IQ Skew and Imbalance Estimation for Coherent Point-to-Multi-Point Optical Networks

TL;DR

This paper introduces a novel method using time-and-frequency interleaving tones (TFITs) for estimating IQ skew and power imbalance in coherent point-to-multi-point optical networks, improving performance diagnostics.

Contribution

It proposes a new TFITs-based approach for far-end IQ-impairments estimation in DSCM-based coherent PtMP networks, enabling accurate, simultaneous assessment at individual leaves.

Findings

Experimental verification on 8Gbaud/SC × 4SCs DSCM network

Estimation errors within ±0.5ps for IQ skew and ±0.2dB for power imbalance

Demonstrated potential for improved impairment management in optical networks

Abstract

Coherent point-to-multi-point (PtMP) optical network based on digital subcarrier multiplexing (DSCM) has been a promising technology for metro and access networks to achieve cost savings, low latency, and high flexibility. In-phase and quadrature (IQ) impairments of the coherent transceiver (e.g. IQ skew and power imbalance) cause severe performance degradation. In the DSCM-based coherent PtMP optical networks, it is hard to realize far-end IQ-impairments estimation for the hub transmitter because the leaf on one subcarrier cannot acquire the signal on the symmetrical subcarrier. In this paper, we propose a far-end IQ-impairments estimation based on the specially designed time-and-frequency interleaving tones (TFITs), which can simultaneously estimate IQ skews and power imbalances of the hub transmitter and leaf receiver at an individual leaf. The feasibility of the TFITs-based IQ-impairments estimation has been experimentally verified by setting up $8$Gbaud/SC $\times$ $4$SCs DSCM-based coherent PtMP optical network. The experimental results depict that the absolute errors in the estimated IQ skew and power imbalance are within $\pm 0.5$ps and $\pm 0.2$dB, respectively. In conclusion, TFITs-based IQ-impairments estimation has great potential for DSCM-based coherent PtMP optical networks.