Abstract
The capacity of space division multiplexing (SDM) systems with coupled channels is fundamentally limited by mode-dependent loss (MDL) and mode-dependent gain (MDG) generated in components and amplifiers. In these systems, MDL/MDG must be accurately estimated for performance analysis and troubleshooting. Most recent demonstrations of SDM with coupled channels perform MDL/MDG estimation by digital signal processing (DSP) techniques based on the coefficients of multiple-input multiple-output (MIMO) adaptive equalizers. Although these methods provide a valid indication of the order of magnitude of the accumulated MDL/MDG over the link, MIMO equalizers are usually updated according to the minimum mean square error (MMSE) criterion, which is known to depend on the channel signal-to-noise ratio (SNR). Therefore, MDL/MDG estimation techniques based on the adaptive filter coefficients are also impaired by noise. In this paper, we model analytically the influence of the SNR on DSP-based MDL/MDG estimation, and show that the technique is prone to errors. Based on the transfer function of MIMO MMSE equalizers, and assuming a known SNR, we calculate a correction factor that improves the estimation process in moderate levels of MDL/MDG and SNR. The correction factor is validated by simulation of a 6-mode long-haul transmission link, and experimentally using a 3-mode transmission link. The results confirm the limitations of the standard estimation method in scenarios of high additive noise and MDL/MDG, and indicate the correction factor as a possible solution in practical SDM scenarios.
Original language | English |
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Article number | 9291436 |
Pages (from-to) | 1968-1975 |
Number of pages | 8 |
Journal | Journal of Lightwave Technology |
Volume | 39 |
Issue number | 7 |
Early online date | 11 Dec 2020 |
DOIs | |
Publication status | Published - 1 Apr 2021 |
Keywords
- mode-dependent gain
- Mode-dependent loss
- optical fiber communications
- space division multiplexing
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High Capacity Optical Transmission Lab
Chigo Okonkwo (Manager), Sjoerd van der Heide (Operator), Menno van den Hout (Operator), Sebastiaan Goossens (Operator), John J.A. van Weerdenburg (Operator), Vincent van Vliet (Operator), Tom Bradley (Manager), Aaron Albores-Mejia (Manager), Denis Fatkhiev (Operator), Maria Freire Hermelo (Operator) & Kadir Gümüş (Operator)
Electrical EngineeringFacility/equipment: Research lab