Abstract

Recent investigations regarding long-haul high-speed transmission systems using Er-doped fiber amplifier repeaters have shown a possibility of realizing the systems of up to 10000 km transmission distance [1][2]. In these system, accumulated polarization dependencies, such as polarization mode dispersion (PMD) and polarization depending loss (PDL) in the fiber and EDFAs, induce a fading in bit error rate (BER) characteristic [3]-[5]. Polarization mode dispersion induces inter-symbol-interference (ISI) in IM-DD systems according to input polarization states because of propagation delay time between the two orthogonal eigen modes (principal states). This influence becomes a serious problem by increasing the bit rate or the transmission length. To avoid polarization mode dispersion influence, the authors have been proposed a "principal states transmission method [6]", which launches the signal light at one of principal states. However, the formerly proposed method can not be applied to optical repeater systems, which include optical isolators, because a pilot light is required to transmit in the opposite direction of the signal light in the same fiber.

© 1993 Optical Society of America