PMD Vector Estimation Through Time-Resolved Waveform Analysis Based on Ultrafast xy-Field Sampling

We show that pulse waveform analysis based on ultrafast xy-field sampling can correctly estimate the complete polarization-mode dispersion (PMD) vector over the signal bandwidth. The xy-field sampling, implemented as polarization-diversity coherent detection with short local pulses, can observe the time-resolved complex amplitude for x- and y-polarizations at ultrafast time scales. By fully characterizing the temporal response of the xy polarized fields after transmission, their Fourier transforms directly yield the output Jones matrix in the frequency domain. Analysis of the matrix provides complete PMD analysis. Consequently, while measuring the waveform distortion of the transmitted pulse train, the technique can quantify a key contributing factor. In addition, a perspective on using this concept to realize rapid PMD estimation is provided. By employing the pulses comprised of two independent state of polarizations (SOPs) as a probe, the two SOP evolutions for individual inputs are captured simultaneously. The analysis algorithm applies the Müller matrix method. This scheme requires neither wavelength sweeping nor input polarization switching, which indicates the possibility of rapid characterization of the Müller matrix and the PMD vector within the probe bandwidth; further study on the measurement range and accuracy is required.

I. Introduction

Pulse distortion caused by polarization-mode dispersion (PMD) is one of the main degradation factors in high-speed fiber-optic communication systems [1], and therefore, an understanding of PMD behavior is an important issue in designing future large capacity transmission systems where adaptive optical/electrical PMD compensation is needed to match the dynamic fluctuations expected [2]–[4].