Abstract
In this paper, we propose to increase residual carrier frequency offset tolerance based on short perfect reconstruction pulse shaping for coherent optical-orthogonal frequency division multiplexing. The proposed method suppresses the residual carrier frequency offset induced penalty at the receiver, without requiring any additional overhead and exhaustive signal processing. The Q-factor improvement contributed by the proposed method is 1.6 dB and 1.8 dB for time-frequency localization maximization and out-of-band energy minimization pulse shapes, respectively. Finally, the transmission span gain under the influence of residual carrier frequency offset is ~62% with out-of-band energy minimization pulse shape.
Highlights
In the past years, coherent optical-orthogonal frequency division multiplexing (CO-OFDM) has been an attractive technology in high speed communication, due to its inherent advantages of higher resilience towards chromatic dispersion and polarization mode dispersion, flexibility in accessing individual subcarriers in multi-user environment, and a simplified equalization scheme [1]
Li et al [9] introduced pulse shaping with root raised cosine (RRC) in optical OFDM, where RRC has demonstrated some improvements in comparison to rectangular pulse shape for receiver operating under the influence of residual carrier frequency offset (CFO)
We deliberately introduce a residual CFO of 2 MHz and investigate the additional tolerance that can be provided by the proposed pulse shapes
Summary
Coherent optical-orthogonal frequency division multiplexing (CO-OFDM) has been an attractive technology in high speed communication, due to its inherent advantages of higher resilience towards chromatic dispersion and polarization mode dispersion, flexibility in accessing individual subcarriers in multi-user environment, and a simplified equalization scheme [1]. Li et al [9] introduced pulse shaping with root raised cosine (RRC) in optical OFDM, where RRC has demonstrated some improvements in comparison to rectangular pulse shape for receiver operating under the influence of residual CFO. We are introducing short perfect reconstruction (orthogonal) pulse shapes in CO-OFDM, namely time-frequency localization maximization (TFL) and out-of-band energy minimization (OBE), and presenting an opportunity of taking a new approach in providing higher residual CFO tolerance with pure discrete pulse shapes. In the case of implementation, truncation is required for RRC to achieve short pulse shape; the discrete finite impulse response of the RRC pulse shape would not allow perfect reconstruction and will not meet the Nyquist criterion
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