OFC/NFOEC: For ROADMs, Less Is More
It's all part of making ROADMs more flexible in order to give service providers more options. The gridless ROADM -- vendors seem to favor the phrase "flexible spectrum," actually -- has gained some buzz amidst all the 100-Gbit/s chatter, because the technology could be useful for carrying unusually high-speed signals.
And like a lot of ideas proposed in optical networking, it's not new. "I think this question pops up every five years," says Krishna Bala, executive vice president with Oclaro Inc. (Nasdaq: OCLR).
Being gridless refers to having wavelengths that don't conform to the ITU grid for Dense Wavelength-Division Multiplexing (DWDM). Specifically, it's about letting wavelengths take up irregular numbers of slots -- 1.4 or 2.2 times more spectrum than usual, for instance.
That could be useful for very high-speed signals or experimental modulation schemes, cases where carriers "aren't sure how much passband they'll need," says Craig Iwata, manager of corporate marketing for JDSU (Nasdaq: JDSU; Toronto: JDU).
But Iwata says he was previously hearing those concerns for 100 Gbit/s, and it's already being shown that a serial, long-haul, 100-Gbit/s wavelength can, indeed, fit in a 50GHz ITU grid. And Bala -- who joined Oclaro through its acquisition of Xtellus last month -- notes that the industry is trying to keep to some standards for line-side 100-Gbit/s interfaces, which he thinks would make anything with nonstandard grid spacings unpopular. (See Oclaro Acquires Xtellus.)
Each of them doubts that demand for flexible-spectrum ROADMs will get heavy any time soon.
Others aren't so sure. Ashish Vengsarkar, CEO of ROADM subsystems vendor Nistica , says he's hearing of interest in the technology right now.
And Nokia Networks seems to like the idea of having a gridless ROADM at the ready, as the company experiments with line-side speeds exceeding 100 Gbit/s.
"There's some way to do 200 Gbit/s within a 50GHz grid, and people have done 100 Gbit/s within 25GHz, but these are based on really complex modulation schemes," says Michel Chbat, the company's North American head of solution engagement.
Should a need for gridless ROADMs emerge quickly somehow, Finisar Corp. (Nasdaq: FNSR) might have an edge. The company's wavelength-selective switch (WSS) is software-programmable to arbitrary grid spacings, even irregular ones. The capability appears to make Finisar's the only shipping WSS that could produce a gridless ROADM.
— Craig Matsumoto, West Coast Editor, Light Reading