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Next-generation elastic optical interfaces will support a wide range of line rates and modulation formats. Such transmission schemes enable doubling of the channel capacity at the expense of a lower reach, whereas a flexible DWDM grid supports the transport of multiple optical signals within a single frequency slot by packing them closely, thus saving spectral resources. The resulting multitude of options on the line side provides network planners the capability to derive the most suitable one for each individual path inside the network. However, planning and operational complexity should not be overlooked, since aspects such as added spectrum fragmentation can hamper the expected network improvements. This paper investigates how to obtain the best compromise between harnessing the main benefits of next-generation optical interfaces, while keeping the complexity of the underlying system at a reasonable level. In particular, we define a novel network spectral efficiency (SE) metric that enables, on one hand, to highlight the relevance of supporting a flexible grid to improve SE and, on the other hand, to demonstrate that the grid granularity can be based on coarser 50 GHz increments without major penalties. The effectiveness of this parameter has been verified by considering two reference network topologies. Finally, the paper also discusses how future optical interface technology developments will shape network design. [ABSTRACT FROM PUBLISHER]

For the first time, we successfully demonstrate the transmission of commercial 10- and 100-Gb/s interfaces, both direct detect and coherent, over 2.75 km of hollow-core fiber. The fiber is connected to the transceivers using spliced standard single-mode pigtails. This demonstration solidifies the commercial potential for low latency applications. [ABSTRACT FROM PUBLISHER]

We experimentally demonstrate, for the first time to the best of our knowledge, an ultralong-haul dense wavelength division multiplexed transmission of 96 \,\, \times \,\, 100 Gb/s coherent polarization multiplexed quadrature phase-shifted keying transponders over ITU-T G.655 nonzero dispersion-shifted large effective area fibers (NZ-DSF) with an effective core area of 72 \mu \text{m}^{2} , employing both commercial erbium-doped fiber amplifiers (EDFA) and hybrid EDFA + Raman amplification systems. Using the state-of-the-art digital pulse shaping and digital preemphasis algorithms, we report \sim 1.5 dB back-to-back optical signal-to-noise ratio penalty at pre forward error correction (FEC) bit error rate (BER) threshold ( 3.8\times 10^-2 ), with respect to theoretical performance. In particular, we demonstrate \sim 6500 km transmission across the entire C-band, at pre-FEC BER of 3.8\times 10^-2 , employing EDFA + backward Raman amplification—where the central channel (1552.2nm) had sufficient margin to enable transmission of up to $\sim 8000$ km. Furthermore, we report that hybrid amplification enables up to \sim 60$ % improvement in maximum transmission reach, compared to EDFA based links. To the best of our knowledge, a record capacity-distance product of \sim 62.4~\textrm {Pb}/\textrm {s}\cdot \textrm {km} is achieved for NZ-DSF—an 11-fold increase, compared with the previous literature. [ABSTRACT FROM PUBLISHER]

The world is connected by a core network of long-haul optical communication systems that link countries and continents, enabling long-distance phone calls, data-center communications, and the Internet. The demands on information rates have been constantly driven up by applications such as online gaming, high-definition video, and cloud computing. All over the world, end-user connection speeds are being increased by replacing conventional digital subscriber line (DSL) and asymmetric DSL (ADSL) with fiber to the home. Clearly, the capacity of the core network must also increase proportionally. [ABSTRACT FROM PUBLISHER]

We present the first demonstration of combined wavelength-division multiplexed (WDM) and mode-division multiplexed (MDM) optical transmission in a hollow-core photonic bandgap fiber (HC-PBGF). For this purpose a novel low loss, broadband 310 m long HC-PBGF with a 37 cell (37c) core geometry is used. The modal properties of the HC-PBGF are characterized in detail, showing an absence of surface modes and low modal crosstalk, which enable WDM and MDM transmission with record high capacity (73.7 Tb/s) for a HC-PBGF. Several modulation formats have been tested, showing very good and stable performance. The transmission properties are assessed by looking into both single-mode transmission and MDM transmission, showing good agreement with the modal characterization of the 37c HC-PGBF. [ABSTRACT FROM PUBLISHER]

Wavelength selective switches (WSSs) that are integrated in reconfigurable optical add-drop multiplexers (ROADMs) induce penalties on the optical signal due to tight optical filtering, which increases as several ROADMs are cascaded in a meshed network. In this letter, we propose and analyze possible configurations for the mitigation of these penalties in optical domain using optical wave shaper (WS). Including one WS in every ROADM node allows transmission of 28 and 32 GBd signals, which are QPSK, 8-QAM, or 16-QAM modulated, through a cascade of 32 and 14 WSS filters, respectively. With an average bandwidth of 33 GHz per WSS, an optical signal to noise ratio penalty below 1 dB at BER=1×10-3 is observed. [ABSTRACT FROM PUBLISHER]

In this letter, 3.072-Tb/s (six spatial and polarization modes \times4 wavelength-division multiplexing (WDM) \times128\-Gb/s 16QAM) transmission over 30 km of few-mode fiber (FMF) is demonstrated employing a photonic integrated mode coupler based on silicon-on-insulator (SoI) technology. A 2-D top coupling solution with five small vertical grating couplers is proposed for coupling between an SoI chip and an FMF, guiding LP01 and LP11 modes. Push-pull and center launch configurations for exciting LP11 and LP01 modes, respectively, through mode-profile matching are analyzed and implemented on the SoI chip. [ABSTRACT FROM PUBLISHER]

In this paper, we experimentally investigate the tolerance of 111-Gb/s polarization multiplexed-return to zero-differential quadrature phase-shift keying (POLMUX-RZ-DQPSK) to the different nonlinear transmission impairments in different links structures. We analyze the effect of dispersion maps for four different fiber types and show that with sufficiently large per-span under-compensation in the double periodic dispersion map, a dispersion managed (DM) link can nearly have a similar performance to a non-DM link. Furthermore, we confirm that the super large effective area fiber family can provide around 3 dB advantage in the tolerance to nonlinear effects compared to standard single-mode fiber. Finally, we demonstrate that interleaving the two polarization tributaries of the 111-Gb/s POLMUX-RZ-DQPSK signal provides only a negligible advantage in terms of tolerance to nonlinear effects. [ABSTRACT FROM PUBLISHER]