Abstract
A number of critical issues for dual-polarization single- and multi-band optical orthogonal-frequency division multiplexing (DP-SB/MB-OFDM) signals are analyzed in dispersion compensation fiber (DCF)-free long-haul links. For the first time, different DP crosstalk removal techniques are compared, the maximum transmission-reach is investigated, and the impact of subcarrier number and high-level modulation formats are explored thoroughly. It is shown, for a bit-error-rate (BER) of 10(-3), 2000 km of quaternary phase-shift keying (QPSK) DP-MB-OFDM transmission is feasible. At high launched optical powers (LOP), maximum-likelihood decoding can extend the LOP of 40 Gb/s QPSK DP-SB-OFDM at 2000 km by 1.5 dB compared to zero-forcing. For a 100 Gb/s DP-MB-OFDM system, a high number of subcarriers contribute to improved BER but at the cost of digital signal processing computational complexity, whilst by adapting the cyclic prefix length the BER can be improved for a low number of subcarriers. In addition, when 16-quadrature amplitude modulation (16QAM) is employed the digital-to-analogue/analogue-to-digital converter (DAC/ADC) bandwidth is relaxed with a degraded BER; while the 'circular' 8QAM is slightly superior to its 'rectangular' form. Finally, the transmission of wavelength-division multiplexing DP-MB-OFDM and single-carrier DP-QPSK is experimentally compared for up to 500 Gb/s showing great potential and similar performance at 1000 km DCF-free G.652 line.
Highlights
Optical orthogonal frequency-division multiplexing (OFDM) is a very promising multicarrier technique for long-haul transmissions [1] due to its high spectral efficiency and robust chromatic dispersion (CD) and polarization-mode dispersion (PMD) tolerance
In contrast to Nyquist-wavelength-division multiplexing (WDM) [15], MB-OFDM technology does not require complex digital signal processing (DSP) to mitigate signal distortion induced by the transceivers filtering and the reconfigurable optical add-drop multiplexers (ROADMs) cascadability is more efficient
After having answered to the aforementioned statement in [12,13,14], where it was shown that 100 Gb/s DP-MB-OFDM and single-carrier DP-quaternary phase-shift keying (QPSK) have nearly the same performance after 10 × 100 km of G.652 fiber; here, we thoroughly explore the DP-MB-OFDM transmission and transceiver limitations to maximize performance
Summary
Optical orthogonal frequency-division multiplexing (OFDM) is a very promising multicarrier technique for long-haul transmissions [1] due to its high spectral efficiency and robust chromatic dispersion (CD) and polarization-mode dispersion (PMD) tolerance. We focus on the theoretical aspects of multiple-input multiple-output (MIMO) equalization methods It is shown for a target bit-error-rate (BER) of 10−3, 2000 km QPSK coherent DP-MBOFDM of transmission is feasible. By adopting a high signal modulation format (i.e. 16 quadrature amplitude modulation [16QAM]), the DAC/ADC bandwidth is relaxed with the cost of BER degradation; whereas the ‘circular’ 8QAM is slightly superior to its ‘rectangular’ form. It is experimentally revealed and numerically verified that 500 Gb/s WDM DP-MB-OFDM and WDM single-carrier DP-QPSK have similar transmission performance at 1000 km DCF-free G.652 fiber line
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