56 Gb/s, PAM-4 Transmission Over 25 km, Using IQ Modulator and Unequally Spaced Levels

[EN] We propose a PAM-4 modulation scheme with unequally spaced levels in order to mitigate chirp effects caused by IQ modulators. Experimental results of 56 Gb/s transmission over 25 km link demonstrate the robustness of this modulation concept.Prodaniuc, C.; Stojanovic, N.; Karinou, F.; Goeger, G.; Qiang, Z.; Llorente, R. (2015). 56 Gb/s, PAM-4 Transmission Over 25 km, Using IQ Modulator and Unequally Spaced Levels. Optical Society (OSA). 1-2. https://doi.org/10.1364/CLEO_SI.2015.STu4F.6S1

Experimental Demonstration of Stokes Space Equalization for Space Division Multiplexed Signals

In this letter we experimentally validate, for the first time, the Stokes space algorithm (SSA) equalizer for space division multiplexing (SDM) transmission systems. We introduce the frequency domain (FD)-SSA and FD least-mean square (FD-LMS) algorithms, and evaluate their performance for different frequency offsets by computer simulations. Our simulations show that FD-SSA is insensitive to the frequency offsets, not requiring carrier frequency estimation (CFE) before equalization (pre-CFE) or carrier phase estimation (CPE) inside the loop (L-CPE). Our experimental results confirm that FD-SSA presents the same performance as FD-LMS, where the required digital signal processing (DSP) stack for FD-SSA is simpler compared to the FDLMS

Novel Equalization Techniques for Space Division Multiplexing Based on Stokes Space Update Rule

Space division multiplexing (SDM) is a promising technology that aims to overcome the capacity crunch of optical communications. In this paper, we introduce the multiple-input multiple-output (MIMO) Stokes Space Algorithm (SSA) implemented in frequency domain, a novel equalization technique for space division multiplexing (SDM). Although different papers have been published about the SSA and its MIMO implementation, we provide for the first time an analysis of the of the convergence speed and frequency offset of the SSA compared to the least mean square (LMS). SSA algorithm can deal with higher frequency offsets and linewidths than LMS, being suitable for optical communications with higher phase noise. SSA does not need pre-compensation of frequency offset, which can be compensated after equalization without penalties. On the other hand, due to reduced convergence speed, SSA requires longer training sequences than LMS

Novel equalization techniques for space division multiplexing based on stokes space update rule

Space division multiplexing (SDM) is a promising technology that aims to overcome the capacity crunch of optical communications. In this paper, we introduce the multiple-input multiple-output (MIMO) Stokes Space Algorithm (SSA) implemented in frequency domain, a novel equalization technique for space division multiplexing (SDM). Although different papers have been published about the SSA and its MIMO implementation, we provide for the first time an analysis of the of the convergence speed and frequency offset of the SSA compared to the least mean square (LMS). SSA algorithm can deal with higher frequency offsets and linewidths than LMS, being suitable for optical communications with higher phase noise. SSA does not need pre-compensation of frequency offset, which can be compensated after equalization without penalties. On the other hand, due to reduced convergence speed, SSA requires longer training sequences than LMS

Frequency-domain 2x2 MIMO equalizer with stokes space updating algorithm

We propose a novel frequency-domain Stokes space algorithm. Its low implementation complexity architecture allows merging static and dynamic 2×2 MIMO equalization in a single stage. We propose a novel frequency-domain Stokes space algorithm. Its low implementation complexity architecture allows merging static and dynamic 2×2 MIMO equalization in a single stage