Large PMD Tolerance Using Block Reversal Alamouti Coding in Simplified Coherent System

We propose and demonstrate a block reversal Alamouti (BR-Alamouti) coding scheme that can effectively tolerate large polarization mode dispersion (PMD) in the single-carrier simplified coherent system with only one single-polarization (SP) heterodyne coherent receiver. If a large PMD exists in the simplified coherent system with traditional Alamouti coding, two orthogonal polarizations experience different time delays so that the time slot orthogonality is destroyed. We theoretically prove that the BR-Alamouti can tolerate large PMD in the simplified coherent system, by time-reversing partial Alamouti-coded data blocks in the time domain to achieve orthogonality in the frequency domain. The performance of the BR-Alamouti is checked in the 20-GBaud QPSK simplified coherent system built on both simulation and experiment platforms. The simulation and experiment results confirm that the BR-Alamouti provides excellent performance and stability to deal with random polarization rotation and large range of differential group delay (DGD) up to 200 ps compared to the traditional Alamouti coding.