Chromatic dispersion mitigation in long-haul fiber-optic communication networks by sub-band partitioning

Abstract

We propose and experimentally demonstrate a novel sub-band multiplexed data architecture for chromatic dispersion (CD) mitigation. We have demonstrated 32 GBaud multi-sub-band (MSB) dual-polarization (DP) 16QAM transmission over 2400 km. Using this approach, the transmitted signal bandwidth is divided into multiple narrow-bandwidth sub-bands, each operating at a lower baud rate. Within each sub-band bandwidth, the CD frequency response can be approximated as a linear-phase band-pass filter, which can be considered as an analog delay that does not require compensation. Therefore, the resulting receiver digital signal processing (DSP) is simplified due to the removal of the CD compensation equalizer. In addition, this leads to efficient parallelization of DSP tasks by deploying multiple independent sub-band processors running at a lower clock rate. The proposed system reduces receiver computational complexity and offers 1 dB higher Kerr-nonlinearity tolerance and 2% extended transmission reach in comparison to the conventional single carrier systems.

Sub-band-based transmission for mode-multiplexed optical systems

“…Both figures indicate a systematic BER penalty in the MSB transceiver compared with the SC option after convergence. This penalty has been also observed in previous works with MSB systems, and can be attributed to interference among neighbouring sub-bands [4]. Figure 4 shows the optical signal to noise ratio (OSNR) required to achieve a BER of 4e-3, versus number of equalizer filter taps, for different configurations.…”

“…This idea has been validated in conventional polarization multiplexed systems (PM) transmission using a computationally-efficient structure with polyphase filters (called in the paper a twice-underdecimated filter bank) [3]. The technique has been applied to mitigate chromatic dispersion (CD) [4] and non-linear effects [5]. Polyphase filter bank architectures have also been employed in the context of MIMO equalization for MMFs in [6], where the twiceunderdecimated filter bank architecture was adapted to achieve fast convergence in an orthogonal frequency division multiplexing (OFDM) system with weakly coupled spatial channels.…”

“…We focus on a transceiver design based on Nyquist-shaped subcarriers generated by a common prototype filter, as proposed in [3] [4]. Compared with OFDM, this architecture exhibits the advantage of avoiding bandwidth consumption due to cyclic prefixes.…”

“…The modulated complex sequence is then parallelized into an odd number of streams (Nsb). The DFT-based polyphase filter bank is implemented with Nsb+1 data streams, where the stream in position (Nsb+1)/2+1 contains zeros to avoid edge effects [4]. A root-raised cosine (RRC) filter is used as prototype.…”

Mitigation of transceiver bandwidth limitations using multi-subcarrier signals

“…These techniques have been proposed for single-carrier Nyquist-shaped transmission systems with high symbol-rates exceeding 32 GBaud and high-order modulation formats. As an alternative to singlecarrier transceivers, electronic subcarrier-multiplexing has been recently attracting the attention of the optical communications community due to its inherent advantages in term of robustness to chromatic dispersion [5] and nonlinear impairments [6], [7]. While the standard pre-emphasis filtering techniques can also be applied to electrical subcarrier-multiplexing signals by processing all subcarriers as a single entity, new opportunities arise on the design of pre-emphasis techniques that treat each subcarrier independently.…”