Spectrally efficient polarization multiplexed direct-detection OFDM system without frequency gap

Chia Chien Wei, Wei Siang Zeng, Chun-Ting Lin

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We experimentally demonstrate a spectrally efficient directdetection orthogonal frequency-division multiplexing (DD-OFDM) system. In addition to polarization-division multiplexing, removing the frequency gap further improves the spectral efficiency of the OFDM system. The frequency gap between a reference carrier and OFDM subcarriers avoids subcarrier-to-subcarrier beating interference (SSBI) in traditional DD-OFDM systems. Without dynamic polarization control, the resulting interference after square-law direct detection in the proposed gap-less system is polarization-dependent and composed of linear inter-carrier interference (ICI) and nonlinear SSBI. Thus, this work proposes an iterative multiple-input multiple-output detection scheme to remove the mixed polarization-dependent interference. Compared to the previous scheme, which only removes ICI, the proposed scheme can further eliminate SSBI to achieve the improvement of ∼ 7 dB in signal-to-noise ratio. Without the need for polarization control, we successfully utilize 7-GHz bandwidth to transmit a 39.5-Gbps polarization multiplexed OFDM signal over 100 km.

Original languageEnglish
Pages (from-to)1823-1828
Number of pages6
JournalOptics Express
Issue number2
StatePublished - 25 Jan 2016

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