GOALI: Polarization Mode Dispersion Compensation in the Spectral Domain Using Liquid Crystal Modulator Arrays

Purdue University, West Lafayette IN

Investigators

Abstract

High-speed fiber optics plays a key enabling role in today's information technology revolution by providing a means for high bandwidth communications. Commercial optical transmission bandwidths are increasing at an impressive rate. In light of these advances, new effects which were previously considered insignificant are now viewed as key limiting factors in high performance lightwave systems. In order to sustain the growth in bandwidth, new technologies are needed to compensate new transmission impairments that arise with rapidly growing data rates. One such impairment, which has become a key factor limiting transmission rates and distances in high-speed fiber systems, is an effect called polarization-mode dispersion (PMD). PMD arises due to small, spatially varying random birefringences in optical fibers, which lead to decorrelation of the input and output polarization states and pulse spreading in the time domain. The latter effect can cause errors in digital communication systems. This problem is especially acute in the embedded fiber base where many fibers exhibit strong PMD. This proposal describes a university-industry collaborative project which aims to demonstrate a novel and advantageous method for compensation of PMD. The concept is to exploit and extend technology developed in the field of ultrafast optical pulse shaping to compensate PMD of wide-band optical signals in parallel on a wavelength-by-wavelength basis and under computer control. This improves on current approaches that only allow compensation of so-called first order PMD for a single wavelength and which do not apply to situations with wide-band optical signals where the distortion caused by PMD varies substantially across the optical bandwidth. This research project will encompass several aspects. One goal is to perform experiments demonstrating the validity of the proposed new PMD compensation scheme. Research will also target programmable generation of PMD for use in test equipment. Both of these activities will be backed up by numerical simulations. Additionally, new PMD measurement strategies will be devised in order to provide the data necessary to suitably control the proposed wavelength-by-wavelength PMD compensators. This should also result in a major advance in instrumentation for state-of-polarization sensing applicable to multiple-wavelength systems.