Data-aided single-carrier coherent receivers

Data-aided algorithms for coherent optic receivers are discussed as an extension of existing non-data aided methods. The concept presents a scalable approach with low implementation complexity and limited overhead for higher-order modulation formats

Optical performance monitoring from FIR filter coefficients in coherent receivers

Abstract: We present a robust and precise optical performance monitoring technique from FIR filter coefficients in coherent receivers with digital equalization. Residual chromatic dispersion, DGD and OSNR are simultaneously estimated from measured 111 Gbit/s data

Impact of mechanical vibrations on laser stability and carrier phase estimation in coherent receivers

Coherent communication systems are largely limited by the laser linewidth of the local oscillator. In addition to phase noise, large frequency deviations can occur if the laser is mechanically vibrated. The detrimental effect of the frequency instability is measured for coherent optical receivers on a typical laser and numerically analyzed for quadrature phase-shift keying and 16-quadrature amplitude modulation using common feed-forward carrier phase recovery algorithms

DSP for coherent single-carrier receivers

In this paper, we outline the design of signal processing (DSP) algorithms with blind estimation for 100-G coherent optical polarization-diversity receivers in single-carrier systems. As main degrading optical propagation effects, we considered chromatic dispersion (CD), polarization-mode dispersion (PMD), polarization-dependent loss (PDL), and cross-phase modulation (XPM). In the context of this work, we developed algorithms to increase the robustness of the single DSP receiver modules against the aforesaid propagation effects. In particular, we first present a new and fast algorithm to perform blind adaptive CD compensation through frequency-domain equalization. This low complexity equalizer component inherits a highly precise estimation of residual dispersion independent from previous or subsequent blocks. Next, we introduce an original dispersion-tolerant timing recovery and illustrate the derivation of blind polarization demultiplexing, capable to operate also in condition of high PDL. At last, we propose an XPM-mitigating carrier phase recovery as an extension of the standard Viterbi-Viterbi algorithm

Data-aided vs. blind single-carrier coherent receivers

Blind and data-aided single-carrier receivers are discussed for high-speed optical coherent receivers. Equalization concepts are presented and evaluated regarding the implementation complexity and overhead for time-domain and frequency-domain equalization techniques

Polarization coupled carrier phase estimation for coherent polarization multiplexed QPSK with OOK-neighbours

We proposed a novel algorithm for carrier phase estimation with differential demodulation, phase coupling between both polarizations and non-redundant error correction. The algorithm is demonstrated on measured 111 Gb/s polarization-multiplexed QPSK with 10times10.7 Gb/s OOK neighbour

Data-aided single-carrier coherent receivers

Data-aided algorithms for coherent optic receivers are discussed as an extension of existing non-data aided methods. The concept presents a scalable approach with low implementation complexity and limited overhead for higher-order modulation formats

Polarization coupled carrier phase estimation for coherent polarization multiplexed QPSK with OOK-neighbours

We proposed a novel algorithm for carrier phase estimation with differential demodulation, phase coupling between both polarizations and non-redundant error correction. The algorithm is demonstrated on measured 111 Gb/s polarization-multiplexed QPSK with 10times10.7 Gb/s OOK neighbour

Low complexity soft differential decoding of QPSK for forward in coherent optic receivers

Coherent systems based on QPSK rely on differential encoding to avoid catastrophic error propagation. A simple solution for soft differential decoding is presented that limits the penalty after FEC to 0.75dB, similar to pre-FEC binary differential decoding