Pilot-Aided Joint-Channel Carrier-Phase Estimation in Space-Division Multiplexed Multicore Fiber Transmission

Abstract

The performance of pilot-aided joint-channel carrier-phase estimation (CPE) in space-division multiplexed multicore fiber (MCF) transmission with correlated phase noise is studied. To that end, a system model describing uncoded MCF transmission where the phase noise comprises a common laser phase noise, in addition to core-and polarization-specific phase drifts, is introduced. It is then shown that the system model can be regarded as a special case of a multidimensional randomwalk phase-noise model. A pilot-aided CPE algorithm developed for this model is used to evaluate two strategies, namely jointchannel and per-channel CPE. To quantify the performance differences between the two strategies, their respective phasenoise tolerances are assessed through Monte Carlo simulations of uncoded transmission for different modulation formats, pilot overheads, laser linewidths, numbers of spatial channels, and degrees of phase-noise correlation across the channels. For 20 GBd transmission with 200 kHz combined laser linewidth and 1% pilot overhead, joint-channel CPE yields up to 3.4 dB improvement in power efficiency or 25.5% increased information rate. Moreover, through MCF transmission experiments, the system model is validated and the strategies are compared in terms of bit-error-rate performance versus transmission distance for uncoded transmission of different modulation formats. Up to 21% increase in transmission reach is observed for 1% pilot overhead through the use of joint-channel CPE.

Iterative Detection and Phase-Noise Compensation for Coded Multichannel Optical Transmission

“…To assess the efficacy of the system model in (1) and the proposed algorithms, a recirculating-loop experiment involving SDM transmission of 64QAM at 20 GBaud through 3 cores of a 7-core weakly-coupled, homogeneous, multicore fiber was carried out. The experimental setup and detailed results are given in a separate article [44]. In this section, additional results are presented based on the same data set.…”

Optimization of Transmitter-Side Signal Rotations in the Presence of Laser Phase Noise

“…The considered system model is based on a simple multichannel laser-phase-noise model proposed in [30], which was used to assess potential performance gains that come from estimating laser phase noise jointly over multiple channels. The model-based simulation results were found to be in agreement with experimental results for transmission through a weakly-coupled, single-mode, homogeneous MCF.…”

“…The model-based simulation results were found to be in agreement with experimental results for transmission through a weakly-coupled, single-mode, homogeneous MCF. The system model in [30] entails uncoded dual-polarization transmission over multiple channels in the presence of laser phase noise, which is arbitrarily correlated among the channels. The data symbols are modeled as uniform random variables that take on values from a set X of complex constellation points, and normalized such that the average symbol energy is E s per channel.…”

On the Performance of Joint-Core Carrier-Phase Estimation in the Presence of Intercore Skew

“…The time-varying nature of phase noise demands dynamic tracking, referred to here as carrier-phase estimation (CPE), which nowadays is typically carried out using digital signal processing (DSP) algorithms operating with the help of pilots [1], [2] or in a blind fashion without the use of pilots [3], [4]. CPE has in recent years been studied specifically in the context of multichannel fiber-optic systems [2], [5]- [8], such as in space-division multiplexed (SDM) transmission. SDM is believed to have the potential to upscale future optical networks in a cost-efficient way through, e.g., the integration of hardware and other resources, as well as the use of specific fibers such as multicore fibers (MCFs) and multimode fibers [9].…”

“…In [14], an algorithm for joint-polarization CPE was proposed, where due to the high degree of correlation in the phase noise in both polarizations, significant performance gains were achieved over per-channel processing. Furthermore, in [2], [15], algorithms performing CPE jointly on an arbitrary number of channels were proposed and found effective based on experimental verification involving MCF transmission [5] and frequency-comb-based wavelength-division multiplexed (WDM) transmission [2].…”