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We demonstrate a 222 GBd on-off-keying transmitter in a short-reach intra-datacenter scenario with direct detection after 120 m of standard single mode fiber. The system operates at net-data rates of >200 Gb/s OOK for transmission distances of a few meters, and >177 Gb/s over 120 m, limited by chromatic dispersion in the standard single mode fiber. The high symbol rate transmitter is enabled by a high-bandwidth plasmonic-organic hybrid Mach–Zehnder modulator on the silicon photonic platform that is ribbon-bonded to an InP DHBT 2:1 digital multiplexing selector. Requiring no driving RF amplifiers, the selector directly drives the modulator with a differential output voltage of 622 mVpp measured across a 50 Ω resistor. The transmitter assembly occupies a footprint of less than 1.5 mm × 2.1 mm. [ABSTRACT FROM AUTHOR]

As optical transceivers evolve toward 200G per lane, the comparatively low bandwidth and sampling speed of the commercially available high-speed digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) increasingly become the dominating obstacle toward success. On the other hand, DACs and ADCs are essential to make use of digital signal processing for impairment compensation and error correction; altogether driving systems’ engineers to a hard design dilemma. With the purpose of alleviating this compromise, we propose a transceiver structure—encompassing both hardware and software—enabling the generation, transmission, and detection of strongly over-filtered data signals whose baudrate exceeds the sampling rates of (potentially) both the DAC and ADC. We call this approach sub-baudrate sampling, a technique which does not increase the processing complexity at the transmitter side and does not even require the information about the channel state for pre-distortion or pre-coding purposes. We experimentally assess the performance of sub-baudrate sampled signals in two blocks of experiments: first the proof of concept in back-to-back configuration, including up to 112-Gbaud on–off keying at 0.785 samples per symbol in ∼25-GHz aggregate bandwidth. Then the C-band transmission demonstration, showing up to 100-Gbaud quaternary pulse-amplitude modulation (0.92 samples per symbol) and 125-Gbaud on–off keying (0.736 samples per symbol) over 1 and 80-km of single-mode fiber, respectively, with more than 3-dB receiver sensitivity margin at the 7% overhead hard-decision bit error rate limit. [ABSTRACT FROM AUTHOR]

We report on an ultrahigh-speed PAM-based IM/DD optical subsystem featuring compact signal generation and tractable digital-processing complexity. The proposed transceiver is based on two main technologies: an InP DHBT selector power DAC for electrical signal generation, and a complexity-optimized receiver processing chain. We show how the complexity of the feed-forward equalizer can be considerably reduced by stacking a <3-symbol memory sequence estimator. Finally, we experimentally demonstrate successful signal recovery for 107-GBd PAM-4 in back-to-back configuration, and after 500 m and 1 km of transmission over standard single-mode fiber for 100- and 84-GBd PAM-4 configuration, respectively. A power-budget margin above 2 dB is attained in all cases. [ABSTRACT FROM PUBLISHER]

We demonstrate for the first time an intensity-modulated direct-detection link using four states of polarization. The four data-independent tributaries are each assigned distinct states of polarization to enable the receiver to separate the signals. Polarization rotation due to propagation over optical fiber is tracked and compensated with simple digital signal processing in Stokes space. Transmission below the forward error correction limit is shown for maximum net bitrates of 100 Gb/s (4$\,\times$  27 GBd) and 120 Gb/s (4$\,\times$ 32 GBd) over 2-km standard single-mode fiber at a center wavelength of 1550 nm. [ABSTRACT FROM PUBLISHER]

A time-reversal array in multimode fiber is proposed for lossless remotely controlled switching using passive optical splitters. The signal to be transmitted is digitally predistorted so that it is routed through the physical layer in order to arrive at only one receiver in an array. The system performance in the presence of an additive white Gaussian noise, modal group delay, and timing error is investigated numerically for single-mode fiber and 10-mode fiber. Focusing using a two-transmitter array and 44 km of single-mode fiber is demonstrated experimentally for 3-GBd QPSK signals with a bit error rate below the forward error correction limit. [ABSTRACT FROM PUBLISHER]

In this paper, joint estimation of carrier frequency, phase, signal means and noise variance, in a maximum likelihood sense, is performed iteratively by employing expectation maximization. The parameter estimation is soft decision driven and allows joint carrier synchronization and data detection. The algorithm is tested in a mixed line rate optical transmission scenario employing dual polarization 448 Gb/s 16-QAM signal surrounded by eight on-off keying channels in a 50 GHz grid. It is shown that joint carrier synchronization and data detection are more robust towards optical transmitter impairments and nonlinear phase noise, compared to digital phase-locked loop (PLL) followed by hard decisions. Additionally, soft decision driven joint carrier synchronization and detection offers an improvement of 0.5 dB in terms of input power compared to hard decision digital PLL based carrier synchronization and demodulation. [ABSTRACT FROM PUBLISHER]