256-QAM (64 Gb/s) Coherent Optical Transmission Over 160 km With an Optical Bandwidth of 5.4 GHz

60Gbit/s 64 QAM-OFDM coherent optical transmission with a 5.3GHz bandwidth

“…60 Gbit/s data (58.8 Gbit/s without OFDM overhead) were successfully transmitted with a demodulation bandwidth of 5.3 GHz. This indicates the possibility of a spectral efficiency as high as 11.1 bit/s/Hz in a multi-channel transmission, which is almost the same as the level we achieved in a single-carrier 256 QAM transmission [5].…”

“…We have already described the highest reported spectral efficiency of 10 bit/s/Hz with a polarizationmultiplexed FDM transmission of 128 QAM signals [4]. Moreover, QAM multiplicity has recently been increased to 256, and 64 Gbit/s data have been transmitted at 4 Gsymbol/s in a 5.4 GHz optical bandwidth [5].…”

Characterization of a high coherence, Brillouin microcavity laser on silicon

“…Ultra-high coherence (low frequency noise) is a priority in a remarkably wide range of applications including: high-performance microwave oscillators [1], coherent fiber-optic communications [2,3], remote sensing [4] and atomic physics [5,6]. In these applications, the laser forms one element of an overall system that would benefit from miniaturization.…”

“…For example, in coherent communication systems a laser (local oscillator) works together with taps, splitters and detectors to demodulate information encoded in the field amplitude of another coherent laser source. Therein, narrow-linewidth lasers increase the number of information channels that can be encoded as constellations in the complex plane of the field amplitude [2,3]. In yet another example, the lowest, close-to-carrier phase-noise microwave signals are now derived through frequency division of a high-coherence laser source using an optical comb as the frequency divider [1].…”

Stop-and-Go Algorithm for Blind Equalization in QAM Single-Carrier Coherent Optical Systems

“…Single-carrier polarization-multiplexed quadrature phase-shift keying (QPSK) is by now the best-established format for the upcoming 100-Gb/s systems [3]- [5]. Research is now addressing the 400-Gb/s or even 1-Tb/s systems [6], with a large variety of proposed solutions from orthogonal frequency-division multiplexing (OFDM) [7], to subcarrier multiplexing (SCM) [8], from novel modulation formats [9], to classical high-order modulations, like multilevel quadrature amplitude modulations (QAMs) [10], [11]. Predictably, the first efforts have been directed to the feasibility analysis of the wellknown QAM formats, which require a proper modulator, are more sensitive to phase noise and frequency offset, and, obviously, are less energy-efficient than simple QPSK schemes [12].…”