Modified widely linear filter for simultaneous multi-impairment compensation
We present a modified w idely l inear s ingle-tap b lind e qualizer f or t he joint multi-impairment compensation of polarization mixing, IQ Imbalance and transceiver phase noise, analyze its performance through simulation and experiments for 32Gbaud PM-16QAM transmission.
Geometric Parameter Extraction-based Receiver IQ imbalance correction for MQAM systems
We present a modulation transparent geometric parameter extraction method to compensate for the receiver IQ imbalance. We evaluate the algorithm's performance for various imbalance values for 32-GBd 16/64QAM signals in both simulations and through experiments.
Pilot-free Bayesian Filter for Phase Noise Correction of 64QAM CO-OFDM Superchannel
We experimentally demonstrate the use of a pilot-free phase noise mitigation algorithm for a gain-switched comb-based 480 Gbps 64QAM CO-OFDM superchannel system using weighted-blind estimation and Bayesian filter with 18% potential improvement in spectral efficiency.
Improved timing synchronization for long-haul transmission at 100 Gbps over 80 WDM channels
We experimentally demonstrate 80 × 100 Gbit/s coherent PDM-QPSK transmission of WDM channels spaced 50 GHz apart, over 1840 Km of Sterlite OH-LITE G652.D fiber using Kalman filtering of timing error estimates obtained from the Oerder & Meyer algorithm.
Pilot-free common phase error estimation for CO-OFDM with improved spectral efficiency
We propose an improved pilot free phase noise mitigation algorithm for CO-OFDM systems using weighted multi-level QPSK partitioning and Kalman filtering. Through extensive Monte Carlo simulations, we demonstrate an improvement in spectral efficiency of >6% in case of 200 Gbps single channel and 1 Tbps multi channel 16QAM CO-OFDM transmission with blind carrier phase estimation. We also experimentally demonstrate the performance of the proposed algorithm against the standard pilot aided algorithm for the transmission of 120 Gbps 16QAM CO-OFDM at different noise levels.
Adaptive Referencing Multitap Filter for TX-IQ Imbalance and Residual ISI Tolerance
We present a multi-tap filter for residual intersymbol interference correction which is tolerant to the transmitter IQ imbalance by adapting the reference constellation simultaneously. We evaluate the algorithm's performance for various imbalance values for 32-GBd 16QAM signals through experiments.
OFDM Baud Rate Limitations in an Optical Heterodyne Analog Fronthaul Link using Unlocked Fibre Lasers
The phase noise (PN) of a photo-generated mmwave carrier, resulting from frequency and phase fluctuations of uncorrelated laser sources, limits the performance of heterodyne/millimeter-wave analog radio-over-fibre links. This work analyzes the effect of subcarrier baud rate and frequency offset (FO) variations on the performance of a 60 GHz OFDM signal generated using unlocked fiber lasers. Conventional digital techniques for FO and PN compensation, in a 25 km mm-wave A-RoF heterodyne system, are shown to overcome relatively large FOs and to enable the successful transmission of kHz range sub-carrier baud rates-in line with recent 5G recommendations.
Optical Phase Conjugation Using Nonlinear SOA for Nonlinearity and Dispersion Compensation of Coherent Multi-Carrier Lightwave Systems
We study the use of nonlinear semiconductor optical amplifier (SOA) for generating optical phase conjugate towards compensation of distortions in short distance optical fiber transmission due to Kerr nonlinearity and chromatic dispersion in coherent multi-carrier lightwave signals. We experimentally demonstrate the effectiveness of the SOA-based phase conjugator to improve the link budget with a 100 km standard single mode fiber link for 20 GHz coherent OFDM signals, with QPSK and 16QAM modulations and a corresponding net bit-rate of 40 Gbps and 80 Gbps respectively. Mid-span spectral inversion scheme is employed where the optical phase conjugate is generated through a partially degenerate four-wave mixing process in a nonlinear SOA. We demonstrate a bit error rate performance within $2\times 10^{-2}$ for an average launched power of up to 12 dBm (9 dBm) for QPSK (16QAM) coherent OFDM signals, in a 100 km fiber link. We also investigate the possible improvement in link budget using numerical simulation for 16QAM and 64QAM CO-OFDM signals with the proposed scheme.
Performance characterization of digital power division multiplexed transmission in fundamental mode of few-mode fiber
We experimentally demonstrate 25.33 Gbps digital power division multiplexed DD-OFDM transmission in 6.5 GHz bandwidth through 5.3 km few mode fiber to enable higher split-ratio and better spectral efficiency in short-haul links.
Influence of Polarization Transformation in Phase Conjugation of PM-QPSK in Nonlinear SOAs
Polarization insensitive phase conjugation generation is experimentally demonstrated using a single pump in a nonlinear SOA for 10 GBaud PM-QPSK data. The influence of polarization transformation properties specific to signal-pump detuning conditions are established.