The Optical Internetworking Forum has started specification of a new analogue coherent optics specification that will fit within a CFP8 pluggable module. The CFP8 is the latest is a series of optical modules specified by the CFP Multi-Source Agreement and will support the emerging 400 Gigabit Ethernet standard.
The analogue coherent optics (ACO) module is used for optical transport. The CFP module integrates the optics and driver electronics while the accompanying coherent DSP-ASIC resides on the line card. This enables systems vendors to use their own DSP-ASICs while choosing the coherent optics from the various module makers.
The OIF completed earlier this year the specification of the CFP2-ACO. Current CFP2-ACO modules support single-wavelength transmission rates from 100 gigabit to 250 gigabit depending on the baud rate and modulation scheme used. The goal of the CFP8-ACO is to support up to four wavelengths, each capable of up to 400 Gbit/s transmissions.
“This isn’t something there is a dire need for now but the projection is that this will be needed in two years’ time,” said Karl Gass of Qorvo and the OIF Physical and Link Layer Working Group optical vice chair.
The CFP8 occupies approximately the same area as the CFP2 but is not as tall such that the module can be doubled-stacked for a total of 16 CFP8-ACOs on a line card. Given that the CFP8 will support up to four 400Gbit/s carriers per module, a future line card could support 25.6 terabit/s of capacity. This is comparable to the total transport capacity of current dense WDM optical transport systems.
Rafik Ward, vice president of marketing at Finisar, says such a belly-to-belly configuration of the modules provides future-proofing for next-generation lineside interfaces. “Having said that, it is not clear when, or how, we will be able to technically support a four-carrier coherent solution in a CFP8 form factor,” said Ward.
Oclaro stresses that such a high total capacity implies that sufficient coherent DSP silicon can fit on the line card. Otherwise, the smaller-height CFP8 module may not enable the fully expected card density if the DSP chips are too large or too power-hungry.
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