By employing a single-mode multi-core fiber and an optical frequency comb source, NICT demonstrated SDM/WDM transmission realizing the new world record fiber-capacity of 2.15Pb/s (1Pb/s=1015b/s), which advances over the previous record by more than a factor of two. In this experiment, the latest technologies including dual-polarization 64QAM super-channel transmitters, power optimized broadband optical amplifiers and digital coherent detections, were also applied in view of future ultrahigh capacity long haul transmission.
As a transmission line, a 31km-long homogeneous 22-core single-mode multi-core fiber, designed and fabricated for this work by Sumitomo Electric, was employed. Homogeneous single-mode multi-core fibers are suitable for long-haul SDM/WDM systems since signal lights propagating through different cores have the same latency. However, suppression of signal cross-talk requires advanced fiber design and fabrication processes, and 19 was the highest number of homogeneous single-mode cores set in a single fiber for long-haul transmission prior to this work.
A high performance optical frequency comb source was employed as the signal carrier source, which can simultaneously generate hundreds of signal carriers covering the C- and L-bands from 1510 to 1620 nm with equal 25GHz-spacing. The frequency comb source, custom designed and fabricated by RAM utilizing a custom highly nonlinear fiber fabricated by Sumitomo Electric, has superior performance (narrow linewidth, low noise, high frequency stability, high mutual coherency, and low power consumption) compared to the performance of existing laser arrays.
The paper on this study was accepted and presented on October 1, 2015 as a postdeadline paper at the 41st European Conference on Optical Communication (ECOC2015) held in Valencia, Spain from September 27 to October 1, 2015. The paper was regarded as the best postdeadline paper and was awarded the Nature Photonics Award in ECOC2015.