JULY 1, 2009 By Stephen Hardy -- The Optical Internetworking Forum (OIF; search Lightwave for OIF) has issued a framework document that spells out what it hopes to accomplish to aid the development of 100-Gbps long-haul DWDM equipment. The document not only explains the dual-polarization quadrature phase-shift keying (DP-QPSK) with coherent detection approach it has chosen as its focus, but highlights several implementation agreements and related project work.
The document is available here.
The OIF expects the projects to produce interface specifications that will support 100-Gbps transport via 50-GHz DWDM channels over reaches of 1000 to 1500 km through up to six ROADMs. The specifications should also be applicable to metro applications of shorter reach but with 20 ROADMs.
The effort is wide ranging, including not only the modulation format itself but such aspects as transceiver architecture (including mechanical aspects), integrated photonics, electrical interfaces, and forward error correction (FEC).
OIF Physical and Link Layer Working Group Vice Chair Karl Gass of Sandia National Laboratories and OIF board member Jeff Hitchens of CoreOptics said in an interview yesterday that work is well underway in all of these areas. While they hesitated to say when final specifications would be available, Gass revealed that draft documents for many of the specifications are already in place -- "They're well past half way," in his words.
However, the complicated FEC effort isn't one of them, Gass noted. The OIF is looking at both hard decision and soft decision approaches, according to the framework document. The tradeoffs among performance gains, the amount of overhead required, and propagation penalties due to higher symbol speeds number among the points of study.
The FEC function will reside within the module. Hitchens pointed to this decision as something that might not have occurred without the collaboration the 100-Gbps effort has created so far.
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