Abstract

Progress in the development of long haul transmission systems using erbium doped fiber amplifiers as repeaters has been very rapid, and the installation of this kind of system in undersea applications is imminent [1,2]. It is very important to understand all aspects of the optical propagation in an optically amplified link, because the noise due to the amplifiers' ASE and any distortions resulting from non-linear effects etc. accumulate through the whole length of the system. This paper reports a study into the effects of polarisation dependent loss (PDL) on the signal and ASE levels in a 3100 km amplified system, containing 69 amplified sections with 45 km repeater spacing [2]. It is known that small amounts of PDL at each section can concatenate to give a significant and variable overall PDL, which leads to fading in the signal to noise ratio [3]. We will show that there is also a previously unnoticed polarisation dependent effect which causes a net penalty in the signal to noise ratio, and we will describe how to eliminate it.

© 1993 Optical Society of America