10-Gb/s PMD compensation using ferroelectric liquid crystals and several PMD penalty signals

ABSTRACTPolarization mode dispersion (PMID) hampers development of 1O Gb/s trunk lines but can be compensated byendless polarization controllers and birefringent fiber. We demonstrate automatic 10 Gb/s PMD compensationusing three deformed-helix ferroelectric liquid crystal cells.KEYWORDSPolarization mode dispersion, Deformed-Helical Ferroelectric Liquid Crystals, Penalty Signal Generation,TDM systems 1. INTRODUCTIONPolarization mode dispersion (PMD) hampers the development of highest-capacity, long-haul optical communi-cation systems. Especially in upgrading of existing transmission lines to 1O Gb/s data rates high PMD of 'old'fibers is a serious problem. Recent publications have shown ways how to compensate PMD [1, 21. A key topractical compensation are low-cost endless polarization controllers. Fiber squeezers [31 are too bulky, LiNbO3 [3, 4] needs several 10 V driving voltage, and nematic liquid crystals are too slow [5]. However, deformed-helicalferroelectric liquid crystals (DHF) [6] respond in a few 100 p.s and need V. We describe the theoreticalfunction of such a controller and demonstrate automatic, though not yet endless, PMD compensation at 10 Gb/s.Horizontal input polarization 'H' can be transformed