Abstract
In this paper, a triple-layer hybrid optical orthogonal frequency division multiplexing (THO-OFDM) for intensity modulation with direct detection (IM/DD) systems with a high spectral efficiency is proposed. We combine $N$ -point asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM), $N$ /2-point ACO-OFDM, and $N$ /2-point pulse amplitude modulated discrete multitoned (PAM-DMT) in a single frame for simultaneous transmission. The time- and frequency-domain demodulation methods are introduced by fully exploiting the special structure of the proposed THO-OFDM. Theoretical analysis show that, the proposed THO-OFDM can reach the spectral efficiency limit of the conventional layered ACO-OFDM (LACO-OFDM). Simulation results demonstrate that, the time-domain receiver offers improved bit error rate (BER) performance compared with the frequency-domain with ~40% reduced computation complexity when using 512 subcarriers. Furthermore, we show a 3 dB improvement in the peak-to-average power ratio (PAPR) compared with LACO-OFDM for the same three layers.
Highlights
In the last decades, the increasing requirement for mobile devices and access to high-speed networks has put additional pressure on the radio-frequency (RF) spectrum usage [1], [2]
We propose a novel spectrum-efficient triple-layer hybrid optical orthogonal frequency division multiplexing (OFDM) (THO-OFDM), which offers a trade-off between ηse and complexity compared with DCO-OFDM
The proposed THO-OFDM can be expressed as: O (THO)-OFDM reached the spectral efficiency limit of the classical LACO-OFDM with only three layers
Summary
The increasing requirement for mobile devices and access to high-speed networks has put additional pressure on the radio-frequency (RF) spectrum usage [1], [2]. Prior to recovering PAM-DMT in the 3rd layer, the clipping interference from ACO-OFDM of the 2nd layer needs to be removed either in the frequency or time domain [30], [33]. The transmitted bits for PAM-DMT in the 3rd layer can be demodulated from the imaginary parts of even subcarriers following the N /2-point FFT operation. Since only the even subcarriers of PAM-DMT are used to carry data information in the proposed scheme, the total spectral efficiency of the proposed THO-OFDM is given by: ηTHO. THO-OFDM could theoretically achieve the spectral efficiency limit of LACO-OFDM with only three layers and the same constellation size
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