OFS demos benchmark 120 Gb/s transmission over single, 100 m multicore multimode fiber strand

OFS said recent demonstration proves the viability of multicore multimode fiber as a transmission medium for next-generation data center and supercomputer networks.

OFS recently announced what it calls "a world record transmission" of 120 Gb/s over 100 meters across a single strand of multimode fiber. The joint demonstration, held at the recent OFC 2012 tradeshow, was enabled by a seven-core laser-optimized multimode fiber made with the OFS LaserWave fiber technology, interfaced with custom-designed transceivers from IBM Research. The demonstration also employed custom-designed VCSELs [vertical-cavity surface-emitting lasers] and photodiodes from Emcore.

OFS said the demonstration exceeded both the previous transmission length record by 60 meters, and the previous data rate record by 50 percent. "This demonstration illustrates the viability of multicore multimode fiber as a transmission medium for next-generation high-performance computer networks," commented Dr. Durgesh S. Vaidya, senior manager of R&D at OFS.

The demonstrated OFS fiber consists of seven graded-index multimode cores in a hexagonal array. Each of the six outer cores transmits at 20 Gb/s over 100 meters using Emcore's two-dimensional arrays of VCSELs and vertically illuminated photodiodes, fabricated in a commercial process with a geometry corresponding to the outer six cores of the fiber.

The fiber's 26 micrometers core size is directly compatible with the photodiodes needed for 25 Gb/s transmission (20 – 30 micrometers diameter). The 20 Gb/s VCSELs were flipped chip packaged on an IBM-designed transceiver employing 130 nm CMOS ICs, and the full link was characterized by IBM Research with all six channels running error-free simultaneously.

The company contends that the additional bandwidth density provided by the multicore fiber link over standard multimode links, combined with advanced light sources such as the Emcore custom arrays, will help to enable more efficient high-performance computers and data centers, while the larger core sizes -- compared to singlemode fiber solutions -- will serve to help keep packaging costs sustainable.

"The expected increase in demand for optical fiber cable in [future high-bandwidth] applications will result in significant network design challenges," Vaidya noted. "While bandwidth requirements continue to grow, network managers face considerable constraints on power and cost budgets, not to mention the physical space required by the fiber cabling. Increasing the bandwidth available on each fiber is a critical step in developing optical interconnects for future networks, not only for high-performance computing but also for data centers, another key growth market for optical fiber."

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