Abstract
Digital coherent technologies enabled the use of spectral-efficient modulation formats with forward error
correction codes as well as the waveform equalization for overcoming the transmission distance limit
due to polarization mode dispersion and chromatic dispersion. Currently, transmission capacity over a
single-mode fiber (SMF) reached 100 Tb/s in laboratory experiments, but it is close to the physical
limitation restricted by the fiber nonlinearity and fiber fuse. Space division multiplexing (SDM)
techniques are indispensable for breaking the capacity limit of standard SMF. In particular, dense SDM
(DSDM) technology, which is defined as SDM with spatial multiplicity of ≥ 30, has been extensively
studied for realizing optical transport networks with the scalability beyond 1 Pb/s capacity. In this paper,
DSDM technologies including a system concept and its recent progress are discussed for realizing Pbit/
s-class capacity transmission systems. We also describe the world first 1 Pb/s unidirectional inlineamplified
transmission experiment over 205.6 km of single-mode 32 core fiber.
