Optically preamplified systems: defining a new eye aperture

Summary form only given. In optical systems having relatively low bit-rate/spl times/distance products (e.g., 2.5 Gbit/s/spl times/100 km) the major problem is to have sufficient power budgets and optical signal-to-noise ratios (SNR). With the increase of the distance-bit-rate product, another important problem appears: the degradation due to intersymbol interference (ISI) stemming from dispersions or nonlinearities. Therefore, the bit error rate (BER) after propagation results from both SNR and ISI degradation. In order to fully understand the system behavior, it is required to separate the different contributions to BER degradation. In optically preamplified systems, however, the usual definition of the eye aperture is inadequate. In this paper, we define a new parameter Q and experimentally verify its relevance.