ABSTRACT
The dependence of propagation performance on the signal baud-rate is investigated by simulations for WDM PDM-16QAM systems operating at a spectral efficiency of 4 b/s/Hz. We take into account the case of transmission over uncompensated links, both for standard single-mode fiber and non-zero dispersion-shifted fiber. Three baud-rates are tested: 16.25, 32.5 and 65 Gbaud, including overhead for soft-decision FEC. Hence, we compare the performance limited by the nonlinear impairments in case of 100, 200 and 400 Gb/s data rate transmission, respectively. We demonstrate that the trade-off between higher OSNR margin and nonlinear transmission penalty favors transmission at lower baud-rate (16.25 Gbaud) and narrower channel spacing (25 GHz), among the three different simulated baud-rates.
ABSTRACT
An empirical phase noise channel model suitable for performance evaluation of high spectrally efficient modulations in 100G long-haul coherent optical transmission systems using polarization-division multiplexed and wavelength-division multiplexing channels is presented. The derivation of the model is worked out by exploiting the similarity between the power spectral density of the carrier extracted from the analysis of propagation measurements and the Lorentzian spectrum that is usually adopted to describe instabilities of semiconductor lasers. The proposed channel model is characterized by only two parameters: the linewidth of the carrier and the signal-to-noise ratio. We show that in the case of quadrature phase-shift keying transmission a good agreement exists between quantitative measures of performance extracted by processing experimental data and those obtained from simulations based on the use of the empirical model.
ABSTRACT
We experimentally investigate the effect of self-phase modulation on direct-detection orthogonal frequency division multiplexed (OFDM) transmission at 11.1 Gb/s over 960km and 1600km uncompensated standard single-mode fiber links. We show that for long-haul systems, the penalties due to nonlinear distortion in OFDM systems are comparable to those in links employing electronic predistortion.
ABSTRACT
The impact of varying the phase relationship between adjacent OTDM channels is investigated in 80 Gbit/s transmission experimentally and numerically. A fiber-based coherent multiplexer is proposed for OTDM experiments - a phase shifter in the multiplexer and an external phase control circuit are used to set and maintain the phase difference. It is demonstrated that the optimum modulation format for maximum transmission distance strongly depends on pulse width, e.g. 120 degrees-RZ provides the best performance for pulse width of 8 ps; however, 90 degrees-RZ is advantageous when pulse width is reduced to 2 ps. Power in 'zero' bit slots and amplitude jitter are calculated to demonstrate that the performance variation is due to intra-channel four-wave mixing (IFWM) and different receiver sensitivity at back-to-back. We also show that phase modulation formats are sensitive to optical filtering.
Subject(s)
Fiber Optic Technology/instrumentation , Signal Processing, Computer-Assisted/instrumentation , Telecommunications/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Models, Theoretical , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Digital signal processing (DSP) combined with a phase and polarization diverse coherent receiver is a promising technology for future optical networks. Not only can the DSP be used to remove the need for dynamic polarization control, but also it may be utilized to compensate for nonlinear and linear transmission impairments. In this paper we present results of a 42.8Gbit/s nonlinear transmission experiment, using polarization multiplexed QPSK data at 10.7GBaud, with 4 bits per symbol. The digital coherent receiver allows 107,424 ps/nm of chromatic dispersion to be compensated digitally after transmission over 6400km of standard single mode fiber.
