10 × 112-Gb/s PDM 16-QAM Transmission Over 630 km of Fiber with 6.2-b/s/Hz Spectral Efficiency

Scaling optical communications for the next decade and beyond

“…To further advance spectral efficiency, one can envision increasing the number of constellation points using, for example, 16 QAM. Gnauck and co-authors [5] have recently demonstrated a spectral efficiency of 6.2 b/s/Hz for 100 Gb/s channels using polarization multiplexed 16 quadrature amplitude modulation (QAM) on a 16.7 GHz spacing. Doubling this spectral efficiency through the use of more constellation points would require the use of 256 QAM.…”

100 Gb/s DQPSK field trial: Live video transmission over an operating LambdaXtreme® network

“…and compares them to various other modulation options, including 100 Gb/s measurements and idealized simulation results. Requirements are presented for NRZ-OOK [50], VSB-NRZ-OOK [37], NRZ-DQPSK [33,53], RZ-DQPSK [33,53], PDM RZ-DQPSK using both 94 Bell Labs Technical Journal DOI: 10.1002/bltj direct detection [4] and coherent detection [15], and PDM 16-QAM [16].…”

“…Generally, when the data rate is increased for binary modulation formats such as nonreturn-to-zero on-off keying (NRZ-OOK), the corresponding optical bandwidth increases and the reach is reduced. Recent research and development of advanced modulation formats with differential phase demodulation as well as with coherent detection have paved the way for potential upgrade paths to 100 Gb/s (see for example [15,16] and [57]). …”

“…Coherent ASICs have been demonstrated for operation at 10 Gbaud [41], and existing complementary metal-oxide semiconductor (CMOS) processes are expected to support 112 Gb/s designs operating at 28 Gbaud. Modulation formats going beyond 4 levels per polarization have also been reported for 100 Gb/s operation [16,57]. Importantly, however, the lack of ASICs in research and development environments forces researchers to either experiment at lower symbol rates using Field Programmable Gate Arrays (FPGAs) or characterize their systems and determine bit error ratios (BERs) using offline signal processing on a personal computer.…”

111-Gb/s PolMux-Quadrature Duobinary for Robust and Bandwidth Efficient Transmission

“…PolMux-16 quadrature amplitude modulation (QAM) was proposed as an alternative modulation format with higher SE for 100 Gb/s [2], but its lower robustness to nonlinear transmission impairments and the need for a more complicated transmitter [2], [5] OFDM, on the other hand, can achieve very high SE [3] with a robust performance, but that comes with the price of having a complicated transmitter that requires having digital-to-analog converters with high vertical resolution.…”