon that remains in place; however, carrier requirements finally may have evolved to the point where 40-Gbit/sec systems may make sense.
Naturally, all three factors-technical maturity, finding the right niche, and no longer being ahead of the market-play off each other in just about all the cases described here. And they perhaps offer a path other technologies may follow, albeit maybe not in their original forms. I’m not looking for anyone to resurrect the S-band amplifier, but low-water-peak fiber has opened that spectrum for CWDM and other applications. So maybe I should keep my mouth shut, because the current activity in PLCs, all-optical switching, and 40-Gbit/sec systems demonstrates that you just can’t count any technology out anymore.
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