Transmission Performance of 256-Gb/s PDM-16QAM With Different Amplification Schemes and Channel Spacings

Abstract

We experimentally investigate the performance of a 256-Gb/s polarization-division-multiplexed 16-ary quadratureamplitude-modulation (PDM-16QAM) transmission system in dispersion uncompensated TeraWave SLA+ fiber spans using erbium-doped-fiber amplifiers (EDFAs), hybrid EDFA/Raman amplifiers, and all backward-pumped Raman amplifiers. The effects of 37.5-and 50-GHz channel spacings and cascaded optical add/drop multiplexers (ROADMs) on the system performance are studied. We find that when there are no ROADMs, hybrid EDFA/Raman amplifiers and all-backward-pumped Raman amplifiers can increase the reach by about 70% and 100%, respectively, compared to EDFA-only amplifiers, from 2000 to about 3500 and 4200 km, respectively, assuming 20% soft-decision forwarderror-correction (SD-FEC) for the system with both 37.5-and 50-GHz channel spacings. We show that cascaded ROADMs have a small impact on the system with 50-GHz channel spacing, but can severely degrade the performance of the system with 37.5-GHz channel spacing and virtually eliminate the reach gain from Raman amplifiers in such systems due to large penalties and higher error floors induced by ROADM filtering effects. We also show that for the same number of channels, the system with 37.5and 50-GHz channel spacings has similar performance when there are no ROADMs. Index Terms-Coherent detection, fiber nonlinearities, nonlinear transmission, optic fiber communication, Raman amplifiers, reconfigurable optical add/drop multiplexers (ROADMs). 0733-8724

Impact of fiber parameters on EDFA and/or Raman amplified high-spectral-efficiency coherent WDM transmissions

“…In Sec. 2, the analytical methods for approximating the signal power evolution and nonlinearity noise power are described and then confirmed by 10-channel 256-Gb/s PDM-16QAM experiments, which employed three amplification schemes: EDFA only, hybrid EDFA/Raman, and all Raman [14]. In Sec.…”

“…The amplification scheme is indicated by the color of the markers or line, with blue for EDFA only, red for hybrid Raman/EDFA, and magenta for all Raman. Referring to the bit error ratio (BER) vs. OSNR relationship in [14], which provides the noise loaded back-to-back characterization of the 256 Gb/s PDM-16QAM system, the corresponding Q 2 factors of the transmissions were obtained from the calculated OSNRs. A center channel of the WDM comb was chosen for the comparison as it suffered the most from the nonlinearity impairment.…”

“…Here, it is extended to systems that are amplified via hybrid EDFA/Raman or all Raman scheme. In order to accurately assess the performances of such systems, the enhanced Gaussian noise (EGN) model [13], which corrects the nonlinearity noise overestimate of the GN model, is adopted, and the analytical methods employed in this work are checked against experiments [14]. For ease of comparison, this work focuses on 256-Gb/s PDM-16QAM WDM transmissions, using the same bit rate per optical carrier and modulation format as in the experiments [14].…”

“…In order to accurately assess the performances of such systems, the enhanced Gaussian noise (EGN) model [13], which corrects the nonlinearity noise overestimate of the GN model, is adopted, and the analytical methods employed in this work are checked against experiments [14]. For ease of comparison, this work focuses on 256-Gb/s PDM-16QAM WDM transmissions, using the same bit rate per optical carrier and modulation format as in the experiments [14]. The performances of such links of various large-effective-area, low-loss fibers are assessed via the experimentally verified analytical methods, and the corresponding OSNR improvements over a reference system are compared with the FOMs in [8,9,11].…”

Large-Area Low-Loss Fibers and Advanced Amplifiers for High-Capacity Long-Haul Optical Networks [Invited]

“…We have further experimentally investigated the transmission performance of TeraWave fiber in a typical 256 Gb/s PDM-16QAM DWDM system with 37.5 and 50 GHz channel spacing [12]. The 256 Gb/s PDM-16QAM is a promising modulation format for two carrier 400 Gb/s systems due to a relatively simple scheme and maturity of opto-electronic components.…”