ADVA's approach combines four 25Gbit/s wavelengths into one feed that fits in one ITU grid assignment. This feed can be carried by optical gear as if it were a single wavelength. ADVA isn't saying what modulation scheme is behind 100G Metro, but it doesn't appear to be the three-amplitude shift keying (3ASK) that the company introduced in 2009.
Why this matters
The OIF framework is nice, but it's targeting a high-tier market. For metro networks and data centers, operators are asking for something cheaper, according to ADVA and other equipment vendors.
That's led to some 100Gbit/s alternatives that don't use coherent detection. Huawei Technologies Co. Ltd. has one, and Ericsson AB (Nasdaq: ERIC) proposed one in December.
None of this discredits the OIF framework; in fact, ADVA discussed a 100Gbit/s coherent extension to the FSP 3000 in February. But it's looking like a multitude of 100Gbit/s metro options could emerge, in contrast with the unified approach the OIF has set for long-haul 100Gbit/s.
Some operators need 100Gbit/s simply as a way to transmit more 10Gbit/s feeds without using more ITU wavelengths, and they say coherent 100Gbit/s is too expensive for the task, according to ADVA. Moreover, influential data-center owners including Amazon Web Services LLC and Google (Nasdaq: GOOG) want less rigorous standards than the carriers do, says Ron Kline, an analyst with Ovum Ltd.
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