Rafael Rios-Müller

Spectrally Efficient 1-Tb/s Transceivers for Long-Haul Optical Systems

We report on the generation and the transmission of 1-Tb/s superchannels for long-haul optical systems. Based on a multicarrier approach, we optimize the design of coherent transceivers at 1-Tb/s while varying the modulation formats together with code rate of soft-decision forward error correction. Through long-haul transmission experiments, we validate our optimum design and highlight the tradeoff between spectral efficiency and maximum transmission reach for 1-Tb/s optical transport. We also report on the transmission impairments suffered by spectrally efficient 1-Tb/s superchannels under the constraints of legacy optical networks using test bed made of 100 km long spans of SSMF and standard 50-GHz slots WSS.

Joint coding rate and modulation format optimization for 8QAM constellations using BICM mutual information

We compare the BICM mutual information of different 8QAM constellations and we show that Circular-8QAM is attractive for high coding rates while quadrature optimized Rect-8QAM provides best performance for low coding rates, both outperforming Star-8QAM.

Single Carrier 168-Gb/s Line-Rate PAM Direct Detection Transmission Using High-Speed Selector Power DAC for Optical Interconnects

We demonstrate the generation and detection of single-polarization 56-GBd PAM-8 and PAM-4 signals using intensity modulation and direct detection leveraging a novel high-speed high-output swing selector power DAC fabricated in an InP DHBT which does not require an external driver. Considering 7% overhead hard-decision forward error control, we validate our design by transmitting the 150 Gb/s net data rate signal based on PAM-8 over 2 km and 100 Gb/s signal based on PAM-4 over 4 km of standard single mode fiber without optical amplification. We complement the results by taking advantage of the high bandwidth of the selector power DAC to increase the PAM-4 symbol rate to 64 GBd and we compare it with the results at 56 GBd at constant information rate. We use the concept of mutual information to assess which Baud rate can achieve best sensitivity as a function of transmission distance.

Optimized spectrally efficient transceiver for 400-Gb/s single carrier transport

We demonstrate a single carrier modulated 400-Gb/s transceiver, leveraging an optimization procedure of inter-symbol interference mitigation and forward error correction. We validate its design by transporting five channels over 6600-km with 6-bit/s/Hz spectral efficiency.

Transmission of single-carrier Nyquist-shaped 1-Tb/s line-rate signal over 3,000 km

We synthesize a single-carrier optical signal at a record 1-Tb/s line-rate, out of multiple spectral slices by joint optical and digital signal processing. The 127.9-GBd signal is successfully transmitted and detected after 3,000km distance.

Spectrally-Efficient 400-Gb/s Single Carrier Transport Over 7 200 km

Since the advent of wavelength division multiplexed optical systems, increasing the bit rate per optical carrier has proved to be the most effective method to drive the overall cost of optical systems down. However, multicarrier approaches have gained momentum for 400-Gb/s transport to cope with bandwidth limitations of optoelectronic components. In this paper, single carrier modulated 400-Gb/s transport over transatlantic distances is demonstrated for the first time. Using high-speed digital-to-analog converters, we successfully generated a 64 GBaud dual-polarization signal modulated using 16-ary quadrature amplitude modulation. Thanks to Nyquist pulse shaping, our channels are closely packed with 66.7 and 75 GHz channel spacing, resulting on 6 and 5.33-bit/s/Hz of spectral efficiencies, respectively. Transceiver design is based on an optimization procedure of inter-symbol interference mitigation and forward error correction overhead. A spatially-coupled low density parity check code with decoder-aware degree optimization is used to reduce the gap to capacity. We validated our transceiver design by transporting five channels over 6600 and 7200-km with 6 and 5.33-bit/s/Hz of spectral efficiency, respectively. We analyze as well the performance gain provided by non-linear mitigation using filtered digital back-propagation algorithm.

Performance Prediction of Nonbinary Forward Error Correction in Optical Transmission Experiments

In this paper, we compare different metrics to predict the error rate of optical systems based on nonbinary forward error correction (FEC). It is shown that an accurate metric to predict the performance of coded modulation based on nonbinary FEC is the mutual information. The accuracy of the prediction is verified in a detailed example with multiple constellation formats and FEC overheads, in both simulations and optical transmission experiments over a recirculating loop. It is shown that the employed FEC codes must be universal if performance prediction based on thresholds is used. A tutorial introduction into the computation of the thresholds from optical transmission measurements is also given.

Compact InP-Based DFB-EAM Enabling PAM-4 112 Gb/s Transmission Over 2 km

We demonstrate a 56-GBd pulse-amplitude modulation-4 compact InP transmitter module integrating a distributed feedback laser and an electro-absorption modulator, which exhibits 50-GHz bandwidth, >13-dB extinction ratio and up to 1.5-mW output power. Successful amplifier-free 112-Gb/s transmission is performed over 2 km using low complexity three-taps equalization. We also study the tradeoff between receiver bandwidth, equalizer length and performance, and show successful signal recovery with bandwidths as low as 18 GHz when increasing the equalizer length.

Direct detection transceiver at 150-Gbit/s net data rate using PAM 8 for optical interconnects

We demonstrate a single-polarization driver-free, direct-detection 56-GBaud PAM-8 transceiver enabled by a high-speed selector power DAC fabricated in InP DHBT, and successfully transmit 168 Gbit/s line-rate over 2 km distance without optical amplification.

Blind Receiver Skew Compensation and Estimation for Long-Haul Non-Dispersion Managed Systems Using Adaptive Equalizer

Imbalances between the four sampling channels of a coherent detector with polarization diversity can rapidly degrade system performance. One of these imbalances, namely the receiver skew, becomes increasingly important when higher symbol rates, higher modulation orders, and low roll-off pulse shapes are used. Here, we evaluate the performance of receiver skew compensation based on a complex-valued multiple-input multiple-output 4 × 2 adaptive equalizer that is tolerant to large residual chromatic dispersion. In addition, we derive skew estimation from converged equalizer taps. Both the adaptive equalizer and the derived estimator are validated experimentally with offline processing through long-haul transmission of 46 Gbaud signal over a non-dispersion-managed test bed. The transmitted signal is Nyquist pulse shaped with a root-raised-cosine filter with 0.1 roll-off factor, polarization division multiplexed, and modulated with 16-ary quadrature amplitude modulation.