Compensation of chromatic dispersion and polarization mode dispersion in optical transmission systems

Abstract

Chromatic dispersion and polarization mode dispersion (PMD) are the most relevant disturbances in optical high speed transmission systems. The influence of chromatic dispersion can be overcome by different methods such as dispersion compensating fibers or fiber gratings. Because of its stochastic behavior the struggle against PMD is much more troublesome and essential for bit rates above 10 Gbit/s. The paper describes the influence of polarization mode dispersion derived from basic principles of transmission. It gives some physical understanding and simple derivation of the characteristic equations of PMD. One distinguishes between first and second order PMD. An optical fiber link showing first order PMD only can be modelled by a waveguide with time varying birefringence. If the birefringence additionally is frequency dependent the fiber will show higher order polarization mode dispersion. PMD compensators can be divided in a similar manner: compensators considering first order PMD only and compensators including PMD of higher order. Compensators operating in the optical domain or in the electrical domain have been proposed.