Abstract
The growing data demands are pushing researchers to pay more attention to spectrally efficient modulation formats. The four-dimensional (4D) signal constellation modulation format has been investigated for metro networks’ applications to achieve better power efficiency. To cope with such modulation formats, the requirement of better digital signal processing (DSP) is also increasing rapidly. More complicated DSPs bring us extra costs; thus, the DSP-free coherent receivers are also investigated because of the high-power consumption of conventional DSP-based receivers, but the transceivers upgrading also results in extra costs. In this invited paper we implement a 4-dimentional modulation format based on Slepian sequences. We applied LDPC coding and experimentally investigated the BER performance in a two-dimensional (2D) 40 km fiber link transmission and demonstrate that being error free is possible without employing the complicated DSP. We compared our proposed modulation scheme with regular 16QAM and found it outperforms 16QAM with DSP over back-to-back transmission by 3.8 dB improvement in OSNR when BER = 10−5, while over 40 km metro network communication link our proposed 4D modulation signals are still successfully transmitted, and the LDPC-coding still works properly with such a new transmission strategy. On the other hand, DSP-free transmission of LDPC-coded 16-QAM exhibits an early error floor phenomenon.
Highlights
Academic Editor: Luis VelascoThe never-ending demands for higher data rates always exist in a variety of industry fields, which require significant efforts to satisfy the growing data demands and to deal with the incoming bandwidth capacity crunch [1–3], pushing researchers to pay more attention to spectrally efficient modulation formats [4]
The terabit optical Ethernet technologies will be affected by security issues, and to solve such problem, the properly designed fiber Bragg gratings (FBGs) application in impulse responses derived from mutually orthogonal Slepian sequences has been advocated in [1] to enable positive rate to convert optical communications [2,3]
We apply the Slepian sequences-based basis functions to a 16points 4D modulation format, combined with the low-density parity-check (LDPC) coding for 40 km metro network transmission
Summary
The never-ending demands for higher data rates always exist in a variety of industry fields, which require significant efforts to satisfy the growing data demands and to deal with the incoming bandwidth capacity crunch [1–3], pushing researchers to pay more attention to spectrally efficient modulation formats [4]. The constellation shaping scheme, both probabilistic shaping (PS) and geometric shaping (GS), are broadly applied to reduce the gap of channel capacity to Shannon limit, which require specified DSP scheme to optimize the performance [28,29] These increasing demands of DSP costs have led researchers to pay more attention to the DSP-free coherent receivers [30–33]. The terabit optical Ethernet technologies will be affected by security issues, and to solve such problem, the properly designed fiber Bragg gratings (FBGs) application in impulse responses derived from mutually orthogonal Slepian sequences has been advocated in [1] to enable positive rate to convert optical communications [2,3] In this invited paper, we apply the Slepian sequences-based basis functions to a 16points 4D modulation format, combined with the LDPC coding for 40 km metro network transmission.
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