Performance evaluation of single-channel coherent systems in presence of nonlinear effects

Performace Evaluation of ASK and DPSK Optical Coherent Systems affected by Chromatic Dispersion and Polarization Mode Dispersion

“…(4) P e0 = l--erfcl where F, = A,(T k ) 2 (i=l, 2), T k is the sampling time for the k-th bit, d the decision threshold, whose optimum value is (5) The error probability is then given by P e = ni (Pr{Q k <0/m,b k =l}) m + 7i 0 (Pr{Q k >0/m,b k =0}} m (6) where Q is the decision variable ( Fig. la) and Pr{B/F} is the probability of the event "B" conditioned by the event "F", b k indicates the k-th bit, m which type of message has been transmitted and π!…”

“…In the case of ASK system we modulate the signal amplitude from 0 to Ρ (Ρ is the transmitted peak power), while in the DPSK system it is the phase of the transmitted signal that is modulated between 0 and π. The modulating function is a raised cosine function with a rise time equal to 1/(4R), where R is the bit rate [4][5]. The output signal EO U , is obtained by (3).…”

“…The method we used is the same as in [4][5], in which system performances were evaluated in presence of Kerr non-linearities. Such a technique is based on the assumption that, in presence of PMD and CD, the signal propagation in optical fibers is a deterministic process and the noise can be assumed present only at the receiver in terms of shot noise.…”

High-speed DPSK coherent systems in the presence of chromatic dispersion and Kerr effect

“…In order to describe the space-time evolution of a linearly polarized field throughout a fiber affected by Kerr effect, chromatic dispersion and loss, it is useful to introduce the complex normalized field amplitude U ( t , z ) , that is given by (4) where E ( t , z ) is the complex envelope of the electrical field at time t in the section z of the fiber and POpt is the transmitted power.…”

“…-l-r----the case of an heterodyne system using asynchronous electrical demodulation affected by chromatic dispersion and Kerr effect is [4], in which however no optimization of the receiver structure is attempted. On the other hand in order to evaluate the feasibility of long span very high-speed systems an accurate design of the receiver is crucial.…”