Dual-polarization OFDM-OQAM for communications over optical fibers with coherent detection

Abstract

Abstract:In order to improve the spectral efficiency of coherent optical communication systems, it has recently been proposed to make use of the orthogonal frequency-division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). Multiple optical channels spaced in the frequency domain by the symbol rate can be transmitted orthogonally, even if each channel overlaps significantly in frequency with its two adjacent channels. The solutions proposed until now in the literature unfortunately only address a single polarization communication, and therefore do not benefit from the capacity gain reached when two polarizations are used to transmit independent information signals. The aim of the present paper is to propose a receiver architecture that can decouple the two polarizations. We build an equalizer per channel at twice the symbol rate and optimize it based on the minimum mean square error (MMSE) criterion. We demonstrate the efficiency of the resulting system compared to the Nyquist wavelength-division multiplexing (N-WDM) system both in terms of performance and complexity. We also assess the system sensitivity to transmit synchronization errors and show that system can even work under significant synchronization errors.

Visible light communication using DC-biased optical filter bank multi-carrier modulation

“…Research projects employing FBMC in radio frequency (RF) and fibre-optical communications have been reported in literature [8]- [10]. However, to the best of the authors' knowledge, the viability of using FBMC in VLC channel has not been experimentally verified.…”

“…However, to the best of our knowledge, its superiority compared with conventional DCO-OFDM in VLC channels has not been verified. Previous works such as [8] and [9] implemented OQAM-OFDM as a method to eliminate the use of CP and increase the spectral efficiency of the system. They focused on using either raised cosine or root-raised cosine filters, but the improvement on their side-lode attenuation performances is relatively minor (Fig.…”

Multicarrier Offset-QAM Modulations for Coherent Optical Communication Systems

“…In our approach, the LMS equalizer was initialized by the channel estimate calculated from training sequences. Since the in-phase and quadrature tributaries experience channels that are delayed copies of each other, a purely real equivalent channel model was employed as described in [2]. Using the training sequences and this channel model, the minimum mean square error equalizer (MMSE) was derived at two samples per symbol using odd/even samples separately (polyphase decomposition).…”

Low-Complexity Blind Phase Search for Filter Bank Multicarrier Offset-QAM Optical Fiber Systems

“…Filter bank multicarrier offset quadrature modulation format (FBMC-OQAM) is an interesting alternative to orthogonal frequency-division multiplexing (OFDM) and has recently received much attention in optical fiber communication systems [1][2][3] thanks to its optimized spectral efficiency (SE) and its robustness to the channel variation in optical fibers. On each subcarrier of FBMC-OQAM systems, a half-symbol time delay between the inphase and quadrature components of the signal is introduced, in order to achieve the orthogonality between adjacent subcarriers [4].…”