Erik De Man

Ultralong haul 1.28-Tb/s PM-16QAM WDM transmission employing hybrid amplification

In order to cope with the foreseeable capacity crunch next-generation optical transmission systems aim to utilize higher order quadrature amplitude modulation formats to achieve spectral efficiency (SE) higher than the current commercial systems. In particular, transmission rates as high as 1 Tb/s are envisioned, employing superchannel configuration achieved by closer than standard 50 GHz placement of Nyquist filtered wavelength-division multiplexed (WDM) channels. Moreover, increase in symbol rate of each subcarrier in a superchannel is desired to reduce the number of components per Tb/s and, consequently, overall cost. In this regard, we addressed a series of challenges namely intersymbolinterference (ISI) induced by low-pass filtering of digital-to-analog converter (DAC), intrasuperchannel crosstalk penalties, and selected suitable forward error correction (FEC) code considering limitations of electronic components. Digital preemphasis is employed to mitigate DAC induced ISI, a subcarrier spacing of 1.2 × symbol rate is chosen to limit crosstalk penalties below 0.5 dB in Q2 and a FEC overhead of 23% is established limiting transponder count to four, achieving 1 Tb/s net data rate. The superchannel is assigned a 200-GHz optical spectrum to achieve a SE of 5.0 b/s/Hz, and WDM transmission performance is evaluated over three different kinds of fibers: standard single-mode fiber (SSMF), large area pure silica core fiber (LAPSCF), and large effective area fiber (LEAF), having span lengths of 95/121, 82/164, and 81 km, respectively. The maximum reach of 1-Tb/s superchannel with 8 × 100-Gb/s WDM channels at pre-FEC threshold of 3.37 × 10-2 was found to be 1110, 1921, and 789 km for SSMF, LAPSCF, and LEAF, respectively. Further improvement in transmission performance is achieved by employing hybrid EDFA-Raman amplification, and achievable distance was extended to 2054, 2952, and 1341 km for SSMF, LAPSCF, and LEAF, respectively, at pre-FEC threshold. Mitigation of a nonlinear phase noise employing single-channel digital back propagation resulted in extension of maximum reach up to 2262, 3349, and 1530 km for SSMF, LAPSCF, and LEAF, respectively.

Joint adaptive pre-compensation of transmitter I/Q skew and frequency response for high order modulation formats and high baud rates

We present a digital algorithm for joint pre-compensation of the low-pass frequency response and I/Q skew in transmitters. Experimental results for DP-16QAM to DP-256QAM at 37.41 GBaud are presented.

A Robust Adaptive Pre-Distortion Method for Optical Communication Transmitters

Present and next generation optical communication systems are constantly being developed to operate at higher baud rates and higher modulation formats. It then becomes inevitable to consider the various linear and nonlinear effects due to the imperfect components at the transmitter. State-of-the-art digital-to-analog converters, high bandwidth driver amplifiers, and dual-polarization (DP) Mach-Zehnder modulators are far from being ideal and present distortions in the form of bandwidth limitation, transmitter I/Q skew, and nonlinear effects. In this letter, we propose a new robust pre-distortion method to mitigate the undesirable linear and non-linear distortions of all electrical and optical transmitter components simultaneously. A step-by-step derivation and implementation of the algorithm are discussed and put forward. The performance of the algorithm is experimentally assessed across DP-4QAM, DP-8QAM, DP-16QAM, DP-32QAM, and DP-64QAM up to the signaling rates of 56 GBd. Significant improvements in the required optical signal-to-noise ratio at bit-error rate (BER) of 10-2 are demonstrated.

Record field demonstration of C-band multi-terabit 16QAM, 32QAM and 64QAM over 762km of SSMF

We demonstrate a record 38.4Tb/s 64QAM C-band transmission over 762km of field deployed SSMF fiber, connecting Lyon and Marseille, France, employing hybrid EDFA-Raman amplification and achieve a spectral efficiency of 8b/s/Hz. Furthermore, we demonstrate, for the first time to our knowledge, flexi-rate transmission over the same commercial link, using quad-carrier 1Tb/s 16QAM (24.0 Tb/s), 1Tb/s 32QAM (32.0 Tb/s) and 1.2Tb/s 64QAM (38.4 Tb/s).

Data transmission through up to 74.8 km of hollow-core fiber with coherent and direct-detect transceivers

An optical transmission loop experiment over hollow-core fiber is demonstrated with 1.25Gb/s OOK, 40G DP-QPSK, 100G DP-QPSK modulation schemes over distances of 31.0 km, 74.8 km, 55.8 km respectively, using two fiber spans with 2.7 km and 3.5 km length.

9.6Tb/s CP-QPSK Transmission Over 6500 km of NZ-DSF With Commercial Hybrid Amplifiers

We experimentally demonstrate, for the first time to the best of our knowledge, an ultralong-haul dense wavelength division multiplexed transmission of 96 × 100Gb/s coherent polarization multiplexed quadrature phase-shifted keying transponders over ITU-T G.655 nonzero dispersion-shifted large effective area fibers (NZ-DSF) with an effective core area of 72 μm2, employing both commercial erbium-doped fiber amplifiers (EDFA) and hybrid EDFA + Raman amplification systems. Using the state-of-the-art digital pulse shaping and digital preemphasis algorithms, we report ~1.5dB back-toback optical signal-to-noise ratio penalty at pre forward error correction (FEC) bit error rate (BER) threshold (3.8 × 10-2), with respect to theoretical performance. In particular, we demonstrate ~6500km transmission across the entire C-band, at pre-FEC BER of 3.8 × 10-2, employing EDFA + backward Raman amplification-where the central channel (1552.2nm) had sufficient margin to enable transmission of up to ~8000km. Furthermore, we report that hybrid amplification enables up to ~60% improvement in maximum transmission reach, compared to EDFA based links. To the best of our knowledge, a record capacity-distance product of ~62.4 Pb/s·km is achieved for NZ-DSF-an 11-fold increase, compared with the previous literature.

Data-aided single-carrier coherent receivers

Data-aided algorithms for coherent optic receivers are discussed as an extension of existing non-data aided methods. The concept presents a scalable approach with low implementation complexity and limited overhead for higher-order modulation formats.

Multi-flex field trial over 762km of G.652 SSMF using programmable modulation formats up to 64QAM

We demonstrate next-generation network upgrade scenarios using flexi-format (PM-QPSK→PM-64QAM) and flexi-rate (100G→300G) transmission over field-deployed fiber (762km). The back-to-back penalties are limited to ~2.6dB, whereas after transmission, available margin in excess of ~7.6dB is reported.

A memory polynomial based adaptive digital pre-distorter for optical communication transmitters

We present a robust adaptive digital pre-distortion technique to mitigate the linear and non-linear degradation of optical communication transmitter components. The proposed method is based on the principles of memory polynomial based pre-distortion and indirect learning architecture. Effectiveness of the presented algorithm is assessed across various higher order modulation formats and higher baud rates. Significant gains are reported in back-to-back measurements and various lab and field trial experiments.

Simulation and verification of a multicore fiber system

In this paper, a simulation model of a multicore fiber in the linear regime is presented. We describe how to digitally represent the fiber and introduce a modelling scheme based on Coupled-Mode theory and Power-Coupled theory to analyze the system performance of multicore fibers. In order to validate the investigated model, the obtained simulation results are compared to our own measurements of a 7-core multicore fiber transmission link and to results from previously published experiments.