Simplified DSP-Based Signal–Signal Beat Interference Mitigation Technique for Direct Detection OFDM

Abstract

Short-and medium-haul links in inter-data center, access, and metro networks require cost-effective direct-detection (DD) wavelength division multiplexing (WDM) transceivers offering energy efficiency, high information spectral density (ISD) and dispersion tolerance. Single-sideband orthogonal frequency division multiplexing (SSB-OFDM) with direct detection is a potential solution; however, it suffers a penalty from signal-signal beat interference (SSBI) caused by the square-law photodetection. In this paper, a novel DSP-based SSBI mitigation technique, with lower complexity than previously proposed methods, is proposed and assessed through numerical simulations for the first time. The performance improvement is quantified by simulations of 9 × 112 Gb/s 16-QAM SSB-OFDM signal with a net optical ISD of 2.1 (b/s)/Hz. The performance is shown to be similar to that of the more complex receiver-based iterative SSBI compensation technique. Simulations predict an 8.7 dB reduction in the required OSNR at the 7% overhead HD-FEC threshold, and increases of up to 100% in maximum reach over uncompensated standard singlemode fibre (SSMF) using the proposed simplified SSBI compensation technique.

Digital Linearization of Direct-Detection Transceivers for Spectrally Efficient 100 Gb/s/λ WDM Metro Networking

“…The compensation works by calculating these terms and subtracting them from the detected signal. Unlike the SSBI estimation and cancellation schemes [20,22,23,26], since the calculation of the SSBI terms is carried out directly from the detected signal rather than from a reconstruction of it based on symbol decisions, the linearization filters offer significantly reduced DSP complexity, and avoid the need for accurate symbol decision making when reconstructing the beating terms. In the single-stage linearization filter (Fig.…”

“…Fortunately, recently demonstrated digital linearization techniques have been shown to be effective in reducing the SSBI penalties, allowing the use of narrow or even no spectral guard-band, without requiring a change to the single photodiode-based optical hardware design [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Experimental Demonstration of a Real-Time Digital Filter Multiple Access PON With Low Complexity DSP-Based Interference Cancellation

“…The optical signals from the ONUs are combined in a 3dB passive optical coupler, representing the remote node of the PON, before the optically combined signal is launched into a 26km SSMF. Both ONUs operate at a nominal wavelength of 1550nm, however a wavelength spacing of 0.3nm is employed to avoid the direct-detection (DD)-induced optical beat interference (OBI) effect [16], in practice wavelength control can be achieved by laser thermal detuning [17] or alternative OBI mitigation methods [18][19] may be employed after suitable modifications. For experiments involving a PTP configuration, ONU1 and the 3dB optical coupler are omitted so that ONU2 connects directly to the 26km SSMF link.…”