Fiber-Nonlinearity-Tolerant Superchannel Transmission via Nonlinear Noise Squeezing and Generalized Phase-Conjugated Twin Waves

Generation of 1024-Tb/s Nyquist-WDM phase-conjugated twin vector waves by a polarization-insensitive optical parametric amplifier for fiber-nonlinearity-tolerant transmission

“…At the receiver, DCS of the signal and the idler was conducted, and a performance gain of 2.4 dB was observed. We attribute the higher gain (~3.8 dB) observed in the work reported here to the fact that (i) the essential dispersionsymmetry condition needed for achieving the optimal PCTW performance [8] was satisfied in our work, and (ii) the WDM-PCTW approach made one polarization of the entire WDM spectrum to be the phase-conjugated and spectrally-inverted copy of the other polarization, thereby further mitigating inter-channel nonlinear effects [10].…”

“…This indicates that in the presence of large PMD, PCTW transmission is still beneficial in that (i) it uses diversity (via different-wavelength signal and idler) to limit the performance variation, and (ii) it tends to become most effective when the nonlinear distortions are the largest (or when nonlinearity mitigation is most needed) due to small instantaneous DGD. This PCTW approach provides the flexibility of trading half the spectral efficiency with more than 3 dB improvement in performance, leading to system cost savings in certain applications [8,10]. To further verify the performance advantage of DCS of PCTWs as compared to DCS of just signals [17] or idlers, we show in Fig.…”

“…It has been shown that longer transmission distance can be obtained by using lower-level modulation formats with lower spectral efficiency [9]. When the PCTW approach is applied to QPSK signals, it provides more than doubled reach with halved spectral efficiency, which may be beneficial in certain ultra-long-haul applications [10]. A 406.6-Gb/s superchannel consisting of eight QPSK signals, each with its twin wave modulated at the same wavelength but on the orthogonal polarization, was transmitted over a distance of 12,800 km in a TrueWave reduced slope (TWRS) fiber link.…”

“…A 406.6-Gb/s superchannel consisting of eight QPSK signals, each with its twin wave modulated at the same wavelength but on the orthogonal polarization, was transmitted over a distance of 12,800 km in a TrueWave reduced slope (TWRS) fiber link. To further mitigate inter-channel nonlinear impairments, it was suggested to form wavelength-division-multiplexed (WDM) PCTWs where one polarization of the entire WDM spectrum is the phase-conjugated and spectrallyinverted copy of the other polarization [8,10]. To generate such broadband WDM-PCTWs, fiber optic parametric amplifiers (OPAs) [11,12] are well suited.…”

Kerr nonlinearity mitigation in 5 × 28-GBd PDM 16-QAM signal transmission over a dispersion-uncompensated link with backward-pumped distributed Raman amplification

“…In a similar work applied to the nonlinear compensation of a polarization-division multiplexed (PDM) quadrature phase shift keying (QPSK) signal, the signal and its inverted spectrum (a conjugate of the signal also known as idler) were generated at the transmitter and both waves were transmitted through the link to the receiver. The twin waves (signal and idler) were detected at the receiver and the idler was again conjugated before its field was coherently superimposed to the field of the signal via digital signal processing (DSP) to cancel out the nonlinear distortions accumulated on the signal [21,22]. However, the DSP power requirements in a high speed data link dominated by fiber impairments can be significantly high.…”