Reduced Equalization Needs of 100 GHz Bandwidth Plasmonic Modulators

As bit rates of optical interconnects increase, a large amount of complicated signal conditioning is needed to compensate for the insufficient bandwidth of current modulators. In this paper, we evaluate the reduced equalization requirements of high-bandwidth plasmonic modulators in short-reach transmission experiments. It is shown that transmission of 100 Gbit/s nonreturn-to-zero (NRZ) and 112 Gbit/s pulse-amplitude modulation4 over 1 km and 2 km distance is possible without any receiver equalization. At higher bit-rates, such as 120 Gbit/s NRZ, data transmission is demonstrated over 500 m with reduced receiver equalization requirements. Transmission up to 200 Gbit/s over 1 km is also shown with more complex receiver equalization. The reduced complexity of the receiver digital signal processing is attributed to a flat frequency response of at least 108 GHz of the plasmonic modulators. All single wavelength transmissions have been performed at 1540 nm in standard single mode fiber

Modified Godard Timing Recovery for Non Integer Oversampling Receivers

A timing recovery algorithm is introduced that operates with less than two samples per symbol and provides an enormous complexity reduction. The complexity reduction is due to a synergy with the already existing Fourier transforms in a coherent receiver, an avoidance of terms that are dominated by noise, and a complete elimination of multiplications. A simulation and an experiment with a single carrier modulation format show that the inherent timing jitter is, despite of the significant complexity reduction, comparable with the state of the art, and in particular outperforms the Godard algorithm for low roll-off factors. In addition, it is one of the few algorithms that operates with less than two samples per symbol in the frequency domain, and thus enables the lowest complexity in a receiver

Optical Transmitters without Driver Amplifiers—Optimal Operation Conditions

ISSN:2076-341

Optical Transmitters without Driver Amplifiers—Optimal Operation Conditions

An important challenge in optical communications is the generation of highest-quality waveforms with a Mach–Zehnder modulator with a limited electrical swing (Vpp). For this, we discuss, under limited Vpp, the influence of the waveform design on the root-mean-square amplitude, and thus, the optical signal quality. We discuss the influence of the pulse shape, clipping, and digital pre-distortion on the signal quality after the electrical-to-optical conversion. Our simulations and experiments, e.g., suggest that pre-distortion comes at the expense of electrical swing of the eye-opening and results in a lower optical signal-to-noise ratio (OSNR). Conversely, digital post-distortion provides operation with larger eye-openings, and therefore, provides an SNR increase of at least 0.5 dB. Furthermore, we find that increasing the roll-off factor increases the electrical swing of the eye-opening. However, there is negligible benefit of increasing the roll-off factor of square-root-raised-cosine pulse shaped signals beyond 0.4. The findings are of interest for single-channel intensity modulation and direct detection (IM/DD) links, as well as optical coherent communication links

Modified Godard Timing Recovery for Non-Integer Oversampling Receivers

A timing recovery algorithm is introduced that operates with less than two samples per symbol and provides an enormous complexity reduction. The complexity reduction is due to a synergy with the already existing Fourier transforms in a coherent receiver, an avoidance of terms that are dominated by noise, and a complete elimination of multiplications. A simulation and an experiment with a single carrier modulation format show that the inherent timing jitter is, despite of the significant complexity reduction, comparable with the state of the art, and in particular outperforms the Godard algorithm for low roll-off factors. In addition, it is one of the few algorithms that operates with less than two samples per symbol in the frequency domain, and thus enables the lowest complexity in a receiver.ISSN:2076-341