Zifeng Wu

Coherent UDWDM PON with joint subcarrier reception at OLT

In this contribution, we report on the experimental investigation of an ultra-dense wavelength-division multiplexing (UDWDM) upstream link with up to 700 × 2.488 Gb/s polarization-division multiplexing differential quadrature phase-shift keying parallel upstream user channels transmitted over 80 km of standard single-mode fiber. We discuss challenges of the digital signal processing in the optical line terminal arising from the joint reception of several upstream user channels. We present solutions for resource and cost-efficient realization of the required channel separation, matched filtering, down-conversion and decimation as well as realization of the clock recovery and polarization demultiplexing for each individual channel.

Clock Recovery by Fractionally Spaced Equalizers for Parallelized Receivers in Optical Networks

A fractionally spaced equalizer (FSE) can perform timing phase adjustment. This paper explains how FSEs can also achieve clock frequency offset compensation. The proposed architecture is suitable for parallelized high speed receivers.

Modulation-Format-Transparent Polarization Tracking Using a Neural Network

We propose a novel technique for modulation-format-transparent polarization tracking and demultiplexing in a coherent, polarization multiplexed fiber-optic communication system. The technique employs Stokes space analysis of the received signal, which allows us to uniquely identify the polarization state independently of the modulation format. A neural network is used for acquisition and tracking of the polarization state and the obtained information is subsequently used to update an adaptive filter that performs the actual demultiplexing.