WDM transmission of 603-Gb/s superchannels over 845 km of 7-core fiber with 42.2 b/s/Hz spectral efficiency

We demonstrate 845-km WDM transmission of eight 100-GHz-spaced 603-Gb/s superchannels in each core of a 76.8-km 7-core fiber placed in a recirculating loop. Space- and polarization-division multiplexing of 16-QAM OFDM signals yields a spectral efficiency of 42.2 b/s/Hz. Introduction Space-division-multiplexing (SDM) in multi-core fiber (MCF) has recently been demonstrated to have the potential to dramatically increase the obtainable capacity and spectral efficiency (SE) of a single fiber. A capacity of 305 Tb/s was achieved in a 10.1-km MCF with nineteen cores by combining SDM with wavelength-division multiplexing (WDM) and polarization-division multiplexing (PDM) of quadrature-phase-shift1 keyed (QPSK) signals . A capacity of 112 Tb/s was achieved in a 76.8-km seven-core MCF, 2 also using SDM-WDM-PDM-QPSK . A 1.12Tb/s superchannel based on coherent optical orthogonal frequency-division multiplexing (COOFDM) was later transmitted over this same 76.8-km seven-core fiber, and reached an intrachannel SE of 60 b/s/Hz by employing PDM and 32-point quadrature amplitude modulation (323 QAM) for subcarrier modulation . It is important to extend the transmission distance by using multi-span transmission to explore the potential of MCFbased SDM for practical long-haul applications. Since multi-core optical amplifiers for use in transmission systems are not yet available, tapered multi-core couplers (TMCs) with low loss and low crosstalk open the opportunity to perform multi-span transmission experiments based on multiple single-core amplifiers.