Transceiver Noise Characterization based on Perturbations

TL;DR

This paper introduces a novel frequency domain notch technique for measuring transceiver noise, skew, and impairments, enabling accurate SNDR estimation and impairment detection with minimal signal processing.

Contribution

The paper presents a new method using frequency domain notches to measure and compensate transceiver impairments, demonstrated on commercial transceivers and DACs.

Findings

Notches can mitigate crosstalk effects on SNDR estimates.

Single notch spectra can detect and compensate impairments.

Skew estimation is feasible using the proposed method.

Abstract

In this paper, we discuss a new technique for measuring transceiver noise, skew, and for the detection of uncompensated transceiver impairments. The method consists on the introduction of frequency domain notch or notches at the transmitter, which allows to estimate of the Signal-to-Noise and Distortion Ratio (SNDR) at different stages over the transmission chain. The proposed technique requires the detection of the signal spectrum using either: a modem receiver, an Optical Spectrum Analyzer (OSA), an oscilloscope, or an Electrical Spectrum Analyzer (ESA), depending on the stage where the spectrum is measured and requiring minimal processing of the received signal. Our analysis is focused on Ciena's WaveLogic Ai commercial transceiver and a 95 Gbaud DAC. We demonstrate that symmetrically placed frequency domain notches can be used to mitiguate the influence of crosstalk on the SNDR estimates. Finally, we show how a single notch spectrum can be used to detect and compensate for impairments, and we perform skew estimation as an example.