Impact of 1.55 mu m laser diode degradation laws on fibre optic system performances using a system simulator

In this paper, we demonstrate the feasibility of degradation laws introduction in the COMSIS (COmmunication System Interactive Software) telecommunication system simulator. A typical power law thermally activated, experimentally fitted, corresponding to the bias current variation versus time of a 1.55 mum distributed feedback (DFB) single mode laser diode used for digital transmission in metropolitan networks is introduced into COMSIS. Simulations of a typical optical link (50 km, 2.5 Gbits/s) are performed considering a direct current pseudo-random modulation technique for the laser diode (I-th = 20 mA). Bias current variation of the transmitter, corresponding to the worse conditions of extrapolation, clearly shows that the degradation of eye patterns can lead to an indecision between the `0' level and the `1' level after 10 years due to the progressive extinction of the laser diode. The strong interest of such system simulations is presented in order to highlight the impact of component parameters degradation on the whole network performances and check thus the validity of failure criteria in relation with operating conditions. (C) 2003 Published by Elsevier Ltd.