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The paper describes the procedures and preliminary results of accelerated life tests performed in the frame of an evaluation programme under ESA -contract. For the calculation of activation energy and median life time, and in order to investigate the drift behaviour ofoptical parameters, a conventional three temperature ageing test at 30°C, 50°C and 70°C is being performed on 80 laser diodes in total, split into two subgroups operating under quaternary pulse position modulation (QPPM) and non return to zero (NRZ) modulation at l6Mbitis with a PN-code length 2-1. The hermetically sealed diodes of the three selected laser types are operated for 3500hrs under automatic average power control with lO4mWpeak/3OmWaverage for QPPM and SlmWpeak/42mWaverage power for NRZ. The failure criterion is 30%-increase ofthe bias current, continuously monitored by computer. Intermediate measurements of the lasers PJI-curves, V/I-characteristics, far field patterns and spectra for purpose of s-calculation are performed. leasurements before and upon completion of the ageing tests consist of Pa/I-curves, V/I-characteristics, photo diode tracking ratios, spectra, mode hopping behaviours, far field patterns, wave front errors and astigmatisms and linear polarization ratios.

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