Super-Nyquist-WDM transmission over 7,326-km seven-core fiber with capacity-distance product of 103 Exabit/s·km

Abstract

We show super-Nyquist-WDM transmission technique, where optical signals with duobinary-pulse shaping can be wavelength-multiplexed with frequency spacing of below baudrate. Duobinary-pulse shaping can reduce the signal bandwidth to be a half of baudrate while controlling inter-symbol interference can be compensated by the maximum likelihood sequence estimation in a receiver. First, we experimentally evaluate crosstalk characteristics as a function of channel spacing between the dual-channel DP-QPSK signals with duobinary-pulse shaping. As a result, the crosstalk penalty can be almost negligible as far as the ratio of baudrate to frequency spacing is maintained to be less than 1.20. Next, we demonstrate 140.7-Tbit/s, 7,326-km transmission of 7 × 201-channel 25-GHz-spaced super-Nyquist-WDM 100-Gbit/s optical signals using seven-core fiber and full C-band seven-core EDFAs. To the best of our knowledge, this is one of the first reports of high-capacity transmission experiments with capacity-distance product in excess of 1 Exabit/s · km.

Performance limits in optical communications due to fiber nonlinearity

“…A typical transmission system is shown in Figure 10a and comprises a number of independent closely spaced transmitters, ideally with flat power spectral densities. Such signals include Nyquist WDM signals [147], OFDM signals [148] or all-optical OFDM signals [149] or super-channels [150]. The signals are transmitted over a link comprising multiple spans of fiber, with periodic amplification, either in the form of discrete amplifiers, such as Erbium doped fiber amplifiers, or distributed amplifiers, commonly based on the Raman Effect.…”

On-chip mode-division multiplexing switch

“…The difficulty in implementing switching for multimode waveguides is due to the contradictory design requirements: since the mode confinements in a multimode waveguide vary significantly between the different modes, the dimensions of the photonic structure required to perform the switching differ greatly from mode to mode as well. In fiber communication, despite the fact that spatial multiplexing has allowed enormous data rates over kilometers of fiber [28][29][30][31][32][33][34][35][36][37][38], its small index contrast Δn ∼ 5 × 10 −3 makes coupling between modes rather strong, and therefore, modes are not easily separable and switching is confined only to the wavelength domain [39][40][41][42][43]. In integrated silicon waveguides, due to the much higher index contrast Δn ∼ 2, coupling between modes is much weaker, and therefore, an integrated multimode platform could allow arbitrary access to individual spatial modes and wavelengths alike to enable reconfigurable switching [44,45] for fully flexible, dense, on-chip optical networks.…”

Impact of 4D Channel Distribution on the Achievable Rates in Coherent Optical Communication Experiments

“…However, using advanced FEC, PM-16QAM can be transmitted over transoceanic distances [4]. The use of advanced FEC in combination with PM quadrature phase shift keying (PM-QPSK) has enabled record SE-transmission distance products [5], [6].…”